Environment-friendly lightweight porous concrete slab and preparation method thereof

Abstract

The application discloses an environment-friendly light-weight porous concrete slab in the field of concrete and a preparation method thereof, and comprises the following components in parts by weight: cement, pulverized coal, recycled aggregate, light aggregate, modified fiber, water reducing agent 0.6-1.2 parts, carbonation-resistant additive, pore-forming agent and foam stabilizer. The application realizes the comprehensive performance of the concrete slab, such as light weight, high strength, high toughness and environmental protection, through interface optimization and functionalization of the modified fiber, efficient utilization of solid waste resources, precise raw material pretreatment and process control. The modified fiber solves the pain points of traditional polypropylene fiber and cement-based matrix, such as weak interface combination and easy agglomeration, through multi-step chemical modification, and is the key to improving the strength and toughness. The large application of pulverized coal ash and waste concrete recycled aggregate realizes the synergy of environmental protection and performance. The phased mixing and precise curing guarantee the material uniformity and hydration sufficiency.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of concrete, and particularly relates to an environment-friendly light-weight porous concrete slab and a preparation method thereof. BACKGROUND

[0002] As the most widely used basic material in the field of construction, the annual output of concrete accounts for more than 60% of the total output of artificial building materials in the world. Although the traditional dense concrete slab has certain mechanical properties, it has significant limitations in resource consumption, energy consumption and environmental impact, and has been difficult to adapt to the development needs of contemporary green buildings. From the perspective of resources and energy, the traditional concrete slab takes cement as the core cementitious material, and the production process of cement consumes a large amount of non-renewable resources such as limestone and clay. Moreover, the production of 1 ton of cement emits about 0.8-1.0 tons of carbon dioxide, accounting for 8%-10% of the total global industrial carbon emissions, which is one of the important factors leading to the greenhouse effect. At the same time, the traditional concrete slab has high density and large self-weight, which not only increases the load bearing of the building structure, resulting in the need to invest more auxiliary materials such as steel and formwork during the construction stage, but also increases fuel consumption and carbon emissions during transportation, forming a high-energy consumption chain throughout the production-construction-use cycle. In terms of performance, the traditional concrete slab has high thermal conductivity and poor thermal insulation performance. According to the building energy consumption monitoring data, the building using the traditional concrete slab has high heat loss of the envelope structure, and needs to rely on air conditioning, heating and other equipment to make up for the energy consumption gap, further aggravating energy waste. In addition, the traditional concrete slab has poor crack resistance and is prone to cracking under the action of environmental factors such as dry-wet cycle and temperature change, which leads to rainwater penetration and steel corrosion, shortens the service life of the building, and increases the maintenance cost and resource consumption in the later period.

[0003] To solve the problems of the traditional concrete slab, light-weight porous concrete slab has gradually become a research hotspot in the industry. The light-weight concrete slab has undergone multiple generations of technical iteration, and the core idea is to build a porous structure inside the concrete to achieve the dual goals of weight reduction and thermal insulation, thereby significantly reducing the density and thermal conductivity and achieving a breakthrough in reducing the self-weight of the building and improving the thermal insulation performance. However, the existing light-weight porous concrete slab still has multi-dimensional technical defects: although the porous structure can achieve light weight, the increase in porosity often leads to a decrease in strength, which is difficult to meet the requirements of mechanical properties of load-bearing partition walls and low-rise building slabs. If the porosity is reduced to improve the strength, the advantages of light weight and thermal insulation will be lost, and a performance contradiction will be caused. The existing products mostly use chemical foaming agents to prepare pores, and the residues of some chemicals may cause the slab to return to alkali and crack in the later period, and the production process of the foaming agent has certain pollution. SUMMARY

[0004] In view of the above, in order to overcome the defects of the prior art, the present application provides an environmentally friendly lightweight porous concrete slab and a preparation method thereof. The present application realizes the comprehensive performance of "light weight, high strength, high toughness and environmental protection" of the concrete slab through interface optimization and functionalization of modified fibers, efficient utilization of solid waste resources, precise raw material pretreatment and process control. The modified fibers solve the pain points of "weak interface bonding and easy agglomeration" of traditional polypropylene fibers and cement-based matrix through multi-step chemical modification, which is the key to improving strength and toughness. The large-scale application of fly ash and waste concrete recycled aggregate realizes the synergy of environmental protection and performance. The staged mixing and precise curing ensure the uniformity and hydration of the material.

[0005] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: the present application provides an environmentally friendly lightweight porous concrete slab, which comprises the following components by weight:

[0006] cement 30-40 parts, fly ash 20-30 parts, recycled aggregate 5-15 parts, lightweight aggregate 15-30 parts, modified fiber 0.5-1 part, water reducing agent 0.6-1.2 parts, carbonation-resistant additive 0.6-1.2 parts, pore-forming agent 0.8-1.5 parts, foam stabilizer 0.3-0.5 parts;

[0007] Preferably, the recycled aggregate includes at least one of waste concrete recycled aggregate, waste ceramic recycled aggregate, waste brick recycled aggregate, and industrial tailings recycled aggregate;

[0008] Preferably, the lightweight aggregate includes at least one of pumice, volcanic slag, expanded perlite, coal gangue ceramic, and expanded slag beads;

[0009] Preferably, the water reducing agent includes at least one of polycarboxylic acid type water reducing agent, naphthalene type water reducing agent, and carbonyl pyruvic aldehyde water reducing agent;

[0010] Preferably, the carbonation-resistant additive includes at least one of silane coupling agent KH-560 and silane coupling agent KH-550;

[0011] Preferably, the preparation method of the modified fiber specifically includes the following steps:

[0012] A1, dissolve an enol compound in dry toluene, add a hydroxyl protecting agent, mix uniformly, then pass through flowing nitrogen, transfer to an ice water bath, and perform a hydroxyl shielding reaction to obtain an enol protected monomer solution;

[0013] Preferably, in step A1, the enol compound includes at least one of 4-penten-1-ol, 5-hexen-1-ol, 6-hepten-1-ol, 9-decen-1-ol, 10-undecen-1-ol, and cis-5-octen-1-ol;

[0014] Preferably, in step A1, the hydroxyl protecting agent comprises at least one of trimethylaluminum, triethylaluminum, triisobutylaluminum;

[0015] Preferably, in step A1, the mass ratio between the enol compound and the hydroxyl protecting agent is 1-2:1.2-3;

[0016] Preferably, in step A1, the stirring speed of the hydroxyl shielding reaction is 200-300 rpm, and the reaction time of the hydroxyl shielding reaction is 3-4 h;

[0017] A2, take the homopolymerization polypropylene powder, the enol protected monomer solution prepared in step A1, dicumyl peroxide and anhydrous toluene, add them into a high-speed mixer under a nitrogen atmosphere, and stir at room temperature. After the reaction system is uniformly mixed, transfer it to a twin-screw extruder for melt grafting reaction. The melt is extruded through a die head, granulated, and modified polypropylene particles are obtained;

[0018] Preferably, in step A2, the weight ratio of the homopolymerization polypropylene powder, the enol protected monomer solution prepared in step A1, the initiator and the anhydrous toluene is as follows: homopolymerization polypropylene powder 100 parts, enol protected monomer solution prepared in step A1 30-50 parts, dicumyl peroxide 0.5-0.8 parts, and anhydrous toluene 5-10 parts;

[0019] Preferably, in step A2, the temperature parameters of the melt grafting reaction are set as follows: feeding section: 135-145℃; compression section: 145-155℃; melt reaction section: 162-168℃; homogenization section: 168-172℃; die head: 162-168℃;

[0020] Preferably, in step A2, the screw rotation speed of the melt grafting reaction is 85-115 rpm;

[0021] A3, melt spinning the modified polypropylene particles prepared in step A2, placing them in an aqueous hydrochloric acid solution, increasing the reaction temperature for stirring reaction, filtering, collecting the fibers, washing them with deionized water until neutral, then placing them in an EDTA solution for immersion, filtering, collecting the fibers, washing them with deionized water, and vacuum drying to obtain modified polypropylene fibers;

[0022] Preferably, in step A3, the concentration of the aqueous hydrochloric acid solution is 0.2-0.5 mol / L;

[0023] Preferably, in step A3, the stirring reaction temperature is 30-40℃, and the stirring reaction time is 1-2 h;

[0024] A4, the modified polypropylene fiber prepared in step A3 is soaked in an ammonia water solution, taken out, washed with deionized water until neutral, and then added to a dopamine-Tris solution, and stirred and reacted at room temperature for 2-3 h. After the reaction is completed, the fiber is collected by filtration, washed with deionized water, and vacuum dried to obtain a PDA-modified polypropylene fiber;

[0025] Preferably, in step A4, the mass of dopamine added is 6%-12% of the mass of the modified polypropylene fiber;

[0026] A5, the PDA-modified polypropylene fiber prepared in step A4 is added to a copper nitrate aqueous solution, the pH of the reaction system is adjusted to 5.0-5.5, and then an ammonium oxalate aqueous solution is added dropwise after uniform mixing, and the reaction temperature is increased for deposition. After the reaction is completed, the fiber is collected by filtration, washed with deionized water until neutral, and vacuum dried to obtain a modified fiber;

[0027] Preferably, in step A5, the mass concentration of the copper nitrate aqueous solution is 0.15-0.3 mol / L, and the mass concentration of the ammonium oxalate aqueous solution is 0.15-0.3 mol / L;

[0028] Preferably, in step A5, the mass-to-volume ratio of the PDA-modified polypropylene fiber to the copper nitrate aqueous solution is 0.1-0.25 g / mL;

[0029] Preferably, in step A5, the mass-to-volume ratio of the PDA-modified polypropylene fiber to the ammonium oxalate aqueous solution is 0.1-0.25 g / mL;

[0030] Preferably, the preparation method of the pore-forming agent specifically comprises the following steps:

[0031] B1, 3-aminophenol hydrochloride is dissolved in deionized water, sodium bicarbonate is added, stirring is continued until no bubbles are generated, and then vacuum filtration is performed. The solid is collected, washed, and vacuum dried to obtain 3-aminophenol;

[0032] Preferably, in step B1, the mass ratio between the 3-aminophenol hydrochloride and the sodium bicarbonate is 1.4-1.7:1;

[0033] Preferably, in step B1, the mass concentration of the 3-aminophenol hydrochloride in the deionized water is 0.14-0.17 g / mL;

[0034] B2, resorcinol is dissolved in anhydrous toluene, p-toluenesulfonic acid is added, after mixing uniformly, 3-aminophenol prepared in step B1 is added, and a uniform reaction system is obtained by mixing, the reaction temperature is increased to carry out reflux reaction, after the reaction is completed, cooling is carried out, ice water is added to the reaction system, stirring is carried out until the solid is completely precipitated, vacuum filtration is carried out, the solid is collected, washing, purification, vacuum drying, 3, 3'-dihydroxydiphenylamine is obtained;

[0035] Preferably, in step B2, the mass ratio between the resorcinol and the 3-aminophenol is 1.0-1.2:1;

[0036] Preferably, in step B2, the added mass of the p-toluenesulfonic acid is 15%-16% of the mass of the resorcinol;

[0037] Preferably, in step B2, the reaction temperature of the reflux reaction is 120-130℃, and the reaction time of the reflux reaction is 4-6h;

[0038] B3, 3, 3'-dihydroxydiphenylamine prepared in step B2 is dissolved in acetone, anhydrous K2CO3 is added, after mixing uniformly, brominated long-chain alkane is added dropwise, after the dropwise addition is completed, the reaction temperature is increased to carry out reflux reaction, after the reaction is completed, heating is stopped, cooling is carried out, filtration is carried out, the filtrate is collected, excess solvent is removed by reduced pressure distillation, after purification, long-chain modified 3, 3'-dihydroxydiphenylamine is obtained;

[0039] Preferably, in step B3, the mass-volume ratio between the 3, 3'-dihydroxydiphenylamine and the brominated long-chain alkane is 0.78-0.96g / mL; wherein the brominated long-chain alkane includes at least one of 1-bromooctane, 1-bromononane, 1-bromodecane;

[0040] Preferably, in step B3, the mass ratio between the 3, 3'-dihydroxydiphenylamine and the anhydrous K2CO3 is 7-8.5:9.7-11.6;

[0041] Preferably, in step B3, the reaction temperature of the reflux reaction is 50-60℃, and the reaction time of the reflux reaction is 4-6h;

[0042] B4, long-chain modified 3, 3'-dihydroxydiphenylamine prepared in step B3 is dissolved in anhydrous DMF, anhydrous K2CO3 is added, after mixing uniformly, flow nitrogen is introduced into the reaction system, Br-PEG-OH is dissolved in DMF, and is added dropwise into the reaction system, after the dropwise addition is completed, the reaction temperature is increased to carry out substitution reaction, after the reaction is completed, cooling is carried out, vacuum filtration is carried out, the filtrate is collected, rotary evaporation is carried out, anhydrous diethyl ether is added for sedimentation purification, vacuum filtration is carried out, the precipitate is collected, washing, drying, PEG modified intermediate is obtained;

[0043] Preferably, in step B4, the mass ratio between the long-chain modified 3,3'-dihydroxydiphenylamine and Br-PEG-OH is 1.0-1.5:1.8-2.5;

[0044] Preferably, in step B4, the mass ratio between the long-chain modified 3,3'-dihydroxydiphenylamine and K2CO3 is 1.0-1.5:1.8-3.0;

[0045] Preferably, in step B4, the reaction temperature of the substitution reaction is 70-80°C, and the reaction time of the substitution reaction is 5-6h;

[0046] B5, the PEG modified intermediate prepared in step B4 is dissolved in anhydrous toluene, p-toluenesulfonic acid is added, after uniform mixing, maleic anhydride is added, stirring to form a uniform system, after flowing nitrogen is introduced, the reaction temperature is increased to carry out reflux reaction, after the reaction is completed, cooling, saturated sodium bicarbonate aqueous solution is added for repeated washing, the organic phase is collected, after washing with deionized water, the organic phase is dehydrated with anhydrous sodium sulfate, the filtrate is collected by vacuum filtration, concentrated by rotary evaporation, and the esterification intermediate product is obtained after purification;

[0047] Preferably, in step B5, the added mass of p-toluenesulfonic acid is 2.5%-3.0% of the mass of the PEG modified intermediate;

[0048] Preferably, in step B5, the mass ratio between the PEG modified intermediate and maleic anhydride is 1.75-2.5:0.6-0.8g;

[0049] Preferably, in step B5, the reaction temperature of the reflux reaction is 80-90°C, and the reaction time of the reflux reaction is 4-6h;

[0050] B6, sodium bisulfite is dissolved in an ethanol aqueous solution, the esterification intermediate product prepared in step B5 is added, the reaction temperature is increased to carry out sulfonation reaction, after the reaction is completed, cooling, dialysis is carried out with deionized water to remove unreacted SO3 - , reduced pressure concentration, freeze-drying to obtain a pore-forming agent;

[0051] Preferably, in step B6, the mass ratio between the sodium bisulfite and the esterification intermediate product is 0.65-0.85:1.7-2.5;

[0052] Preferably, in step B6, the reaction temperature of the sulfonation reaction is 65-75°C, and the reaction time of the sulfonation reaction is 3-4h;

[0053] The present application also provides a preparation method of an environmentally friendly lightweight porous concrete slab, which specifically comprises the following steps:

[0054] S1: raw material pretreatment:

[0055] S11, fly ash treatment: put the fly ash into a drying oven at 100-110°C, dry until the water content is ≤1%; then pass through an 80-mesh standard sieve to remove coarse particles and unburned carbon particles, obtain pretreated fly ash, and reserve;

[0056] S12, recycled aggregate treatment: take the waste aggregate, crush it with a jaw crusher, then sieve it with a 5-10mm aperture sieve, repeatedly rinse it with clean water until the surface is free of floating dust, and dry it under ventilation until the water content is 3-5%, and reserve;

[0057] S13, lightweight aggregate treatment: select lightweight aggregate, soak it for 2h, then drain it until the surface is free of water, and reserve;

[0058] S14, modified fiber pretreatment: cut the modified fiber into 6-12mm short fibers, dry mix it with the pretreated fly ash prepared in step S11 for 1min to achieve fiber pre-dispersion, obtain pre-dispersed modified fiber, and reserve;

[0059] S15, dilute the water-reducing agent with mixing water to obtain a 10-15% water solution, and reserve the water-reducing agent dilution;

[0060] S16: take water according to the water-cement ratio (water / cement + fly ash) of 0.4-0.45, of which 10-15% is used to dilute the water-reducing agent, and the rest is direct mixing water;

[0061] S2, mixing and stirring in stages:

[0062] S21, put the cement and pre-dispersed modified fiber into the mixer, stir at a speed of 150-200r / min for 1-2min until the fiber is evenly distributed;

[0063] S22, slowly add the water-reducing agent dilution prepared in step S15 and direct mixing water to the mixer, add the pore-forming agent and foam stabilizer, stir at a speed of 250-300r / min for 2-3min to form a cement slurry without lumps and uniform fluidity;

[0064] S23, add the recycled aggregate and lightweight aggregate, stir at a speed of 150-200r / min for 1-1.5min, then add the carbonation-resistant additive, stir at a speed of 100-150r / min for 0.5-2min until all components are evenly mixed;

[0065] S3, pouring and forming: slowly pour the mixed and stirred mixture into the mold, pour to a height of 5-10mm higher than the top edge of the mold, start the vibration table, and vibrate at a low frequency of 30-50Hz for 20-30s until the surface is free of obvious bubbles and tends to be flat, use a scraper to remove the excess mixture on the top edge of the mold, trim the surface to be flat, immediately cover it with plastic film, and let it stand for 1-2h;

[0066] S4, segmented maintenance:

[0067] S41, standard maintenance: move the mold covered with the film into a standard curing room, control the temperature at 20 DEG C, the relative humidity is greater than or equal to 95%, standard curing for 7 days, check the film sealing property every day, if the condensed water is insufficient, spray clean water appropriately;

[0068] S42, natural maintenance: after standard curing for 7 days, demoulding, transfer the plate to a ventilated and light-avoiding place, cover with a wet cloth and spray water twice a day to keep the surface wet, the environmental temperature is not less than 5 DEG C, natural curing for 21 days, and light-weight porous concrete plate is obtained.

[0069] The beneficial effects obtained by the present application are as follows:

[0070] The present application provides an environment-friendly light-weight porous concrete plate and a preparation method thereof, and the present application realizes the comprehensive performance of the concrete plate, such as light weight, high strength, high toughness and environmental protection, through interface optimization and functionalization of modified fibers, efficient utilization of solid waste resources, precise raw material pretreatment and process control, wherein the modified fibers solve the pain points of traditional polypropylene fibers and cement-based matrix, such as weak interface combination and easy agglomeration, through multi-step chemical modification, and are the key to improving strength and toughness; the large-scale application of fly ash and waste concrete recycled aggregate realizes the synergy of environmental protection and performance; and staged mixing and precise curing guarantee material uniformity and hydration sufficiency. In the modified fibers involved in the present application, the hydroxyl group in the enol compound is protected to avoid free radical reaction caused by the initiator in the subsequent reaction process, peroxide dicumyl DCP is used as an initiator, free radicals are generated by decomposition of DCP in a high-temperature melting environment of a double-screw extruder, PP free radicals are formed by attacking the PP main chain, addition reaction occurs between the PP free radicals and the double bond of the protective monomer, the grafting of the protective monomer on the PP main chain is realized, modified PP particles are finally granulated, the aluminum-oxygen bond of the modified PP particles is hydrolyzed into hydroxyl groups after the modified PP particles are spun into fibers under certain conditions, the residual aluminum ions are chelated with 0.05wt% EDTA aqueous solution to avoid the influence of impurities on the subsequent reaction, a large number of free hydroxyl groups are introduced on the surface of the PP fibers, the polarity is significantly improved, the hydroxyl groups can form hydrogen bonds with the hydroxyl groups of the cement hydration products, the interface bonding force between the fibers and the matrix is preliminarily enhanced, the PDA forms hydrogen bonds / ester bonds with the hydroxyl groups on the surface of the fibers through the ortho-phenol groups, is tightly attached to the surface of the fibers, and forms a uniform coating, the ortho-phenol and amino groups of the PDA can form C-S-H gel and Ca 2+ OH in the cement-based matrix through chemical adsorption, further strengthen the interface bonding, the amino and ortho-phenol groups on the surface of the PDA can coordinate with metal ions (such as Cu 2+ ), providing anchoring sites for the next step of copper oxalate deposition, the amino / ortho-phenol groups of the PDA coating coordinate with Cu 2+ in copper nitrate; adjust the pH to optimize Cu2+ The coordination efficiency of PDA, dropwise addition of ammonium oxalate, Cu 2+ reacts with oxalate (C2O4 2- ) to form copper oxalate (CuC2O4) nanoparticles / microparticles, which are deposited on the surface of the PDA coating. The copper oxalate particles form a concave-convex structure on the fiber surface, which forms a mechanical interlocking force with the cement paste, greatly improving the interfacial frictional resistance and preventing the fiber from being easily pulled out; Cu 2+ can act as a trace catalyst for cement hydration, promoting the generation of C-S-H gel, making the fiber-matrix interface area more dense, and reducing microcracks. Copper oxalate itself has a certain strength, and cooperates with the PDA coating to improve the mechanical properties of the fiber itself. When the concrete is subjected to tension / compression, the uniformly dispersed modified fiber can transfer the stress from the matrix to the fiber through hydrogen bonding, chemical adsorption, and mechanical interlocking, preventing the stress concentration from causing crack initiation. If the matrix has already produced microcracks, the fiber will span the crack, pull the two sides of the crack through the interfacial bonding force, prevent the crack from expanding into a macroscopic crack, and form a bridging effect, greatly improving the toughness. Dense effect: the copper oxalate on the surface of the fiber catalyzes the generation of C-S-H gel, filling the interfacial voids and reducing the porosity of the matrix, while the skeleton effect of the fiber itself can inhibit the shrinkage of concrete, further improving the compressive strength.

[0071] The core function of the pore-forming agent is to reduce the air-liquid interfacial tension through the amphiphilic structure, stabilize the air bubbles during stirring, or promote chemical gas production. The -SO3 - group introduced by sulfonation has strong hydrophilicity and can be adsorbed on the surface of the bubbles to form a charge repulsion, which, together with the foam stabilizer, further prevents the bubbles from merging or breaking, ensuring uniform pore distribution. The closed pore structure can reduce the thermal conductivity coefficient and improve the thermal insulation performance of the board. The semi-open pore structure can alleviate the water expansion pressure during freeze-thaw cycles through capillary adsorption, improving the frost resistance. The PEG chain in the pore-forming agent molecule has water retention properties, which can reduce the bleeding of concrete and avoid surface pore defects caused by water loss, indirectly improving the impermeability. The PDA coating on the surface of the modified fiber can be combined with the sulfonic acid and carboxyl groups of the pore-forming agent through hydrogen bonding or electrostatic attraction, allowing the pore-forming agent molecules to be adsorbed on the fiber surface to form a fiber-pore-forming agent composite interface. The amphiphilic nature of the pore-forming agent can reduce the interfacial energy between the fibers, further improving the dispersibility of the fibers. The fiber acts as an air bubble anchor point, fixing the position of the bubbles and reducing the escape of bubbles during vibration, improving the stability of the pores. Although the pore-forming agent reduces the density, the pores can become stress concentration points, which may lead to a decrease in compressive / flexural strength. However, the modified fiber can specifically strengthen the weak areas around the pores through the bridging-dispersing stress effect. When the concrete is stressed, the fiber spanning the microcracks on the edge of the pores transfers the stress to the surrounding matrix, offsetting the strength loss caused by the pores. BRIEF DESCRIPTION OF DRAWINGS

[0072] Figure 1Fig. 1 is a graph showing the thermal insulation performance of the concrete slabs prepared in Examples 1-3 and Comparative Examples 1-3 of the present application;

[0073] Figure 2 Fig. 2 is a graph showing the mechanical properties of the concrete slabs prepared in Examples 1-3 and Comparative Examples 1-3 of the present application;

[0074] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the specification, illustrate the embodiments of the present application and explain the present application, and are used to explain the present application together with the embodiments of the present application, but do not limit the present application. DETAILED DESCRIPTION

[0075] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0076] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by one of ordinary skill in the art. In addition, any method and material similar or equivalent to those described herein can be used in the present application. The preferred methods and materials described herein are only used for demonstration, but cannot limit the content of the present application.

[0077] The experimental methods in the following examples are all conventional methods unless otherwise specified. The experimental materials and strains used in the following examples are all purchased from commercial channels unless otherwise specified.

[0078] Example 1

[0079] The present embodiment provides an environmentally friendly lightweight porous concrete slab, which comprises the following components by weight: cement 30 parts, fly ash 30 parts, waste concrete recycled aggregate 5 parts, expanded perlite 15 parts, modified fiber 1 part, polycarboxylate superplasticizer 0.9 part, silane coupling agent KH-560 0.6 part, pore-forming agent 0.8 part, foam stabilizer 0.3 part.

[0080] The preparation method of the modified fiber specifically comprises the following steps:

[0081] A1, 10-undecene-1-al 1.7 g is taken in a flask, 20 mL of dry toluene is added to the flask, and stirring is carried out at a speed of 200 rpm until the 10-undecene-1-al is completely dissolved. 3.0 g of triisobutylaluminum is dissolved in 15 mL of anhydrous toluene, and is added to the reaction system at a speed of 1 drop / s. The reaction system is transferred to an ice water bath, and is kept at a speed of 200 rpm for 3 h under a nitrogen atmosphere to obtain an enol protected monomer solution.

[0082] A2, take the homopolymerization polypropylene powder 50 g, the enol protection monomer solution prepared in step A1 15 g, DCP 0.25 g and anhydrous toluene 2.5 g, under the atmosphere of nitrogen, add into the high-speed mixer, stirring reaction under the condition of room temperature at the speed of 1000 rpm, after the reaction system is uniformly mixed, transfer to the twin-screw extruder for melt grafting reaction, set the temperature parameters of melt grafting reaction as follows: feeding section: 145℃; compression section: 155℃; melt reaction section: 168℃; homogenization section: 172℃; die head: 168℃, set the screw speed of the twin-screw extruder as 85 rpm, the melt is extruded through the die head, granulated, and modified polypropylene particles are obtained;

[0083] A3, melt spinning of the modified polypropylene particles prepared in step A2, placing in 0.2 mol / L hydrochloric acid aqueous solution, increasing the reaction temperature to 40℃, stirring reaction, reaction for 1 h, filtering, collecting the fiber, washing with deionized water until neutral, then placing in 0.05 wt% EDTA aqueous solution for 30 min, filtering, collecting the fiber, washing with deionized water, and vacuum drying at 60℃ for 8 h to obtain modified polypropylene fiber;

[0084] A4, taking 5.0 g of the modified polypropylene fiber prepared in step A3, soaking in 50 mL of 0.1% ammonia water solution, standing for 15 min, then taking out and washing the modified polypropylene fiber with deionized water until neutral, taking 0.3 g of dopamine hydrochloride and dissolving in 100 mL of 0.05 mol / L Tris-HCl buffer solution, adding the washed modified polypropylene fiber, stirring at room temperature for 2 h, after the reaction is completed, filtering, collecting the fiber, repeatedly washing with deionized water for 3 times, and vacuum drying at 30℃ for 6 h to obtain PDA-modified polypropylene fiber;

[0085] A5, taking 5.0 g of the PDA-modified polypropylene fiber prepared in step A4, adding to 50 mL of 0.15 mol / L copper nitrate aqueous solution, mixing at room temperature at the speed of 200 rpm for 1 h, adjusting the pH of the reaction system to 5.5, after mixing uniformly, adding 50 mL of 0.15 mol / L ammonium oxalate aqueous solution dropwise at the speed of 1 mL / min, increasing the reaction temperature to 50℃, stirring at the speed of 400 rpm, and performing deposition reaction, reaction for 45 min, after the reaction is completed, cooling the reaction system to room temperature, filtering, collecting the fiber, washing with deionized water until neutral, and vacuum drying at 60℃ for 6 h to obtain modified fiber;

[0086] The preparation method of the pore-forming agent specifically includes the following steps:

[0087] B1, 3-amino phenol hydrochloride 7.2 g was dissolved in 50 mL of deionized water, 4.2 g of sodium bicarbonate was added to the reaction system in 3 times, and stirring was continued at a speed of 200 rpm until no bubbles were generated. After the light brown solid was precipitated, it was left to stand for 10 min, vacuum filtration was performed, and the solid was washed with ice water. After vacuum drying at 60 °C for 2 h, 3-amino phenol was obtained;

[0088] B2, resorcinol 4.8 g was taken and placed in a flask, 50 mL of anhydrous toluene was added, and stirring was continued until the resorcinol was completely dissolved. Then 0.72 g of p-toluenesulfonic acid was added, and after uniform mixing, 4.8 g of 3-amino phenol prepared in B1 was added, and uniform reaction system was obtained by continuing to mix. The reaction temperature was raised to 120 °C, and reflux reaction was performed for 4 h. After the reaction was completed, heating was stopped, and after the reaction system was cooled to room temperature, 50 mL of ice water was added to the reaction system, stirring was continued until the solid was completely precipitated, vacuum filtration was performed, and the solid was washed with ice water for 3 times. After purification, vacuum drying at 60 °C for 2 h, 3,3'-dihydroxydiphenylamine was obtained;

[0089] B3, 7.0 g of 3,3'-dihydroxydiphenylamine prepared in step B2 was taken and placed in a flask, 60 mL of acetone was added, and stirring was continued until the 3,3'-dihydroxydiphenylamine was completely dissolved. Then 9.7 g of anhydrous K2CO3 was added to the reaction system, and after uniform mixing, 7.3 mL of 1-bromooctane was added to the reaction system at a rate of 1 drop / s. After the dropwise addition was completed, the reaction temperature was raised to 55 °C, and reflux reaction was performed for 5 h. After the reaction was completed, heating was stopped, and after the reaction system was naturally cooled to room temperature, vacuum filtration was performed, and the filtrate was collected. After removing the excess reaction solvent by distillation under reduced pressure, purification was performed, and long-chain modified 3,3'-dihydroxydiphenylamine was obtained;

[0090] B4, 1.0 g of long-chain modified 3,3'-dihydroxydiphenylamine prepared in step B3 was accurately weighed and placed in a flask, 10 mL of anhydrous DMF was added, and stirring was performed at a speed of 180 rpm. After the long-chain modified 3,3'-dihydroxydiphenylamine was completely dissolved, 1.8 g of anhydrous K2CO3 was added, and after uniform mixing, nitrogen gas was introduced into the reaction system. 1.8 g of Br-PEG-OH was dissolved in 5 mL of anhydrous DMF, and was added dropwise to the reaction system at a rate of 1 drop / s. After the dropwise addition was completed, the reaction temperature was raised to 70 °C, and substitution reaction was performed for 6 h. After the reaction was completed, the reaction system was cooled to room temperature, vacuum filtration was performed, and the filtrate was collected. After removing the excess reaction solvent by rotary evaporation, 50 mL of anhydrous ether was added for sedimentation purification, vacuum filtration was performed, and the precipitate was washed with anhydrous ether. After vacuum drying at 50 °C for 4 h, PEG modified intermediate was obtained;

[0091] B5, accurately weigh 1.75 g of the PEG modified intermediate prepared in step B4 and dissolve it in 10 mL of anhydrous toluene, add 45 mg of p-toluenesulfonic acid, mix well, then add 0.6 g of maleic anhydride, stir to form a uniform system, then pass flowing nitrogen for 20 min, increase the reaction temperature to 85℃, and reflux for 5 h. After the reaction is completed, cool the reaction system to room temperature, add saturated sodium bicarbonate aqueous solution to the reaction system for repeated washing, collect the organic phase, wash with deionized water, then dehydrate the organic phase with anhydrous sodium sulfate, vacuum filter to collect the filtrate, concentrate by rotary evaporation, and purify to obtain an esterified intermediate product;

[0092] B6, dissolve 0.65 g of sodium bisulfite in an ethanol aqueous solution (V 乙醇 :V 水 =1:3), slowly add 1.7 g of the esterified intermediate product prepared in step B5, increase the reaction temperature to 65℃, and perform sulfonation reaction for 4 h. After the reaction is completed, cool the reaction system to room temperature, then remove unreacted SO3 - with deionized water by dialysis, concentrate under reduced pressure, and freeze-dry to obtain a pore-forming agent.

[0093] The application also provides a preparation method of the environmentally friendly lightweight porous concrete slab, and specifically comprises the following steps:

[0094] S1: raw material pretreatment:

[0095] S11, fly ash treatment: place the fly ash into a 100℃ drying oven, dry until the water content is ≤1%, then pass through a 80-mesh standard sieve to remove coarse particles and unburned carbon particles, to obtain pretreated fly ash for standby use;

[0096] S12, recycled aggregate treatment: take the waste aggregate, crush it with a jaw crusher, then sieve it with a 5mm aperture sieve, repeatedly wash it with clean water until there is no floating dust on the surface, and dry it under ventilation until the water content is 3%, for standby use;

[0097] S13, lightweight aggregate treatment: select the lightweight aggregate, soak it in advance for 2 h, then drain it until there is no water on the surface, for standby use;

[0098] S14, modified fiber pretreatment: cut the modified fiber into 6mm short fibers, dry mix the short fibers with the pretreated fly ash prepared in step S11 for 1 min to realize fiber pre-dispersion, to obtain pre-dispersed modified fibers for standby use;

[0099] S15, dilute the water reducing agent with mixing water to obtain a 10% water solution of the water reducing agent, for standby use;

[0100] S16: take water according to the water-cement ratio (water / fly ash+fly ash) of 0.4, wherein 10% of the water is used to dilute the water reducing agent, and the remaining water is directly used for mixing.

[0101] S2, mixing in stages:

[0102] S21, put cement, pre-dispersed modified fiber into the mixer, stir at 150 r / min for 2 min, until the fiber is evenly distributed;

[0103] S22, slowly add water reducing agent diluent and direct mixing water to the mixer, add pore-forming agent and foam stabilizer, stir at 250 r / min for 3 min, form a cement paste without lumps and uniform flowability;

[0104] S23, add recycled aggregate, light aggregate, stir at 150 r / min for 1.5 min, then add carbonation-resistant additive, stir at 100 r / min for 2 min, until all components are mixed evenly;

[0105] S3, pouring and forming: slowly pour the mixed mixture into the mold, the pouring height is 10 mm higher than the upper edge of the mold, start the vibration table, low frequency 50 Hz vibration for 30 s, until the surface is free of obvious bubbles and tends to be flat, use a scraper to remove the excess mixture on the upper edge of the mold, trim the surface to be flat, immediately cover the plastic film, and stand for 2 h;

[0106] S4, segmented curing:

[0107] S41, standard curing: move the covered mold into the standard curing room, control the temperature at 20℃ and the relative humidity at ≥95%, standard curing for 7 days, check the film sealing every day, if the condensate water is insufficient, spray clean water appropriately;

[0108] S42, natural curing: after standard curing for 7 days, demold the plate and transfer it to a well-ventilated and light-protected place, cover it with a wet cloth and spray water 2 times a day to keep the surface moist, the environmental temperature should not be lower than 5℃, and the plate should be naturally cured for 21 days to obtain a lightweight porous concrete plate.

[0109] Example 2

[0110] The present embodiment provides an environmentally friendly lightweight porous concrete plate, which comprises the following components by weight: cement 40 parts, fly ash 20 parts, waste ceramic recycled aggregate 10 parts, expanded slag beads 22 parts, modified fiber 0.5 parts, polycarboxylic acid type water reducing agent 1.2 parts, silane coupling agent KH-550 0.9 parts, pore-forming agent 1 part, foam stabilizer 0.4 parts;

[0111] The preparation method of the modified fiber specifically comprises the following steps:

[0112] A1, 5-hexen-1-ol 1.0 g was taken in a flask, 20 mL of dry toluene was added to the flask, and stirring was carried out at a speed of 300 rpm until 10-undecen-1-ol was completely dissolved. Trimethylaluminum 1.2 g was dissolved in 15 mL of anhydrous toluene, and was added to the reaction system at a speed of 1 drop / s. The reaction system was transferred to an ice water bath, and was kept under a nitrogen atmosphere at a speed of 200 rpm for 3 h to obtain an enol-protected monomer solution;

[0113] A2, homopolymerized polypropylene powder 50 g, enol-protected monomer solution prepared in step A1 20 g, DCP 0.35 g, and anhydrous toluene 3.5 g were added to a high-speed mixer under a nitrogen atmosphere, and stirring was carried out at a speed of 1000 rpm at room temperature. After the reaction system was uniformly mixed, it was transferred to a twin-screw extruder for melt grafting reaction. The temperature parameters of the melt grafting reaction were set as follows: feeding section, 135°C; compression section, 145°C; melt reaction section, 162°C; homogenization section, 168°C; die head, 162°C. The screw rotation speed of the twin-screw extruder was set as 115 rpm. The melt was extruded through a die, and was granulated to obtain modified polypropylene particles;

[0114] A3, the modified polypropylene particles prepared in step A2 were subjected to melt spinning, were placed in 0.35 mol / L hydrochloric acid aqueous solution, and were subjected to stirring reaction by increasing the reaction temperature to 35°C. After 1.5 h, the fibers were collected by filtration, were washed with deionized water until neutral, were immersed in 0.05 wt% EDTA aqueous solution for 30 min, were collected by filtration, were washed with deionized water, and were vacuum dried at 60°C for 8 h to obtain modified polypropylene fibers;

[0115] A4, the modified polypropylene fibers prepared in step A3 5.0 g were immersed in 50 mL of 0.1% ammonia aqueous solution, and were left to stand for 15 min. The modified polypropylene fibers were taken out, and were washed with deionized water until neutral. Dopamine hydrochloride 0.45 g was dissolved in 100 mL of 0.05 mol / L Tris-HCl buffer, and the washed modified polypropylene fibers were added. Stirring was carried out at room temperature for 2.5 h. After the reaction was completed, the fibers were collected by filtration, were repeatedly washed with deionized water for 3 times, and were vacuum dried at 30°C for 6 h to obtain PDA-modified polypropylene fibers;

[0116] A5, 5.0 g of the PDA-modified polypropylene fiber prepared in step A4 was added to 30 mL of a 0.2 mol / L aqueous copper nitrate solution, mixed at a speed of 200 rpm for 1 h at room temperature, then the pH of the reaction system was adjusted to 5.2, after uniform mixing, 30 mL of a 0.2 mol / L aqueous ammonium oxalate solution was added dropwise at a speed of 1 mL / min, the reaction temperature was raised to 60°C, and the deposition reaction was carried out under stirring at a speed of 400 rpm, for 30 min, after the reaction was completed, the reaction system was cooled to room temperature, filtered, and the fiber was collected, washed to neutral with deionized water, and then vacuum dried at 60°C for 6 h to obtain the modified fiber;

[0117] The preparation method of the pore-forming agent specifically includes the following steps:

[0118] B1, 8.0 g of 3-aminophenol hydrochloride was dissolved in 50 mL of deionized water, 5.0 g of sodium bicarbonate was added to the reaction system in three portions, and stirring was continued at a speed of 200 rpm until no gas bubbles were generated, then the system was allowed to stand for 10 min, vacuum filtration was performed, the solid was washed with ice water, and then vacuum dried at 60°C for 2 h to obtain 3-aminophenol;

[0119] B2, 6.0 g of resorcinol was placed in a flask, 50 mL of anhydrous toluene was added, stirring was performed until the resorcinol was completely dissolved, then 0.8 g of p-toluenesulfonic acid was added, uniform mixing was continued, then 5.0 g of 3-aminophenol prepared in B1 was added, uniform mixing was continued to obtain a uniform reaction system, the reaction temperature was raised to 130°C, and refluxing was performed for 3 h, after the reaction was completed, heating was stopped, the reaction system was allowed to cool to room temperature, then 50 mL of ice water was added to the reaction system, stirring was performed until the solid was completely precipitated, vacuum filtration was performed, the solid was washed with ice water for 3 times, then purification was performed, and vacuum drying was performed at 60°C for 2 h to obtain 3,3'-dihydroxydiphenylamine;

[0120] B3, 7.5 g of 3,3'-dihydroxydiphenylamine prepared in step B2 was placed in a flask, 60 mL of acetone was added, stirring was performed until the 3,3'-dihydroxydiphenylamine was completely dissolved, then 10.5 g of anhydrous K2CO3 was added to the reaction system, uniform mixing was performed, then 1-bromononane 9.2 mL was added to the reaction system at a speed of 1 drop / s, after the dropwise addition was completed, the reaction temperature was raised to 50°C, and refluxing was performed for 6 h, after the reaction was completed, heating was stopped, the reaction system was allowed to cool to room temperature naturally, vacuum filtration was performed, the filtrate was collected, excess reaction solvent was removed by distillation under reduced pressure, and then purification was performed to obtain long-chain modified 3,3'-dihydroxydiphenylamine;

[0121] B4, accurately take 1.25g of long-chain modified 3, 3'-dihydroxydiphenylamine prepared in step B3 into a flask, add 10mL of anhydrous DMF, and stir at a speed of 180rpm, after the long-chain modified 3, 3'-dihydroxydiphenylamine is completely dissolved, add 2.4g of anhydrous K2CO3, mix uniformly, then introduce flowing nitrogen into the reaction system, dissolve 2.2g of Br-PEG-OH in 5mL of anhydrous DMF, and add it dropwise into the reaction system at a speed of 1 drop / s, after the dropwise addition is completed, increase the reaction temperature to 75℃, and perform substitution reaction, the reaction is performed for 5.5h, after the reaction is completed, the reaction system is cooled to room temperature, vacuum filtration is performed, the filtrate is collected, rotary evaporation is performed to remove excess reaction solvent, 50mL of anhydrous ether is added for sedimentation purification, vacuum filtration is performed, the precipitate is repeatedly washed with anhydrous ether, and vacuum drying is performed at 50℃ for 4h to obtain a PEG modified intermediate;

[0122] B5, accurately take 2.1g of the PEG modified intermediate prepared in step B4 and dissolve it in 10mL of anhydrous toluene, add 60mg of p-toluenesulfonic acid, mix uniformly, then add 0.7g of maleic anhydride, stir to form a uniform system, introduce flowing nitrogen for 20min, increase the reaction temperature to 80℃, and perform reflux reaction, the reaction is performed for 6h, after the reaction is completed, the reaction system is cooled to room temperature, saturated sodium bicarbonate aqueous solution is added to the reaction system for repeated washing, the organic phase is collected and washed with deionized water, then the organic phase is dehydrated with anhydrous sodium sulfate, the filtrate is collected by vacuum filtration, rotary evaporation is performed for concentration, and after purification, an esterification intermediate product is obtained;

[0123] B6, dissolve 0.75g of sodium bisulfite in an ethanol aqueous solution (V 乙醇 :V 水 =1:3), slowly add 2.1g of the esterification intermediate product prepared in step B5, increase the reaction temperature to 70℃, perform sulfonation reaction, the reaction is performed for 3.5h, after the reaction is completed, the reaction system is cooled to room temperature, deionized water is used for dialysis to remove unreacted SO3 - , vacuum concentration, and freeze-drying to obtain a pore-forming agent;

[0124] The application further provides a preparation method of the environmentally friendly lightweight porous concrete slab.

[0125] S1: raw material pretreatment

[0126] S11, fly ash treatment: the fly ash is placed into a 110℃ drying oven, and is dried until the water content is ≤1%; then, the fly ash is sieved through a 80-mesh standard sieve to remove coarse particles and unburned carbon particles, and a pretreated fly ash is obtained for standby use;

[0127] S12. Recycled aggregate processing: Take waste aggregate, crush it with a jaw crusher, screen it with a 10mm mesh screen, rinse it repeatedly with clean water until there is no floating dust on the surface, and dry it in a ventilated place until the moisture content is 4% for later use.

[0128] S13 Lightweight aggregate treatment: Select lightweight aggregate, soak it for 2 hours in advance, then drain it until there is no visible water on the surface, and set it aside.

[0129] S14. Modified fiber pretreatment: Cut the modified fiber into 12mm short fibers, mix them with the pretreated fly ash prepared in step S11, and dry mix for 1 minute to achieve fiber predispersion and obtain predispersed modified fiber for later use.

[0130] S15. Dilute the water-reducing agent with mixing water to a 10% aqueous solution to obtain a diluted water-reducing agent solution for later use.

[0131] S16: Water is taken according to a water-cement ratio (water / cement + fly ash) of 0.45, of which 10% of the water is used to dilute the water-reducing agent and the remainder is used for direct mixing.

[0132] S2. Staged mixing and stirring:

[0133] S21. Add cement and pre-dispersed modified fiber into a mixer and mix at 200 r / min for 1 min until the fiber is evenly distributed.

[0134] S22. Slowly add water-reducing agent dilution and direct mixing water to the mixer, add pore-forming agent and foam stabilizer, and stir at 300 r / min for 2 minutes to form a cement slurry without lumps and with uniform fluidity.

[0135] S23. Add recycled aggregate and lightweight aggregate, stir at 100 r / min for 1 min, then add anti-carbonization additive, stir at 150 r / min for 0.5 min, until all components are mixed evenly.

[0136] S3. Casting and molding: Slowly pour the well mixed mixture into the mold, with the pouring height 5mm higher than the upper edge of the mold. Start the vibrating table and vibrate at a low frequency of 30Hz for 20 seconds until there are no obvious bubbles on the surface and it tends to be flat. Use a scraper to scrape off the excess mixture at the upper edge of the mold, and trim the surface to be flat. Immediately cover with plastic film and let it stand for 1 hour.

[0137] S4. Segmented maintenance:

[0138] S41. Standard curing: Move the mold covered with film into the standard curing room, control the temperature at 20℃ and the relative humidity at ≥95%, and cure for 7 days. Check the film sealing daily. If there is insufficient condensation, spray water appropriately.

[0139] S42, natural curing: after 7 days of standard curing, demolding, transferring the plate to a ventilated, light-avoiding site, covering with a wet cloth and spraying water twice a day to keep the surface moist, keeping the ambient temperature not lower than 5℃, and naturally curing for 21 days to obtain the lightweight porous concrete plate.

[0140] Example 3

[0141] The embodiment provides an environmentally friendly lightweight porous concrete plate, which comprises the following components in parts by weight: cement 35 parts, fly ash 25 parts, waste concrete recycled aggregate 15 parts, expanded perlite 30 parts, modified fiber 0.8 part, polycarboxylate superplasticizer 0.6 part, silane coupling agent KH-560 1.2 part, pore-forming agent 1.5 part, foam stabilizer 0.5 part.

[0142] The preparation method of the modified fiber specifically comprises the following steps:

[0143] A1, 2.0 g of 9-decene-1-ol was taken into a flask, 20 mL of dry toluene was added to the flask, and the stirring speed was 250 rpm until the 10-undecene-1-ol was completely dissolved, 2.2 g of triethylaluminum was dissolved in 15 mL of anhydrous toluene, and was added to the reaction system at a speed of 1 drop / s, the reaction system was transferred to an ice water bath, and the stirring speed was kept at 200 rpm for 3 h under a nitrogen atmosphere to obtain an enol-protected monomer solution;

[0144] A2, 50 g of homopolymerized polypropylene powder, 25 g of the enol-protected monomer solution prepared in step A1, 0.4 g of DCP and 5 g of anhydrous toluene were added to a high-speed mixer under a nitrogen atmosphere, and stirring was carried out at a speed of 1000 rpm and room temperature, after the reaction system was uniformly mixed, it was transferred to a twin-screw extruder for melt grafting reaction, the temperature parameters of the melt grafting reaction were set as follows: feeding section: 140℃; compression section: 150℃; melt reaction section: 165℃; homogenization section: 170℃; die head: 165℃, and the screw rotation speed of the twin-screw extruder was set as 100 rpm, the melt was extruded through a die, and was granulated to obtain modified polypropylene particles;

[0145] A3, the modified polypropylene particles prepared in step A2 were melt-spun, were placed in a 0.5 mol / L hydrochloric acid aqueous solution, the reaction temperature was increased by 30℃, and stirring was carried out, the reaction was carried out for 2 h, filtration was carried out, the fibers were collected, were washed with deionized water until neutral, were then placed in a 0.05wt% EDTA aqueous solution for 30 min, were filtered, the fibers were collected, were washed with deionized water, and were vacuum dried at 60℃ for 8 h to obtain modified polypropylene fibers;

[0146] A4, 5.0 g of the modified polypropylene fiber prepared in step A3 was immersed in 50 mL of 0.1% ammonia water solution, and after standing for 15 min, it was taken out and washed with deionized water until neutral. 0.6 g of dopamine hydrochloride was dissolved in 100 mL of 0.05 mol / L Tris-HCl buffer, and the washed modified polypropylene fiber was added. After stirring at room temperature for 3 h, the reaction was completed, and the fiber was collected by filtration and washed repeatedly with deionized water for 3 times. After vacuum drying at 30°C for 6 h, PDA-modified polypropylene fiber was obtained;

[0147] A5, 5.0 g of the PDA-modified polypropylene fiber prepared in step A4 was added to 20 mL of 0.3 mol / L copper nitrate aqueous solution, and after mixing at 200 rpm for 1 h at room temperature, the pH of the reaction system was adjusted to 5.0. After mixing uniformly, 20 mL of 0.15 mol / L ammonium oxalate aqueous solution was added dropwise at a rate of 1 drop / s, and the reaction temperature was raised to 50°C. The deposition reaction was carried out by stirring at 400 rpm. After 45 min of reaction, the reaction system was cooled to room temperature, and the fiber was collected by filtration and washed with deionized water until neutral. After vacuum drying at 60°C for 6 h, the modified fiber was obtained.

[0148] The preparation method of the pore-forming agent specifically includes the following steps:

[0149] B1, 8.6 g of 3-aminophenol hydrochloride was dissolved in 50 mL of deionized water, and 6.0 g of sodium bicarbonate was added to the reaction system in three portions. Stirring was continued at 200 rpm until no gas bubbles were generated. After the light brown solid was precipitated, it was allowed to stand for 10 min, and then vacuum filtration was performed. After washing the solid with ice water, vacuum drying was performed at 60°C for 2 h to obtain 3-aminophenol.

[0150] B2, 6.72 g of resorcinol was placed in a flask, 50 mL of anhydrous toluene was added, and after stirring until the resorcinol was completely dissolved, 1.0 g of p-toluenesulfonic acid was added. After uniform mixing, 6.0 g of 3-aminophenol prepared in B1 was added, and the reaction system was continuously mixed to obtain a uniform reaction system. The reaction temperature was raised to 125°C, and refluxing was performed for 3.5 h. After the reaction was completed, the heating was stopped, and the reaction system was cooled to room temperature. Then, 50 mL of ice water was added to the reaction system, and stirring was performed until the solid was completely precipitated. Vacuum filtration was performed, and the solid was washed repeatedly with ice water for 3 times. After purification, vacuum drying was performed at 60°C for 2 h to obtain 3,3'-dihydroxydiphenylamine.

[0151] B3, 3,3'-dihydroxydiphenylamine 8.5 g prepared in step B2 was placed in a flask, 60 mL of acetone was added, and after stirring until the 3,3'-dihydroxydiphenylamine was completely dissolved, 11.6 g of anhydrous K2CO3 was added to the reaction system, and after mixing uniformly, 1-bromodecane 10.8 mL was added to the reaction system at a rate of 1 drop / s, after the dropwise addition was completed, the reaction temperature was raised to 60°C, and reflux reaction was carried out, and the reaction was carried out for 4 h, after the reaction was completed, the heating was stopped, and after the reaction system was naturally cooled to room temperature, vacuum filtration was carried out, the filtrate was collected, the excess reaction solvent was removed by reduced pressure distillation, and after purification, long-chain modified 3,3'-dihydroxydiphenylamine was obtained;

[0152] B4, long-chain modified 3,3'-dihydroxydiphenylamine 1.5 g prepared in step B3 was accurately weighed and placed in a flask, 10 mL of anhydrous DMF was added, and stirring was carried out at a speed of 180 rpm, after the long-chain modified 3,3'-dihydroxydiphenylamine was completely dissolved, 3.0 g of anhydrous K2CO3 was added, and after mixing uniformly, flowing nitrogen was introduced into the reaction system, Br-PEG-OH 2.5 g was dissolved in 5 mL of anhydrous DMF, and was added dropwise to the reaction system at a rate of 1 drop / s, after the dropwise addition was completed, the reaction temperature was raised to 80°C, and substitution reaction was carried out, and the reaction was carried out for 5 h, after the reaction was completed, the reaction system was cooled to room temperature, vacuum filtration was carried out, the filtrate was collected, and the excess reaction solvent was removed by rotary evaporation concentration, 50 mL of anhydrous ether was added for sedimentation purification, vacuum filtration was carried out, the precipitate was collected, and was repeatedly washed with anhydrous ether, and after vacuum drying at 50°C for 4 h, a PEG modified intermediate was obtained;

[0153] B5, the PEG modified intermediate 2.5 g prepared in step B4 was accurately weighed and dissolved in 10 mL of anhydrous toluene, 75 mg of p-toluenesulfonic acid was added, and after mixing uniformly, 0.8 g of maleic anhydride was added, and after stirring to form a uniform system, flowing nitrogen was introduced for 20 min, the reaction temperature was raised to 90°C, and reflux reaction was carried out, and the reaction was carried out for 4 h, after the reaction was completed, the reaction system was cooled to room temperature, saturated sodium bicarbonate aqueous solution was added to the reaction system for repeated washing, the organic phase was collected, and after washing with deionized water, the organic phase was dehydrated with anhydrous sodium sulfate, the filtrate was collected by vacuum filtration, and after rotary evaporation concentration, an esterification intermediate product was obtained after purification;

[0154] B6, sodium bisulfite 0.85 g was dissolved in an ethanol aqueous solution (V 乙醇 :V 水 =1:3), and the esterification intermediate product 2.5 g prepared in step B5 was slowly added, the reaction temperature was raised to 75°C, and sulfonation reaction was carried out, and the reaction was carried out for 3 h, after the reaction was completed, the reaction system was cooled to room temperature, and deionized water was used for dialysis to remove unreacted SO3 - , after reduced pressure concentration, freeze-drying was carried out, and a pore-forming agent was obtained;

[0155] The application further provides a preparation method of the environment-friendly light-weight porous concrete slab, and specifically comprises the following steps:

[0156] S1: raw material pretreatment:

[0157] S11, fly ash treatment: the fly ash is placed into a 100 DEG C drying oven, dried until the water content is less than or equal to 1%, then sieved through a 80-mesh standard sieve to remove coarse particles and unburned carbon particles, and the pretreated fly ash is obtained and reserved;

[0158] S12, recycled aggregate treatment: the waste aggregate is broken by a jaw crusher, then sieved through a 8-mm-aperture sieve, repeatedly washed with clean water until no floating dust is present on the surface, and dried by ventilation until the water content is 5%, and the aggregate is reserved;

[0159] S13, light aggregate treatment: the light aggregate is selected, soaked for 2 hours, then taken out and drained until no water is present on the surface, and the aggregate is reserved;

[0160] S14, modified fiber pretreatment: the modified fiber is cut into 10-mm short fibers, and then dry-mixed with the pretreated fly ash prepared in step S11 for 1 minute to realize fiber pre-dispersion, and the pre-dispersed modified fiber is obtained and reserved;

[0161] S15, the water reducing agent is diluted into a 10%-water solution by using mixing water to obtain a water reducing agent diluent, and the diluent is reserved;

[0162] S16: water is taken according to a water-cement ratio (water / fly ash+fly ash) of 0.4, wherein 10% of the water is used for diluting the water reducing agent, and the remaining water is directly used for mixing;

[0163] S2, mixing and stirring in stages:

[0164] S21, the cement and the pre-dispersed modified fiber are put into a stirrer, and stirred at a speed of 150 r / min for 2 minutes until the fiber is uniformly distributed;

[0165] S22, the water reducing agent diluent and the directly-mixed water are slowly added into the stirrer, and a pore-forming agent and a foam stabilizer are added, and stirred at a speed of 280 r / min for 3 minutes to form a cement slurry without lumps and with uniform fluidity;

[0166] S23, the recycled aggregate and the light aggregate are added, and stirred at a speed of 180 r / min for 1.5 minutes, and then the carbonization-resistant additive is added, and stirred at a speed of 120 r / min for 2 minutes until all components are uniformly mixed;

[0167] S3, pouring and forming: the mixed material is slowly poured into a mold, the pouring height is 10 mm higher than the upper edge of the mold, a vibrating table is started, and low-frequency vibration is performed at 40 Hz for 30 seconds until no obvious bubbles are present on the surface and the surface tends to be flat, the excess mixed material on the upper edge of the mold is scraped off by a scraper, the surface is trimmed to be flat, plastic film is immediately covered, and the product is left to stand for 1.5 hours.

[0168] S4, segment maintenance:

[0169] S41, standard maintenance: move the mold covered with the film into the standard maintenance room, control the temperature at 20℃ and the relative humidity at ≥95%, standard maintenance for 7 days, check the film sealing every day, if the condensed water is insufficient, spray clean water appropriately;

[0170] S42, natural maintenance: after standard maintenance for 7 days, demold and transfer the plate to a ventilated and light-avoiding place, cover with a wet cloth and spray water 2 times a day to keep the surface wet, the environmental temperature is not lower than 5℃, natural maintenance for 21 days, and obtain the lightweight porous concrete plate.

[0171] Comparative Example 1

[0172] The present comparative example provides a concrete plate and a preparation method thereof, which are different from Example 1 only in that the pore-forming agent is replaced by sodium dodecyl benzene sulfonate in the same weight fraction, and the remaining components and component contents are the same as those of Example 1.

[0173] Comparative Example 2

[0174] The present comparative example provides a concrete plate and a preparation method thereof, which are different from Example 1 only in that the modified fiber is replaced by polypropylene fiber in the same weight fraction, and the remaining components and component contents are the same as those of Example 1.

[0175] Comparative Example 3

[0176] The present comparative example provides a concrete plate and a preparation method thereof, which are different from Example 1 only in that the preparation method of the modified fiber does not include steps A4 and A5, and the remaining components and component contents are the same as those of Example 1.

[0177] Experimental Example 1

[0178] According to GB / T10294-2008 “Determination of Steady-state Thermal Resistance and Related Properties of Thermal Insulation Materials by Guarded Hot Plate Method”, a concrete plate test piece with a specification of 300mm×300mm×50mm is prepared, a guarded hot plate type thermal conductivity instrument is used, and the test conditions are set as follows: average temperature: 20±2℃, heat flow direction: perpendicular to the plane of the plate, steady-state judgment: record data when the heat flow density fluctuation is ≤2% / h, and calculate the thermal conductivity λ (W / (m·K)) according to the following formula:

[0179] λ=q×d / ΔT;

[0180] wherein q is the heat flow density (W / m 2 ), ΔT is the temperature difference (K), and d is the thickness of the test piece (m);

[0181] According to GB / T 10297-2015 "Determination of Thermal Conductivity of Nonmetallic Solid Materials Hot-wire Method", the concrete plate test piece with a specification of 200mmx200mmx50mm is prepared, and a hot-wire method thermal conductivity instrument is used for testing, and the heat storage coefficient S (W / (m 2 ⋅K) is calculated according to the following formula:

[0182] ;

[0183] Wherein, λ is the thermal conductivity (W / (m⋅K) ) ; c is the specific heat capacity (J / (kg⋅K) ), ρ is kg / m 3 ;

[0184] Figure 1 The heat insulation performance results of the concrete plates prepared in Examples 1-3 and Comparative Examples 1-3 of the present application are shown in the figure. In Example 1, a uniform closed pore structure is formed from the pore-forming agent, blocking the main path of heat conduction, and the modified fiber reduces the interface gap to avoid additional heat channels, both of which cooperate to achieve a low thermal conductivity. The pore-forming agent is modified by long-chain PEG and sulfonated to have strong foam stability, forming uniform closed pores with poor air flowability in the closed pores, which maximally blocks heat conduction. The modified fiber is grafted with 10-undecene-1-al, and then coated and deposited with copper oxalate. There is no obvious interface gap between the fiber and the matrix, and there is no additional heat channel. In Example 2, 5-hexene-1-al is used instead of 10-undecene-1-al to modify the fiber. The winding and anchoring effect of the fiber after grafting is weakened, and a small amount of micro gaps is generated at the interface, forming a weak heat channel, which slightly increases the thermal conductivity. In Example 3, the enol compound of the modified fiber is similar to that of Example 1, and its heat insulation performance is similar to that of Example 1. In Comparative Example 1, sodium dodecyl benzene sulfonate is a traditional anionic surfactant that relies on a single hydrophobic chain for foam stability. During the mixing and vibrating of the concrete, the bubbles are easily broken or combined to form a large number of large pores and connected pores. The air in the large pores has strong flowability, and the connected pores directly form a through heat channel, resulting in a significant decrease in thermal resistance and a significant increase in thermal conductivity. The high proportion of large pores leads to a low effective porosity, but the high heat storage coefficient only represents a strong heat storage capacity during temperature changes, which cannot compensate for the defect of excessively high thermal conductivity. Heat easily penetrates, and the heat insulation performance is still poor. In Comparative Example 2, unmodified polypropylene fiber is used instead of modified fiber. Polypropylene has strong hydrophobicity and poor compatibility with the hydrophilic cement matrix. Continuous interface gaps are formed between the fiber surface and the matrix, which act as small air ducts. Heat can be quickly conducted along the gaps, resulting in an increase in thermal conductivity. The increase in interface gaps leads to a loose overall structure, further reducing the thermal resistance of the matrix and exacerbating heat conduction.

[0185] Experimental Example 2

[0186] According to GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete", concrete plate specimens are prepared with a size of 100mmx100mmx100mm, and the compressive strength of the concrete specimens is tested by a universal testing machine. The upper and lower surfaces of the specimen are padded flat, aligned with the center of the testing machine, and loaded at a uniform speed until the specimen fails. The maximum failure load F is recorded, and the compressive strength f is calculated according to the following formula: cu (MPa):

[0187] ;

[0188] Where F is the maximum failure load (kN), A is the compressive area of the specimen (mm 2 ), and 0.95 is the size conversion coefficient.

[0189] According to GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete", concrete plate specimens are prepared with a size of 100mmx100mmx500mm, and the flexural strength of the concrete specimens is tested by a universal testing machine. The specimen ends are connected to the testing machine clamps, ensuring that the tension is along the axial direction, and the specimen is loaded at a uniform speed until it breaks. The maximum tensile force F is recorded, and the flexural strength f is calculated according to the following formula: f (MPa):

[0190] ;

[0191] Where F is the maximum failure load (kN), L is the support span (mm), b is the specimen width (mm), and h is the specimen height (mm).

[0192] According to GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete", concrete plate specimens are prepared with a size of 100mmx100mmx500mm, and the tensile strength of the concrete specimens is tested by a universal testing machine. The specimen ends are connected to the testing machine clamps, ensuring that the tension is along the axial direction, and the specimen is loaded at a uniform speed until it breaks. The maximum tensile force F is recorded, and the tensile strength f is calculated according to the following formula: t (MPa):

[0193] ;

[0194] Where F is the maximum failure load (kN), A is the tensile cross-sectional area of the specimen (mm 2 );

[0195] Figure 2The mechanical property results of the concrete plates prepared in Examples 1-3 and Comparative Examples 1-3 of the present application are shown in the figure. The three strengths of Examples 1-3 are significantly higher than those of Comparative Examples 1-3, and the improvement in flexural / tensile strength is much greater than that in compressive strength, which illustrates the technical logic of optimizing the load-bearing base and modifying the complete fiber to strengthen the toughness, and the comprehensive improvement of mechanical properties is achieved by the synergy of the two. The compressive strength is the ability of the material to resist axial compression, which is mainly affected by the quality of the pores, and then by the matrix density. The flexural strength is the ability of the material to resist bending failure, and the cross-section will produce a tensile stress zone when bending. The fiber needs to transfer stress through interfacial bonding to prevent crack propagation. The tighter the fiber and matrix bonding, the stronger the bridging effect and the higher the flexural strength. The tensile strength is the ability of the material to resist axial tension, which is almost entirely dependent on the tensile bearing capacity of the fiber due to the weak tensile resistance of the concrete matrix itself. The tighter the fiber and matrix bonding, the greater the tensile force that can be transferred and the higher the tensile strength. In the examples, uniform closed pores are formed by long-chain modification, PEG modification, and sulfonation. Closed pores do not damage the continuity of the matrix, and stress can be uniformly transferred. At the same time, the complete modified fiber reduces the interfacial gap and improves the matrix density. In Comparative Example 1, the use of traditional dodecylbenzenesulfonic acid sodium as a pore-forming agent leads to poor foam stability, forming a large number of large pores and interconnected pores. When under pressure, stress is concentrated at the interconnected pores, and the matrix cracks along the pore wall, resulting in a sudden drop in load-bearing capacity. In Comparative Example 2, unmodified polypropylene fiber is used, leading to poor matrix compatibility and the presence of interfacial gaps but no interconnected pore defects. The matrix continuity is better than that of Comparative Example 1, so the compressive strength is slightly higher. In Comparative Example 3, the fiber omits PDA and copper oxalate, resulting in the retention of enol grafting, small interfacial gaps, and slightly higher matrix density, so the compressive strength is higher than that of Comparative Examples 1-2.

[0196] In the examples, the fiber is enol-grafted, PDA-coated, and PDA-enhanced with copper oxalate to increase adhesion, and copper oxalate fills the gaps. The fiber and matrix form mechanical entanglement and chemical bonding, making it difficult to debond during bending. In Comparative Example 2, the unmodified fiber has strong hydrophobicity and no effective bonding with the matrix. During bending, the fiber instantaneously debonds and cannot bridge at all. Once a crack is generated, it penetrates the cross-section, resulting in the lowest flexural strength. Although the fiber in Comparative Example 1 is completely modified, the interconnected pores of the traditional pore-forming agent cause stress to concentrate along the interconnected pores during bending, and the crack rapidly expands. The pore defects dominate the flexural performance, so the flexural strength is only slightly higher than that of Comparative Example 2. In Comparative Example 3, the fiber omits PDA and copper oxalate, resulting in some bonding force with the matrix and weak bridging effect. Therefore, the flexural strength is higher than that of Comparative Examples 1-2.

[0197] In the examples, the fiber-matrix interface has no obvious gap. When subjected to tensile force, the fiber can transfer the tensile force from the fragile matrix to itself. In Comparative Example 1, the interconnected pores become the starting point of fracture under tensile force, and the crack penetrates along the interconnected pores. Although the fiber is completely modified, the pore defects result in low tensile strength. In Comparative Example 3, the fiber retains enol grafting and has some bonding force with the matrix, which can bear part of the tensile force. Therefore, the tensile strength is higher than that of Comparative Examples 1-2.

[0198] While embodiments of the application have been shown and described, it is to be understood that the embodiments described are merely exemplary and that changes can be made in the embodiments without departing from the spirit and scope of the application.

[0199] The above description of the application and its embodiments is not restrictive, and the embodiments shown in the drawings are only one of the embodiments of the application, and the actual application is not limited thereto. In general, if a person skilled in the art is inspired by it, without departing from the purpose of the application, without creative design, similar ways and embodiments of the technical solution should belong to the protection scope of the application.

Claims

1. An environmentally friendly lightweight porous concrete slab, characterized by: The lightweight porous concrete slab comprises the following components by weight: cement 30-40 parts, fly ash 20-30 parts, recycled aggregate 5-15 parts, lightweight aggregate 15-30 parts, modified fiber 0.5-1 part, water reducing agent 0.6-1.2 parts, carbonation-resistant additive 0.6-1.2 parts, pore-forming agent 0.8-1.5 parts, foam stabilizer 0.3-0.5 parts; the recycled aggregate comprises at least one of waste concrete recycled aggregate, waste ceramic recycled aggregate, waste brick recycled aggregate, and industrial tailings recycled aggregate; the lightweight aggregate comprises at least one of pumice, volcanic slag, expanded perlite, coal gangue ceramic, and expanded slag beads; the water reducing agent comprises at least one of polycarboxylic acid water reducing agent, naphthalene water reducing agent, and carbonyl pyruvic aldehyde water reducing agent; the carbonation-resistant additive comprises at least one of silane coupling agent KH-560 and silane coupling agent KH-550; The preparation method of the modified fiber specifically comprises the following steps: A1, take the enol compound and dissolve it in dry toluene, add a hydroxyl protecting agent, mix uniformly, and then introduce flowing nitrogen, transfer to an ice water bath, and perform a hydroxyl shielding reaction to obtain an enol protected monomer solution; A2, take the homopolymerized polypropylene powder, the enol protected monomer solution prepared in step A1, dicumyl peroxide, and anhydrous toluene, and add them to a high-speed mixer under a nitrogen atmosphere, and then perform stirring reaction at room temperature; after the reaction system is uniformly mixed, transfer to a twin-screw extruder to perform melt grafting reaction; the melt is extruded through a die head, pelletized, and then modified polypropylene particles are obtained; A3, take the modified polypropylene particles prepared in step A2, perform melt spinning, place in hydrochloric acid aqueous solution, increase the reaction temperature, perform stirring reaction, filter, collect the fibers, wash with deionized water until neutral, then place in EDTA solution, filter, collect the fibers, wash with deionized water, and vacuum dry to obtain modified polypropylene fibers; A4, take the modified polypropylene fibers prepared in step A3, soak in an ammonia water solution, take out, wash with deionized water until neutral, add to dopamine-Tris solution, stir at room temperature for 2-3 h, after the reaction is completed, filter, collect the fibers, wash with deionized water, and vacuum dry to obtain PDA-modified polypropylene fibers; A5, take the PDA-modified polypropylene fibers prepared in step A4, add to a copper nitrate aqueous solution, adjust the pH of the reaction system to 5.0-5.5, mix uniformly, dropwise add ammonium oxalate aqueous solution, increase the reaction temperature, and perform deposition reaction; after the reaction is completed, filter, collect the fibers, wash with deionized water until neutral, and vacuum dry to obtain modified fibers; The preparation method of the pore-forming agent specifically comprises the following steps: B1, take 3-aminophenol hydrochloride and dissolve it in deionized water, add sodium bicarbonate, continuously stir until no gas bubbles are generated, stand, vacuum filter, collect the solid, wash, and vacuum dry to obtain 3-aminophenol; B2, resorcinol is dissolved in anhydrous toluene, p-toluenesulfonic acid is added, mixed uniformly, then 3-aminophenol prepared in step B1 is added, mixed to obtain a uniform reaction system, the reaction temperature is increased to carry out reflux reaction, after the reaction is completed, cooling, ice water is added to the reaction system, stirring until the solid is completely precipitated, vacuum filtration, collecting the solid, washing, purification, vacuum drying, to obtain 3, 3'-dihydroxydiphenylamine; B3, 3, 3'-dihydroxydiphenylamine prepared in step B2 is dissolved in acetone, anhydrous K2CO3 is added, mixed uniformly, then bromine long-chain alkane is added dropwise, after the dropwise addition is completed, the reaction temperature is increased to carry out reflux reaction, after the reaction is completed, the heating is stopped, cooling, filtration, collecting the filtrate, removing excess solvent by distillation under reduced pressure, after purification, long-chain modified 3, 3'-dihydroxydiphenylamine is obtained; B4, long-chain modified 3, 3'-dihydroxydiphenylamine prepared in step B3 is dissolved in anhydrous DMF, anhydrous K2CO3 is added, mixed uniformly, then Br-PEG-OH is dissolved in DMF, and is added dropwise into the reaction system, after the dropwise addition is completed, the reaction temperature is increased to carry out substitution reaction, after the reaction is completed, cooling, vacuum filtration, collecting the filtrate, rotary evaporation concentration, adding anhydrous diethyl ether for sedimentation purification, vacuum filtration, collecting the precipitate, washing, drying, to obtain PEG modified intermediate; B5, PEG modified intermediate prepared in step B4 is dissolved in anhydrous toluene, p-toluenesulfonic acid is added, mixed uniformly, then maleic anhydride is added, stirring to form a uniform system, after flowing nitrogen is introduced, the reaction temperature is increased to carry out reflux reaction, after the reaction is completed, cooling, adding saturated sodium bicarbonate aqueous solution for repeated washing, collecting the organic phase, washing with deionized water, then the organic phase is dehydrated with anhydrous sodium sulfate, vacuum filtration to collect the filtrate, rotary evaporation concentration, after purification, esterification intermediate product is obtained; B6, the sodium bisulfite solution is dissolved in an aqueous ethanol solution, the esterification intermediate prepared in step B5 is added, the reaction temperature is raised to perform sulfonation, after the reaction is completed, the reaction is cooled, and deionized water is used to perform dialysis to remove unreacted SO3 - , vacuum concentration, and freeze-drying to obtain the pore-forming agent.

2. The environmentally friendly lightweight porous concrete slab according to claim 1, characterized in that: In step A1, the enol compound includes at least one of 4-penten-1-ol, 5-hexen-1-ol, 6-hepten-1-ol, 9-decen-1-ol, 10-undecen-1-ol, cis-5-octen-1-ol; in step A1, the hydroxyl protection agent includes at least one of trimethylaluminum, triethylaluminum, triisobutylaluminum; in step A1, the mass ratio between the enol compound and the hydroxyl protection agent is 1-2:1.2-3; in step A1, the stirring speed of the hydroxyl shielding reaction is 200-300 rpm, and the reaction time of the hydroxyl shielding reaction is 3-4 h.

3. The environmentally friendly lightweight porous concrete slab according to claim 2, characterized in that: In step A2, the weight ratio of the homopolypropylene powder, the enol protected monomer solution prepared in step A1, the dicumyl peroxide and the anhydrous toluene is: 100 parts of the homopolypropylene powder, 30-50 parts of the enol protected monomer solution prepared in step A1, 0.5-0.8 parts of the dicumyl peroxide and 5-10 parts of the anhydrous toluene; in step A2, the temperature parameters of the melt grafting reaction are set as follows: the feeding section: 135-145℃; the compression section: 145-155℃; the melt reaction section: 162-168℃; the homogenization section: 168-172℃. The head: 162-168℃; in step A2, the screw rotation speed of the melt grafting reaction is 85-115 rpm.

4. The environmentally friendly lightweight porous concrete slab according to claim 3, characterized in that: In step A3, the concentration of the hydrochloric acid aqueous solution is 0.2-0.5 mol / L; in step A3, the reaction temperature of the stirring reaction is 30-40℃, and the reaction time of the stirring reaction is 1-2 h; in step A4, the added mass of the dopamine is 6%-12% of the mass of the modified polypropylene fiber.

5. The environmentally friendly lightweight porous concrete slab according to claim 4, characterized in that: In step A5, the mass concentration of the copper nitrate aqueous solution is 0.15-0.3 mol / L, and the mass concentration of the ammonium oxalate aqueous solution is 0.15-0.3 mol / L; in step A5, the mass-volume ratio of the PDA-modified polypropylene fiber to the copper nitrate aqueous solution is 0.1-0.25 g / mL; in step A5, the mass-volume ratio of the PDA-modified polypropylene fiber to the ammonium oxalate aqueous solution is 0.1-0.25 g / mL.

6. The environmentally friendly lightweight porous concrete slab according to claim 5, characterized in that: In step B1, the mass ratio between the 3-aminophenol hydrochloride and sodium bicarbonate is 1.4-1.7:1; in step B1, the mass concentration of the 3-aminophenol hydrochloride in the deionized water is 0.14-0.17 g / mL; in step B2, the mass ratio between the resorcinol and 3-aminophenol is 1.0-1.2:1; in step B2, the added mass of the p-toluenesulfonic acid is 15%-16% of the mass of the resorcinol; in step B2, the reaction temperature of the reflux reaction is 120-130℃, and the reaction time of the reflux reaction is 4-6 h; in step B3, the mass-volume ratio between the 3,3'-dihydroxydiphenylamine and the brominated long-chain alkane is 0.78-0.96 g / mL; wherein the brominated long-chain alkane includes at least one of 1-bromooctane, 1-bromononane and 1-bromodecane; in step B3, the mass ratio between the 3,3'-dihydroxydiphenylamine and the anhydrous K2CO3 is 7-8.5:9.7-11.6; in step B3, the reaction temperature of the reflux reaction is 50-60℃, and the reaction time of the reflux reaction is 4-6 h.

7. The environmentally friendly lightweight porous concrete slab according to claim 6, characterized in that: In step B4, the mass ratio between the long-chain modified 3,3'-dihydroxydiphenylamine and Br-PEG-OH is 1.0-1.5:1.8-2.5; in step B4, the mass ratio between the long-chain modified 3,3'-dihydroxydiphenylamine and K2CO3 is 1.0-1.5:1.8-3.0; in step B4, the reaction temperature of the substitution reaction is 70-80°C, and the reaction time of the substitution reaction is 5-6h; in step B5, the added mass of p-toluenesulfonic acid is 2.5%-3.0% of the mass of the PEG modified intermediate; in step B5, the mass ratio between the PEG modified intermediate and maleic anhydride is 1.75-2.5:0.6-0.8; in step B5, the reaction temperature of the reflux reaction is 80-90°C, and the reaction time of the reflux reaction is 4-6h; in step B6, the mass ratio between the sodium bisulfite and the esterification intermediate is 0.65-0.85:1.7-2.5; in step B6, the reaction temperature of the sulfonation reaction is 65-75°C, and the reaction time of the sulfonation reaction is 3-4h.

8. A method for producing the environmentally friendly lightweight porous concrete slab according to any one of claims 1 to 7, characterized by: Specifically comprising the following steps: S1: raw material pretreatment: S11, fly ash treatment: put the fly ash into a 100-110°C drying oven, dry until the water content is ≤1%; then pass through an 80-mesh standard sieve to remove coarse particles and unburned carbon particles, to obtain pretreated fly ash for standby; S12, recycled aggregate treatment: take the waste aggregate, crush it with a jaw crusher, and then sieve it with a 5-10mm aperture sieve, repeatedly rinse it with clean water until there is no floating dust on the surface, and then dry it under ventilation until the water content is 3%-5%, for standby; S13, light aggregate treatment: select light aggregate, soak it in advance for 2h, then drain it, and until there is no clear water on the surface, for standby; S14, modified fiber pretreatment: cut the modified fiber into 6-12mm short fibers, dry mix it with the pretreated fly ash prepared in step S11 for 1min to achieve fiber pre-dispersion, to obtain pre-dispersed modified fiber for standby; S15, dilute the water reducing agent with mixing water to obtain a 10%-15% water solution, to obtain a water reducing agent diluent for standby; S16: take water according to a water-cement ratio of 0.4-0.45, of which 10%-15% is used to dilute the water reducing agent, and the rest is direct mixing water; S2, mixing and stirring in stages: S21, put the cement and pre-dispersed modified fiber into the stirrer, stir at a speed of 150-200r / min for 1-2min until the fiber is evenly distributed; S22, slowly add the water reducing agent diluent prepared in step S15 and the direct mixing water to the stirrer, add the pore-forming agent and foam stabilizer, and stir at a speed of 250-300r / min for 2-3min to form a cement slurry without lumps and uniform fluidity; S23, add the recycled aggregate and light aggregate, stir at a speed of 150-200r / min for 1-1.5min, then add the carbonation-resistant additive, and stir at a speed of 100-150r / min for 0.5-2min until all components are uniformly mixed; S3, pouring forming: slowly pour the stirred mixture into the mold, the pouring height is 5-10 mm higher than the upper edge of the mold, start the vibration table, according to 30-50 Hz low frequency vibration for 20-30 s, until the surface has no obvious bubbles and tends to be flat, use a scraper to remove the excess mixture on the upper edge of the mold, trim the surface to be flat, immediately cover the plastic film, and stand for 1-2 h; S4, segmented curing: S41, standard curing: move the mold covered with the film into the standard curing room, control the temperature at 20℃ and the relative humidity at ≥95%, standard curing for 7 d, check the film sealing property every day, and if the condensed water is insufficient, appropriately spray clean water; S42, natural curing: after standard curing for 7 d, demold the mold, transfer the board to a ventilated and light-avoiding place, cover with a wet cloth and spray water 2 times a day to keep the surface wet, the environmental temperature is not lower than 5℃, and natural curing for 21 d, to obtain the lightweight porous concrete board.

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