Ultra-high performance concrete and method for producing the same

Abstract

The application discloses the technical field of concrete, and discloses an ultrahigh-performance concrete and a preparation method thereof, raw materials of the concrete comprising: 600-850 parts of cement, 120-180 parts of fly ash, 200-250 parts of silica ash, 1000-1450 parts of aggregate, 180-225 parts of water, 7-12 parts of water reducing agent, 15-20 parts of acrylamide in-situ polymerization solution, 5-8.5 parts of PVC fiber and 9-12.5 parts of calcium carbonate whisker; in the scheme, waste incineration bottom slag and waste incineration fly ash are used to prepare aggregate, calcium carbonate whisker, acrylamide in-situ polymerization solution and PVC fiber for preparing the ultrahigh-performance concrete, the application proportion of waste incineration products in the ultrahigh-performance concrete is significantly increased, the cost of the ultrahigh-performance concrete is significantly reduced, and the concrete has excellent mechanical properties.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of concrete, in particular to an ultra-high performance concrete and a preparation method thereof. BACKGROUND

[0002] The ultra-high performance concrete is a new type of cement-based composite material with excellent mechanical properties, durability and other characteristics. However, the amount of cement used in the preparation process of the ultra-high performance concrete is 2-3 times that of ordinary concrete, which makes the ultra-high performance concrete have a high cost. The chemical elements of waste incineration waste mainly include Ca, Si, Al and Fe elements, which belong to the CaO-Al2O3-SiO2-Fe2O3 system, similar to the composition of the raw materials for producing cement. Therefore, in the prior art, the waste incineration waste is used as a raw material to prepare the ultra-high performance concrete, which not only effectively reduces the amount of cement and the production cost of the ultra-high performance concrete, but also significantly improves the resource utilization efficiency of the waste incineration waste.

[0003] The waste incineration waste generally includes waste incineration bottom slag and waste incineration fly ash. The prior art has disclosed technical solutions for preparing the ultra-high performance concrete using the waste incineration fly ash and the waste incineration bottom slag. For example, the green and environmentally friendly ultra-high performance concrete material and the preparation method thereof disclosed in the publication CN113443872A fix the heavy metals in the fly ash in the concrete through the hydration of cement and fly ash, and reduce the high water absorption rate of the fly ash through the water reducing agent, so that the fly ash can replace part of the cement to reduce the amount of cement, and the performance of the ultra-high performance concrete does not change significantly. For another example, the ultra-high performance concrete and the preparation method thereof disclosed in the publication CN116903330A use the fly ash and zeolite to produce calcined zeolite, use silica fume and polycarbonate activated silicon dioxide to coat the waste bottom slag, and then use the calcined zeolite and the waste bottom slag to prepare the ultra-high performance concrete. The alkali-silica gel generated by the waste incineration bottom slag and the concrete improves the internal humidity of the concrete, reduces the drying shrinkage of the concrete, and the calcined zeolite can absorb the cement hydration products, which can play an internal curing role. However, the existing technology has a low proportion of waste incineration in the ultra-high performance concrete, and the utilization efficiency of the waste incineration bottom slag is low. SUMMARY

[0004] In order to overcome the problem of low comprehensive utilization rate of the waste incineration in the ultra-high performance concrete under the condition of the prior art, the present application provides an ultra-high performance concrete and a preparation method thereof. In the present application, the waste incineration bottom slag and the waste incineration fly ash are used to prepare aggregates, calcium carbonate whiskers, in-situ polymerization solution of acrylamide and PVC fibers for preparing the ultra-high performance concrete, which significantly increases the application proportion of the waste incineration products in the ultra-high performance concrete, significantly reduces the cost of the ultra-high performance concrete, and the concrete has excellent mechanical properties.

[0005] The specific technical solution of this invention is as follows:

[0006] An ultra-high performance concrete comprises, by weight parts: 600-850 parts cement, 120-180 parts fly ash, 200-250 parts silica fume, 1000-1450 parts aggregate, 180-225 parts water, 7-12 parts water-reducing agent, 15-20 parts acrylamide in-situ polymerization solution, 5-8.5 parts PVC fiber, and 9-12.5 parts calcium carbonate whiskers.

[0007] Preferably, the aggregate is made by coating the bottom ash of waste incineration with detoxified fly ash, the detoxified fly ash is made by thermally desorbing dioxins from acid leaching filter residue, and the acid leaching filter residue is made by acid leaching and filtering fly ash to obtain filter residue.

[0008] Preferably, the particle size of the waste incineration bottom ash is 6.75–16 mm.

[0009] Preferably, the pH of the acid leaching treatment is 2 to 3.

[0010] Preferably, the calcium carbonate whiskers are made from crude brine and carbon dioxide. The crude brine is prepared by using an acid leaching solution obtained from fly ash through acid leaching and filtration as raw material, and then treating it to remove heavy metals and sulfides.

[0011] Preferably, the calcium carbonate whiskers are modified calcium carbonate whiskers, which are made by modifying calcium carbonate whiskers with sodium hydroxide and tetraethyl orthosilicate.

[0012] Preferably, the acrylamide in-situ polymerization solution is prepared using acrylamide, ammonium persulfate and N,N'-methylenebisacrylamide as raw materials.

[0013] The application provides an ultra-high performance concrete, which is made of fly ash acid leaching residue of incinerated garbage and garbage incineration bottom slag as raw materials, and calcium carbonate whiskers are made of acid leaching filtrate of garbage incineration fly ash as raw materials, and the garbage incineration waste includes garbage incineration bottom slag and fly ash, wherein the garbage bottom slag is a granular inert compactible material, contains siliceous compounds, calcareous compounds and anhydrite, has the same effect of volcanic ash activity and hydraulicity as lime and cement. The fly ash belongs to CaO-Al2O3-SiO2-Fe2O3 system, has the activity of volcanic ash, and the particle size of the fly ash is relatively small, and the fly ash is combined with the garbage bottom slag to prepare the aggregate, so that the low content of the fine material of the bottom slag characteristics is corrected, and the compactibility of the concrete is improved. In addition, acrylamide is added in the ultra-high performance concrete, which can produce a large amount of carboxyl under the alkaline environment of the cement base, and is bonded with the metal ions of the hydration product to form a firm skeleton network system, so that the mechanical properties of the concrete are changed. The addition of PVC fiber can reduce the porosity of the concrete, organize the expansion of cracks, improve the compactness of the concrete, and enhance the durability. The whisker material refers to a one-dimensional single crystal material with a certain length-diameter ratio and a certain cross-sectional area. The protective film on the surface of the whisker adsorbs the Ca 2+ To a certain extent, the cement hydration is delayed. With the growth of the curing age, the nucleation effect, filling effect and bridge crack resistance effect of the whisker are exerted. The large length-diameter ratio increases the contact area of the whisker and the ultra-high performance concrete matrix, and the interfacial adhesion between the two is stronger, so that more energy is consumed in the process of whisker pulling out, and the mechanical properties of the ultra-high performance concrete are enhanced in many aspects.

[0014] Moreover, the present application forms a micro-meso-macro multi-scale modification system for the ultra-high performance concrete by in-situ polymerization of acrylamide solution, PVC fibers and calcium carbonate whiskers; due to the in-situ polymerization of acrylamide, a complete and uniform polymer network is formed in the concrete matrix; the carboxyl groups generated after the hydrolysis of acrylamide form bridging chemical bonds with the hydration products; however, the in-situ polymerization of acrylamide has an inhibitory effect on the cement hydration, which reduces the strength of the concrete; however, the addition of PVA fibers and modified calcium carbonate whiskers can avoid this problem and enhance the mechanical properties of the concrete; firstly, the addition of fibers can prevent the expansion of concrete cracks; the addition of modified calcium carbonate whiskers and PVA fibers can not only bridge the micro-cracks distributed in the concrete and inhibit the development of these micro-cracks into macro-cracks, but also prevent the expansion of macro-cracks, thereby enhancing the performance of the concrete at different structural levels; secondly, the modified calcium carbonate whiskers and the polymer network formed by the in-situ polymerization of acrylamide form a physical adsorption of intermolecular forces and electrostatic forces; at the same time, the carboxyl groups generated after the hydrolysis of acrylamide can bond with the calcium ions on the crystal surface, thereby forming a chemical adsorption of chemical bonds; the above combined effects make the polymer network formed by the in-situ polymerization of acrylamide and the calcium carbonate whiskers tightly combined, thereby forming a tightly combined interface of whisker-polymer-cementitious material, which makes the whiskers tightly combined with the concrete and further improves the agglomeration of the whiskers, so that the reinforcing effect of the calcium carbonate whiskers is fully exerted; furthermore, the in-situ polymerization of acrylamide also forms a wrapping layer of polymer and hydration products on the surface of PVA, which greatly enhances the bonding strength and combination of the PVA fibers and the concrete matrix, so that the reinforcing effect of the fibers is also fully exerted, thereby enhancing the mechanical properties of the overall concrete.

[0015] A preparation method of the above-mentioned ultra-high performance concrete, comprising the following steps: uniformly mixing cement, fly ash and silica fume in a stirring device, then adding aggregate, water and water reducing agent and stirring again, adding calcium carbonate whiskers, PVC fibers and in-situ polymerization solution of acrylamide in batches during the stirring process, and finally vacuum mixing and discharging to prepare the ultra-high performance concrete.

[0016] As preferred, the preparation method of the aggregate comprises the following steps: preparing fly ash into slurry according to water-cement ratio of 2-2.5:1, adding pickling agent into the slurry for acid immersion treatment, filtering the acid immersion residue to obtain acid immersion residue, placing the acid immersion residue in a low-temperature pyrolysis desorption device for pyrolysis desorption dioxin treatment to prepare detoxified fly ash, preparing the detoxified fly ash into coating slurry according to water-cement ratio of 0.4-0.6:1, adding waste incineration bottom ash into the coating slurry for stirring and drying to prepare the aggregate, the pH of the acid immersion treatment is 2-3, the temperature of the pyrolysis desorption dioxin treatment is 450-550℃, and the time of the pyrolysis desorption dioxin treatment is 1-1.5h.

[0017] As preferred, the preparation method of the calcium carbonate whisker comprises the following steps: fly ash is made into slurry according to water-cement ratio of 2-2.5:1, then an acid pickling agent is added into the slurry for acid leaching treatment, the acid leaching treatment is followed by filtration to obtain an acid leaching filtrate, the pH of the acid leaching filtrate is adjusted to 9.5-10 using sodium hydroxide, then suction filtration is performed, 1.5-3 mmol / L sodium sulfide is then added into the filtrate to separate and obtain a crude salt water, carbon dioxide is pumped into the crude salt water until the solution is neutral, then filtration is performed to obtain a filter cake, the filter cake is added into a sodium hydroxide solution, and stirring is performed at 40-45℃ for 10-12 h for washing and drying to prepare the calcium carbonate whisker, the calcium carbonate whisker, 200-210 parts of anhydrous ethanol and 45-50 parts of deionized water are mixed, 2.5-3 parts of ammonia water is then added, stirring is performed for 1-2 h, 30-35 parts of tetraethyl orthosilicate is then added, and stirring is performed at 40-45℃ for 5-7 h, then washing and drying are performed to prepare the modified calcium carbonate whisker.

[0018] The application also provides a preparation method of the above-mentioned ultra-high performance concrete, wherein the incineration fly ash is subjected to acid leaching treatment, and the harmful chloride ions in the incineration fly ash are removed after the acid leaching treatment; the acid leaching residue and the acid leaching filtrate obtained after the acid leaching treatment are subjected to treatment respectively, the heavy metals in the acid leaching residue are removed after the pyrolysis desorption and dioxin detoxification, the peak value of calcium carbonate in the detoxified fly ash is increased, calcium oxide and silicon dioxide form calcium silicate through solid phase reaction and siliconization reaction in a high temperature environment, the activity of the pretreated fly ash is enhanced, and the particle size of the pretreated fly ash is fine, the fly ash is made into slurry and wrapped on the incineration bottom ash, can fill the surface pores and cracks of the incineration bottom ash, make the surface of the incineration bottom ash flat, form a high-strength matrix protection layer, and make the structure of the wrapped incineration bottom ash more compact; the treated incineration fly ash can react with the incineration bottom ash to produce C-S-H crystals, which are completely hydrated and have good adhesion with the surface of the incineration bottom ash; the hydration products of the pretreated fly ash slurry can produce numerous micro voids and agglomerated hydration products, which can significantly improve the water absorption of the aggregate after being wrapped on the surface of the incineration bottom ash; in addition, due to the use of rapid drying in the wrapping operation, irregular crystal structures and internal bubbles of the pretreated fly ash slurry are generated, the molecular activity is more intense, more gas bubbles are generated, and the gas bubbles can quickly move away from the incineration bottom ash, but the wrapping layer is thin, the gas can quickly escape from the wrapping layer, no water film is formed around the incineration bottom ash, the cement hydration products do not produce large bubbles or even large cracks caused by air layer, and the mechanical properties of the concrete are improved.

[0019] The method further uses the acid leaching filtrate obtained after the waste incineration fly ash is treated by acid leaching as a raw material to prepare calcium carbonate whiskers, uses sodium hydroxide to pretreat the surface of the calcium carbonate whiskers, increases the number of hydroxyl groups on the surface of the whiskers, then uses tetraethyl orthosilicate to modify the surface of the whiskers, and enhances the bonding performance between the calcium carbonate whiskers and the cement-based interface. The surface of the modified calcium carbonate whiskers is rough, and silica generated by the hydrolysis of the tetraethyl orthosilicate is attached to the surface. The silica can participate in the hydration reaction of the cement, increase the hydration products around the calcium carbonate whiskers, and improve the compactness of the cement matrix. When a crack propagates to the surface of the whiskers, more energy is consumed to overcome the friction between the whiskers and the cement matrix, thereby improving the toughness of the ultra-high performance concrete.

[0020] Compared with the prior art, the application has the following technical effects:

[0021] The fly ash after detoxification and the waste incineration bottom ash are used as the aggregate of the concrete, which not only reasonably utilizes resources and reduces the burden of environmental disposal, but also makes the fly ash after detoxification smaller in particle size and stronger in activity through acid leaching and pyrolysis desorption modification, fills the pores and cracks on the surface of the waste incineration bottom ash after forming a slurry, makes the surface of the waste incineration bottom ash smooth, forms a high-strength matrix protection layer to make the structure more compact, enhances the compressive resistance of the aggregate, and thus improves the mechanical properties of the concrete.

[0022] The calcium carbonate whiskers used in the application are prepared from the fly ash during detoxification, which has the effect of treating waste with waste and saves costs.

[0023] The modified calcium carbonate whiskers, PVC fibers and acrylamide in-situ polymerization solution are used to modify the cement-based material, acrylamide is used as a micro-scale modification material to form a complete and uniform polymer network and simultaneously form a bonding effect with the hydration products, greatly improving the microstructure and performance of the cement-based material; the silica attached to the surface of the modified calcium carbonate whiskers can increase the hydration products around the whiskers, and as a mesoscale modification material, the filling effect makes the structure of the cement-based material more compact, and simultaneously inhibits the generation and propagation of microcracks to improve the mechanical strength and toughness of the cement-based material; the PVC fibers are used as a macro-scale modification material to bear the load, inhibit cracks and improve the mechanical properties of the cement-based material; and the three materials have a positive synergistic effect, forming a micro-mesoscopic-macro multi-scale synergistic modification to comprehensively improve the mechanical properties of the concrete. DETAILED DESCRIPTION

[0024] The application will be further described below in combination with examples.

[0025] Example 1:

[0026] An ultra-high performance concrete comprises, by mass fraction: cement 850 parts, fly ash 180 parts, silica fume 240 parts, aggregate 1400 parts, water 210 parts, water reducing agent 12 parts, acrylamide in-situ polymerization solution 20 parts, PVC fiber 8.5 parts, calcium carbonate whisker 12.5 parts; the cement is P042.5 Portland cement, the fly ash meets the requirements of II fly ash in GB / T1596-2017, the silica fume meets the performance index of SF95 grade in GB / T27690-2023; the water reducing agent is a polycarboxylic acid high-performance water reducing agent (solid content 20%, water reducing rate 30%); the modified calcium carbonate whisker is 0.5 mm in length and 20 mm in length, the PVC strength is 1600 MPa·S, and the acrylamide in-situ polymerization solution is prepared from acrylamide, ammonium persulfate and N,N'-methylene bisacrylamide.

[0027] A preparation method of an ultra-high performance concrete comprises the following steps:

[0028] Fly ash pretreatment: fly ash is made into fly ash slurry at a solid-liquid ratio of 1:2, and then hydrochloric acid is used for acid leaching treatment of the fly ash, the pH of the fly ash slurry is adjusted to 2 by using 31% hydrochloric acid, and after acid leaching treatment, solid-liquid separation is performed to obtain acid leaching residue and acid leaching filtrate;

[0029] Preparation of aggregate: the acid leaching residue is introduced into a rotary kiln, and after pyrolysis and desorption at 550 DEG C for 2 h, dioxin detoxification fly ash is obtained, the dioxin detoxification fly ash is made into a coating slurry at a water-cement ratio of 0.4, the incineration garbage bottom ash (particle size of 6.75-9.5 mm) is immersed in the coating slurry for coating treatment to form a coated material, and then the coated material is placed in a drying oven at 105 DEG C for drying to form the aggregate;

[0030] Preparation of calcium carbonate whisker: the pH of the acid leaching filtrate is adjusted to 10 by using sodium hydroxide, then heavy metal solids are removed by standing and suction filtration, and the filtrate is collected, 3 mmol / L sodium sulfide is added to the filtrate, and then the sulfide precipitate is removed by suction filtration to obtain a crude salt water, carbon dioxide is pumped into the crude salt water until the crude salt water is neutral, and then solid-liquid separation is performed to obtain a filtrate and a filter cake, the filter cake is added to a sodium hydroxide solution (6 kg of sodium hydroxide and 250 kg of water) and stirred at 45 DEG C for 12 h, and then washed and dried to obtain the calcium carbonate whisker;

[0031] Preparation of ultra-high performance concrete: cement, fly ash and silica fume are injected into a stirring device and uniformly mixed, then the above-mentioned aggregate, water and water reducing agent are added and continuously stirred, the modified calcium carbonate whisker, PVC fiber and acrylamide in-situ polymerization solution are added in three times during the stirring process, and finally the ultra-high performance concrete is obtained after vacuum mixing for 4 min and discharging.

[0032] Example 2:

[0033] An ultra-high performance concrete comprises, by mass fraction: cement 720 parts, fly ash 150 parts, silica fume 220 parts, aggregate 1350 parts, water 195 parts, water reducing agent 9 parts, acrylamide in-situ polymerization solution 18 parts, PVC fiber 7 parts, calcium carbonate whisker 10 parts; the cement is P042.5 Portland cement, the fly ash meets the physical and chemical performance requirements of II-grade fly ash in GB / T1596-2017, and the silica fume meets the performance index of SF95-grade silica fume for mortar and concrete in GB / T27690-2023; the water reducing agent is a polycarboxylic acid high-performance water reducing agent (solid content 20%, water reducing rate 30%); the modified calcium carbonate whisker is 0.8 mm in length and 25 mm in length, the PVC strength is 1600 MPa·S, and the acrylamide in-situ polymerization solution is prepared from acrylamide, ammonium persulfate and N,N'-methylene bisacrylamide as raw materials.

[0034] A preparation method of an ultra-high performance concrete comprises the following steps:

[0035] Fly ash pretreatment: fly ash is prepared into fly ash slurry at a solid-liquid ratio of 1:2, and solid-liquid separation is performed to obtain filter residue and filtrate;

[0036] Preparation of aggregate: the filter residue is introduced into a rotary kiln, and dioxin detoxification fly ash is obtained after pyrolysis and desorption at 500 DEG C for 1.5 h, the dioxin detoxification fly ash is prepared into a coating slurry at a water-cement ratio of 0.5, the incineration garbage bottom slag (particle size 9.5-12 mm) is immersed in the coating slurry for coating treatment to prepare a coated object, and the coated object is placed in a drying oven at 105 DEG C for drying to prepare the aggregate;

[0037] Preparation of calcium carbonate whisker: the pH of the filtrate is adjusted to 10 by using sodium hydroxide, then heavy metal solids are removed by standing and suction filtration, and the filtrate is collected, 3 mmol / L sodium sulfide is added to the filtrate, and the sulfide precipitate is removed by suction filtration to obtain a crude salt water, carbon dioxide is pumped into the crude salt water until the crude salt water is neutral, and solid-liquid separation is performed to obtain filtrate and filter cake, the filter cake is added to a sodium hydroxide solution (6 kg of sodium hydroxide and 250 kg of water) and stirred at 45 DEG C for 12 h, and after washing and drying, the calcium carbonate whisker is obtained;

[0038] Preparation of ultra-high performance concrete: the cement, fly ash and silica fume are injected into a stirring device and uniformly mixed, then the above-mentioned aggregate, water and water reducing agent are added and continuously stirred, the modified calcium carbonate whisker, PVC fiber and acrylamide in-situ polymerization solution are added three times during the stirring process, and finally the ultra-high performance concrete is prepared by vacuum mixing for 4 min and discharging.

[0039] Example 3:

[0040] An ultra-high performance concrete comprises, by mass fraction: cement 650 parts, fly ash 120 parts, silica fume 200 parts, aggregate 1200 parts, water 185 parts, water reducing agent 8 parts, acrylamide in-situ polymerization solution 16 parts, PVC fiber 6 parts, calcium carbonate whisker 9 parts; the cement is P042.5 Portland cement, the fly ash meets the requirements of II grade fly ash in GB / T1596-2017, and the silica fume meets the performance index of SF95 grade silica fume for mortar and concrete in GB / T27690-2023; the water reducing agent is a polycarboxylic acid high-performance water reducing agent (solid content 20%, water reducing rate 30%); the modified calcium carbonate whisker is 0.5 mm in length and 20 mm in length, the PVC strength is 1600 MPa·S, and the acrylamide in-situ polymerization solution is prepared from acrylamide, ammonium persulfate and N,N'-methylene bisacrylamide.

[0041] A preparation method of an ultra-high performance concrete comprises the following steps:

[0042] Fly ash pretreatment: fly ash is made into fly ash slurry at a solid-liquid ratio of 1:2, and then the fly ash is subjected to acid leaching treatment using hydrochloric acid; the acid leaching treatment uses hydrochloric acid with a mass fraction of 31% to adjust the pH of the fly ash slurry to 2; after the acid leaching treatment, solid-liquid separation is performed to obtain acid leaching residue and acid leaching filtrate;

[0043] Preparation of aggregate: the acid leaching residue is introduced into a rotary kiln, pyrolysis and desorption are performed at 550°C for 2h to obtain dioxin detoxification fly ash, the dioxin detoxification fly ash is made into a coating slurry at a water-cement ratio of 0.4, the incineration garbage bottom ash (particle size of 6.75-9.5mm) is immersed in the coating slurry for coating treatment to form a coated object, and the coated object is placed in a drying oven at 105°C for drying to form the aggregate;

[0044] Preparation of calcium carbonate whisker: the pH of the acid leaching filtrate is adjusted to 10 using sodium hydroxide, then heavy metal solids are removed by standing and filtration to collect the filtrate, 3mmol / L sodium sulfide is added to the filtrate, and the sulfide precipitate is removed by filtration to obtain a crude salt water, carbon dioxide is pumped into the crude salt water until the crude salt water is neutral, and then solid-liquid separation is performed to obtain a filtrate and a filter cake, the filter cake is added to a sodium hydroxide solution (6kg of sodium hydroxide and 250kg of water) and stirred at 45°C for 12h, and then washed and dried to obtain the calcium carbonate whisker;

[0045] Preparation of ultra-high performance concrete: cement, fly ash and silica fume are injected into a stirring device and uniformly mixed, then the above-mentioned aggregate, water and water reducing agent are added and continuously stirred, the modified calcium carbonate whisker, PVC fiber and acrylamide in-situ polymerization solution are added in three times during the stirring process, and finally the ultra-high performance concrete is obtained after vacuum mixing for 6min and discharging.

[0046] Example 4:

[0047] An ultra-high performance concrete comprises, by mass fraction: cement 850 parts, fly ash 180 parts, silica fume 240 parts, aggregate 1400 parts, water 210 parts, water reducing agent 12 parts, acrylamide in-situ polymerization solution 20 parts, PVC fiber 8.5 parts, calcium carbonate whisker 12.5 parts; the cement is P042.5 Portland cement, the fly ash meets the physical and chemical performance requirements of II-grade fly ash in GB / T1596-2017, and the silica fume meets the performance index of SF95-grade silica fume for mortar and concrete in GB / T27690-2023; the water reducing agent is a polycarboxylic acid high-performance water reducing agent (solid content 20%, water reducing rate 30%); the modified calcium carbonate whisker is 0.5 mm in length and 20 mm in length, the PVC strength is 1600 MPa·S, and the acrylamide in-situ polymerization solution is prepared from acrylamide, ammonium persulfate and N,N'-methylene bisacrylamide as raw materials.

[0048] A preparation method of an ultra-high performance concrete comprises the following steps:

[0049] Fly ash pretreatment: fly ash is made into fly ash slurry at a solid-liquid ratio of 1:2, and then the fly ash is subjected to acid leaching treatment using hydrochloric acid; the acid leaching treatment uses hydrochloric acid with a mass fraction of 31% to adjust the pH of the fly ash slurry to 2; after the acid leaching treatment, solid-liquid separation is performed to obtain acid leaching residue and acid leaching filtrate;

[0050] Preparation of aggregate: the acid leaching residue is introduced into a rotary kiln, pyrolysis and desorption are performed at 500 DEG C for 2 hours to obtain dioxin detoxification fly ash, the dioxin detoxification fly ash is made into a coating slurry at a water-cement ratio of 0.6, the incineration garbage bottom ash (particle size 9.5-12 mm) is immersed in the coating slurry for coating treatment to form a coated object, and the coated object is naturally dried to form the aggregate;

[0051] Preparation of calcium carbonate whisker: the pH of the acid leaching filtrate is adjusted to 10 using sodium hydroxide, then heavy metal solids are removed by standing and filtration to collect the filtrate, 3 mmol / L sodium sulfide is added to the filtrate, and the sulfide precipitate is removed by filtration to obtain a crude salt water, carbon dioxide is pumped into the crude salt water until the crude salt water is neutral, and then solid-liquid separation is performed to obtain a filtrate and a filter cake, the filter cake is added to a sodium hydroxide solution (6 kg of sodium hydroxide and 250 kg of water) and stirred at 45 DEG C for 12 hours, and then washed and dried to obtain the calcium carbonate whisker;

[0052] Preparation of ultra-high performance concrete: cement, fly ash and silica fume are injected into a stirring device and uniformly mixed, then the above-mentioned aggregate, water and water reducing agent are added and continuously stirred, the modified calcium carbonate whisker, PVC fiber and acrylamide in-situ polymerization solution are added in three times during the stirring process, and finally the ultra-high performance concrete is obtained after vacuum mixing for 4 minutes and discharging.

[0053] Example 5:

[0054] An ultra-high performance concrete comprises, by mass fraction: cement 850 parts, fly ash 180 parts, silica fume 240 parts, aggregate 1400 parts, water 210 parts, water reducing agent 12 parts, acrylamide in-situ polymerization solution 20 parts, PVC fiber 8.5 parts, calcium carbonate whisker 12.5 parts; the cement is P042.5 Portland cement, the fly ash meets the physical and chemical performance requirements of II-grade fly ash in GB / T1596-2017, the silica fume meets the performance index of SF95-grade silica fume for mortar and concrete in GB / T27690-2023; the water reducing agent is a polycarboxylic acid high-performance water reducing agent (solid content 20%, water reducing rate 30%); the modified calcium carbonate whisker is 0.5 mm in length and 20 mm in length, the PVC strength is 1600 MPa·S, and the acrylamide in-situ polymerization solution is prepared from acrylamide, ammonium persulfate and N,N'-methylene bisacrylamide as raw materials.

[0055] A preparation method of an ultra-high performance concrete comprises the following steps:

[0056] Fly ash pretreatment: fly ash is made into fly ash slurry at a solid-liquid ratio of 1:2, and then hydrochloric acid is used for acid leaching treatment of the fly ash, the pH of the fly ash slurry is adjusted to 2 by using hydrochloric acid with a mass fraction of 31% for acid leaching treatment, and solid-liquid separation is performed after acid leaching treatment to obtain acid leaching residue and acid leaching filtrate;

[0057] Preparation of aggregate: garbage incineration bottom slag with a particle size of 9.5-16 mm is artificially selected as the aggregate;

[0058] Preparation of calcium carbonate whisker: the pH of the above-mentioned acid leaching filtrate is adjusted to 10 by using sodium hydroxide, then heavy metal solids are removed by standing and suction filtration, and the filtrate is collected, 3 mmol / L sodium sulfide is added to the filtrate, and the sulfide precipitate is removed by suction filtration to obtain crude brine, carbon dioxide is pumped into the crude brine until the crude brine is neutral, and solid-liquid separation is performed to obtain filtrate and filter cake, the filter cake is added to a sodium hydroxide solution (6 kg of sodium hydroxide and 250 kg of water) and stirred at 45°C for 12 h, and after washing and drying, calcium carbonate whisker is obtained;

[0059] Preparation of ultra-high performance concrete: cement, fly ash and silica fume are injected into a stirring device and uniformly mixed, then the above-mentioned aggregate, water and water reducing agent are added and continuously stirred, modified calcium carbonate whisker, PVC fiber and acrylamide in-situ polymerization solution are added three times during the stirring process, and finally the ultra-high performance concrete is obtained by vacuum mixing for 4 min and discharging.

[0060] Example 6:

[0061] An ultra-high performance concrete comprises, by mass fraction: cement 850 parts, fly ash 180 parts, silica fume 240 parts, aggregate 1400 parts, water 210 parts, water reducing agent 12 parts, acrylamide in-situ polymerization solution 20 parts, PVC fiber 8.5 parts, calcium carbonate whisker 12.5 parts; the cement is P042.5 Portland cement, the fly ash meets the physical and chemical performance requirements of II-grade fly ash in GB / T1596-2017, the silica fume meets the performance indicators of SF95-grade silica fume for mortar and concrete in GB / T27690-2023; the water reducing agent is a polycarboxylic acid high-performance water reducing agent (solid content 20%, water reducing rate 30%); the modified calcium carbonate whisker is 0.5 mm in length and 20 mm in length, the PVC strength is 1600 MPa·S, and the acrylamide in-situ polymerization solution is prepared from acrylamide, ammonium persulfate and N,N'-methylene bisacrylamide as raw materials.

[0062] A preparation method of an ultra-high performance concrete comprises the following steps:

[0063] Fly ash pretreatment: fly ash is made into fly ash slurry at a solid-liquid ratio of 1:2, and then the fly ash is subjected to acid leaching treatment using hydrochloric acid; the acid leaching treatment uses hydrochloric acid with a mass fraction of 31% to adjust the pH of the fly ash slurry to 2; after the acid leaching treatment, solid-liquid separation is performed to obtain acid leaching residue and acid leaching filtrate;

[0064] Preparation of aggregate: the acid leaching residue is introduced into a rotary kiln, pyrolysis and desorption are performed at 550 DEG C for 2 h to obtain dioxin detoxification fly ash, the dioxin detoxification fly ash is made into a coating slurry at a water-cement ratio of 0.4, the incineration garbage bottom ash (particle size of 6.75-9.5 mm) is immersed in the coating slurry for coating treatment to form a coated object, and the coated object is placed in a drying oven at 105 DEG C for drying to form the aggregate;

[0065] Preparation of calcium carbonate whisker: the pH of the acid leaching filtrate is adjusted to 9.5-10 using sodium hydroxide, then the heavy metal solids are removed by standing and suction filtration, and the filtrate is collected; 1.5-3 mmol / L sodium sulfide is added to the filtrate, and the sulfide precipitate is removed by suction filtration to obtain a crude salt water; carbon dioxide is pumped into the crude salt water until the crude salt water is neutral, and then solid-liquid separation is performed to obtain a filtrate and a filter cake; 26 kg of the filter cake is added to a sodium hydroxide solution (6 kg of sodium hydroxide and 250 kg of water) and stirred at 40-45 DEG C for 10-12 h; after washing and drying, the calcium carbonate whisker is obtained; the calcium carbonate whisker, 210 kg of anhydrous ethanol and 50 kg of deionized water are mixed, 2.9 kg of ammonia water is added and stirred for 1-2 h, then 33 kg of tetraethyl orthosilicate is added and stirred at 45 DEG C for 7 h, and after washing and drying, the modified calcium carbonate whisker is obtained.

[0066] Preparation of ultra-high performance concrete: cement, fly ash and silica ash are injected into a stirring device to mix evenly, then the above aggregate, water and water reducing agent are added and continue to stir, and the modified calcium carbonate whisker, PVC fiber and acrylamide in-situ polymerization solution are added three times during the stirring process, and finally the ultra-high performance concrete is obtained after vacuum mixing for 4 min.

[0067] Example 7:

[0068] An ultra-high performance concrete, comprising by mass fraction: cement 850 parts, fly ash 180 parts, silica ash 240 parts, aggregate 1400 parts, water 210 parts, water reducing agent 12 parts, acrylamide in-situ polymerization solution 20 parts, PVC fiber 8.5 parts, calcium carbonate whisker 12.5 parts; the cement is P042.5 Portland cement, the fly ash meets the physical and chemical performance requirements of II fly ash in GB / T1596-2017, and the silica ash meets the performance index of SF95 grade for mortar and concrete in GB / T27690-2023; the water reducing agent is a polycarboxylic acid high performance water reducing agent (solid content is 20%, water reducing rate is 30%); the modified calcium carbonate whisker is 0.5mm in length and 20mm in length, the PVC strength is 1600MPa·S, and the acrylamide in-situ polymerization solution is prepared from acrylamide, ammonium persulfate and N,N'-methylene bisacrylamide.

[0069] A preparation method of an ultra-high performance concrete, comprising the following steps:

[0070] Fly ash pretreatment: fly ash is made into fly ash slurry at a solid-liquid ratio of 1:2, and then the fly ash is subjected to acid leaching treatment using hydrochloric acid, and the pH of the fly ash slurry is adjusted to 2 using 31% mass fraction of hydrochloric acid, and the solid-liquid separation after acid leaching treatment obtains acid leaching residue and acid leaching filtrate;

[0071] Preparation of aggregate: the above acid leaching residue is introduced into a rotary kiln, and dioxin detoxification fly ash is obtained after pyrolysis and desorption at 550℃ for 2h, the dioxin detoxification fly ash is made into a coating slurry at a water-cement ratio of 0.4, the incineration garbage bottom ash (particle size is 6.75-9.5mm) is immersed in the coating slurry for coating treatment to prepare a coated material, and then the coated material is placed in a drying oven at 105℃ for drying to prepare the aggregate;

[0072] Preparation of calcium carbonate whisker: the pH of the above acid leaching filtrate is adjusted to 9.5-10 using sodium hydroxide, then heavy metal solids are removed by standing and suction filtration, and the filtrate is collected, 1.5-3 mmol / L sodium sulfide is added to the filtrate, and the sulfide precipitate is removed by suction filtration to obtain a crude brine, carbon dioxide is pumped into the crude brine until the crude brine is neutral, and solid-liquid separation is performed to obtain a filtrate and a filter cake, 30 kg of the filter cake, 210 kg of anhydrous ethanol, and 50 kg of deionized water are mixed, then 2.9 kg of ammonia water is added, stirring is performed for 1-2 h, then 33 kg of tetraethyl orthosilicate is added, stirring is performed at 45°C for 7 h, and after washing and drying, modified calcium carbonate whisker is obtained.

[0073] Preparation of ultra-high performance concrete: cement, fly ash, and silica ash are injected into a stirring device and mixed uniformly, then the above-mentioned aggregate, water, and water reducing agent are added and continue to be stirred, the modified calcium carbonate whisker, PVC fiber, and acrylamide in-situ polymerization solution are added in three portions during the stirring process, and finally, vacuum mixing is performed for 4 min before discharging to produce ultra-high performance concrete.

[0074] Comparative Example 1:

[0075] Compared with Example 1, no calcium carbonate whisker and acrylamide in-situ polymerization solution are added in Comparative Example 1.

[0076] Comparative Example 2:

[0077] Compared with Example 1, no PVC fiber and acrylamide in-situ polymerization solution are added in Comparative Example 2.

[0078] Comparative Example 3:

[0079] Compared with Example 1, no calcium carbonate whisker and PVC fiber are added in Comparative Example 3.

[0080] Comparative Example 4:

[0081] Compared with Example 1, no vacuum mixing and discharging are used in Comparative Example 4.

[0082] Test Example:

[0083] The performance of the ultra-high performance concrete prepared in Examples 1-7 and Comparative Examples 1-4 is tested, and the test items include the following indexes:

[0084] Flow performance: according to GB / T50080-2016, the ultra-high performance concrete slurry is evenly layered into a mini-slump cone with a lower diameter of 100 mm, an upper diameter of 50 mm, and a height of 150 mm, the upper opening of the slump cone is smoothed with a flat shovel, and then the slump cone is vertically lifted upwards, the vertical diameters of the slurry are measured when the slurry is no longer flowing, and then the average of the two diameters is taken as the flow parameter of the slurry;

[0085] Flexural strength: The flexural strength test was carried out according to GB / T 17671-1999 Cement-Determination of strength properties of hardening - mortar cubes (ISO method). The test procedure included that the test block for flexural strength test was a prism with the size of 40mm x 40mm x 160mm, and the loading rate of the instrument was 0.05kN / s. The data exceeding the average value ±10% in the test results were removed, and the average value was taken as the flexural strength of the test block;

[0086] Compressive strength: The compressive strength test was carried out on the side surface of the half prism. The loading rate of the instrument was 2.4kN / s. The data exceeding the average value ±10% in the test results were removed, and the average value was taken as the compressive strength of the test block;

[0087] The test results are shown in Table 1.

[0088] Table 1: Performance test results of ultra-high performance concrete

[0089]

[0090]

[0091] As shown in Table 1, in Example 1 and Example 2, the fly ash prepared by Preparation Example 2 was not subjected to acid immersion and high-temperature detoxification treatment, and contained a large amount of heavy metals, which invaded the intergranular layer during the C-S-H hydration and deposition process, and had low activity, so that the compressive strength and flexural strength were decreased.

[0092] In Example 1 and Example 3, the fly ash after detoxification and the bottom slag of waste incineration were mixed to prepare the aggregate. The fly ash slurry after detoxification could fill the pores of the bottom slag of waste incineration, so that the prepared aggregate was more dense, and the strength of the aggregate was greatly improved by filling and wrapping.

[0093] In Example 4, the aggregate was prepared by natural drying. The natural drying process was not as active as the rapid drying, so that the gas could not be quickly flushed out of the wrapping layer, and the water film was formed around the bottom slag of waste incineration, so that the cement hydrate produced large bubbles or even large cracks in the air layer, and the compressive strength and flexural strength were decreased.

[0094] In Example 5, the aggregate was not wrapped with detoxified fly ash slurry, but directly used the bottom slag of waste incineration as the aggregate. Since the surface of the bottom slag of waste incineration was rough, had many pores, the crystal joint was loose, and the crystal gap was large, the microstructure of the aggregate was porous, so that the mechanical properties of the prepared ultra-high performance concrete were poor.

[0095] Both example 6 and example 7 use modified calcium carbonate whiskers, and the compressive strength and the bending strength are increased, because the surface of the modified calcium carbonate whisker is attached with silica, and the silica participates in the hydration reaction, so that the hydration product around the calcium carbonate whisker is increased, the density of the cement matrix is improved, when the external force is applied, more energy is needed to overcome the friction between the interfaces, so that the mechanical properties are improved, in addition, compared with example 6, in example 7, sodium hydroxide is not added to pretreat the surface of the whisker during modification of the calcium carbonate whisker, and the compressive strength and the bending strength of example 7 are lower than those of example 6, which indicates that the use of sodium hydroxide for surface pretreatment can increase the number of hydroxyl groups on the surface of the whisker and enhance the bonding performance between the interfaces.

[0096] Compared with example 1, no calcium carbonate whisker and acrylamide are added in comparative example 1, no PVC fiber and acrylamide are added in comparative example 2, and no calcium carbonate whisker and PVC fiber are added in comparative example 3, the compressive strength of comparative examples 1-3 is poor, and the bending strength is general, the above results show that the addition of the three influences each other, the in-situ polymerization of acrylamide changes the surface structure of the calcium carbonate whisker and the PVA fiber, improves the bonding strength between the whisker, the fiber and the cement matrix, and the reinforcing effect of the whisker and the fiber is fully exerted. The in-situ polymerization of acrylamide, the calcium carbonate whisker and the PVA fiber play a role from different scales, and there is a positive mutual synergistic effect, forming a micro-mesoscopic-macro multi-scale modification mechanism, which greatly improves the comprehensive mechanical properties of the material.

[0097] The application provided in the application increases the application ratio of incineration waste products in the concrete, significantly improves the utilization rate of waste incineration products, significantly reduces the cost of the ultra-high performance concrete, and the mechanical properties of the ultra-high performance concrete prepared by the application are excellent, and meet the use standard of the ultra-high performance concrete.

[0098] The above is only a preferred embodiment of the application, and does not limit the application, any simple modification, change and equivalent transformation of the above embodiment according to the technical essence of the application still belong to the protection scope of the technical solution of the application.

Claims

1. An ultra-high performance concrete, characterized in that, The composition by weight is as follows: 600-850 parts cement, 120-180 parts fly ash, 200-250 parts silica fume, 1000-1450 parts aggregate, 180-225 parts water, 7-12 parts water-reducing agent, 15-20 parts acrylamide in-situ polymerization solution, 5-8.5 parts PVC fiber, and 9-12.5 parts calcium carbonate whiskers. The aggregate is made by coating the bottom ash of waste incineration with detoxified fly ash. The detoxified fly ash is made by thermally desorbing dioxins from acid leaching filter residue. The acid leaching filter residue is made by acid leaching and filtering fly ash to obtain filter residue. The calcium carbonate whiskers are modified calcium carbonate whiskers, which are made from calcium carbonate whiskers as raw materials by modification with sodium hydroxide and tetraethyl orthosilicate. The acrylamide in-situ polymerization solution is prepared from acrylamide, ammonium persulfate and N,N'-methylenebisacrylamide as raw materials.

2. The ultra-high performance concrete according to claim 1, characterized in that, The particle size of the waste incineration bottom ash is 6.75~16 mm.

3. The ultra-high performance concrete according to claim 1, characterized in that, The pH of the acid leaching treatment is 2-3.

4. The ultra-high performance concrete according to claim 1, characterized in that, The calcium carbonate whiskers are made from crude brine and carbon dioxide. The crude brine is prepared by using an acid leaching solution obtained from fly ash through acid leaching and filtration as raw material, and then treating it to remove heavy metals and sulfides.

5. A method for preparing ultra-high performance concrete according to any one of claims 1 to 4, characterized in that, Includes the following steps: Cement, fly ash, and silica fume are poured into a mixing device and mixed evenly. Then, aggregates, water, and water-reducing agents are added and mixed again. During the mixing process, calcium carbonate whiskers, PVC fibers, and acrylamide in-situ polymerization solution are added in batches. Finally, the mixture is vacuum-mixed and discharged to prepare ultra-high performance concrete.

6. The preparation method according to claim 5, characterized in that, The method for preparing the aggregate includes the following steps: fly ash is prepared into a slurry at a water-ash ratio of 2~2.5:1, then an acid pickling agent is added to the slurry for acid leaching treatment, and after acid leaching treatment, the slurry is filtered to obtain acid leaching residue. The acid leaching residue is placed in a low-temperature thermal desorption device for thermal desorption of dioxins to prepare detoxified fly ash. The detoxified fly ash is prepared into a coating slurry at a water-ash ratio of 0.4~0.6:

1. Waste incineration bottom ash is added to the coating slurry, stirred, dried, and used to support the aggregate. The pH of the acid leaching treatment is 2~3, the temperature of the thermal desorption of dioxins is 450~550 ℃, and the time of the thermal desorption of dioxins is 1~1.5 h.

7. The preparation method according to claim 5, characterized in that, The method for preparing the calcium carbonate whiskers includes the following steps: fly ash is prepared into a slurry at a water-ash ratio of 2-2.5:1, and then an acid pickling agent is added to the slurry for acid leaching treatment. After acid leaching treatment, the filtrate is obtained by filtration. The pH of the filtrate is adjusted to 9.5-10 using sodium hydroxide and then filtered. After filtration, 1.5-3 mmol / L sodium sulfide is added to the filtrate and the precipitate is separated to obtain crude brine. Carbon dioxide is pumped into the crude brine until the solution is neutral and then filtered to obtain a filter cake. The filter cake is added to a sodium hydroxide solution and stirred at a constant temperature of 40-45℃ for 10-12 hours. After washing and drying, calcium carbonate whiskers are obtained. Calcium carbonate whiskers, 200-210 parts of anhydrous ethanol and 45-50 parts of deionized water are mixed, and 2.5-3 parts of ammonia water are added. The mixture is stirred for 1-2 hours, and then 30-35 parts of tetraethyl orthosilicate are added. The mixture is stirred at 40-45℃ for 5-7 hours, and then washed and dried to obtain modified calcium carbonate whiskers.

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