Interface-enhanced granite concrete and preparation method thereof

Abstract

The invention discloses interface-enhanced granite concrete and a preparation method thereof, and belongs to the technical field of concrete. The granite concrete is prepared from the following components in parts by mass: 30 to 40 parts of cement, 40 to 50 parts of modified granite coarse aggregate, 50 to 60 parts of fine aggregate, 20 to 30 parts of mixed filler, 1 to 3 parts of low hydration heat polycarboxylate superplasticizer, 0.5 to 2 parts of shrinkage reducing agent and 10 to 30 parts of water. The granite is subjected to surface modification, and the novel low-hydration-heat polycarboxylate superplasticizer is adopted, so that the interface adhesion performance of granite aggregate and cement paste is remarkably improved, and the performances such as compressive strength and tensile strength of the granite concrete are greatly improved; therefore, the concrete has good application prospect and value in the technical field of concrete.

Description

Technical Field

[0001] The present invention belongs to the technical field of concrete, and particularly relates to an interface-reinforced granite concrete and a preparation method thereof. Background Art

[0002] With the rapid development of transportation infrastructure and the improvement of environmental protection awareness, high-quality non-renewable resources such as medium-alkali aggregates are becoming increasingly scarce. Acidic aggregates such as granite have the advantages of hard texture, wear resistance, anti-slip property, high mechanical strength, etc., and are rich in reserves and widely distributed. If granite is applied to the engineering construction of concrete, it can not only relieve the tense situation of the supply of medium-alkali stone resources, but also effectively reduce the project cost and drive the local economic development.

[0003] Aggregates with different lithologies have differences in strength, density, porosity, and water absorption. The difference between their elastic modulus and cement paste results in significantly different deformations under the action of the same stress, and relative displacement is likely to occur, leading to the appearance of microcracks or even dislocation damage in the interfacial transition zone, seriously reducing the mechanical properties of concrete. The tensile, flexural, and crack resistance properties of concrete mainly depend on the characteristics of the interfacial transition zone. The stronger the bonding effect of the interfacial transition zone, the higher the comprehensive mechanical properties of concrete. The complex interfacial behavior largely determines the mechanical response of granite concrete, and thus affects its service life and durability. Therefore, how to improve the interfacial adhesion performance between granite aggregates and cement paste and improve the performance of granite concrete has become an important problem to be solved urgently. Summary of the Invention

[0004] The present invention provides an interface-reinforced granite concrete, which comprises the following components in parts by mass:

[0005] Cement 30 - 40 parts, modified granite coarse aggregate 40 - 50 parts, fine aggregate 50 - 60 parts, mixed filler 20 - 30 parts, low heat of hydration polycarboxylate water reducer 1 - 3 parts, shrinkage reducing agent 0.5 - 2 parts, water 10 - 30 parts.

[0006] In the above granite concrete formula, the cement is Portland cement, specifically one or more of ordinary Portland cement, slag Portland cement, pozzolanic Portland cement, fly ash Portland cement, and composite Portland cement.

[0007] In the above granite concrete formula, the fine aggregate is composed of stone powder, polymer, and fine sand, and the mass ratio of the three is 2 - 4:1 - 5:3 - 5; the stone powder is selected from at least one of limestone powder, diabase powder, and dolomite powder; the polymer is selected from one or more of sodium polyacrylate, potassium polyacrylate, sodium polymethacrylate, and ammonium polyacrylate.

[0008] In the above granite concrete formulation, the mixed filler is a material with pozzolanic activity, specifically selected from at least two of desulfurized fly ash, fly ash, high-calcium fly ash, steel slag powder, iron tailings, mineral powder, limestone powder, and metakaolin, and the relative mass ratios of the pozzolanic materials are the same.

[0009] In the above granite concrete formulation, the shrinkage reducing agent is selected from at least one of polyoxyethylene ether, neopentyl glycol, trimethylolpropane, and pentaerythritol.

[0010] In the above granite concrete formulation, the modified granite coarse aggregate is prepared by the following method:

[0011] Mix the surface modifier with the buffer solution to obtain a surface modifier solution; then atomize the surface modifier solution and evenly spray it on the surface of the granite coarse aggregate; then carry out curing, and the modified granite coarse aggregate is obtained after the curing ends.

[0012] In the above method for preparing the modified granite coarse aggregate, the surface modifier is a compound containing an o-diphenol functional group, specifically selected from at least one of norepinephrine, tannic acid, dopamine, dopamine hydrochloride, hydroxytyramine, 2,3,4-trihydroxybenzaldehyde, 6-hydroxytyramine, gallate, gallic acid, gallate, methyl gallate, catechin, epicatechin, epigallocatechin, epicatechin gallate, and ellagic acid; the buffer solution includes at least one of acetic acid and sodium acetate buffer solution, disodium hydrogen phosphate and citric acid buffer solution, and disodium hydrogen phosphate and sodium dihydrogen phosphate buffer solution, and the concentration of the buffer solution is 0.05 - 0.2 mol / L, and the pH is 8 - 10.

[0013] In the above method for preparing the modified granite coarse aggregate, the concentration of the surface modifier in the surface modifier solution is selected from 0.5 - 3 g / L.

[0014] In the above method for preparing the modified granite coarse aggregate, the spraying amount of the surface modifier solution is: 10 - 40 kg of the surface modifier solution is sprayed per ton of granite coarse aggregate.

[0015] In the above method for preparing the modified granite coarse aggregate, the granite coarse aggregate is composed of granite with particle sizes of 5 - 10 mm, 10 - 20 mm, and 16 - 31.5 mm, and their mass ratio is 1:3:1.

[0016] In the above method for preparing the modified granite coarse aggregate, the curing conditions are selected from: curing at 20 - 60 °C for 24 - 72 h.

[0017] In the above granite concrete formulation, the low heat of hydration polycarboxylate water reducing agent is prepared by the following method:

[0018] Mix the esterification product, unsaturated boric acid, and macromonomer of ether, add water to dissolve them, and obtain a copolymer monomer mixture solution; then dropwise add an initiator solution, a molecular weight regulator, an ester monomer, and functional monomer A to the copolymer monomer mixture solution for reaction. After the reaction is completed, adjust the pH of the polymerization product to obtain a polycarboxylate superplasticizer with low heat of hydration.

[0019] In the above preparation method of the polycarboxylate superplasticizer with low heat of hydration, the components are selected from the following mass parts:

[0020] 1 - 4 parts of esterification product, 3 - 6 parts of unsaturated boric acid, 50 - 150 parts of macromonomer of ether, 0.3 - 4 parts of initiator solution, 0.2 - 3 parts of molecular weight regulator, 5 - 10 parts of ester monomer, 3 - 5 parts of functional monomer A, 25 - 90 parts of water.

[0021] In the above preparation method of the polycarboxylate superplasticizer with low heat of hydration, the unsaturated boric acid is selected from one or more of 4 - vinylphenylboronic acid (VBA), 2 - propeneboronic acid, potassium 4 - vinylphenylborate, and sodium 4 - vinylphenylborate; the macromonomer of ether is selected from at least one of isobutenol polyoxyethylene ether, isopentenol polyoxyethylene ether, vinyl polyethylene glycol ether, and ethenoxybutyl polyethylene glycol ether; the initiator is a water - soluble redox initiator system or a water - soluble azo initiator, and the water - soluble azo initiator is selected from azodiisobutylamidine hydrochloride and azodiisobimidazoline hydrochloride; in the water - soluble redox initiator system, the oxidant is selected from one of hydrogen peroxide, sodium persulfate, potassium persulfate, and ammonium persulfate, and the reductant is selected from one of sulfites, bisulfites, or thiosulfates; the concentration of the initiator solution is selected from 0.5% - 10%; the molecular weight regulator is selected from at least one of thioglycerol, 1 - mercapto - 1,1 - ethanediol, 2 - mercapto - 1,3 - propanediol, 2 - mercapto - 2 - methyl - 1,3 - propanediol, 2 - mercapto - 2 - ethyl - 1,3 - propanediol, 1 - mercapto - 2,3 - propanediol, 2 - mercaptoethyl - 2 - methyl - 1,3 - propanediol, and thioglycolic acid; the ester monomer is selected from at least one of 2 - methacryloyloxyethyl phosphate, 2 - methacryloyloxypropyl phosphate, acryloyloxyethyl phosphate, acryloyloxypropyl phosphate, and methyl methacrylate borate; the functional monomer A is selected from at least one of 2 - ethylhexyl acrylate, hexanediol diacrylate, tripropylene glycol diacrylate, dipropylene glycol diacrylate, trimethylolpropane triacrylate, neopentyl glycol diacrylate, isobornyl acrylate, ethoxyethoxyethyl acrylate, 2 - hydroxyethyl methacrylate, 2 - hydroxyethyl acrylate, 2 - hydroxypropyl methacrylate, 2 - hydroxypropyl acrylate, 2 - methacryloyloxyethyl phosphate, 2 - methacryloyloxypropyl phosphate, 2 - hydroxypropyl acrylate, triethylene glycol diacrylate, and triethylene glycol dimethacrylate.

[0022] In the above preparation method of the low heat of hydration polycarboxylate water reducer, the reaction conditions are selected from: the reaction temperature is 10 - 60°C, the dropping time lasts for 1 - 6 h, and after the dropping is completed, heat preservation reaction is carried out for 1 - 4 h.

[0023] In the above preparation method of the low heat of hydration polycarboxylate water reducer, the pH of the polymerization product is adjusted to 5 - 7.

[0024] In the above preparation method of the low heat of hydration polycarboxylate water reducer, the esterification product is prepared by the following method:

[0025] An unsaturated acid or unsaturated anhydride is added to an organic solvent, heated, and then a functional monomer B and a catalyst are added, and the temperature is raised for reaction to obtain an esterification product.

[0026] In the above preparation method of the esterification product, the components are selected from the following mass parts:

[0027] 30 - 40 parts of unsaturated acid or unsaturated anhydride, 30 - 40 parts of organic solvent, 30 - 40 parts of functional monomer B, 0.2 - 1 part of catalyst.

[0028] In the above preparation method of the esterification product, the unsaturated acid is selected from at least one of fumaric acid, cinnamic acid, glycidyl acrylate, fumaric acid, itaconic acid; the unsaturated anhydride is selected from at least one of phthalic anhydride, norbornene dicarboxylic anhydride, succinic anhydride, glutaric anhydride, itaconic anhydride, maleic anhydride, polyisobutylene succinic anhydride; the organic solvent is selected from at least one of n - hexane, cyclohexane, n - heptane; the functional monomer B is selected from at least one of isomannitol, sorbitol, maltitol, xylitol, isomaltulose, sorbitol, mannitol; the catalyst is selected from one of p - toluenesulfonic acid, methanesulfonic acid, sodium xylene sulfonate, p - toluenesulfonic anhydride, sodium p - toluenesulfonate.

[0029] In the above preparation method of the esterification product, the heating conditions are selected from: heating to 100 - 120°C; the temperature - raising reaction conditions are selected from: raising the temperature to 150 - 170°C and reacting for 0.5 - 1.5 h.

[0030] The present invention provides the above - mentioned preparation method of granite concrete, including the following steps:

[0031] The modified granite coarse aggregate and cement are mixed evenly, water is added for mixing, and then fine aggregate, mixed filler, low heat of hydration polycarboxylate water reducer and shrinkage - reducing agent are added and mixed evenly to obtain interface - enhanced granite concrete.

[0032] The present invention provides the application of the above - mentioned granite concrete in roads, bridges, airports, docks or water conservancy projects.

[0033] The beneficial effects of the present invention are as follows:

[0034] The present invention uses a surface modifier containing o-diphenol functional groups to functionally modify the surface of acidic coarse aggregates through self-polymerization adhesion characteristics. Its phenolic hydroxyl groups have a strong complexing ability with Ca 2+ and can adsorb and chelate free Ca in the nearby cement 2+ to promote the formation of hydration products. Due to the seeding effect of polyphenol-Ca 2+ , the polyphenol-Ca 2+ chelates can be in-situ deposited and aggregated between the coarse aggregate and the paste interface, filling the gaps in the interfacial transition zone, promoting the hydration reaction of cement at the coarse aggregate interface, significantly reducing the large pores and cracks at the coarse aggregate / paste interface, forming a dense microstructure, and better regulating the interfacial bonding strength between the coarse aggregate and the paste, thereby improving the compressive strength and durability of concrete.

[0035] The fine aggregates used in the present invention are composed of stone powder, polymer and fine sand. The polyacrylic acid polymer is prone to hydrolysis to generate polyacrylic acid polymer under alkaline conditions and can react with Ca 2+ , Fe 3+ , Al 3+ , Mg 2+ with relatively high concentrations generated by cement hydration to undergo cross-linking reactions. Among them, the high-valent metal ions form polar bonds (ionic bonds) and coordination bonds with the carboxyl groups of potassium polyacrylate through their polynuclear hydroxo-bridged complex ions to generate cross-linking, forming a cation-polymer interpenetrating network structure with stable structure, which can not only endow the fine aggregates with good stability, but also enhance the binding between the modified fine aggregates and the gel in concrete, thereby further enhancing the anti-cracking performance and compressive strength of concrete.

[0036] The water reducer provided by the present invention introduces three functional groups, namely ester group, phenyl group and boric acid group, through molecular structure design. When applied to cement-based materials, the ester group functional group undergoes a controllable hydrolysis reaction in the highly alkaline environment of the concrete pore solution. This process releases carboxylate ions with steric hindrance effects and hydroxy phenyl boric acid groups in stages, and is achieved through a dual action mechanism: on the one hand, the carboxylate disperses cement particles through electrostatic repulsion, and on the other hand, the boric acid group undergoes a reversible complexation reaction with the hydroxyl groups in the cement hydration products, effectively delaying the early hydration process of minerals such as tricalcium silicate. This synergistic effect not only reduces the hydration temperature peak of the system, but also delays the appearance time of the temperature peak by 10 - 11 hours, creating favorable conditions for heat conduction inside the concrete.

[0037] Through molecular design, the present invention uses a self-made esterification product to carry out a free radical copolymerization reaction with an unsaturated boronic acid derivative, successfully synthesizing a polycarboxylate superplasticizer functionalized with multi-boronic acid groups and polyhydroxy sugar alcohols. High-density boronic acid and hydroxyl groups are evenly distributed on the molecular chain of the obtained copolymer. Compared with traditional carboxylic acid groups, boronic acid groups exhibit more excellent coordination adsorption characteristics: on the one hand, the adsorption performance is enhanced: the binding energy between the boronic acid groups and the surface of cement particles is significantly increased, thus greatly improving the dispersion efficiency of the superplasticizer; at the same time, it has strong environmental adaptability, and the boronic acid groups have stronger tolerance to impurity ions (such as SO4 2- , Cl - etc.) in cement, enabling the concrete to maintain excellent workability under different aggregates and construction environments; in terms of regulating the heat of hydration: the boronic acid groups delay the hydration process of C3S by complexing Ca 2+ in the pore solution, significantly reducing the hydration heat release rate, thereby effectively inhibiting the early temperature cracks of high-strength concrete.

[0038] The present invention prepares an esterification product by esterifying polyhydroxy sugar alcohol with an unsaturated acid / anhydride, which has the advantages of low cost and simple operation. The prepared esterification product participates in the next copolymerization reaction, making the main chain of the polycarboxylate superplasticizer carry groups such as benzene rings, carboxylic acids, and hydroxyl groups. Introducing a rigid benzene ring into the main chain makes the main chain have a rigid and non-bendable structure, ensuring that the superplasticizer molecules are not easily buried by stone powder in manufactured sand, thereby improving the workability of the concrete; on the one hand, the polyhydroxy sugar alcohol groups react with the hydration products of cement to form insoluble metal salts (calcium salts), slowing down the hydration rate of cement, but not affecting the later hydration of cement; under the alkaline conditions of cement, the ester groups of the esterification product gradually hydrolyze over time, continuously releasing carboxylic acid groups that contribute to the water-reducing effect, thereby compensating for the lost water-reducing rate and achieving the effect of maintaining the slump.

[0039] In summary, the present invention improves the interfacial adhesion performance between granite aggregates and cement paste, improves the performance of granite concrete, and thus has good application prospects and value in the field of concrete technology. Description of the Drawings

[0040] Figure 1 is the linear expansion rate of different concrete samples;

[0041] Figure 2 is the chloride ion diffusion coefficient of different concrete samples. Detailed Embodiments

[0042] In the present invention, the granite coarse aggregate is composed of granite with particle sizes of 5 - 10 mm, 10 - 20 mm, and 16 - 31.5 mm respectively, and their mass ratio is 1:3:1.

[0043] Other materials used in the present invention can be obtained through commercial channels without special declaration. Other terms used in the present invention generally have the meanings commonly understood by those of ordinary skill in the art unless otherwise specified. The present invention will be described in further detail below with reference to specific embodiments and data. The following embodiments are only for illustrating the present invention and do not limit the scope of the present invention in any way.

[0044] Example 1

[0045] Prepare granite concrete according to the following steps:

[0046] Mix 40 kg of modified granite coarse aggregate and 30 kg of portland cement evenly, add 15 kg of water and mix evenly, then add 50 kg of fine aggregate, 10 kg of metakaolin, 10 kg of fly ash, 2 kg of low heat of hydration polycarboxylate superplasticizer and 1 kg of shrinkage reducing agent, and mix evenly to obtain granite concrete with enhanced interface.

[0047] The portland cement is ordinary portland cement with the model P.O42.5; the fine aggregate is composed of stone powder (limestone powder), potassium polyacrylate and fine sand, and the mass ratio of the three is 2:3:5; the shrinkage reducing agent is neopentyl glycol.

[0048] The modified granite coarse aggregate is granite coarse aggregate with catechin modified on its surface, and its preparation method is as follows:

[0049] Mix 0.5 g of catechin (surface modifier) with 1 L of acetic acid and sodium acetate buffer solution (0.1 mol / L) to obtain a surface modifier solution with a concentration of 0.5 g / L; atomize 1 kg of the surface modifier solution and spray it on the surface of 50 kg of granite coarse aggregate, then turn over and stir the coarse aggregate particles to ensure that the surface of the coarse aggregate particles is evenly coated with the surface modifier; spread out the coarse aggregate particles and keep the ambient temperature at 30 °C for 24 h. During the curing process, ensure the relative dispersion of the coarse aggregate particles by turning and stirring to obtain modified granite coarse aggregate with catechin modified on its surface.

[0050] The low heat of hydration polycarboxylate superplasticizer is prepared by the following method:

[0051] Add 30 g of glutaric anhydride to 30 g of cyclohexane, heat to 100 °C, then add 30 g of xylitol and 0.5 g of p-toluenesulfonic anhydride, raise the temperature to 150 °C, and react for 1 h to obtain an esterification product; mix 2 g of the esterification product, 3 g of potassium 4-vinylbenzeneborate, and 100 g of vinyl polyethylene glycol ether, and add 50 g of water to dissolve it to obtain a copolymer monomer mixture solution; dropwise add 1 g of an azodiisobutyramidine hydrochloride solution (mass concentration 3%), 0.5 g of thioglycolic acid, 5 g of acryloyloxyethyl phosphate, and 3 g of dipropylene glycol diacrylate to the copolymer monomer mixture solution for reaction. The reaction temperature is 30 °C, the dropping time is 3 h, and after dropping, keep warm for 2 h. Adjust the pH of the obtained polymerization product to 6 with sodium hydroxide solution to obtain a polycarboxylate superplasticizer with low heat of hydration.

[0052] Example 2

[0053] Prepare granite concrete, and the steps are as follows:

[0054] Mix 45 kg of modified granite coarse aggregate and 35 kg of portland cement evenly, add 20 kg of water and mix evenly, then add 55 kg of fine aggregate, 15 kg of mineral powder, 15 kg of high-calcium fly ash, 2 kg of polycarboxylate superplasticizer with low heat of hydration, and 1 kg of shrinkage-reducing agent, and mix evenly to obtain granite concrete with enhanced interface.

[0055] The portland cement is ordinary portland cement, with the model P.O42.5; the fine aggregate consists of stone powder (limestone powder), ammonium polyacrylate, and fine sand, and the mass ratio of the three is 3:4:3; the shrinkage-reducing agent is pentaerythritol.

[0056] The modified granite coarse aggregate is granite coarse aggregate surface-modified with hydroxydopamine, and its preparation method is as follows:

[0057] Mix 1.5 g of hydroxydopamine (surface modifier) with 1 L of acetic acid and sodium acetate buffer solution (0.1 mol / L) to obtain a surface modifier solution with a concentration of 1.5 g / L; atomize 1.5 kg of the surface modifier solution and spray it on the surface of 50 kg of granite coarse aggregate, then turn over and stir the coarse aggregate particles to ensure that the surface of the coarse aggregate particles is evenly coated with the surface modifier; spread out the coarse aggregate particles and keep the environmental temperature at 40 °C for 24 h of curing. During the curing process, ensure the relative dispersion of the coarse aggregate particles by turning and stirring to obtain modified granite coarse aggregate surface-modified with hydroxydopamine.

[0058] The polycarboxylate superplasticizer with low heat of hydration is prepared by the following method:

[0059] Add 40 g of cinnamic acid to 35 g of cyclohexane, heat to 110 °C, then add 40 g of mannitol and 0.6 g of sodium p-toluenesulfonate, raise the temperature to 160 °C, and react for 1.5 h to obtain an esterification product; mix 3 g of the esterification product, 4 g of 4-vinylphenylboronic acid sodium salt, and 100 g of isopentenyl alcohol polyoxyethylene ether, and add 70 g of water to dissolve it to obtain a copolymer monomer mixture solution; dropwise add 2 g of azodiisobutyramidine hydrochloride solution (mass concentration of 5%), 2 g of thioglycerol, 5 g of acryloyloxyethyl phosphate, and 4 g of trimethylolpropane triacrylate to the copolymer monomer mixture solution for reaction. The reaction temperature is 50 °C, the dropping time is 5 h, and after dropping, keep warm for 3 h. Adjust the pH of the obtained polymerization product to 7 with sodium hydroxide solution to obtain a polycarboxylate superplasticizer with low heat of hydration.

[0060] Example 3

[0061] Prepare granite concrete, the steps are as follows:

[0062] Mix 50 kg of modified granite coarse aggregate and 40 kg of portland cement evenly, add 21 kg of water and mix evenly, then add 60 kg of fine aggregate, 15 kg of mineral powder, 15 kg of desulfurized fly ash, 2 kg of polycarboxylate superplasticizer with low heat of hydration and 1 kg of shrinkage reducing agent, and mix evenly to obtain granite concrete with enhanced interface.

[0063] The portland cement is ordinary portland cement, with the model of P.O42.5; the fine aggregate consists of stone powder (limestone powder), sodium polymethacrylate and fine sand, and the mass ratio of the three is 3:2:5; the shrinkage reducing agent is pentaerythritol.

[0064] The modified granite coarse aggregate is granite coarse aggregate with epicatechin modified on the surface, and its preparation method is as follows:

[0065] Mix 3 g of epicatechin (surface modifier) with 1 L of disodium hydrogen phosphate and citric acid buffer solution (0.1 mol / L) to obtain a surface modifier solution with a concentration of 3 g / L; atomize 2 kg of the surface modifier solution and spray it on the surface of 50 kg of granite coarse aggregate, then turn over and stir the coarse aggregate particles to ensure that the surface of the coarse aggregate particles is evenly coated with the surface modifier; spread out the coarse aggregate particles and keep the environmental temperature at 50 °C for 48 h. During the curing process, ensure the relative dispersion of the coarse aggregate particles by turning and stirring to obtain modified granite coarse aggregate with epicatechin modified on the surface.

[0066] The polycarboxylate superplasticizer with low heat of hydration is prepared by the following method:

[0067] 40 g of phthalic anhydride was added to 40 g of cyclohexane, heated to 120 °C, then 40 g of isomaltitol and 0.7 g of methanesulfonic acid were added, the temperature was raised to 170 °C, and the reaction was carried out for 1.5 h to obtain an esterification product; 4 g of the esterification product, 6 g of potassium 4-vinylbenzeneborate, and 100 g of polyoxyethylene isobutenyl ether were mixed, and 80 g of water was added to dissolve them to obtain a copolymer monomer mixture solution; 3 g of an azobisisobutyramidine hydrochloride solution (mass concentration of 1%), 2 g of 1-mercapto-2,3-propanediol, 8 g of acryloyloxyethyl phosphate, and 5 g of trimethylolpropane triacrylate were respectively added dropwise to the copolymer monomer mixture solution for reaction, the reaction temperature was 60 °C, the dropping time was 5 h, and after dropping, it was kept warm for 4 h. The obtained polymerization product was adjusted to pH 7 with a sodium hydroxide solution to obtain a polycarboxylate superplasticizer with low heat of hydration.

[0068] Comparative Example 1

[0069] Compared with Example 1, the difference in this comparative example is only that the granite coarse aggregate was not surface-modified.

[0070] Comparative Example 2

[0071] Compared with Example 1, the difference in this comparative example is only that the superplasticizer used was a common commercially available polycarboxylate superplasticizer (Zhengzhou Kaidi Chemical Products Co., Ltd., water reduction rate 24%).

[0072] Comparative Example 3

[0073] Compared with Example 1, the difference in this comparative example is only that potassium polyacrylate was not added to the fine aggregate used, that is, the fine aggregate consisted of stone powder and fine sand, and the mass ratio of the two was 2:5.

[0074] I. Performance Test of Granite Concrete

[0075] 1. Compressive Strength and Tensile Strength

[0076] The granite concrete prepared in the above-mentioned examples was cured according to the specimen curing method in the Standard for Test Methods of Physical and Mechanical Properties of Concrete (GB / T 50081-2019), the curing age was 7 d, and the compressive strength and tensile strength performance tests were carried out on the cured concrete.

[0077] Both the compressive strength and the tensile strength were determined according to the Standard for Test Methods of Physical and Mechanical Properties of Concrete (GB / T 50081-2019).

[0078] The test results are shown in Table 1:

[0079] Table 1 Test Results of Concrete Compressive and Tensile Strengths

[0080] Group Compressive strength at 7 days (MPa) Compressive strength at 28 days (MPa) Tensile strength at 7 days (MPa) Tensile strength at 28 days (MPa) Example 1 44.3 54.5 12.1 17.3 Example 2 45.6 56.2 12.4 17.8 Example 3 46.8 57.1 12.8 18.1 Comparative Example 1 37.5 45.1 9.2 14.2 Comparative Example 2 39.5 48.3 10.1 14.6 Comparative Example 3 40.2 50.3 10.5 15.1

[0081] As can be seen from the data in Table 1, the concrete prepared by the present invention has good compressive strength, and the compressive strengths of the examples are all better than those of the comparative examples. Compared with Comparative Example 1, after the granite coarse aggregate in Example 1 was modified with epicatechin on the surface, its compressive strength was significantly higher than that of Comparative Example 1. The introduction of epicatechin-functionalized coarse aggregate significantly improved the compressive strength of the concrete. Compared with Comparative Example 1, its 7-day and 28-day compressive strengths increased by 15.3% and 17.2% respectively. This indicates that due to the introduction of phenolic hydroxyl groups, the functional coating endows the granite coarse aggregate with the ability to chelate Ca 2+ . In addition, this chelating ability is accelerated with the progress of the cement hydration reaction, resulting in the precipitation of polyphenol-Ca 2+ chelates at the coarse aggregate / paste interface. Due to the seeding effect of polyphenol-Ca 2+ , polyphenol-Ca 2+ chelates can be in-situ deposited and aggregated between the coarse aggregate and the paste interface, filling the gaps in the interfacial transition zone, promoting the hydration reaction of cement at the coarse aggregate interface, significantly reducing the large pores and cracks at the coarse aggregate / paste interface, forming a dense microstructure. These precipitated hydration products play a bonding role between the coarse aggregate and the paste, enhancing the denseness of the interfacial area and significantly improving the compressive strength of the concrete.

[0082] Meanwhile, compared with Comparative Example 1, the splitting tensile strength of the concrete in Example 1 was significantly improved. This is mainly because the splitting tensile strength of the concrete depends more on the bonding ability between the coarse aggregate and the cement paste. The surface modification has a very obvious improvement on the surface of the coarse aggregate. The chelates on the surface of the coarse aggregate not only repair the defects on the aggregate surface and optimize the aggregate shape, but also can effectively improve the bonding strength between the aggregate and the cement paste, optimizing the interfacial transition zone between the coarse aggregate and the cement paste. Therefore, after the surface of the coarse aggregate is modified and strengthened, the splitting tensile strength of the concrete is effectively improved.

[0083] Compared with Comparative Example 3, adding potassium polyacrylate to the fine aggregate in Example 1 can significantly improve its compressive strength and tensile strength. This is mainly because the cement paste is an alkaline-rich paste, and potassium polyacrylate is prone to hydrolysis to form polyacrylic acid polymers under alkaline conditions. In the initial stage of cement hydration, a relatively high concentration of Ca 2+ , Fe 3+ , Al 3+ , Mg 2+, the cations precipitated from the hydration of cement will come into contact with the hydrolyzed polyacrylic acid polymer and undergo a cross-linking reaction to form a cation-polymer structure with a stable structure. In addition, potassium polyacrylate accelerates the hydration of cement and promotes the cross-linking reaction between the metal ions precipitated from cement hydration and the polymer. Cement and potassium polyacrylate polymer each form a three-dimensional interpenetrating network structure, and these two networks rely on and penetrate each other to form a three-dimensional cross structure in space. Their mutual cross-linking enhances the stability of this interpenetrating network structure. Therefore, the compressive and tensile strengths of Example 1 are significantly improved compared to Comparative Example 3.

[0084] 2. Workability, bleeding rate and slump test of concrete

[0085] The slump of the fresh concrete mixture was tested according to the Standard Test Method for Properties of Ordinary Fresh Concrete Mixtures (GB / T 50080-2016).

[0086] Bleeding rate test: Add a certain amount of well-stirred foamed lightweight concrete slurry (m1) into the measuring cylinder, cover the cylinder lid and start timing. Before 60 minutes, suck out the water secreted at the top of the measuring cylinder with a straw every 10 minutes. After 60 minutes, measure it every 30 minutes until there is no bleeding on the surface. When testing, use gaskets of the same height to lift the measuring cylinder, and then weigh the mass of the remaining slurry (m2). The bleeding rate is (m1 - m2) / m0; where m0 is the total water consumption in the weighed filling slurry.

[0087] The test results are shown in Table 2:

[0088] Table 2 Test results of concrete performance

[0089] Number Workability Bleeding rate % Slump (mm) Example 1 Good 5.1 230 Example 2 Good 6.2 250 Example 3 Good 5.4 245 Comparative Example 1 Good 15.2 200 Comparative Example 2 Good 13.5 150 Comparative Example 3 Good 7.6 170

[0090] As can be seen from Table 2, the performances of the examples are all better than those of the comparative examples. Combining the results of Examples 1-3 and Comparative Example 2, it can be seen that compared with the existing water-reducing agents, the low heat of hydration polycarboxylate water-reducing agent provided by the present invention has better water-reducing and slump retention performances, good bleeding rate and workability. This is because the present invention uses polyhydric sugar alcohol to esterify with unsaturated acid / anhydride to prepare an esterification product, and the prepared esterification product participates in the next copolymerization reaction, so that the main chain of the polycarboxylate water-reducing agent has groups such as benzene ring, carboxylic acid, and hydroxyl group. Introducing a rigid benzene ring into the main chain makes the main chain have a rigid and non-bendable structure, ensuring that the water-reducing agent molecules are not easily buried by the stone powder in the manufactured sand, thereby improving the workability of concrete; on the one hand, the polyhydric sugar alcohol group reacts with the hydration products of cement to form insoluble metal salts (calcium salts), slowing down the hydration rate of cement, but not affecting the later hydration of cement; under the alkaline condition of cement, the ester group of the esterification product gradually hydrolyzes over time, continuously releasing carboxylic acid groups that contribute to the water-reducing effect, thereby compensating for the lost water-reducing rate and achieving the effect of maintaining the slump.

[0091] 3. Heat of hydration of cement and rate of reduction of heat of hydration

[0092] The heat of hydration of cement and the rate of reduction of heat of hydration were determined with reference to the "Method for Measuring Heat of Hydration of Cement (GB / T 12959--2008)". Meanwhile, the linear expansion rate was determined with reference to the standards of JC / T 603-2004 and JC / T 313-2009, and the chloride ion diffusion coefficient was determined with reference to the "Standard Test Method for Chloride Ion Penetration Resistance of Concrete (GB / T 50080-2016)".

[0093] The test results are shown in Table 3 Figure 1 and Figure 2 as follows:

[0094] Table 3 Comparison table of 3d heat of hydration of cement and rate of reduction of heat of hydration between the examples and comparative example 2

[0095] Number Hydration heat value at 3d (J / g) Reduction rate / % Tmax (h) Tmax (°C) Example 1 223.6 32.3 28 62 Example 2 232.1 29.7 27 63 Example 3 228.9 30.7 27 62 Comparative Example 2 330.5 -- 17 73

[0096] In the above Table 3, Tmax(h): the time corresponding to the highest temperature when the hydration heat release of the concrete paste reaches the maximum; Tmax(℃): the temperature corresponding to the highest temperature when the hydration heat release of the cement paste reaches the maximum.

[0097] From Figure 1 , Figure 2 and Table 3, it can be seen that the low heat of hydration type polycarboxylate water reducer of the present invention has unique molecular structure characteristics, and its molecular chain synergistically integrates ester group functional groups, aromatic phenyl structures and boric acid groups. When applied to the cement-based material system, under the action of the alkaline medium environment, the ester group structure undergoes cleavage through a controllable hydrolysis reaction, thereby releasing two key active components in stages: on the one hand, carboxylic acid groups with high-efficiency dispersion effects are generated, and on the other hand, a slow-release functional unit containing a hydroxy phenyl boric acid structure is formed. Among them, the carboxylic acid groups effectively improve the dispersibility of cement particles through the electrostatic repulsion effect, while the hydroxy phenyl boric acid unit regulates the hydration kinetics process of cement minerals through complexation. Compared with traditional carboxylic acid groups, boric acid groups exhibit more excellent coordination adsorption characteristics: on the one hand, the adsorption performance is enhanced: the binding energy between the boric acid groups and the surface of cement particles is significantly increased, thereby greatly improving the dispersion efficiency of the water reducer; at the same time, it has strong environmental adaptability, and the boric acid groups have stronger tolerance to impurity ions in cement (such as SO4 2- , Cl - etc.), enabling the concrete to maintain excellent workability under different aggregates and construction environments; in terms of regulating the heat of hydration: the boric acid groups complex with Ca in the pore solution 2+, delaying the hydration process of C3S and significantly reducing the hydration heat release rate, thus effectively inhibiting the early temperature cracks of high-strength concrete. This dual action mechanism not only significantly reduces the peak value of hydration heat release in the system (up to 15.1% reduction), but also extends the heat dissipation period by regulating the hydration heat release rate, delaying the appearance time of the temperature peak by 10 - 11 hours, creating favorable conditions for the internal heat conduction of concrete. Based on the principle of synergistic regulation of thermodynamics - kinetics, this water reducer can effectively inhibit the accumulation of early thermal stress in concrete, significantly reduce the incidence of structural cracks, and thus significantly improve the volume stability (28d shrinkage rate reduced by 38.1%) and durability index (chloride ion penetration coefficient decreased by 44.4%) of concrete structures. Experimental data show that the present invention realizes the organic unity of water reduction performance and hydration heat regulation through molecular design, providing an innovative solution for improving the crack resistance of high-strength concrete.

[0098] 4. Splitting tensile strength

[0099] In engineering construction, the problem in the application of granite concrete is whether there is good bonding performance between the cement paste and the granite body. The rock - cement paste binary interface is a traditional weak surface. The performance of concrete is affected not only by factors such as the strength, elastic modulus of aggregates and the performance of cement paste, but also by the structure of the interfacial transition zone between aggregates and cement paste. The structure of the interfacial transition zone between aggregates and cement paste is relatively loose and has low strength. Under the action of external factors, cracks are likely to appear, and the composition and morphology of the hydration products are different from those of the matrix. The mineral composition and surface structure of aggregates will affect the nucleation and growth of hydration products, especially calcium hydroxide (CH) and ettringite (AFt), thus affecting the microstructure of the interfacial transition zone and further affecting the mechanical properties of the interfacial transition zone.

[0100] The present invention studies the splitting tensile strength performance of granite aggregate concrete.

[0101] The splitting compressive test is used to characterize the interfacial bonding performance of ECC - reinforced concrete. Referring to the Standard Test Method for Physical and Mechanical Properties of Concrete GB / T 50081 - 2019, the loading rate of the universal testing machine is 0.04 MPa / s, and the calculation formula for splitting tensile strength is:

[0102] f st = 2F / πA

[0103] f st is the splitting tensile strength of the specimen, F is the load value of the testing machine, and A is the bonding area of the specimen.

[0104] The test results are shown in Table 4:

[0105] Table 4 Splitting tensile strength of Example 1 and Comparative Example 1

[0106] Group Splitting tensile strength (MPa) Example 1 3.2 Comparative Example 1 2.1

[0107] As can be seen from Table 4, compared with Comparative Example 1, the splitting tensile strength of the specimen in Example 1 increased by 52.3%. This is mainly because in the present invention, the granite coarse aggregate uses a surface modifier containing o-diphenol functional groups, and the surface of the acidic coarse aggregate is functionally modified through the self-polymerization adhesion characteristics. Its phenolic hydroxyl group has a strong complexing ability with Ca 2+ and can adsorb and chelate free Ca in the nearby cement 2+ , promoting the formation of hydration products. Due to the seeding effect of polyphenol-Ca 2+ , the polyphenol-Ca 2+ chelates can be in-situ deposited and aggregated between the coarse aggregate and the paste interface, filling the gaps in the interfacial transition zone, promoting the hydration reaction of cement at the coarse aggregate interface, significantly reducing the large pores and cracks at the coarse aggregate / paste interface, forming a dense microstructure, and better regulating the interfacial bonding strength between the coarse aggregate and the paste, thus improving the compressive strength and durability of the concrete.

[0108] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention in other forms. Any person skilled in the art may use the disclosed technical content to make changes or modifications into equivalent embodiments with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution content of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. An interface-enhanced granite concrete, characterized in that It comprises components in the following parts by mass: 30 - 40 parts of cement, 40 - 50 parts of modified granite coarse aggregate, 50 - 60 parts of fine aggregate, 20 - 30 parts of mixed filler, 1 - 3 parts of low heat of hydration polycarboxylate water reducer, 0.5 - 2 parts of shrinkage reducing agent, and 10 - 30 parts of water.

2. The granite concrete according to claim 1, characterized in that, The cement is Portland cement selected from one or more of ordinary Portland cement, slag Portland cement, pozzolanic Portland cement, fly ash Portland cement, and composite Portland cement; the fine aggregate is composed of stone powder, polymer, and fine sand, and the mass ratio of the three is 2 - 4:1 - 5:3 - 5; the stone powder is selected from at least one of limestone powder, diabase powder, and dolomite powder; the polymer is selected from one or several of sodium polyacrylate, potassium polyacrylate, sodium polymethacrylate, and ammonium polyacrylate; the mixed filler is at least two of desulfurized fly ash, fly ash, high calcium fly ash, steel slag powder, iron tailings, ore powder, limestone powder, and metakaolin; the shrinkage reducing agent is selected from at least one of polyethylene glycol ether, neopentyl glycol, trimethylolpropane, and pentaerythritol.

3. The granite concrete according to claim 1, wherein The modified granite coarse aggregate is prepared by the following method: Mix the surface modifier with the buffer solution to obtain a surface modifier solution; then atomize the surface modifier solution and evenly spray it on the surface of the granite coarse aggregate; then carry out curing, and after the curing is completed, the modified granite coarse aggregate is obtained.

4. The granite concrete according to claim 3, wherein The surface modifier is a compound containing an o-diphenol functional group, specifically selected from at least one of norepinephrine, tannic acid, dopamine, dopamine hydrochloride, hydroxydopamine, 2,3,4-trihydroxybenzaldehyde, 6-hydroxydopamine, gallate, gallic acid, gallate, methyl gallate, catechin, epicatechin, epigallocatechin, epicatechin gallate, and ellagic acid; the buffer solution includes at least one of acetic acid and sodium acetate buffer solution, disodium hydrogen phosphate and citric acid buffer solution, and disodium hydrogen phosphate and sodium dihydrogen phosphate buffer solution, the concentration of the buffer solution is 0.05 - 0.2 mol / L, and the pH is 8 - 10.

5. The granite concrete according to claim 1, wherein The low heat of hydration polycarboxylate water reducer is prepared by the following method: Mix the esterification product, unsaturated boric acid, and ether macromonomer, add water to dissolve it to obtain a copolymer monomer mixture solution; then dropwise add the initiator solution, molecular weight regulator, ester monomer, and functional monomer A to the copolymer monomer mixture solution for reaction, and after the reaction is completed, adjust the pH of the polymerization product to obtain the low heat of hydration polycarboxylate water reducer.

6. The granite concrete according to claim 5, wherein The components are selected from the following parts by mass: 1 - 4 parts of esterification product, 3 - 6 parts of unsaturated boric acid, 50 - 150 parts of ether macromonomer, 0.3 - 4 parts of initiator solution, 0.2 - 3 parts of molecular weight regulator, 5 - 10 parts of ester monomer, 3 - 5 parts of functional monomer A, and 25 - 90 parts of water; The unsaturated boric acid is selected from one or more of 4-vinylphenylboronic acid, 2-propeneboronic acid, potassium 4-vinylphenylborate, and sodium 4-vinylphenylborate; the ether macromonomer is selected from at least one of isobutenol polyoxyethylene ether, isopentenol polyoxyethylene ether, vinyl polyethylene glycol ether, and vinyloxybutyl polyethylene glycol ether; the initiator is a water-soluble redox initiator system or a water-soluble azo initiator, and the water-soluble azo initiator is selected from azobis(isobutylamidine) hydrochloride and azobis(2-methylimidazoline) hydrochloride; in the water-soluble redox initiator system, the oxidant is selected from one of hydrogen peroxide, sodium persulfate, potassium persulfate, and ammonium persulfate, and the reductant is selected from one of sulfites, bisulfites, or thiosulfates; the concentration of the initiator solution is selected from 0.5% - 10%; the molecular weight regulator is selected from at least one of thioglycerol, 1-mercapto-1,1-ethanediol, 2-mercapto-1,3-propanediol, 2-mercapto-2-methyl-1,3-propanediol, 2-mercapto-2-ethyl-1,3-propanediol, 1-mercapto-2,3-propanediol, 2-mercaptoethyl-2-methyl-1,3-propanediol, and thioglycolic acid; the ester monomer is selected from at least one of 2-methacryloyloxyethyl phosphate, 2-methacryloyloxypropyl phosphate, acryloyloxyethyl phosphate, acryloyloxypropyl phosphate, and methyl acrylate borate; the functional monomer A is selected from at least one of 2-ethylhexyl acrylate, hexanediol diacrylate, tripropylene glycol diacrylate, dipropylene glycol diacrylate, trimethylolpropane triacrylate, neopentyl glycol diacrylate, isobornyl acrylate, ethoxyethoxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl methacrylate, 2-hydroxypropyl acrylate, 2-methacryloyloxyethyl phosphate, 2-methacryloyloxypropyl phosphate, 2-hydroxypropyl acrylate, triethylene glycol diacrylate, and triethylene glycol dimethacrylate.

7. The granite concrete according to claim 5, characterized in that, The esterification product is prepared by the following method: Add the unsaturated acid or unsaturated anhydride to an organic solvent, heat it, then add the functional monomer B and a catalyst, and raise the temperature for reaction to obtain the esterification product.

8. The granite concrete according to claim 7, characterized in that, The amounts of each component are selected from the following mass parts: 30 - 40 parts of unsaturated acid or unsaturated anhydride, 30 - 40 parts of organic solvent, 30 - 40 parts of functional monomer B, and 0.2 - 1 part of catalyst; The unsaturated acid is selected from at least one of fumaric acid, cinnamic acid, glycidyl acrylate, fumaric acid, and itaconic acid; the unsaturated anhydride is selected from at least one of phthalic anhydride, norbornene dicarboxylic anhydride, succinic anhydride, glutaric anhydride, itaconic anhydride, maleic anhydride, and polyisobutylene succinic anhydride; the organic solvent is selected from at least one of n-hexane, cyclohexane, and n-heptane; the functional monomer B is selected from at least one of isomannitol, sorbitol, maltitol, xylitol, isomaltulose, sorbitol, and mannitol; the catalyst is selected from one of p-toluenesulfonic acid, methanesulfonic acid, sodium xylenesulfonate, p-toluenesulfonic anhydride, and sodium p-toluenesulfonate.

9. The granite concrete according to claim 1, characterized in that, The preparation method of the granite concrete comprises the following steps: Mix the modified granite coarse aggregate and cement evenly, add water and mix, then add fine aggregate, mixed filler, low heat of hydration polycarboxylate water reducer and shrinkage reducing agent, and mix evenly to obtain interface-reinforced granite concrete.

10. Application of the granite concrete according to any one of claims 1 to 9 in roads, bridges, airports, docks or water conservancy projects.

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