Additive for recycled aggregate concrete and preparation method thereof
阅读说明：本技术 一种再生骨料混凝土用外加剂及其制备方法 (Additive for recycled aggregate concrete and preparation method thereof ) 是由 王敏 张凯峰 孟刚 王军 罗作球 姚源 童小根 王佳敏 胡宇博 于 2021-01-26 设计创作，主要内容包括：本申请涉及混凝土外加剂领域,具体公开了一种再生骨料混凝土用外加剂及其制备方法,所述再生骨料混凝土用外加剂包括下列重量份的物质：30～50份氨基磺酸盐减水剂、20～30份聚羧酸减水剂、10～15份纳米二氧化硅溶胶和20～45份水；所述纳米二氧化硅溶胶包括等摩尔质量混合的亲水性实心二氧化硅溶胶和亲水性多孔二氧化硅溶胶。本申请在该外加剂中添加减水剂和纳米二氧化硅,先通过减水剂添加,提高混凝土保坍效果,再采用实心的纳米二氧化硅溶胶与多孔的纳米二氧化硅溶胶进行复合,作为再生骨料混凝土内部孔隙结构的填充料,提高混凝土结构的密实强度,降低水泥的水化程度,提高了再生骨料混凝土的和易性、流动性和密实性。(The application relates to the field of concrete admixtures, and particularly discloses an admixture for recycled aggregate concrete and a preparation method thereof, wherein the admixture for recycled aggregate concrete comprises the following substances in parts by weight: 30-50 parts of a sulfamate water reducing agent, 20-30 parts of a polycarboxylic acid water reducing agent, 10-15 parts of nano silica sol and 20-45 parts of water; the nano silica sol comprises hydrophilic solid silica sol and hydrophilic porous silica sol which are mixed by equimolar mass. This application adds water-reducing agent and nanometer silica in this admixture, adds through the water-reducing agent earlier, improves concrete slump loss effect, adopts solid nanometer silica sol and porous nanometer silica sol to compound again, as the filler of the inside pore structure of regeneration aggregate concrete, improves the closely knit intensity of concrete structure, reduces the hydration degree of cement, has improved the workability, mobility and the compactedness of regeneration aggregate concrete.)
1. The admixture for the recycled aggregate concrete is characterized by comprising the following components in parts by weight:
30-50 parts of a sulfamate water reducing agent;
20-30 parts of a polycarboxylic acid water reducing agent;
10-15 parts of nano silica sol;
20-45 parts of water; the nano silica sol comprises hydrophilic solid silica sol and hydrophilic porous silica sol which are mixed by equimolar mass.
2. The admixture for recycled aggregate concrete according to claim 1, wherein the surfaces of the particles of the hydrophilic porous silica sol are filled and coated with an oxygen scavenger, and the mass of the oxygen scavenger filling and coating is 35-40% of the mass of the hydrophilic porous silica sol.
3. The admixture for recycled aggregate concrete according to claim 2, wherein the oxygen scavenger comprises the following substances in parts by weight:
30-45 parts of polyvinylpyrrolidone;
15-25 parts of sodium erythorbate;
15-25 parts of sodium hexametaphosphate.
4. The admixture for recycled aggregate concrete according to claim 3, wherein the oxygen scavenger further comprises the following components in parts by weight: 8-15 parts of D-sodium gluconate and 3-5 parts of zinc sulfate.
5. The admixture for recycled aggregate concrete according to claim 1, wherein the hydrophilic porous silica sol is prepared by the following method:
(1) according to the mass ratio of 1: 10-15, mixing silicon dioxide and a polyvinyl alcohol solution, placing the mixture in an oil bath at the temperature of 100-110 ℃ for heating treatment, and standing and cooling the mixture to room temperature to obtain a mixed solution;
(2) according to the mass ratio of 1: 20-25, dropwise adding a sodium hydroxide solution into the mixed solution, stirring, mixing and collecting to obtain a suspension;
(3) and then mixing the components in a volume ratio of 1: and 10-15, mixing the silane coupling agent with the suspension, adjusting the pH to 10.0, carrying out heat preservation reaction at 40-45 ℃, collecting the reaction liquid, placing the reaction liquid at 45-60 ℃, and carrying out rotary evaporation until the volume of the reaction liquid is 1/3, thus obtaining the hydrophilic porous silicon dioxide.
6. The admixture for recycled aggregate concrete according to claim 4, wherein the filling and coating of the oxygen scavenger comprises the following steps:
(1) mixing polyvinylpyrrolidone, sodium erythorbate, sodium hexametaphosphate, D-sodium gluconate and zinc sulfate according to a formula to obtain mixed granules, wherein the mass ratio of the mixed granules to the total mass of the granules is 1: 20, adding the mixed particles into water, and stirring and mixing to obtain a coating filling liquid;
(2) according to the volume ratio of 2-3: stirring and mixing hydrophilic porous silicon dioxide and coating filling liquid, performing centrifugal separation after ultrasonic dispersion, taking a lower layer for precipitation, drying, crushing, grinding and sieving to complete filling and coating of the deoxidant.
7. The method for preparing the admixture for recycled aggregate concrete according to any one of claims 1 to 6, characterized by comprising the following preparation steps:
s1, and the molar mass ratio of the materials is 1: 1, stirring, mixing and homogenizing hydrophilic solid silica sol and hydrophilic porous silica sol filled with deoxidant to obtain a homogenized mixed solution;
and S2, mixing the homogeneous mixed solution, the sulfamate water reducer, the polycarboxylic acid water reducer and water according to the formula, placing the mixture in an oil bath at the temperature of 100-110 ℃, heating for 2-3 hours, standing, cooling to room temperature, and defoaming to obtain the additive for the recycled aggregate concrete.
8. The method for preparing an admixture for recycled aggregate concrete according to claim 7, wherein the solid contents of the hydrophilic solid silica sol and the hydrophilic porous silica sol are both 15%.
Technical Field
The application relates to the field of concrete admixtures, in particular to an admixture for recycled aggregate concrete and a preparation method thereof.
Background
The construction waste is used as recycled aggregate for development and application, so that the problem that a large amount of waste concrete is difficult to treat is solved; on the other hand, the consumption of natural aggregate in the construction industry can be reduced, so that the exploitation of natural sandstone is reduced, the problems that the natural aggregate is increasingly deficient and a large amount of sandstone is destroyed to the ecological environment are fundamentally solved, the living environment of human is protected, and the requirement of sustainable development is met.
Compared with common concrete, the main difference of the recycled concrete is the difference between the recycled aggregate and the natural aggregate. The recycled aggregate obtained by crushing, screening, leaching, drying and other treatments of the waste concrete has more edges and corners and rough surface, the components contain a certain amount of hardened cement mortar, and in addition, a plurality of micro cracks are formed in the concrete block in the crushing process due to mechanical damage, so that the apparent density of the recycled aggregate is small, the void ratio is large, the water absorption rate is large, and the crushing index value is high, so that the mechanical strength and the performance of the recycled aggregate concrete can be improved by adding the additive.
In view of the above-mentioned related technologies, the inventor believes that, in the process of improving the strength of the admixture adopted by the existing recycled aggregate, the recycled aggregate concrete has insufficient density due to large internal structural voids of the recycled aggregate and excessive oxygen is easy to accumulate, and after the recycled aggregate is directly doped into the concrete, the workability and the fluidity of the concrete are reduced due to the rough structure of the recycled aggregate.
Disclosure of Invention
In order to improve the workability, the fluidity and the compactness of the recycled aggregate concrete after the additive is used, the application provides the additive for the recycled aggregate concrete and the preparation method thereof.
The application provides an additive for recycled aggregate concrete and a preparation method thereof, which adopt the following technical scheme:
an additive for recycled aggregate concrete comprises the following substances in parts by weight: 30-50 parts of a sulfamate water reducing agent, 20-30 parts of a polycarboxylic acid water reducing agent, 10-15 parts of nano silica sol and 20-45 parts of water; the nano silica sol comprises hydrophilic solid silica sol and hydrophilic porous silica sol which are mixed by equimolar mass.
By adopting the technical scheme, the water reducing agent and the nano silicon dioxide are added into the admixture, the slump retaining effect of the concrete is improved by adding the water reducing agent, and the concrete has good fluidity after being mixed; meanwhile, the additive adopts solid nano-silica sol and porous nano-silica sol to be compounded, and the formed composite sol is used as a filler of a pore structure in the recycled aggregate concrete to improve the compaction strength of the concrete structure, on the basis, the nano-silica sol can effectively permeate into pores of the concrete and react with calcium hydroxide added in the concrete through good activity of the nano-silica sol to generate hydrated calcium silicate gel, so that the concrete structure is continuously compacted in the actual use process and the mechanical property of the concrete is improved Fluidity and compactness.
Preferably, the surfaces of the particles of the hydrophilic porous silica sol are filled with and coated with an oxygen scavenger, and the filling and coating mass of the oxygen scavenger is 35-40% of that of the hydrophilic porous silica sol.
Through adopting above-mentioned technical scheme, this application is through filling cladding deoxidant inside the granule and the surface at this porous silica sol of hydrophilicity, improve deoxidant after the in-service use quick inactivation and lead to regeneration aggregate concrete at later stage in-process, because deoxidant premature release and lead to the not good problem of concrete compact structure, this application is through the scheme of cladding load, form good filling infiltration effect, even deoxidization and optimize concrete structure to the compactness of regeneration aggregate concrete has been improved.
Preferably, the oxygen scavenger comprises: 30-45 parts of polyvinylpyrrolidone, 15-25 parts of sodium erythorbate and 15-25 parts of sodium hexametaphosphate.
Through adopting above-mentioned technical scheme, this application is compounded through adding sodium erythorbate and sodium hexametaphosphate, carry out the deoxidization to concrete inner structure, guarantee that regeneration aggregate concrete material has suitable oxygen content, thereby improve the compact structure of concrete, simultaneously on this basis, this application adds polyvinylpyrrolidone in the deoxidant, this material has good film forming ability, cohesiveness, the hygroscopicity, solubilization or condensation, can form good load effect and slow release effect in hydrophilicity porous silica surface and the inside in hole, thereby in the use, improve the speed of deoxidant deoxidization inactivation, thereby improve regeneration aggregate concrete overall structure's compact performance.
Preferably, the oxygen scavenger further comprises the following components in parts by weight: 8-15 parts of D-sodium gluconate and 3-5 parts of zinc sulfate.
By adopting the technical scheme, the zinc-zinc complex is prepared by selecting and compounding the D-sodium gluconate and the zinc sulfate, compounding the D-sodium gluconate with the zinc sulfate through the adsorption effect of carboxyl and polyhydroxy of the D-sodium gluconate, and compounding Zn through the D-sodium gluconate and the zinc sulfate2+The composite deoxidant has good stabilizing effect, and ensures that all components of the deoxidant form good stable dispersion, thereby further improving the deoxidant effect of the deoxidant and improving the compactness of the whole structure of the recycled aggregate concrete.
Preferably, the hydrophilic porous silica sol is prepared by the following method: (1) according to the mass ratio of 1: 10-15, mixing silicon dioxide and a polyvinyl alcohol solution, placing the mixture in an oil bath at the temperature of 100-110 ℃ for heating treatment, and standing and cooling the mixture to room temperature to obtain a mixed solution; (2) according to the mass ratio of 1: 20-25, dropwise adding a sodium hydroxide solution into the mixed solution, stirring, mixing and collecting to obtain a suspension; (3) and then mixing the components in a volume ratio of 1: and 10-15, mixing the silane coupling agent with the suspension, adjusting the pH to 10.0, carrying out heat preservation reaction at 40-45 ℃, collecting the reaction liquid, placing the reaction liquid at 45-60 ℃, and carrying out rotary evaporation until the volume of the reaction liquid is 1/3, thus obtaining the hydrophilic porous silicon dioxide.
By adopting the technical scheme, the surface of the nano silicon dioxide particle is coated by the polyvinyl alcohol, and after the surface of the polyvinyl alcohol is coated, the sodium hydroxide is used for corrosion treatment, so that a good corrosion pore channel structure is formed on the surface of the nano silicon dioxide, and the nano silicon dioxide after corrosion is formed into a porous structure, so that a good loading effect can be formed on the deoxidant.
Preferably, the filling and coating of the oxygen scavenger comprises the following methods: (1) mixing polyvinylpyrrolidone, sodium erythorbate, sodium hexametaphosphate, D-sodium gluconate and zinc sulfate according to a formula to obtain mixed granules, wherein the mass ratio of the mixed granules to the total mass of the granules is 1: 20, adding the mixed particles into water, and stirring and mixing to obtain a coating filling liquid; (2) according to the volume ratio of 2-3: stirring and mixing hydrophilic porous silicon dioxide and coating filling liquid, performing centrifugal separation after ultrasonic dispersion, taking a lower layer for precipitation, drying, crushing, grinding and sieving to complete filling and coating of the deoxidant.
Through adopting above-mentioned technical scheme, this application adopts the deoxidant to inside good cladding that forms of sol material, inside permeating to porous silica granule through the deoxidant to form good packing to its hole and surface, the deoxidant of this scheme load has good packing clad effect, and the deoxidant of cladding improves its compact structure to inside effectual support and the packing of forming in porous silica hole simultaneously, thereby has improved regeneration aggregate concrete overall structure's compactedness ability.
In a second aspect, the present application provides a method for preparing an admixture for recycled aggregate concrete, comprising the following preparation steps: s1, and the molar mass ratio of the materials is 1: 1, stirring, mixing and homogenizing hydrophilic solid silica sol and hydrophilic porous silica sol filled with deoxidant to obtain a homogenized mixed solution; and S2, mixing the homogeneous mixed solution, the sulfamate water reducer, the polycarboxylic acid water reducer and water according to the formula, placing the mixture in an oil bath at the temperature of 100-110 ℃, heating for 2-3 hours, standing, cooling to room temperature, and defoaming to obtain the additive for the recycled aggregate concrete.
Through adopting above-mentioned technical scheme, this application technical scheme is earlier through carrying out the homogenization treatment with porous and solid nanometer silica granule to make porous and solid nanometer silica granule form good complex, on this basis, through carrying out effectual mixture with each component, form good dispersion even system, when later stage uses, even dispersion sol can effectively permeate to the inside in regeneration aggregate concrete pore, closely knit concrete carries out the degree of depth to concrete inside pore oxygen and gets rid of, has further improved the concrete compactness.
Preferably, the solid content of the hydrophilic solid silica sol and the solid content of the hydrophilic porous silica sol are both 15%.
Through adopting above-mentioned technical scheme, the solid content of silica sol is optimized in this application, has effectively improved the water reducing effect of regeneration aggregate concrete to improve the water reducing effect of additive, on this basis, through the improvement of its solid content, improve the concrete slow setting effect, thereby effectively improved concrete material's workability and closely knit degree.
In summary, the present application has the following beneficial effects:
1. this application adds water-reducing agent and nanometer silica in this admixture, add through the water-reducing agent earlier, improve concrete slump loss prevention effect, make the concrete mix the back and have good mobility, the rethread adds nanometer silica sol, as the inside pore structure's of regeneration aggregate concrete filler, improve the closely knit intensity of concrete structure, simultaneously this application is still through porous nanometer silica's interpolation, the specific surface area of compound silica sol has been improved, thereby make it mix with water after, adsorb a large amount of surface water, thereby reduce the hydration degree of cement, the workability of regeneration aggregate concrete has been improved, mobility and closely knit nature.
2. This application is through inside and the surface packing cladding deoxidant of the granule at this porous silica sol of hydrophilicity, improve quick deactivation after the deoxidant in-service use and lead to regeneration aggregate concrete at later stage in-process, because the deoxidant premature release leads to the not good problem of concrete compact structure, through the scheme of cladding load, form good filling infiltration effect, even deoxidization and optimize concrete structure to the compactness of regeneration aggregate concrete has been improved.
3. This application is compounded through adding sodium erythorbate and sodium hexametaphosphate, carry out the deoxidization to concrete inner structure, guarantee that regeneration aggregate concrete material has suitable oxygen content, thereby improve the closely knit structure of concrete, this application adds polyvinylpyrrolidone in the oxygen-eliminating agent simultaneously, form good load effect and slow release effect on hydrophilicity porous silica surface and pore inside, thereby in the use, improve the deactivated speed of oxygen-eliminating agent deoxidization, thereby improve regeneration aggregate concrete overall structure's closely knit performance.
4. According to the application, the D-sodium gluconate and the zinc sulfate are added into the deoxidant in a compounding manner, the D-sodium gluconate has a carboxyl and polyhydroxy adsorption effect, and is compounded with the zinc sulfate, so that Zn is treated by the D-sodium gluconate and the zinc sulfate2+The composite deoxidant has good stabilizing effect, and ensures that all components of the deoxidant form good stable dispersion, thereby further improving the deoxidant effect of the deoxidant and improving the compactness of the whole structure of the recycled aggregate concrete.
Detailed Description
The present application will be described in further detail with reference to examples.
Examples
In the examples of the present application, the raw materials used are as follows, but not limited thereto:
the cement is P.O 42.5 grade.
The natural aggregate is natural macadam with diameter of 20mm, crushing index of 4.7%, water absorption of 1.2%, and apparent density of 2660kg/m3；
The recycled aggregate is obtained by mechanically crushing and screening recycled construction waste and is from Huawei environmental protection building materials Co., Ltd, Shenzhen city.
The coarse aggregate had a diameter of 20mm, a crush index of 15.2%, a water absorption of 5.4%, and an apparent density of 2590kg/m3。
The fine aggregate is natural river sand with fineness modulus of 2.6 and apparent density of 2.65g/cm3. The fly ash is the II-grade fly ash sold in the market,
example 1:
mixing 200mL of hydrophilic silicon dioxide with a solid content of 15% and 2000mL of polyvinyl alcohol solution with a mass fraction of 5%, placing the mixture in an oil bath at 100 ℃ for heating treatment for 2 hours, and standing and cooling the mixture to room temperature to obtain a mixed solution; dropwise adding 5mL of 0.5mol/L sodium hydroxide solution into the mixed solution, controlling the dropwise adding rate to be 2mL/min, and collecting a suspension after the dropwise adding is finished; mixing 20mL of silane coupling agent with 200mL of suspension, adjusting the pH to 10.0, carrying out heat preservation reaction at 40 ℃ for 20h, collecting the reaction solution, placing the reaction solution into a reaction solution for rotary evaporation at 45 ℃, and obtaining hydrophilic porous silica sol when the reaction solution is evaporated to 1/3 of the volume of the reaction solution;
placing 800mL of deionized water, 10g of polyvinylpyrrolidone, 6g of sodium erythorbate, 6g of sodium hexametaphosphate, 3g of sodium D-gluconate and 1g of zinc sulfate in a stirring device, stirring, mixing, keeping the temperature at 85 ℃, mixing for 25min, standing, and cooling to room temperature to obtain a coating filling liquid;
stirring and mixing 50mL of hydrophilic porous silica sol and 20mL of coating filling liquid, placing the mixture into ultrasonic dispersion for 10min under 200W, collecting mixed suspension, placing the mixed suspension into centrifugal separation for 10min under 1500r/min, taking down the lower layer precipitate, placing the lower layer precipitate into a temperature-keeping drying room at 45 ℃ for 6h, crushing and grinding the mixture, and sieving the dried product by a 2000-mesh sieve to obtain coated modified nano silica particles;
the molar mass ratio of the massage is 1: 1: 25, stirring and mixing the coated modified nano silicon oxide particles, solid nano silicon dioxide and deionized water, placing the mixture in a homogenizer, and homogenizing the mixture for 2 hours at 4500r/min to obtain a homogeneous mixed solution;
and respectively weighing 30 parts by weight of sulfamate water reducer, 20 parts by weight of polycarboxylic acid water reducer, 10 parts by weight of homogeneous mixed liquor and 20 parts by weight of water, and stirring and mixing to obtain the admixture for the recycled aggregate concrete.
Example 2:
mixing 225mL of hydrophilic silicon dioxide with a solid content of 15% and 2500mL of polyvinyl alcohol solution with a mass fraction of 5%, heating in an oil bath at 105 ℃ for 2 hours, standing, and cooling to room temperature to obtain a mixed solution; dropwise adding 7mL of 0.5mol/L sodium hydroxide solution into the mixed solution, controlling the dropwise adding rate to be 2mL/min, and collecting a suspension after the dropwise adding is finished; mixing 27mL of silane coupling agent with 350mL of suspension, adjusting the pH to 10.0, then carrying out heat preservation reaction at 42 ℃ for 22h, collecting the reaction solution, placing the reaction solution into the reaction solution for rotary evaporation at 52 ℃, and obtaining hydrophilic porous silica sol when the reaction solution is evaporated to 1/3 of the volume of the reaction solution;
putting 900mL of deionized water, 12g of polyvinylpyrrolidone, 7g of sodium erythorbate, 7g of sodium hexametaphosphate, 4g of sodium D-gluconate and 2g of zinc sulfate into a stirring device, stirring, mixing, keeping the temperature at 90 ℃, mixing for 27min, standing, and cooling to room temperature to obtain a coating filling liquid;
stirring and mixing 68mL of hydrophilic porous silica sol and 25mL of coating filling liquid, placing the mixture into 250W for ultrasonic dispersion for 12min, collecting mixed suspension, placing the mixed suspension into 1750r/min for centrifugal separation for 12min, taking the lower-layer precipitate, placing the lower-layer precipitate into 47 ℃ for heat preservation and drying for 7h, crushing and grinding the mixture, and sieving the crushed mixture with a 2000-mesh sieve to obtain coated modified nano silica particles;
the molar mass ratio of the massage is 1: 1: 25, stirring and mixing the coated modified nano silicon oxide particles, solid nano silicon dioxide and deionized water, placing the mixture in a homogenizer, and homogenizing the mixture for 2 hours at the speed of 4750r/min to obtain a homogeneous mixed solution;
and respectively weighing 40 parts by weight of sulfamate water reducer, 25 parts by weight of polycarboxylic acid water reducer, 12 parts by weight of homogeneous mixed liquor and 32 parts by weight of water, and stirring and mixing to prepare the admixture for the recycled aggregate concrete.
Example 3:
mixing 250mL of hydrophilic silicon dioxide with solid content of 15% and 3000mL of polyvinyl alcohol solution with mass fraction of 5%, placing the mixture in an oil bath for heating treatment at 110 ℃ for 3 hours, and standing and cooling the mixture to room temperature to obtain a mixed solution; dripping 8mL of 0.5mol/L sodium hydroxide solution into the mixed solution, controlling the dripping speed to be 3mL/min, and collecting a suspension after the dripping is finished; mixing 35mL of silane coupling agent with 500mL of suspension, adjusting the pH to 10.0, carrying out heat preservation reaction at 45 ℃ for 24 hours, collecting the reaction solution, placing the reaction solution into the reaction solution for rotary evaporation at 60 ℃, and obtaining hydrophilic porous silica sol when the reaction solution is evaporated to 1/3 of the volume of the reaction solution;
putting 1000mL of deionized water, 15g of polyvinylpyrrolidone, 8g of sodium erythorbate, 8g of sodium hexametaphosphate, 5g of sodium D-gluconate and 2g of zinc sulfate into a stirring device, stirring, mixing, keeping the temperature at 100 ℃, mixing for 30min, standing, and cooling to room temperature to obtain a coating filling liquid;
stirring and mixing 80mL of hydrophilic porous silica sol and 30mL of coating filling liquid, placing the mixture into ultrasonic dispersion for 15min under 300W, collecting mixed suspension, placing the mixed suspension into centrifugal separation for 15min under 2000r/min, taking down the lower layer precipitate, placing the lower layer precipitate into a room at 50 ℃, keeping the temperature, drying for 8h, crushing, grinding and sieving by a 2000-mesh sieve to obtain coated modified nano silica particles;
the molar mass ratio of the massage is 1: 1: 25, stirring and mixing the coated modified nano silicon oxide particles, solid nano silicon dioxide and deionized water, placing the mixture in a homogenizer, and homogenizing the mixture for 3 hours at the speed of 5000r/min to obtain a homogenized mixed solution;
and respectively weighing 50 parts by weight of sulfamate water reducer, 30 parts by weight of polycarboxylic acid water reducer, 15 parts by weight of homogeneous mixed liquor and 45 parts by weight of water, and stirring and mixing to prepare the admixture for the recycled aggregate concrete.
Examples 4 to 6
In the examples 4 to 6, no oxygen scavenger was added during the preparation of the admixture for recycled aggregate concrete, and the conditions and the component ratio were the same as those in the examples 4 to 6 corresponding to the examples 1 to 3, respectively.
Examples 7 to 9
In the preparation processes of the oxygen scavengers in the embodiments 7 to 9, the sodium D-gluconate and the zinc sulfate are not added, and the other conditions and the component proportions are the same as those of the embodiments 7 to 9 respectively corresponding to the embodiments 1 to 3.
Performance test
The performance tests of examples 1 to 9 were performed, and the workability, impermeability and mechanical properties of the recycled aggregate concrete were measured after the admixtures for recycled aggregate concrete prepared in examples 1 to 9 were used.
Detection method/test method
The concrete is prepared by screening and preparing raw materials according to the element composition proportion in the following table 1:
TABLE 1 main composition of concrete
(3) And (3) workability test:
slump: the test is carried out according to the standard of the test method for the performance of common concrete mixtures (GB/T50080-2016), the recycled concrete is mixed, and the test slump is measured by a slump cone and is recorded.
(2) Mechanical properties:
compressive strength: the sizes of concrete cubic compression-resistant test blocks are 150mm multiplied by 150mm, the test blocks are demoulded after 24h, and the compression strength of the test piece is measured after the test piece is cured for 28 days under standard conditions according to the standard of the test method for the mechanical property of common concrete (GB/T50081-2002).
(3) Impermeability:
durability: the impermeability test method is carried out according to the impermeability test method in the test method of the long-term performance and the durability of ordinary concrete (GB/T50082-2009), the impermeability height method is adopted in the impermeability test, and the water permeability resistance of the recycled concrete is researched by measuring the permeability height and calculating the relative permeability coefficient.
The specific detection results are shown in the following table 2:
TABLE 2 Performance test Table
Referring to the comparison of the performance tests of table 2, it can be found that:
the performances of the examples 1 to 3 are compared, wherein the compressive strength, permeability coefficient and slump property in the example 3 are the best, and the addition ratio of each component is the highest in the example 3 compared with the examples 1 and 2, so that the technical scheme of the application can be implemented.
With embodiment 1 ~ 3 and embodiment 4 ~ 6 go the performance contrast, because embodiment 4 ~ 6 in the additive preparation in-process for the recycled aggregate concrete, do not add the deoxidant, and it does not have obvious change although the slump, this demonstrates that the deoxidant is less to the modification of fluidity, but osmotic coefficient and compressive strength all show and descend, this demonstrates the deoxidant that this application adopted, through carrying out the deoxidization to concrete inner structure, guarantee that recycled aggregate concrete material has suitable oxygen content, thereby improve the compact structure of concrete, thereby improve the compact performance of recycled aggregate concrete overall structure.
Compared with the performance of the embodiments 1-3 and 7-9, the performance of the embodiments 7-9 is compared, and because the D-sodium gluconate and the zinc sulfate are not added in the preparation process of the deoxidant, and although the slump constant of the deoxidant is not obviously changed, the permeability coefficient and the compressive strength are both reduced in a small degree, the deoxidant adopted in the application is explained, and the D-sodium gluconate and the zinc sulfate are selected for compounding, so that the deoxidant effect of the deoxidant can be further improved, and the compactness of the whole structure of the recycled aggregate concrete is improved.
Comparative example
Comparative examples 1 to 3
In comparative examples 1 to 3, no nano silica sol was added during the preparation of the oxygen scavenger, which is the same as the other conditions and component ratios of comparative examples 1 to 3 corresponding to examples 1 to 3, respectively.
Comparative examples 4 to 6
Comparative examples 4 to 6 in the preparation process of the oxygen scavenger, only the solid nano silica sol was added instead of the nano silica sol used in the present application, and the other conditions and the component ratios of comparative examples 4 to 6 respectively corresponding to examples 1 to 3 were the same.
Comparative examples 7 to 9
In comparative examples 7 to 9, only the porous nano silica sol was added in place of the nano silica sol used in the present application during the preparation of the oxygen scavenger, and the other conditions and the component ratios were the same as in comparative examples 7 to 9 corresponding to examples 1 to 3, respectively.
Comparative examples 10 to 12
In comparative examples 10 to 12, only ascorbic acid was added instead of the oxygen scavenger in the preparation process of the oxygen scavenger, which was the same as the other conditions and component ratios of comparative examples 10 to 12 corresponding to examples 1 to 3, respectively.
Performance test
After the admixture for the recycled aggregate concrete prepared in the comparative examples 1-12 is used, the workability, impermeability and mechanical properties of the recycled aggregate concrete are detected.
Detection method/test method
The cement is P.O 42.5 grade.
The natural aggregate is natural macadam with diameter of 20mm, crushing index of 4.7%, water absorption of 1.2%, and apparent density of 2660kg/m3；
The recycled aggregate is obtained by mechanically crushing and screening recycled construction waste and is from Huawei environmental protection building materials Co., Ltd, Shenzhen city.
The coarse aggregate had a diameter of 20mm, a crush index of 15.2%, a water absorption of 5.4%, and an apparent density of 2590kg/m3。
The fine aggregate is natural river sand with fineness modulus of 2.6 and apparent density of 2.65g/cm3. The fly ash is II-grade fly ash purchased in the market.
(3) And (3) workability test:
slump: the test is carried out according to the standard of the test method for the performance of common concrete mixtures (GB/T50080-2016), the recycled concrete is mixed, and the test slump is measured by a slump cone and is recorded.
(2) Mechanical properties:
compressive strength: the sizes of concrete cubic compression-resistant test blocks are 150mm multiplied by 150mm, the test blocks are demoulded after 24h, and the compression strength of the test piece is measured after the test piece is cured for 28 days under standard conditions according to the standard of the test method for the mechanical property of common concrete (GB/T50081-2002).
(3) Impermeability:
durability: the impermeability test method is carried out according to the impermeability test method in the test method of the long-term performance and the durability of ordinary concrete (GB/T50082-2009), the impermeability height method is adopted in the impermeability test, and the water permeability resistance of the recycled concrete is researched by measuring the permeability height and calculating the relative permeability coefficient.
The specific detection results are shown in the following table 3:
TABLE 3 Performance test Table
Referring to the performance test comparison of table 3, it can be found that:
comparing the comparative examples 1 to 3 with the examples 1 to 3, in the comparative examples 1 to 3, in the preparation process of the deoxidant, the nano silica sol is not added, as can be seen from table 3, the compressive strength, the mechanical property and the workability of the concrete are all reduced, and simultaneously the compressive strength and the mechanical property are greatly reduced, namely, the admixture prepared by the method adopts the solid nano silica sol and the porous nano silica sol to be compounded after the concrete is used, the compact strength of a concrete structure is improved by using the composite sol as a filler of a pore structure in the recycled aggregate concrete, and the specific surface area of the composite silica sol is improved by adding the porous nano silica, so that the admixture is mixed with water to adsorb a large amount of surface water, thereby reducing the hydration degree of cement, improving the workability of the recycled aggregate concrete, Fluidity and compactness.
Comparing the comparative examples 4-6 with the examples 1-3, the comparative examples 4-6 only add solid nano silica sol, replace the nano silica sol adopted in the present application, the impermeability and the mechanical strength are all reduced, which shows that the solid nano silica sol can be used as the filler of the internal pore structure of the recycled aggregate concrete, the compact strength of the concrete structure is improved, and simultaneously, the solid nano silica sol penetrates into the concrete pores, reacts with calcium hydroxide added in the concrete through the good activity of the solid nano silica sol, and generates hydrated calcium silicate gel, thereby continuously compacting the concrete structure and improving the mechanical property of the concrete in the actual use process.
Comparing the comparative examples 7-9 with the examples 1-3, in the preparation process of the deoxidant, only adding the porous nano silica sol to replace the nano silica sol adopted in the application to cause the reduction of the compressive strength and the impermeability of the deoxidant in the comparative examples 7-9, which shows that the specific surface area of the composite silica sol is improved by adding the porous nano silica, so that the composite silica sol can adsorb a large amount of surface water after being mixed with water, thereby reducing the hydration degree of cement and improving the fluidity and the compactness of the recycled aggregate concrete.
Compare this application comparative example 10 ~ 12 and embodiment 1 ~ 3, in the comparative example 10 ~ 12 in the oxygen-eliminating agent preparation process, only add ascorbic acid and replace the oxygen-eliminating agent, this mobility and the compactibility that leads to the concrete have a small amplitude and descend, this shows that in the admixture of this application preparation, through the oxygen-eliminating agent material of complex, can permeate inside the porous silica granule, thereby form good packing to its hole and surface, improve the inside compact structure of concrete, thereby the compaction performance of regeneration aggregate concrete overall structure has been improved.
The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.