CN113185169B - Recycled aggregate soaked based on metakaolin slurry and modification method thereof - Google Patents
Recycled aggregate soaked based on metakaolin slurry and modification method thereof Download PDFInfo
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- CN113185169B CN113185169B CN202110240510.6A CN202110240510A CN113185169B CN 113185169 B CN113185169 B CN 113185169B CN 202110240510 A CN202110240510 A CN 202110240510A CN 113185169 B CN113185169 B CN 113185169B
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B20/00—Use of materials as fillers for mortars, concrete or artificial stone according to more than one of groups C04B14/00 - C04B18/00 and characterised by shape or grain distribution; Treatment of materials according to more than one of the groups C04B14/00 - C04B18/00 specially adapted to enhance their filling properties in mortars, concrete or artificial stone; Expanding or defibrillating materials
- C04B20/10—Coating or impregnating
- C04B20/1055—Coating or impregnating with inorganic materials
- C04B20/1077—Cements, e.g. waterglass
- C04B20/1081—Mineral polymers, e.g. geopolymers
Abstract
The invention belongs to the technical field of building materials, and particularly relates to a method for modifying recycled aggregate based on metakaolin slurry soaking, which mainly comprises the following steps: preparing raw materials, namely weighing 60-90 parts of metakaolin, 30-65 parts of fly ash, 30-65 parts of silica fume, 0.5-1.5 parts of water reducing agent, 2-3.5 parts of alkali activator, 2-3 parts of water glass solution and 35-60 parts of water by weight; mixing and stirring metakaolin, fly ash and silica fume uniformly according to the proportion to obtain a dry mixture; mixing water, a water reducing agent, an alkaline activator and a water glass solution in proportion and uniformly stirring to obtain a mixed solution; mixing the dry mixture and the mixed solution in proportion and uniformly stirring to obtain metakaolin slurry; and (3) pretreating the recycled coarse aggregate, soaking the recycled coarse aggregate in metakaolin slurry, filtering the slurry after the slurry is saturated by water absorption, and drying the slurry to obtain the modified recycled aggregate. The method can utilize the existing waste to the maximum extent and realize the resource utilization of industrial waste.
Description
Technical Field
The invention belongs to the technical field of building materials, and particularly relates to a method for modifying recycled aggregate based on metakaolin slurry soaking.
Background
Along with the large-scale progress of urbanization construction, a large amount of buildings are dismantled, so that a large amount of building garbage is stockpiled and cannot be consumed. The construction waste comprises residue soil, waste concrete, waste masonry and other wastes. In the prior art, the main treatment modes of the construction demolition waste are in-situ landfill, roadbed utilization, the production of recycled bricks by using recycled aggregates, the production of recycled concrete and the like. The method for producing various building products by using the construction waste to produce the recycled aggregate and adding auxiliary materials such as cement, fly ash and the like is an environment-friendly and economic mode. However, the recycled aggregate prepared from the construction waste has low strength, high porosity and water absorption and is not beneficial to engineering use due to the defect of the construction waste, namely a large number of micro cracks exist on the surface.
Therefore, it is necessary to perform a surface modification treatment on recycled aggregate in order to enable the recycled aggregate to be used in large quantities in engineering. The existing recycled aggregate modification mainly comprises two methods, one is a physical purification modification method, and a mortar layer on the surface of the recycled aggregate is removed and weakened by methods such as mechanical strengthening, heating grinding, wet processing and the like; one is a chemical strengthening modification method, which fills the pores on the surface of the recycled aggregate by methods such as polymer solution, micro powder, CO2 carbonization strengthening and the like to improve the physical properties of the recycled aggregate.
However, the above methods all have some disadvantages, such as the occurrence of alkali-silica reaction, poor compatibility of organic polymer and concrete, etc., so there is a need to develop an efficient and novel method for modifying aggregate, so that the recycled aggregate can overcome the problems of low strength and low water absorption, and the recycled aggregate can meet the requirements of current buildings.
Disclosure of Invention
The invention aims to further optimize the method for modifying the recycled aggregate, repair the microcracks of the mortar layer on the surface of the recycled aggregate, fill the pores on the surface of the recycled aggregate, reduce the water absorption of the recycled aggregate, improve the strength of the recycled aggregate, enhance the bonding strength of the modified aggregate and the concrete, and further improve the performance of the recycled aggregate. On one hand, the pollution problem of the waste concrete to the ecological environment due to mass storage is relieved, and the waste concrete is popularized and applied as a green building material; on the other hand, the recycled aggregate is fully utilized, the environment is further protected, and green production is realized.
The invention provides a method for modifying recycled aggregate based on metakaolin slurry soaking, which mainly comprises the following steps:
s1: preparing raw materials, namely respectively weighing 60-90 parts of metakaolin, 30-65 parts of fly ash, 30-65 parts of silica fume, 0.5-1.5 parts of water reducing agent, 2-3.5 parts of alkali activator, 2-3 parts of water glass solution and 35-60 parts of water by weight;
s2, mixing metakaolin, fly ash and silica fume according to the proportion, and uniformly stirring to obtain dry mixture;
s3, mixing water, a water reducing agent, an alkaline activator and a water glass solution in proportion and uniformly stirring to obtain a mixed solution;
s4, mixing the dry mixture prepared in the S2 and the mixed solution prepared in the S3 in proportion, and uniformly stirring to obtain metakaolin slurry;
and S5, pretreating the recycled coarse aggregate, soaking the recycled coarse aggregate in the metakaolin slurry prepared in the S4 until the metakaolin slurry is saturated in water, filtering out the slurry, and drying the slurry to obtain the modified recycled aggregate.
Further, the alkali-activator is a 40% NaOH solution.
Further, the concentration of the water glass solution is 10%.
Further, the water absorption of the modified recycled aggregate for 24 hours is 4-7%.
Furthermore, the recycled coarse aggregate in S5 is waste concrete with the particle size of 5-25 mm.
Further, the pretreatment step of the recycled coarse aggregate in S5 is as follows: and (3) putting the regenerated coarse aggregate into water, soaking for 24 hours, and filtering.
The technical scheme provided by the invention has the beneficial effects that: the method for modifying the recycled aggregate based on metakaolin slurry soaking has the following advantages:
1. the metakaolin, the silica fume and the fly ash adopted by the invention have the characteristics of large specific surface area, high reaction activity and the like, are suitable for being excited under alkaline conditions to form a high-strength cementing material, are beneficial to the preparation of high-strength and high-durability building materials, can utilize the existing wastes to the maximum extent, and can realize the resource utilization of industrial wastes;
2. according to the invention, NaOH solution, water glass solution and metakaolin are adopted, under the action of the NaOH solution and the water glass solution, OH-ions break through the network structure of Al-O, Si-O bonds in the fly ash to form a low-activity state, an alkaline activator and an active silicon-aluminum mineral admixture are utilized, and ettringite and C-S-H gel are generated through natural hydration to wrap the recycled aggregate, so that the internal pores of the recycled aggregate are filled, the mortar microcracks on the surface of the recycled aggregate are repaired, and the water absorption of the recycled aggregate is reduced;
3. the method has the advantages of simple operation, simple and easily obtained preparation raw materials, low cost, easy adjustment of the concentration of metakaolin slurry and convenient realization of functionalization;
4. the invention greatly reduces the burden of industrial solid waste discharge on the environment, reduces the cost, reduces the resource consumption, realizes the functionalization, the greening and the high-valued of the product while largely consuming the industrial solid waste, and has good economic benefit and social benefit.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be further described below.
The embodiment of the invention provides a method for modifying recycled aggregate based on metakaolin slurry soaking, which mainly comprises the following steps:
s1: preparing raw materials, namely weighing 60-90 parts of metakaolin, 30-65 parts of fly ash, 30-65 parts of silica fume, 0.5-1.5 parts of water reducing agent, 2-3.5 parts of alkali activator, 2-3 parts of water glass solution and 35-60 parts of water by weight; wherein the alkali activator is a NaOH solution with the concentration of 40%, and the concentration of the water glass solution is 10%;
s2, mixing metakaolin, fly ash and silica fume according to the proportion, and uniformly stirring to obtain dry mixture;
s3, mixing water, a water reducing agent, an alkaline activator and a water glass solution in proportion and uniformly stirring to obtain a mixed solution;
s4, mixing the dry mixture prepared in the S2 and the mixed solution prepared in the S3 in proportion, and uniformly stirring to obtain metakaolin slurry;
s5, placing the recycled coarse aggregate into water to be soaked for 24 hours, filtering out, weighing 2kg of recycled coarse aggregate to measure water absorption, then soaking the soaked recycled coarse aggregate into the metakaolin slurry prepared in the S4, filtering out after water absorption is saturated, airing to obtain modified recycled aggregate, placing the modified recycled aggregate into water to be soaked for 24 hours, filtering out, weighing 2kg of modified recycled aggregate to measure water absorption. Wherein, the recycled coarse aggregate is waste concrete, and the particle size of the recycled coarse aggregate is 5-25mm after the recycled coarse aggregate is crushed by a jaw crusher. The aim of adjusting the concentration of the metakaolin slurry can be achieved by adjusting the proportion of the materials, so that the integrity of the regenerated coarse aggregate package is improved, and the functionalization is conveniently realized.
The recycled aggregate modified by the method has the water absorption rate of 4-7% in 24 hours.
In the invention, alkaline excitant and active silicon-aluminum mineral admixture are utilized to form metakaolin slurry, the recycled coarse aggregate is wrapped to fill internal pores and repair surface microcracks, thus improving the performance of the recycled aggregate, reducing the water absorption of the recycled aggregate, reducing the water consumption of the recycled concrete, obviously improving the strength of the recycled aggregate concrete and improving the utilization rate of the recycled aggregate in the concrete.
In addition, the invention adopts NaOH solution, water glass solution and metakaolin, OH-ions break the network structure of Al-O, Si-O bonds in the fly ash under the action of the NaOH solution, the fly ash becomes a low-activity state, an alkaline excitant and an active silicon-aluminum mineral admixture are utilized to generate ettringite and C-S-H gel through natural hydration to wrap the recycled aggregate, the internal pores of the recycled aggregate are filled, the mortar microcracks on the surface of the recycled aggregate are repaired, and the water absorption of the recycled aggregate is reduced.
< example 1>
S1, preparing raw materials, namely weighing 60 parts of metakaolin, 30 parts of fly ash, 30 parts of silica fume, 0.5 part of water reducing agent, 2 parts of 40% concentration NaOH solution, 2 parts of 10% concentration water glass solution and 35 parts of water respectively by weight;
s2, mixing metakaolin, fly ash and silica fume according to the proportion, putting the mixture into a stirrer, and uniformly stirring to obtain a dry mixture;
s3, putting water, a water reducing agent, an alkaline activator and a water glass solution into a volumetric barrel according to a proportion, mixing and uniformly stirring to obtain a mixed solution;
s4, mixing the dry mixture prepared in the S2 and the mixed solution prepared in the S3 in proportion, and uniformly stirring to obtain metakaolin slurry;
s5, taking the recycled coarse aggregate with the particle size of 5-25mm, placing the recycled coarse aggregate into water for soaking for 24h, filtering, weighing 2kg of recycled coarse aggregate to measure the water absorption, then soaking the soaked recycled coarse aggregate into the metakaolin slurry prepared in S4, filtering after water absorption is saturated, airing to obtain the modified recycled aggregate, placing the modified recycled aggregate into water for soaking for 24h, filtering, weighing 2kg of modified recycled aggregate to measure the water absorption.
In this example, the water absorption of the soaked recycled coarse aggregate was 10.3%, and the water absorption of the soaked modified recycled aggregate was 4.3%.
< example 2>
S1, preparing raw materials, namely weighing 70 parts of metakaolin, 40 parts of fly ash, 40 parts of silica fume, 0.8 part of water reducing agent, 2.5 parts of 40% NaOH solution, 2.2 parts of 10% sodium silicate solution and 40 parts of water by weight respectively;
s2, mixing metakaolin, fly ash and silica fume according to the proportion, putting the mixture into a stirrer, and uniformly stirring to obtain dry mixture;
s3, putting water, a water reducing agent, an alkaline activator and a water glass solution into a volumetric barrel according to a proportion, mixing and uniformly stirring to obtain a mixed solution;
s4, mixing the dry mixture prepared in the S2 and the mixed solution prepared in the S3 in proportion, and uniformly stirring to obtain metakaolin slurry;
s5, taking the recycled coarse aggregate with the particle size of 5-25mm, placing the recycled coarse aggregate into water for soaking for 24h, filtering, weighing 2kg of recycled coarse aggregate to measure the water absorption, soaking the soaked recycled coarse aggregate into the metakaolin slurry prepared in the S4, filtering after the metakaolin slurry is saturated in water, airing to obtain the modified recycled aggregate, placing the modified recycled aggregate into water for soaking for 24h, filtering, weighing 2kg of modified recycled aggregate to measure the water absorption.
In this example, the water absorption of the soaked recycled coarse aggregate was 10.3%, and the water absorption of the soaked modified recycled aggregate was 4.5%.
< example 3>
S1, preparing raw materials, and respectively weighing 80 parts of metakaolin, 50 parts of fly ash, 50 parts of silica fume, 1.1 parts of a water reducing agent, 3 parts of a 40% NaOH solution, 2.8 parts of a 10% water glass solution and 50 parts of water by weight;
s2, mixing metakaolin, fly ash and silica fume according to the proportion, putting the mixture into a stirrer, and uniformly stirring to obtain dry mixture;
s3, putting water, a water reducing agent, an alkali activator and a water glass solution into a volumetric barrel according to a certain proportion, mixing and uniformly stirring to obtain a mixed solution;
s4, mixing the dry mixture prepared in the S2 and the mixed solution prepared in the S3 in proportion, and uniformly stirring to obtain metakaolin slurry;
s5, taking the recycled coarse aggregate with the particle size of 5-25mm, placing the recycled coarse aggregate into water for soaking for 24h, filtering, weighing 2kg of recycled coarse aggregate to measure the water absorption, soaking the soaked recycled coarse aggregate into the metakaolin slurry prepared in the S4, filtering after the metakaolin slurry is saturated in water, airing to obtain the modified recycled aggregate, placing the modified recycled aggregate into water for soaking for 24h, filtering, weighing 2kg of modified recycled aggregate to measure the water absorption.
In this example, the water absorption of the soaked recycled coarse aggregate was 10.3%, and the water absorption of the soaked modified recycled aggregate was 3.7%.
< example 4>
S1, preparing raw materials, namely weighing 90 parts of metakaolin, 65 parts of fly ash, 65 parts of silica fume, 1.5 parts of water reducing agent, 3.5 parts of 40% NaOH solution, 3 parts of 10% water glass solution and 60 parts of water by weight;
s2, mixing metakaolin, fly ash and silica fume according to the proportion, putting the mixture into a stirrer, and uniformly stirring to obtain a dry mixture;
s3, putting water, a water reducing agent, an alkaline activator and a water glass solution into a volumetric barrel according to a proportion, mixing and uniformly stirring to obtain a mixed solution;
s4, mixing the dry mixture prepared in the S2 and the mixed solution prepared in the S3 in proportion, and uniformly stirring to obtain metakaolin slurry;
s5, taking the recycled coarse aggregate with the particle size of 5-25mm, placing the recycled coarse aggregate into water for soaking for 24h, filtering, weighing 2kg of recycled coarse aggregate to measure the water absorption, then soaking the soaked recycled coarse aggregate into the metakaolin slurry prepared in S4, filtering after water absorption is saturated, airing to obtain the modified recycled aggregate, placing the modified recycled aggregate into water for soaking for 24h, filtering, weighing 2kg of modified recycled aggregate to measure the water absorption.
In this example, the water absorption of the soaked recycled coarse aggregate was found to be 10.3%, and the water absorption of the soaked modified recycled aggregate was found to be 4.8%.
The features of the embodiments and embodiments described herein above may be combined with each other without conflict.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and should not be taken as limiting the scope of the present invention, which is intended to cover any modifications, equivalents, improvements, etc. within the spirit and scope of the present invention.
Claims (3)
1. A method for modifying recycled aggregate based on metakaolin slurry soaking is characterized by mainly comprising the following steps:
s1: preparing raw materials, namely weighing 60-80 parts of metakaolin, 30-50 parts of fly ash, 30-50 parts of silica fume, 0.5-1.1 parts of water reducing agent, 2-3 parts of alkali activator, 2-2.8 parts of water glass solution and 35-50 parts of water by weight;
s2, mixing metakaolin, fly ash and silica fume according to the proportion, and uniformly stirring to obtain a dry mixture;
s3, mixing water, a water reducing agent, an alkaline activator and a water glass solution in proportion and uniformly stirring to obtain a mixed solution;
s4, mixing the dry mixture prepared in the S2 and the mixed solution prepared in the S3 in proportion, and uniformly stirring to obtain metakaolin slurry;
s5, pretreating the recycled coarse aggregate, soaking the recycled coarse aggregate in the metakaolin slurry prepared in the S4 until the metakaolin slurry is saturated in water, filtering out the slurry, and drying the slurry to obtain the modified recycled aggregate;
wherein the alkaline activator is NaOH solution with the concentration of 40%;
the concentration of the water glass solution is 10 percent;
the pretreatment step of the recycled coarse aggregate in the step S5 is as follows: and (3) putting the regenerated coarse aggregate into water, soaking for 24 hours, and filtering.
2. The method for modifying recycled aggregate based on metakaolin slurry soaking according to claim 1, wherein the water absorption of the modified recycled aggregate for 24 hours is 4-7%.
3. The method for modifying recycled aggregate based on metakaolin slurry soaking according to claim 1, wherein the recycled coarse aggregate in S5 is waste concrete with a particle size of 5-25 mm.
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