CN114956642A - Composite expanding agent based on regenerated micro powder and preparation method thereof - Google Patents
Composite expanding agent based on regenerated micro powder and preparation method thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
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- C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
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- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
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Abstract
The invention discloses a composite expanding agent based on regenerated micro powder and a preparation method thereof, wherein the composite expanding agent comprises the following components in parts by mass: 5-10 parts of regenerated micro powder, 30-60 parts of low-temperature calcined regenerated micro powder, 5-15 parts of granulated blast furnace slag powder, 5-10 parts of steel slag powder, 20-40 parts of amorphous calcium aluminate, 5-20 parts of gypsum, 0.01-0.05 part of dispersing agent and 0.1-0.4 part of water reducing agent; the low-temperature calcined regenerated micro powder is obtained by calcining the fine powder which is obtained by crushing and collecting concrete at 650-800 ℃ and preserving heat for 60-90 min. The method disclosed by the invention centers on the resource utilization requirement of solid wastes, and utilizes a large amount of fine powder generated in the construction waste crushing process of waste concrete, red bricks and the like, so that the carbon neutralization efficiency of buildings and industries is effectively improved. Compared with the traditional expanding agent, the composite expanding agent has the properties of high early strength, good fluidity, sulfate erosion resistance and the like.
Description
Technical Field
The invention relates to the technical field of building materials, in particular to a composite expanding agent based on regenerated micro powder and a preparation method thereof.
Background
The existing concrete expanding agent is developed on the basis of expansive cement, and the expanding agent is mixed in the stirring process of concrete to be mixed into expansive concrete, which can also be called as compensation shrinkage concrete. The main principle is that the expanding agent has a certain expansion capacity after being hydrated with cement, and the expansion capacity can just offset the shrinkage of the cement. At present, concrete expanding agents mainly made of inorganic materials mainly comprise: calcium sulphoaluminate concrete expanding agent which generates ettringite through hydration reaction; calcium oxide and magnesium oxide concrete expanding agents which generate calcium hydroxide/magnesium through hydration reaction; calcium sulphoaluminate and calcium oxide composite concrete expanding agent which generates ettringite and calcium hydroxide by hydration reaction. A large amount of natural calcium source materials and sulphoaluminate materials are consumed in the production process of the existing concrete expanding agent, wherein the natural calcium source materials are mainly limestone which is decomposed to form quick lime, and a large amount of carbon dioxide is discharged in the process of exploiting the limestone and calcining to form the quick lime, so that the strategic goal of 'double carbon' is not achieved in China. The main raw material of the sulphoaluminate material is bauxite, which is a non-renewable resource and is not beneficial to sustainable development. Meanwhile, the expansion rates and the efficiencies of different expansion sources are different, the calcium sulphoaluminate concrete expanding agent generally needs about 14 days to achieve stability, the calcium oxide expanding agent can reach a stable period within 1-4 days of hydration, and the two expanding agents cannot continuously and stably provide expansion capacity from the initial stage to the later stage of hydration. If the calcium sulphoaluminate and calcium oxide composite concrete expanding agent is doped, the expansion rate of the concrete needs to be controlled by some technical means, for example, the curing condition is harsh, the water demand is large, otherwise, the expansion effect is greatly reduced, and the strength is even obviously influenced. Therefore, the existing expanding agent mainly has the defects of high cost, environmental pollution, discontinuous expansion efficiency, no enhancement effect and the like.
Disclosure of Invention
The invention provides a composite expanding agent based on regenerated micro-powder and a preparation method thereof, the composite expanding agent has the characteristics of high early strength, micro-expansion, quick condensation, high reutilization rate of solid waste resources, good durability and the like, and the problems of large shrinkage of cement-based materials and low utilization rate of the regenerated micro-powder are effectively solved.
The purpose of the invention is realized by the following technical scheme:
the first purpose of the invention is to provide a composite expanding agent based on regenerated micro-powder, which consists of the following components: regenerated micro powder, low-temperature calcined regenerated micro powder, granulated blast furnace slag powder, steel slag powder, amorphous calcium aluminate, gypsum, a dispersing agent and a water reducing agent.
In one embodiment of the invention, the regenerative micro powder composite expanding agent consists of the following components in parts by mass: 5-10 parts of regenerated micro powder, 30-60 parts of low-temperature calcined regenerated micro powder, 5-15 parts of granulated blast furnace slag powder, 5-10 parts of steel slag powder, 20-40 parts of amorphous calcium aluminate, 5-20 parts of gypsum, 0.01-0.05 part of dispersing agent and 0.1-0.4 part of water reducing agent.
In one embodiment of the invention, the regenerated micro powder is fine powder obtained by crushing and collecting concrete, and the fineness of the fine powder is less than or equal to 75 microns.
In one embodiment of the invention, the low-temperature calcined regenerated micro powder is obtained by low-temperature calcination of fine powder ground collected by concrete crushing; the low temperature is 650-800 ℃, the calcining time is 60-90 min, and the powder is ground until the specific surface area is more than or equal to 400m 2 /kg。
In one embodiment of the invention, the main mineral component of the amorphous calcium aluminate is dodecacalcium heptaluminate (C) 12 A 7 ) And tricalcium aluminate (C) 3 A) (ii) a Wherein C is 12 A 7 The content of (B) is more than 90%.
In one embodiment of the invention, the specific surface area of the amorphous calcium aluminate is more than or equal to 500m 2 /kg。
In one embodiment of the invention, the water reducing agent is a polycarboxylic acid high-efficiency water reducing agent and/or a naphthalene high-efficiency water reducing agent.
In one embodiment of the invention, the water reducing rate of the water reducing agent is more than or equal to 30%.
In one embodiment of the invention, the dispersing agent is aluminum stearate and/or cellulose ether.
In one embodiment of the invention, the proportion of the regenerated micropowder composite expanding agent replacing cement is 5-15% (mass percent).
In one embodiment of the invention, the granulated blast furnace slag powder meets the activity index and fluidity ratio requirements of grade S95 specified in GB/T18046-2017 granulated blast furnace slag powder for use in cement, mortar and concrete.
In one embodiment of the invention, the steel slag powder meets the requirements of activity index and fluidity ratio of the primary steel powder specified in GB/T20491-2006 Steel slag powder for Cement and concrete.
In one embodiment of the invention, the gypsum is dihydrate gypsum meeting the requirements of GB/T21371-2019 "Industrial by-product Gypsum for use in Cement".
The invention also aims to provide a preparation method of the composite expanding agent based on the regenerated micro powder, which comprises the following steps: uniformly mixing the regenerated micro powder, the low-temperature calcined regenerated micro powder, the granulated blast furnace slag powder, the steel slag powder, the amorphous calcium aluminate, the gypsum, the water reducer and the dispersant to obtain the regenerated micro powder composite expanding agent.
The process flow diagram of the composite expanding agent is shown in figure 1, and specifically comprises the following steps:
s1: grinding the fine powder collected in the winnowing process in the waste concrete crushing process to 75 microns to obtain regenerated micro powder with alkali-activated activity;
s2: calcining the regenerated micro powder obtained from S1 in a muffle furnace at 650-800 ℃, preserving heat for 60-90 min, and grinding until the specific surface area is more than or equal to 400m 2 Per kg, obtaining low-temperature calcined regenerated micro powder;
s3: 5-10 parts of regenerated micro powder obtained in S1, 30-60 parts of low-temperature calcined regenerated micro powder obtained in S2, 5-15 parts of granulated blast furnace slag powder, 5-10 parts of steel slag powder, 20-40 parts of amorphous calcium aluminate, 5-20 parts of gypsum, 0.01-0.05 part of dispersant and 0.1-0.4 part of water reducer are uniformly mixed to obtain the composite expanding agent based on the regenerated micro powder.
The regenerated micro powder in the composite expanding agent based on the regenerated micro powder is the fine powder collected in the winnowing process of the construction waste crushing process, and the components of the powder are SiO 2 、CaCO 3 、Ca(OH) 2 Calcium silicate hydrate and calcium aluminate, and the like. The regenerated micro powder has more surface pores, higher water absorption and no cementing hydration capacity, and is prepared by grinding the fine powder collected in the winnowing process of the waste concrete crushing process to below 75 microns, namely, the regenerated micro powder is subjected to mechanical activation (grinding).
The low-temperature calcined regenerated micro powder is obtained by calcining the ground regenerated micro powder in a muffle furnace at the temperature of 650-800 ℃ and preserving the heat for 60-90 min, and the component of the regenerated micro powder is usually SiO 2 、CaO、Ca 2 SiO 4 And the like, has hydration activity and has synergistic hydration effect with aluminum phase minerals.
The amorphous calcium aluminate consists of CaO and Al 2 O 3 Mixing at a certain proportion, melting at a high temperature of 1200 deg.C, quickly air cooling, grinding to a certain fineness to obtain amorphous calcium aluminate, wherein dodecacalcium heptaluminate (C) 12 A 7 ) The content is more than 90 percent, and the balance is mainly tricalcium aluminate (C) 3 A)。
The granulated blast furnace slag powder is a powder material obtained by grinding water-quenched granulated blast furnace slag to a certain fineness, the surface of the particles is rough, and the active substance is SiO 2 Has high content and high hydraulicity.
The steel slag powder is a powder material which is produced in the steel-making process and has the waste slag of certain fineness after being ground, the particle surface is rough, and the chemical composition of the steel slag mainly comprises CaO and SiO 2 、Al 2 O 3 、Fe 2 O 3 MgO, similar to cement clinker in composition, and has higher free calcium oxide component and micro-expansion effect.
The low-temperature calcined regenerated micro powder is mixed with aluminum stearate and/or cellulose ether, so that a thin layer of aluminum stearate and/or cellulose ether is coated on the surface of CaO particles to prevent CaO from contacting with slurry in the early stage of hydration, prolong the setting time of the slurry and play a role in dispersion.
In the process of preparing the composite expanding agent based on the regenerated micro powder, the original C-S-H gel structure surface layer in the regenerated micro powder is damaged due to the mechanical activation, the particle size distribution of the regenerated micro powder and the polymerization degree and mode of Si-O bonds and Al-O bonds in the regenerated micro powder are changed, meanwhile, the specific surface area of the regenerated micro powder is further increased, the activity of the regenerated micro powder is improved, the depolymerization-polycondensation reaction can be carried out in alkaline environments such as slag powder, steel slag powder and gypsum slurry, and the multi-mineral hardened slurry is formed. The DSC curve of the multi-mineral hardened slurry of the composite expanding agent based on the regenerated micro powder is shown in figure 2, and the hydraulic mineral in the regenerated micro powder calcined at low temperature is mainly C 2 S, the hydration products are C-S-H gel and Ca (OH) 2 Amorphous state C 12 A 7 The hydration product is C 2 AH 8 And C 3 AH 6 。C 2 S-C 12 A 7 The hydration product of the system is a C-S-H gel, C 2 AH 8 And C 3 AH 6 No Ca (OH) was found 2 . This is because C 12 A 7 Hydration releases Al (OH) 4- And Ca (OH) 2 Reaction to form C 3 AH 6 Thereby quickening C 2 And (4) hydrating the S. C 2 S-C 12 A 7 -CaSO 4 The hydration products of the system are C-S-H gel, AFt, C 3 AH 6 (weak dehydration peak) and no C was found 2 AH 8 And Ca (OH) 2 . Therefore, the hydration products after the low-temperature calcination regeneration micro powder, the amorphous calcium aluminate and the gypsum are compounded are C-S-H gel, AFt and C 3 AH 6 . This is because the presence of gypsum can interact with Ca in the liquid phase 2+ And Al (OH) 4- The combination of the two components forms hydrated calcium sulphoaluminate, reduces Al (OH) in a liquid phase 4- And the concentration accelerates the reaction rate. If the regenerated micro powder is not mixed, the SO is not provided for the liquid phase after the gypsum effect is finished 3 SO in liquid phase 3 Reduced concentration of ettringite and C 12 A 7 The reaction is converted into AFm, and the calcium carbonate in the regenerated micropowder can block AFt directionThe shift in AFm, continuously provides the micro-expansion effect. Therefore, the composite expanding agent of the invention contains Ca in the hydration reaction process 2+ 、SO 4 2- 、Al(OH) 4- The reaction generates AFt and consumes a large amount of Ca (OH) 2 To destroy C 2 Solid-liquid balance of S promotes C 2 S is hydrated to release more Ca 2+ Finally, the Ca (OH) in the hydration product is reduced 2 The content of (A) increases the hydration reaction rate of cement, and has obvious expansion effect and sulfate erosion resistance.
Low-temperature calcining regenerated micropowder to generate beta-C 2 S, CaO, and has good micro-expansion effect when reacting with amorphous calcium aluminate and gypsum to form ettringite and calcium hydroxide crystals. The content of calcium carbonate in the regenerated micro powder is high, and the compound system can stabilize ettringite and make the ettringite continuously have micro-expansion characteristic. The granulated blast furnace slag powder, the steel slag powder and hydration products C-S-H gel and hydrated calcium aluminate in the regenerated micro powder have the Si-O bond and the Al-O bond which are subjected to structural fracture and recombination under the alkaline excitation conditions of gypsum, calcium hydroxide and the like to generate a new cementing product. Along with the extension of the age, the structure of the solidified body is more compact, and the strength is gradually improved.
Therefore, when the silicate cement is mixed with the regenerated micro powder composite expanding agent, Ca (OH) 2 And C 12 A 7 Liberation of Al (OH) 4- Reaction to form C 3 AH 6 And ettringite, accelerates the hydration reaction of the portland cement, breaks down C 3 S、C 2 S and Ca (OH) 2 The solid-liquid balance of the solution accelerates the hydration reaction of silicate minerals, shortens the setting time, improves the early strength of the hardened slurry, generates a large amount of ettringite with a micro-expansion effect, can mutually promote the hydration process of cement, accelerates the formation of the hardened slurry structure and improves the physical and mechanical properties of the hardened slurry, namely mortar and concrete.
Compared with the prior art, the invention has the advantages that:
(1) the low-temperature calcined regenerated micro powder used by the invention mainly comprises dicalcium silicate, calcium oxide, quartz and other phases, wherein silicic acidDicalcium has hydration activity, and calcium oxide crystals have micro-expansion characteristics. The low-temperature calcined regenerated micro powder is compounded with aluminate minerals and gypsum to form ettringite (AFt) and calcium hydroxide, and the effect similar to that of a calcium sulphoaluminate and calcium oxide composite concrete expanding agent is formed. Meanwhile, calcium carbonate in the regenerated micro powder has the function of stabilizing ettringite (AFt), can prevent ettringite from being converted into monosulfide hydrated calcium sulfoaluminate (AFm) in the hydration process, has the synergistic hydration effect with slag powder and steel slag powder, ensures the strength development of the expanding agent in the use process of concrete, and can provide active SiO 2 And Al 2 O 3 The components accelerate the hydration of the composite expanding agent. Aluminum stearate/cellulose ether particles are coated on the surfaces of calcium sulphoaluminate and calcium oxide, so that the contact of CaO and the slurry is blocked at the early stage of hydration, and the setting time of the slurry is prolonged. The water reducing agent can adjust the working performance of the slurry. Therefore, the low-temperature calcined regenerated micro powder, the aluminum phase mineral and the gypsum are compounded to replace part of cement-based materials, and the slag powder, the steel slag powder and the additive are used as auxiliary materials, so that the cost can be reduced, the early strength can be improved, the micro-expansion effect can be achieved, and the method has important significance for large-amount and high-added-value utilization of the regenerated micro powder in the building material industry.
(2) The composite expanding agent prepared based on the processes of mechanical activation, alkali activation, low-temperature calcination and the like of the regenerated micro powder can realize the large-scale resource utilization of the regenerated micro powder, reduce the land occupation, save natural resources and improve the environment.
(3) The invention takes the regenerated micro powder, the low-temperature calcined regenerated micro powder, the granulated blast furnace slag powder, the steel slag powder, the amorphous calcium aluminate, the gypsum, the dispersant, the water reducer and the like as main raw materials, and the cement is added to ensure that the cement has the characteristics of good fluidity, high strength, good durability, micro-expansion and the like. Compared with the traditional cement-based expanding agent, the composite expanding agent based on the regenerated micro powder has the properties of high early strength, good fluidity, sulfate erosion resistance and the like.
(4) The preparation method is simple, does not need large-scale equipment and complex process, has flexible and adjustable composition and performance, is easy to control, has good applicability, and has the characteristics of low cost, good fluidity, high strength, high utilization rate of the regenerated micro powder, good durability, good shrinkage and the like.
Drawings
In order that the present disclosure may be more readily and clearly understood, reference is now made to the following detailed description of the embodiments of the present disclosure taken in conjunction with the accompanying drawings, in which
FIG. 1 is a schematic process flow diagram of the composite expansion agent of the present invention;
FIG. 2 is a DSC curve of a multimineral hardened slurry of the present invention;
FIG. 3 is an XRD spectrum of a cement hardened slurry with different amounts of composite expansion agent blended according to the present invention.
Detailed Description
The present invention is further described below in conjunction with the following figures and specific examples so that those skilled in the art may better understand the present invention and practice it, but the examples are not intended to limit the present invention.
Example 1
A composite expanding agent based on regenerated micro powder comprises the following components in parts by mass:
uniformly mixing 5 parts of regenerated micro powder, 40 parts of low-temperature calcined regenerated micro powder, 20 parts of amorphous calcium aluminate, 10 parts of gypsum, 15 parts of granulated blast furnace slag powder, 10 parts of steel slag powder, 0.2 part of polycarboxylic acid water reducing agent and 0.01 part of aluminum stearate to prepare the regenerated micro powder composite expanding agent. Then replacing 5% (mass percent) of cement with the regenerated micropowder composite expanding agent, and measuring the 7d limited expansion rate of the cement-based material to be 280 multiplied by 10 under the curing condition that the temperature is 20 +/-2 ℃ and the relative humidity is 60 +/-5% -6 。
Example 2
A composite expanding agent based on regenerated micro powder comprises the following components in parts by mass:
uniformly mixing 10 parts of regenerated micro powder, 30 parts of low-temperature calcined regenerated micro powder, 30 parts of amorphous calcium aluminate, 20 parts of gypsum, 5 parts of granulated blast furnace slag powder, 5 parts of steel slag powder, 0.3 part of naphthalene water aqua and 0.05 part of cellulose ether to prepare the regenerated micro powder composite expanding agent. Then the regenerated micro-powder composite expanding agent is substituted for 12 percent
(mass percent) after the cement is added, under the curing condition that the temperature is 20 +/-2 ℃ and the relative humidity is 60 +/-5 percent, the 7d limited expansion rate of the cement-based material is measured to be 460 multiplied by 10 -6 。
Example 3
A composite expanding agent based on regenerated micro powder comprises the following components in parts by mass:
uniformly mixing 5 parts of regenerated micro powder, 60 parts of low-temperature calcined regenerated micro powder, 20 parts of amorphous calcium aluminate, 5 parts of gypsum, 5 parts of granulated blast furnace slag powder, 5 parts of steel slag powder, 0.2 part of polycarboxylic acid water agent and 0.02 part of cellulose ether to prepare the regenerated micro powder composite expanding agent. Then replacing 15 percent (mass percentage) of cement with the regenerated micro-powder composite expanding agent, and measuring the 7d limited expansion rate of the cement-based material to be 500 multiplied by 10 under the curing condition that the temperature is 20 +/-2 ℃ and the relative humidity is 60 +/-5 percent -6 。
Example 4
A composite expanding agent based on regenerated micro powder comprises the following components in parts by mass:
uniformly mixing 5 parts of regenerated micro powder, 40 parts of low-temperature calcined regenerated micro powder, 35 parts of amorphous calcium aluminate, 5 parts of gypsum, 10 parts of granulated blast furnace slag powder, 5 parts of steel slag powder, 0.4 part of naphthalene water aqua and 0.03 part of aluminum stearate to prepare the regenerated micro powder composite expanding agent. Then replacing 8 percent (mass percent) of cement with the regenerated micro-powder composite expanding agent, and measuring the 7d limited expansion rate of the cement-based material to be 200 multiplied by 10 under the curing condition that the temperature is 20 +/-2 ℃ and the relative humidity is 60 +/-5 percent -6 。
Comparative example 1
A composite expanding agent based on regenerated micro powder comprises the following components in parts by mass:
40 parts of low-temperature calcined regenerated micro powder, 30 parts of amorphous calcium aluminate, 15 parts of gypsum, 5 parts of granulated blast furnace slag powder, 10 parts of steel slag powder, 0.3 part of naphthalene water reducer and 0.04 part of cellulose ether are uniformly mixed to prepare the regenerated micro powder composite expanding agent. Then replacing 10% cement with the regenerated micropowder composite expanding agent, and measuring the 7d limited expansion rate of the cement-based material to be 80 multiplied by 10 under the curing conditions that the temperature is 20 +/-2 ℃ and the relative humidity is 60 +/-5% -6 。
Comparative example 2
A composite expanding agent based on regenerated micro powder comprises the following components in parts by mass:
60 parts of low-temperature calcined regenerated micro powder, 20 parts of gypsum, 10 parts of granulated blast furnace slag powder, 10 parts of steel slag powder, 0.3 part of naphthalene water reducer and 0.04 part of cellulose ether are uniformly mixed to prepare the regenerated micro powder composite expanding agent. Then replacing 10% cement with regenerated micropowder composite expanding agent, and making it be relatively wet at 20 +/-2 deg.CUnder the curing condition with the degree of 60 +/-5 percent, the 7d limited expansion rate of the cement-based material is measured to be-200 multiplied by 10 -6 。
Comparative example 3
A composite expanding agent based on regenerated micro powder comprises the following components in parts by mass:
uniformly mixing 40 parts of amorphous calcium aluminate, 20 parts of gypsum, 20 parts of granulated blast furnace slag powder, 20 parts of steel slag powder, 0.3 part of polycarboxylic acid water reducing agent and 0.02 part of aluminum stearate to prepare the regenerated micro-powder composite expanding agent. Then replacing 15% cement with the regenerated micropowder composite expanding agent, and measuring the 7d limited expansion rate of the cement-based material to be-50 multiplied by 10 under the curing conditions that the temperature is 20 +/-2 ℃ and the relative humidity is 60 +/-5% -6 。
Comparative example 4
A composite expanding agent based on regenerated micro powder comprises the following components in parts by mass:
uniformly mixing 45 parts of regenerated micro powder, 20 parts of amorphous calcium aluminate, 10 parts of gypsum, 15 parts of granulated blast furnace slag powder, 10 parts of steel slag powder, 0.2 part of polycarboxylic acid water reducing agent and 0.01 part of aluminum stearate to prepare the regenerated micro powder composite expanding agent. Then replacing 5% (mass percent) of cement with the regenerated micropowder composite expanding agent, and measuring the 7d limited expansion rate of the cement-based material to be-170 multiplied by 10 under the curing condition that the temperature is 20 +/-2 ℃ and the relative humidity is 60 +/-5% -6 。
Comparative example 5
A composite expanding agent based on regenerated micro powder comprises the following components in parts by mass:
uniformly mixing 25 parts of regenerated micro powder, 40 parts of low-temperature calcined regenerated micro powder, 10 parts of gypsum, 15 parts of granulated blast furnace slag powder, 10 parts of steel slag powder, 0.2 part of polycarboxylic acid water reducing agent and 0.01 part of aluminum stearate to prepare the regenerated micro powder composite expanding agent. Then replacing 5% (mass percent) of cement with the regenerated micro-powder composite expanding agent, and measuring the 7d limited expansion rate of the cement-based material to be 350 multiplied by 10 under the curing conditions that the temperature is 20 +/-2 ℃ and the relative humidity is 60 +/-5 percent -6 。
Comparative example 6 conventional Cement-based expansive agent
After 8 percent (mass percentage) of cement is replaced by the calcium sulphoaluminate and calcium oxide composite concrete expanding agent, under the curing condition that the temperature is 20 +/-2 ℃ and the relative humidity is 60 +/-5 percent, the 7d limited expansion rate of the cement-based material is 100 multiplied by 10 -6 。
The performance of the composite expanding agents of examples 1-4 and comparative examples 1-6 is tested by referring to national specifications GB/T17671-2021 Cement mortar Strength test method (ISO method), JC4762017 concrete expanding agent and GB/T50082-2009 Standard test method for Long-term Performance and durability of ordinary concrete, and the test results are shown in Table 1 below.
TABLE 1 determination of the properties of the recycled micropowder composite expanding agent
The results in Table 1 show that the initial setting times of examples 1 to 4 are improved by 29% or more, the 3d compressive strength is improved by 25% or more, and the 7d restricted expansion ratio is from-250X 10 -6 Lifting to 500X 10 -6 The sulfate erosion resistance is significantly enhanced.
As can be seen from the comparative examples and examples, when Portland cement is blended with cement containing C 2 S-C 12 A 7 -CaSO 4 After regenerating the micropowder expanding agent of (2), Ca (OH) 2 And C 12 A 7 Liberation of Al (OH) 4- Reaction to form C 3 AH 6 And ettringite, accelerate the hydration reaction of the silicate cement and breakC 3 S、C 2 S and Ca (OH) 2 The solid-liquid balance of the solution shortens the setting time and improves the early strength of the hardened slurry. Therefore, after 5 to 15 percent of silicate cement is replaced by the regenerated micro-powder composite expanding agent, the hydration process can be mutually promoted, the hydration of the cement and the formation of a hardened slurry structure are accelerated, the physical and mechanical properties of the hardened slurry, namely mortar and concrete, are improved, and the shrinkage is reduced in the hydration process of calcium oxide crystals and the formation process of ettringite crystals, so that the micro-expansion cement-based material is formed.
The composite expansion agent of comparative example 1 lacks the regenerated fine powder, and although only ettringite and calcium hydroxide are formed in the system, the micro-expansion effect is not sustained because of no stabilizing effect of calcium carbonate (limestone) in the regenerated fine powder on ettringite, and finally the shrinkage effect is exhibited for 7 d.
The composite expanding agent of comparative example 2 lacks amorphous calcium aluminate and regenerated micropowder, and although calcium hydroxide is formed in the system, the micro-expansion effect cannot be achieved due to the low content of calcium oxide in the regenerated micropowder calcined at low temperature, and finally the shrinkage effect is still exhibited in 7 d.
The composite expanding agent of comparative example 3 lacks of low-temperature calcined regenerated micro powder and regenerated micro powder, although ettringite is formed in the system, due to lack of the stabilizing effect of calcium carbonate on ettringite and the expansion effect of calcium hydroxide generated by calcium oxide in calcined regenerated micro powder, the micro-expansion effect cannot be achieved, and finally 7d still presents the contraction effect.
The XRD spectra of the cement hardened slurry with different composite expanding agent mixing amounts in examples 1, 2 and 3 and comparative example 2 of the invention are shown in figure 3, when the composite expanding agent is mixed in the cement, the hydration product is basically consistent with pure silicate cement, but the characteristic peaks of calcium hydroxide and ettringite in examples 1, 2 and 3 are obviously enhanced. The results show that a moderate amount of the composite swelling agent greatly accelerates the hydraulic mineral C 3 S and C 2 The hydration of S improves the hydration degree of cement, increases the content of ettringite in the hydrated slurry, and has no amorphous calcium aluminate and obviously reduced ettringite generation amount in the comparative example 2.
Practice of the inventionIn example 1, when the composite expanding agent lacks the low-temperature calcined regenerated fine powder or amorphous calcium aluminate, respectively, the composite expanding agent does not achieve the effect of micro-expansion, mainly lacks C 2 S and C 12 A 7 The synergistic hydration effect of the compound expanding agent, and the expansion efficiency of the compound expanding agent can not be greatly shown.
Compared with the comparative example 6, the common cement-based composite expanding agent disclosed by the invention has the advantages that the micro-expansion effect is weaker in 7 days, and the composite expanding agent disclosed by the invention has the advantages of high setting speed, high strength, continuous expansion efficiency and obvious advantages.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications of the invention may be made without departing from the spirit or scope of the invention.
Claims (10)
1. The composite expanding agent based on the regenerated micro powder is characterized by comprising the following components: regenerated micro powder, low-temperature calcined regenerated micro powder, granulated blast furnace slag powder, steel slag powder, amorphous calcium aluminate, gypsum, a dispersing agent and a water reducing agent.
2. The composite expanding agent as claimed in claim 1, wherein the regenerated micropowder composite expanding agent consists of the following components in parts by mass: 5-10 parts of regenerated micro powder, 30-60 parts of low-temperature calcined regenerated micro powder, 5-15 parts of granulated blast furnace slag powder, 5-10 parts of steel slag powder, 20-40 parts of amorphous calcium aluminate, 5-20 parts of gypsum, 0.01-0.05 part of dispersing agent and 0.1-0.4 part of water reducing agent.
3. The composite expanding agent as claimed in claim 1, wherein the regenerated micro powder is a fine powder obtained by crushing and collecting concrete, and the fineness of the fine powder is less than or equal to 75 μm.
4. The composite expanding agent as claimed in claim 1, wherein the low-temperature calcined regenerated micro powder is obtained by low-temperature calcining of fine powder collected by concrete crushing; the low temperature range is 650-800 ℃.
5. The composite expanding agent as claimed in claim 4, wherein the time of the low-temperature calcination is 60-90 min.
6. The composite expanding agent as claimed in claim 1, wherein the amorphous calcium aluminate has a specific surface area of 500m or more 2 /kg。
7. The composite expanding agent of claim 1, wherein the water reducing agent is a polycarboxylic acid high-efficiency water reducing agent and/or a naphthalene high-efficiency water reducing agent.
8. The composite expanding agent as claimed in claim 1, wherein the water reducing rate of the water reducing agent is not less than 30%.
9. The composite expanding agent of claim 1, wherein the dispersing agent is aluminum stearate and/or a cellulose ether.
10. A method for preparing the composite expanding agent according to any one of claims 1 to 9, comprising the steps of: uniformly mixing the regenerated micro powder, the low-temperature calcined regenerated micro powder, the granulated blast furnace slag powder, the steel slag powder, the amorphous calcium aluminate, the gypsum, the water reducer and the dispersant to obtain the composite expanding agent.
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