CN108751811B - Preparation method of concrete without negative strength influence and high internal curing efficiency - Google Patents

Preparation method of concrete without negative strength influence and high internal curing efficiency Download PDF

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CN108751811B
CN108751811B CN201810580775.9A CN201810580775A CN108751811B CN 108751811 B CN108751811 B CN 108751811B CN 201810580775 A CN201810580775 A CN 201810580775A CN 108751811 B CN108751811 B CN 108751811B
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concrete
water
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mass
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杨进
贺行洋
苏英
王发洲
郑正旗
黄健翔
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Hubei University of Technology
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    • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
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    • C04B18/00—Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
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    • C04B24/14—Peptides; Proteins; Derivatives thereof
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    • C04B24/00—Use of organic materials as active ingredients for mortars, concrete or artificial stone, e.g. plasticisers
    • C04B24/24—Macromolecular compounds
    • C04B24/26—Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
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    • C04B24/24—Macromolecular compounds
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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
    • C04B40/0028—Aspects relating to the mixing step of the mortar preparation
    • C04B40/0039—Premixtures of ingredients
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    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
    • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
    • C08F220/52—Amides or imides
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    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
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    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J3/00—Processes of treating or compounding macromolecular substances
    • C08J3/02—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques
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    • C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
    • C04B2201/50—Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength
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    • C08J2333/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers
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Abstract

The invention discloses a preparation method of concrete without negative strength influence and high internal curing efficiency, which adopts the technical scheme that a skeleton structure curing agent is firstly subjected to pre-water absorption, then is premixed with river sand and gravel, and finally is sequentially added with cement and the balance of water and is uniformly stirred to obtain the concrete; the preparation method of the framework structure curing agent comprises the following steps of uniformly mixing raw material powder, a pore regulator and water to obtain a raw material mass, and drying, calcining and crushing to obtain the porous rigid PM framework; and (3) immersing the porous rigid PM framework into liquid SAP gel for loading, and then drying to obtain the framework structure curing agent with the rigid framework structure. The invention has simple and reliable process, low production cost, high maintenance efficiency and no negative effect of strength.

Description

Preparation method of concrete without negative strength influence and high internal curing efficiency
Technical Field
The invention relates to the field of building materials, in particular to a preparation method of concrete without negative strength influence and high internal curing efficiency.
Background
Concrete is one of the most important civil engineering materials at present, and the development of high performance is the main direction of the development of concrete materials. It is predicted that concrete will remain the most dominant engineering material and High Performance Concrete (HPC) will dominate over the next 100 years or more.
Although the special raw material system and structural characteristics of the high-performance concrete make the performance of the high-performance concrete superior to that of common concrete, the high-performance concrete also brings inherent problems. Compared with common concrete, the high-performance concrete has the characteristics of high cementing material dosage, low water-cement ratio, high sand rate and the like. The water-cement ratio of ordinary concrete is generally more than 0.38, while the water-cement ratio of high-performance concrete is generally between 0.20 and 0.38, and the water-cement ratio range cannot meet the requirement of sufficient hydration of cement. The characteristics of high early hydration speed, high self-drying degree and large self-shrinkage of the high-performance concrete are determined by the higher consumption of the cementing material and the lower water-to-gel ratio of the high-performance concrete, and then the problems of poor early stability, easy cracking and the like are caused. In addition, due to the characteristics of low water-gel ratio and compact structure of the high-performance concrete, external curing moisture is difficult to enter the interior of the concrete, so that the internal relative humidity is low, and the problems of water loss cracking, early cracking and the like are more prominent when the early curing is insufficient. The shrinkage cracking of the concrete can cause a series of problems of structure leakage, external erosion, strength reduction and the like, and even influence the long-term service of the concrete structure. Aiming at the problems, the development of the research on the shrinkage and crack resistance of the high-performance concrete is of great significance.
At present, the main technical means for solving the shrinkage cracking of concrete mainly comprise an expanding agent, an organic shrinkage reducing agent, internal curing, surface spraying and covering, fiber toughening and the like. However, the expanding agent still has the problems of strict requirements on moisture, adaptability to concrete and the like at present, and the organic shrinkage reducing agent also has the problems of low early strength, high cost and the like at present. For the external curing methods of spraying, covering and curing the surface, such as spraying, curing the surface, covering the surface, coating organic solvent on the surface and the like from outside to inside, because the high-performance concrete structure is compact, the problems of self-shrinkage, self-drying shrinkage and the like caused by insufficient internal humidity of the concrete are difficult to essentially solve by the external curing methods. The fiber toughening mainly plays a role in reducing concrete shrinkage through the constraint action of the fibers, and the self-drying problem in high-performance concrete cannot be fundamentally solved.
The internal curing technology is mainly characterized in that water is supplemented into the concrete through internal curing media (such as ceramic sand and super absorbent resin), the additional water does not exist in a mode of simply increasing the water-cement ratio, and the additional water is gradually released through the internal curing media, so that the internal relative humidity of the concrete is compensated, the self-drying is delayed, and the problem of large self-shrinkage of the high-performance concrete is fundamentally solved. However, the currently commonly used internal curing medium, Super Absorbent Polymer (SAP), is susceptible to the action of osmotic pressure of cement pore solution ions inside concrete, and water inside the SAP is released too quickly and too early and is difficult to regulate, resulting in low internal curing efficiency; and the macro-voids left after the SAP releases water tend to cause a significant decrease in concrete strength. The other common internal curing medium ceramic sand (LWA) mainly has too low water absorption rate (5% -30%), and the internal curing efficiency is difficult to ensure; meanwhile, the porous ceramic sand has negative influence on the strength of the concrete material.
Therefore, there is an urgent need to develop an internal curing concrete material having high internal curing efficiency without adverse effects of strength.
Disclosure of Invention
The invention aims to solve the technical problems and provides a preparation method of concrete with no negative strength influence and high internal curing efficiency, which has the advantages of simple and reliable process, low production cost, high internal curing efficiency and no negative strength effect.
The technical scheme includes that the skeleton structure curing agent is pre-absorbed with water, then is pre-mixed with river sand and gravel, and finally cement and the balance water are sequentially added and uniformly stirred to obtain concrete; the additive amount of the skeleton structure curing agent accounts for 0.1-0.5% of the mass of the concrete, and the preparation method of the skeleton structure curing agent comprises the following steps:
(1) uniformly mixing raw material powder, a pore regulator and water to obtain a raw material mass, and drying, calcining and crushing to obtain a porous rigid PM framework;
(2) and (3) immersing the porous rigid PM framework into the liquid SAP gel for loading and assembling, and then drying to obtain the framework structure curing agent with the rigid framework structure.
Comprises the following components in percentage by weight: 0.1-0.5% of skeleton structure curing agent, 13-24% of cement, 27-31% of river sand, 43-50% of gravel and 5.5-5.9% of water, wherein the total mass percentage is 100%.
In the step (1), the additive of the pore regulator in the raw material dough accounts for 10-50%, the water accounts for 20%, and the balance is raw material powder.
In the step (1), the raw material powder is at least one of clay, shale, silt sludge and silicon-aluminum industrial waste residues; the pore regulator is at least one of carbon particles, organic fibers, EPS foam particles and plant fibers.
In the step (1), the calcination temperature is 800-1200 ℃, and the time is 30min-2 h.
In the step (1), the average particle size of the porous rigid PM framework is 5 μm-20 mm.
In the step (1), the obtained porous rigid PM framework is modified, and the modification method comprises the following steps: and soaking the porous rigid PM framework in NaOH solution, then cleaning with fresh water, soaking in a surface modifier, and drying to obtain the surface modified PM framework.
In the step (1), the concentration of the NaOH solution is 1-4 mol/L; the surface modifier is silane coupling agent solution with the concentration of 0.5-1.5% by mass.
In the step (1), the soaking time of the porous rigid PM framework in the NaOH solution is 48-96h, and the soaking time in the surface modifier is 18-36 h.
In the step (2), the preparation method of the liquid SAP gel comprises the following steps: and mixing and reacting the monomer, the cross-linking agent and the initiator to obtain the liquid SAP gel.
The monomer is at least one of acrylic acid, acrylamide, sodium alginate and feather protein; the cross-linking agent is N, N' -methylene bisacrylamide, and the addition amount of the cross-linking agent is 0.02-0.1% of the mass of the monomer; the initiator is potassium persulfate, and the addition amount of the initiator is 0.1-0.2% of the mass of the monomer.
The water release nature of the SAP material is aimed at, namely the SAP is directly contacted with a cement matrix pore solution (containing complex ions) after being doped into cement concrete, so that the water in the SAP material is too quickly and prematurely released under the driving of the ion osmotic pressure. According to the method, a pore regulator is added into raw material powder to form pores, a porous rigid PM framework is obtained through drying, calcining, crushing and sintering, and liquid SAP gel is loaded and assembled in the porous rigid PM framework to obtain the framework structure curing agent with a rigid framework structure. The loading process enables the SAP gel to fully enter each level of pores of the porous rigid PM framework, after the cement matrix is added, the water release environment of the SAP in the cement matrix can be changed based on the PM/SAP composite structure, and multiple water release regulation and high water retention of the PM/SAP structure are realized by utilizing gradient physical water release of the porous rigid PM framework and chemical regulation water release of the SAP. The SAP gel is loaded and assembled in the PM framework to form a unique alternate assembly composite structure, compared with the traditional internal maintenance medium (ceramic sand and SAP), the novel internal maintenance composite structure has the characteristics of high water absorption rate, high water retention and high mechanical strength, and the inherent defects of low water absorption rate and poor water retention of the traditional ceramic sand and the traditional SAP gel are overcome.
Furthermore, the raw material powder can be selected from a silica-alumina sinterable material for preparing a composite material with a porous rigid framework, which can be listed as at least one of clay, shale, silt and silica-alumina industrial waste residues, and preferably clay and shale; the pore regulator is not particularly limited, and may be at least one of carbon particles, organic fibers, EPS foam particles and plant fibers, preferably carbon particles (50nm or more and 500 μm or less in average particle size) and organic fibers (with any aspect ratio) are used in combination, in order to ensure sufficient porosity, the additive of the pore regulator in the raw dough accounts for 10 to 50 mass%, too much leads to insufficient mechanical strength and rigidity of the rigid skeleton, too little leads to insufficient pores of the rigid skeleton and poor loading effect of SAP gel, and the porosity of the prepared porous rigid PM skeleton is preferably controlled to 20 to 70%.
In order to improve the rigidity of the framework as much as possible, the calcination temperature is preferably controlled to be 800-1200 ℃ and the time is preferably controlled to be 30min-2h, the problems of mutual adhesion, cracking, surface hole sealing and the like of the rigid framework can be caused by overhigh temperature or overlong time, and the problems of insufficient porosity, poor internal connectivity, low mechanical strength and the like of the rigid framework can be caused by overlow temperature or overlong time. The porous rigid PM framework is obtained by crushing to an average particle size of 5 μm to 20mm, and the particle size is controlled in such a range that it is considered that too small a particle size results in a limited loading amount of the liquid SAP gel and too large a particle size results in too long a loading time.
Furthermore, preferably, the porous rigid PM framework is modified, then the liquid SAP gel is loaded and assembled in the porous rigid PM framework, and the total amount of chemical groups such as hydroxyl groups exposed on the surface of the pores of the rigid PM framework is increased through modification, so that the liquid SAP gel can be chemically bonded with the surface of the inner pores after entering the rigid PM framework, is assembled by itself, improves the adhesive force of the liquid SAP gel, and effectively ensures the stability of the interpenetration composite structure of the PM-SAP material; the mass ratio of the porous rigid PM framework to the liquid SAP gel after loading can be any, and is preferably 7-3: 3-7.
Has the advantages that:
firstly, the skeleton structure curing agent is added into the concrete, and the physical and chemical multiple water release regulation and control of the skeleton structure curing agent can avoid the too fast release of early free water. The liquid resin gel is inserted, loaded and assembled in the porous rigid PM framework with the hierarchical porous structure, so that the complete contact between the SAP gel and the cement matrix can be avoided, the water release environment of the SAP gel in the cement matrix is changed by regulating the contact proportion between the SAP gel and the cement matrix, and the early-stage free water is prevented from being released too fast; on the other hand, the porous rigid PM framework has a hierarchical pore structure, can absorb water through physical capillary to store a part of water, and plays a physical regulation and control role of sequentially releasing water from large pores to small pores under the action of capillary negative pressure. Finally, based on gradient physical water release of the hierarchical porous high-strength framework and chemical regulation water release of the SAP gel, multiple water release regulation of the framework structure curing agent and efficient utilization of internal curing water are realized.
Secondly, a high-strength framework left after the framework structure curing agent releases water can play a bearing role, negative influences of existing SAP water release macro pores on mechanics are eliminated, hundreds of micron-sized macro pores are left in all existing SAP materials after water is released in a cement matrix, and finally the strength of cement concrete is obviously reduced; because the SAP gel is loaded in the porous high-strength framework, the high-strength bearing framework is left after water release and shrinkage of the framework structure curing agent, thereby avoiding the generation of macroscopic holes for water release in a cement matrix, and meanwhile, the high-strength framework left by the water release of the framework structure curing agent can play a role in mechanical bearing, thereby eliminating the negative influence of the macroscopic holes for mechanics caused by the existing SAP water release.
Third, a reinforced interfacial region may be formed around the skeletal structure curing agent. The porous high-strength skeleton left after the skeleton structure curing agent releases water can form a mechanical interlocking structure with the surrounding cement matrix, and meanwhile, the hydration degree and compactness of the surrounding cement paste can be improved through the water releasing curing effect of the skeleton structure curing agent. Under the combined action of a mechanical interlocking structure formed by the high-strength framework and the cement matrix and SAP gel water release maintenance, a reinforced interface area can be formed around the porous framework, so that the negative influence of diffusion communication holes formed by SAP early quick water release on impermeability can be avoided, and mechanical contribution can be generated.
Drawings
FIG. 1 is a schematic structural view of the framework structure curing agent of the present invention in the interior of concrete.
Detailed Description
The present invention will be further described with reference to the following examples, but the present invention is not limited to the following examples.
Skeleton structure curing agent example 1:
1) adding water into clay powder and a pore regulator (carbon powder with the average particle size of 100 mu m and polypropylene fiber with the diameter of 30 mu m) to mix to form a raw material cluster (the carbon powder and the polypropylene fiber both account for 15 percent of the mass of the raw material cluster and the water accounts for 20 percent of the mass of the raw material cluster), preheating, drying, calcining for 1h at the temperature of 800-;
2) soaking the PM framework prepared in the step 1) in 2mol/L NaOH solution for 72h, cleaning the PM framework by fresh water, soaking the PM framework in 1% silane coupling agent solution for 24h, and drying to obtain a surface modified porous PM framework;
3) uniformly stirring a monomer (acrylic acid), a cross-linking agent (N, N' -methylene bisacrylamide, the dosage of which is 0.06 percent of the mass of the monomer) and an initiator (potassium persulfate, the dosage of which is 0.15 percent of the mass of the monomer) by adopting a conventional sol-gel method, and reacting for 4 hours in a constant-temperature water bath at 50 ℃ to obtain liquid SAP gel;
4) and (3) carrying out vacuum load assembly (the vacuum degree is 100mbar, the holding time is 30min) on the surface modified porous PM framework obtained in the step 2) in the liquid SAP gel obtained in the step 3), and drying (the temperature is 50 ℃, the time is 24 hours) to obtain the framework structure curing agent 1 with the rigid framework structure.
Skeleton structure curing agent example 2:
1) adding water into shale powder and a pore regulator (EPS foam particles with the average particle size of 500 mu m and waste paper plant fibers with the diameter of 50 mu m) to mix so as to form a raw material cluster (the carbon powder and the polypropylene fibers respectively account for 10 percent and 40 percent of the mass of the raw material cluster, and the water accounts for 20 percent of the mass of the raw material cluster), preheating, drying, calcining for 2 hours at the temperature of 800 plus 1200 ℃, and crushing so as to obtain a porous rigid PM framework (the average particle size is 4mm-20mm) with high strength, high communication rate and hierarchical pore structure;
2) soaking the PM framework prepared in the step 1) in 1mol/L NaOH solution for 72h, cleaning the PM framework by fresh water, soaking the PM framework in 1.5% silane coupling agent solution for 24h, and drying to obtain a surface modified porous PM framework;
3) uniformly stirring monomers (acrylic acid and acrylamide in a ratio of 4:6), a cross-linking agent (N, N' -methylene bisacrylamide, the dosage of which is 0.1 percent of the mass of the monomers), an initiator (potassium persulfate, the dosage of which is 0.2 percent of the mass of the monomers) by adopting a conventional sol-gel method, and reacting in a constant-temperature water bath at 50 ℃ for 4 hours to obtain liquid SAP gel;
4) and (3) carrying out vacuum load assembly (the vacuum degree is 100mbar, the holding time is 30min) on the surface modified porous PM framework obtained in the step 2) in the liquid SAP gel obtained in the step 3), and drying (the temperature is 50 ℃, the time is 24 hours) to obtain the framework structure curing agent 2.
Skeleton structure curing agent example 3:
1) adding water into shale powder and a pore regulator (carbon powder with the average particle size of 50nm and polypropylene fiber with the diameter of 15 mu m) to mix so as to form a raw material cluster (the carbon powder and the polypropylene fiber respectively account for 20 percent and 10 percent of the mass of the raw material cluster, and the water accounts for 20 percent of the mass of the raw material cluster), preheating, drying, calcining for 2 hours at the temperature of 800-;
2) soaking the PM framework prepared in the step 1) in a 4mol/L NaOH solution for 72h, cleaning the PM framework by fresh water, soaking the PM framework in a silane coupling agent solution with the mass concentration of 0.5% for 24h, and drying to obtain a surface modified porous PM framework;
3) uniformly stirring a monomer (acrylamide), a cross-linking agent (N, N' -methylene bisacrylamide, the dosage of which is 0.02 percent of the mass of the monomer) and an initiator (potassium persulfate, the dosage of which is 0.1 percent of the mass of the monomer) by adopting a conventional sol-gel method, and reacting for 4 hours in a constant-temperature water bath at 50 ℃ to obtain liquid SAP gel;
4) and (3) carrying out vacuum load assembly (the vacuum degree is 100mbar, the holding time is 30min) on the surface modified porous PM framework obtained in the step 2) in the liquid SAP gel obtained in the step 3), and drying (the temperature is 50 ℃, the time is 24 hours) to obtain the framework structure curing agent 3.
Skeleton structure curing agent example 4:
1) adding water into the sludge and a pore regulator (carbon powder with the average particle size of 250 mu m and polypropylene fiber with the diameter of 50 mu m) to mix to form a raw material cluster (the carbon powder and the polypropylene fiber both account for 5 percent of the mass of the raw material cluster, and the water accounts for 20 percent of the mass of the raw material cluster), preheating, drying, calcining for 30min at the temperature of 800-1200 ℃, and crushing to obtain a porous rigid PM framework (with the average particle size of 5 mu m-20mm) with high strength, high connectivity and a hierarchical pore structure;
2) soaking the PM framework prepared in the step 1) in 2mol/L NaOH solution for 72h, cleaning the PM framework by fresh water, soaking the PM framework in 1% silane coupling agent solution for 24h, and drying to obtain a surface modified porous PM framework;
3) uniformly stirring a monomer (acrylic acid and acrylamide in a ratio of 2:8), a cross-linking agent (N, N' -methylene bisacrylamide, the dosage of which is 0.05 percent of the mass of the monomer), an initiator (potassium persulfate, the dosage of which is 0.15 percent of the mass of the monomer) by adopting a conventional sol-gel method, and reacting in a constant-temperature water bath at 50 ℃ for 4 hours to obtain liquid SAP gel;
4) and (3) carrying out vacuum load assembly (the vacuum degree is 100mbar, the holding time is 30min) on the surface modified porous PM framework obtained in the step 2) in the liquid SAP gel obtained in the step 3), and drying (the temperature is 50 ℃, the time is 24 hours) to obtain the framework structure curing agent 4.
Skeleton structure curing agent example 5:
1) adding water into the silicon-aluminum industrial waste residue (specifically, fly ash), a pore regulator (carbon powder with the average particle size of 500 mu m and polypropylene fiber with the diameter of 100 mu m) and mixing to form a raw material cluster (the carbon powder and the polypropylene fiber respectively account for 40 percent and 5 percent of the mass of the raw material cluster, and the water accounts for 20 percent of the mass of the raw material cluster), preheating, drying, calcining for 1 hour within the range of 800 plus one year and 1200 ℃, and crushing to obtain a porous rigid PM framework (the average particle size is 10mm-20mm) with high strength, high communication rate and hierarchical pore structure;
2) soaking the PM framework prepared in the step 1) in a 4mol/L NaOH solution for 72h, cleaning the PM framework by adopting fresh water, soaking the PM framework in a silane coupling agent solution with the mass concentration of 1.5% for 24h, and drying to obtain a surface modified porous PM framework;
3) uniformly stirring a monomer (sodium alginate), a cross-linking agent (N, N' -methylene bisacrylamide, the dosage of which is 0.1 percent of the mass of the monomer) and an initiator (potassium persulfate, the dosage of which is 0.2 percent of the mass of the monomer) by adopting a conventional sol-gel method, and reacting for 4 hours in a constant-temperature water bath at 50 ℃ to obtain liquid SAP gel;
4) and (3) carrying out vacuum load assembly (the vacuum degree is 100mbar, the holding time is 30min) on the surface modified porous PM framework obtained in the step 2) in the liquid SAP gel obtained in the step 3), and drying (the temperature is 50 ℃, the time is 24 hours) to obtain the framework structure curing agent 5.
Skeleton structure curing agent example 6:
1) adding water into clay powder, shale powder and a pore regulator (carbon powder with the average particle size of 500 mu m and polypropylene fiber with the diameter of 100 mu m) for mixing to form a raw material cluster (the clay powder, the shale powder and the polypropylene fiber respectively account for 40 percent and 5 percent of the mass of the raw material cluster, the water accounts for 20 percent of the mass of the raw material cluster, and the ratio of the clay powder to the shale powder is 1:1), preheating, drying, calcining for 2 hours at the temperature of 800 plus 1200 ℃, and crushing to obtain a porous rigid PM framework (the average particle size is 5 mu m-4mm) with high strength, high communication rate and hierarchical pore structure;
2) soaking the PM framework prepared in the step 1) in a 4mol/L NaOH solution for 72h, cleaning the PM framework by adopting fresh water, soaking the PM framework in a silane coupling agent solution with the mass concentration of 1.5% for 24h, and drying to obtain a surface modified porous PM framework;
3) uniformly stirring a monomer (feather protein powder), a cross-linking agent (N, N' -methylene bisacrylamide, the dosage of which is 0.1 percent of the mass of the monomer) and an initiator (potassium persulfate, the dosage of which is 0.2 percent of the mass of the monomer) by adopting a conventional sol-gel method, and reacting for 4 hours in a constant-temperature water bath at 50 ℃ to obtain liquid SAP gel;
4) and (3) carrying out vacuum load assembly (the vacuum degree is 100mbar, the holding time is 30min) on the surface modified porous PM framework obtained in the step 2) in the liquid SAP gel obtained in the step 3), and drying (the temperature is 50 ℃, the time is 24 hours) to obtain the framework structure curing agent 6.
Comparative example 1:
the traditional internal curing medium, shale ceramic sand, with the particle size of 5 μm-4mm and the water absorption rate of 30% is used as a comparative curing agent 1.
Comparative example 2:
the traditional internal curing medium, polyacrylic acid super absorbent resin, with a particle size of 50-100 μm and a fresh water absorption rate of 150 times, was used as a comparative curing agent 2.
Comparative example 3:
a simple physical mixture of two conventional internal curing media (shale ceramic sand in comparative example 1: polyacrylic acid super absorbent resin in comparative example 2 ═ 1:1) was used as comparative curing agent 3.
The water absorption multiplying power and the water retention rate are tested according to GB/T17431.1-1998 and GB/T22905-2008; the cylinder pressure strength test method refers to GB/T17431.2-1998; the method for obtaining the interface region in the free water content test is described in the publication of Cement and Concrete Research,2016,81: 112-.
Table 1 main properties of the skeleton structure curing agents 1-6 and the comparative curing agents 1-3 (conventional internal curing media):
Figure BDA0001688147900000101
Figure BDA0001688147900000111
as can be seen from Table 1, the skeleton-structure curing agents 1 to 6 have the characteristics of high water absorption rate, high water retention and high mechanical strength, and the performance thereof is superior to that of the conventional internal curing medium (comparative curing agent 1, comparative curing agent 2 and comparative curing agent 3).
Concrete examples 1 to 6:
the prepared curing agents with the skeleton structures 1-6 are respectively pre-absorbed with water, then are premixed with river sand and gravel, finally cement and the balance water are sequentially added and are uniformly stirred, and concrete 1-6 is obtained respectively, wherein the addition amount of each component is shown in table 2.
Table 2 concrete examples 1-6 each component addition (weight percent):
Figure BDA0001688147900000112
concrete comparative example 1:
comparative concrete 1 was obtained in the same manner as in example 1 except that the skeletal structure curing agent was not added to the raw materials.
Comparative concrete example 2:
comparative concrete 2 was obtained in the same manner as in example 2 except that the skeletal structure curing agent was not added to the raw materials.
Comparative concrete example 3:
comparative concrete 3 was obtained in the same manner as in example 1 except that the skeleton structure curing agent was not added to the raw materials, and 0.5 mass% of an acrylic super absorbent resin (SAP, having a water absorption capacity of 150 in deionized water) was added thereto.
Comparative concrete example 4:
the comparative concrete 4 was prepared in the same manner as in example 1 except that the raw material was not added with the skeletal structure curing agent but added with shale pottery sand (particle size 5 μm-4mm, water absorption capacity 30%) in an amount of 0.5% by mass.
Concrete comparative example 5:
the raw materials were not added with a skeleton structure curing agent, but were added with a simple physical mixture (0.5% by mass) of shale ceramic sand (particle size 5 μm-4mm, water absorption rate 30%) and acrylic super absorbent resin (particle size 50-100 μm, water absorption rate 150 times), the mass ratio of which was 1:1, and comparative concrete 5 was obtained as in example 1.
The concrete compressive strength refers to GB/T50081-2002; shrinkage and Cl of concrete-The diffusion coefficient and the cracking area are referred to GB/T50082-2009.
TABLE 1 Main Properties of concrete of examples 1 to 6 and comparative examples 1 to 5
Figure BDA0001688147900000121
Figure BDA0001688147900000131
As can be seen from Table 1, the concretes 1 to 6 of different strength grades (C80, C50 and C30) prepared in examples 1 to 6 had lower self-shrinkage and crack area, indicating good internal curing efficiency, and the compressive strength and Cl resistance of the concrete of the present invention were compared with those of the comparative concretes 1 to 5 to which the skeletal structure curing agent of the present invention was not added-The permeability is not affected in any negative way, even improved. Meanwhile, the internal curing concrete of the present invention (example 1) has mechanical properties and Cl resistance, compared to the currently used SAP internal curing (comparative example 3), ceramic sand internal curing (comparative example 4) and SAP and ceramic sand mixed internal curing (comparative example 5)-Has obvious advantages in permeability and higher internal curing efficiency (internal relative humidity, self-contraction)The area of cracking).

Claims (11)

1. A preparation method of concrete without negative strength influence and high internal curing efficiency is characterized in that a skeleton structure curing agent is pre-absorbed with water, then is premixed with river sand and gravel, and finally is sequentially added with cement and the balance of water to be uniformly stirred to obtain concrete; the additive amount of the skeleton structure curing agent accounts for 0.1-0.5% of the mass of the concrete, and the preparation method of the skeleton structure curing agent comprises the following steps:
(1) uniformly mixing raw material powder, a pore regulator and water to obtain a raw material mass, and drying, calcining and crushing to obtain a porous rigid PM framework;
(2) and (3) immersing the porous rigid PM framework into the liquid SAP gel for loading and assembling, and then drying to obtain the framework structure curing agent with the rigid framework structure.
2. The method for preparing concrete with no negative strength influence and high internal curing efficiency according to claim 1, which comprises the following components in percentage by weight: 0.1-0.5% of skeleton structure curing agent, 13-24% of cement, 27-31% of river sand, 43-50% of gravel and 5.5-5.9% of water, wherein the total mass percentage is 100%.
3. The method for preparing concrete having no negative strength influence and high internal curing efficiency as claimed in claim 1 or 2, wherein in said step (1), said additives of pore regulator in raw dough comprise 10-50%, water comprises 20%, and the balance is raw meal.
4. The method for preparing a PM-SAP composite material having a rigid skeleton structure as claimed in claim 1 or 2, wherein in the step (1), the raw material powder is at least one of clay, shale, sludge, and waste residue of alumino-silica industry; the pore regulator is at least one of carbon particles, organic fibers, EPS foam particles and plant fibers.
5. The method for preparing concrete without adverse effect on strength and with high internal curing efficiency as claimed in claim 1 or 2, wherein in the step (1), the calcination temperature is 800-1200 ℃ for 30min-2 h.
6. The method for preparing concrete with no negative strength influence and high internal curing efficiency according to claim 1 or 2, wherein in the step (1), the average particle size of the porous rigid PM framework is 5 μm-20 mm.
7. The method for preparing concrete with no negative strength influence and high internal curing efficiency according to claim 1 or 2, wherein in the step (1), the porous rigid PM framework is modified, and the modification method comprises the following steps: and soaking the porous rigid PM framework in NaOH solution, then cleaning with fresh water, soaking in a surface modifier, and drying to obtain the surface modified PM framework.
8. The method for preparing concrete with no negative strength influence and high internal curing efficiency according to claim 7, wherein in the step (1), the concentration of the NaOH solution is 1-4 mol/L; the surface modifier is silane coupling agent solution with the concentration of 0.5-1.5% by mass.
9. The method for preparing concrete without negative strength influence and high internal curing efficiency according to claim 7, wherein in the step (1), the soaking time of the porous rigid PM framework in NaOH solution is 48-96h, and the soaking time in the surface modifier is 18-36 h.
10. The method for preparing concrete with no negative strength influence and high internal curing efficiency according to claim 7, wherein in the step (2), the liquid SAP gel is prepared by: and mixing and reacting the monomer, the cross-linking agent and the initiator to obtain the liquid SAP gel.
11. The method for preparing concrete with no negative strength influence and high internal curing efficiency as claimed in claim 1, wherein the monomer is at least one of acrylic acid, acrylamide, sodium alginate and feather protein; the cross-linking agent is N, N' -methylene bisacrylamide, and the addition amount of the cross-linking agent is 0.02-0.1% of the mass of the monomer; the initiator is potassium persulfate, and the addition amount of the initiator is 0.1-0.2% of the mass of the monomer.
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CN101898877A (en) * 2010-08-17 2010-12-01 重庆大学 Method for pretreating lightweight aggregate used for internal curing of cement-based materials
CN103193425A (en) * 2013-04-09 2013-07-10 四川省交通运输厅公路规划勘察设计研究院 High-strength pumping anti-crack concrete prepared by slag aggregate and production method of concrete

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CN1683421A (en) * 2005-03-11 2005-10-19 华南理工大学 Silicatel multifunctional organic alkoxy silane cross linked polyacrylate water suction resin and its preparing method
CN101898877A (en) * 2010-08-17 2010-12-01 重庆大学 Method for pretreating lightweight aggregate used for internal curing of cement-based materials
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