CN111635161A - Polycarboxylate-based high-performance water reducer for coarse aggregate with high water absorption and its preparation and application - Google Patents

Abstract

The invention belongs to the field of building material additives, and in particular relates to a polycarboxylic acid-based high-performance water reducer for coarse aggregate concrete with high water absorption, preparation and application thereof. The water reducing agent includes: polycarboxylate superplasticizer I: 4.00%-40.00%, polycarboxylate superplasticizer II: 1.00%-20.00%, defoamer: 0.01%-1.00%, air-entraining agent : 0.00% to 1.00%, retarder: 0.05% to 10.00%, bleeding inhibitor: 0.10% to 2.00%, adsorption inhibitor: 0.00% to 2.00%, and water: 26.00 to 68.00%. The polycarboxylic acid-based high-performance water-reducing agent of the present invention has the characteristics of low air entrainment, high water-reduction, improved concrete homogeneity, suppression of post-bleeding, low shrinkage rate and good slump retention ability, and can be applied to Preparation of coarse aggregate high performance concrete with high water absorption.

Description

Polycarboxylate-based high-performance water reducer for coarse aggregate with high water absorption and its preparation and application

technical field

The invention belongs to the field of building material additives, and in particular relates to a polycarboxylic acid-based high-performance water reducer for coarse aggregate concrete with high water absorption, preparation and application thereof.

Background technique

In recent years, with the popularization and application of high performance concrete, polycarboxylate water reducer has become the only water reducer that can make concrete high performance. Compared with traditional superplasticizers, the new generation of polycarboxylate superplasticizers has excellent properties such as low dosage, high water reducing rate and good slump retention.

In some special geological structural environments, the source of high-quality coarse aggregate is very limited, and the coarse aggregate that can meet the requirements of the national standard is expensive and difficult to supply, and cannot be used on site. Especially in the African continent, the common coarse aggregate can meet the national standard GB/T14685-2011 intermediate gradation, crushing value and other indicators, but the water absorption rate is usually between 2 and 5%, which does not meet the national standard less than 2%. When high water absorption aggregate is used to prepare concrete, under the condition of certain water consumption, the slump of the prepared concrete is smaller than that of ordinary aggregate concrete, and the loss of fluidity over time is large, which is difficult to meet the pumping construction. Second, the water absorbed by the coarse aggregate with high water absorption rate is easy to release the water in the hole under high-intensity vibration, which is easy to cause water marks or even sand lines on the surface of the concrete; third, compared with ordinary aggregate concrete, The use of coarse aggregates with high water absorption will lead to an increase in porosity in concrete, thereby increasing drying shrinkage. Fourth, the concrete after forming and hardening often has many internal defects, and erosive ions are easy to penetrate, which seriously affects its use in marine engineering. service life in the environment.

For aggregate concrete with high water absorption, researches at home and abroad mainly focus on lightweight aggregates and recycled aggregates with high water absorption, such as pre-wetting them to achieve saturated surface dryness, or selecting waterproof polymers for pretreatment. Patent CN103145363A provides a polycarboxylate superplasticizer for recycled aggregate concrete. The prepared polycarboxylate superplasticizer has high water-reducing rate and good dispersibility, and can better adapt to recycled aggregate concrete; CN103172298A invented a special high-efficiency water-reducing agent for recycled aggregate concrete, which can obviously improve the working performance of recycled aggregate concrete, reduce the loss of working performance over time, and at the same time improve the mechanical strength to a certain extent. None of the above patents pay attention to the appearance and drying shrinkage characteristics of concrete, and the dosage of water reducing agent is relatively high. For natural aggregates with high water absorption, only a few literatures suggest that sandstone has a high water absorption, and no research has been done on its application performance, and no special water reducing agent has been developed.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a polycarboxylic acid-based high-performance water-reducing agent for coarse aggregates with high water absorption, and its preparation and application. With the characteristics of post-bleeding, low shrinkage and good slump retention, it is suitable for the preparation of high water absorption coarse aggregate high performance concrete.

Technical scheme of the present invention:

A polycarboxylic acid-based high-performance water-reducing agent for coarse aggregates with high water absorption, the composition is composed of the following materials by weight percentage:

Polycarboxylate superplasticizer I: 4.00%～40.00%;

Polycarboxylate superplasticizer II: 1.00%～20.00%

Defoamer: 0.01%～1.00%;

Air-entraining agent: 0.00%～1.00%;

Retarder: 0.05%～10.00%;

Bleeding inhibitor: 0.10%～2.00%

Adsorption inhibitor: 0.00% to 2.00%

Water: 26.00～68.00%;

in:

The weight-average molecular weight of the polycarboxylic acid superplasticizer I is 10,000 to 120,000;

The weight-average molecular weight of the polycarboxylic acid superplasticizer II is 10,000 to 120,000;

The defoamer is a slow-release defoamer;

Described air-entraining agent is dodecanol sulfate monoester sodium salt;

Described retarder is one or two compounds of sodium gluconate and white sugar;

The bleeding inhibitor is 2-acrylamide-2-methylpropanesulfonic acid-N,N-dimethylacrylamide;

The adsorption inhibitor is polyvinyl alcohol.

The above-mentioned air-entraining agent: 0.00% to 1.00%, including 0.00% for protection, no air-entraining agent is added, and more preferably 0.03% to 1.00%.

The above-mentioned adsorption inhibitor: 0.00% to 2.00%, including 0.00% for protection, no adsorption inhibitor is added, more preferably 0.02% to 2.00%.

Described polycarboxylate superplasticizer (I) is a polycarboxylate superplasticizer containing the following general structural formula:

Wherein R ₁ represents hydrogen, methyl or COOM group, R ₂ represents hydrogen, methyl or CH ₂ COOM group, M represents hydrogen, monovalent metal, divalent metal, ammonium group or organic amine group; R ₃ represents hydrogen Or methyl; R ₄ O represents an oxyalkylene group of 2-8 carbon atoms; R ₅ represents hydrogen or an alkyl group of 1-6 carbon atoms; n and m are any integers other than zero; q represents a methylene group The number of , is an integer from 0 to 2; k represents the average number of moles of oxyalkylene groups added, which is any number from 1 to 180;

Said polycarboxylic acid superplasticizer (II) is copolymerized by 5%-92% by mass of monomer A, 8%-95% by mass of monomer B and 0-30% by mass of monomer C Obtained, wherein monomer A has the structure of general formula (1):

Wherein R ₆ represents hydrogen, methyl or -COOM group, R ₇ represents hydrogen, methyl or -CH ₂ COOM group, M represents hydrogen, monovalent metal, divalent metal, ammonium group or organic amine group; R ₈ O represents an oxyalkylene group of 2-8 carbon atoms; R ₉ represents hydrogen or an alkyl group of 1-6 carbon atoms; x represents the number of methylene groups, which is an integer of 0-2; y represents an oxyalkylene group The average number of added moles is any number from 1 to 180. In the copolymer, the monomer A is one, two or more of which are used in combination;

Monomer B has the structure of general formula (2):

wherein R ₁₀ represents hydrogen, methyl or COOM group, R ₁₁ represents hydrogen, methyl or CH ₂ COOM group, M represents hydrogen, monovalent metal, divalent metal, ammonium group or organic amine group; in the copolymer, Monomer B is used in combination of one, two or more;

Monomer C is hydroxyethyl acrylate, methacrylate, acrylonitrile, unsaturated sulfonic acid or its salt, acrylamide, methylol acrylamide, vinyl ester, vinyl aromatic compound. In the copolymer, the monomer C is used in a mixture of one, two or more.

The slow-release defoamer is a compound represented by the general structural formula (3):

Wherein: R ₁₂ represents HOOC-CH=CH-, HOOC-CH-CH-; w represents -COO-, -CONHCH ₂ CH ₂ O-; R ₁₃ O represents an oxyalkylene group of 2-8 carbon atoms; R ₁₄ represents an alkyl group of 1-6 carbon atoms, and Z is any integer of 1-120.

The bleeding inhibitor is 2-acrylamide-2-methylpropanesulfonic acid-N,N-dimethylacrylamide.

The adsorption inhibitor is polyvinyl alcohol, the degree of polymerization is 300, and the degree of alcoholysis is 87%-89%.

Said polycarboxylic acid-based high-performance water reducer, preferably, the composition includes the following components: 30 parts by weight of polycarboxylic acid superplasticizer I, 20 parts by weight of polycarboxylic acid superplasticizer II, 4 parts by weight of polycarboxylic acid superplasticizer parts by weight of retarder, 0.22 parts by weight of antifoaming agent, 0.2 parts by weight of air entraining agent, 0.5 part by weight of bleeding inhibitor and 0.5 part by weight of adsorption inhibitor, 44.58 parts by weight of water; or the composition comprises The following components: 33 parts by weight of polycarboxylate superplasticizer I, 12 parts by weight of polycarboxylate superplasticizer II, 5 parts by weight of retarder, 0.17 parts by weight of defoamer, 0.05 parts by weight of entrained air agent, 1 part by weight of a bleeding inhibitor, 0.5 part by weight of an adsorption inhibitor, and 48.78 parts by weight of water.

The solid content of the water-reducing agent composition is 20-40%, and the water-reducing rate is 10-28%.

The dosage of the polycarboxylic acid-based high-performance water reducing agent is 0.6% to 2.0% of the mass of the total cementitious material in the concrete.

The application of the above-mentioned polycarboxylic acid-based high-performance water-reducing agent can be applied to the preparation of high-water absorption coarse aggregate high-performance concrete.

The invention utilizes the bleeding inhibitor and the adsorption inhibitor to further help solve the problems of bleeding and consumption by ineffective adsorption that occur when the polycarboxylic acid encounters aggregates with a large water absorption rate.

The coarse aggregate with high water absorption rate is easy to absorb water molecules and high molecular polymers because of its large pore structure, thereby reducing the amount of polycarboxylate water reducing agent used for cement dispersing. Carboxylic acid superplasticizers can disperse and maintain the dispersing ability of cement particles respectively; the main purpose of the combination of defoamer and air-entraining agent is to adjust the working performance of concrete, which can eliminate the introduction of polycarboxylate superplasticizers. The large air bubbles brought by it will produce closed and independent tiny air bubbles; the selection of the retarder is mainly to control the setting time of the concrete; the addition of the bleeding inhibitor can effectively lock the water and prevent the porous coarse aggregate from vibrating during construction. The water in the pore structure is released to cause bleeding, which helps to improve the workability of concrete; the -OH structure contained in the adsorption inhibitor polyvinyl alcohol is easily adsorbed to the surface of the particles, and can form with polycarboxylate superplasticizer. Competitive adsorption, effectively preventing the polycarboxylate superplasticizer from being adsorbed into the pores, reducing the useless consumption of the polycarboxylate superplasticizer. When the product of the present invention is used for preparing high-performance concrete with high water absorption and coarse aggregate, fresh concrete with good construction performance can be obtained, and the requirements on the appearance quality, shrinkage rate and strength of concrete can be met.

Detailed ways

In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the examples, but the content of the present invention is not limited to the following examples.

Materials, reagents, etc. used in the following examples can be obtained from commercial sources unless otherwise specified.

Example 1

Weigh 45.43kg of water and place it in the reactor, then add 4.00kg sodium gluconate under agitation, add 30.00kg of solid content successively after being completely dissolved and be 40% PCE-1-1 (polycarboxylate superplasticizer I , the specific structure is

)、20.00kg40％固含量的PCE-2-1(聚羧酸超塑化剂Ⅱ，单体A为异戊烯醇聚氧乙烯醚，聚氧乙烯数为55，单体B为顺丁烯二酸，单体C为丙烯酸羟乙酯)，然后加入0.08kg缓释型消泡剂D1(R₁₂为HOOC-CH＝CH-，w为-CONHCH₂CH₂O-，R₁₃O为5个碳原子的氧化烯基，R₁₄为2个碳原子的烷基，Z为60)、0.50kg泌水抑制剂，继续搅拌均匀后即得到本发明的聚羧酸系高性能减水剂，记为LWAC-1。

), 20.00kg 40% solid content PCE-2-1 (polycarboxylate superplasticizer II, monomer A is prenol polyoxyethylene ether, polyoxyethylene number is 55, monomer B is maleic butene Diacid, monomer C is hydroxyethyl acrylate), then add 0.08kg slow-release defoamer D1 (R ₁₂ is HOOC-CH=CH-, w is -CONHCH ₂ CH ₂ O-, R ₁₃ O is 5 oxyalkylene group of carbon atoms, R ₁₄ is an alkyl group of 2 carbon atoms, Z is 60), 0.50kg of a bleeding inhibitor, and the polycarboxylic acid-based high-performance water-reducing agent of the present invention is obtained after continuing to stir evenly, Denoted as LWAC-1.

Example 2

)、20.00kg40％固含量的PCE-2-2(聚羧酸超塑化剂Ⅱ，单体A为异戊烯醇聚氧乙烯醚，聚氧乙烯数为55，单体B为顺丁烯二酸，单体C为丙烯酸羟乙酯)，然后加入0.10kg缓释型消泡剂D1、0.50kg泌水抑制剂，继续搅拌均匀后即得到本发明的聚羧酸高性能减水剂组合物，记为LWAC-2。Weigh 45.40kg of water and place it in the reactor, then add 4.00kg sodium gluconate under agitation, add the PCE-1-2 (polycarboxylate superplasticizer I of 30.00kg40% solid content successively after being completely dissolved, concrete Structure is

), 20.00kg 40% solid content PCE-2-2 (polycarboxylic acid superplasticizer II, monomer A is prenol polyoxyethylene ether, the number of polyoxyethylene is 55, and monomer B is maleic butene Diacid, monomer C is hydroxyethyl acrylate), then add 0.10kg slow-release defoamer D1, 0.50kg bleeding inhibitor, and continue to stir to obtain the polycarboxylate high-performance water reducer combination of the present invention thing, denoted as LWAC-2.

Example 3

Weigh 44.58kg of water and place it in the reactor, then add 4.00kg sodium gluconate under agitation, add 30.00kg40% solid content PCE-1-1, 20.00kg40% solid content PCE-2- 1, then add 0.20kg air-entraining agent, 0.22kg defoamer D1, 0.50kg bleeding inhibitor, after 0.5kg adsorption inhibitor continues to stir to obtain polycarboxylate high performance water reducing agent composition of the present invention, record for LWAC-3.

Example 4

Weigh 48.75kg of water and place it in the reactor, then add 3.00kg sodium gluconate successively under agitation, and add 33.00kg40% solids of PCE-1-2 and 12.00kg40% solids of 2.00kg white sugar successively after being completely dissolved. PCE-2-2, then add 0.06kg of air-entraining agent, 0.19kg of defoamer D1, 1.00kg of bleeding inhibitor, 0.5kg of adsorption inhibitor, and continue to stir to obtain the polycarboxylate high-performance water-reducing agent of the present invention agent composition, denoted as LWAC-4.

Example 5

Weigh 48.78kg of water and place it in the reactor, then add 3.00kg sodium gluconate and 2.00kg white sugar successively under agitation, add 33.00kg40% solid content PCE-1-1, 12.00kg40% solid content successively after being completely dissolved PCE-2-1, then add 0.05kg air-entraining agent Y2, 0.17kg defoaming agent D1, 1.00kg bleeding inhibitor, 1.5kg adsorption inhibitor, continue stirring to obtain the polycarboxylic acid high performance of the present invention Water reducing agent composition, denoted as LWAC-5.

Comparative Example 1

Weigh 45kg of water and place it in the reactor, then add 5.00kg sodium gluconate successively under agitation, add 30.00kg40% solid content PCE-3-1 (commercially available water-reducing type polycarboxylate superplasticizer) successively after being completely dissolved. plasticizer), 20.00kg of PCE-3-2 (commercially available slump-preserving polycarboxylate superplasticizer) with a solid content of 40%, continue stirring to obtain a polycarboxylate high-performance water reducer composition, denoted as PC -1.

The polycarboxylate superplasticizer compositions LWAC-1 to LWAC-5 in the above examples, the polycarboxylate superplasticizer composition PC-1 of the comparative example, and the commercially available preformed polycarboxylate superplasticizers were combined. The superplasticizer composition PC-2 was added to the concrete according to the proportion of coarse aggregate concrete with high water absorption, and the initial and 1h slump and fluidity, initial bulk density, 28d compressive strength and shrinkage of the fresh concrete were tested. Ratio, barrel molding (70L) to observe the appearance after demolding. The cement used in the test is CMP.O.42.5, grade I fly ash, natural river sand with a fineness modulus of 2.7, 5-20mm crushed stone (the water absorption rate of large stones is 5.03%, and the water absorption rate of small stones is 3.46%), C40 The concrete mix ratio is: C:F:S:G:W=357:63:738:978:164, in which the ratio of large and small stones is 4:1. The application performance test was carried out using the high water absorption coarse aggregate concrete mix ratio, and the results are shown in Table 1.

Table 1 Test results of application performance of various superplasticizers in high water absorption coarse aggregate concrete

The polycarboxylate water-reducing agent composition of the present invention contains a variety of hydrophilic groups, the copolymerization ratio of small molecular groups is high, and the molecular structure is uniform, so that the product has a high water-reducing rate; and the water-reducing agent contains esters Bond molecules will gradually hydrolyze in an alkaline environment, so that they can continuously adsorb with cement for a period of time, which can reduce the slump loss of concrete; at the same time, the water reducing agent contains functional groups that can reduce the surface tension of concrete pore solutions , which can reduce the negative capillary pressure to reduce the shrinkage stress of concrete.

It can be seen from the test results that the polycarboxylate water reducing agent composition of the present invention has good initial dispersing ability and good slump retention ability, and the prepared fresh concrete has good workability and wrapping property, and the appearance of concrete is good. A certain improvement can be obtained; compared with the comparative example 1, the polycarboxylate water reducing agent composition of the present invention has little difference in initial fluidity, but the slump retention ability has been greatly improved, and the concrete state has been greatly improved. Improvement, the appearance of concrete can also be significantly improved through the deployment of different proportions of the bubble regulator; the polycarboxylate water reducer composition of the present invention is compared with the prefabricated polycarboxylate water reducer composition in terms of initial fluidity and slump retention. The properties of the concrete are relatively good, and because the initial air bubbles of the concrete using the commercially available products are relatively large, although the bulk density is low, the wrapping of the fresh concrete is poor, and slight oozing occurs when inserting and tamping, and the appearance of the hardened concrete is not very good. The medium-bleeding inhibitor can well inhibit the release of water in the pores of the coarse aggregate with high water absorption, and the adsorption inhibitor can effectively reduce the consumption of polycarboxylate superplasticizer and prolong the workability retention time of concrete. Therefore, using the polycarboxylate water-reducing agent of the present invention can make the fresh concrete obtain good working performance, and can meet the requirements on the appearance quality, shrinkage rate and strength of the concrete.

The above are only the preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the concept of the present invention, several improvements and modifications can also be made, and these improvements and modifications should also be regarded as are within the protection scope of the present invention.

Claims (9)

1. A polycarboxylic acid high-performance water reducing agent for coarse aggregates with high water absorption is characterized in that: the composite material consists of the following substances in percentage by weight:

polycarboxylic acid superplasticizer I: 4.00% -40.00%;

polycarboxylic acid superplasticizer II: 1.00% -20.00%;

defoaming agent: 0.01 to 1.00 percent;

air entraining agent: 0.00% -1.00%;

retarder: 0.05 percent to 10.00 percent;

bleeding inhibitors: 0.10% -2.00%;

adsorption inhibitor: 0.00% -2.00%;

water: 26.00-68.00%;

wherein:

the weight average molecular weight of the polycarboxylic acid superplasticizer I is 10000-120000;

the weight average molecular weight of the polycarboxylic acid superplasticizer II is 10000-120000;

the defoaming agent is a slow release defoaming agent;

the air entraining agent is sodium lauryl sulfate monoester salt;

the retarder is one or two of sodium gluconate and white sugar;

the bleeding inhibitor is 2-acrylamide-2-methylpropanesulfonic acid-N, N-dimethylacrylamide;

the adsorption inhibitor is polyvinyl alcohol.

2. The polycarboxylic acid-based high performance water reducing agent for coarse aggregates with high water absorption according to claim 1, characterized in that: the polycarboxylic acid superplasticizer I is a polycarboxylic acid superplasticizer containing the following structural general formula:

wherein R is₁Represents hydrogen, methyl or a COOM group, R₂Represents hydrogen, methyl or CH₂COOM group, M represents hydrogen, monovalent metal, divalent metal, ammonium group or organic amine group; r₃Represents hydrogen or methyl; r₄O represents an oxyalkylene group of 2 to 8 carbon atoms; r₅Represents hydrogen or alkyl of 1 to 6 carbon atoms; n and m are any integers not equal to zero; q represents the number of methylene groups and is an integer of 0 to 2; k represents an average molar number of addition of the oxyalkylene group and is an arbitrary number of 1 to 180.

3. The polycarboxylic acid-based high performance water reducing agent for coarse aggregates with high water absorption according to claim 1, characterized in that: the polycarboxylic acid superplasticizer II is obtained by copolymerizing 5-92% of monomer A, 8-95% of monomer B and 0-30% of monomer C by mass percent, wherein the monomer A has a structure of a general formula (1):

wherein R is₆Represents hydrogen, methyl or a-COOM group, R₇Represents hydrogen, methyl or-CH₂COOM group, M represents hydrogen, monovalent metal, divalent metal, ammonium group or organic amine group; r₈O represents an oxyalkylene group of 2 to 8 carbon atoms; r₉Represents hydrogen or alkyl of 1 to 6 carbon atoms; x represents the number of methylene groups and is an integer of 0-2; y represents the average molar number of addition of the oxyalkylene group and is any number of 1 to 180, and in the copolymer, the monomer A is one, two or more of the monomers are mixed for use;

monomer B has the structure of formula (2):

wherein R is₁₀Represents hydrogen, methyl or a COOM group, R₁₁Represents hydrogen, methyl or CH₂A COOM group, M represents hydrogen, a monovalent metal, a divalent metal, an ammonium group or an organic amine group; in the copolymer, the monomer B is one, two or more of the monomers;

the monomer C is acrylate, methacrylate, acrylonitrile, unsaturated sulfonic acid or salt thereof, acrylamide, hydroxymethyl acrylamide, vinyl ester and vinyl aromatic compound; in the copolymer, the monomer C is used in combination of one, two or more thereof.

4. The polycarboxylic acid-based high performance water reducing agent for coarse aggregates with high water absorption according to claim 1, characterized in that: the slow-release antifoaming agent is a compound represented by the general structural formula (3):

wherein: r₁₂Represents HOOC-CH ═ CH-or HOOC-CH-; w represents-COO-or-CONHCH₂CH₂O-；R₁₃O represents an oxyalkylene group of 2 to 8 carbon atoms; r₁₄Represents an alkyl group of 1 to 6 carbon atoms, and Z is any integer of 1 to 120.

5. The polycarboxylic acid-based high performance water reducing agent for coarse aggregates with high water absorption according to claim 1, characterized in that: the polymerization degree of the polyvinyl alcohol is 300, and the alcoholysis degree of the polyvinyl alcohol is 87% -89%.

6. The polycarboxylic acid-based high performance water reducing agent for coarse aggregates with high water absorption according to claim 1, characterized in that: the using and mixing amount of the polycarboxylate superplasticizer is 0.6-2.0% of the mass of the total cementing material in the concrete.

7. The polycarboxylic acid-based high performance water reducing agent for coarse aggregates with high water absorption according to claim 1, characterized in that: the solid content of the water reducing agent is 20-40%.

8. The method for preparing the polycarboxylic acid-based high-performance water reducing agent for coarse aggregates with high water absorption according to claim 1, characterized in that: the method comprises the following steps: weighing water, placing the water in a reaction kettle, adding sodium gluconate under a stirring state, sequentially adding a polycarboxylic acid superplasticizer I and a polycarboxylic acid superplasticizer II after the sodium gluconate is completely dissolved, adding a slow-release antifoaming agent and a bleeding inhibitor, and continuously stirring uniformly to obtain the polycarboxylic acid high-performance water reducing agent for the coarse aggregate with high water absorption.

9. The use of the polycarboxylic acid-based high-performance water reducer for coarse aggregates with high water absorption according to claim 1 for preparing high-performance concrete with coarse aggregates with high water absorption.