阅读说明：本技术 一种再生骨料混凝土和易性耐久性改良添加剂 (Recycled aggregate concrete workability improving additive ) 是由 赵同峰 周烨 李冬松 于 2019-11-01 设计创作，主要内容包括：本发明一种再生骨料混凝土施工性耐久性改良添加剂,属建筑材料技术领域,包括硅酸锂、微硅粉、复合引气剂、增稠润滑剂、聚羧酸减水剂、缓凝剂,其中：硅酸锂：聚羧酸减水剂混合溶液＝0.001-0.08；普通引气剂：纳米引气剂＝0.1-5；各添加剂占混合溶液的重量百分比分别为：微硅粉：0.25-1.5；复合引气剂：0.001-0.005；增稠润滑剂：0.001-0.003；缓凝剂：0.001-0.05。本发明用于混凝土工程中,能大幅提高混凝土施工性、稳定性及耐久性能。本发明适用于钢筋混凝土结构、混凝土结构及构筑物。使用本发明能大幅降低混凝土的粘度,提高混凝土流速与扩展度、抗裂性、施工性以及工作稳定性。(The invention relates to an additive for improving the construction durability of recycled aggregate concrete, which belongs to the technical field of building materials and comprises lithium silicate, micro silicon powder, a composite air entraining agent, a thickening lubricant, a polycarboxylic acid water reducing agent and a retarder, wherein: lithium silicate: 0.001-0.08% of polycarboxylic acid water reducing agent mixed solution; common air entraining agents: 0.1-5 parts of nano air entraining agent; the weight percentages of the additives in the mixed solution are respectively as follows: micro silicon powder: 0.25-1.5; compound air entraining agent: 0.001-0.005; thickening lubricant: 0.001-0.003; retarder: 0.001-0.05. The invention is used in concrete engineering, and can greatly improve the construction property, stability and durability of concrete. The invention is suitable for reinforced concrete structures, concrete structures and structures. The invention can greatly reduce the viscosity of concrete and improve the flow rate, the expansion degree, the crack resistance, the constructability and the working stability of the concrete.)

1. A recycled aggregate concrete workability durability improving additive is characterized in that: the silicon dioxide water reducing agent comprises lithium silicate, micro silicon powder, a composite air entraining agent, a thickening lubricant, a polycarboxylic acid water reducing agent and a retarder, wherein the lithium silicate and the polycarboxylic acid water reducing agent are colorless transparent liquid, the composite air entraining agent comprises a micron air entraining agent and a nanometer air entraining agent, and the micro silicon powder, the composite air entraining agent and the thickening lubricant are powdery particles; the weight ratio of each component is as follows:

(1) lithium silicate: 0.001-0.08% of polycarboxylic acid water reducing agent;

(2) micron air entraining agent: 0.1-5 parts of nano air entraining agent;

(3) micro silicon powder: polycarboxylic acid water reducing agent: 0.25-2;

(4) the weight percentages of the functional additives in the total mixed solution are respectively as follows:

compound air entraining agent: 0.1-0.5;

thickening lubricant: 0.1-0.3;

retarder: 0.1-5.

2. The recycled aggregate concrete workability improving additive according to claim 1, characterized in that: the weight ratio of each component is as follows:

(1) lithium silicate: 0.002-0.06 wt% of mixed solution of polycarboxylic acid water reducing agent;

(2) micron air entraining agent: 0.5-4 parts of nano air entraining agent;

(3) micro silicon powder: polycarboxylic acid water reducing agent: 0.3-1.5;

(4) the weight percentages of the functional additives in water are respectively as follows:

compound air entraining agent: 0.2-0.4;

thickening lubricant: 0.1-0.2;

retarder: 1-3.

3. The recycled aggregate concrete workability improving additive according to claim 1 or 2, characterized in that: the micron air entraining agent is one of rosin resin, alkyl and alkyl arene sulfonate and triterpenoid soap.

4. The recycled aggregate concrete workability improving additive according to claim 1 or 2, characterized in that: the retarder is one of sodium gluconate, white sugar (brown sugar) and borax.

5. The recycled aggregate concrete workability improving additive according to claim 1 or 2, characterized in that: the composite air entraining agent consists of a micron air entraining agent and a nanometer air entraining agent, wherein the dosage of the micron air entraining agent is used for ensuring that the air content in concrete is between 3 and 4 percent, and the nanometer air entraining agent is a polymer nanometer air entraining agent, so that a large amount of beneficial bubbles are introduced, and the air content is increased by 1 to 2 percent.

6. The use of a recycled aggregate concrete workability improving additive according to claim 1 or 2, characterized in that: and fully stirring the mixed solution and the functional additive, and then adding the mixed solution into cement concrete, mortar or cement paste to be uniformly stirred.

Technical Field

The invention belongs to the technical field of building materials, and particularly relates to a recycled aggregate concrete workability improving additive.

Background

In 2020, the yield of the construction waste in China reaches astonishingly 39.66 hundred million tons. While the yield of the construction waste is greatly increased, the problems of shortage of natural aggregate resources, rising of price and the like are faced. The recycling of the waste concrete is the most effective measure for solving the problems. China began to research and apply recycled aggregate concrete more than 10 years ago. However, due to the problems of policy, cost, raw material stability, particularly the durability of recycled aggregate concrete and the like, a plurality of obstacles are arranged for the recycled aggregate concrete, and the recycled aggregate concrete is not applied on a large scale for many years.

The recycled aggregate in actual production has unstable source, uneven quality and larger random performance and variability, the recycled aggregate produced by crushing treatment contains about 30 percent of hardened cement mortar, most of the cement mortar are independent blocks and are attached to the surface of natural aggregate in a small amount, and meanwhile, in the crushing process, the commercial concrete is influenced by external forces such as extrusion, collision, grinding and the like due to crushing machinery, so that a large amount of micro cracks exist in the aggregate, the original interface of the aggregate and cement paste in the matrix concrete block is influenced and damaged, and the cohesive force is reduced. Compared with natural aggregate, the high-performance natural aggregate has the characteristics of high water absorption rate, high water absorption speed, small apparent density and bulk density, large crushing index and the like.

The above problems cause the recycled concrete to be deteriorated in the impermeability, the resistance to carbonization, the resistance to sulfate attack, the resistance to chloride ion permeability, the wear resistance, the crack resistance, etc., to various degrees. When the method is used in engineering, the engineering quality requirements are often difficult to meet.

Research also shows that when the recycled coarse aggregate is adopted, the slump loss of the concrete is fast, the water consumption needs to be increased by about 5-15%, but the concrete of the polycarboxylic acid system with the sensitive state is more difficult to control than the common concrete due to the variability of raw materials.

Therefore, if the recycled concrete is popularized in a large scale and good construction performance and later-period service capacity of the recycled concrete are ensured, the construction stability and later-period durability of a concrete system need to be further improved through the additive.

Disclosure of Invention

In view of the above problems, the present invention provides an additive for improving workability and durability of recycled aggregate concrete by enhancing the permeability and binding force between a new cement-based material and recycled aggregate using lithium silicate. The construction stability of the concrete is improved through the composite action of all the additives, so that the homogeneity and stability of the recycled concrete are ensured, the durability is further improved, the construction is stable, and the applicability is strong.

The purpose of the invention is realized by the following technical scheme:

the additive comprises lithium silicate, micro silicon powder, a composite air entraining agent, a thickening lubricant, a polycarboxylic acid water reducing agent and a retarder, wherein the lithium silicate and the polycarboxylic acid water reducing agent are colorless transparent liquids, the composite air entraining agent comprises a micro air entraining agent and a nano air entraining agent, and the micro silicon powder, the composite air entraining agent and the thickening lubricant are powdery particles; the weight ratio of each component is as follows:

(1) lithium silicate: 0.001-0.08% of polycarboxylic acid water reducing agent;

(2) micron air entraining agent: 0.1-5 parts of nano air entraining agent;

(3) micro silicon powder: polycarboxylic acid water reducing agent: 0.25-2;

(4) the weight percentages of the functional additives in the total mixed solution are respectively as follows:

compound air entraining agent: 0.1-0.5;

thickening lubricant: 0.1-0.3;

retarder: 0.1-5.

Preferably, the weight ratio of each component is as follows:

(1) lithium silicate: 0.002-0.06 wt% of mixed solution of polycarboxylic acid water reducing agent;

(2) micron air entraining agent: 0.5-4 parts of nano air entraining agent;

(3) micro silicon powder: polycarboxylic acid water reducing agent: 0.3-1.5;

(4) the weight percentages of the functional additives in water are respectively as follows:

compound air entraining agent: 0.2-0.4;

thickening lubricant: 0.1-0.2;

retarder: 1-3.

Preferably, the micron air entraining agent is one of rosin resin, alkyl and alkyl arene sulfonate and triterpenoid soap.

Preferably, the retarder is one of sodium gluconate, white sugar (brown sugar) and borax.

Preferably, the composite air entraining agent consists of a micron air entraining agent and a nanometer air entraining agent, wherein the dosage of the micron air entraining agent is used for ensuring that the air content in the concrete is between 3 and 4 percent, and the nanometer air entraining agent is a macromolecule nanometer air entraining agent, so that a large amount of beneficial bubbles are introduced, and the air content is increased by 1 to 2 percent.

A method for using the additive for improving the workability and durability of recycled aggregate concrete comprises the steps of fully stirring the mixed solution and the functional additive, adding the mixed solution into cement concrete, mortar or cement paste, and uniformly stirring.

The invention has the beneficial effects that:

1. the invention utilizes lithium silicate to enhance the permeability and the binding force between the new cement-based material and the recycled aggregate. A large amount of tiny air bubbles are introduced through the composite air entraining agent, and the flow rate of the cement matrix is improved while the water solution is thickened through the polycarboxylic acid water reducing agent, the micro silicon powder and the thickening lubricant. The construction time is ensured by the retarder. Besides the characteristics of respective performance of each additive, the composite action of the additives further improves the construction stability of the concrete, thereby ensuring the homogeneity and stability of the recycled concrete and further improving the durability.

2. In the invention, the composite air entraining agent consists of a common air entraining agent and a high molecular polymer air entraining agent, wherein the common air entraining agent introduces millimeter-sized and micron-sized bubbles; the air entraining agent of the high molecular polymer is introduced into micron-sized and nanometer-sized bubbles. The common air entraining agent is used for introducing enough gas; the high molecular polymer air entraining agent introduces a large amount of tiny bubbles, the microbubbles are extremely stable, the function of the balls is exerted in the concrete, and the slump and the flowing speed of the concrete are improved. Meanwhile, a large number of air chambers prevent water and harmful substances from invading in the service period of the concrete, and the durability of the concrete is improved.

3. The invention can be used as the workability improving additive of the recycled aggregate concrete, can greatly improve the cohesiveness, the water retention and the fluidity of the recycled aggregate concrete, overcomes the contradiction between the viscosity and the flow rate, has good construction performance and construction stability, improves the construction speed, reduces the secondary waste rate, avoids secondary water adding of workers on site, and ensures the engineering quality.

4. The material provided by the invention can greatly improve the durability of concrete, so that the service life of the concrete meets the design service life, the maintenance cost is further reduced, the secondary pollution is avoided, and the energy conservation and emission reduction are further realized. The concrete has the characteristics of water reduction, thickening, air entraining, viscosity reduction, slow setting and the like, and is stable in construction and strong in applicability. And has certain economic benefit and social benefit.

Detailed Description

The present invention will be described in detail with reference to examples.

The common air entraining agent is one or more of rosin resin, alkyl and alkyl arene sulfonate and triterpenoid soap.

The retarder is one or more of sodium gluconate, white sugar (brown sugar) and borax. On one hand, the setting time of the concrete can be delayed, and the later strength is improved; on the other hand, the sodium gluconate has the viscosity reduction effect, and the white sugar (brown sugar) and the borax have certain thickening and water retention performances and can be selectively added according to actual needs so as to properly adjust the concrete state.

A small amount of silica fume fills gaps among cement particles, so that on one hand, free water in the gaps is released, the fluidity of concrete is improved, and on the other hand, the silica fume has a large specific surface area and adsorbs a large amount of free water, so that a cement matrix system becomes viscous, and the construction stability is improved. On the other hand, the addition of the silica fume adjusts the micro-gradation of the cementing material, and reduces the defects of the transition area of the new cement base and the recycled aggregate interface, thereby improving the mechanical properties of the cement base material, such as binding power, compression resistance, rupture strength and the like, and correspondingly improving other durability.

The thickening lubricant is a synthetic high molecular polymer, and is different from the traditional thickening products such as cellulose, welan gum and xanthan gum. Its function is both thickening and lubricating. The long-chain structure of the polymer is combined with concrete mixing water, the water solution becomes viscous, but the lubricating property of the water solution reduces the friction force among cement particles, and compensates the influence on the fluidity loss of the concrete.

The thickening lubricant, the micro silicon powder and the nano air entraining agent are used in a composite way, so that the compactness of the concrete is better. The good cohesiveness and water retention solve the defects of water sensitivity and doping amount sensitivity of the polycarboxylate superplasticizer, and well ensure the stability of the concrete state under the condition of unstable recycled aggregate. In addition, in a stable cement-based system, bubbles are smaller, more homogeneous and more stable, and the durability of the recycled concrete in all aspects is greatly improved.