Effect of superplasticizer on shrinkage and cracking of concrete

Overview of superplasticizer

High-efficiency water reducing agent can significantly improve the fluidity of the mixing slurry, so that the foam mud can reach self-leveling in the mold and reduce or even no bread. It can greatly reduce water consumption while maintaining the slump of concrete. Water reducers are also called dispersants or plasticizers. It is the most commonly used admixture.

Principle of water reducing agent:

The specific surface area of cement is generally 350-400m2/kg, and more than 90% of the cement particles have a particle size in the range of 7-80 microns, which belongs to the category of fine powder particles. For cement-water systems, the surfaces of cement particles and hydrated cement particles have a slightly polar surface and are highly hydrophilic. Fine cement particles have a considerable specific surface energy (solid-liquid interface energy). In order to reduce the total heat on the surface solid and liquid, fine cement particles tend to spontaneously condense into flocs to minimize the interface energy of the system and make the system thermodynamic. keep it steady. At the same time, in the early stage of cement hydration, the surface of C3A particles is positively charged, while the surfaces of C3S and C2S particles are negatively charged.

There are three watering methods in concrete: free water combined with water and adsorbed water. In the initial stage of cement mixing, there is less chemically bound water and adsorbed water, and the mixed water mainly exists in the form of free water. However, due to the flocculation structure of the cement particles, 10%-30% of the open water is wrapped in them, thereby severely reducing the fluidity of the concrete mixture. The main function is to destroy the flocculation structure of cement particles, keep them in a dispersed state, and release free water in the packaging and flocs, thereby improving the fluidity of fresh concrete.

The role of superplasticizer:

1. Reduce the solid-liquid interface energy of cement particles

2. Electrostatic repulsion

3. Spatial repulsion

4. Lubrication effect of hydration film

Application of superplasticizer

With the continuous improvement of society and productivity technology, in the construction industry, the quality and performance requirements of concrete are becoming more and more stringent, and the quality of buildings is directly affected by the performance of concrete.

The invention of concrete admixture greatly improved this problem. Commercial concrete mixed with water-reducing agent greatly improves the work performance, increases the strength of the concrete, and improves the durability and service life of the concrete. This is a remarkable achievement. Used in the construction industry.

Water reducing agents are widely used in various key infrastructures, especially high-rise buildings, super high-rise buildings, high-speed railways, highways, subway stations, nuclear power plants, etc., which promote the rapid development and strong protection of the construction industry. industry.

The water-reducing agent is an additive, which can significantly reduce or greatly reduce the mixing water of concrete in the concrete mixing process, and improve the fluidity and strength. It has been proved that if the water-reducing agent is added to the concrete, if it is not necessary to increase the strength, it can be Greatly reduce the amount of cement and improve the compactness of concrete. Therefore, water reducing agent is an indispensable additive in commercial concrete.

In order to further improve the economic benefits of commercial concrete, concrete manufacturers like to use water-reducing agents with higher water-reducing properties to increase the strength of concrete or greatly reduce the amount of cement and reduce production costs.

In fact, this is a major misunderstanding. Although water reduction is beneficial to improve the compressive strength of concrete, excessive water reduction can also adversely affect the flexural strength of concrete.

Although proper water reduction is conducive to reducing the shrinkage of concrete, it must be noted that when designing the concrete mix, the water-reducing function of the water-reducing agent has been considered, and the water-cement ratio in the overall design is low, such as further reducing . The amount of water used will increase the shrinkage rate of the concrete and increase the shrinkage rate of the concrete.

When commercial concrete greatly reduces the amount of cement, although the compressive strength does not decrease, as the volume of hardened cement stone in the concrete decreases, the tensile strength will decrease.

Due to the reduction of cement consumption, the concrete grouting layer is too thin, which will cause more micro-cracks in the concrete. Of course, the micro-cracks have little effect on the compressive strength of concrete, but they cannot affect the tensile strength and other properties of concrete. The large reduction in neglected cementitious materials will also affect the elastic modulus and creep of concrete, making it easier to crack. In the production of commercial concrete, the water reduction rate of concrete and the amount of cementitious materials must be considered comprehensively. Never reduce moisture or excessively reduce gelling materials.

The price of superplasticizer

The price of superplasticizer varies randomly with production costs, transportation costs, international conditions, exchange rates, and market supply and demand of superplasticizers. Tanki New Materials Co. Ltd aims to help all industries and chemical wholesalers find high-quality products by providing a full range of products. If you are looking for superplasticizer, please contact us for the latest price.

Suppliers of superplasticizers

As a global supplier of superplasticizers, Tanki New Materials Co., Ltd. Has extensive experience in the performance, application and cost-effective manufacturing of advanced and engineering materials. The company has successfully developed a series of foam concrete additives (including lightweight concrete, CLC blocks provide concrete foaming agents, superplasticizers, foam concrete strength enhancers, etc.), high-purity targets, and functional materials. Ceramics and structural equipment, and provide OEM services.