How to select the right admixture? The key to improved ready-mixed concrete performance

Concrete, as one of the necessary construction materials in the process of building construction, is highly valued in the field of building construction.

Nowadays, the emergence of admixtures is to create more concrete construction technology new techniques, and there are many types of concrete, the resulting concrete in the construction and performance characteristics are different.These are in the application of ready-mixed concrete additives need to pay attention to the process, and different circumstances should be combined with the specific concrete construction and performance of the selection of the appropriate type of additives. Admixtures of different types, the performance of the characteristics of the different, so in the selection of additives ready-mixed concrete need to consider a number of influencing factors, remember not to confuse the principle of selection of admixtures.

Building construction units should do a good job of concrete commonly used admixtures of varieties and components of the division of work, according to the different kinds of admixtures back to the quality indicators and performance, analyse the basic mechanical properties and durability of concrete with admixtures. Do a good job of ready-mixed concrete admixture selection principle analysis is the most important link, but also at this stage of building construction field urgent solution to a major problem.

1. Varieties and components of commonly used admixtures

1.1 Ordinary water reducing agent, slow-setting water reducing agent

The most common additives for ready-mixed concrete are ordinary water reducing agents and retarders. Water reducing agent is one of the commonly used admixtures in the mixing process of concrete, and its main function is to reduce the amount of water required in the mixing process of concrete. The use of ordinary water reducing agent can not only effectively reduce the construction unit in the concrete mixing process of water consumption, but also can reduce the consumption of cement.

Commonly used ordinary water reducing agents and retarders are lignosulfonate water reducing agents, polycyclic aromatic salts and polycarboxylic acid high performance water reducing agents. Among them, lignosulfonates are mainly made of lignin, fumaric acid and other raw materials. As a general water reducing agent, lignosulfonate has a lower cost and can achieve 8% to 10% water reducing effect, which can effectively improve the strength and fluidity of concrete. Polycyclic aromatic sulfonate water reducing agent mainly refers to naphthalene homologous sulfonates, generally made of concentrated sulfuric acid and naphthalene and other materials.

Compared with the water reducing agent of lignosulfonate, the water reducing agent of polycyclic aromatic sulfonate can reach 25% even though the production cost is increased. This can further reduce the amount of water used by the construction unit in the mixing of concrete, strengthen the strength of concrete and improve the construction quality. Polycarboxylic acid-based high-performance water reducing agent is mainly made of milk acid. Compared with the above two kinds of water reducing agents, this kind of water reducing agent has the highest water reducing rate, and the comprehensive ability is far more than the above two kinds of water reducing agents.

1.2 Retarders

Retarder is also one of the commonly used admixtures in the process of concrete mixing, and its main function is to prolong the setting time of concrete, so that the concrete has better plasticity. Classified according to the structure of the coagulant, retarder can be roughly divided into: sugar retarder, citric acid and its salts retarder, zinc salts, phosphate retarder and lignosulfonate retarder four.

Due to the different composition and internal structure of different retarders, the duration of the effect on the concrete will also have a certain degree of difference. However, these retarders can effectively improve the strength of concrete and frost resistance. However, the construction personnel in the use of retarder and retarder water reducing agent also need to be used in moderation. If the retarder or retarder water reducing agent used too much will lead to concrete difficult to set, which seriously affects the construction efficiency.

If a large number of water-reducing agent will also lead to excessive evaporation of water in the concrete, making the concrete cracking and other problems affecting the quality of concrete construction.

2 Quality index and performance of the impellant

The quality of concrete admixtures will not only affect the quality of concrete construction, but also may have a greater impact on the concrete's solidification efficiency, water consumption and strength. Therefore, in order to ensure the construction quality of the project, the construction unit needs to strengthen the concrete admixture quality indicators and performance screening.

3 Interaction between the implant and the cement

The main role of the admixture is to add the corresponding admixture in the concrete, so as to achieve the improvement of concrete performance, and then promote the construction quality and construction efficiency of construction projects. The reason why the admixture can promote the improvement of concrete performance is because it can produce mutual effect with concrete. Usually the mutual effect between admixtures and concrete has adaptability, matching and compatibility.

Due to the main components in the admixture and various types of composition ratio has a big difference, so the adaptability between different admixtures and concrete will also produce a big difference. Poorly adapted admixtures may not only lead to the phenomenon of low water reduction rate of concrete, but also may lead to the rapid concreting of concrete, thus affecting the normal construction of the project. Better adapted admixtures can effectively improve the water reduction rate of concrete, and to a certain extent to avoid dry cracking, cracking and other phenomena in concrete.

The match between the admixture and the concrete will affect the adsorption efficiency of the concrete to the admixture. If the match between the admixture and the concrete is low, the adsorption efficiency of the concrete to the admixture will be extremely low, which will also affect the efficacy of the admixture.

The compatibility of the admixture with the concrete will have an impact on the efficiency of the admixture. If the compatibility between admixtures and concrete is poor, it will lead to the concrete not being able to blend with the admixture, which will lead to the waste of some admixtures. This phenomenon will lead to the low efficiency of the use of admixtures, which affects its performance.

4 Conclusion

The analysis of ready-mixed concrete admixture selection principle is very realistic, is the current stage of the development of the field of building construction in the process of focusing on a major technical problem. Practice has proved that the development and application of concrete admixtures will essentially give the development of building construction units to bring a certain role in promoting the construction unit to really improve the construction technology of the construction unit in the construction of the enterprise has a long-term development significance.