Concrete additive is an admixture added during concrete mixing. It is mainly used to improve the performance of concrete. From the point of addition ratio of admixture, it is generally not more than 5%. Although it contains a small amount, it has played an active role in improving the performance of concrete and has become an indispensable part of the current development of concrete. The additives used in concrete mainly refer to different types of water reducing agents. The extensive promotion of concrete admixtures has led to significant improvements in the strength of the concrete, its brittleness and its own weight, and has improved the applicability of concrete construction. For example, adding antifreeze to concrete can make concrete construction work in the cold winter. The use of superplasticizers enables the renewal of concrete placement and flow regimes.
The water reducing agent is used for concrete mixing, which can change the gas content of the concrete, so that the gap ratio inside the concrete is greatly reduced. The effect of water reducer on the fluidity of concrete is usually reflected by the magnitude of the slump. When the proportion of water and cement used in concrete is constant, the degree of collapse of concrete can be greatly improved by adding a precipitant. And through the use of water reducing agents. The concrete setting time can be extended appropriately. However, it is necessary to properly control the amount of water reducing agent. Maintain reasonableness to avoid excessive increase in concrete that will not condense for a long time. By adding the scientific proportion of the water reducing agent, the performance and strength of the overall concrete structure can be improved, and the proportion of water cement in the concrete is reduced.
In the past 40 years, the application of water reducing agent in concrete has been rapidly developed. Polycarboxylate water reducing agent has become an indispensable component for the preparation of high performance concrete as a new generation of water reducing agent. However, the problem of poor adaptability of polycarboxylate water reducer (PCE) to cement has been a technical problem for cement manufacturers, concrete construction units and admixture manufacturers. Grinding is the most energy-consuming part of the cement production process. Improving the mechanical structure of the grinding and adding grinding aids during the grinding process are effective measures to reduce energy consumption and improve grinding efficiency. With the implementation of the energy conservation and emission reduction strategy, the proportion of grinding aids used in China's cement grinding process has exceeded 50%.
The adaptation and incompatibility between the so-called concrete admixture and cement can be considered as follows: When formulating concrete (or mortar), according to the technical specifications of concrete admixture application, a certain admixture that has been tested to meet the relevant standards can be added to the regulations. If the cement using the admixture of the variety can produce the desired effect, the cement is compatible with the admixture. On the contrary, if the effect is not produced, the cement and the admixture are not Compatible.
Water reducing agent is one of the most important types of concrete admixtures. It can be used alone or as a compound admixture with other functional components. It is a high performance water reducer for improving many properties of fresh and hardened concrete. The high performance water reducing agent is a water reducing agent having a higher water reducing rate, a better slump retention performance, a smaller drying shrinkage, and a certain air entraining performance than the superplasticizer. High performance water reducing agent has obvious technical advantages and high cost performance compared with other water reducing agents when formulating high strength concrete and high durability concrete.
Since the successful development and application of lignosulfonate water reducer in 1935, the development of admixtures has been more than 60 years old. The successful application of admixtures has brought a real revolution to the development of concrete technology because The application of the admixture can not only affect the construction of the concrete in the fresh mixing stage, but also improve the structure of the hardened concrete body from the microscopic and submicroscopic levels, so that the concrete can be modified by means of admixture.
In the construction process of highway engineering, concrete is an extremely important building material, which has a relatively large impact on the quality of highway engineering construction. In the concrete construction process, in order to ensure the performance of the concrete and improve the applicability of the concrete, an admixture is generally added to the concrete. As an indispensable part of concrete, concrete admixture can significantly improve the quality of concrete by adding admixture to concrete, improve the performance of concrete, reduce the amount of cement in concrete, and save construction costs. In the actual application process, different types of admixtures have different functions. In practical applications, they should be carefully selected and applied reasonably to ensure the construction quality of concrete. Therefore, it is necessary to correctly understand the concrete admixture so as to fully exert the effect of the admixture.
Study on Synthesis and between Molecular Structure and Performance of Ether-type Polycarboxylate Superplasticizer
The development and progress of concrete admixture technology has played a decisive role in the technological progress of the concrete industry. Throughout the industry, the entire industry has experienced the development of the first generation of ordinary water reducers represented by wood calcium and the second generation of superplasticizers represented by naphthalene series. As the third generation, the latest generation of high performance water reduction The agent, polycarboxylate high-performance water reducer has good performance in water reduction, moisture retention, plasticization, shrinkage and environmental protection, and has become the future development direction of the concrete admixture industry.
Latest research and development progress and market development trend of China's concrete admixture industry
The China Building Materials Federation Concrete Admixture Branch conducts a nationwide survey on the production of concrete admixtures every two years. The purpose is to grasp the latest developments in the industry and provide an accurate basis for formulating industry development policies. The investigation has been going on for more than ten years.
At present, the domestic grinding and grinding agents for research and application are liquid and solid. The formula consists mainly of single or composite products such as amines, polyols and acetates. The basic components are mostly organic surface active substances. Triethanolamine and ethylene glycol are highly polar surfactants and are used as cement grinding aids.