Development history of grouting materials

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In China, the traditional grouting material used in the early prestressed duct grouting is generally pure cement slurry. During construction, cement, water, water reducer, expansion agent, etc. are used for on-site preparation. The grouting material prepared on site must meet the following requirements: the water cement ratio is 0.40~0.45, and the water cement ratio can be reduced to 0.35 at least by adding an appropriate amount of water reducing agent; The maximum bleeding rate of the grouting material shall not exceed 3%, and the bleeding shall be absorbed by the mortar again within 24h; The viscosity of the grouting material should be controlled within 14-18s; The grouting material has a certain expansion effect before solidification; The compressive strength of the grout test block shall not be less than 50MPa. When cement, various admixtures and water are used to prepare grouting materials on site, there are usually problems such as poor compatibility of various admixtures and poor adaptability of cement and water reducer, resulting in the following serious problems in duct grouting: (1) poor stability of slurry quality, poor liquidity, fast flow loss and good volume stability; (2) Fresh slurry has large bleeding, easy segregation and stratification, much Micro Foam in the slurry, poor fluidity, improper setting time, slurry grouting is often not smooth, easy to block the pipe, slow construction speed, and it is difficult for the duct to become full, etc; (3) After hardening, the slurry is not dense, there are many air bubbles and needle gaps, and the bonding with the prestressed reinforcement is not solid. There are even broken lines in the slurry, the pores are not full, and the slurry outside the high points is powdered. The above problems not only affect the construction, but also directly related to the durability and safe use of the bridge structure

China has made some improvements to the traditional grouting materials prepared on site, using cement, water and a variety of admixtures to effectively solve the problem of poor compatibility of various admixtures on site. However, due to China's vast territory, the raw materials used in the production of cement in various places are different, and the cement produced is very different, so the problem of poor adaptability between cement and admixtures still exists

in foreign countries, the grouting material used at the duct grouting site is usually ready mixed commercial grouting material. The ready mixed commercial grouting material is a factory product, which is designed through experiments in advance, then prepared into uniform powder in the factory and packaged into bags. At the construction site, you only need to add water and mix it into slurry according to the instructions. Using ready mixed commercial grout can effectively solve the problems of poor compatibility of various admixtures and poor adaptability of cement and water reducer

on August 1st, 2011, the implementation of domestic jtg/t f50-2011 technical specifications for highway and bridge construction has greatly improved the requirements of all aspects of the performance of the grouting slurry. The on-site ready mixing can no longer meet the requirements, and is finally eliminated. Ready mixed commodity grout developed by Chongqing Boruida building materials Co., Ltd. and other new building materials enterprises has gradually occupied the market. Obviously, with the improvement of large radian, the domestic grouting technology can better protect the prestressed reinforcement from exposure and corrosion, and ensure the safety of prestressed concrete structures; Make the prestressed reinforced concrete have good bonding, ensure the effective transmission of prestress between them, and make the prestressed reinforcement and concrete work together

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