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Study on grouting material used for connecting longitudinal steel sleeve of assembly building
Release time:2017-5-26 18:43:20      Click on the number of times:942


With the construction of industrialization related policies and industry norms have been introduced, the assembly type concrete structure in China ushered in the development of the opportunity. In addition to the design and manufacture of prefabricated components, the key technologies of assembly type concrete structures are the installation and connection of components. At present, the connection method of longitudinal reinforcement used in engineering is the use of sleeve grouting. The principle is that the reinforcement and the sleeve are firmly connected together with the cement grouting material.

Cement based grouting material is a dry mixture composed of cement and other cementitious materials as base material, adding proper amount of fine aggregate and a small amount of admixture and other materials. After mixing with water, it has the properties of large fluidity, quick hardness, high strength and so on. It is filled in the gap between the sleeve and the ribbed steel bar, and the steel grouting joint is formed. The performance of grouting material will directly affect the safety performance of the component, study the influence of each component on the performance of the grouting material, grouting material to solve the contradiction between high fluidity and high strength has an important significance for improving the safety performance of building assembly.

Influence of kinds of cementitious materials on properties of grouting material

At present, cementitious materials used in cement based grout mainly include high performance Portland cement, sulphoaluminate cement and Portland cement combined with sulphoaluminate cement (or aluminate cement). The high performance Portland cement is used as the main cementing material, and the expansion component is added to compensate the shrinkage during the hydration and hardening of the cement. The grouting material has the advantages of low cost, simple preparation and wide application. However, due to China's expanding agent product quality under expansion component uneven in quality, performance or cement to the products easy to cause grouting material quality fluctuation, therefore need to repeatedly test and technical adjustment, to seek the best formula.

When the sulphoaluminate cement is used as the main cementitious material, the expansion property of the sulphoaluminate cement does not need to be added into the expansion component. This kind of grouting material short setting time, high early strength, expansion performance is reliable, but the production cost is high, mainly for passenger dedicated pot rubber bearing grouting and cement concrete pavement rapid repair engineering.

When using Portland cement and sulphoaluminate cement (or cement) as the main composite cementitious material preparing grouting material, the number of gypsum and ettringite formation control to improve the mechanical properties of composites and the expansion properties. However, the grouting material is often adjusted because of the complex composition of the raw materials.

Influence of mineral admixture on properties of grouting material

The mineral admixtures are high performance cement-based materials indispensable component, studies have shown that the use of mineral admixtures to replace part of cement, can effectively improve the performance of cement based grouting material and hardened cement paste. The improvement of mineral admixtures is closely related to their particle size distribution, particle morphology and hydrophilic properties.

Influence of fine aggregate type on properties of grouting material

As an important component of mortar, fine aggregate affects the workability, compactness and strength of paste. The natural sand and quartz sand with good gradation are usually used in the grouting of cement base grouting material.

Influence of admixture type on grouting material performance

1. water reducing agent

High efficiency water reducing agent is the key to ensure high fluidity of grouting material with low water cement ratio. At present, the commonly used polycarboxylate superplasticizer has the advantages of good compatibility with different kinds of cement, low dosage, high water reducing rate and good slump retention. It is an important material for preparing high fluidity grouting material. However, if the polycarboxylate superplasticizer admixture, often can cause bleeding and segregation of slurry and other issues, and may even cause serious accidents, so we should choose the appropriate water reducing agent and to determine the optimal dosage of the test.

2. expansion agent

For cement grouting material, the expansion property is a very important index, so the expansion agent is another important admixture of cement based grouting slurry. Cement based grouting material will produce plastic shrinkage in the construction of the early days of l-3h, may lead to serious impact on the performance of hollowing. Moreover, with the increase of age, the cement based slurry will undergo self hydration reaction, which will cause autogenous shrinkage and drying shrinkage, which will lead to cracking of the hardened paste structure. Therefore, the early and late expansion components should be added into the cement-based grouting material to compensate the shrinkage of the slurry before and after hardening.

3. defoaming agent

In the flow of high strength cement based grouting material in the course of the study, because of the low water binder ratio and adding superplasticizer and superfine mineral admixture, often makes more viscous slurry, is not conducive to the discharge of slurry bubble, so easy to cause the structure of slurry density, finally affect the development of pulp the strength and durability of materials. Therefore, defoaming agents are often added in the preparation of cement based grouts. At present, the types of defoamer commonly used are mainly organosilicon, polyether modified polysiloxane, polyether and so on.

epilogue

The performance of the grouting material not only affects the construction quality of the dress matching type building, but also affects the safety of the building structure. How to solve the contradiction between high fluidity and high strength of grouting material is an important problem to be solved in grouting material research. At present, the quality of grouting material in the domestic market is uneven, and there is still a gap with foreign advanced technology. Strengthening the research of complete sets of grouting materials is of great significance to the development of prefabricated buildings.



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