Research On The Durability And Reaction Mechanism Of Cement Based Composite Material With Gansu Attapulgite

Serious damage resulting from early-age deterioration of concrete structure has obtained more attention. Due to harsh natural environment in western regions, it is argent to research concrete durability. Incorporating mineral admixture into concrete is an important method to improve concrete durability. However, incorporation of mineral admixtures can increase the viscosity of concrete mixtures and reduce construction in practical engineering applications.Moreover, concrete with mineral mixtures can' t satisfy the requirement of crack resistance and it is difficult to detect concrete cracking. In order to solve above problems, the effect of attapulgite produced in Gansu province on workability, mechanical properties, volume stability and durability of cement-based composites on the basis of present situation about concrete durability in western regions. The application of cement-based composites with attapulgite has a good influence on the Qinghai-Tibet Railway engineering. According to analysis the mechanism of cement-based composites with attapulgite, the following conclusions can be obtained.1.After physical refining and purifying, the ratio between length and diameter of attapulgite in Gansu province is approximately 25. The one- dimensional attapulgite is a kind of nano-fibrous materials and can react with calcium hydroxide. The attapulgite can reduce the size of calcium hydroxide crystals, thus increasing concentration of OH- in pore solution and pH value of pore solution, which result in improving the quality of passive steel film and enhancing inhibiting effectiveness. The activated attapulgite can enhance corrosion resistance of cement-based materials and improve the effect of corrosion inhibitors, further effectively protecting passivated steel.2.The activated attapulgite can increase water demand and water retention and reduce bleeding rate of cementitous composites. Compared with high performace concrete with combination of fly ash, slag and silica fume, autogenous shrinkage and drying shrinkage of concrete with 1% attapulgite has been significantly reduced to 24% and 12%. Cracking time of concrete with attapulgite is apparently delayed and cracking area is sharply reduced 13.7%.Meanwhile, The role of attapulgite as nucleation can decrease the width of interfacial transition zone, improve the pore size and distribution, increase the ink bottle holes, the sulfate resistance,frost resistance and resistance to chloride penetration of concrete with attapulgite have been improved in different degree. The attapulgite produced in Gansu province can improve the rheology of concrete, shorten the time difference between surface and internal hardening.Meanwhile, high water absorption of attapulgite can provide a certain amount of water to delay cracking time and further increase volume stability of concrete.3.Concrete with attapulgite can satisfy the demand of the Qinghai-Tibet Railway engineering,such as construction, strength and durability, remarkable promoting social and economic benefits.