Study On Thermal Deformation Properties Of Cement Paste

With the developing of concrete technology, bulk concrete and super-long structural concrete are always adopted in civil engineering. Internal stress occurs resulting from the different temperature distribution, which caused by hydration heat and the varying environmental temperature. Crack is inevitable when the internal stress exceeds the ultimate tensile strength of the materials, which affects the performance of concrete structure.In this paper, the test method of the linear thermal expansion coefficient (as LTEC) of hardened cement paste is studied. Influence factors of thermal deformation are investigated, including temperature, water cement ratio, age, moisture content, admixture and mix ratio. It was found that the LTEC increases with aging, temperature rising and water-cement ratio decreasing. The admixture can make the LTEC of cement paste smaller than pure cement paste. The moisture content in cement paste enlarges the LTEC.Cement paste is assumed to consist of the solid-a mixture of hydration products, anhydrated cement and admixtures-and the pores which are partially saturated by water and dry air. The factors affecting the thermal deformation of cement paste are as follows: the constituent in cement paste and its content determined by mix ratio and degree of hydration, the pore structure effected by mix ratio and age, the water content determined by pore structure and environmental humidity , the temperature. We can conclude that the LTEC decrease with porosity rising.It comes to the conclusion that these factors, according to the importance, may be ranked as porosity, age, temperature, moisture content. Big capillary has evident effect for the LTEC of cement paste, and air pore has some effect, too. But the pores which has smaller size is inessential.