Modification And Properties Of Recycled Cementitious Materials

The Large number of energy and natural resources consumed, the exhaust emissions as well as the sharp increase of waste concrete by cement and concrete industry have formed an increasingly heavy burden on the society, economy and environment. Therefore the preparation of recycled cementitious materials by the use of waste concrete has important theoretical value and practical significance. This thesis aims at the the problem of water demand and high CaO content, research on the modification and properties of recycled cementitious materials. The results of this article are as follow:The modified study of cement paste dehydration with highly active silicon raw materials mixed. The mineral composition, structure evolution and modification mechanism of recycled cementitious materials during the heating process which prepared under different treatment processes and raw materials were studied by the techniques of XRD, FT-IR,29Si-NMR. The results showed that:The?-CaO generated from the cement paste will react with the middle phase of C-S-H and highly reactive ultrafine silica fume during the thermal decomposition. The P-C2S formed in this process that has reduced the?-CaO content in recycled cementitious materials effectively. The hydration analysis, FE-SEM were used to study the hydration characteristics and microstructure of hydration paste of recycled cementitious materials, as well as the relativity of the heat treatment regime with the structural characteristics and hydration activity of in the dehydration phases.This research provides a theoretical basis of optimizing the preparation process of the recycled cementitious material and improving the hydration of cementitious ability of resycled cementitious materials.The influence of the hydration activity of recycled cementitious materials with different composition of raw material and calcination system were studied, and use the recycled cementitious materials to prepare the admixtures in the preparation of concrete. Research on the influence of work performance, physical and mechanical performance by use the recycled cementitious materials. The results show that: compared to ordinary recycled cementitious material, the modified measures can improve the problem of short setting time of recycled cementitious materials, reduce the required amount of water and improve the work performance as well as the physical and mechanical properties of concrete. The volume stability and the ability of resistance to chloride ion penetration is almost the same with the ordinary concrete.