Search

Antimony (Sb) is a trace element applied widely in modern industry. A large number of tailing solid wastes are left and accumulated in the mining area after purifying the precious antimony from the antimony ores, causing serious pollution to the environment. The major aim of this study is to investigate the feasibility of utilizing antimony tailing coarse aggregate (ATCA) as a complete substitute for natural coarse aggregate (NCA) in high-strength concrete. Concrete specimens with 25%, 50%, 75%, and 100% ATCA replacing the NCA in conventional concrete were prepared for evaluating the performance of ATCA concrete. The investigators find that ATCA concrete has good workability, and the mechanical properties and long-term behavior (shrinkage and creep) of ATCA concrete with all replacement levels are superior to those of NCA concrete. The durability indices of ATCA concrete, such as the frost-resistant, chloride permeability, and resistance to carbonation, are better than those of NCA concrete. While the alkali activity and cracking sensitivity behavior of ATCA concrete seem to be decreased, nevertheless, the difference is not significant and can be neglected. The researchers demonstrate that all of the control indices of ATCA concrete meet the requirements of the current industry standards of China. Overall, ATCA can be used in concrete to minimize environmental problems and natural resources depletion.

Chloride binding capacity and its effect on the microstructure of mortar made with marine sand (MS), washed MS (WMS) and river sand (RS) were investigated in this study. The chloride contents, hydration products, micromorphology and pore structures of mortars were analyzed. The results showed that there was a diffusion trend for chloride ions from the surface of fine aggregate to cement hydrated products. During the whole curing period, the free chloride content in the mortars made by MS and WMS increased firstly, then decreased and stabilized finally with time. However, the total chloride content of three types of mortar hardly changed. The bound chloride content in the mortars made by MS and WMS slightly increased with time, and the bound chloride content included the MS, the WMS and the RS arranged from high to low. C3A·CaCl2·10H2O (Friedel’s salt) was formed at the early age and existed throughout the curing period. Moreover, the volume of fine capillary pore with a size of 10–100 nm increased in the MS and WMS mortar.

An innovative approach of reusing waste ceramic polishing powder generated in ceramic industries to develop admixture in cement was studied. Effects of waste polishing powder (PP) on compressive strength, pore structure, dry shrinkage ratio, heat of hydration and microstructures were studied comparing to fly ash (FA). Results show that waste polishing powder has high of pozzolanic activity than fly ash does. The cement mortar strength active index of PP is up to 83.6% and that of FA in experimental is only 72.3%. The addition of PP reduces the heat of hydration of cement and accelerates the early hydration of cement pastes. But the dry shrinkage of mortars increased obviously as the admixture of PP is increased, however, mixing compound PP and FA in mortars conduces to decrease the dry shrinkage of mortar. Microstructure analysis and mercury intrusion porosimetry of mortars further indicated that larger amount of hydration product is formed in mortars added polishing powder, which results in the low average pore diameter and the dense cement pastes.