Recycling phosphogypsum as the sole calcium oxide source in calcium sulfoaluminate cement production and solidification of phosphorus.

Because the disposal of phosphogypsum (PG) can lead to serious contamination of the air, soil, and water, recycling of PG has attracted wide attention. This study investigated the effect and solidification of phosphorus in the production of calcium sulfoaluminate (CSA) cement using PG as the sole CaO source. The effects of three phosphorus impurities (Ca(PO), CaHPO, Ca(HPO)) on the decomposition of CaSO, formation of minerals, microstructure of the clinker, and the hydration and mechanical properties of the cement were studied.

Recycling phosphogypsum as a sole calcium oxide source in calcium sulfoaluminate cement and its environmental effects.

As the disposal of phosphogypsum can result in severe contamination of soil and groundwater, several researchers worldwide have devoted efforts toward realizing suitable methods for PG disposal. This study demonstrates the feasibility of using phosphogypsum as the sole CaO source in the preparation of calcium sulfoaluminate cement by considering its mechanical properties and the potential environmental impacts of its large-scale utilization. First, the effects of the alumina/silica ratio on the mineral phase formation, setting time, compressive strength, and microstructure of calcium sulfoaluminate cement were studied.

Population-based sexual behavior surveys in China: Liuzhou compared with other prefectural cities.

Sexual behaviors in China are rapidly changing; simultaneously, sexually transmitted infections (STI)/HIV prevalence is increasing in the general population. To investigate these major shifts, we examined sexual behaviors and self-reported STI in one prefectural city in southern China, Liuzhou, and compared it to other prefectural cities throughout China. We used adults age 18-39 from two sets of population-based surveys that paralleled each other in both content and method.