Yongjia He

Preparation and Properties of Alkali-Activated Ground-Granulated Blast Furnace Slag Thermal Storage Concrete

Thermal storage concrete is prepared by using alkali-activated ground-granulated blast furnace slag as cementitious material. To improve thermal conductivity, graphite aggregate is used to replace part of the coarse aggregate, and, furthermore, polypropylene fiber is added to improve the heat resistance performance of the concrete. The compressive strength of concrete specimens before and after heating (up to 450 °C) was tested, and, furthermore, scanning electron microscopy was used to investigate the structure alteration due to heating. Results showed that the partial replacement of coarse aggregate by graphite block could obviously improve the thermal conductivity of the thermal storage concrete. At the same time, the specimen with 30% graphite aggregate replacement still exhibited good mechanical properties. The mechanism of the high residual strength was investigated.

Effect of polymer on morphology and structure of calcium silicate hydrate prepared via precipitation method

The effects of polyacrylamide (PAM) and polyvinyl alcohol (PVA) on morphology and structure of calcium silicate hydrate with C/S 1.0–1.7 prepared via precipitation in solution were investigated by XRD, FT-IR and TEM techniques. The results show that incorporation of the polymers decreased the order degree, increased the interlayer spacing and disturbed the layered stacking of C-S-H. Interlayer spacing expansion depended on C/S ratios and type of polymer. Interlayer spacing expansion had a minimum at C/S 1.0 and a maximum at C/S 1.3 and 1.5. Interlayer spacing expansion of PAM was bigger than that of PVA with the same C/S. C-S-H added with PVA mainly exhibited foil-like and fibrillar morphology. The fibrils were of variable length from a few tens of nanometers to a few hundreds of nanometers. Fibrils or foils seemed to be longer in the presence of PVA.

Porous haydite used as waste water filter medium for lake sludge

Porous haydite used as waste filter medium was prepared by dreging lake sludge to help solve the treatment problem of sludge and realize its reclamation. Several calcination regimes were considered and their effects on the pore structure and the properties such as the strength, the density, the filtering ability and the phosphate absorption ability of the haydite were investigated. For the mixture of 60% lake sludge and 40% fly ash in this experiment, the calcination regime with a pre-calcination period at about 600 °C, a temperature keeping period at 1 200 °C and a moderate cooling rate are recommended to prepare haydite with reasonable pore structure and good performances for its usage as the waste water filter media.