Silicon carbide waste as a source of mixture materials for cement mortar

This paper presents an investigation of the feasibility of recycling silicon carbide waste （SCW） as a source of mixture materials in the production of cement mortar. Mortars with SCW were prepared by replacing different amounts of cement with SCW, and the properties of the resulting mortars, such as the fluidity, strength and shrinkage, were studied in this work. Thermogravimetry-differential scanning calorimet;＇y and scanning electron microscopy were employed to understand the reasons for the property changes of the mortars. The results indicate that SCW decreases the initial and l-h fluidity of fresh mortar but improves the loss of fluidity. The mortar with SCW exhibits a lower strength at 3 d and7 d but a higher strength at 28 d and 56 d compared to the control. The shrinkage rate of cement mortar with SCW shows an obvious decrease as the replacement ratio increases. In addition, the content of calcium hydroxide in hardened paste also shows that SCW has some impact on the hydration of the cement-SCW system. The microstructures of the hardened paste also show evidence for a later strength change of mortar containing SCW. This work provides a strategic reference for possibly applying SCW as a mixture material in the production of cement mortar.

Preparation Process and Properties of Porous Ecological Concrete

By using waste bricks as aggregate,a kind of porous ecological concrete was prepared and the mixing technique and its properties were studied. Effects of the cement paste fluidity on workability of the porous ecological concrete were investigated,and influences of the water-cement ratio,the aggregate-cement ratio and the aggregate size on compressive strength and porosity of the porous ecological concrete were also discussed. Results show that for preparation of the porous ecological concrete,the aggregates should be enveloped with neat cement paste,and recommended fluidity of the cement paste is 200～235 mm. With the increasing of the aggregate-cement ratio,porosity of the porous ecological concrete increases while the 28 d compressive strength decreases. With increasing of the water-cement ratio,porosity of the porous ecological concrete decreases. And relationship between compressive strength and water-cement ratio of the porous ecological concrete does not follow Bolomey's formula. As a result of this study the porous ecological concrete is prepared,its porosity is 38.93%,the water absorption is 11.39% and the compressive strength is 1.14 MPa.