Papers by Author: Ke Chen

Abstract: The set of alkali-activated slag cement (AASC) and concrete and the measures for set-retarding were reviewed. Due to the fast set of high and super high strength alkali-activated slag cement and concrete, an inorganic compound set retarder YP-3 was developed. The effect of the retarder on setting time and strength as well as heat evolution of AASC were tested, and the mechanism of the retarder was analysed. Results show that the retarder can regulate the initial set of high strength AASC in the range of 29hrs with little negative effect on its strength development. The retarder could react with silicate ions from liquid to rapidly form a compact film in early age of hydration of AASC, the film covered the surface of slag and obstructed R+ and OH- in contact with slag particle directly. Consequently the set of AAC was delayed.

Abstract: The composite coatings of self-flux alloy matrix reinforced by WC-12%Co were produced on the surface of 45 steel using laser cladding technology. The effects of CeO2 to macro-morphology, microstructure, hardness, wear resistance and corrosion resistance of cladding layer were investigated. The results show that rare earths oxide (CeO2) added laser cladding coating has distribution, dimension phases and less deficiency. CeO2 could promote liquating process of WC, increasing the quantity and distribute uniformity of intermetallic compounds in laser cladding layer. Because of dispersion precipitation and fine-crystal strengthen effect, laser cladding layer with CeO2 has higher microhardness, wearing resistance and better corrosion resistance properties.

Abstract: In this paper, the influence of the types and addition dose of MgO expanding agent and the age of cement on expansion value and expansion performance of cement based material added with MgO expanding agent was systematically studied.The expansion characteristics of cement based material added with MgO expanding agent or calcium sulphoaluminate expanding agent were compared. The expansion of such material increases with the addition dose of MgO expanding agent and cement mortar age. During the test period, the expansion of cement based material increases continuously. The light-burned MgO expanding agent modified by CaO expanding agent is able to increase the 28d expansion of such material effectively. The temperature of calcination for the heavy-burned MgO expanding agent is higher than that of light-burned one, thus the heavy-burned MgO expanding agent has a rather dense structure with slow hydration rate and gives a small expansion of the cement based material at early age, showing an obvious expansion delay. The calcium sulphoaluminate expanding agent gives most expansion of the material in the early 28d and there is small expansion at middle and later age of the material.

Abstract: The slag is used as solid dispersing component with addition of a little amount of alkali component, a clinker free, alkali activated slag cement based ecomaterial (AASCBE) has been developed. The experiment results showed that the alkali activated slag cement based ecomaterial has excellent mechanical performances and durability, i.e., low energy consumption in manufacture, low environmental pollution, increased utilization of solid waste, enhanced efficiency of solid waste utilization, the heat from waste tyre or municipal domestic waste burning can be used for the material production, the CO2 can be recycled as a resource for the material curing and making the regeneration and recirculation possible. LCA study of this material shows that the complex environmental index of the alkali activated slag cement based ecomaterial is 2.9337×10-12 year/ton, which takes only 19.8% of that for Portland cement or 25.9% of that for slag cement, such material has certain environmental compensation function, therefore it is a new ecomaterial with excellent environmental coordination.