Moreover,based on the analysis of these methods,a concept of contribution and the stiffness coefficient contributionβ, which views the contribution of rib beam towards gypsum combination mode as a kind stiffness of the structure,is proposed to calculate the reinforced concrete ribbed plaster mold combination of flat-slab system much more accurately.

Nansha Trough located in the southwestern South China Sea (SCS) is a promising area of gas hydrate resources in China, in which authigenic gypsum and pyrite assemblages in surface sediments are widely distributed.

The present paper delt with the influence of several additives such as water reducing agent of N and colloidal silica on the performances including setting time and strength and absorption rate and attack rate of modle gypsum,.

After correction,all the patterns were evaluated,so the best pattern was chosen and compared with the plaster cast and the relationship could be found.

The article analyzed the factors affecting the working life of plaster mould during the period from preparation to application and emphasized the importance of extending the working life.

This paper deals with the effect of adding polyvinyl alcohol (PVA),polyvinyl formal (PVA) and methyl cellulose (MC) on the performance of plaster mould.