PREPARATION OF COMPOSITES OF NATURAL-RUBBER LATEX PORTLAND-CEMENT FORMOLDS

The aim of this study was to prepare polymeric moulds using natural ru bber latex (NRL)-Portland cement (PC) composites based on a delayed-ac tion mechanism. Factors affecting the preparation process, such as con centration, mixing percentage, additives and their effects on what is regarded as a delayed-action coacervant combination were studied. Comp osites of NRL-PC for moulds were prepared as two separate parts. The s tabilized NRL (100 parts) with hydroxyethyl cellulose (HEC) 2 parts pe r 100 parts of latex (phr) as stabilizer and a delayed-action coacerva nt (sodium metasilicate as a delay agent) 5 parts per 100 parts of lat ex on the one hand and the dry blend of cement, 65 parts soluble in wa ter, as a paste on the other hand, were mixed thoroughly on the site. HEC was added to the rubber latex to prevent coagulation with the elec trolyte (sodium metasilicate) present in the mixture. Some physical pr operties of the rubber-cement mould prepared, such as shrinkage, water uptake and mechanical properties were studied. Radiation and ageing e ffects under different environmental conditions (such as under soil, u nder water and in the presence and absence of UV radiation) on the mec hanical stability of the rubber-cement composites were investigated. T he mechanical stability improved when the samples were kept under soil and under water, but deterioration was observed for samples kept in t he presence of UV radiation (sunlight). The possibility of using the r ubber-cement moulds prepared in the held of construction as crack fill ing material, expansion joint fillers and for soil injection is sugges ted. (C) 1998 SCI.