The aim of this study was to prepare polymeric moulds using natural rubber latex (NRL)ÈPortland cement (PC) composites based on a delayed-action mechanism. Factors a †ecting the preparation process, such as concentration, mixing percentage, additives and their e †ects on what is regarded as a delayedaction coacervant combination were studied. Composites of NRLÈPC for moulds were prepared as two separate parts. The stabilized NRL (100 parts) with hydroxyethyl cellulose (HEC) 2 parts per 100 parts of latex (phr) as stabilizer and a delayed-action coacervant (sodium metasilicate as a delay agent) 5 parts per 100 parts of latex on the one hand and the dry blend of cement, 65 parts soluble in water, 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 electrolyte (sodium metasilicate) present in the mixture. Some physical properties of the rubberÈcement mould prepared, such as shrinkage, water uptake and mechanical properties were studied. Radiation and ageing e †ects under di †erent environmental conditions (such as under soil, under water and in the presence and absence of UV radiation) on the mechanical stability of the rubberÈcement composites were investigated. The mechanical stability improved when the samples were kept under soil and under water, but deterioration was observed for samples kept in the presence of UV radiation (sunlight). The possibility of using the rubberÈcement moulds prepared in the Ðeld of construction as crack Ðlling material, expansion joint Ðllers and for soil injection is suggested.
1998 SCI.