The Use of Rapid Setting Mortar as Floor Leveling in Polyurethane Coating

Abstract

The purpose of this paper was to determine rapid setting mortar mix design for the use as a leveling layer in polyurethane floor coating. Rapid setting mortar required superplasticizer and accelerator to satisfy with the flow rate of mortar within 130±5 percent and compressive strength of mortar not less than 200 and 400 ksc at 8 hours and 24 hours, respectively. For at least 95% probability of passing the required compressive strength, target means should be 217 ksc and 435 ksc, respectively. Then mortar mix proportions were designed according to the ACI 211.1-91 method. Then mortar mix proportions obtained were examined with the flow table test, the compression test and the tensile test. The mortars were cast within a range of atmospheric temperatures, 29-32°C,    32-34°C and more than 34°C.  Results from the study showed that the optimum mortar proportion was water to cement ratio of 0.35, Portland cement type 3 content of 588 kg/m³, superplasticizer 1.2% by weight of cement, and the accelerator 0.28% by weight of cement. The mortar reached compressive strength 217 ksc in 8 hours for the casting temperature 29°C-32 °C. And at 24 hours, mortar could reach compressive strength of 435 ksc at all of temperature ranges without adding accelerator. Although the tensile strength of the rapid setting mortar was less than polyurethane,     in the application of the rapid setting mortar as floor leveling layer together with the polyurethane coating, no crack or peeling at the surface was found. Thus, rapid setting mortar might be used as floor leveling in place of the polyurethane composite at the much lower cost of construction