Effect of silica fume and MIRHA on thermal conductivity of cement paste

Increased usage of air-conditioners in buildings leads to higher levels of electricity and energy consumption. Thermal insulation improves energy-efficiency of buildings by retarding heat flow through building envelopes and thus reducing indoor cooling load. This research investigates the potential of two cement replacement materials, which are silica fume and Microwave Incinerated Rice Husk Ash (MIRHA), incorporated in cement paste as thermal insulation. Samples of cement paste with varying volumes of silica fume and MIRHA were prepared and evaluated on their thermal conductivity values. Their viability as building materials were then evaluated by measuring their permeable porosities and compressive strengths at three (3), seven (7) and 28 days of curing. Results show that higher dosage of silica fume and MIRHA in cement paste lead to lower thermal conductivity but negatively affect compressive strength and permeable porosity. MIRHA reduces thermal conductivity more efficiently than silica fume but leads to a faster decline in compressive strength and increase in permeable porosity. The lowest thermal conductivity value obtained in this experiment was 0.4273 Wm-1K-1, which was achieved by samples with MIRHA incorporated at 25% of cement paste volume.