Thermal insulation enhancement of rammed earth using wood fly ash and calcium bentonite

Abstract

This study evaluates the effect of chemical additives such as cement, wood fly ash, and calcium bentonite on the mechanical and thermal insulation of rammed earth (RE) material in vernacular buildings with low carbon footprint. Compacted and cured hollow RE samples were used for measuring the decrement factor, time lag, and peak temperature as part of the material's thermal properties. The results show the greatest improvement in UCS = 9.35 MPa was obtained by adding 10 % cement and 5 % fly ash after 28 days of curing. The most extended time lag was measured at 10 % cement, 10 % fly ash and 15 % Ca-bentonite (114.28 min), 10 % cement, 5 % fly ash and 15 % Ca-bentonite (73.67 min), and 5 % cement, 5 % fly ash, and 15 % Ca-bentonite (130.35 min) in hot environment with ideal humidity, hot and humid environment, and cold climate, respectively. On the other hand, the lowest decrement factor was found after 5 % cement, 10 % fly ash, and 15 % Ca-bentonite incorporation in a hot environment with ideal humidity (0.7239), 5 % cement and 5 % fly ash incorporation in a hot and humid environment (0.7778), and 5 % cement, 5 % fly ash, and 15 % Ca-bentonite incorporation in a cold climate (0.6874). The optimum mixture varied depending on the applications, such as required strength and climatic effects.