Durability of Rammed Earth Materials

Abstract

Rammed earth (RE) is a low-embodied-energy construction technique that attracted the attention of engineers in recent years. To date, few studies have investigated the chemical deterioration of RE. This study investigated the durability of cement-stabilized rammed earth (CSRE) for 1 year under aggressive environments. Three cement contents were considered for preparing the CSRE specimens. They were exposed to acidic, alkaline, sulfate, and high-moisture environments. The mechanical properties of the CSRE specimens were determined at intervals of 1, 3, 6, 9, and 12 months of immersion in solutions. Results revealed that the sulfate environment was the most destructive solution for the CSRE specimens, which caused complete degradation of low-cement specimens and significantly decreased the compressive strength of high cement content CSRE. Scanning electron microscopy demonstrated the formation of ettringite for specimens submerged in sulfate solution. CSRE with small cement content was also completely disintegrated after 6 and 9 months of exposure in alkaline and acid environments, respectively. However, the acidic environment did not considerably affect the compressive strength of higher cement content CSRE, and the alkaline environment improved the compressive strength. Mathematical relationships are proposed between the compressive strength, Young's modulus, and ultrasonic pulse velocity for higher cement content specimens. Finally, multiobjective optimization by desirability function was used to minimize the cement content and maximize the compressive strength, simultaneously.