Effects of curing and processing on strength of raw earth stabilized with lime and sodium silicate

Earthen construction has attracted much attention in recent years, given that it offers many environmentally friendly features. Extensive works have been conducted to optimize the binder type or dosage in stabilization of raw earth, but the effects of curing and processing are often overlooked. This investigation targets to understand the strength performance of raw earth after curing and/or processing. The testing matrix contains variables of two binders (lime and sodium silicate), six densities, five curing ages, two curing conditions (natural and steam), two processing approaches (extrusion and rolling), and seven processing cycles, in which a total of 324 raw earth specimens are prepared. Analyses with scanning electron microscope are also conducted to interpret the stabilization mechanism. Results show that the strength of raw earth are positively correlated with the density. The highest strength gain is obtained at 28 days curing for both lime and sodium silicate stabilization. Upon natural curing, the mass loss increases over time, as well as the strength; upon steam curing, the mass increases with the curing age, but it can lead to a reduction in strength. The implementation of processing promotes the strength gain, and the optimal processing cycle is determined as 15–20 and 10–15 times for extrusion and rolling, respectively.