Microstructural Observations on the Durability of Stabilized Rammed Earth

Abstract

This study provides a qualitative microstructural investigation of fly ash geopolymers' role in rammed earth's durability against water ingress and contact erosion. A series of SEM (scanning electron microscopy) images were captured on geopolymer-stabilized as well as unstabilized rammed earth samples. These samples were fabricated from predefined amounts of sand and fine materials together with fly ash geopolymers in the laboratory by static compaction to 25 MPa inside rigid molds. Two standardized durability tests were performed, namely, the dip test and the spray (also known as erosion) test. The results of these tests reflected excellent durability properties (practically zero erosion) of the stabilized material. The microscopic investigation provided an insight into the reason behind this improvement, where geopolymer networks inhabited the macro and micro pores and served as a cementing agent interconnecting the earthen materials’ grains. On the contrary, grains of the unstabilized material were weakly bonded by the clay component of the mixture, as observed with the SEM images; therefore, they were more susceptible to erosion by water.