Engineering and mineralogical characteristics of stabilized unfired montmorillonitic clay bricks

This paper presents engineering and mineralogical characteristics of stabilized unfired montmorillonitic clay bricks treated by different curing methods. Quicklime (up to 30 wt.%) and Portland cement (up to 15 wt.%) at different proportions were used as stabilizers to Egyptian montmorillonitic clay in clay-based mixtures. Sand was used in the formulations of the unfired clay brick specimens. The formulated clay specimens were treated by moisture and spray techniques until 90 days of curing. The laboratory unfired stabilized clay specimens were identified using X-ray diffraction technique. In addition, physical and mechanical properties were measured according to the Egyptian Standard Specification (ESS) 1234-2005 and evaluated in accordance with the Egyptian Code for Building Units (ECP) 204-2005 to ensure the quality and impact of the made unfired clay specimens. The quantification of the formed phases demonstrated a detrimental effect of calcium silicate hydrates (C-S-H), portlandite (Ca(OH)2) and calcite (CaCO3) phases in the studied samples. The physico-mechanical results of the specimens cured by the moisture method were higher than those treated by the spray of the same sample. In all cases, the test results suggested that cement amended specimen properties rather than lime. Moreover, as explained from the obtained physico-mechanical properties, calcium hydroxide generated from the hydration of cement is more reactive than that from the hydration of the added lime. Also, it is recommended to use the suitable mixture for rural building construction in tropical countries