MECHANICAL PERFORMANCE OF COMPRESSED STABILIZED EARTH BRICK MASONRY WITH FOUR MORTAR TYPES: A COMPARATIVE EXPERIMENTAL STUDY

Abstract

Compressed stabilized earth bricks (CSEBs) offer a locally adaptable alternative to fired masonry, but wall-level performance depends strongly on the interaction between the earth units and mortar. This study experimentally evaluated the effect of four mortar systems-mud mortar, cement-stabilized mud mortar, cement-sand mortar 1:6, and cement-sand mortar 1:3-on the mechanical performance of CSEB masonry. The experimental program comprised three types of mechanical tests. Twelve masonry specimens measuring 4 ft × 4 ft were prepared and tested for diagonal shear strength. Twelve smaller masonry specimens measuring 1.5 ft × 1.5 ft (18 in × 18 in) were prepared and tested for compressive strength. In addition, 12 direct shear (triplet) specimens were prepared for each mortar type to evaluate the shear/bond behavior at the masonry joint, following the testing standard adopted in the thesis. The reported mean compressive strengths were 1.85, 3.12, 4.45, and 5.68 MPa for mud, stabilized mud, 1:6, and 1:3 mortar, respectively. Mean diagonal shear strengths were 0.12, 0.24, 0.38, and 0.52 MPa, while mean direct shear strengths were 0.10, 0.22, 0.34, and 0.48 MPa, respectively. Reanalysis of the reported replicates per group showed statistically significant between-group differences for all three outcomes (one-way ANOVA, p < 0.001). However, the relatively limited number of specimens used for some test categories requires cautious interpretation of the statistical findings. The results demonstrate a consistent increase in measured masonry strength with the transition from unstabilized mud mortar to stabilized mud and cement-sand mortars. The findings support mortar selection as an important design variable in CSEB masonry and indicate that stabilized mud mortar can provide a substantially stronger alternative to unstabilized mud mortar while retaining lower material intensity than conventional cement-rich mortar systems. Long-term durability, environmental life-cycle performance, seismic response, and field validation were outside the scope of the present study.