Abstract:The compressive performance of grouted mortarless masonry prisms strengthened with glass fiber-reinforced polymer (GFRP) composites was investigated in this study. A total of 18 grouted mortarless masonry specimens, i.e., nine strengthened with GFRP (called G-GMM) and nine without GFRP (called GMM), were tested under uniaxial compression. The effect of grout strength on the compressive strength of the prisms was discussed. Moreover, the effect of GFRP on the cracking load, modulus of elasticity, ultimate bearing capacity, failure modes, compressive stress-strain behavior, and deformation behavior of the specimens was analyzed. The test results indicated that GFRP strengthening increased the ratio of initial cracking load and ultimate load bearing capacity of mortarless masonry to a great extent, i.e., the ratio is 50-80% for G-GMM and 40-65% for GMM. In addition, GFRP clearly improved the deformation capability of the GMM. The tested experimental data were in good agreement with the predicted values using classic expressions.