This paper presents the experimental investigation by partial replacement of fly ash by GGBS on geopolymer bricks. The bricks were of a standard size of 190 mm x 90 mm x 90 mm. In this investigation, a geopolymer brick was prepared by the partial replacement of fly ash by GGBS (50:50), fine aggregates, and six molar concentrations of sodium hydroxide and sodium silicate (Na2SiO3) solution were used as an alkaline solution with a mass ratio of Na2SiO3/NaOH of 2.5. The geopolymer bricks were kept open to the atmosphere for 24 hours. The geopolymer brick specimen was tested for water absorption and compressive strength. The strength of the masonry depends on the strength of the component of the masonry such as bricks and cement mortar. Triplet shear bond and Single shear bond strengths was calculated. The test results showed that the compressive strength increases with 100% replacement of GGBS with fly ash. Since the minimum compressive strength of brick is limited to 3.5 N /mm2, a 50% replacement of GGBS with fly ash was studied for all the tests.