Concrete brick increasingly well known as a building material, as it is considered
to be faster in its production. The use of additional materials to improve the
quality of concrete brick, one of the materials added is feldspar ash. Utilization of
feldspar ash is because currently feldspar ash is only used for ceramic
manufacture. In this research, the variations of feldspar ash composition as the
subtitution of regular sand were 0%, 25%, 50%, 75%, and 100% to the weight of
sand. Test sample of 10 cm in length, 10 cm wide, and 10 cm height for
compressive strength testing and water absorption. Compression strength test of
concrete bricks used CMT (compression machine test) at 28 days old of concrete
brick. From the result of test of compressive strength and water absorption, its
indicate that concrete brick with mixture of feldspar ash for all composition still
meets requirement according to SNI (National Standard of Indonesia) 03-0349-
1989. The average compressive strength value with replacement percentage
composition of 0%, 25%, 50%, 75%, and 100% was 25.82 kg/cm2, 33.44 kg/cm2,
44.48 kg/cm2, 65,48 kg/cm2 and 88.75 kg/cm2 which meet the criteria of solid
concrete brick grade III, II and I. Average water absorption rate with mixed
composition percentages of 0%, 25%, 50%, 75%, and 100% are 28.31%, 20.50%,
21.37%, 13.62% and 10.81% respectively.