Utilization of Kelut’s Volcanic Ash as the Aggregate Mixture of Concrete Brick

Kelut volcano had erupted in February 2014. The eruption has produced various materials i.e. ash, sands, etc. Volcanic ash contains various elements such as Si, Al, Ca, Fe, Na and P. It is potential to be used as raw material for cement-based products. This study investigates the utilization of Kelut’s volcanic ash as the raw material of cement-brick. The Kelut’s volcanic ash was analyzed to determine the contents of iron (Fe), aluminum (Al), and silica (Si). The volcanic ash was screened to obtain 100 mesh size of ash. The volcanic ash of 100 mesh size was mixed withcement, sand, and water with ratio of 1 kg cement, 2 kg volcanic ash, and 15 kg sand (1 :2 :15). Themixture of volcanic ash, sand and cement was poured and pressed in the concrete brick mold. Theconcrete brick was then aerated in a room for hardening process. The experiment was repeated foranother ratio of raw material (cement: volcanic ash: sand = 2:1:15) and the age of the concrete brick(46, 61, 75 and 89 days). Concrete bricks were analyzed to determine the quality and the mechanicalcharacteristics. The results has shown that Kelut’s volcanic ash has a composition of aluminum (Al)4.707%, silica (SiO2) 23.4%, and iron (Fe) 3.85%, that is like the composition of the cementmaterials. The concrete bricks which are made of cement, Kelut’s volcanic ash, and sand with theratio of 2:1:15 has a maximum compression strength of 18.85 MPa at the age of 89 days. Theaddition of Kelut’s volcanic ash has improved the strength of concrete brick. However, too muchvolcanic ash will lead to increasing compression strength