Abstract
The use of precast concrete structural systems in the Indonesian civil engineering industry is expected to increase due to the continuous annual need of buildings and infrastructures for social and economic development. The fabrication of the precast concrete requires the use of sand with 5% suitable sludge content as one of the important raw materials but it is difficult to find a low-cost method of obtaining this sand in several regions of the country. However, the available high sludge content has been discovered to be reducing aggregate adhesion with cement paste and requires more water in the concrete mixture, thereby, causing a reduction in its compressive strength. This study tested the use of natural sand with a high sludge content of 12.7% and different variations of OPC at 2.5, 5.0, 7.5, and 10.0% in CS1, CS2, CS3, and CS4 samples, respectively, to determine the compressive strength and workability of the precast concrete structure. Moreover, two samples were used as controls and they include Ref-1 with 3.7% sludge content and Ref-2 with 12.7% sludge content without the addition of OPC. The results showed the addition of at least 2.5% OPC into concrete slurry is recommended to ensure optimal performance of the CCS samples. This means combining local natural sand, despite its high sludge content, with other materials is reliable for the fabrication of precast concrete structure in future civil engineering applications.
