Penggunaan Cangkang Kemiri Sebagai Bahan Penambah Sebagian Agregat Kasar Terhadap Kuat Tekan Beton

Abstract

The continuously increasing demand for coarse aggregate in concrete construction impacts natural resource exploitation, necessitating eco-friendly material alternatives such as candlenut shell waste. This study aims to determine the effect of adding candlenut shell waste on the compressive strength of concrete with a target strength of 25 MPa and to identify the optimal mixture percentage. The research method applied was laboratory experimental. A total of 12 cylindrical specimens measuring 150 x 300 mm were utilized, divided into 4 mixture variations (0%, 2%, 4%, and 6% by weight of coarse aggregate) with 3 samples each. Compressive strength testing was conducted at 28 days according to SNI 03-1974-2011 standards. Data were analyzed using comparative descriptive analysis by comparing the mechanical properties of each variation against normal concrete. Results indicated that adding candlenut shells tended to decrease compressive strength as the mixture percentage increased. The 2% variation yielded an average compressive strength of 24,98 MPa, 4% yielded 24,70 MPa, and 6% yielded 23,97 MPa. Although candlenut shells did not increase compressive strength, the 2% proportion was most optimal, closely approaching normal concrete (25,24 MPa). The strength reduction was caused by the lightweight and porous nature of candlenut shells affecting concrete density.