Karakterisasi Sifat Mekanik Statik dan Pola Retakan Beton dengan Diperkuat Abu Cangkang Sawit dan Fly Ash

Abstract

The utilization of Fly Ash and Palm Oil Fuel Ash (POFA) as alternative constituent materials for mortar represents a strategic solution to support sustainable construction concepts. This study aims to analyze the effects of Fly Ash and POFA addition on the physical properties, mechanical properties, crack patterns, and microstructural characteristics of mortar. An experimental design was employed using variations of Fly Ash (0% and 5%) and POFA (0%, 5%, 10%, and 15%) as cement replacement materials. Testing included slump flow, density, absorption, compressive strength, and splitting tensile strength at 28 days, supplemented by microstructural analysis using Scanning Electron Microscope - Energy Dispersive X-ray Spectroscopy (SEM-EDS). The results indicated that the combination of Fly Ash and POFA significantly enhanced mortar performance. The resulting densities ranged from 2,080.63 kg/m³ (M22) to 2,234.23 kg/m³ (M24). The optimum composition was achieved in the M24 variation (5% Fly Ash + 15% POFA), which yielded a maximum compressive strength of 50.67 MPa and a splitting tensile strength of 6.66 MPa, classifying it as high-strength concrete. Crack pattern analysis showed a transition in failure mechanisms from bond cracks in the control sample to shear cracks in the optimum sample. These findings were validated by microstructural analysis, which revealed a highly dense C-S-H matrix morphology dominated by Silica (≈56.7%) and Calcium (≈29.4%) compounds resulting from the pozzolanic reaction.