Аннотация
Abstract The production of ordinary Portland cement (OPC) is a major source of greenhouse gas emissions. With the growing demand for oil and gas well cement, the use of sustainable supplementary cementitious materials (SCMs) such as synthetic pozzolans has gained significant attention. This study examines the influence of palm oil fuel ash (POFA) and empty fruit bunch (EFB) on the performance of class G cement. The pozzolans were processed under two conditions before slurry preparation: burnt pozzolans (75 μm) and ground pozzolans (212 μm). Cement incorporating burnt pozzolans (B-pozzolans) was compared with cement containing ground pozzolans (G-pozzolans) to evaluate their effects on slurry density, compressive strength, and viscosity. Initial tests investigated 5% pozzolan replacement, followed by extended evaluations at 0%, 5%, 10%, and 15% by weight of cement (WOC). Results showed that increasing pozzolan content did not yield a linear improvement in cement strength. Strength peaked at an optimal replacement level of 10% and declined thereafter, with higher replacement levels delaying the initial hydration stage. Changes in pozzolan content also influenced slurry viscosity and density. The optimal replacement levels for B-EFB and B-POFA were identified as 5% and 10-15%, respectively. The 5% and 10% B-EFB fiber slurries exhibited relatively high viscosity, whereas 15% B-POFA cement delivered superior performance, achieving higher strength (28.76 MPa) and lower viscosity (140 cp) as compared to 100% Ordinary Portland Cement, which had a strength of 21.02 MPa and a viscosity of 145 cp. Additionally, the 15% B-POFA slurry produced only 1.75% free water and was 5.6 % less expensive to produce than 100% OPC, confirming its suitability for real-world oil well cementing applications. Overall, pozzolanic cement not only enhances strength but also reduces OPC costs, mitigates waste management issues. This study provides a detailed evaluation of the physical, rheological, and mechanical properties of palm waste, demonstrating its potential as a sustainable Class G cement additive.