Optimizing environmentally efficient mortar properties through synergistic integration of cellulose microfibers and calcined palm oil fuel ash: A response surface methodology technique

Cement mortar is susceptible to microcracks due to various environmental factors, including weathering and chemical exposure. To address the issue, this study examines how calcined palm oil fuel ash (CPOFA) and cellulose microfibers (CMF) can be utilized to sustainably enhance the properties of cement mortar. By addressing the dual objectives of reducing cement consumption and finding productive uses for palm oil industry waste, this research addresses an important environmental challenge. Previous attempts to improve the performance of palm oil fuel ash (POFA) in cement-based materials through chemical and thermal modifications have not fully achieved the desired outcomes. To overcome these limitations, this research integrated CPOFA with CMF, leveraging their combined effects to enhance mortar performance. Using a user-defined option of response surface methodology (RSM), the study designed and tested nine different mortar mixtures, with CMF additions from 0 % to 2 % and CPOFA replacements of cement between 0 % and 40 %. These mixtures were evaluated for mortar flow, compressive, flexural, and splitting tensile strengths. Additionally, microstructural examination and X-ray diffraction (XRD) tests were conducted on selected samples to gain deep insight into the material interactions. The compact scanning electron microstructure coupled with high XRD peaks of Tobermorite and Portlandite from the XRD analysis of 1CMF-20CPOFA mortar sample maximized the development of dense cementation products due to its cementation reactions. The findings revealed that while increasing CPOFA content reduced both fresh and hardened mortar properties (mortar flow decreased from 90 % to 23 % at 0-40 % CPOFA), the addition of CMF significantly improved workability and strength, particularly at CMF contents between 1 % and 2 % and CPOFA levels below 20 %. At 20 % CPOFA, increasing CMF content from 0 % to 1 % enhanced 28-day compressive strength from 53 to 62 MPa, flexural strength from 5.3 to 6.6 MPa, and splitting tensile strength from 2.66 to 2.83 MPa. Through multi-objective optimization, the study identified the ideal mix ratios of 1.7 % CMFs and 11.3 % CPOFA, which were experimentally validated. The experimental results for the responses, including mortar flow, compressive strength, flexural strength, and splitting tensile strength, showed absolute relative deviations of less than 10 % from the corresponding predicted response values generated by the optimization. This approach not only demonstrates a more effective use of CPOFA but also highlights a sustainable, high-performance alternative for construction materials.