Enunciation of size effect of sustainable palm oil clinker sand on the characteristics of cement and geopolymer mortars

Abstract

Palm oil clinker (POC), a by-product from palm oil industry, has gained attention as a potential sand replacement in concrete. This study focuses on the grading of palm oil clinker sand (POCS) as a whole replacement of conventional sand in cement and geopolymer mortars. Fly ash (FA) and ground-granulated blast-furnace slag (GGBS) were used as binders and activated with a Na2SiO3/NaOH ratio of 1.5 in geopolymer mixes. Four different gradings of POCS with a maximum size of 4.75, 2.36, 1.18, and 0.60 mm, along with a control mix with the utilization of Mining sand (MS), were used to cast a total of 10 mixes for cement and geopolymer mortars. The microstructure of the POCS was analysed, and engineering properties of mortars were investigated through flow table test, compressive and flexural strengths, density, drying shrinkage, water absorption and sorptivity tests, and SEM images. The results revealed that mixes with the incorporation of finer POCS particles produced better compressive, flexural, and water absorption values, while the opposite was experienced in terms of drying shrinkage. Overall, the density of the mixes incorporating POCS was reduced by up to 20% and POCS geopolymer mortars produced higher strengths than those of cement. A 28-day compressive strength of 55–65 MPa was produced with the utilization of POCS in geopolymer mortar under the ambient temperature of 26–28 °C.