Optimizing Cement Use in Sustainable Sandcrete Blocks: Standardizing Low-Strength Mortar Testing and Evaluating BYF Cement Feasibility

Abstract

The urgent demand for sustainable and cost-effective construction materials has prompted the exploration of alternative binders to conventional Portland cement. However, a significant methodological gap persists, where alternative binders intended for low-strength mortars are often evaluated using the EN 196-1 standard, which is designed for high-strength cementitious systems and thus not representative of low-strength performance contexts such as sandcrete block production. This study investigates the technical feasibility of Belite-Ye'elimite-Ferrite (BYF) cement as an alternative binder for low-strength applications, with a particular focus on sandcrete block production for sustainable construction in Sub-Saharan Africa. It introduces a modified testing methodology that adapts standard procedures to the low-strength context. Key modifications include the use of mix design representative of low-strength mortar anchored on bulk density control, and a reduction in specimen replicates from six to three to reflect the operational characteristics of tailored adjustments to casting and compaction protocols. Experimental results demonstrate that BYF cement specimen at 7% cement content and 14% water content achieves a comparable 1-, 7- and 28-day compressive strength to Portland cement specimen at 7% cement and 11% water (4.5MPa, 5.2 MPa, and 6.7 MPa vs 1.9 MPa, 4.1 MPa, and 6.1MPa respectively), with improved repeatability and reduced variability in test outcomes. Further analysis shows that BYF at 5% cement content and 11% water content achieves a comparable result (3.73 MPa, 6.3 MPa, and 6.7 MPa respectively). XRD analysis confirms early and sustained strength development, supporting its viability as a low-carbon alternative binder. Regression analysis further established a moderate correlation (R² = 0.4046) between bulk density and compressive strength, with compaction shown to be a critical variable. The findings support the technical feasibility of BYF cement as a low-carbon alternative for low-cost housing applications and proposes a reproducible testing methodology for evaluating low-strength binders. However, further research is needed on durability performance, field application, and economic feasibility to support broader adoption. Key words: BYF cement, Portland Cement, Low-strength Application, Sustainable Sandcrete Blocks, EN 196-1 Modified Testing Method, Compressive Strength, Bulk Density, Sub-Saharan Africa, Cement Hydration.