JOURNAL OF SCIENCE TECHNOLOGY AND EDUCATION 13(2), JUNE, 2025 ISSN: 2277-0011; Journal homepage: www.atbuftejoste.com.ng Corresponding author: Musa Ibrahim musa.ibrahim@bazeuniversity.edu.ng Department of Civil Engineering, Faculty of Engineering, Baze University, Abuja, Nigeria. © 2025. Faculty of Technology Education. ATBU Bauchi. All rights reserved 508 Comparative Analysis of the Compressive Strength of Metakaolin Sandcrete Blocks and Sandcrete Blocks Incorporating Selected Supplementary Cementitious Materials Musa Ibrahim Department of Civil Engineering, Faculty of Engineering, Baze University, Abuja, Nigeria ABSTRACT This paper examines the effect of partially substituting metakaolin (MK) and some selected supplementary cementitious materials (such as Olive Seed Ash, Maize Cob Ash, Millet Husk Ash, and Guinea Corn Husk Ash) for cement on the hollow Sandcrete blocks compressive strength. Sandcrete hollow blocks measuring 225 x 225 x 450 mm were made using a 1:6 mix ratio, which is one part cement to six parts fine aggregate (sand). The study was carried out by comparing the compressive strength of Sandcrete blocks produced at 10% and 20% replacement of Metakaolin and other selected supplementary cementitious materials to assess the impact on the hollow Sandcrete block’s strength. The result of compressive strength of metakaolin and some selected SCMs was analyzed and compared after 28 days of curing. The compressive strength of all the SCM-based hollow Sandcrete block samples for this study ranges from 2.16 N/mm² and 4.50 N/mm² at 0% (control), 1.73 N/mm² and 4.05 N/mm² at 10%, and 1.50 N/mm² and 3.15 N/mm² at 20% replacement of cement with SCM. Sandcrete blocks made with Millet Husk Ash had the highest compressive strength, followed by those made with Maize Cob Ash, Olive Seed Ash, Metakaolin and Guinea Corn Hush Ash with 4.50, 4.30, 3.82, 3.51 and 2.16 N/mm² respectively which meet the requirement specified by Nigeria Industrial Standard NIS 87 (2000), BS 6073, and National Building Code (2006) except Guinea Corn Hush Ash and are adequate for usage as non-bearing and load- bearing structures in areas where moisture infiltration may occur. Sandcrete blocks produced at 20% replacement of cement with SCM can all be used as non-bearing walls except Guinea Corn Hush Ash, which does not meet the minimum requirement specified by various codes. It can be concluded that 10% and 20% replacement of cement with other SCM can be effectively substituted with 10% and 20% as cement in structural Sandcrete blocks, and the quality of materials will not be compromised. INTRODUCTION Sandcrete block is a composite construction material primarily made up of cement, sand, and water, which are moulded into a variety of sizes (Odeyemi et al., 2018). Despite the introduction of new materials like life bricks and modified clay blocks, Sandcrete blocks appear to be an improvement over the currently available materials. The construction industry is a vital economic sector in developing countries like Nigeria. Sandcrete blocks are widely used in Nigeria and virtually all African countries for the ARTICLE INFO Article History Received: December, 2024 Received in revised form: January, 2025 Accepted: May, 2025 Published online: June, 2025 KEYWORDS Ash, Compressive Strength, Metakaolin, Sandcrete Blocks, Supplementary Cementitious Materials