Composite particle size–absorption index (CPSAI) for preliminary assessment of crushed stone manufactured sand for concrete applications

The increasing scarcity of natural river sand has necessitated the widespread use of crushed stone manufactured sand (M-sand) in concrete and mortar applications. M-sand, however, exhibits considerable variability in grading, micro-fines content, and water absorption, making it challenging to assess suitability using conventional standards such as ASTM, IS, BS etc. which focus mainly on definite grading zones. A Composite Particle Size–Absorption Index (CPSAI) is proposed that integrates water absorption (WA), fineness modulus (FM) and with percentages passing the 600 μm and 150 μm sieves into a single dimensionless index. This study presents a preliminary comparative assessment of M-sand suitability for use as fine aggregate in concrete. In routine concrete mix design practice, detailed characterization of fine aggregates is often limited to basic parameters such as sieve analysis, water absorption, and specific gravity. The proposed CPSAI utilizes commonly available test parameters and integrates them into a single index that captures key grading and absorption characteristics of manufactured sand, thereby enabling a rapid preliminary assessment of its suitability for concrete applications. Twenty M-sand samples from different sources were tested in the laboratory. CPSAI enables ranking of samples based on overall suitability, demonstrating a simple yet effective method to screen M-sand sources. The sensitivity of the index to variations in grading and absorption parameters is discussed to demonstrate its applicability as a screening tool for preliminary material selection. The proposed index was further validated using 28-day compressive strength results of mortar specimens, indicating a strong correlation between CPSAI and mechanical performance. However, CPSAI is intended as a preliminary comparative screening tool and should not be considered a direct predictor of concrete performance without further validation using larger datasets and comprehensive concrete performance tests. The study highlights the practical applicability of CPSAI for engineers and researchers and identifies high, medium, and low-performing sands for potential use in concrete and mortar.