Compressive strength is considered one of the key parameters of mortar for ensuring the structural integrity and durability of masonry construction. Sand, as the primary fine aggregate in mortar, plays a crucial role in determining its mechanical properties. This study investigates the influence of sand type and fineness on the compressive strength of cement mortar cubes prepared with locally available sands in Bangladesh. Three types of sand Sylhet sand, Domar sand, and Local sand were selected for the experimental program due to their common use in construction projects. Two cement-to-sand ratios (1:4 and 1:6) were used to prepare a total of 48 mortar cubes (50 mm × 50 mm), which were cured in water for 3, 7, 14, and 28 days. The fineness modulus (FM) of the sands was determined according to ASTM C136-01, yielding values of 2.53, 2.29, and 1.72 for Sylhet, Domar, and Local sand, respectively. The compressive strength was measured using a Universal Testing Machine (UTM), and the average strength for each curing period was recorded. Results showed that Sylhet sand consistently produced the highest compressive strength across all curing ages, reaching approximately 32 MPa at 28 days for the 1:4 mix. Domar sand yielded moderate strength values, while Local sand exhibited the lowest performance due to its coarser gradation and higher impurity content. Mixtures of two sands (particularly Sylhet and Domar) exhibited synergistic effects, resulting in improved strength compared to single-sand mortars. Additionally, strength gain from 7 to 28 days was significant, with 28-day strengths approximately 60% higher on average, demonstrating the importance of proper curing. The findings confirm that sand type and grading are critical factors influencing strength development in mortar, and they provide guidance for optimizing sand selection to achieve superior mortar performance in construction practice.
Bhuiyan et al. (Fri,) studied this question.