Comparative evaluation of sand sources based on physical and morphological characteristics for cement concrete...

Sand is one of the main materials used in the construction industry and serves as a key component in cement, concrete and mortar. The quality and availability of sand play a crucial role in determining the durability and performance of structures. This study examines the suitability of locally mined fine aggregates for use in cement concrete production, focusing on seven locations around the Dar es Salaam region of Tanzania: Mpigi Magohe, Misugusugu, Ngeta, Mbagala, Mkuranga, Tegeta and Jangwani. Sand quality directly influences concrete strength and durability, making proper selection essential. Physical and morphological properties were tested per ASTM standards, including sieve analysis, water absorption, specific gravity, bulk density, moisture, silt content, and organic matter content. Scanning Electron Microscopy (SEM) was used to evaluate sand morphology. The results showed that fineness modulus ranged from 1.75 to 2.66, water absorption between 1.80 and 6.08%, specific gravity from 2.50 to 2.65, bulk density from 1489 to 1735 kg/m³, silt content between 4.14 and 11.94%, and organic matter content from 0.15 to 0.75%. Morphological analysis revealed Misugusugu sand had the best texture, low porosity and compact grains, followed by Tegeta and Mpigi Magohe, which exhibited well-balanced morphological properties, while Ngeta and Mkuranga had poor morphology and higher porosity. Among these, only Mpigi Magohe and Tegeta sands met ASTM standards for high-quality fine aggregates, suitable for concrete production with a fineness modulus of 2.54 and 2.66, water absorption of 2.4% and 1.8%, specific gravity of 2.61 and 2.63, bulk density of 1621 kg/m³ and 1554 kg/m³, silt content of 4% and 4%, and organic matter content of 0.2% and 0.3% respectively. The study recommends blending of poorly graded sands such as those from Ngeta, Mkuranga, Mbagala and Jangwani with better quality sands from Mpigi Magohe or Tegeta to achieve improved particle size distribution and reduced impurities. Washing of high silt sands is also suggested to reduce contaminants, thereby enhancing the quality of local aggregates for construction purposes.