ASSESSING THE SUITABILITY OF BEACH SAND FOR ROAD CONSTRUCTION

Sand, an important fine aggregate material for mortar and mortar mixtures, plays a crucial role in construction, and its quality significantly affects the performance of buildings. Being a product of weathering and sedimentation, sand parameters will vary in their properties from one area to another. This dissertation presents a comprehensive assessment of beach sand for road construction in Monkey Bay, Mangochi. This area is characterized by different geological formations comprising basement complex rocks, including high-grade paragneisses and charnockitic granulites. This area is dominated by monazite-bearing beach sand and other minerals, including biotite-hornblende-quartz-syenites (indicative of post-orogenic, high-level types) and biotite granite (Kalk et al., 2012b). The study aimed at evaluating the grain size uniformity, organic impurities, and mineral composition of sand samples from various beach sites within Monkey Bay to determine their suitability for road construction. A purposive methodology was employed, involving the collection and analysis of sand samples from beach locations. All tests were conducted at the Malawi University of Science and Technology geology laboratory. The tests followed the standards set by the American Society for Testing and Materials (ASTM) of 2007, which acted as benchmarks for evaluating the sand quality. Grain size distribution analysis was accomplished by sieving the sand samples, organic impurity assessment used a mixture of sand samples with sodium hydroxide, and mineralogy of the sand was accomplished by hand lenses, with all tests following the ASTM procedures. From the results, there is variability in terms of grain size distribution from different locations, with some samples falling short in the required distribution, which could affect the consistency and strength of road structure. Organic impurities too had varying concentrations in different samples, with others exceeding the recommended standard, while the mineralogy showed a dominance of durable minerals of quartz and feldspar with varying little amounts of weak, flaky minerals, mostly mica.

The study aimed at evaluating the grain size uniformity, organic impurities, and mineral composition of sand samples from various beach sites within Monkey Bay to determine their suitability for road construction. Grain size distribution analysis was accomplished by sieving the sand samples, organic impurity assessment used a mixture of sand samples with sodium hydroxide, and mineralogy of the sand was accomplished by hand lenses, with all tests following the ASTM procedures. From the results, there is variability in terms of grain size distribution from different locations, with some samples falling short in the required distribution, which could affect the consistency and strength of road structure. Organic impurities too had varying concentrations in different samples, with others exceeding the recommended standard, while the mineralogy showed a dominance of durable minerals of quartz and feldspar with varying little amounts of weak, flaky minerals, mostly mica.

Monkey Bay town lies at the southern end of Lake Malawi in the Mangochi district. It is situated between latitudes 14°00′S and 14°30′S and longitudes 34°30′E and 35°00′E. The area is primarily underlain by the basement complex rocks, including high-grade paragneisses and charnockitic granulites. This area is dominated by monazite-bearing beach sand and other minerals, including biotite-hornblende-quartz-syenites (indicative of post-orogenic, high-level types) and biotite granite (Kalk et al., 2012b). A detailed assessment conducted by the Atomic Energy Division of the Geological Survey of Great Britain in 1956 identified significance deposits of these sands; Nkope 1,200 short tons, Chikowa 1500 short tons and Lungu 2700 short tons. The area has undergone significant tectonic activities, with the Rift Valley Escarpment being the dominant structural feature. (Geological survey bulletin)

Traditional authority: TA Nankumba

District: Mangochi

Coordinates: -14.28595, 34.9228