Effects of fine aggregate types on the strength properties of building blocks

This work studied the effects of fine aggregates on the strength properties of building blocks. The fine aggregates used were sharp sand, quartz sand, granite dust and run-off sand. A cement-fine aggregate mix ratio of 1:6 and a water-cement ratio of 0.5 were used throughout the work. Sixteen hollow blocks of dimension, 450mm x 225mm x 150mmand 12 solid blocks of dimension 600mm x 150mm x 150mm were cast for each of the fine aggregate samples. The bulk density of the fine aggregates used were1600kg/m3, 1550kg/m3 , 1400kg/m3 and 1500kg/m3while the water absorption rates were 6.12%, 4.65%, 10% and 5% for sharp sand, quartz sand, granite dust and run-off sand respectively. Mixing of the particles was done manually using spades on a clean relatively impervious surface. The samples were cast on a level surface and cured by sprayingwater morning and evening for 7, 14, 21 and 28 days. For each of the curing ages, 4 samplesmade with each of the aggregate types were tested for the compressive strength of the hollow blocks while 3 samples each were tested for the flexural strength of each of the solid building blocks. The highest and lowest values of the compressive strengths of the hollow blocks which were obtained for quartz sand and granite dust block samples respectively after curing for 28 days were 5.14N/mm2 and 3.42N/mm2. For the same period of curing, the flexural strengths of 5.03N/mm2 and 2.86N/mm2 were the highest and lowest values which were obtained for blocks made with sharp and run-off sands respectively. Results of the tests show that quartz sand is an excellent alternative to sharp sand for the production of building blocks. It was concluded that the compressive and flexural strengths of building blocks are significantly affected by the type of fine aggregates used in their production.