Suitability of Saw Dust Ash-Lime Mixture for Production of Sandcrete Hollow Blocks

The use of saw-dust ash (SDA) mixed with 45% slaked lime for production of sandcrete hollow blocks was investigated. The aim was to determine the percentage SDA lime and water-cement ratio that would give the 28-day maximum strength. Saw dust was burnt and the ash sieved using a 150 micrometer sieve. The ash mixed with 45% slake lime was used to partially replace ordinary Portland cement (OPC) in various proportions. Fifteen blocks for each proportion were moulded using the mix of 1:8 and water-cement ratio of 0.50. Sprinkling of water on the blocks commenced after three days. The blocks were cured by complete immersion in water at room temperature. Three blocks were tested for strength at each of the ages of 7, 14 and 28 days for each proportion of OPC/SDA-lime. The 90:10 (cement: SDA-lime) proportion which gave the highest strength was further investigated for various water-cement ratios. It was concluded that for a mix of 1:8, 10% replacement of OPC by SDA-lime gave the maximum strength at water-cement ratio of 0.55 and was recommended for the production of sandcrete hollow blocks. The blocks should be used for low-income housing and non-load bearing walls

Suitability of Broken Bottles as Fine Aggregate for Production of Concrete

The use of broken bottles as partial replacement of river sand for production of concrete was investigated. The grading of the broken bottles and sand fell in zone II. The specific gravity of the bottles was 2.55 and that of sand was 2.65. Sand was replaced with the broken bottles in the proportions of 0%, 10%, 20%, 30%, 40%, and 50% by weight. The mix of 1:2:4 by weight and watercement ratio of 0.45 were used. Cubes of side 150mm were cast for each proportion, cured by complete immersion in water and tested for density and strength at the ages of 7, 14 and 28 days. The average compressive strength of the cubes was found to increase with curing age but decrease with increase in the proportion of broken bottles in the mix. The proportion of broken bottles to give a minimum strength of 20N/mm2 was 30% at 7 and 14 days, and 40% at 28days. The maximum mean compressive strength of 19.0N/mm2 was obtained at 28days when sand and broken bottles were used in equal proportions. Density did not appear to have a discernible trend. For structural concrete, the proportion of broken bottles should be limited to 30% for early strength concrete and 40% when early strength is not required. For non-structural concrete, proportion greater than 40% can be used

Suitability of groundnut shell ash/lime mixture in production of concrete

The suitability of groundnut shell ash (GSA) mixed with 45% slaked lime was investigated. The aim was to determine the percentage GSA/lime and water-cement ratio that would give the 28 – day minimum strength of 20N/mm2. Groundnut shells were burnt and the ash sieved using 150 micrometer sieve. The ash mixed with 45% slaked lime was used to partially replace ordinary Portland cement (OPC) in various proportions. The design mix used was 1:2:4 and water – cement ratios of 0.45, 0.55 and 0.65 by weight. Nine cubes of side 150mm were cast for each proportion and water – cement ratio. The cubes were cured by complete immersion in water at room temperature. Three cubes were tested for density and strength at each of the ages of 7, 14 and 28 days for each proportion of OPC/GSA – lime. It was concluded that for a mix of 1:2:4, the proportion of GSA/lime up to 20% gave the 28-day minimum strength of 20N/mm2 at water-cement ratio of 0.65 and was recommended for use as structural concrete.Keywords: Groundnut shell ash, Cement, Concrete, Water-cement ratio, StrengthNigerian Journal of Technological Research, vol 7(1) 201