The Thermal Conductivity and Cold Crushing Strength Of Locally Produced Sandcrete Bricks of Different Compositions of Sawdust, Palm-Nut Fibre And Pozzolana Incorporated- A Search for Room Comfort in the Tropics

The quality housing enhances the health and welfare of man and contributes immensely to his productivity, thus underscoring its importance as a fundamental need. Sandcrete blocks are widely used in Ghana as a walling unit. This research determined the effect of sawdust, palm-nut fibre, hydrated lime and pozzolana on the thermal conductivity and the cold crushing strength (CCS) of a locally produced sawdust-palm-nut fibre-pozzolana incorporated bricks, in search for room comfort. The controlled sandcrete blocks were mixed in the ratio 6:1 and 3:1 and mix for cement replacement was also prepared. Both batches of the sandcrete samples were air cured for a period of 28 days, and tested for their cold crushing strength (CCS) and thermal conductivity. Sawdust and palm-nut fibre cubic samples were prepared using varied composition of sawdust and palm-nut fibre. The mix was poured into a 100 mm cubic mould to form cubic samples. One batch of the samples was air cured, the second batch was cured by sprinkling of water and the third batch by total immersion of samples in water for a period of 28 days. Cold crushing strength and thermal conductivity tests were carried out at the end of the 28th day period. It was found that the controlled sandcrete samples for sand-to-cement ratio of 6:1 and 3:1 and air cured for 28 days, the strength values were (6.01 ± 0.46) MPa and (6.63 ± 0.46) MPa, respectively. Again, thermal conductivity of (11.53 ± 0.15) × 10-2 Wm-1 oC-1 and (12.36 ± 0.07) × 10-2 Wm-1 oC-1 respectively were recorded. Those cured by sprinkling of water had the strength of (6.07 ± 0.09) MPa and (9.92 ± 0.55) MPa for sand-to-cement ratio of 6:1 and 3:1 respectively. Cement replacement of 40%wt gave strength of (5.65 ±0.04) MPa and (5.98 ± 0.27) MPa for samples air cured and that cured by sprinkling of water for 28 days respectively. The new local sawdust samples with composition of 9%wt gave the strength of (2.67 ± 1.12) MPa and thermal conductivity of (7.59 ± 0.09) × 10-2 Wm-1 oC-1 and could be considered for internal partitioning. Palm-nut fibre samples with composition 2.0 %wt gave the strength of (7.45 ± 0.18) MPa and thermal conductivity of (7.08 ± 0.11) × 10-2 Wm-1oC-1, and this was recommended for main structural work. Sawdust-palm-nut fibre samples with composition of 1.5 %wt sawdust and 1.5 %wt palm-nut fibre gave the strength of (3.91 ± 0.07) MPa and thermal conductivity (7.06 ± 1.08) × 10-2 Wm-1 oC-1 and could be considered for non-load bearing structural work in a non water-logged area. It was also found that the mix ratio, the nature of the constituent materials, porosity and binder to water ratio affected the quality of the new locally produced bricks. This research indicated that, generally, the addition of palm-nut fibre improved the strength of the local bricks, besides giving good thermal comfort, but sawdust weakens the bricks. However, it is recommended that the sawdust and the palm-nut fibre be treated to enhance bonding thereby improving strength. The local sawdust bricks, palm-nut fibre bricks and sawdust-palm-nut fibre bricks had low thermal conductivity and therefore predicted good thermal comfort. However, there is room for improvement, but palm-nut fibre bricks gave higher strength and lower thermal conductivity than the controlled sandcrete block and the sandcrete block sold on the open market.

Source: KNUST