QUALITY OF SANDCRETE HOLLOW BLOCKS IN NIGERIA

QUALITY OF SANDCRETE HOLLOW BLOCKS IN NIGERIA

ABSTRACT

Sandcrete hollow blocks are widely used in Plateau State, Nigeria. The quality of these blocks produced, however, differs from each manufacturer due to different methods employed in the production and the properties of the constituent materials. This research work focuses on the impact of quality control practices by manufacturers on the quality of blocks produced in the state. General survey of the entire state was conducted to determine the number of block industries in the state and 121 block manufacturing industries were observed. Five (5) block industries were selected randomly for the studies. 300 Sandcrete blocks of average sizes of 450 x 230 x 230mm were purchased from the manufacturers and tested for dry and wet development compressive strength; and wet compressive strength after 28 days, the density, water absorption, dry shrinkage, wetting expansion and dimension tolerance of the blocks were also determined.Sand (fine aggregates) material samples were also taken from the manufacturers and tested for grading, silt and clay contents. Cement samples used for the manufacturing of these blocks were collected and tested for setting times, standard consistency and soundness. The mix ratio and method of curing were also considered. The research work confirmed that, the highest dry and wet development compressive strength values were found to be 0.75N/mm2 and0.62N/mm2 respectively. The highest wet compressive strength was found to be 0.86N/mm2 . The sand materials fell within zone 1 and 2 of the British standard sieve, and the silt and clay contents were found to be less than 6% as specified by BS EN 1377-2:1990, which are adequate for good mix.The cement consistency was found to be 30.5% which is within the BS EN 196-6:2010 requirement, the initial setting time was found to be 48minutes and the final setting time was found to be 2hours 47minutes, which is within the recommendations of BS EN 196-:2008. The soundness was found to be 1.2mm, which is within the recommendations of 12mm specified by BS EN 196-3:2008. The blocks produced are therefore less than the local and international standard requirements and therefore, unsuitable for use as a load bearing wall.

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