CURING ON THE STRENGTH OF SANDCRETE BLOCKS

One of the basic needs of man is housing. Over 90% of physical infrastructure in Nigeria are being constructed using sandcrete blocks making it a very important material in building construction. it is widely used in Nigeria, Ghana, and other African countries as load bearing and non-bearing walling units. For a long time in Nigeria, sandcrete blocks are manufactured in many parts of the country without any effort to satisfy local building requirements or good quality work. In the year 2000, and in an attempt to enhance the use of the best materials and manufacturing practice, the Standard Organization of Nigeria developed a reference document which prescribed the minimum requirements and uses of different kinds of sandcrete blocks. This study put into consideration the effects of curing on the compressive strength property of 150mm thick sandcrete blocks produced by commercial block industries in Benin metropolis of Nigeria. Commercial sandcrete blocks were randomly selected from three (3) block moulding sites, the curing practices and the mix ratio of the blocks gotten from the various sites were taken into account and was left for 28 days after wish the compressive test was done on them. The mix ratio gotten from the sites were 1:12, 1:14 and 1:16. Also, in the structural Laboratory of the University of Benin, sandcrete blocks were moulded with the same mix ratio from the various sites as control and also to the standard 1:6 mix ratios and was cured for 28 days by watering every morning and evening up to the testing dates. The 28day compressive test results were compared with those cured in the sites. The results gotten from site range from 0.303N/mm2 to 0.763N/mm2 , while those cured in the University Laboratory range from 0.425N/mm2 to 0.875 N/mm2 . These results indicate the 28-day compressive strengths of blocks. the compressive strengths of all the blocks made from site and labouratory for mix ratios of 1:12, 1:14 and 1:16 were below the minimum requirements xi of 2.8N/mm2 by the British Standard BS 6073, although the block from the labouratory gave a higher value of compressive strength to that of the site for each corresponding mix ratio. The value gotten from the standard mix ratio (1:6) was 3.058N/mm2 which was more than the minimum specification for sandcrete blocks. This study concludes that improper curing method and mix ratios are responsible for the poor quality of commercial sandcrete block made in Benin metropolis.