Prompted by the high cost of building materials as well as the amount of dead load weight generated by block wall on beams and columns in partitioning works most especially in high rise buildings, this project work on the use of sawdust as admixture in production of hollow sandcrete blocks was carried out in order to investigate a possible solution to the problems. The research work understudies the weight vis-a-vis cost of production of available commercial sandcrete blocks in Lagos metropolis. It has been observed that prices of construction blocks were typically above the reach of many Nigerians. Production of sandcrete blocks were made by partial replacement of sand with a varying proportion (10%, 20%, 30% and 40%) of sawdust. The strength of each block was determined to ascertain conformity with the minimum acceptable standards. Equally, the weights were checked and compared with blocks devoid of sawdust. The tests were carried out on the 7, 14, 21 and 28 days after production. From data gathered, recommendations were given which will be beneficial to the construction industry and general populace in respect of low cost and light weight sandcrete blocks. It is concluded that if the recommendations herein should be followed, problems of cost and weight in building construction shall be reduced.
Sustainability in the construction industry is a global concern, and one way of handling this is the idea of recycling old concrete rubbles in the production of fresh concrete. Recycled aggregate concrete is normally classified as light weight concrete and recommended for use in production of low-grade non-structural elements. This study examined the properties of crushed old concrete cubes as replacement for natural aggregate. Five specimens 150x150mm concrete cubes with varying percentages of coarse recycled aggregate of 0 %( control), 25, 50, 75 and 100% were prepared. All the mixes were proportioned using the absolute volume method with a targeted compressive strength of 30N/mm2 and varying w/c ratio. The result shows that with up to 75% replacement of natural aggregate with recycled aggregate, the 28 days compressive strength of concrete is in close proximity with that of normal concrete. While the strength of exclusive recycled aggregate concrete is about 15% lesser than that of exclusive natural aggregate. The result of this research confirms that crushed old concrete cubes can be safely used in the production of high grade concrete.
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