Onundi^1,, Lateef O. Alkali¹, Abba M. Oumarou², M. Ben Ahamadu Audu¹

The qualities of construction materials and the influence of insurgency on the availability of local coarse aggregates for production of concrete in Maiduguri were assessed in this study. Ten block production industries were selected from major wards in Maiduguri metropolis, while the brands of cement sold in Maiduguri including Dangote 3X (i.e. Obajana) and Ashaka, of grades 42.5N and 32.5N respectively were selected with two different sizes of blocks. Four sizes of reinforcement bars; 10 mm, 12 mm, 16 mm and 20 mm; were randomly selected. Local aggregates and water were used during the investigations. Microsoft Excel was used to analyse and interpret the data. The results show that, the dry compressive strength of the sandcrete blocks samples for the 150 mm blocks were 0.016 to 0.999 N/mm² which is less than between 0.03 to 98.44 % of the recommended minimum of 1.0N/mm² at age 7 days; similarly, the average compressive strength of the sampled 225 mm blocks were also 0.253 to 0.634 N/mm² which is less than between 57.73 to 83.14 % of the recommended minimum of 1.5N/mm² at the age of 7 days. The highest value of 0.634 N/mm² was less than the recommended value of 1.5N/mm² for load bearing walls. The diameters of all the steel reinforcements were 1.42 to 3.09% less than the specifications; characteristic strengths of 10 mm steel reinforcement proved to be 506.7N/mm² which is greater than 460N/mm² the recommended value. A factor of safety of 1.115 was recommended instead of 1.15. The insurgency in the north eastern part has negatively impacted the quality and availability of construction material as well as the local coarse aggregates in the building industry.

Bama Gravel, construction materials, compressive strength, insurgency, Portland cement, yield stress