ABSTRACT
In hot weather retarding admixture are added to prolong the chemical process of hydration so that concrete remain plastic and workable for longer period of time which will gives room to high volume placements. The goal of the research is to investigate the effect of cereal flours made from maize and sorghum on the properties of concrete; this is with a view to establishing the efficacy of the selected cereals as retarder in concrete. The objectives of this research are to; determine the physical and chemical properties of cereal flour made from sorghum and maize flour, establish appropriate dosages of admixture (cereal flour) required for concrete mixes in terms of compression and tension strength, assess the effects of the cereals flour on the fresh properties of concrete, assess the effects of the cereals flour on the hardened properties of concrete. The mix used for the research was calculated using the BRE method and the water cement ratio of 0.6 was used. The mix ratio of 1:1.13:3.40 was used. Trial test was conducted with maize, sorghum, wheat and millet. The cereal was ground, sieved and added in various percentages by weight to the cement, mix and cast in a cube of 100 by 100 by100mmmould left in the mould for 24 hours then demould and immersed in water for seven days. After seven days it was tested for compressive strength, the sorghum and maizegave the highest and higher values of compressive strength respectively and therefore used for the main work. The same procedure was used for the main workthe samples used were produced in three different batches. The first sets of batches were the control samples which also served as source of comparison. The second and the third batches had various percentages of maize and sorghum flour added respectively. The curing was done by complete immersion for 1, 3, 7, 28 and 56 days for all the samples. The compressive strength and tensile strength increase from 1% to 3% dosage of the cereal flour added by weight of the cement. The compressive strength and tensile strength increase as the age of curing increases. Sorghum flour had higher values of compression and tension strength than maize flour. The result of the water absorption test of hardened concrete for maize flour showed that at 28 days 4% and 5% dosage of maize flour added by weight of cement conform to water absorption test for hardened concrete. 1% to 3% dosage of the maize flour do not conform to water absorption test for hardened concrete, at 56 days 1% and 2% of maize flour dosage do not conform to water absorption test while 3% to 5% dosage of maize flour conform to water absorption test. For sorghum flour at 28 days 1% and 2% dosage do not conform to water absorption test for hardened concrete, 3% to 5% dosage conform to water absorption for hardened concrete. At 56 days all the specimens conform to water absorption test for hardened concrete. For the results of the abrasion resistance it was observed that the abrasion resistance decreases with increase in curing period. It was also observed that the maize flour has higher abrasion resistance than sorghum flour. The optimum compressive and tensile strength of the test specimen is achieved at 3% dosage of maize and sorghum flour added to the cement. Maize and sorghum flour delay the setting time of cement, for sorghum flour added to cement the setting time is achieved at 410 minutes while for maize is 248 minutes. Maize flour and sorghum flour are good retarding admixtures as they delay the setting time of cement.