AN OPTIMUM EVALUATION OF FOUR DIFFERENT NIGERIAN PORTLAND CEMENTS FOR HIGHWAY RIGID PAVEMENTS.

This study investigated the trend of four different types of new brands of cement that are produced locally in Nigeria for optimum selection while producing concrete for highway pavement. The four brands of portland cements used individually in the course of producing the investigated concretes are tagged 42.5 Rd, 32.5 Rs, 42.5 Np and 32.5 Rt. It involved using nominal maximum size of 19 mm granite as coarse aggregate in the individual concrete production. Coarser river sand with fineness modulus of 3.0 along was used with water cement ratio of 0.4 to produce the said individual cement concrete of ratio 1:1.5:3 mixtures. The four different types of cement were individually subjected to tests that included specific gravity, fineness, consistency, setting time, chemical and metallic compositions. The coarse aggregate used was subjected to crushing, impact and abrasion tests. Aggregate gradation tests were also carried out on both fine and coarse aggregates. Each brand of fresh concrete produced based upon the cement type was subjected to slump and compaction factor tests. Compressive, tensile splitting and flexural strength tests were carried out on hardened concrete specimens. At 28 days curing, the use of 19 mm maximum size of aggregate proffered concrete flexural strength ranging from 3.6 N/mm? to 4.8 N/mm? Significantly, it is the use of 42.5 Np cement only that satisfied the minimum requirement value for flexural strength of 4.5 N/mm? at 28 days curing for highway pavement design and construction. The justification for this study is the identification of the uniqueness of the 42.5 Np cement having a breakthrough among the peering cements for being singularly satisfying standard specification requirements in this facets.