International Journal of Engineering and Applied Sciences (IJEAS) ISSN: 2394-3661, Volume-5, Issue-7, July 2018 21 www.ijeas.org Abstract— Using granite 12.5 mm nominal maximum size aggregate in the production of concrete is increasing in Nigeria. For this reason, its optimization in use for satisfactory and adequacy in relationship to strength and durability for highway rigid pavement construction in Nigeria is a concern. In this study, granite of 12.5 mm nominal maximum size aggregate gradation as concrete constituent has been used for four different types of 1:2:3 mixtures along with Portland cement and river sand. Of the four different types of concrete production carried out, Type B0 is of a normal concrete using 0.4 water cement ratio (w/c) with no addition of superplasticizer to the concrete produced. Others are superplasticized concretes Types B1, B2 and B3 that were individually produced with addition of varied 1.0%, 1.25% and 1.5% of superplasticizer to cement weight using 0.3 water cementitious materials ratio (w/cm). A total number of 180 concrete specimens were produced in this study. 60 specimens were 550 mm x 150 mm x150 mm beams; another 60 specimens were 150 mm x 150 mm x 150 mm cubes while additional 60 specimens were 150 mm diameter with 300 mm of length cylinders. Tests were duly carried out upon hardened specimens moist cured for 7, 28, 56, 90 and 120 days for flexural, compressive and tensile strengths accordingly. The results of cement used gave relative density value as 3.15, bulk density as 1160 kg/m³ with its fineness being 5% retained on 45 μm sieve. River sand used is of well-graded fine aggregate while granite employed is of uniformly graded coarse aggregate. Concrete mix design flexural strength of 5.3 N/mm² at 1.25% superplasticizer dosage achieved and satisfied standard specification requirements for highway rigid pavement whereas 4.9 N/mm² was achieved by normal concrete which could not satisfy same and uneconomical. Index Terms— Experimental, Superplasticizer, Concrete, Pavement I. INTRODUCTION Coarse aggregate nominal maximum size for concrete production varies from 4.75 mm to 90 mm according to ASTM D448 of which the commonly used of same varied from 9.5 mm to 25 mm. Using granite material of 12.5 mm nominal maximum size aggregate in the production of concrete is increasing in Nigeria. For this reason, there is need to give concern and attention towards optimizing 12.5 mm nominal maximum size aggregate for concrete production. Hence, this will pave way for providing satisfactory concrete with strength and durable properties that could be used for highway pavement construction in Nigeria. Concrete mineral constituent that predominantly retained on the 4.75 mm sieve or the portion that retained on same is called coarse aggregate ASTM C125 (2015). According to Buertey et al., (2015) Isaac Akiije, Department of Civil and Environmental Engineering University of Lagos, Akoka-Yaba Lagos, Nigeria coarse aggregate generally takes approximately 60-75% of the total volume of the structural concrete while coarse and fine aggregates typically make up to 70% to 90% of same. Concrete mineral constituent that passed the 9.5 mm sieve and almost entirely passing the 4.76 mm sieve and predominantly retained on the 74-micron sieve is called fine aggregate. Bhattacharjee et al., (2016) claimed that aggregates were earlier considered as chemically inert materials but now it has been recognized that some of the aggregates are chemically active and also that certain aggregates exhibit chemical bond at the interface of aggregate and paste. Oduroh et al., (2000) considered the effect of the gradation on the strain-rate tensile behaviour of the concrete upon the maximum size of the aggregate particles at high strains. They concluded that as the surface area increases with the decrease in the maximum size of the aggregates whilst resulting to voids decrease and increase in concrete bond strength. Normal Portland cement specified as Type I by ASTM C150 (2015) has its application for general concrete work whilst its most suitability in use includes floors, reinforced concrete structures and pavements construction. Normal concrete is usually limited to 0.42 water cement ratio by weight for non-air-entrained concrete or 0.39 water cement ratio by weight for air-entrained concrete ACI 211.1 (2009). Superplasticizer, or high-range water reducer, can either greatly increase the flow of the fresh concrete or reduce the amount of water required for a given consistency. Mamlouk (2006) and Akiije (2017) claimed that superplasticizers can be used in the production of concrete for a low water-cementitious materials ratio with the benefits of higher workability of fresh concrete, higher strength of hardened concrete, reduced porosity with very low permeability. The aim of this study is about the characterization and effects of a 12.5 mm nominal maximum size aggregate used in normal and superplasticized concretes for highway rigid pavement. Specifically, the main objectives are to: 1. Determine properties of constituents that are readily available to produce satisfactory strength and durable normal and superplasticized concretes. 2. Define concrete mix designs for the purpose of selecting the most economical proportions for a required minimum standard quality. 3. Assess the workability of the fresh concretes produced through laboratory slump and compacting factor tests. 4. Determine the moist cured hardened concretes specimens’ strengths properties through the appropriately compressive, flexural and tensile splitting tests. The scope of work in this study is on proportioning concrete constituents which are cement, fine and coarse aggregates of mix 1:2:3 respectively using water cementitious Characterization and Effects of a 12.5 mm Nominal Maximum Size Aggregate in Concrete Strengths Optimization Isaac Akiije