Characterization and Effects of a 12.5 mm Nominal Maximum Size Aggregate in Concrete Strengths Optimization

Isaac Akiije

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.

https://dx.doi.org/10.31873/IJEAS.5.7.06