Evaluation of lateritic coarse aggregates as a partial replacement for granite coarse aggregates in structural concrete.
Loading...
Date
2023
Authors
Musonda, Musunga
Journal Title
Journal ISSN
Volume Title
Publisher
The University of Zambia
Abstract
In Zambia, coarse aggregates for concreting are normally produced by crushing granite, limestone and basalt among other rock types. However, these rocks are scarce diminishing natural resources and henceforth; the need to study other naturally available materials for full or partial replacement; with the intention of reducing the cost of concrete. The main aim of this research was to evaluate concrete produced by partially replacing Granite Coarse Aggregate (GCA) with Lateritic Coarse Aggregates (LCA). The properties of LCA concrete evaluated included; but were not limited to the fresh and hardened state properties of LCA concrete, some durability properties of the concrete such as Sorptivity, water accessible porosity and residual strength after exposure to high temperature. Mineral composition of Lateritic Coarse Aggregates was analyzed using X-Ray Diffraction (XRD). The results showed that crushed lateritic aggregates were composed of 43.7% Crystalline iron oxide (FeO (OH)) (Goethite), 38% Kaolinite i.e. Clay mineral (Al2O3 2SiO2·2H2O), 18.3% Quartz (SiO2) and abundant amorphous (non-crystalline) iron oxide minerals such as Ferrihydrite (Fe2O3•H2O). A trial mix for 30MPa concrete was done in the laboratory, using granite coarse aggregates, river sand, 42.5R Portland Cement and portable water. Thereafter, alternative mixes were done by replacing GCA with LCA in the proportions, 90:10, 80:10, 70:30, 60:40, 50:50, and 0:100, by mass. The study results showed a trend of reducing crushing and split tensile strengths with increase in the LCA amount in the concrete mix. Mathematical relationships obtained from this study showed that replacing 19.2% of LCA for GCA in a 30 MPa concrete mix can achieve a concrete with a characteristic strength of 25 MPa at 28 days, while a 27% replacement of LCA for GCA would achieve a compressive strength of 25 MPa at 50 days. This range of replacement was found to produce normal weight concrete. The study also showed that concrete with less than 30% of GCA replaced with LCA had higher, but acceptable sorptivity and water absorption rate than plain concrete. Further, LCA concrete replaced with up to 30% of GCA at 28 days showed identical mass and crushing strength loss to that of plain concrete; upon the specimens being exposed to elevated temperature.
Keywords: Workability, Water absorption, Granite coarse aggregate, Lateritic coarse aggregate, Structural concrete
Description
Masters of Engineering in Structural
Keywords
Granite coarse aggregate. , Building materials. , Buildings--Design and construction. , Construction industry--Management. , Engineering, Architectural. , Sustainable architecture.