Comparison between BRE and USBR Methods of Concrete Mix Design using SDA as partial replacement for Fine Aggregate

Abstract

The fundamental objective of this research was to empirically analyse and compare between the Building Research Establishment (BRE) and the United States Bureau of Reclamations (USBR) methods of concrete mix designs using uncrushed coarse aggregate at various target strength which evokes three different mix ratios 1:2.05:2.95/0.54, 1:2.23:3.21/0.58 and 1:2.41:3.47/0.62 for the BRE method ; 1:2.41:3.36/0.59, 1:2.37:3.29/0.38 and 1:2.28:3.17/0.56 for the USBR method  and to determine how the different design methods affect overall results as to tests on the freshly prepared concrete to measure the degree of workability of concrete which involves the slump and compaction factor tests. Experiments were performed to examine the physical properties of the constituents of concrete such as the sieve analysis test to determine the grading of the aggregates (fine and granite) which was deduced from the particle size distribution (PSD) curve; specific gravity tests on the materials; density, bulk density and unit weight tests. The hardened concrete at 7 days and 28days of curing were equally experimented to determine the mechanical properties of the concrete. The compressive test was executed on 150mmx150mmx150mm   cubes for the various mix ratios to measure the compressive strength of the concrete moulds at the 7 and 28days ages of curing through direct crushing. The split-tensile test was carried out on cylindrical moulds of dimension ø150mmx300mm to determine the tensile strength of the hardened concrete at the respective ages. The flexural tests were experimented on 150mmx150mmx150mm concrete beams to evaluate the flexural strength of the concrete at both curing ages using a center point approach. The averages of these data were used for the analysis of the derived results. The fine aggregate was partially replaced with Saw dust Ash (SDA) at various percentages of replacement. Compressive, Split-tensile and flexural strength tests at these variable percentages of partial replacement of fine aggregate at 0%, 5%, 10%, 15%, and 20% with Saw dust Ash (SDA) was done to examine the effect on these mechanical properties. This study was geared to determine the optimum percentage of partial replacement of fine aggregate by the Saw dust Ash (SDA). After analyzing the obtained data emanating from the various mechanical experiments, the average optimum percentage of sand replacement by SDA was found to be 5% for effectiveness. In presenting these results and from the designs, it was glaring to elucidate the similarities and differences between the BRE and USBR design methods. In tandem to the established data, relevant conclusion and recommendations were efficiently implemented as to the 5% partial replacement of sand with Saw dust Ash (SDA) for efficiency and economy.