Effects of concrete grades on strength characteristics of reinforced concrete slender beams

L.M Olanitori,I.A Gbadamosi

doi:10.4314/jasem.v23i5.12

Abstract

This paper presents the results of experimental study on the effects of concrete grades on strength characteristics of reinforced concrete slender beams. The materials used for the concrete were sand, crushed granite, stone dust, cement and water. Concrete mix ratios of 1:2:4 and 1:3:6 by weight with water-cement ratio of 0.6 was used. Four (4) reinforced concrete slender beams were cast, which were loaded with a point load at the beam centre. The results of the work show that, with decrease in concrete grade, there was corresponding decrease in ultimate load and shear capacity. For a drop of 16.67%, 38.67% and 62% in concrete grade there were corresponding decrease in the strength characteristics of beams by about 10.5%, 21.79% and 32.75% respectively. Therefore, decrease in concrete grade does not have the same percentage decrease in the strength characteristics of beams. Also, the mode of failure of reinforced concrete beams, depends not only on the ratio of the span to height of beam and the percentage area of reinforcement provided, but also on the concrete grade.Keywords: Concrete grades, slender beam, compressive strength, ultimate load, shear capacity

Highlights

Concrete is one of the major construction material being used worldwide
Tests by Zhou et al (1995) show that compressive strength increases with an increase in coarse aggregate size
Olanitori and Afolayan (2014) noted that, most reinforced concrete structures failed by shearing, and this is because there exist discrepancies between estimated shear capacity based on equations from the codes and, the actual shear capacity and concluded that more research work should be conducted on models that can predict the shear capacity of reinforced concrete beams more accurately

Summary

Introduction

Concrete is one of the major construction material being used worldwide. Its great advantage is that as a man-made material, it can be poured into moulds of any shape where it sets, removing the necessity to form the material by carving, as is the case with stone. The quality of concrete produced depends on the quality of its constituent materials and their mix ratios; the higher the percentage of clay/silt content of sand, the lower the characteristic strength (Olanitori and Olotuah , 2005). Ezeldin and Aitcin (1991) compared concretes with the same mix proportions containing four different coarse aggregate types They concluded that, in highstrength concretes, higher strength coarse aggregates typically yield higher compressive strengths, while in normal-strength concretes, coarse aggregate strength has little effect on compressive strength. Olanitori and Olotuah (2005), noted in their study, that targeted concrete strength may not be achieved due to the silt/clay content in the fine aggregate. The flexural tests carried out on the beams were in accordance with BS EN 12390-5 (2009)

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Methods

Conclusion