FLEXURE AND CRACKING BEHAVIOR OF RC BEAMS BY PARTIAL REPLACEMENT OF CEMENT WITH GGBS

Abstract

Ordinary Portland cement (OPC) is one the main materials used in casting reinforced concrete (RC)
structures. However, it causes the emission of a significant amount of CO2 to the atmosphere and therefore
contributes widely to the formation of the greenhouse effect. The increasing use of such OPC materials in
construction projects had led to the initiation of global environmental warming. The utilization of industrial byproduct in construction sector could become an important route for large-scale safe disposal of the industrial wastes
and reduction of construction cost. Ground Granulated blast furnace slag (GGBS) is a by-product of the steel industry
which can be partially replaced with cement to reduce significantly many of the environmental burdens associated
with concrete. Polypropylene fibers tend to hold the concrete mix together. This slows the settlement of coarse
aggregate and thus reduces the rate of bleeding. This paper presents, the flexure and cracking behavior of RC beams
by partial replacement of cement with GGBS of 0%, 50% and 70%. Addition of polypropylene fibers decreases the unit
weight of concrete and increases its strength. 0.5% of polypropylene is added to cement. Experimental investigation
included testing of six reinforced concrete beams with and without GGBS. Portland cement is replaced with 50% and
70% GGBS. In this paper, the results of laboratory investigation conducted on the structural behavior of reinforced
concrete beam with various replacement levels of GGBS are presented. In addition, the concrete compressive and
tensile strength of the different mixes were evaluated at 7, 28 and 56 days. All the beam specimen were tested on the
two point loading. Data presented include the load-deflection characteristics, cracking behavior of the reinforced
concrete beams with and without GGBS when tested at 28 and 56 days. The investigation revealed that the
compressive and split tensile strength decreases by increasing of GGBS percentage, but increases with age. The
ultimate loading capacity of the beam specimens with 50% and 70% GGBS replacement are higher than that of the
without GGBS specimen by 2% and 3% respectively.