30-05-2012, 05:25 PM
fiber reinforced concrete (FRC)
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ABSTRACT
In modern day construction practice, repair and rehabilitation of structures has taken a prominent role. Mortar plays a vital part in these works. As such, the flowability of mortar can be an added advantage when inaccessibility comes into picture like in case of congested reinforcement or narrow cracks or fissures. Due to the application easiness and mechanical advantages, Self Compacting Mortar is preferred for repair purposes especially in reinforced concrete structures these days. The cement as well as the ingredients of the paste, mineral admixtures (pozzolanic or inert nature) and plasticizing chemical admixtures should be carefully chosen in order to obtain a suitable paste composition to enrich the granular composition of the mix. There is no universally accepted agreement on the effect of these factors due to the complexity of combined action; thus, it is hard to make a generalization.
INTRODUCTION
By adjusting the aggregate content and using a combination of chemical and mineral admixtures, self-compacting concrete mixes behave in a manner not normally observed in standard concrete. These admixtures, typically consisting of high-range water-reducing (HRWR, or superplasticizing) and viscosity-modifying admixtures, meet the requirements of ASTM C494. Filler materials are often used for replacing some of the aggregates and modifying the viscosity. High doses of HRWR produce a mix with high fluidity and allow for a reduced water-powder ratio. Without a viscosity-modifying admixture, the mixture would tend to segregate. However, the viscosity-modifying admixture enhances the viscosity of the mixture, which reduces aggregate segregation, settlement, and bleeding. The resulting mix, when properly designed, is considered to be self-compacting or self-placing concrete.
EXPERIMENTAL WORK
GENERAL:
The sole purpose of the experimental study is to determine the workability and segregation indices of fibre reinforced self compacting concrete with varying fiber contents. The experimental work consists of preparing the concrete mix with all ingredients and testing for workability of concrete by using flow test and compaction factor test.
Mix Design for FRSCC:
Using the equation as proposed by Su-Hsu and Chai(2), several trial mixes were made in order to reach the suitable mix proportion so as to satisfy the criteria for making successful SCC.
(a) Slump flow test:
This test is used to determine the filling ability and can indicate segregation resistance of self-compacting concrete to an experienced user. In this type of test, the fresh concrete is poured into a mould in the shape of a frustum of a cone. When the cone is withdrawn or lifted upward gradually, the distance the concrete has spread provides a measurement of the consistency of the concrete. Figure 2.1 shows the spreading of concrete after lifting the cone.