02-10-2012, 04:53 PM
EFFECT OF SIZE OF AGGREGATE ON MECHANICAL PROPERTIES OF
SELF COMPACTING CONCRETE
EFFECT OF SIZE OF AGGREGATE.pdf (Size: 123.62 KB / Downloads: 87)
ABSTRACT
Self-Compacting Concrete (S.C.C) is a concept in which the ingredients of the
concrete mix are proportioned with addition of suitable chemical and mineral admixtures
so that the concrete flows without segregation and compacts by its own weight without
any external or internal vibration. To achieve the warranted workability and compressive
strengths, compositions were designed to obtain a SCC of 30 MPa strength based on
Nan- Su method of mix design and following Okamura’s and EFNARC guidelines using
mineral admixtures like fly ash. An experimental programme has been carried out on
SCC mixes with different sizes of aggregate ranging from 20 mm to 8 mm to study the
effect of size of aggregate on mechanical properties of SCC. Reasonable improvement
in the compressive strengths was observed when SCC was developed with 12.5 mm size
aggregate.
INTRODUCTION
Self-Compacting Concrete (S.C.C.) has been described as “the most revolutionary
development in concrete technology ”. S.C.C is a concept in which the ingredients of the
concrete mix are proportioned with addition of suitable chemical and mineral admixtures
so that the concrete flows without segregation and compacts by its own weight without
any external or internal vibrators. When the construction industry in Japan experienced a
decline in the availability of skilled labour in the 1980s a need was felt for a concrete that
would overcome the problems of defective workmanship like compaction which effects
durability of concrete. This led to the development of S.C.C The concept was proposed
by Professor Hajime Okamura of Kochi university of Technology, Japan in 1986 as a
solution to the growing durability concerns of Japanese Government and later developed
by Professor Ozawa at the university of Tokyo. Since then S.C.C. has generated
tremendous interest among the research scholars, engineers and concrete technologists.
MIXING OF INGREDIENTS
Cement , fine aggregate and fines were mixed and then coarse aggregate was
added and mixed. Thoroughly Then 75 % of water was added and mixed together Then
25 % of water with Super plasticizer was added , mixed together for 5minutes. Different
trail proportions were mixed in the laboratory and the optimum percentage of super
plasticizer for the mix for each size of coarse aggregate was determined. Thus SCC was
produced in the laboratory for each size of coarse aggregate 20mm,16mm, 12.5mm,10
mm and 8mm with optimum dosage of super plasticizer and fly ash without any
segregation
TESTING OF SCC IN FRESH STATE
To be called as SCC the fresh concrete must have the following characteristics
Adequate fluidity, High resistance to segregation, Appropriate plastic viscosity and
sufficient deformability. These characteristics are fully described by the following
properties.