The HRWRA helps in achieving excellent flow at low water contents and VMA reduces bleeding and improves the stability of the concrete mixture.An effective VMA can also bring down the powder requirement and still give the required stability.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 could overcome the problems of defective workmanship.
Materials for SCC Mixture proportions for SCC differ from those of ordinary concrete, in that the former has more powder content and less coarse aggregate.
Moreover, SCC incorporates high range water reducers (HRWR, superplasticisers) in larger amounts and frequently a viscosity modifying agent (VMA) in small doses.
In fact, river sand is simply not available in many areas.
Although there are studies that have shown that quarry run could be used as a filler instead of limestone for SCC, where X, Y, and Z are dimensions of the aggregate) to indicate the likely degree of potential compaction; values of index between 60 and 10 are cubic, between 30 and 60 indicate flakiness (100 for perfect cube), while values below 30 suggest elongation - Sphericity index to describe the polyhedral shape of the particle, and - Roundness index to describe the degree of angularity; values between 84 and 100 are angular, and between 52 and 68 are rounded Admixtures SCC invariably incorporates chemical admixtures - in particular, a high range water reducing admixture (HRWRA) and sometimes, viscosity-modifying agent (VMA).
It is possible that the highly flowable nature of SCC could allow a higher proportion of flaky aggregates compared to normal concrete. O’Flannery and O’Mahony have devised a method for shape characterisation of coarse aggregate, which could assist in designing SCC mixtures having marginally unsuitable aggregates.
The purpose of the study was to determine dimensional parameters for ‘fingerprinting’ any given coarse aggregate sample.
Research studies in Japan are also promoting new types of applications with SCC, such as in lattice type structures, casting without pump, and tunnel linings.
Since the development of SCC in Japan, many organizations across the world have carried out research on properties of SCC.
In Japan, the volume of SCC in construction has risen steadily over the years.