Self-compacting concrete (SCC) is a flowing concrete mixture that is able to consolidate under its own weight. The highly fluid nature of SCC makes it suitable for placing in difficult conditions and in sections with congested reinforcement. Use of SCC can also help minimize hearing-related damages on the worksite that are induced by vibration of concrete. Another advantage of SCC is that the time required to place large sections is considerably reduced.
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. This led to the development of self-compacting concrete, primarily through the work by Okamura1. A committee was formed to study the properties of self-compacting concrete, including a fundamental investigation on workability of concrete, which was carried out by Ozawa et al2. at the University of Tokyo. The first usable version of self-compacting concrete was completed in 1988 and was named “High Performance Concrete”, and later proposed as “Self Compacting High Performance Concrete”.
In Japan, the volume of SCC in construction has risen steadily over the years3. Data indicate that the share of application of SCC in precast concrete industry is more than three times higher than that in the ready-mixed concrete industry. This is attributable to the higher cost of SCC. The estimated average price of SCC supplied by the RMC industry in Japan was 1.5 times that of the conventional concrete in the year 2002. 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. The Brite-Euram SCC project4 was set up to promote the use of SCC in some of the European countries. A state-of-the-art report on SCC was compiled by Skarendahl and Petersson5 summarizing the conclusions from the research studies sponsored by the Brite-Euram project on SCC. A recent initiative in Europe is the formation of the project – Testing SCC6– involving a number of institutes in research studies on various test methods for SCC. In addition, an organization with the participation from the speciality concrete product industry – EFNARC7– has developed specifications and guidelines for the use of SCC that covers a number of topics, ranging from materials selection and mixture design to the significance of testing methods.
Current studies in SCC, which are being conducted in many countries, can be divided into the following categories: (i) use of rheometers to obtain data about flow behaviour of cement paste and concrete, (ii) mixture proportioning methods for SCC, (iii) characterization of SCC using laboratory test methods, (iv) durability and hardened properties of SCC and their comparison with normal concrete, and (v) construction issues related to SCC. These will be relevant to the immediate needs. In addition, the following questions also need particular attention, from a long-term perspective: (i) development of mixture design guideline tables similar to those for normal concrete, (ii) a shift to more ‘normal’ powder contents in SCC, from the existing high powder mixtures, (iii) better understanding of the problems of autogenous and plastic shrinkage in SCC, and (iv) development of site quality control parameters such as in ‘all-in-one’, acceptance tests.
