Self-Compacting Concrete (SCC) – The Latest Emerging Technology in Construction
SCC may not be a newly invented technology in the world. SCC was 1st conceptualized in 1986 by Prof. Okamura in Japan to improve the quality and stability of concrete structures. It is a high-flow, self-consolidating mixture of concrete which reduces the involvement of manual labor and associated defects. It flows practically like a liquid to assume the shape of the formwork/mold, though surprisingly, it does not contain a higher content of water compared with normal concrete.
Usage & Proven Benefits
Since the development of the prototype of SCC in 1988, the use of SCC in actual structures has been limited to special applications. However in modern day construction, it may prove to be a revolutionary technology in concrete construction. KPDK Buildtech has conducted in-depth analyses on this mixtures and has adopted this innovative technology in their project “Newtown Square� at Sector 95A, Gurgaon.
It has proved itself to be beneficial because of a number of factors, including:
Faster Construction Reduction in site manpower Better surface finishes. Easier placing Improved durability. Greater freedom in design. Thinner concrete section i.e. used in congested reinforcement. Reduce noise levels, absence of vibration. Safer working environment.
SCC may be used in pre-cast applications or for concrete placed on site. It can be manufactured in a site batching plant or in a Ready-Mix Concrete (RMC) plant & delivered to site by truck (TM- Transit Mixture). It can then be placed either by pumping or pouring into horizontal or vertical structures.
Case Study: SCC Concreting at Newtown Square, Sector 95A, Gurgaon
KPDK Buildtech has always attempted to adopt latest technologieswith regards to construction. At “Newtown Square”, Gurgaon, we have done over 1000 cum SCC mainly consisting of deep beams and slabs for the 3rd floor level transfer girder in our Newtown Square project in the past one month & also have planned for another 500 cum SCC @ 5th floor level transfer girder.
Each planned pour SCC at the project site was done for approximately 500 m3, which was poured continuously within 30 hours @ average speed of 16-18 m3/hr. This pace was maintained through multiple pumps working simultaneously, and during this period, the KPDK project team had kept a continuous monitoring on the quality, workability of SCC at site for an extended day/night vigil. Team-KPDK has ensured all necessary and specific design & test verifications are being carried out including slump tests , cube molding for on -site lab testing, post Rebound Hammer Testing etc.as per Indian Standard:456 to maintain our quality records. Post concreting 28 – Day Strength of 117% has been achieved!
SCC was done with the support of the countries’ top concreting experts such as Ultratech Cement Ltd & ACC Ltd. These companies have ensured high-end quality delivered through the use of sophisticated PLC Microprocessors & GPS Tracking systems to ensure timely delivery.
Additional Technical Aspects
Following are more interesting technical aspectson the use of SCC:
SCC technology has made possible by super-plasticizers . Super-plasticizers are an essential component of SCC to provide the necessary workability. Other types may be incorporated as necessary, such as viscosity modifying agents (VMA) for stability, air entraining admixture (AEA) to improve freeze-thaw resistance, retarders for control of setting etc. In SCC, admixture material added during the mixing process of concrete in small quantities related to the mass of cement (0.8-1.2% of total cementitious content) to modify the properties of fresh or hardened concrete. SCC is able to flow under its own weight & completely fill the formwork, even in the presence of dense reinforcement, without the need of any vibration, whilst maintaining homogeneity. It is able to remain homogeneous in composition during transport & placing. The max. size of aggregate in SCC depends on the particular application & is usually limited to 20 mm. In SCC , moisture content should be closely monitored & must be taken into account in order to produce SCC of constant quality. Due to the special rheological requirements of SCC, both inert & reactive additions are commonly used to improve & maintain the workability , as well as to regulate the cement content & so reduce the Heat of Hydration. Typical additions are:
Stone Powder Fly Ash Silica Fume Ground Blast Furnace Slag Ground Glass Filler.
Due to high content of powder, SCC may show more plastic shrinkage or creep than ordinary concrete mixes. Special care should also be taken to begin curing the concrete as early as possible due to SCC tends to dry faster than conventional concrete because there is little or no bleed water at the surface.
SCC should be designed so that workability is maintained to meet the requirement, Placing is faster, especially if a pump is used, but it is still essential to make sure that delivery & placing can be completed within the workability-retention time of the concrete.
Article by Vineet Kumar – Project Engineer, KPDK Buildtech Pvt Ltd