Self compacting concrete compacts on its own, without any need for further compaction. Building concrete structures sans vibration has been accomplished in the past. For instance, the use of "tremie" facilitates the placement of concrete underwater without vibration. The placement of shaft and mass concretes can also be done successfully without vibration. But the fact is all the above mentioned instances of concrete are of minimized strength and consistent quality could be difficult to obtain. Modern applications pertaining to self compacting concrete are primarily focused on reliable and better uniform quality as well as high performance.
Researchers at Tokyo University began to develop self compacting concrete during the late 1980's, after recognizing the shortage of complete compaction and uniformity of concrete by vibration. Japan developed and utilized SSC that did not need vibration, by the early nineties. The SSC gained popularity in Japan by 2000, for ready mixed concrete and prefabricated products. With this, the use of self compacting concrete began to grow rapidly.
Self compacting concrete has been defined as the most radical advancement in the area of concrete construction for a period of several decades. It was originally developed in Japan for the purpose of balancing skilled labor shortage that was prevalent then. Over time, it has proved to be remarkably beneficial owing to the following advantages:
Quick construction.
Enhanced durability.
Site manpower is reduced.
The surface finish is better.
Placing is easier.
The working environment is safer too.
Materials Used for Self Compacting Concrete
• Ordinary Portland cement is used.
• The maximum aggregate size is limited to 20mm. For structures with congested reinforcement, a size of 10 to 12 mm is preferred. Aggregate size greater than 20mm can also be used whenever possible. Rounded and cubical aggregates that are well graded are also preferred. The quality of the aggregate has to be uniform, with regard to grading and shape.
Fine aggregates can either be manufactured or natural and the grading has to be uniform during the complete work. Close monitoring of the content of moisture and the aspects of absorption is necessary to avoid compromising on the quality of self compacting concrete. FINES are particles that are smaller than 0.125 mm. These particles have a say in the powder content.
• Mixing water: The quality of water has to be established on similar lines while using for prestressed or reinforced concrete.
• Chemical admixtures: One vital component of Self Compacting concrete that is required for necessary workability is super plasticizers.
Poly-carboxylated ethers, the new generation plasticizer, is specially used for self compacting concrete.
All other type of chemical admixtures can be incorporated as per the requirements, like Viscosity Modifying Agents (VMA), retarders for settings control and air entraining agents to enhance the resistance to freeze-thaw.
Self compacting concrete has won wide popularity in the past few years to be used for placement in highly congested reinforced concrete structures possessing difficult casting conditions. Hence, there must be good cohesiveness and high fluidity in the fresh concrete. Fine materials on the likes of fly ash can make sure that the concrete possesses such properties.
Recommend : Amazon Best Selling Civil Engineer Civil Engineering Overview General Civil Engineer
ไม่มีความคิดเห็น:
แสดงความคิดเห็น