What Is Roller-Compacted Concrete?

Roller compacted concrete is a kind of dry and hard cement, using Portland cement, pozzolan admixture, water, admixtures, sand and graded coarse aggregate to make dry and hard concrete without slump. The same transportation and paving equipment as in the construction of earth and rock dams are adopted, and the layers are compacted by vibration. The RCC dam not only has the characteristics of small concrete volume, high strength, good anti-seepage performance, dam body can overflow, etc., but also has the advantages of simple, fast, economic, and large-scale general machinery for the construction process of earth-rock dams.

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Compared with other concrete, it has the following characteristics:

1. Cement: Basically consistent with the requirements of ordinary concrete cement. Correct

   Mixing: Ordinary concrete mixer can be used as the mixer. Because the RCC concrete has a small water content and belongs to dry hard concrete, the mixture is not easy to mix uniformly, so the mixing time should be appropriately lengthened. The falling height of RCC concrete should be minimized to avoid the largest aggregate dispersion.

   Material transportation: When transporting the mixture, it is transported by automobile. The material transportation vehicle must be covered with tarpaulin to avoid being exposed to the sun or rain.

   Paving: The construction speed of RCC concrete is mainly affected by the mixing ability and the paving speed, so it is very important to choose the appropriate paving method and machinery. Unloading, paving and liquidation are required to keep the RCC material unloaded on the concrete surface that has been closed. ^[2]

   RCC dams are broadly divided into two categories: one is the RCD represented by the Japanese "golden silver" model, which is filled with RCC at the center and the normal concrete (usually 2 to 3 meters thick) outside for seepage prevention and protection. The other is a fully-rolled concrete dam, called RCC, which has a low water-cement ratio and zero slump. It is vibrated and compacted by a vibratory roller.

   RCD adopts the general construction machinery and methods of earth and rock dams to compact concrete, the construction process is simple, the thin layer is poured through the warehouse, the warehouse surface is large, the mechanical efficiency is fully exerted, and the construction speed is fast.

   RCC has the advantages of simple structure, fast construction, high strength, less shrinkage, less cement usage, low cost, and reduced construction environmental pollution. RCC technology has been vigorously developed in China, and Puding RCC has now been completed

   According to the experience of Willock Creek Dam in the United States, the unit price of RCC is about 1/3 of that of conventional concrete. In just 4 months, all 300,000 m ³ concrete projects have been completed. The experience of Japanese dams has also shortened the construction period compared to the conventional pouring method. Daochuanchuan Dam saved 7000t of cement and reduced formwork by 44%. In China's Hangkou Dam, the construction period was shortened by half, cement was saved by 44%, and the overall cost was reduced by 16%. However, there are still some problems in RCC that need to be studied and solved. For example, the joint of layers is easy to become a weak layer of water seepage; the concrete transportation and paving process is prone to aggregate separation.