Study on RCD Concrete with High Quality by Double Mixing Method and Milled Stone

Abstract

Roller Compacted Dam Construction method has been used for gravity concrete dam construction as a major method in Japan. Quality of RCD concrete depends on materials, especially fine aggregate.
Therefore severe selection for materials and strict quality control has been done on fine aggregate. Low quality aggregate should be adopted for the concrete dam construction in order to keep source of aggregate, if quality of concrete can be kept.
According to recent studies on the normal concrete, milled stone has been recognized as on excellen additional material to improve behavior of fresh concrete such as workability so on.
The Double Mixing method (which was expected enveloping sand with cement) was also assessed to reduce the bleeding of concrete and to improve quality of concrete.
The authors assessed quantitavely the effect of improvement of RCD concrete by these methods in laboratory test. It was observed that bleeding was considerably reduced and that workability was also improved by adding 30kg/m³ of the milled stone instead of fine aggregate. Quite similar tendency was observed by the Double Mixing method expected to sand enveloped with cement.