Abstract
We have carried out experiments on the use of “Masa-do” as a fine aggregate for concrete since 1981. The term “Masa-do” is applied to the residual soil derived from the weathered granite or decomposed granite in Japan. From these experiments, it was shown that “Masa-do” can be used as a fine aggregate for concrete.
In this paper, experimental studies on the resistance of concrete made with “Masa-do” as a fine aggregate to freezing and thawing are discussed. After curing in water at 20°C for 14 or 28 days, the concrete was exposed to freezing and thawing in the laboratory. The type of exposure is rapid freezing in air and thawing in water. The test piece is a prism with 10 cm square and 40 cm long.
Weight, volume, bulk density, dynamic modulus of elasticity, ultrasonic pulse velocity, flexural strength and compressive strength were measured. These factors were compared with the each initial value after 14 or 28 days, and the resistance to freezing and thawing was evaluated. From the experiments carried out for three years since 1988, the following results were obtained.
1) The plain concrete (without air entraining agent) made with Masa-do as a fine aggregate has a lower resistance to freezing and thawing than that made with river sand.
2) Whenever the air content of concrete was increased to 4% or more by an air entraining agent, the resistance to freezing and thawing was improved considerably.
3) To evaluate the resistance of concrete to freezing and thawing, ultrasonic pulse velocity as well as dynamic modulus of elasticity are the effectual methods.
4) The bulk density of concrete is not influenced by freezing and thawing, because freezing and thawing is not the chemical attack.
