Title: Application of Superplasticizer to Reduce Drying Shrinkage and Thermal Cracking of Concrete

Author(s): Hiroshi Tokuda, Masami Shoya, Makoto Kawakami, and Makoto Kagaya

Publication: Symposium Paper

Volume: 68

Issue:

Appears on pages(s): 101-120

Keywords: proportiy admixtures; compr ts; cracking (fractu oning; plasticizers; essive s ring); c thermal trength; concretes; consist-uring; drying shrinkage; mix diffusivity;

DOI: 10.14359/6467

Date: 1/1/1981

Abstract:
This paper describes the results of an investigation to improve the drying shrinkage, thermal diffusivity and coefficient of thermal expansion of comparatively rich-mix concrete by the use of admixtures. Three types of superplasticizers were examined. Shrinkage tests were performed on 100x100x400 mm prismatic speci-mens in a controlled room where the temperature and the humidity were kept at 20°C and at 50 % R.H.. Two series of tests were made, one to make clear the character of shrinkage of concretes of low water-cement ratio and another to examine the effect of dosage of superplasticizer on shrinkage. Thermal diffusivity tests and the tests for the coefficient of thermal expansion were carried out using 10x20 cm cylindrical specimens of gravel concretes having a maximum cement content of 700 kg/m3, and attempts were made to improve these thermal properties by reducing the unit water content by the addition of a certain superplasticizer. It was found that the addition of superplasticizer to reduce the unit water content by about 20 percent, while maintainingthe constant consistency of concrete, gave a maximum increase of thermal diffusivity of more than 14 percent, a maximum decrease of coefficient of thermal ex-pansion of about 7 percent and a maximum decrease of drying shrinkage of almost 12 percent at 350 days drying. It is concluded that a suitable choice and use of superplasticizers should be used more specifically to improve drying shrinkage and thermal properties.