Concrete Journal

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In December 2009, the Concrete Committee of the Japan Society of Civil Engineers set up a subcommittee for Study for Silicate-based Surface Impregnation Method for Concrete Structures. With 47 members under chairman Professor Koji Takewaka of Kagoshima University, the subcommittee completed its work in March 2012. Among several surface protection methods, the subcommittee focused its activity on silicate-based penetrants that are able to improve properties of concrete surface layer, to heal cracks and to prevent deteriorations of concrete structures. The main components of silicate-based surface penetrants react with calcium hydroxide which is formed during the process of cement hydration, and form a C-S-H gel in the concrete. The main components used in commercialized penetrants are lithium silicate, sodium silicate, potassium silicate or their mixture. In the actual products, however, it is unusual to find just one of these ingredients; most of the penetrants contain various additives and minor ingredients that aim to stabilize reactivity of main components and to improve their physical properties. However, from an engineering point of view, it is little meaning to categorize silicate-based surface penetrants according to these additives and minor components. The subcommittee, therefore, proposed a classification of surface penetrants into two types that are “Solidifying type” and “Reactive type”, according to improvement mechanisms of the main components on concrete surface.

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This paper outlines the state of the art report on construction performance and issues related to examination and inspection systems for fresh concrete. We identified the problem and limitation of the present evaluation system of construction performance and issues related to the current slump test, and carried out a factor analysis (interrelation diagram) on quality control issues and quality problems with regard to the construction of civil engineering structures. Based on this understanding and results, this paper describes measures to ensure workability needed for construction. This paper also proposes experimental methods for examinations and inspections related to the design of concrete mix proportions as alternatives to the slump test.

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In Limestone Association of Japan, in order to make everyone correctly understand the properties of crushed limestone aggregate, Committee on Concrete Aggregate was established by the specialists in limestone resources and concrete materials in 2008. In our Committee, we stacked the test data on the properties of concrete with limestone aggregate and widely collected latest technology findings and data. Furthermore, we made an in-depth study on various issues. Since we summarized the results as “Limestone Aggregate and Concrete - Addendum (2012) ”, we will introduce here its main points.

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