Abstract
The European standards of common cements, EN 197-1:2000 & EN 197-2:2000, have been established and are expected to be drafts for ISO standards. This movement will encourage us to harmonize JIS with ISO standards and it is thought to be a good opportunity to re-evaluate the cement and concrete technology in Japan. As for the work towards the harmonization with ISO standards, it is necessary to investigate the European cements in their market. Based on this situation, we decided to re-examine the idea of the most suitable cement for the new century through the comparison of European common cements with Japanese common cements in the form of Japanese common concrete.
In the examination, six types of cements from two major European manufacturers in Germany and France and three types of cements in the Japanese market were used. The six European cements were of two different sets strength classes! 32.5, 42.5 and 52.5 in each country. The three Japanese cements were normal Portland cement, high early strength Portland cement and blast furnace slag cement type B. As a first step, physico-chemical analysis was carried out in order to know the difference in cement characteristics. As a result, it has been confirmed that the strength of German cements were controlled by changing the fineness. As for the French cements, the cement of the 52.5 class was similar to Japanese normal Portland cement. The cements of the other classes were manufactured by blending the normal Portland cement with blast furnace slag powder or limestone powder so as to control the strength.
Following the analysis of cement characteristics, the suitability of the cements for use as common concrete with 30N/mm2 of the characteristic strength was examined. In the fresh condition of the concrete, the segregation resistance was best in the cement of the lowest strength class because the use of this type of cement resulted in an increase in the powder content in the concrete. Then, the strength development and the durability such as neutralization, chloride penetration, freezing-thawing resistance, water permeability, and drying shrinkage were tested and the performances of the concrete using different cements was evaluated comprehensively based on these test results. It was concluded that the most suitable cement for the concrete of 30N/mm2 strength was the cement of the 32.5 class.
These examinations made us aware that the present Japanese cement is not always the best for common concretes. In the future, we will reconsider the most suitable cement in the Japanese construction market in the new century as well as the development of high performance and multi functional cement materials.
