Hiroshi Yamada

The factors which affect drying shrinkage of concrete are material properties and environmental conditions, and so on. It is said that the type of coarse aggregate is one of the most dominant factors which affect concrete drying shrinkage. Therefore, it is important that the length-change properties of coarse aggregate particle are grasped when concrete drying shrinkage strain is estimated. Moreover, it is a practical benefit that concrete drying shrinkage strain is estimated by using coarse aggregate properties to be obtained the result early, regardless of the mix proportion of concrete. From the above backgrounds, in this research, we tried to estimate concrete drying shrinkage strain by composite model which has been proposed by KISHITANI &amp BABA, and investigated applicability of the model by using the initial tangent modulus or the secant modulus for coarse aggregate. For this study we used 19 types of crushed stone from different regions and of different qualities. As a result, the estimation of concrete drying shrinkage strain by KISHITANI &amp BABA equation was made different results of accuracy due to types of modulus of elasticity to be used for calculation. The calculated value against the experimental value was a range of -30 to +10% when using the initial tangent modulus, and was a range of -30 to +30% when using the secant modulus.

The cementitious material deterioration by biogenic sulfuric acid attack in sewage environments has become a severe problem for sewage related facilities. In general, it has been said that by using blast furnace slag sand to cementitious material is improved the resistance to sulfuric acid attack. In this research, we focused on blast furnace slag sand, and investigated, on resistance to sulfuric acid attack of mortar, the influence each of chemical composition, fineness modulus and sand to cement ratio of mix proportion. As a result, we indicated that the relationship between sulfuric acid attack resistance of mortar by using blast furnace slag sand and chemical composition of CaO, and fineness modulus, and sand to cement ratio of mix proportion, was a linear, respectively. We also indicated that sulfuric acid attack resistance of mortar by using blast furnace slag sand was improved larger chemical composition of CaO, smaller fineness modulus and larger sand to cement ratio, respectively. We found that by a change of 1% in chemical composition of CaO, by a change of 1.00 in fineness modulus and by a change of 1.0 in sand to cement ratio were changed the mortar weight loss of about 5%, about 13% and about 2.6∼3.7%, respectively. Moreover, from the result of multiple linear regression analysis, it was clear that fine particle of under 0.3mm of blast furnace slag sand was improved the sulfuric acid attack resistance of the mortar.

The factors which affect drying shrinkage of concrete are material properties and environmental conditions, and so on. It is said that the type of coarse aggregate is one of the most dominant factors which affect concrete drying shrinkage. It has also been pointed out that the pore structure of coarse aggregate affects drying shrinkage strain of concrete. From the above backgrounds, in this research, we focused on the pore structure of pore radius of 1 μ m or less for coarse aggregate and investigated the relationship between the coarse aggregate pore characteristics obtained by using mercury porosimetry and the drying shrinkage strain of coarse aggregate and concrete. For this study we used 10 types of crushed stone from different regions and of different qualities. As a result, we indicated a mutual relationship could be identified between the pore characteristics of coarse aggregate and the drying shrinkage strain of coarse aggregate or concrete when categorization by rock type was used. We also demonstrated that the average pore size of coarse aggregate, calculated from the pore characteristics obtained by using mercury porosimetry, was related to the drying shrinkage strain of coarse aggregate and concrete, and that it is possible that this relationship could be uniformly expressed by a power function.

The tensile creep test of the post-installed anchor was carried out by the improved spring type creep test equipment. The measurement of creep deformation from non-load and creep fracture time was possible over a long period of time by this equipment. The creep deformation at about 1/3 load of the maximum load increase slightly for the duration of 90 day, but the creep deformation is very small, and creep fracture will not occur in 50 years. And at 80% of the maximum load, creep fracture occurred in 168 days.