The authors have proposed a partially pre-cooling system for massive structures, such as gravity concrete dams. It is discussed in this paper how the effectiveness of the proposed method is discussed using the finite element analysis. In the ordinary pre-cooling system, pre-cooled concrete is placed in the entire region (width and depth) of a massive structure. In the proposed system , pre-cooled concrete is placed only in the surface layer. In order to evaluate the effectiveness of this system, a thermal stress analysis was conducted by the finite element method. The key parameters were the dimensions of the cooling system and cooling temperatures. The results show that the proposed system is rather effective than the conventional cooling system in terms of the thermal stress condition of massive concrete structures. In addition, the cost benefit is adequately expected.

The purpose of this paper is to develop pre-casting permanent forms which are effective in improving the durability and appearance of concrete structure, conserving wood and modernizing cast-in-place concrete work. The influences of various materials used and accelerated curing methods on the properties of PCM(polymer cement mortar) applied to the forms were investigated. In these experiments, polymer dispersions composed of SA(styrene-acryl), PAE(polyacrylic ester), EVA(ethylene-vinyl acetate) and SBR(styrene-butadiene rubber) were used. Mixtures contained aggregate ; crushed silica and ferro-nickel slag sand, cement ; normal Portland, high-early strength portland and white portland cement, and color pigment ; red, green, yellow and black color pigment, were used. Steam curing and oven-dry curing were carried out. The fluidity, compressive strength, flexural strength, resistance to abrasion, chloride ion penetration, carbonation and sulfate, and surface color of PCM were examined. From these investigations, the following conclusions can be obtained. The use of SA type polymer, ferro-nickel slag sand, high-early strength portland cement and color pigments were effective in getting PCM with high fluidity, mechanical strength, durability and tinting strength. Additionally, steam curing and oven-dry curing are practical for the early-age strength development of PCM.

This paper discusses the mechanism of the setting shrinkage of polymer concrete with liquid resin mainly composed of methyl methacrylate (MMA-PC) and reports the study results on the method for reducing the setting shrinkage. The setting shrinkage is classified into two large categories, that is, shrinkage due to polymerization and shrinkage caused by temperature decrease after the maximum temperature is reached. The shrinkage amount due to temperature decrease is in proportion to the liquid resin content. The authors demonstrated that the shrinkage due to polymerization significantly vanes with the formation state of matrix of liquid resin with tiller. For reducing the shrinkage, it is effective to confine the shrinking strain by adding fibers and modifying the filler properties to limit the volume change due to polymerization.

The durability and strength characteristics of high-volume fly ash concrete were studied in order to utilize fly ash, an industrial by-product from coal fired thermal power plants, as a typical admixture for concrete. The results of this study were as follows: (1) The strength development of high-volume fly ash concrete is higher than that of conventional concrete. (2) There is an optimum mixing ratio of fly ash, in which the compressive strength reaches a maximum level. (3) Freezing and thawing resistance of high-volume fly ash concrete is almost the same as that of conventional concrete. (4) Abrasion resistance, durability in marine environment, and water-tightness are improved by the use of high-volume fly ash. (5) Adiabatic temperature rise can be reduced compared with that of concrete without fly ash.

Two aspects of researches concerning the self compacting concrete techniques have been extensively carrying out in Japan. One aspect is to find a systematic way to evaluate the consistency experimentally. The other is to seek a theoretical way to predict the properties. Thus for the first goal, in this paper three kinds of methods including the dragging ball viscometer test, the slump flow test and the 075 funnel test were proposed to investigate the influence of concrete mixture proportions on the consistency of viscous agent series self compacting concrete. For the second goal, a numerical approach was initially proposed to simulate the behavior of self compacting concrete called Modified Distinct Element Method (MDEM). The applicability of MDEM is verified by comparing the simulation results with the experimental results of the above three types of tests.