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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.

Many reinforced buildings were damaged by the Hyogoken-Nanbu Earthquake of 1995. In order to clarity the actual state of carbonation of the concrete and the chloride ion content in concrete of buildings in Hanshin area, the depths of carbonation and the amount of chloride ion were measured in 117 concrete samples that were obtained from 97 damaged buildings. The effects of carbonation depth and chloride ion content with regard to the corrosion of steel were also investigated. The measured carbonation depths were wildly scattered, and some of the concrete being heavily carbonated. The amounts of chloride ions in old river sand concrete were small. Large amounts of chloride ion were found mixed with sand, not only from the ocean but also from rivers in the buildings that were built between 1960 and 1978. These chloride ion were thought to be induced through sea sand and an admixture. The concentration of chloride ions in concrete were small for buildings that had been constructed after the regulation of the amount of chloride in concrete that was instituted in 1986. A great deal of the steel embedded in the carbonated concrete was severely corroded. The degree of steel corrosion tended to increase with an increase in the amount of chloride ion as well as carbonation depth.

This paper presents an empirical equation representing the relation between the amount of air laden chlorides reaching a concrete surface and the rate of chloride ions penetrating into concrete. By using this proposed equation as a boundary condition, an analytical diffusion model is presented, where various factors such as water-cement ratio (w/c), carbonation depth, and lapse of time after construction are considered. Comparing the analytical results obtained from the proposed model with the experimental results, the effectiveness of this proposed model is confirmed.

The relationship between the neutralization depth determined by a phenolphthalein 1% ethanol solution and the concentration distribution of CaCO3 - Ca(OH)2 in carbonated concrete is discussed, based upon accelerated carbonation and outdoor exposure tests, and field - survey research by making use of powder X - ray diffraction and thermal analytical methods. It was found that the neutralization depth exists in the partly - carbonated zone of concrete where both CaCO3 and Ca(OH)2 are observed, and that carbonation front depth from which CaCO3 is not detected, exists much deeper in concrete. Further, it was confirmed that the neutralization depth is about half of the carbonation front depth. This fact is interpreted by theoretical research of unsteady state dynamic analysis for the diffusion of CO2 from the surface inwards into concrete accompanied by carbonation reaction with Ca(OH)2 . Computer simulation was done for the converted CO2 concentration in carbonated concrete by using the effective diffusion coefficient estimated as a function of water cement ratio. If the converted CO2 concentration in the neutralization depth is assumed to be 10% of the surface concentration, the neutralization depth is almost the same as the depth calculated using Hamada's law which is considered to be adequately applicable for the progress of neutralization of concrete with a water cement ratio of 60% exposed outdoors in the rain. It is concluded that the relationship between the neutralization depth (X,,) and the carbonation front depth (X;) is expressed by the following equation : Xn = (l/2) Xf

When high-strength concretes are conveyed by pumping, the pumping pressure may increase and the flowability of high-fluidity concrete may be greatly decreased. This is a problem for construction of concrete-filled tubular steel columns. In this study, pumping tests and filling tests of steel tubular model columns with several kinds of high-fluidity concrete having a water: cementitious ratio of 30% were conducted. Silica fume results in better pumpability. The pressure loss reflects good correlation to the plastic viscosity of the concrete calculated from the time taken for it to discharge from an inverted slump cone. When the concretes used in the tests were pumped into tubular columns, the cavity area under the diaphragm plates was less than 10% and the core strength obtained at 91 days was over 80 N/mm*. If the slump flow of concrete at the top of the column is mote than 45cm, it can be expected that the column will be filled well. The pressure of concrete at the bottom of the column is approximately 1.2 times the head pressure.