This paper is focused on the effect of limestone and calcium sulfate contents on sulfate resistance of ground granulated blast furnace slag (GGBS) blended cement. Sulfate resistance was evaluated using length change over six years in accordance with ASTM C 1012, and sulfate resistance mechanism of GGBS blended cement was discussed by analyzing the hydration products and sulfate ion ingress. Although GGBS was found to suppress sulfate ion ingress, it was probable that alumina in GGBS would form ettringite with externally supplied sulfate ions. Addition of limestone and increase in calcium sulfate content allowed both monocarbonate and ettringite to form without generating monosulfate. This was thought to suppress further formation of ettringite with external sulfate ions during immersion in sulfate solution. GGBS blended cement with a suitable amount of limestone powder and a controlled content of calcium sulfate exhibited markedly excellent long term sulfate resistance.

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 This paper studies a stress evaluation method for expansive concrete using moderate- or low-heat portland cement. Thermal stress reduction effect and temperature dependence of restrained expansion/ shrinkage properties of these expansive concretes were investigated by uniaxial restraint tests under various temperature conditions with prestressing steel bars or invar steel bars embedded in the specimens. Moreover, material models were created for the analysis of the properties of these expansive concretes such as expansive strain and Young’s modulus based on the relationship between restrained expansion strain and reinforcement ratio. The analysis results with these models showed that stress occurring in expansive concrete could be approximated by the recommended method quantitatively under the temperature history assumed for mass concrete.

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 Super fibers such as ultrahigh molecular weight polyethylene (PE) are widely used in industry for their light weight and excellent mechanical and corrosion properties. However, concrete reinforced with these super fibers has only limited application. On the other hand, continuous fiber composites have been a focus of interest as a potential reinforcing material for concrete. The authors prepared RC beam specimens reinforced with mesh- or rope-shaped PE fibers and carried out loading tests on them to find their effects in improving shear carrying capacity and post peak behavior.

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 Box culverts were manufactured at an actual plant using heavyweight concrete which was designed with metal-slag-based heavyweight aggregate having a density of over 4.0g/cm³. Using high fluidity mix proportions for good workability, the authors examined influence of material segregation on the mechanical behavior of the product and its surface water-shielding performance at different vibration durations. It was found in the external pressure test that, within the range of this experiment, influence of vibration of up to ten times longer than usual was almost none on the mechanical properties of the box culvert products using medium fluidity concrete containing expansive admixture. On the other hand, surface water shielding performance of the concrete decreased at around the top surface of the form. Micro cracks of about 0.2mm were found in the surface during the external pressure test, but the concrete exhibited self-healing performance on them with an external supply of water.

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 Ordinary portland cement (OPC) in Japan is of a high strength type equivalent to a strength class of 52.5 of EN standard (197-1). However, low strength cement yields concrete of cement rich mix which provides an increased viscosity and improved resistance against material segregation. Therefore, when the emphasis is placed on workability and durability of concrete, cement rich mix with low strength cement is more suitable than cement poor mix with high strength cement. In this study, two types of 32.5 strength class blended cement were experimentally manufactured. Cement of this grade is commonly used in Europe. Ready mixed concrete was manufactured using these cements to evaluate the concrete properties, and wall-shaped specimens were prepared for outdoor exposure of ten years. Using core samples taken from the walls after the ten-year exposure, strength, carbonation and water permeability tests were carried out. Moreover, comparative analyses were made for reaction ratio of cement and pore structure of concrete by using backscattered electron imaging (BEI) and mercury intrusion porosimetry (MIP). The concretes using the experimentally manufactured low strength cements of 32.5 strength class were found to be comparable in properties with those using OPC or blast furnace slag cement type B.

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 Calcium nitride (Ca₃N₂) which is used in production of phosphor materials for LED is manufactured using calcium. Manufacturing high quality Ca₃N₂ with excellent phosphor characteristics requires high-purity calcium. However, calcium of stable quality is expensive and rarely available in the market. The authors examined a technique of distillation purification to obtain high-purity calcium from low-grade calcium which is easily available at reasonable prices. This study investigates the influence of the material of condensation plates used in the distillation purification equipment on impurity contents in distilled calcium. Four different materials with ease of processing were selected, and distillation experiment was carried out using condensation plates made of them. The results showed that materials not containing nickel were suitable for the components of the distillation purification equipment. It was also found that higher purities may be achieved by improving the distilled calcium recovery system and controlling distillation temperatures.

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