This paper estimates the effects of a composition change of ordinary Portland cement (OPC) with increased mineral admixtures up to 10% (hereafter 10OPC) on the quality and the environmental impacts based on the previous literatures in the past 10 years. The authors have shown that 10OPC with up to 2% increase in aluminate phase can have a satisfactory quality compared to conventional OPC. It is revealed that 10OPC’s production can reduce the CO₂ emissions by 50 to 56g/kg-cement compared to conventional OPC’s. On the other hand, composition change of clinker affected the amount of the waste for raw materials of 10OPC by -15 to 74g/kg-cement. In this report, quality of cement and concrete, and the environmental impacts in cement manufacturing were compared in detail by respective design of cement.

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 For the purpose of evaluating the environmental impact reduction method of cement manufacturing from an integrated viewpoint, environmental impact assessment of cement was conducted when the production method and environmental condition were virtually changed. As a result, from the viewpoint of improving the production method, the effects are greater in the order of waste use in clinker burning, reduction of coal consumption, and increase of the amount of mineral admixture used. On the other hand, from the viewpoint of improving environmental conditions, the effects are greater in the order of waste use in areas with high social value at landfill sites, change in coal procurement areas, and reduction of NO_X in areas with large impacts on health. In addition, as a result of evaluating the interaction between the production method and the environmental conditions, it is shown that the effect on waste use is very large and that it is useful as a method for reducing the environmental impact of cement production.

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 In order to create a concrete admixture that would effectively improve frost resistance, the authors prepared concrete specimens using paraffin emulsion and evaluated their basic properties including fresh properties, strength, waterproofness and freeze-thaw resistance. The results showed that adding more paraffin emulsion reduced the amount of bleeding and enhanced the waterproofing property and freeze-thaw resistance, without affecting the fresh properties and strength. The improved freeze-thaw resistance was likely because of aggregation of 1.0 - 1.5 micrometer paraffin particles in the emulsion into 25-150 micrometer particles which were thought to contribute to reduction of the freezing expansive pressure in the similar manner to the effect of entrained air.

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 Structures using ultra high strength concrete can have longer spans, greater heights and higher durability. There are an increasing number of civil engineering applications of ultra high strength fiber reinforced concrete (UFC), including construction of bridge beams and airport runway slabs as well as renewal of highway bridge slabs. In 2015, Taiheiyo Cement developed Porosity Free Concrete (PFC). This new matrix has a high compressive strength of about 400 N/mm² and still retains a high strength of about 300 N/mm² when reinforced with fibers for higher tensile performance. However, more experiments are necessary to determine the shear properties of PFC beams. It is expected that the ultra high compressive strength will be very effective when PFC beams are prestressed with a higher tensile force than that applied to PC beams using normal strength concrete.
　In this study, four-point bending tests were conducted on fiber reinforced PFC beams for the objective of investigating the shear capacity (V_u) of the fiber reinforced PFC beams. Moreover, the effects of prestressing level and prestressing steel ratio (p_w) were examined to evaluate the contribution of the fibers (V_f).
　The major findings are as follows. 1) V_rpc increased with the increase in the prestressing level, because of the expansion of the compression region which could be verified from the minimum principal strain distribution. 2) V_rpc increased with the increase of p_w , because of the increase in the neutral axis distance from the upper edge.

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 In this paper, applicability of the X-ray computed tomography scanner (X-ray CT) to cement-treated soil was examined using laboratory test specimens and field boring cores in the aim of developing an observation and analysis method for its internal structure. We aimed to clearly detect gradation changes due to the partial volume effect in the presence of cement, rather than directly observing the particle shape derived from cement. In the examination using the laboratory test specimens, proper tube voltage and current of the Xray CT suitable to determine the amount of cement stabilizer added were selected for each soil type, based on the peak separation on the gray value histogram. The magnitude of the gray values was found to be in good correspondence with the density and strength properties. In the examination of the boring cores, the gray value was found to be useful in detecting deterioration of the treated soil attributable to non-uniform distribution of cement stabilizer or drying. Moreover, it was found that the intensity of the gray values was consistent with the needle penetration gradient, showing local differences in strength in a boring core.

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 Inorganic selenium is one of the naturally occurring heavy metals commonly contained in excavation waste rock from tunnel and road construction, and its content often exceeds the elution limit specified by the Soil Contamination Countermeasures Act of Japan. Insolubilization of the selenium contained in excavation waste rock has been an issue because selenium(Ⅵ) cannot be easily reduced to a water insoluble form.
　In this study, the effect of selenium reduction by microorganisms present in excavation waste rock was investigated. In addition, lactic acid was added as a nutrient to promote the microbial metabolism, and its effect on selenium reduction was also evaluated. The results showed that the addition of lactic acid accelerated the selenium reduction and dramatically decreased the dissolved selenium concentration. The lactic acid concentration decreased in excavation waste rock where the dissolved selenium concentration decreased, demonstrating the consumption by microorganisms. It was shown that the microbial growth promoted by the added lactic acid may have contributed to efficient insolubilization of selenium contained in excavation waste rock through the combined effect of the selenium reduction in a coupled redox reaction and the selenium reduction associated with fermentative lactate degradation.

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