Integrated coal gasification combined cycle is a new power generation system with excellent energy efficiency. The system generates coal gasification slag, CGS, as an industrial byproduct, and the aggregate using CGS was included in the category of slag aggregate for concrete in the Japan Industrial Standards (JIS) in 2020. However, many are left unknown in terms of its influence on the long term properties of cementitious materials. In this study, mortar was prepared using CGS aggregate as fine aggregate, and changes in physical properties were evaluated over the course of one year. The use of CGS aggregate resulted in reduced drying shrinkage of mortar and increased Young's modulus, which was attributed to the high rigidity of CGS aggregate whose density was higher than that of natural sand. It was also found that, with a smaller water cement ratio and sufficient curing in water, the mortar had a significantly decreased volume of voids and developed a higher compressive strength over the long term period. Furthermore, microscopic observation revealed that a layer of reactants was formed on the surface of the CGS aggregate particles, indicating that the dense matrix was formed due to the pozzolanic reaction of CGS aggregate.

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 Use of mineral admixtures in cement has been promoted in the cement industry in the efforts towards a carbon-neutral society. On the other hand, the production of blast furnace slag, a typical mineral admixture, is forecasted to decrease in the future. This study experimentally investigated the properties of the mortar of blended blast furnace slag cement which was partially replaced with limestone powder, and also evaluated the influencing factors of the properties for the mortar. It was found that the partial replacement with limestone powder increased flowability of the mortar, shortened setting time and improved early strength development. When the replacement ratio of limestone powder was up to 10%, both 28-day compressive strength and water penetration rate coefficient of the mortar remained almost the same as those without replacement. Moreover, the results suggested that while porosity was the dominant influencing factor of the compressive strength, the complexity of the pore structure in the mortar had to be also taken into account for the water penetration rate coefficient.

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 Use of cement clinker for aggregate in cement is being investigated as one of the clinker applications under development. In this study, delayed ettringite formation (DEF) was studied for durability evaluation of the mortars using clinker fine aggregate. Furthermore, effectiveness of addition of fly ash (FA) was evaluated as a means to control DEF. The results showed that the mortar containing clinker fine aggregate, with or without the FA addition, had no expansion that could be attributed to DEF even at 484 days of age, indicating a high DEF resistance of the mortar. This was attributed to the use of clinker fine aggregate which made the mortar highly resistant to mass transfer, as well as to the fact that the pH in the mortar was kept high by the alkali supplied into the liquid phase from the clinker fine aggregate.

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 With the aging of factory equipment, the number of equipment failures and associated repairs has been increasing. In addition, in preparation for future manpower shortages, there is an urgent need to make inspection techniques more labor-saving and efficient. We focused on a 3D laser scanner for its capacity to capture the true shape of a kiln and worked to develop a new inspection method for kilns, the main equipment used in cement production. The dimensions of kilns were measured at several plants using a 3D laser scanner to understand the shape characteristics of the kilns, and shape evaluation was performed by using the elliptic approximation. By this method, it was possible to understand kiln- specific shape characteristics depending on the kiln diameter and obtain overall shape distribution of the kiln and local deformation distribution. The precise information obtained for the overall shape and local deformation of the kiln included the distance between the fulcrums which was previously unknown. This implies possible applications of the proposed method to the determination of a reasonable shell switching range or detailed inspection screening of deformed areas. In order to establish management guidelines that can be used to evaluate kiln health, periodic data accumulation will be necessary in addition to measurement at the time of failure.

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