To understand the effects of multiple ions in seawater on the penetration of chloride ions and the alteration of the solid phase of hardened cement, immersion tests were conducted with four different solutions. In the case of mortar, chloride penetration was accelerated in NaCl+MgSO₄ solution and suppressed in artificial seawater, as indicated by the results of the immersion test for 1736 days. This was thought to be due to the influence of aragonite brucite gypsum, and ettringite formed, and leaching of CSH on the mortar surface. For concrete, the results of 1008 days of immersion test showed that regardless of the type of immersion solution, there was no portlandite in the area up to 10 mm of the concrete, suggesting that changes in the pore structure due to leaching affected the penetration of chloride ions.

 Ultra-High Performance Fibre Reinforced cementitious Composite (UHPFRC) is characterised by high compressive/tensile strength and very low permeability. Application of UHPFRC to structural members subjected to severe mechanical actions and environmental conditions, such as bridge decks, can take full advantage of these excellent properties. When UHPFRC is cast on existing structures, its shrinkage is restrained and tensile stresses are induced over the entire depth of the UHPFRC. Therefore, it is necessary to understand tensile properties and restrained shrinkage behaviour of UHPFRC for developing a method to strengthen and rehabilitate structural members with UHPFRC.

 This paper presents results of direct tension tests and uniaxial restrained shrinkage tests of UHPFRC. UHPFRC mix used in the experimental tests is characterised by mortar matrix densified by ettringite (AFt) formation; thus, it is called “AFt-UHPFRC”. The direct tension tests are conducted for three UHPFRC mixtures and effects of wollastonite, fibre type and content, and curing conditions on tensile behaviour of the UHPFRC are discussed. The uniaxial restrained shrinkage tests are performed using a Temperature-Stress Testing Machine (TSTM) that allows investigating restrained shrinkage behaviour of cementitious materials from very early age. It is found that tensile creep significantly relaxes tensile stress due to restrained shrinkage and no microcracking occurs in UHPFRC under a full-restraint condition. Moreover, it is understood that although shrinkage strain of heat-cured UHPFRC is lower than that of UHPFRC without heat treatment, tensile stress induced due to restrained shrinkage is larger in heat-cured UHPFRC than UHPFRC without heat treatment.

 The aim of this study is assessing behaviors of buried flexible pipes at applying the internal loading method (ILM) for evaluating the strength of these pipes. In this study, behaviors of buried and un-buried pipes were compared using a polyvinyl chloride (PVC) pipe and a fiberglass reinforced plastic mortal (FRPM) pipe. As a result, the relationships between load and deformation of buried pipes showed nonlinearity, in which deformation ratio increases with the increment of applied load. The curve lines were thought to be classified into two stages; before and after the occurrence of the small shear failure in back-filling soil. Because of the restraint by the backfilling soil, the inclination of load-deformation curves of buried pipes became larger for both kinds of pipes. The difference of inclination between buried and unburied pipes was larger with the PVC pipe whose ring stiffness is smaller than the FRPM pipe. In the circumferential direction on the outside of buried pipes, tensile strains accrued especially at both of top and bottom parts of it. On the contrary, compressive strains gradually increased at the four portions oblique to the loading axis. This result indicates that expansion of the diameters in oblique direction is restrained by backfilling soil around buried pipes.

 Production of ultra-high strength fiber reinforced concrete (UFC) generally requires heat-curing of high temperature. The UFC manufacturing at a site is often hard because of no heating equipment. The purpose of this study was to investigate proper materials and mixture for a UFC manufacturable under ambient temperature. In addition, to confirm the applicability of the developed UFC, the study conducted fundamental tests at a site by using the UFC supplied from a ready-mixed concrete plant. The study showed that a cement with a low C₃A and high C₃S content, water-binder ratios of 14% to 21%, and flow of 230mm to 290mm are suitable for the UFC without heat curing.