There is potential demand to make concrete light. However, complications regarding quality control of lightweight aggregates, decline in the tensile strength of lightweight concrete, economical problems, etc. have been inhibiting the promotion of its utilization. In this study, the strength properties of lightweight mortar were investigated. This lightweight mortar adopted the expanded polystyrene waste, whose volume was reduced by extreme infrared rays, as substitute for fine aggregate. The authors obtained the mix proportions of this lightweight mortar which have sufficient compressive strength as structural material. The other strength types were also investigated experimentally. As a preceding step, the most practical mix proportions were proposed from the viewpoint of viscosity, which was closely related to the segregation.

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The suppressing effect of fly ash on alkali-silica reaction (ASR) is different from the physical, chemical and mineralogical property of fly ash itself. This paper reports the important character of fly ash related to the suppressing effect on expansion of mortar due to ASR. The effectiveness of fly ash is affected by the specific surface area, amorphous silica, calcium content of fly ash and alkali content of cement. Fly ash containing high calcium content could not suppress expansion. In this study, a new index, using specific surface area, amorphous silica content in fly ash, alkali content of cement and fly ash volume per unit is proposed. This index was correlated with ASR expansion ratio of mortar incorporating fly ash.

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In order to clarify nonlinear interaction between pile and its surrounding soil under seismic load, full-scale monotonic and reversed cyclic lateral loading tests were carried out on concrete piles embedded into the ground. The test results revealed that the lateral load carrying capacity of pile is affected by the piling method and the stiffness degradation of cohesive soil subjected to cyclic deformation. In addition, 3-D finite element analysis was carried out based on the test results. With proper consideration of the above-mentioned factors, the analytical method was found to simulate well the actual behavior of pile-soil system.

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This paper presents the local bond characteristic of deformed bar embedded in early-age concrete. Fundamental experiments were conducted using mortar specimens with various thin covers of deformed bar. Many internal cracks were observed in early age. The relationships between local bond stress and slip were obtained from the uniaxial tensile test using concrete specimens with long bond length of deformed bar. The relationships include the effect of hydration and averaged concrete strain. The relationships after age of 2 days can be expressed by an equation in various locations along the deformed bar.

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Recently, large scale tunnel structures of high strength concrete are built in many countries. At the same time, there are several tunnel fire accidents occur in the world, and serious damages are reported. On this account a detailed research about fire-resistant capability of high strength concrete should be evaluated.
The objective of this study is to improve the fire-resistance of fiber reinforced high strength concrete. High strength concretes reinforced with polypropylene fiber, steel fiber, and hybrid fiber (combination of polypropylene and steel fiber) were evaluated in this study.
Test results clearly showed the change in physical and chemical property of high strength concrete after exposed to high temperature. The deterioration of micro structure, permeability behavior and crystal structure change of hardened cement were investigated. Furthermore, the behavior of high strength concrete exposed to high temperature such as the residual strength characteristic, the toughness deterioration and the fire-resistant capability, such as explosive spalling effect were also discussed precisely.

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Two-point probability functions were used to quantitatively evaluate geometrical characteristics of microstructure in hardened cement pastes with various water/cement ratios. The functions sensitively reflected changes in the microstructure with time. The specific surface area of unhydrated cement derived from the two-point function had information on the process of hydration of cement. Continuity of a phase such as capillary pores was well characterized by the lineal-path function. The characteristics quantified by the functions do not contradict the Powers model nor the concept of representative volume element. The two-point probability functions were useful to understand the process of hydration of cement and the microstructural features by spatial distance as a measure.

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The purpose of the present study is to investigate the curing effect for cracking resistance of expansive concrete. Flexural strength experiments were conducted in order to obtain the influence of amount of expansive material and wet-curing time. The experimental results indicated that RC beam with expansive material had higher strength and extensibility than that with normal concrete. Especially, the experiments implied the concrete with 40kg/m³ of expansive material had higher resistance to cracking.

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Steel-making slag concrete consists of by-products at ironworks. Steel-making slag concrete is expected as an environmentally friendly concrete. Steel-making slag concrete is used for foot protection block and small marine block, now. The purpose of this study is to enlarge the cover field of steel-making slag concrete productions. In this paper, elastic strain, thermal strain, autogeneous shrinkage strain and drying shrinkage strain of steel-making slag concrete are compared with those of normal cement concrete. Autogeneous shrinkage of steel-making slag concrete is very small due to high water absorption of steel-making slag, even when water to binder ratio of the concrete is quite small. Drying shrinkage strain at ultimate drying time of steel-making slag concrete is much bigger than that of normal cement concrete. Furthermore, drying shrinkage strain of steel-making slag concrete develops at a very low rate. They are due to the effect of high water absorption of steel-making slag. When drying shrinkage strain of steel-making slag concrete is predicted by JSCE model, water content in aggregate must be taken into consideration. On the other hand, Young's modulus, thermal expansion coefficient of steel-making slag concrete is as same as those of normal cement concrete. The effect of type of aggregate on those coefficients is small. As shown in this paper, the deformation of steel-making slag concrete can be predicted in design. It is possible to utilize the steel-making slag concrete in manufacturing of plain concrete structures such as large precast concrete armour unit or concrete block for retaining wall and revetment.

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When a part of fine aggregate in mortar is replaced with a mineral admixture, superiority or inferiority of the consistency of the mortar can be evaluated by the ratio of average thickness of excess water film to surface-volume average diameter of the particles of the solid materials in the mortar. The ratio can be calculated with the solid volume percentage of the solid materials and the mixture proportion of mortar. Adequate improvement of the consistencies of concrete can be realized by the replacement of a part of fine and coarse aggregates with a mineral admixture when the ratio calculated with the data of the solid materials and the mixture proportion of the concrete is the largest.

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In this study, we evaluated influence of quality of recycled fine aggregates which were made by a ball mill on flowability, strength, and chloride permeability of mortar. In addition, we studied about pore structures of mortar. Recycled fine aggregate is composed of original aggregate and old cement paste and there are rough and convexoconcave parts in the circumference. The mortar which was used recycled fine aggregates (L2) removed convexoconcave parts by a ball mill had almost same values of flowability, strength, and chloride permeability compared to recycled fine aggregate H or ordinary fine aggregate, although they are classified into recycled fine aggregate L (JIS A 5023) in the viewpoint of the density and the absorption. Also, although there is the transition zone which has a high CaO/SiO₂ ratio between aggregate and the new cement paste in ordinary, it was confirmed that the zone between aggregate and the new cement paste in the mortar which was used recycled fine aggregates has lower CaO/SiO₂ ratio.

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Scrapped plaster boards are crushed and the resulting materials can be classified either as waste gypsum (CaSO₄ · 2H₂O) or dust paper. Usually, about 70% of the wasted gypsum is used in reclaimed ground, while all the dust paper is incinerated. On account of these disposals, various environmental problems have emerged in recent years. Therefore, it is desirable to utilize them effectively. In this study, wasted gypsum and dust paper were recycled and used as hot mixed asphalt mixtures. Based on the results of laboratory tests, plant tests and field tests, the applicability of wasted gypsum and dust paper was confirmed.

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A property of SBS modified asphalt is improved by uniformly dispersed SBS particles into the asphalt in size of under 0.001mm. A mechanical property of a porous asphalt concrete can be estimated by a workload obtained from a flexural test of the asphalt. For the paving based on performance specification, it is important that both suppliers and constructors confirm the microstructure of SBS modified asphalt for the view point of guarantee of the performance. Same sample photomicrographs which show the condition for morphology of SBS into the binder are very useful to confirm the microstructure of SBS modified asphalt.

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There were typos and other errors in Doboku Gakkai Ronbunshuu E Vol. 63 (2007), No. 1 pp.185. Wrong:Vol. 63 (2007), No.1 p.185 Fig.11
Right:Vol. 63 (2007), No.1 p.185 Fig.11

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