In the currently study, it should be noted that the bond characteristics between steel plate with stud and concrete has been remained to be estimated by the experimental study of one side or both sides shear experiments. However, it seems to be difficult to apply the simply accumulation resistance of stud and frictional resistance of steel plate and concrete with confined stress, to real concrete structures so as to be under comprehensive stress state i.e. bi-axial or tri-axial stress state. In this study, the experimental estimation for the effect of lateral pressure on the shear behavior is performed due to the modified experimental method of previous shear experiment in which the lateral pressure is controlled continuously to be constant values, and then the detailed modeling of the bond characteristics between steel plate with stud and concretes which is depend on the laconfined stress, is developed. Moreover, the applicability of developed model is estimated due to the comparison with experiment results.
The strength characteristic of Air Mortar has not been sufficiently clarified until now. So we carried out the unconfined compression tests, static loading tests and cyclic loading tests. The followings were obtained from the present study; 1) Unconfined strength was evaluated by two parameters, i.e., air content and water cement ratio; 2) The Air Mortar embankment has enough structural performance for loads of train.
Fatigue tests were carried out on welded steel wire mesh and RC beam in order to investigate the fatigue strength of welded steel wire mesh made with spot welding. Besides, welding residual stress and stress concentration at the crossing portion of the bars, which influenced fatigue performance of the mesh very much, were investigated by experiment and FEM analysis respectively. Fatigue strength of the mesh was mush higher than the specified design strength for welded steel reinforcing bar, because welding residual stress was small, and stress concentration is relatively mild. Finally, fatigue crack propagation analysis was applied to estimate the fatigue strength and propose a design curve for the steel wire mesh made with spot welding.
Fly ash cement prepared from high early strength cement (HPC) and fly ash (FA) was proposed and its ecological evaluation was performed. It has the following characteristics. Compared to ordinary portland cement (OPC), it has a shorter set time and has similar hardening characteristics to those of HPC. Its early strength up to age 7 days is higher. Its adiabatic temperature rise was about the same as that of OPC. Based on the ecological evaluation, the fly ash cement prepared from HPC and FA can reduce CO2 gas emission at its production by 20 mass% compared to OPC.
It was clarified that highly fluid concrete (HFC) added with slowly cooled blast furnace slag powder (CFS) showed the same degree strength of as that of HFC added with lime stone powder (LSP) and that it was hard to carbonation. The HFC added with CFS showed a greater increase in strength during the carbonation process as compared with the HFC added with LSP and, as a result, pore volume decreased as well to become rigid and dense. We assumed that carbonation after that was suppressed thereafter. It was also found that, as a result of carbonation, melilite and α-CS, which were main components of the CFS, reacted as well.
This paper describes the results of an experiment and the estimation of applied cement grout materials on the seismic retrofitting construction of reinforced concrete piers, where epoxy resin is generally used as an injection material. As a result, the value of compressive strength, unit weight, etc. shows no significant difference between heights, and it is stronger than that of normal concrete piers. In the two methods of construction, injection methods and dropping down, there is no difference in performance, therefore it is found out that the cheap method of dropping down is economically favorable. Cement grout materials are heavier than epoxy resin materials. Therefore, in the construction of cement grout materials, it is necessary to take notice of the stress in steel casing. However, it is possible to use less than allowable stress by evaluating the performance of the anchor bolts and arrangement suitably.
In Japan, many RC structures are damaged by chloride attack under marine environments. Based on this situation, establishment of “Repair Design System” for damaged structures and “Durability Oriented Design System” for newly constructed structures is strongly required. The indispensable information in these design systems is a quantitative evaluation of environmental conditions, in which structures are exposed. However, enough research data on this topic are not obtained. In this study, 2 years' exposure test of small size mortar specimens in 19 ports located from Hokkaido to Okinawa was carried out. From test results and their analysis, quantitative evaluation of environmental factors, affecting deterioration of mortar specimens is discussed. Through a series of experimental work, several environmental factors are selected as key factors that affect the steel corrosion in mortar and mortar deterioration.
Formerly, the experimental data indicating the expansion of Laumontite contained concrete under seawater environments is reported. However, the expansion mechanism or factors affecting the expansion are not clarified. In this study, through the analysis of expansively deteriorated old concrete, the cause of the expansion is confirmed to be the ettringite formation inside concrete. Furthermore, through the expansive test of mortar specimens, including several different factors, the following conclusions are obtained. Cement type or steam curing has no significant effect on the expansion generation and its magnitude. However, seawater supply to concrete surface is indispensable to generate the expansion of concrete.
The purpose of this study is to examine the effect of low-heat portland cement which control thermal cracking in thick concrete wall of cut and cover tunnels, through the measurement for massive concrete structures and the numerical analysis of a crack width by the finite element method. As a result of the examination, since use of low-heat portland cement reduces heat of hydration, and the compressive strength of concrete with it became high at early age and increased smoothly later when curing with high temperature was conducted. It is learned that use of low-heat portland cement is effective to control a thermal cracking of massive concrete structures.
In recent years, a technique for producing slag (MSW slag) by melting municipal solid waste or its incinerated ash at more than 1,300°C, and cooling it has been developed. This study examines 4 kinds of gasification MSW slag (rotary kiln, thermo select, fluidized-bed and coke-bed) and discusses the possibility of its utilization as fine aggregate for concrete. It is clear that the possibility is high because almost every MSW slag satisfies the quality standard as fine aggregate for concrete. Moreover, a concrete product of 50% slag replacement ratio to fine aggregate had no problem with strength and freeze-thaw resistance. It is, therefore, judged that the product can be put to use.
We study the expansive concrete filled steel tube with a flat bar in center using for a brace member of the energy dissipative braced frame. From the discussion of the compression test results of the expansive concrete with a water-(cement+admixture) ratio 20 and 30% in the tube, we proposed the estimation formulae of the chemical prestress of the concrete at yield of the steel tube and we showed the idealization of the compression characteristics of the concrete and the steel tube
Currently, a large amount of municipal solid wastes including domestic wastes are finally dumped and therefore the rate of recycling is not high. Technology for the production of MSW slag is being developed to assist in the recycling of these wastes. MSW slag is made from municipal solid wastes by high temperature processing, melting, and solidifying. If the MSW slag is able to be used for RC structures, the municipal solid wastes will contribute to the reduction of the final disposal of wastes. This report conducted some experiments with fine aggregate using MSW slag, and investigated whether MSW slag could be used for RC structures in terms of the seismic performance. Experiments were conducted to examine the flexural, shear, and bond failures of RC beam members. As a result, the RC beam members with MSW slag showed the same seismic performance as those of normal concrete. This indicated that the MSW slag could be used for RC structures in terms of structural performance.
This paper reports the performance of repair method with carbon fiber sheets for prestressed concrete beams, which were members of highway bridges, damaged by alkali aggregate reaction. Test cores were taken both parallel (horizontally) and perpendicular (vertically) to the direction of prestressing. Compressive strength and Young's modulus of the vertical cores were smaller than that of the horizontal cores. It was clarified that microstructure of horizontal cores were denser than vertical cores, because the prestressing prevented the expansion of horizontal concrete. The cores were effectively restraind with carbon fiber sheets in the expansion. The carbon fiber sheets can be expected to restrain the expansion of concrete damaged by alkali aggregate reaction because of water resistability and confinement.
Eco-cement is made from municipal waste incinerator ash, which contains much amount of Al2O3 and Cl-. Consequently Eco-cement contains much more amount of interstitial phase and Cl- than OPC. Although 20 to 40 mass% of Cl- in Eco-cement dissolved into free water within 3 hours, Cl- concentration decreased rapidly after that. In the case that Cl- content in cement was adjusted to 0.1 mass% by NaCl, almost all of Cl- in free water was bound as Friedel's salt in mortar with Eco-cement, OPC and Blastfurnace Slag Cement. The value of [Cl-/OH-] molar ratio of free water in each mortar was under 0.6 at 28 days, so steel corrosion is likely not to occur. In the case that Cl- content was increased to 1.0 mass%, Eco-cement bound more amounts of Cl- than other cements by producing much amount of Friedel's salt. Remained Cl- in free water, which was not bound as Friedel's salt was sorbed in hydrates such as C-S-H.
Distributed fiber optic sensing technique is being considered as a promising method to monitor continuously structural behavior such as the detection of crack, and the measurements of crack widths and overall deformation with a real-time manner, because current structural inspection technologies are not capable of responding to many of the monitoring needs pertinent to concrete structures. In this paper, in order to investigate and improve the monitoring capability of fiber optic sensors with BOTDR, first of all, several kinds of installation methods are proposed. Moreover the effectiveness is verified through testing instrumented RC beam specimen where the fiber optic cable is installed with the proposed methods. It is realized that the loop type of installation methods of fiber optic sensors can be effectively used to measure the crack damage within a relatively local area and the fixed point installation method of fiber optical sensor is capable of measurement of strain due to one or two localized cracks within a distance of lm resolution.