In this study, experiments on shrinkage and expansion behaviors of high-strength concrete containing reactive aggregate were carried out. The strain distribution in the cross section was examined, and the effects of seal curing, cross sectional size, environmental conditions up to 14 days and dry-wet repetition on the shrinkage and expansion behaviors were investigated. The results proved in the case of high-strength concrete that the expansion caused by alkali-silica reaction started from outer layer under the condition of 40_??_ and of 97.5%R.H.. Further, it was found that the expansion caused by alkali-silica reaction came about at a small value of strain affected by autogeneous shrinkage.
In this study, deformation and fracture behaviors of concrete under impact triaxial compressive and hydrostatic loadings have been studied to discuss the concrete material model available for numerical simulation of reinforced concrete structures subjected to detonations. The impact triaxial compressive and hydrostatic loading tests were carried out with the Split Hopkinson Pressure Bar (SHPB) system with a pressure cell for two kinds of concrete specimens in static compressive strength, and the dynamic failure criteria and deformation property were investigated.
It is needed to clarify the alternation phenomena of cementitious materials that will be used for engineered barrier system in radioactive waste repository. We compared three accelerated leaching methods to clarify each characteristic phenomenon by applying same block-shaped OPC paste specimen to each leaching method. The most progression of alteration was observed in the penetrating method with forming the unique sequence of pore size distribution, ranging from 0.9 to 3 × 10-6m, which was thought to be derived from advective phenomenon. In the penetrating method, alteration of AFm-phases, AFt and C-S-H that facing to the pore followed after the disappearing of CH. In the process of alteration of C-S-H, Ca2+ leached out with gaining the polymerization (Chain-condition) rate of (SiO4) 4- in C-S-H. Even in such progressed alteration stage, much of AFt and Katoite (C-A-S-H) remained as the evidence of its high stability comparing to other cement hydrates.
A simplified procedure for single-story asymmetric building subjected to bi-directional ground motion is proposed. In this procedure, their responses are predicted through a nonlinear static analysis of MDOF model considering the effect of bi-directional excitations and an estimation of the nonlinear response of equivalent SDOF model. The results obtained by the proposed procedure are compared with the results obtained by the nonlinear dynamic analysis performed for simultaneous bi-directional ground motions. Their results are compared with the nonlinear dynamic analysis results, and satisfactory prediction can be found in nonlinear response of single-story asymmetric buildings.
Chloride induced corrosion of reinforcing steel is a typical cause of deterioration of RC structure. To maintain deteriorated RC structures properly, it is essential to determine the degree of deterioration accurately. In this study, the seismic performance, such as the strength and ductility, of RC beams deteriorated by chloride-induced corrosion of reinforcing steel are investigated by carrying out reversely cyclic loading tests. The results are summarized as follows : The accumulated dissipated energy of RC beam reduces with the progress of rebar corrosion, and the cracks in cover concrete caused by rebar corrosion decrease the seismic capacity of RC beam.
By using of original apparatus utilized gravity action for mixing of cemented sand and gravel, mixing efficiency and effect of different obstacles were examined. And falling mechanism by gravity force and analysis method of particle behaviors for simulation of mixing were studied. As the result, the mixing efficiency would be explained by the impacting momentum concerning of the products of impacting number, impacting velocity and impacting angle, and the effect for shape of the impacting obstacles, board, funnel or stick, would be able to explain by the correction factor on the formula of the impacting momentum were clarified. DEM analysis for the normalized particle distribution of sand and gravel was able to explain the falling by gravity and collision phenomenon to the obstacles by estimating parameters of the impacting energy and the frequency of the change the order of particles during falling.
Moderate-heat portland cement has likely been applied to mass concrete where as in this study it is applied to high-strength concrete with a designed strength ranging from 36 to 70 N/mm2. Fresh properties, strength development and temperature histories of full-scale model specimens of the high-strength concrete have been investigated. It was found that high-strength concrete with moderate-heat cement can be fully applicable to real construction practice on site. Moreover, some important prediction formulas and parameter value were derived : the maximum temperature of the model specimen with parameters of unit cement content and concrete temperatures, relationship between core strength and simplified adiabatic temperatures and a water-cement ratio by which column strengths in structure can satisfy the designed strength.
In this paper, a fundamental design concept and some experimental results are reported to develop a kind of intelligent concrete that has the self-healing function with heating device. Self-diagnosis composite is employed as the heating device that can heat up the damaged part in concrete. This heating device is embedded in concrete and it heats up the damaged part of concrete once a crack occurs to cross the device. In the meanwhile, a pipe protected by heat-plasticity film containing repair agent is embedded in concrete, too. Hence, selective heat around crack can melt the film to release the repair agent into crack and harden the repair agent in crack. Experimental results confirm the suggested method to be effective.
This paper deals with a new manufacturing machine of fine concrete aggregate which excels in grain shape and grading. In this paper, we report the experimental results of concrete aggregate made by the kinetic energy of many chains which rotate at high speed in the presented stone crusher. We carried out many crushing experiments using some raw stones, then examined the grain shape and grading of the produced concrete aggregates. As experimental factors, we changed the size, rotating speed, combination, and number of chains. We also considered the influence of the number of the crushing and the mixed raw stones. Consequently, it became clear that the presented stone crusher can produce the concrete aggregate with excellent grain shape.
In this paper, in order to evaluate the influence of dispersion of quality of concrete cased by construction errors on the maintenance management of concrete structure quantitatively, Repair-Risk was proposed. Repair-Risk was calculated by using the prediction result of deterioration of concrete structure considering with the dispersion of quality of concrete and the risk curve of repair cost. Even when two or more structures should be managed, the inspection plan (selection of inspection item, evaluation of the effect of accuracy of inspection method and selection of structure) can be made by using proposed method.
This paper presents a ratio of strength deterioration of R/C columns using high strength concrete up to 160MPa and high strength steel due to cyclic loading of the same drift angle. The ratio of strength deterioration was defined as second cycle strength over first cycle strength. The ratio was decreased as a displacement increased from maximun strength point to limit displacement point and a large correlation was found between the ratios at these two points and the limit displacement of R/C columns. Based on 36 test data, the estimate equations for the ratio at an optional displacement was proposed. The equations showed good agreement with the test data.