In this study, to analyze the change of mass of concrete structure subjected to fire damage, cement paste was exposed at high temperature to maintenance time and analyzed mass change characteristics by TGA analysis. As a result of analysis, the mass reduction rate of cement paste decreased with increasing heating time after heating at high temperature.
Generally, reinforced concrete structures are exposed to complex deterioration. It is necessary to investigate the effect of decreasing the strength of reinforced concrete structures subjected to aging more frequently. Therefore, this study aims to analyze the resistance to freezing and thawing during complex deterioration. After the beam specimens were prepared, the freezing and thawing tests were carried out and the strength of the specimens subjected to freezing and thawing decreased as a result of 4 - point bending test.
In this study, it evaluate the Local damage properties of amorphous metallic fiber reinforced cement composite by different fiber length. 30mm and 15mm length of amorphous metallic fiber was reinforced and fiber volume fraction was set to 1.0, 1.5 vol.%. Flexural test and high speed projectile impact test was performed. As as result, 30mm length of specimen showed more good flexural and impact resistance performance compared to 15mm length of specimen.
This study was conducted to evaluate the effect of self-sensing performance on strain-hardening cement composite containing CNT by curing age. The mixing amount of CNT was set at 1.0%, and SHCC fibers were mixed with PE 1.0% and steel fiber 0.5%. The electrical resistance measurement for the tensile strain sensing performance was based on AC method and 4 probe methods. Test results indicated that electrical sensitivity of SHCC decreased with an increase in curing age.
This paper describes the mechanical properties of high strength concrete with 1,600 MPa strength steel fiber. The fiber aspect ratio and fiber volume fraction used in this study is 80 and 0.75%. The Cylindrical specimens with ∅150×300 mm and the prisms with 150×150×550 mm were mad and tested in accordance with KS F2403 and ASTM C1609. As the result, specimens with high strength fiber has superior performance then that with normal strength fiber.
The purpose of this study was to evaluate the direct tensile fracture behavior of steel fiber hybrid reinforced cement composite by strain rate. Experiment result, it was confirmed that SSF suppressed the microcrack around the HSF at the strain rate 101/s, which resulted in the improvement of the pullout resistance of the HSF.
This research provide a general model for viscosity curve. The rheological behavior of cement-based materials has been described by a flow curve. The flow curve helps intuitive understanding to explaining the flow of concrete. However, in this study, the rheological behavior of cement paste was analyzed using different approach called the viscosity curve. In this study, Sisko model for viscosity curve is used to indicate the rheological behavior of cement paste. Also relaxation process is analyzed by exponential model.
In this paper, an experimental program has been conducted to investigate shrinkage of fast hardening concrete (FHC) which is used to replace the existing ballasted track with concrete track. In the test, curing method was considered as a test variable. The test results indicated that autogenous shrinkage was dominant on FHC while drying shrinkage was negligible. To represent shrinkage of FHC, a new model has been proposed through regression of the test results.
In this paper, possibility of cracks in fast hardening track has been analyzed with consideration of shrinkage of fast hardening concrete. To evaluate tensile stress on fast hardening track, the analysis considers restrain effects by frictions due to subgrade and rail fastener. The analysis results indicated that the maximum tensile stress in fast hardening track increased as the continuous casting length of fast hardening concrete increased. To prevent cracks due to shrinkage, it was investigated that the continuous casting length be less than 66.9 m.
In this study, the mechanical properties of concrete incorporating blast furnace slag with 60 % were analyzed according to CBS-Dust replacement rate. Results indicate that replacement of more than 10 % of CBS-Dust have a positive effect on reducing waste disposal costs and strength improvement
In this research, the rheological properties of mortar under high pressure were measured in order to investigate the cause of segregation of concrete after pumping. A rheometer with high pressure cell was used to measure rheological properties under 100 bar to 200 bar. The rheological properties were measured at three steps; before pressurization and after pressurization. The rheological properties of high-range water reducing admixture were measured by different composition ratio. The viscosity curve was used for the measurement, and the results were analyzed using a sisko-model.
In this study, the effect of compressive loading of carbon nanotube (CNT) mixed cement composites was investigated. To evaluate the electrical resistivity variation of 30%∼60% of compressive load of cement composites containing 1.0% CNT, 1.0% CNT was added to cement composites and compressive strength was calculated. The greater the change in electrical resistance to compressive load, the more vulnerable to internal conductive networks. Also, as the amount of CNT mixed increases, the electrical resistance to the load is more sensitive and it is expected to be mixed more than 1.0%.
of ordinary Portland cement. Water-cement ratio was 0.40 and cement-sand ratio was 1:3. The content of nano-TiO2 was 3% but the content of nano-SiO2 changed in cement mortars. The content of nano-SiO2 was 0%, 0.5%, 1%, 1.5% and 2% of the binder weight. Mortar prisms and beams were made in specified molds and cured in limewater. Compressive and flexural strengths, porosity and ultrasonic pulse velocity were measured. Then mortars were stored in 6 molar ammonium nitrate (NH4NO3) solution. Leaching depth, variation of mechanical and microstructural properties were measured. Presence of nano-particles decreased the leaching depth and the degradation of mechanical and microstructural properties in mortars.
As a method to improve the water purification performance of porous concrete through existing studies, it has been analyzed how to substitute effective microorganisms at a certain rate for use or immersing porous concrete in a culture solution. In this study, we tried to compare and analyze the viability of microbial cells after mixing spherical microbial cells with useful microbes and natural materials in order to more easily apply high - concentration microbes.
This research provides an analysis of experiments on sulfuric acid resistance of alkali-activated slag mortar with dolomite powder. The results show that the longer the bedding time, the lower the mass change in all specimens. Among them, the mass change in a dolomite replaced specimens are shown to be less than that of a non-dolomite specimens. Since the composition of dolomite reacts with sulfuric acid solution to produce a product, it is thought to play a role in reducing mass reduction.
In this study, the conventional model for the yield stress with the volume fraction of aggregate, where the volume fraction of aggregate was considered separately into the volume fraction of fine and coarse aggregate. The modified model equation can be applied to relate the yield stress of the wet sieved mortar and that of the concrete. Based on the model equation and the mix proportion of concrete, the yield stress of concrete is well predicted, which contributes the simplification of the performance evaluation process of concrete.
This study was conducted to propose a strength correction factor to compensate the strength delay at designed age caused by the temperature drop in low temperature condition. Strength correction factors due to temperature drop T28 were provided using the constant function model.
As a result of this study, the testor penetration resistance and the hardness of the durometer are considered highly correlated and are thought to be effective when using the durometer to determine the setting time in the field structure.
This study was conducted to compensate for the decrease in intensity due to the decrease in temperature and proposed temperature correction strength T28, using the Fractional function model.
In this paper, fracture behavior of high-strength SFRC with high tensile strength steel fiber was investigated. Two different steel fibers with tensile strength of 1,200 and 1,600 MPa was used in SFRC specimens. Tst results showed that fracture behavior was more ductile with increasing the steel fiber tensile strength.