Current Issue : October - December Volume : 2017 Issue Number : 4 Articles : 5 Articles
The paper deals with the experimental determination of shrinkage development during concrete ageing. Three concrete mixtures\nwere made.They differed in the amount of cement in the fresh mixture, 300, 350, and 400 kg/m3. In order to determine the influence\nof plasticiser on the progress of volume changes, another three concrete mixtures were prepared with plasticiser in the amount of\n0.25% by cement mass. Measurements were performed with the goal of observing the influence of cement and plasticiser content\non the overall development of volume changes in the concrete. Changes in length and mass losses of the concrete during ageing\nwere measured simultaneously. The continuous measurement of concrete mass losses caused by drying of the specimen�s surface\nproved useful during the interpretation of results obtained from the concrete shrinkage measurement. During the first 24 hours of\nageing, all the concrete mixtures exhibited swelling. Its magnitude and progress were influenced by cement, water, and plasticiser\ncontent. However, a loss of mass caused by water evaporation fromthe surface of the specimens was also recorded in this stage. The\nmeasured progress of shrinkage corresponded well to the progress of mass loss....
Research on mechanical property of SFRC was done through experiments of two SFRC T-beams and one concrete T-beam, while\nthe influences of different volume fractions of steel fibers on integral rigidity, ultimate shear capacity, and the crack distribution\ncharacteristics were analyzed. ANSYS finite element software was used to simulate the tests and it was found that there was good\nconformation between the results of ANSYS simulation and tests. The test results and finite element software simulation both\nshowed that the incorporation of steel fibers in the concrete can increase the integral rigidity and ultimate shear capacity, while\npartially reducing the propagation of cracks effectively. It was also proved that it is reliable to simulate SFRC T-beam by ANSYS\nsoftware....
The influence of crumb-rubber on the mechanical properties of Portland cement concrete (PCC) is studied by experimental tests\nand numerical simulations.Themain hypothesis of the study is that replacing part of the stone aggregate with crumb-rubber in the\nmix modifies the energy dissipation during the cracking process and affects the concrete behaviour under monotonically increasing\nloads. The experimental research programcharacterizes themechanical properties of PCC for three different types of concrete with\na variable content of crumb-rubber.The experimental results showed that fracture energy and other properties are directly related\nto the rubber fineness used in the mixture. The material properties derived for these laboratory tests are used to study, by numerical\nmodels, its response through its damage evolution. The numerical model used to simulate the damage evolution of the concrete is\nthe Embedded DiscontinuityMethod (EDM). One characteristic of the EDMis that it does not need to modify the mesh topology to\npropagate the damage through the continuum solid. For this study, the Disk-Shaped Compact Tension specimen geometry, normed\nby the D7313-13 of the ASTM, is used. Results showed that the numerical methods provide good approximation of the experimental\ncurve in the elastic and softening branches....
About 20 billion square feet of Ethylene Propylene Diene Monomer (EPDM) rubber is\ninstalled on roofs in the United States and most of them will be reaching the end of their lifespan soon.\nThe purpose of this study is to investigate potential reuses of this rubber in Civil Engineering projects\nrather than disposing it into landfills. First, laboratory tests were performed on various shredded\nrubber-sand mixtures to quantify the basic geotechnical engineering properties. The laboratory test\nresults show that the shredded rubber-sand mixture is lightweight with good drainage properties\nand has shear strength parameters comparable to sand. This indicates that the rubber-sand mixture\nhas potential to be used for retaining wall backfill and many other projects. To assess the economic\nadvantage of using shredded rubber-sand mixtures as a lightweight backfill for retaining walls\nsubjected to static and earthquake loadings, geotechnical designs of a 6 m tall gravity cantilever\nretaining wall were performed. The computed volume of concrete to build the structural components\nand volume of backfill material were compared with those of conventional sand backfill. Results show\nsignificant reductions in the volume of concrete and backfill material in both static and earthquake\nloading conditions when the portion of shredded rubber increased in the mixture....
Cement-based composites belong among the basic building materials used in civil\nengineering. Their properties are given not only by their composition but also by their behaviour\nafter mixing, as well as by the methods of curing. Monitoring the processes and phenomena\nduring the early stages of setting is vital for determining the resulting properties and durability.\nThe acoustic emission method is a unique non-destructive method that can detect structural changes\nas a cement-based composite is setting. It can also detect the onset and growth of cracks during the\nservice life of a cement-based composite since the moment it has been mixed. The paper discusses the\nuse of the acoustic emission method with a focus on the early stage of the lifespan of a cement-based\ncomposite including the measures necessary for its use and description of the parameters of acoustic\nemission signals....
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