Abstract: This paper presents the results of the experimental works to investigate the use of waste limestone from water treatment industry as fine aggregate in green concrete. Two concrete mixtures with a constant water-to-binder ratio of 0.3 were prepared for this investigation, in which, the normal concrete mixture was designed following the guidelines of ACI 211 standard, while the green concrete mixture was designed using densified mixture design algorithm (DMDA) technology. For comparison, both types of concrete samples were subjected to the same test program, including fresh properties, compressive strength, strength efficiency of cement, drying shrinkage, electrical surface resistivity, ultrasonic pulse velocity, and thermal conductivity. Test results indicate that both concrete mixtures showed the excellent workability due to the round-shape of waste limestone aggregate and the use of superplasticizer. In addition, the green concrete mixture exhibited a better performance in terms of engineering properties and durability in comparison with the normal concrete mixture. The results of the present study further support the recycling and reuse of waste limestone as fine aggregate in the production of green concrete.
Abstract: The soil-cement columns are generally installed and cured in the soft clay layers under confining pressure. The strength of the soil-cement columns may be influenced by confining pressure during curing period. In this study, the main objective was to study the influence of curing pressure on unconfined compressive strength of cemented clay. A series of unconfined compression tests was performed on a cement admixed clay sample cured under pressure values of 0 kPa (atmospheric pressure), 25kPa, 50kPa and 100 kPa using a typical unconfined compression equipment. The test samples with values of cement content of 0.5, 1.0 and 2.0 percent were cured for 28 days.The stress-strain curves obtained from all tests show a peak value of stress. The unconfined compressive strength or peak stress obviously increased with increasing cement content for all curing pressure conditions. It can be observed that the strength of samples gradually increased with curing pressure for cement content of 0.5 percent. For cement contents of 1.0 and 2.0 percent, the strengths of samples cured under pressures of 25 kPa dramatically increased from the strength of samples cured without pressure (0 kPa), however, the strengths of samples for curing pressures of 25, 50 and 100 kPa were not clearly different.
Abstract: Rebar steel is used in the construction of various buildings. Vanadium (V), one of microalloying elements, is often added in the rebar steel to improve mechanical property. In order to analyse the effect of V on the microstructure and property of rebar steel, 0.043 wt.% V was added in a 20MnSi rebar steel. The base steel and V added steel were refined in a 50 kg vacuum induction furnace and rolled to plates of 14 mm thick. The mechanical properties of two steels were compared by tensile tests on a Wan-10000 tensile testing machine. The microstructure and precipitation of two steels were analysed by SEM and TEM observations. The microstructures of two steels consist of ferrite and pearlite. However, the grains of V bearing steel are finer. Moreover, fine nanoscale precipitates of V can be observed in V bearing steel. Therefore, the mechanical property of V addition rebar steel is improved by gain refinement strengthening and precipitation strengthening.
Abstract: The main aim of this paper is determined of properties, especially granulometry, of recycled silicon carbide waste and its possibility of using in new cementitious recipes. Paper is focused on importance of creation of grain curves and on relationship between silicon carbide and compounds in concrete matrix. Purpose of this research is using waste material and therefore minimalizes of its production and reduces ecological effect on environment by its recycling. Set of granulometry measurements of each recycled materials were done as well as its grain characteristic. The End of work includes the evaluation of the possible use of SiC waste for cement mixtures.
Abstract: A negative hygroscopic expansion (NHE) material contracts with the absorption of moisture. This paper introduces an NHE microstructure based on a truss-like lattice system that consists of two types of conventional materials, namely the apex and base rods connected by hinge joints. Based on the analytical model for volumetric strains, NHE is attainable by controlling the dimensions, coefficients of hygroscopic expansion and the changes in the hygroscopic concentration in the apex and base rods. For the special case where the apex rods are rigid, NHE is attainable if the apex-to-base rod length ratio is less than 0.707; if the apex-to-base rod length ratio is greater than 0.707, NHE is still attainable if the base rod’s hygroscopic strain is sufficiently large. NHE materials and structures are envisaged to play an important role for countering the effects of thermal expansion so as to decrease the extent of hygro-thermal stresses and/or strains. As such, further investigations on NHE materials are recommended to facilitate design principles that minimizes stress and/or strains in extreme hygro-thermal environment.
Abstract: In this paper, the results of the structural analysis of glued laminated timber and its joints in corrosive environment are shown. This paper includes calculation results for dowel connections of wood structures using steel and carbon fibres cylindrical dowel pins in accordance with the applicable regulatory documents by means of finite element analysis in ANSYS software, as well as experimental findings.
Abstract: Asphalt mixture is a kind of a viscoelastic material with viscoelastic characteristic of time-temperature equivalence. This paper, from the engineering practical consideration, and the perspective of time-temperature equivalence principle, based on the Rutting Test of Asphalt Mixture,has obtained equivalence relations of the effect of wheel speed and temperature on asphalt mixture rut index by different wheel speed and different temperatures rutting test, so as to provide the data support for the research of anti-rutting mechanism of asphalt pavement.