Abstract: In order to achieve the penetration method which could reflect the high temperature property of SBS modified asphalt, the paper presented the penetration test of SBS modified asphalt with different types and dosages of SBS modifier at three kinds of penetration weight and four different temperatures. Meanwhile, the high temperature performance of the SBS modified asphalt mixture was studied. It was found that penetration measured under current specification method (25oC, 100g, 5s) could not identify the difference of viscosity and high temperature property of different SBS modified asphalt. When the test conditions are revised to “penetration weight of 150 g, test temperature of 30oC, penetration time of 5s”, the penetration of different SBS modified asphalt measured by revised method could be used to evaluate the temperature susceptibility of SBS modified asphalt accurately and are closely related to the dynamic stability of mixture.
Abstract: Cement industry is responsible of 5-7% of CO2 emissions to the atmosphere. This is preoccupant because this is one of the greenhouse effect gases which cause global warming. Pozzolanic material incorporation in cement mortars elaboration represents a good alternative to partially substitute cement, since its chemical composition could contribute to improvement of its durability and mechanical characteristics. In this research, mortars with pozzolanic substitutions are evaluated through non-destructive tests as: capillary absorption, electrical resistivity, and ultrasonic pulse velocity to the age of 1000 days. The results suggested that the incorporation of pozzolanic material as partial substitutes of Portland cement increases the mortars properties mainly in substitutions of CBC 20%, PN 10, and 30%.
Abstract: Article presents quality evaluation system for description of recycled concrete aggregates (RCA), verification of RCA properties and subsequent application in to concrete mixtures as a partial or total replacement of natural aggregates (NA). Modernization and rehabilitation of constructions is accompanied by creation of demolition waste from old buildings and structures. The necessity of recycling is unavoidable, because volume of construction and demolition waste (C&DW) is increasing and the landfills are reaching their maximum capacity. Nowadays, there are numerous research teams focused on analysis of characteristics and application of RCA into new concrete as a replacement of NA. Test samples of RCA have always different source, grain composition and other physical and mechanical properties, which are variously described in each different paper. Up to now, there is no any uniform quality evaluation system for description of recycled concrete aggregates, which can easily describe their source and assumed properties. Our aim is to set up rules for description of RCA and simplify the evaluation of properties of various RCA. Qualification system will be applied on three different samples of RCA and verified by the selected properties tests. Tested samples of RCA will be than used as a replacement of natural aggregates in concrete mixtures. The replacement amount was set up on 20%, 40% and 100% according to the reviewed literature, to have a comparable replacement amount and valuable results for discussion. The results of RCA testing and testing of concrete with partial and total replacement of NA showed that the evaluation system is working properly. It can be concluded, that accuracy of the quality evaluation system for description of recycled concrete aggregates is sufficient, but more tests on RCA should be done to prove all connections in between description of RCA and their properties.
Abstract: The peculiarities of pultruded FRP profiles, i.e. low mass, durability and ease of construction, make them suitable for retrofitting traditional masonry structures, particularly in seismic areas. This could represent an effective solution, not yet sufficiently explored, that allows for non-invasive and reversible interventions, which improve the structural performance with a very small structural mass addition. The paper presents a FEM study on a hypothesis of retrofit of a traditional masonry building with pultruded FRP frame, adjacent to the masonry structure and connected to it with mechanical fasteners. The results appear promising and enlighten much increased in-plane strength and stiffness, as well as the change of the masonry failure mode into a more dissipative one.
Abstract: Residual parameters of Ultra High Performance Concrete (UHPC) exposed to high temperatures were experimentally accessed. The UHPC was provided by hybrid fibre reinforcement based on polyvinyl alcohol (PVA) and steel fibres. Among the studied material properties, bulk density, matrix density, total open porosity, pore size distribution, water vapour transmission and liquid water transport properties were examined. The UHPC samples were exposed to the temperatures 400 °C, 600 °C, 800 °C, and 1000 °C respectively. For comparative purposes, the reference UHPC samples cured at laboratory temperature were tested as well. Based on the obtained results, correlation between concrete structural changes and tested parameters was found out. The applied temperature load highly affected the concrete porosity, pore size, and thus both liquid and gaseous moisture transport parameters. Disintegration of concrete structure, colour change, cracking, damage of steel fibres (melting), and failure of their cohesion was apparent from optical microscopy analysis.
Abstract: Old reinforced concrete buildings constructed around 1980’s in many developing countries have been designed against mainly gravity load. Beam-column joints in these buildings contain slightly or no shear reinforcement inside the panel zones due to the construction convenience, and are vulnerable to shear failure in beam-column joints under the action of earthquake loads, especially for the exterior beam-column joints. This experimental study aimed to investigate the seismic performance of five half-scale exterior beam-column joints simulating the joints in existing reinforced-concrete buildings with non-shear hoop details. The test results showed that the structural performances of the beam-column joints under earthquake including failure mode, load-drift ratio relationship, shear strain of the joints and energy dissipation are strongly affected by the amount of longitudinal reinforcing bars of beams.
Abstract: This paper examines the impact of type of electrolyte solutions, standing time without electricity on the reinforced bond of the concrete of different water cement ratio before and after chloride extraction, processes the microscopic structure and mechanism analysis. The electrochemistry method can discharge the chlorine salt without destroying the original concrete protective layer and realize the non-loss, low cost and fast repair for the concrete structure destroyed by the chlorine salt corrosion. The results show a substantial loss of the reinforced bond (70-76%) after chloride extraction according to the concrete of different water cement ratio, and the decrease is in proportion to the current-on time and the electrochemical capacity of the electrolyte. The increased partial porosity of the cathode area of the concrete by the chlorine and hydrogen produced in the process of electrochemical chlorine extraction, the decomposition and softening of the concrete hydration products with external field are the main reasons for the dramatic drop of the reinforce bond.
Abstract: Nowadays, most of the infrastructure building has inside its structural elements stony material. Over the years, the rocks have been widely used in construction, as stony material in a ceramic or cement matrix, or as a structural element in historical buildings. Physical characteristics are determined as: the present Humidity, Absorption, Density, specific Gravity, and mechanics as uni-axial Compression Resistance, besides Capillary Suction. We obtained images with Scanning Electron Microscopy (SEM) and we compared the physical and mechanical proofs with microphotographs. These studies help a restorer to use the rocks wisely and with the conviction that the rock is appropriate for the goals searched. The stony materials are found in a material bank called Comanja in Michoacán, Mexico.
Abstract: This paper reports an experimental study on the use of waste plastics in stone mastic asphalt (SMA) for infrastructural applications (e.g. roads, carparks and underground construction). The binders investigated were conventional bitumen, target bitumen (polymer modified bitumen) and waste plastics (recycled low-density polyethylene LDPE of 5 wt% and 10 wt% blends). The properties of bitumen were assessed based on its penetration value and softening point; while the performance of asphalt premix (or asphalt mixture) was evaluated based on its Marshall stability, flow and quotient. The asphalt mixture incorporating waste plastics (10 wt% LDPE blend) as polymer modifier could be a promising material for use in SMA for infrastructural applications.