Papers by Keyword: Concrete

Abstract: With the study of frost resistance of plain concrete and mixed concrete with fly-ash substituted and mixed concrete with fly-ash substituted and nanoSiO₂ as admixture, the outcomes of the test go that the frost resistance of concrete with nanoSiO₂ will be increased considerably.

Abstract: Combining use electrochemical measurement and weight loss testing, the inhibition efficiency of an organic inhibitor was studied in a chloride contaminated solution. The results showed that the added inhibitor can enhance the corrosion potential and decreased the corrosion current density of rebar. The weight loss testing confirmed that the inhibitor reduced the corrosion rate of rebar by 80% in the chloride containing solution. Moreover, the linear polarization results are consistent with the weight loss testing, which suggests that the former is an effective method to estimate the inhibition efficiency of inhibitors.

Abstract: The degradation of the connection between shear studs and concrete is a complicated phenomenon that depends on many factors, including; interfacial properties, concrete crushing and steel yielding. The purpose of this paper is to outline the scope and methodology of the research project being undertaken to characterise the shear stud-concrete interface of a composite beam using finite element analysis. A mesoscopic model will be created for a section of the interface. With the use of a multi-scale approach, the mesoscopic model will be incorporated into a global model. The influence of steel roughness and mechanical properties will be included. Concrete is to be modelled as heterogeneous, comprising discrete regions of aggregate, cement matrix, and an interfacial transition zone (ITZ). The effect of the ITZ will be taken into account using a zero thickness cohesive element. Experimental testing using a push-up rig is to be conducted to verify the numerical models. The ultimate aim is to develop a simplified representation of the shear stud-concrete interface that can be used in a large scale finite element model of a composite member to correctly capture the behaviour of the shear stud-concrete interface in the elastic and inelastic state.

Abstract: As part of an ongoing research project into the numerical prediction of high temperature hygral processes in concrete and fire induced spalling, a fully coupled hygro-thermal model has been formulated for predicting the behaviour of concrete at high temperatures. The hygro-thermal model is a mathematical model for predicting the behaviour of concrete at high temperatures, treating the concrete as a multi-phase semi-saturated porous material. A numerical simulation of a one-dimensional heating experiment performed on an unreinforced concrete slab is presented, demonstrating the effectiveness of the model. A brief discussion of the main hygral processes is presented, in addition to a discussion of numerical challenges arising from the numerical implementation.

Abstract: This paper presents a comparison of available numerical structural formulations for the short-and long-term analysis of composite beams with partial shear interaction. Four methods of analysis are considered and these include the finite difference method, the finite element method, the direct stiffness method and the exact analytical model. The results obtained using these formulations are compared qualitatively and their accuracy is estimated, adopting the exact analytical model as a benchmark reference with the objective of establishing the minimum spatial discretisations required to keep the error within an acceptable tolerance. These comparisons are carried out for two static configurations, i.e. simply-supported beams and propped cantilevers, from which the qualitative behaviour of these formulations in the modelling of continuous beams can also be deduced.

Abstract: This study presents use of an approach which links the Latin Hypercube technique with Crank-Nicolson based finite difference approach for probabilistic assessment of chloride diffusion through silane-treated concrete. There are six random variables; (1) surface chloride, (2) diffusion coefficient, (3) first application time, (4) subsequent application time, (5) effective duration, and (6) cost of silane treatment. By different application times, three repair strategies are proposed. With silane treatment, the diffusion of chloride ions in silane-treated zone is retarded leading to the extension of the time which the chloride content at a threshold depth reaches the critical value of rebar corrosion and concrete cracking. Based on this extension, the time-dependent risk of rebar corrosion and concrete cracking is defined, and the time-dependent ratio of cumulative cost of silane treatment to benefit (percent reduction of the risk) is calculated. And, the best strategy based on the ratio of cost to benefit is justified.

Abstract: It is of great importance to innocuity, minimization and reutilization of manganese slag generated in manganese products by electric furnace process. In the paper, ordinary Portland cement is replaced by manganese slag part then to evaluate manganese slag's influence on the mechanical properties. The experimental results obtained show that ordinary Portland cement added less than 20% by manganese slag was improved in mechanical performances and the cement concrete added less than 20% by manganese slag was not changed significantly. To reduce the economic costs, enhance mechanical properties, manganese slag can replace part of cement concrete.

Abstract: In todays world, pollution is one of the most critical and acute problems resulted by human civilization which threatens the cycle and system of life, and nowadays, pollution of the environment is not an isolated problem which a special country is concerned with. The pollutant molecule that enters the environment in Europe can reach the lungs of people living in the heart of jungles in Africa or in vast plains in Asia. One of the pollutant industries which heavily affect the environment is the industry of Portland cement production. In the process of producing cement, different kinds of pollutants including Carbon Dioxide go into the environment, and as a result, this industry stands above the majority of industries regarding the pollutant emission rate. If the number of construction projects is considered as an indicator of every countrys development, the considerable use of concrete in projects carried out in developing and developed countries, and the accelerating competition of these countries for development lead to the rapid growth in use of concrete whose main material is Portland cement, and this trend results in intensifying the effects of pollutants on the environment. As concrete should be produced to the extent needed for use, and as the concrete consumption is growing, the production of cement should be increased, and this leads to a greater cycle of pollution. Thus, as prevention is considered one of the best ways to fight pollution, with conservation of cement in concrete, not only isnt any disturbance caused in development trend, but also the cost of projects will be reduced, and due to the reduction in cement consumption, countries can benefit from sustainable development, adjust the production of cement and lower the pollution caused by cement production, and as a result, reach green environment more easily. In the present article, the effect of Portland cement production in polluting the environment as well as the conservation of cement in Iran was studied and the results were reported.

Abstract: Nanotechnology can be used for design and construction processes in many areas since nanotechnology generated products have many unique characteristics. These characteristics can significantly fix current construction problems, and may change the requirement and organization of the construction process. This paper reviews the basic concept of nanotechnology, different types of nanomaterial and their manufacturing process as well as the applications of nanotechnology in different fields such as concrete, pavement engineering, construction materials. Use of nanotechnology is found to offer high performing and efficient materials. Specific application areas include water and waste water treatment, construction materials etc. The use of nanotechnology in civil engineering is still in infancy stage. The production methods, pollutions caused to human health, manufacturing difficulties, performance are the issues to be addressed in order to use the nanotechnology in civil engineering.

Abstract: In order to find the reason of concrete cracking in some construction. The mechanical property and micro-analysis of cores were tested, which drilled from cracked concrete floor. The test results indicated that alkali–aggregate reaction occurred, leading to the cracks in concrete floor. X-ray diffraction and scanning electron microscope facilitate the occurrence analysis and evaluation of cracked concrete.