The use of rubber in self-compacting concrete is gaining more attention from the point of view of improved engineering properties of the product and also sustainability. Although several attempts have been reported on the utilization of crumb rubber for the replacement of coarse aggregate in conventional concrete and to some extent in self-compacting concrete, limited information is only available on the use of rubber as replacement for fine aggregate. This article mainly deals with the development of self-compacting concrete with varying proportions of powdered rubber as filler (fine aggregate replacement). The self-compactability characteristics and the engineering properties of self-compacting rubberized concrete mixes with varying compressive strengths have been experimentally evaluated. The experimental values have been compared with those of conventional rubberized concrete available from the past studies. The results indicate that self-compacting rubberized concrete has better engineering properties, which are most desirable for structural purposes, in comparison with conventional concrete with and without rubber.
Under fatigue loading, concrete like quasi-brittle materials exhibit softening behaviour since an inelastic zone will be formed in front of the crack tip called the fracture process zone (FPZ). There are various toughening mechanisms that exhibiting in this region. Current design practices for reinforced concrete assumes a zero tensile strength for concrete which is actually overly conservative. In fact, concrete can bear significant tensile stress and strain. Therefore, the tension softening response of RC member should consider in the study. Under fatigue loading, strength and stiffness decrease progressively according to the maximum amplitude and the number of cycles of loading. Fracture plays an important role in failure of normally and lightly reinforced beam. Since FPZ mechanisms and fibre bridging action resist crack propagation, we have to consider these mechanisms while assessing remaining life of RC member. Fatigue failure occurs when applied load is much less than the moment capacity. Such structures susceptible to fatigue load need to be monitored and residual life is to be predicted. This paper is presenting a review on the residual strength assessment on plain and reinforced concrete. The review includes the influence of various tension-softening models in predicting the residual life of plain and reinforced concrete. A comparative study is also conducted in order to assess the residual life by considering various tension softening laws.
Aggregates generally occupy 60% to 75% of the concrete volume and strongly influence the fresh and hardened properties and economy of concrete. The continued extraction of aggregates from nature has caused its depletion at an alarming rate. The worldwide depletion of natural resources and the simultaneous accumulation of waste materials call for the need for sustainable development in the construction industry. Hence, recent researches have been focussed on the use of locally available waste materials such as coconut shell, plastic, etc., in concrete to replace the mineral aggregates. This study deals with the strength characteristics of PET fibre reinforced coconut shell concrete (PFRCSC). Earlier studies have shown that when coconut shell was used in concrete to replace the coarse aggregates, compressive strength was decreased considerably. But, this reduction in strength was significantly low for 10% coarse aggregate replacement. Also, the inclusion of polythene fibres made from waste plastic bottles was noted to improve the strength characteristics of concrete. Hence, an attempt has been made to combine the positive characteristics of both coconut shell concrete (CSC) and PET Concrete. M30 normal concrete and CSC concrete with 10% coarse aggregate of normal concrete replaced by coconut shell has been taken as thecontrol mixes. PET fibres made from waste plastic bottles were added at volume fractions of 0, 0.5, 1, 1.5 and 2%. The mechanical properties such as density, compressive strength, tensile strengthand flexural strength were determined and compared with the control mixes. The experimental investigations were carried out on a total of 180 specimens which includes cubes, cylinders and prisms. The results indicate that PFRCSC is a sustainable, eco-friendly and economical concrete with better engineering properties and strength characteristics in comparison with normal concrete and coconut shell concrete.
Structural insulated panels (SIPs) made by sandwiching an insulating material from both sides have been used in buildings to enhance thermal resistance without loss in structural integrity. New innovations to improve its compositeness are also being explored. One method is to use shear connector made of high thermal resistant and ductile materials. This connects two outer wythes through insulation layer. The outer material can be of any type of high compressive strength concrete. These are usually reinforced with steel or carbon or glass fiber. The use of light weight and high strength materials helps to reduce the overall thickness of the structure. As the material of shear connector acts as a thermal bridge across the outer wythes, materials with low U value (thermal transmittance) are preferred. In this paper, an attempt has been made to carry out a comparative study on the performance of SIPs with shear connectors manufactured using different materials.
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