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Reactive Powder Concrete (RPC) is an ultra-high strength concrete composite prepared by the replacement of natural aggregates with quartz powder, silica fume and steel fibers. The use of RPC yields high strength, high ductile concrete with optimized material use and contributes to economic, sustainable and ecofriendly constructions. Past research has indicated that RPC offers significant improvement in the mechanical and physical properties owing to its homogenous composition with less defects of voids and microcracks. This leads to enhancement of ultimate load capacity of RPC members and results in superior ductility, energy absorption, tensile strain-hardening behavior, crack control capability and durability. Geo-polymer concrete (GPC) is a type of concrete that is made by reacting aluminate and silicate bearing materials with a caustic activator. Usually, waste materials such as fly ash or slag from iron and metal production are used, which helps lead to a cleaner environment. This paper attempts to review the effect of steel fibers on the shear strength of steel fiber reinforced RPC and compare the results with those of geopolymer concrete.

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.

Many infrastructures like Bridge decks, airfield and highway pavements, offshore structure and machinery foundation are subjected to fatigue loading. This cyclic loading induces gradual, permanent internal changes in a material and thereby affecting the remaining life of the infrastructure. The heterogeneities in concrete add complexities in analysing fatigue failure of reinforced concrete. This review paper discuss about fatigue life prediction models for both plain and reinforced concrete structural member. This review paper comprises various deterministic and probabilistic models used in predicting the fatigue life of plain and reinforced concrete. Deterministic approach is dependent on some initial parameters and conditions and is unreliable to accurately determine the fatigue life of concrete. This results in the development of a more generalized model based on a probabilistic approach that accounts for the stochasticity in fatigue failure of concrete. In recent years, artificial neural network emerged as a new promising computational tool which adopts a probabilistic approach for modelling complex relationships.

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.

The effect of microcracks ahead of a macrocrack on the post-peak behavior of concrete-like quasi-brittle material is studied. The critical length of a microcrack is estimated by considering a small element near the macrocrack tip and defining the critical crack opening displacement of the microcrack that exist in the interface region between the aggregate and cement paste. A fracture model is proposed to predict the post-peak response of plain concrete. This model is validated using the experimental results for normal-strength, high-strength and self-consolidating concretes available in the literature. Through a sensitivity analysis, it is observed that the elastic modulus of concrete and the fracture toughness of the interface have a substantial influence on the critical microcrack length.

A linearized stress intensity factor (SIF) is derived for concrete through a multiscale approach by considering the predominant process zone mechanisms such as aggregate bridging and microcracking. This is achieved by considering a bridging zone and a microcrack at the macrocrack tip. The bridging zone resists the crack growth through aggregate bridging mechanism. The SIF thus derived is further used in developing an analytical model which predicts the entire crack growth curve for plain concrete by making use of the concepts of dimensional analysis and self similarity in conjunction with the human population growth model. This model is validated using experimental data reported on normal strength, high strength and self consolidating concrete. Through sensitivity analyses it is shown that the specimen size plays an important role in the fatigue crack growth process of concrete. (C) 2017 Elsevier Ltd. All rights reserved.

The fracture process of concrete is characterized by various toughening mechanisms that exist at the macro crack tip. In this study, the crack growth resistance due to the bridging of aggregates (defined as bridging stress) is evaluated by relating the crack opening displacements at the macroscopic scale to the mesoscopic one by considering the fracture toughness and the elastic modulus of the interface between the coarse aggregate and the mortar. The influence of specimen size and the stress ratio on the bridging stress is studied. The effect of the bridging stress on the fatigue crack growth rate is predicted and the results are found to agree well with the experiments for normal and micro concrete. The residual strength of a damaged beam is computed in terms of the moment carrying capacity by considering the bridging resistance offered by the coarse aggregates. (C) 2016 Elsevier Ltd. All rights reserved.