Proper curing ensures that concrete meets the intended structural and durability requirements. A poorly cured concrete may result in development of early-age cracks due to reduction of internal relative humidity. Self-curing is one of the most effective curing techniques that are used in the modern construction industry. Many studies have shown that buildings are a significant contributor to natural resources depletion and environmental emissions. Demolished concrete from buildings has become a great concern in terms of waste disposal. After applying proper recycling techniques, it can be used as an alternative source for normal coarse aggregate which not only will help resolve waste disposal issues but also provide a solution for the short supply of normal coarse aggregate for concrete. This research makes an attempt to investigate the performance of self-curing concrete with recycled coarse aggregate by evaluating its structural properties in terms of compressive strength, split tensile strength and flexure strength. The comparative results show that recycled coarse aggregate achieves up to 94.82% of the normal aggregate compressive strength with normal curing and 91.73% normal aggregate when self-curing agent is used. A compressive strength increase of 3% was observed between normal curing and self-curing specimens with recycled coarse aggregate. It is also seen that an average structural performance decrease of 13% is recorded for self-curing test specimens when the aggregate is changed from normal to recycle.
High performance concrete (HPC) offers several advantages over normal-strength concrete, namely, high mechanical strength and high durability. Therefore, HPC allows for concrete structures with less steel reinforcement and a longer service life, both of which are crucial issues in the eco-efficiency of construction materials. Nevertheless international publications on the field of concrete containing nanoparticles are scarce when compared to Portland cement concrete (around 1%) of the total international publications. HPC nanoparticle-based publications are even scarcer. This article presents the results of an experimental investigation on the mechanical properties and durability of HPC based on nano-TiO 2 and fly ash. The durability performance was assessed by means of water absorption by immersion, water absorption by capillarity, ultrasonic pulse velocity, electric resistivity, chloride diffusion and resistance to sulphuric acid attack. The results show that the concretes containing an increased content of nano-TiO 2 show decreased durability performance. The results also show that concrete with 1% nano-TiO2 and 30% fly ash as Portland cement replacement show a high mechanical strength (C55/C67) and a high durability. However, it should be noted that the cost of nano-TiO 2 is responsible for a severe increase in the cost of concrete mixtures.
This paper discusses both experimental and analytical investigations for evaluation of the performance of the fiber reinforced polymer composites (FRPC) rehabilitated reinforced concrete (RC) beam-column joints subjected to cyclic loading. For experimental investigations, two types of beam-column joint specimens, with ductile and brittle reinforcement detailing are cast and investigated in this study. The joint specimens are subjected to the cyclic displacements of increasing amplitude until failure. Post failure, the joint specimens are rehabilitated using the FRPC. The rehabbed joint specimens are then subjected to the similar regime of cyclic displacements until failure. Salient details of the procedures for preparation and investigation of both control and rehabbed joint specimens are discussed in this paper. Performances of joint specimens are recorded in the form of the load-displacement plots. Comparisons between performances of control and rehabbed joint specimens highlight the efficiency of the discussed rehabilitation scheme in enhancement of strength, ductility, and deformability of the RC beam-column joints. In analytical investigations, the load-displacement relationships for both control and rehabbed joints are modeled in the form of the multi-scale models which consider stiffness degradation under cyclic loading. Accordingly, this paper also reports brief discussion on the stepwise development of the analytical models for performance of the materials; the cross-section; and that of the joints. Good agreement between experimentally observed and analytically modeled load-displacement relations facilitates validation of the analytical models, which then provides useful means for field applications of the FRPC in rehabilitation of RC beam-column joints.
First phase (overall design) for the design of a new, traditionally built Hindu temple in the Hoysala style of the 12th century.
