In this research work, the mechanical properties of high-strength self-compacting concrete (HSSCC) were studied. Three mixes were selected, having compressive strengths of more than 70, 80, and 90 MPa, respectively. For these three mixes, the stress–strain characteristics were studied by casting cylinders. It was observed during the testing that the binder content and water-to-binder ratio influence the strength of HSSCC, and slow changes in stress–strain curves were seen as the strength increased. The use of HSSCC results in reduced bond cracking, leading to a more linear and steeper stress–strain curve in the ascending branches as the strength of the concrete increases. Elastic properties such as modulus of elasticity and Poisson’s ratio of HSSCC were calculated using experimental data. In HSSCC, since the aggregate content is lower and the size of the aggregates is smaller, it will have a lower modulus of elasticity compared to normal vibrating concrete (NVC). Thus, an equation is proposed from the experimental results for predicting the modulus of elasticity of HSSCC. The results suggest that the proposed equation for predicting the elastic modulus of HSSCC for strengths ranging from 70 to 90 MPa is valid. It was also observed that the Poisson’s ratio values for all three mixes of HSSCC were found to be lower than the typical value for NVC, indicating a higher degree of stiffness.

This paper reviews the research carried on effects of fire on the mechanical and thermal properties on concrete. Fire in the structure causes higher temperature at the concrete surface, which causes a reduction in compressive strength, modulus of elasticity of concrete. Though concrete is a poorer conductor than steel, sustained high temperature at the surface leads to progressive heating of the inner layers of concrete. This leads to exposing reinforcing bars to higher temperature; which causes a reduction in the yield stress, ductility and tensile strength of steel. This paper also focuses on the concrete cover, the reinforcement bars in a concrete structure are protected against fire only by the concrete cover layer thus higher is the cover more is the resistance and vice a versa. Effects of temperature on the thermal conductivity of concrete is also discussed in detail.

The durability of concrete subjected to an aggressive environment is a major issue faced by constructional engineers. Many researchers have tried to evaluate the durability characteristics of concrete against aggressive fluids. Amongst the fluids, compounds of sulphuric acid and chloride ions caused massive deterioration in concrete. Reactive powder concrete (RPC) is a type of ultra-high-strength cement composite. In the present study, an effort is made to assess durability properties of RPC. The RPC with compressive strengths 110, 120 and 130MPa have been produced. Acid immersion test, salt crystallization test and chloride ion penetration tests have been carried out to assess the degradation of concrete. Samples were exposed to sulphuric acid solutions over a period of 60 days with concentrations varying from 0.5-2%. The salt crystallization tests were carried out by immersing samples in 14% Na2SO4 solutions. Visual observations and deterioration in terms of mass and compressive strength reductions are recorded. The RPC showed high resistance towards the crystallization of salts. A significant amount of weight loss and strength loss was observed for the samples exposed to high concentrations of sulphuric acid. A negligible amount of chloride ion penetration was observed.

Most of the existing codes are using stress block parameters which were derived for normal strength concrete. Rectangular stress-block parameters used for normal strength concrete cannot be used safely for higher grade concrete like HPC, hence new stress-block parameters are established from the experimental investigations. Theses parameters can be made very much useful in the design of HPC members. Present research aims at behaviour study of HPC using stress block parameters. High performance concrete single span beams were tested under monotonic four-point bending. Considering the experimental stress-strain curves of HPC for grade 60, 80 and 100 MPa, an idealized stress block curve is established and the stress block parameters are derived. Based on the idealized stress block curve, the equations for ultimate moment of resistance, depth of neutral axis, limiting moment of resistance and maximum depth of neutral axis are proposed. Based on the observation of experimental load deformation curves, an ideal load deformation curve is proposed, which follows four significant events identified as, first cracking, yielding of reinforced steel, crushing of concrete with spalling of cover and ultimate failure. The predicted values compare well with the experimental values. The average location of the first crack observed was at 0.535 times the span of the beam from the left support of the observer in the tension zone.