C. Natarajan

Evaluation of residual strength and durability aspect of concrete cube exposed to elevated temperature

The study emphasis the effect of elevated temperature on concrete cubes made with M20, M25, and M30 concrete grades. The other variables considered were temperature (100, 200, 400, and 600 °C), duration of exposure (1-h and 2-h) and two types of cooling methods. The mass loss is varied from 0.52 to 6.56% for various temperature and duration of exposure. The mass loss increases as the duration of exposure increased. The porosity ranges from 9.89 to 44.34% and it depends on grade of concrete and exposed temperature. The strength loss ranges from 3% at 200 °C to 57% at 600 °C for air cooled specimen. In quench cooled specimen the loss in strength varies gradually up to 200 °C but at 400 °C the loss in strength was 42%, while the loss was only 32% for air cooled specimen. The obtained residual compressive strength curve from this study was compared with strength curves proposed by various codes.

Investigation of the Behaviour of Concrete Containing Waste Tire Crumb Rubber

In the concrete preparation 70–80 % occupying natural aggregates like crushed rock and river sand, the most commonly used coarse and fine aggregate is likely become scarcer the it is today. Now construction people need the alternatives to natural aggregates. Therefore, finding alternatives to naturally available materials is important to sustaining construction industry. On other hand a large quantity of waste materials are being produced by various industries and the governments are seeking ways to reduce the problem of disposal and to control the health hazard from the accumulation of waste materials. Some of the waste materials, such as coal fly ash, bottom ash, glass granules, plastic granules, copper slag, and crushed rock dust were used in the concrete. So in such waste materials are used to modify the mechanical and durability properties of concrete so as to make it suitable for any situation, this would also additional benefits in terms of reduction in cost, energy savings, promoting ecological balance and conservation of natural resources. In this study, the production of concrete was obtained by partially replacing the fine aggregate with crumb rubber. The main advantages of crumb rubber utilization in concrete to give the lower density, higher impact and toughness resistance, enhanced ductility, and better sound insulation etc. Crumb rubber is made by shredding waste tires. In the shredding process the steel wires are removed from the discard tires. The crumb rubber particle size ranging from 0.075 mm to not exceeding 4.75 mm, similar to the fine aggregates. Experimental investigations were carried out to study the behaviour of concrete with and without crumb rubber. The replacement of crumb rubber contents varying 5–25 % of river sand by volume. The test results indicated that the addition of waste tire crumb rubber substitution increases, the density, compressive strength and static modulus of elasticity was decreased. At the same time the flexural strength was increased up to 15 % of crumb rubber replacement. The relationship between static modulus of elasticity and flexural strength with compressive strength of concrete with and without crumb rubber was analyzed and compared the experimental results with the empirically calculated values by using design codes.

Impact Response of Paver Blocks with Waste Tyre Crumb Rubber

Waste materials utilisation has been a very important aspect in the concrete manufacturing to develop the green construction in the last decade. The disposal of waste tyres is one of the most problematic issues in the present scenario. The use of waste tyres in the concrete production is very important to control the waste accumulation and preserve the natural resources. The aim is to investigate the effect of partial replacement of sand by waste tyre crumb rubber in the production of concrete paver blocks. The specimens were prepared for 5, 10, 15, 20 and 25% replacements by volume for sand. M40 grade concrete was designed and used in this study. The paver blocks were prepared in the industry and tested in the laboratory to determine the impact resistance. The test results revealed that the impact resistance for both first crack and ultimate failure increased with an increase in the crumb rubber content up to 25%.

Effect of Fire on Reinforced Concrete Slab—Numerical Simulation

Buildings are often exposed to elevated temperature due to lack of fire safety, sabotages, etc. A recent survey about India’s risk says that fire has been rated among top three risks by most of sectors across India. The study investigates the influence of cooling condition on concrete slab exposed to fire. The variables considered for the study are thickness of slab 125 mm, retention period of one-hour and four-hour, subjected to temperature of 300, 400 and 500 °C, and two types of cooling regimes like air cooling and quench cooling. The slab which was exposed to temperature of 500 °C for four-hour duration had temperature of 143 °C at the unexposed surface which is marginally less than the allowable limit, but other slabs reveal good resistance to insulation. The reduction in flexural stiffness of concrete slab exposed to 500 °C for four-hour retention period was 28.67 and 37.89% for air cooled and quench-cooled specimens, respectively. The irrecoverable loss in flexural stiffness of concrete slab was influenced by the retention period, exposed temperature and cooling regimes.

Influence of Glass Fiber on Fresh and Hardened Properties of Self Compacting Concrete

The practical need of self-compacting concrete (SCC) is increasing due to increase in the infrastructure competence all over the world. The effective way of increasing the strength of concrete and enhance the behaviour under extreme loading (fire) is the keen interest. Glass fibers were added for five different of volume fractions (0%, 0.1%, 0.3%, 0.5% and 0.6%) to determine the optimum percentage of glass fiber without compensating the fresh properties and enhanced hardened properties of SCC concrete. The fresh state of concrete is characterized by slump flow, T-50cm slump flow, and V-funnel and L- box tests. The results obtained in fresh state are compared with the acceptance criteria of EFNARC specification. Concrete specimens were casted to evaluate the hardened properties such as compressive strength, split tensile strength, flexural strength and modulus of elasticity. Incorporation the glass fiber into SCC reduces the workability but within the standard specification. The hardened properties of SCC glass fiber reinforced concrete were enhanced, due to bridging the pre-existing micro cracks in concrete by glass fiber addition.

Behaviour of Two Way Reinforced Concrete Slab at Elevated Temperature

The reinforced concrete slabs have experienced significant levels of stressing and cracking as a result of restrained thermal deformations. However, for evaluating the thermal strains in the slab, temperature distribution of the slab is required. Temperature distribution of the reinforced concrete slab varies from point to point. The temperature of unexposed concrete slab also rises due to the adjacent slab which is exposed to fire, even though concrete is having significant resistance for the propagation of fire. In this study, temperature distribution over the surface of concrete slab is obtained using finite element computer program (ABAQUS). Two different cases are considered to estimate the heat propagation through slab. In the first case, slab is subjected to fire at its center region. In the second case, slab is subjected to fire at outer region means along the walls. Modelling is carried out to predict the temperature distribution and thermal strains of concrete slab. The other parameters considered for this study are varying thickness of slab (100 and 200 mm) and exposed temperature (100, 200, 300 and 400 °C). The duration of exposure considered for the study is 4 h.