Journal Mar 2019

Numerical investigations on compressive behavior of concrete at meso-scale M.V. Sukesh, Saptarshi Sasmal

In this paper, a methodology is proposed for simulation of non-linear behavior of concrete at meso-scale by incorporating heterogeneity. The geometrical models of concrete are generated using randomly sized aggregates. Load transfer mechanism, stress distribution and crack formation of the heterogeneous concrete with different aggregate volume fraction are studied by using the special elements to capture
cracking/crushing of concrete. Load-deformation behaviour of the heterogeneous concrete cells is also investigated. It is observed that as the volume percentage of aggregates is increased, maximum load withstood by the cell decreases, i.e. strength decreases as the volume percentage of aggregates increases. It is to mention that there is a total drop of 16% in the strength with increase of volume percentage of aggregates from 20 to 40. It is also noted that the elastic modulus is increased with increase in the volume percentage of aggregates even
though the strength monotonically decreases. There is a total increase of 25% of elastic modulus when the volume percentage of aggregates is changed from 20 to 40. The study will be helpful for understanding and describing the engineering properties of cement based systems and will facilitate to analytically evaluate the behavior of heterogeneous composites.

Influence of fly ash on mechanical and transport properties of concrete and mortar due to its effect on the interfacial transition zone Meenakshi Sharma, Bhavya Parashar, Shashank Bishnoi

Supplementary cementitious materials reduce the clinker factor in concrete. These mineral additives can vary in particle sizes (fine to ultrafine) and can influence mechanical properties and durability of concrete to a great extent. Durability of concrete depends on its intrinsic transport properties which further depend on the Interfacial Transition Zone (ITZ) present around aggregates. Available experimental investigations on the effect of fly ash on transport properties of concrete and mortar appear to be ambiguous, ranging from deleterious to enhancing effects to varying degrees. The present study examines the influence of fly ash on transport and mechanical properties of mortar and concrete to understand its influence on ITZ. Mortar and concrete having same aggregate volume fraction and water/cement ratio were tested for compressive strength, elastic modulus, oxygen permeability and sorptivity: variables include fly ash of different fineness with different percentage replacement. Same volume fraction of aggregates in mortar and concrete leads to a higher
ITZ volume in mortar due to finer particle size distribution of aggregates. The strength and elastic modulus results shows that fly ash improves the mechanical properties of mortar more compared to concrete. The decrease in the fluid transport was also found more for mortar compared to concrete. This suggests that fly ash significantly improves the interfacial transition zone around aggregates. The improvement was found to increase with increasing fly ash fineness.

Experimental studies on developed PZT based coating under fire exposure Ankur Achnani, Sharadkumar Purohit, Urmil V Dave

In the present paper, a fire retardant coating using Piezoelectric (PZT) Powder is developed to protect the substrate against detrimental effects of the fire. An experimental study has been carried out over two different substrate materials exposed to temperature up to 1300°C at the instant through oxyacetylene flame and temperature to 500°C through oven. An escape time about 2 times and surface temperature drop of 50°C have been observed for PZT coated substrate vis-a-vis bare substrate. PZT coating is tested for Flammability (UL 94) and for Optical
Density of Smoke (ASTM E 662) at NABL accredited laboratory establishes developed coating as fire retardant coating.

Performance of fly ash based geopolymer concrete under ambient and oven curing conditions M. V Krishna Rao, P. Rathish Kumar, T. Seshadri Sekhar

This paper addresses the effect of Sodium hydroxide (NaOH) concentration and curing type on strength and durability characteristics of low calcium fly ash-based Geopolymer Concrete (GPC). Test results indicate that the workability decreased and strength improved with increasing concentration of NaOH in Geopolymer Concrete specimens. Hot oven cured concrete specimens exhibited better compressive strength as compared to those of ambient curing. Exposure of Geopolymer Concrete specimens to acidic and sulphate environments suffered loss of weight and compressive strength up to 3.5% and 14% respectively. Results signified that hot oven cured
Geopolymer Concrete is highly resistant to water sorption, chloride ion penetration, and also to acid and sulphate attacks.

An experimental investigation on flexural behaviour of reinforced Self-Compacting Concrete beams at elevated temperatures N. Suresh, Sachin B. P.

This paper deals with the effect on mechanical properties of Self-Compacting Concrete (SCC) subjected to sustained elevated temperature. Experimental investigations were carried to find the behavior of Self Compacting Concrete for compressive strength, split tensile strength and flexural behavior. The experimental program was carried on cubes, cylinders and reinforced beams to study the effect of sustained elevated temperature on SCC. The specimens were subjected to elevated temperature between a range of 100ºC to 600ºC at an interval of 100ºC for a period of 2 hours. The observations shows that there is an increase in compressive strength up to 300ºC and found to decrease beyond this temperature. It is also been observed that tensile strength and load carrying capacity of the beam is inversely proportional to the temperature.

Potential of electrical response at low Radio Frequencies for estimation of the degree of moisture saturation in cement mortar Gopinandan Dey, Abhijit Ganguli, Bishwajit Bhattacharjee, Tapan Kumar Gandhi

In this paper, the electrical response of cement mortar samples under different Degrees of Saturation (DoS) is examined at Radio frequencies (RF), varying from100 kHz to 300 kHz. A new technique of measurement of the DoS is proposed for mortar samples. The electrical responses in terms of the complex ratio between the output and input voltages, measured at various DoS, are found to follow a systematic pattern. An angular parameter corresponding to the complex voltage ratio is presented as an empirical measure of the DoS.

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