Dr.Yogesh Aggarwal, Assistant Professor, and S.Naveen Chander, Post Graduate Student, Department of Civil Engg. NIT Kurukshetra, Haryana.

Introduction

Lightweight concrete can be obtained either by replacing totally or partially standard aggregates by low weight aggregates or introducing gassing agents in concrete. The interest is not only to decrease the volume of load-bearing elements but also to get better thermal properties with regard to conventional concrete. Achieving both the thermal insulation and lightweight bearing structure with a material is an attractive idea. Virgin EPS beads is indeed such a material that can be easily incorporated with different contents in concrete to produce lightweight concrete with a wide range of densities as well with thermal insulation property. The mechanical properties of such a concrete is highly dependent on the amount of polystyrene aggregate in the mix. When the bead content increases, both the density and strength are significantly reduced. Babu and Babu [1,2] studied the strength and durability of EPS concrete containing mineral admixtures such as silica fume and fly ash with concrete densities varying from 550 to 2,200 kg/m3 and the corresponding strength results were found to vary from 1 to 24 MPa. Similarly, Sadrmomtazi et al. [3] investigated addition of silica fume and rice husk ash in combination with polypropyelene fibers to EPS concrete to obtain densities in the range of 900 to 1900 kg/m3 with compressive strengths varying from 3 to 33 MPa. While Xu et al. [4] confirmed legitimacy of the use of EPS lightweight bricks made by EPS lightweight aggregate concrete, it was observed that the mechanical properties could be improved by decreasing EPS sphere size. Miled et al. [5] developed a 2D numerical model to analyze such size effects. Till date, no attempt has been made to include ground granulated blast furnace slag (GGBS) as admixture in EPS concrete, so in the present study effect of GGBS on various properties in EPS concrete is analyzed. GGBS is obtained from slag, which is nothing but a waste product from both ferrous and nonferrous metal industries. Two processes govern slag's reaction rate during the initial period of hydration. The first is the nucleation and the growth rate of hydration phases. These compounds are then transformed into CSH gel. The second is the phase boundary interactions or the interactions that occur between the old compounds and the newly formed compounds. These compounds or hydrates are generally more gel-like in structure than the products of Portland cement. These hydrates add to the density of the cement paste. Also, the hydration of slag, in the presence of Portland cement, depends greatly upon the breakdown and dissolution of glassy slag structures by hydroxide anions (OH). This ion release occurs during the hydration of cement [6].

NBM&CW November 2014