ISSN 2319-5347, ISI Impact Factor: 0.763

VOLUME 03 NO. 02 APRIL 2014:

Title:        Alkali-activated binder systems for pavement quality concrete using dredged marine sand as fine aggregate
Authors:   Manjunatha S. B., Ravishankar A. U., and Narasimhan M. C.
Abstract:  Most of the aggregates used in the manufacture of concrete come from quarries or alluvial rivers. Now-a-days, these sources of natural aggregates are depleting fast and their extraction also has harmful consequences for the environment. For these reasons, it is important to optimize the consumption of natural aggregates as well as to enhance their replacement by other alternative sources. Increasing global emission of green-house gases like co2 associated with increasing use of Portland cement-based concrete mixes and problems associated with effective and safe disposal of industrial wastes such as fly-ash and Ground granulated blast furnace slag (GGBS) are two major areas of concern for modern communities. Development of structurally efficient, eco-friendly and economically cost-effective and eco-friendly alternative binder systems, with lower carbon foot-prints, using Fly-ash and GGBS is an area of current research focus. Increase in depletion of natural river sand has become a major issue to search for an alternative. The present paper is aimed at performance evaluation of pavement quality concrete (PQC) mixes developed by alkali activation of fly-ash and GGBS and Alkali activation of these source materials has been achieved using combination of Sodium hydroxide and Sodium silicate solutions. In addition possible use of coarse aggregates with 31.5 mm maximum aggregate size, with appropriate grading in developing PQC mixes and dredged marine sand as fine aggregate is
aimed at. Mechanical properties of such PQC mixes based on alkali-activated binders such as compressive strength, flexural strength, and modulus of elasticity have been evaluated in this study. Combined gradation of 31.5 mm & down-size coarse aggregate and dredged marine sand as fine aggregate has been achieved to satisfy the standard requirements such as Shilstone method, 0.45 power chart and workability-coarseness factor. In the alkali activator system, the ratio of Sodium hydroxide to Sodium silicate ratio as 2.5 is considered.The results show that the compressive strengths at all ages is considerably at par with control concrete with natural river
sand. The flexural strength at all ages are also almost matching the control mix. Other properties like modulus of elasticity have also been evaluated and found approximately same as control mix.

Keywords:   Fly-ash, GGBS, Alkali activators, Dredged marine sand
Page No:     194-201

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