Nanosilica and Microsilca in Concrete

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Introduction

Concrete is most widely used material for various applications in this world. India is second largest producer of concrete in world. As this is used in various applications its base properties which are obtained by preparing concrete with required raw materials must be enhanced by adding some other material to it. There comes the role of admixtures by which one can extract required property from concrete. There are various two basic classifications of admixtures. Chemical and Mineral admixture. There are various types of mineral admixtures. Most of mineral admixtures are by-products available from some production industry. Silica fume is a mineral admixture which is obtained as by-product of silicon industry is a costliest material but is very desirable material for normal concretes. Footprint of Nanotechnology which is defined as science of controlling the properties at nanometer scale which can make revolutionary changes in bulk material properties [23] in construction field has great impact in improving the properties of concrete . There are many types of nano-materials like nano-silica, nano-alumina, carbon tubes etc.. This paper describes how the properties of concrete are enhanced by adding nano-silica to it and compares with concrete containing microsilica. Both nano-silica and micro-silica are siliceous admixtures having higher contents of amorphous silica but nano-silica is the one having 1/10th size of silica-fume which is major advantage for nano-silica to enhance different properties of concrete to larger extent than microsilica.

Silica Fume

 It is by-product of silicon industry and contains very large amounts of amorphous silicondioxide (about 90%). (ACI-116R)[1]

 It is 100 times smaller than cem...

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...ay be due to reduced size and total volume of pores. Not much difference was found between addition of NS or MS to these concretes.[16]

Effect on self-compacted concrete

On addition of NS to self-compacted concrete one can observe reduction in bleeding, segregation and flowability. Experimental results showed improved compressive strength, split tensile strength and flexural strength. Higher electrical resistivity and resistance to chloride ion penetration was also observed in NS incorporated Self compacting concretes.[17][18]

Effect on rice husk ash concrete

Author observed that overall performance of concrete was increased and there is huge reduction in water absorption [19]

Effect on eco-concrete

Delayed setting and very low early strengths are major defects of eco-concrete which can be counteracted by incorporating NS into these concretes. [20]

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