Micro and Nano Engineered High Volume Ultrafine Fly Ash Cement Composite with and without Additives

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Title: Micro and Nano Engineered High Volume Ultrafine Fly Ash Cement Composite with and without Additives

Author(s): R. Roychand, S. De Silva, D. Law, and S. Setunge

Publication: IJCSM

Volume: 10

Issue: 1

Appears on pages(s): 113–124

Keywords: nano silica, silica fume, fly ash, additives, X-ray diffraction, scanning electron microscopy

Date: 3/31/2016

Abstract:
This paper presents the effect of silica fume and nano silica, used individually and in combination with the setaccelerator and/or hydrated lime, on the properties of class F high volume ultra fine fly ash (HV-UFFA) cement composites,replacing 80 % of cement (OPC). Compressive strength test along with thermogravimetric analysis, X-ray diffraction and scanningelectron microscopy were undertaken to study the effect of various elements on the physico-chemical behaviour of the blendedcomposites. The results show that silica fume when used in combination with the set accelerator and hydrated lime in HV-UFFAcement mortar, improves its 7 and 28 day strength by 273 and 413 %, respectively, compared to the binary blended cement fly ashmortar. On the contrary, when nano silica is used in combination with set accelerator and hydrated lime in HV-UFFA cementmortar, the disjoining pressure in conjunction with the self-desiccation effect induces high early age micro cracking, resulting inhindering the development of compressive strength. However, when nano silica is used without the additives, it improves the 7 and28 day strengths of HV-UFFA cement mortar by 918 and 567 %, respectively and the compressive strengths are comparable to thatof OPC.


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