The effect of nanosilica addition on flowability, strength and transport properties of ultra high performance concrete

• Published in: Materials in engineering Vol. 59; pp. 1 - 9
• Main Authors: Ghafari, Ehsan, Costa, Hugo, Júlio, Eduardo, Portugal, António, Durães, Luisa
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.07.2014
• Subjects: Cements; Compressive strength; Concretes; Microstructure; Nanosilica; Nanostructure; Pastes; Porosity; Pozzolanic reactivity; Scanning electron microscopy; Transport properties; Ultra high performance concrete; Ultra high performance concrete; Transport properties; Microstructure; Nanosilica; Pozzolanic reactivity
• ISSN: 0261-3069
• DOI: 10.1016/j.matdes.2014.02.051

The experimental study herein presented was conducted aiming to evaluate the influence of nanosilica (nS) addition on properties of ultra-high performance concrete (UHPC). Thermo gravimetric analysis results indicated that nS consumes much more Ca(OH)2 as compared to silica fume, specifically at the early ages. Mercury intrusion porosimetry measurements proved that the addition of nS particles leads to reduction of capillary pores. Scanning electron microscope observation revealed that the inclusion of nS can also efficiently improve the interfacial transition zone between the aggregates and the binding paste. The addition of nS also resulted in an enhancement in compressive strength as well as in transport properties of UHPC. The optimum amount of cement replacement by nS in cement paste to achieve the best performance was 3 wt.%. However, the improper dispersion of nS was found as a deterrent factor to introduce higher percentage of nS into the cement paste. •We studied the influence of nanosilica addition on the properties of UHPC.•The addition of nS into cement paste can increase the amount of hydration products.•The water demand in the mixtures increased depending on the percentage of replacement.•Compressive strength of UHPC mixtures increased with the increase of nS content.•The addition of nS particles leads to a reduction of capillary pores.