Effects of nanosilica on the calcium silicate hydrates in Portland cement–fly ash systems

Abstract

Effects of nanosilica on the calcium silicate hydrates in Portland cement-fly ash systems Calabria-Holley, Paine and Papatzani Effects of nanosilica on the calcium silicate hydrates in Portland cement-fly ash systems Cementitious materials have a complex chemistry and naturally form nanostructures in the hydration process, a network of calcium silicate hydrates. It is considered that nanoparticles such as nanosilica could act as a pozzolanic material as well as a seeding agent for nucleation and acceleration of the formation of the calcium silicate hydrate network. This work evaluates the effect of nanosilica on the calcium silicate hydrate network and microstructure of hardened ternary, quaternary and quinary system Portland cement based pastes. The quinary system, containing Portland cement, limestone, fly ash, microsilica and nanosilica, and ternary combinations (Portland cement, limestone and fly ash) showed mean calcium/silicon atomic ratios of the calcium silicate hydrate gel in the 28 d old hardened paste of 1 . 2 and 2 . 3 respectively. Fourier transform infrared spectroscopy results show the presence of the bridging silicate tetrahedra (Q 2 ) characteristic of a peak at around 980 cm 21 and a shoulder at around 1060 cm 21 in the calcium silicate hydrate gel network of the ternary, quaternary and quinary combinations; these bands are thus more pronounced for the nanosilica-enhanced formulations. The sample obtained in the presence of microsilica and nanosilica (quinary combination) showed evidence of a more intricate calcium silicate hydrate gel network (bridging tetrahedra) characteristic of a honeycomb-like structure opposed to the ternary combination (control sample). Advances in Cement Research Volume 27 Issue 4 Effects of nanosilica on the calcium silicate hydrates in Portland cement-fly ash systems Calabria-Holley, Paine and Papatzani Advances in Cement Research Volume 27 Issue 4 Effects of nanosilica on the calcium silicate hydrates in Portland cement-fly ash systems Calabria-Holley, Paine and Papatzani Advances in Cement Research Volume 27 Issue 4 Effects of nanosilica on the calcium silicate hydrates in Portland cement-fly ash systems Calabria-Holley, Paine and Papatzani Advances in Cement Research Volume 27 Issue 4 Effects of nanosilica on the calcium silicate hydrates in Portland cement-fly ash systems Calabria-Holley, Paine and Papatzani Advances in Cement Research Volume 27 Issue 4 Effects of nanosilica on the calcium silicate hydrates in Portland cement-fly ash systems Calabria-Holley, Paine and Papatzani Advances in Cement Research Volume 27 Issue 4Effects of nanosilica on the calcium silicate hydrates in Portland cement-fly ash systems

Polycarboxylate/nanosilica-modified quaternary cement formulations – enhancements and limitations

“…For the paste characterisation, arrest of hydration was performed following two different methodologies: solvent exchange and oven drying, as described by Calabria-Holley et al (2015). For the generation of SEM back-scattered images and the microstructural investigation, solvent exchange was the technique employed for the arrest of hydration.…”

A comprehensive review of the models on the nanostructure of calcium silicate hydrates

“…A whole new range of hybrid cements is evolving with the addition of a range of nanoparticles, mainly nano-SiO 2 [128][129][130][131][132], nano-TiO 2 [133], nano-montmorillonite clay [134,135], nano-Al 2 O 3 [136], nano-Fe 2 O 3 [137], by (i) improving particle packing, (ii) modifying particle size distributions, (iii) providing nucleation points for accelerated cement hydration, (iv) producing additional C-S-H, via enhanced pozzolanic reaction, reducing C/S ratio towards denser C-S-H. Moreover, the addition of totally new functions to concrete has become possible, such as photocatalytic characteristics with the incorporation of nano-TiO 2 particles [1].…”

Hydration Studies of Cementitious Material using Silica Nanoparticles

“…The IR spectra are in agreement with the interpretation through EDX also, that the addition of additives results in the formation of additional C-S-H gel, which could possess a low C/S ratio. According to the previous studies the additional C-S-H has more polymerised silica network with different characteristics, one of them being assigned to enhancement in durability (Holley et al 2014). The intensities of the 1413-1449cm -1 band of SNPs was smaller than that of the hydrated cement at 1d, suggesting the decrease in carbonation ratio (Fig.…”