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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

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For the first time, the hydrophilicity of hemp shiv was modified without the compromise of its hygroscopic properties. This research focused on the use of sol-gel method in preparation of coatings on the natural plant material, hemp shiv, that has growing potential in the construction industry as a thermal insulator. The sol-gel coatings were produced by cohydrolysis and polycondensation of tetraethyl orthosilicate (TEOS) using an acidic catalyst. Methyltriethoxysilane (MTES) was added as the hydrophobic precursor to provide water resistance to the bio-based material. Scanning electron microscopy (SEM) and focused ion beam (FIB) have been used to determine the morphological changes on the surface as well as within the hemp shiv. It was found that the sol-gel coatings caused a reduction in water uptake but did not strongly influence the moisture sorption behaviour of hemp shiv. Fourier transformed infrared (FTIR) spectroscopy shows that the coating layer on hemp shiv acts a shield, thereby lowering peak intensity in the wavelength range 1200-1800 cm −1 . The sol-gel coating affected pore size distribution and cumulative pore volume of the shiv resulting in tailored porosity. The overall porosity of shiv decreased with a refinement in diameter of the larger pores. Thermal analysis was performed using TGA and stability of coated and uncoated hemp shiv have been evaluated. Hemp shiv modified with sol-gel coating can potentially develop sustainable heat insulating composites with better hygrothermal properties. A novel method for modification of hemp shiv using sol-gel technology. Graphical Abstract• Coating layer acts as a breathable membrane allowing the hemp shiv to retain its hygric characteristics.• Hemp shiv coated with sol-gel monolayer reduces its water absorption capacity by 200%.• The effects of sol-gel coating on surface morphology, thermal stability and porosity of the shiv increase with increase in coating thickness.

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