Sorptivity and acid resistance of ambient-cured geopolymer mortars containing nano-silica

Abstract

This study investigated the effects of nano-silica on flowability, strength development, sorptivity and acid resistance properties of fly ash geopolymer mortars cured at 20 o C. The changes in mass, compressive strength and microstructure of the specimens after immersion in acid solutions for different durations were determined. The microstructures were studied by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analysis. It was found that addition of nano-silica in geopolymer mortars based on fly ash alone or fly ash blended with 15% GGBFS or 10% OPC improved the compactness of microstructure by reducing porosity. Thus, the nano-silica reduced sorptivity and increased compressive strength of the mixes. The average mass loss after 90 days of immersion in acid solutions reduced from 6.0% to 1.9% by addition of 2% nano-silica.Similarly, significant reduction in strength loss after immersion in acid solution was observed in the specimens by using nano-silica.

Pore Structure Degradation of Different Cement Mortars Exposed to Sulphuric Acid

“…The largest variation occurred for the ethyl silicate mortar with an increase of 30.5 percentage points (pp) (increased from 8.6% at 28 days to 39.2% at 90 days), and the zinc stearate mortar was the least affected with an increase in mass loss of 16.8 points. These results are consistent with those obtained in other studies, where cementitious materials were seen to decrease mass with increase in exposure time [3,10,28].…”

“…In relation to those stored in optimallaboratory conditions (without attack), the lowest total porosity values were noted for the specimens with nanosilica. This result shows a slightly beneficial effect of this addition in terms of porosity, which agrees with another study in which nanosilica has been used [28]. The control and ethyl silicate specimens had practically the same total porosity when not exposed to the acid attack.…”

“…Mechanical strength tests are commonly used to evaluate the effects of chemical exposures on cementitious materials [26,28,29]. In this study, the compressive strength of the specimens was tested after 28 days of acid exposure (i.e., 56 days after their manufacture) and 90 days of exposure (118 days after their manufacture) for both control and treated mortars.…”

“…As with compressive strength, mass loss is also a parameter that is usually measured to assess the impact of aggressive environments on cementitious materials [25,28]. In this study, the specimens were weighed three times: (i) after 28 days of curing and before starting the sulphuric acid exposure; (ii) after 28 days of acid exposure (56 days from their manufacture), and (iii) after 90 days of exposure acid (118 days after their manufacture).…”

Effect of TiO2Nanoliquid on the Properties of Cement Mortar

“…Nano silica densify the matrix which was observed from SEM images. In the drying shrinkage the hydration rate was not effective due to the high volume replacement NimaFarzadnia et al [6].Sorptivity of the specimen was less when compared to that of the control specimen and the micro structure of the specimen with nano liquid was more compact when compared to control specimen ParthaSarathi Deb et al [7].Nano Silica andnano clay in wet and dry condition respectively have significant improvement on the compressive and flexural strength of high performance concrete. The addition of more amount of nano liquid reacted negatively towards the compressive and flexural strength Anwar M Mohamed [8].Nano silica improves the compressive strength and resistance to sulphate attack when compared to control mortar Saloma [9].…”