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This study investigates the effects of Fe 3 O 4 and Fe 3 O 4 /SiO 2 nanoparticle admixtures on the behavior of cement mortars exposed to elevated temperatures. Pristine nanoparticles of magnetite (Fe 3 O 4 ) were coated with a solid silica shell (via the Stöber method), to form a core-shell nanostructure (Fe 3 O 4 /SiO 2 ). The cement mortars were incorporated with an optimized ratio of 3 wt% Fe 3 O 4 and 5 wt% of Fe 3 O 4 /SiO 2 admixture. The specimens were exposed to elevated temperatures of 200, 300, 450, 600 and 800 °C. After cooling, the mass loss and flexural and compressive strengths of the specimens were determined. The results demonstrated that the presence of magnetite-silica (Fe 3 O 4 /SiO 2 ) nanostructures is much more beneficial for improving the thermal resistance of cement mortars than pristine Fe 3 O 4 nanoparticles. The silica (SiO 2 ) shell in the nanoparticles improves residual compressive strength and prevents crack extension in cement mortars exposed to elevated temperatures. The investigations undertaken in this study were supported by optical and scanning electron microscopic studies. [ABSTRACT FROM AUTHOR]

In recent years utilization of solid waste in building materials has gathered spectacular attention. One material with potential applications, especially in cement-based composites, is waste glass. The aim of this study was to evaluate the possibility of manufacturing sustainable cement mortars with the use of nanosilica (NS) and brown soda-lime waste glass (WG) fine aggregate. The mechanical and thermal properties of cement mortars containing WG aggregate and nanosilica, were analyzed in terms of waste glass and nanosilica content. Ordinary fine aggregate (river sand) was replaced with WG fine aggregate at a ratio of 100% by weight. Moreover, 0, 1 and 3 wt% of NS was incorporated to cement mortar. The experiment revealed that the presence of WG fine aggregate significantly decreased the thermal conductivity of the cement mortars and that furthermore, the sorptivity coefficient decreased. The study has shown that WG fine aggregate can be a successful substitute for natural fine sand without leading to mechanical deterioration and by significantly improving thermal properties of cement mortars. Additionally, the incorporation of nanosilica (especially in higher contents – 3 wt%) leads to a further decrement in thermal conductivity and sorptivity and improves compressive strength. [ABSTRACT FROM AUTHOR]

In this contribution the effect of nanosilica (NS) on the behavior of cement mortars containing quartz aggregate and two types of heavyweight aggregates (magnetite and barite) exposed to elevated temperature will be investigated. The cement mortars have been modified with nanosilica in quantities of 1%, 2%, 3%, 4% and 5% (by weight of cement). The samples were exposed to the elevated temperatures of 200 °C, 400 °C, 600 °C and 800 °C, respectively. The mass loss, flexural and compressive strength of the cooled specimens were determined. Additionally, by means of scanning electron microscopy (SEM) and optical microscopy the structure defects have been determined. The results clearly demonstrate that there is an optimal nanosilica content, in the cement mortar containing quartz and magnetite aggregate, improving the thermal resistance and preventing the crack extension (especially in the range of 200–400 °C). However, the study has also shown that cement mortars containing barite aggregate tend to crack and exhibit spalling as a result of low thermal resistance of the aggregate. [ABSTRACT FROM AUTHOR]

The recycling of waste glass is a major problem for municipalities worldwide. The problem concerns especially colored waste glass which, due to its low recycling rate as result of high level of impurity, has mostly been dumped into landfills. In recent years, a new use was found for it: instead of creating waste, it can be recycled as an additive in building materials. The aim of the study was to evaluate the possibility of manufacturing sustainable and self-cleaning cement mortars with use of commercially available nanomaterials and brown soda-lime waste glass. Mechanical and bactericidal properties of cement mortars containing brown soda-lime waste glass and commercially available nanomaterials (amorphous nanosilica and cement containing nanocrystalline titanium dioxide) were analyzed in terms of waste glass content and the effectiveness of nanomaterials. Quartz sand is replaced with brown waste glass at ratios of 25%, 50%, 75% and 100% by weight. Study has shown that waste glass can act as a successful replacement for sand (up to 100%) to produce cement mortars while nanosilica is incorporated. Additionally, a positive effect of waste glass aggregate for bactericidal properties of cement mortars was observed. [ABSTRACT FROM AUTHOR]

The recycling of waste glass is a major problem for municipalities worldwide due to high disposal costs and environmental concerns. Recycling glass from the municipal solid waste stream in order to manufacture new glass products is limited due to high costs, impurities, and mixed color. Although colorless waste glass has been recycled effectively, colored waste glass with its low recycling rate, has mostly been dumped into landfills. Due to its high level of impurity, colored glass cannot be processed easily. A new use was found for it, instead of creating waste: an additive in building materials. In this study, the self-cleaning properties and strength development characteristics of mortar containing waste glass and nanomaterials (nanosilica – nSiO 2 and titanium dioxide – TiO 2 ) are analyzed in terms of waste glass content and the effectiveness of commercially available nanomaterials. Quartz sand is replaced with brown waste glass at ratios of 25%, 50% and 100% by weight. The photodegradation of the rhodamine B test has been conducted to analyze the effect of titanium dioxide, nanosilica and waste glass presence in the cement mortar for its potential application in self-cleaning façades. Studies have shown that waste glass can act as a successful replacement for sand, especially when mixed partially with sand. Additionally, a positive influence of nanomaterials on the self-cleaning and mechanical properties was noted. [ABSTRACT FROM AUTHOR]

This investigation studies the effects of hot water and hot air curing on the strength development, transport properties, and freeze-thaw resistance of mortars incorporating low-heat blast furnace slag cement and nanosilica (NS). Mortar samples were prepared and stored in ambient conditions for 24 h. After demolding, mortar samples were subjected to two different hot curing methods: Hot water and hot air curing (40 °C and 60 °C) for 24 h. For comparison purposes, mortar reference mixes were prepared and cured in water and air at ambient conditions. Strength development (from 1 to 180 days), capillary water porosity, water sorptivity, and freeze-thaw resistance were tested after 180 days of curing. The experimental results showed that both curing regimes accelerate the strength development of mortars, especially in the first seven days of hydration. The highest early strengths were reported for mortars subjected to a temperature of 60 °C, followed by those cured at 40 °C. The hot water curing regime was found to be more suitable, as a result of more stable strength development. Similar findings were observed in regard to durability-related properties. It is worth noting that thermal curing can more efficiently increase strength in the presence of nanosilica, suggesting that NS is more effective in enhancing strength under thermal curing. [ABSTRACT FROM AUTHOR]

It was shown that the uniform dispersion of nanoparticles into a cement matrix is a key issue in their application in the field. Therefore, here we compare two methods of incorporation of mesoporous silica nanospheres into cement using acetone (method A) or water (method B) as a dispersant, to reveal its influence on the mechanical properties of the formed composite. It was proven that in both cases, small amounts of silica nanoparticles agglomerates does not affect the mechanical properties of the cement mortars. However, the addition of mesoporous silica nanospheres to cement in an acetone solution is more effective and results in higher compressive and flexural strength than the sample of the composite formed from water solution of silica nanoparticles and cement. [ABSTRACT FROM AUTHOR]