Dosage Of Nanosilica Research Articles

Strength-enhanced ecological ultra-high performance fibre-reinforced cementitious composites with nano-silica

An economical and ecological (ECO) ultra-high performance fibre reinforced cementitious composite (UHPFRCC) with a high volume of mineral admixture as part of the binding materials and river sand as the aggregate was designed. The flowability and strength development of ECO-UHPFRCC with various dosages of nano-silica were studied. The effects of nano-silica on the morphology of hardened matrix microstructure and the hydrates characteristics were investigated by SEM, XRD, TG and nano-indentation. The results demonstrated that the mechanical properties of the ECO-UHPFRCC were significantly improved with the increased dosage of nano-silica; its compressive strength exceeded 200 MPa after 3 days of steam curing when mixed with 4% by weight of nano-silica. The static mechanical properties of ECO-UHPFRCC were enhanced as a result of the optimized micro-properties. The mechanism of the effects of nano-silica on the performance of ECO-UHPFRCC microstructure were investigated and discussed as well.

Effects of Nanosilica on Compressive Strength and Durability Properties of Concrete with Different Water to Binder Ratios

The effects of the addition of different nanosilica dosages (0.5%, 1%, and 1.5% with respect to cement) on compressive strength and durability properties of concrete with water/binder ratios 0.65, 0.55, and 0.5 were investigated. Water sorptivity, apparent chloride diffusion coefficient, electrical resistivity, and carbonation coefficient of concrete were measured. The results showed that compressive strength significantly improved in case of water/binder = 0.65, while for water/binder = 0.5 no change was found. Increasing nanosilica content, the water sorptivity decreased only for water/binder = 0.55. The addition of 0.5% nanosilica decreased the apparent chloride diffusion coefficient for water/binder = 0.65 and 0.55; however, higher nanosilica dosages did not decrease it with respect to reference value. The resistivity was elevated by 0.5% nanosilica for all water/binder ratios and by 1.5% nanosilica only for water/binder = 0.5. The carbonation coefficient was not notably affected by increasing nanosilica dosages and even adverse effect was observed for water/binder = 0.65. Further information of microstructure was also provided through characterization techniques such as X-ray diffraction, thermal gravimetric analysis, mercury intrusion porosimetry, and scanning electron microscopy. The effectiveness of a certain nanosilica dosage addition into lower strength mixes was more noticeable, while, for the higher strength mix, the effectiveness was less.

Effects of nano-silica on the strength development of geopolymer cured at room temperature

Use of nano-silica is gaining wider attention due to its significant effect on the microstructural and mechanical properties of Portland cement based binders. Effects of the incorporation of nano-silica in fly ash based geopolymer binders have been investigated in this study. Low-calcium fly ash was used as the principal source of aluminosilicate and it was blended with either blast furnace slag or Portland cement at small percentages in order to accelerate the curing at room temperature. Nano-silica was used at a rate up to 3% of the total binder in order to understand its effect on the strength and microstructural development. The experimental results show that the strength and microstructural properties could be further developed with inclusion of nano-silica in geopolymer mixes. Compressive strength increased with the increase of nano-silica content up to 2%. Scanning electron microscopy (SEM) images showed denser microstructures with well-connected interlocking morphology for the optimum nano-silica dosage. The strength increase is contributed by densification of the microstructure with the addition of nano-silica.

Effect of Type, Size, and Dosage of Nanosilica and Microsilica on Properties of Cement Paste and Mortar

Many studies attention are being devoted to use of nano-scale silica particles in cementitious materials by considering the success of using silica fume in concrete as an active pozzolan. The effect of various types of nanosilicas (NSs), both in powder and colloidal forms, with specific surface area (SSA) from 80 to 380 m²/g (0.016 to 0.078 ft²/lb) on the mechanical properties of cement paste and mortar were studied. Results showed a substantial reduction in the workability of mixtures by adding NS particles. The compressive strength of specimens was not affected by NS in powder and colloidal form, but was only sensitive to changing SSA. The use of NS enhanced the strength of cement paste compared to the control mixture, and the level of improvement increased for higher dosages of NS. However, by increasing the SSA more than 90 m²/g (0.018 ft²/lb), the compressive strength of specimens decreased. A low percent of various NSs did not affect compressive strength of mortar. However, adding a high dosage of NS particles created the same effect as using microsilicas.

Effect of Nanosilica on Rheology, Fresh Properties, and Strength of Cement-Based Grouts

AbstractThe effect of colloidal nanosilica on the fresh and rheological parameters, plastic shrinkage, heat of hydration, and compressive strength of cement-based grouts is investigated in this paper. The fresh and rheological properties were evaluated by the minislump flow, Marsh cone flow time, Lombardi plate cohesion meter, yield value, and plastic viscosity. The key parameters investigated were the dosages of nanosilica and superplasticizer and temperature of mixing water. Statistical models and isoresponse curves were developed to capture the significant trends. The dosage of nanosilica had a significant effect on the results. The increase in the dosage of nanosilica led to increasing the values of flow time, plate cohesion meter, yield stress, plastic viscosity, heat of hydration at 1 day and 3 days, and compressive strength at 1 day, while reducing the minislump, plastic shrinkage up 24 h, and compressive strength at 3, 7, and 28 days. Conversely, the increase in the dosage of superplasticizer led ...

Properties of concrete incorporating nano-silica

This study investigated the effect of colloidal nano-silica on concrete incorporating single (ordinary cement) and binary (ordinary cement+Class F fly ash) binders. In addition to the mechanical properties, the experimental program included tests for adiabatic temperature, rapid chloride ion permeability, mercury intrusion porosimetry, thermogravimetry and backscattered scanning electron microscopy in order to link macro- and micro-scale trends. Significant improvement was observed in mixtures incorporating nano-silica in terms of reactivity, strength development, refinement of pore structure and densification of interfacial transition zone. This improvement can be mainly attributed to the large surface area of nano-silica particles, which has pozzolanic and filler effects on the cementitious matrix. Micro-structural and thermal analyses indicated that the contribution of pozzolanic and filler effects to the pore structure refinement depended on the dosage of nano-silica.