Dosage Of Nanosilica Research Articles

Influence of pozzolanic addition on strength and microstructure of metakaolin-based concrete.

The intent of this study is to explore the physical properties and long-term performance of concrete made with metakaolin (MK) as a binder, using microsilica (MS) and nanosilica (NS) as substitutes for a portion of the ordinary Portland cement (OPC) content. The dosage of MS was varied from 5% to 15% for OPC-MK-MS blends, and the dosage of NS was varied from 0.5% to 1.5% for OPC-MK-NS blends. Incorporation of these pozzolans accelerated the hardening process and reduced the flowability, consistency, and setting time of the cement paste. In addition, it produced a denser matrix, improving the strength of the concrete matrix, as confirmed by scanning electron microscopy and X-ray diffraction analysis. The use of MS enhanced the strength by 10.37%, and the utilization of NS increased the strength by 11.48% at 28 days. It also reduced the penetrability of the matrix with a maximum reduction in the water absorption (35.82%) and improved the resistance to the sulfate attack for specimens containing 1% NS in the presence of 10% MK. Based on these results, NS in the presence of MK can be used to obtain cementitious structures with the enhanced strength and durability.

Enhanced fresh and hardened properties of foamed concrete modified with nano-silica

Nowadays, the application of nanotechnology has gained increased attention in the concrete technology field. Several applications of concrete require light weight; one such concrete used is foamed concrete (FC), which has more voids in the microstructure. In this study, nano-silica (NS) was utilized, which exhibits a pozzolanic nature, and it reacts with other pozzolanic compositions (like lime, alumina, etc.) to form hydrated compounds in concrete. Apart from these hydrated compounds, NS acts as a filler material and enhances properties of concrete such as the fresh and hardened properties. This research examines the fresh, hardened, and microstructural properties of FC blended with NS. The ratio of binder and filler used in this research is 1:1.5, with a water-to-binder ratio of 0.45 and a density of 880 kg/m3. A total of six different weight fractions of NS were added to FC mixes, namely 0%, 1%, 2%, 3%, 4%, and 5%. Properties assessed for FC blended with NS were the slump, bulk density, strength parameters (flexural, splitting tensile, and compressive strengths), morphological analysis, water absorption, and porosity. It was concluded from this study that the optimum NS utilized to improve the properties was 3%. Apart from this, the relationship between the mechanical properties and NS dosages was developed. The correlations between the compressive strength and other properties were analyzed, and relationships were developed based on the best statistical approach. This study helps academicians, researchers, and industrialists enhance the properties of FC blended with NS and their relationships to predict concrete properties from other properties.

Surface treatment with nano-silica and magnesium potassium phosphate cement co-action for enhancing recycled aggregate concrete

Abstract In this study, surface treatment, using blended materials of nano-silica (NS) and magnesium potassium phosphate cement (MKPC) slurries containing four dosages of NS, was applied to recycled aggregate (RA) with distinct RA maintenance schemes to enhance the RA concrete (RAC) performance and control NS dosage for economy. The results imply that the NS + MKPC slurry can efficiently bolster the bonding with RA and the new interfacial transition zone (ITZ), contributing to a distinct enhancement of RAC’s macro-properties. Besides, the optimal NS dosage and RA maintenance scheme revealed by the simplified linear weighted sum optimization method were 3% and no pre-curing procedure, respectively. On the basis of the aforementioned optimal conditions, the modified RAC (C-3-N) achieved enhanced compressive strength by 40.75%, split tensile strength by 46.26%, and chloride ion penetration resistance by 65.93% in comparison with the untreated RAC0. Moreover, the advantages observed in C-3-N were attributed to the exceptional microstructural characteristics in both the NS + MKPC slurry and the new ITZ. This study establishes the potential to augment the efficacy of nanomaterials in reinforcing RAC and enhance the economic viability and practicability of RAC applications. Simultaneously, these advancements contribute to fostering sustainable development within the construction industry and yielding environmental benefits.

Effect of Nanosilica on the Strength and Durability of Cold-Bonded Fly Ash Aggregate Concrete

Cold-bonded Fly Ash Aggregate (CFAA), as an alternative to natural coarse aggregates, can prepare more lightweight, economical, and sustainable concrete. However, CFAA concrete has insufficient durability, which hinders its application in a salt-corrosion environment. Nanosilica (NS) has an advantage of high activity and is generally used as an efficient mineral admixture in engineering. This study aims to improve the strength and durability of CFAA concrete by incorporating NS. To this end, compression tests, splitting tensile tests, and microscopic analyses were performed to investigate the mechanical properties of the concrete containing different NS dosages. Subsequently, the dry–wet and freeze–thaw durability tests were conducted to evaluate the salt-corrosion resistance and the frost resistance in the water, Na2SO4 solution, and Na2CO3 solution. The results show the compressive and splitting tensile strength peak at 2 wt% NS dosage. In this instance, the concrete has an optimum microstructure and exhibits desirable salt-corrosion resistance in the late stage of dry–wet cycles. During freeze–thaw cycles, NS could improve the frost resistance of the concrete but scarcely diminished internal damage under sulfate attack. The study explores the long-term performance of NS-modified CFAA concrete, providing a simple and effective method to mitigate the concrete deterioration in a harsh environment.

Effect of Nano-Silica and Sorbitol on the Properties of Chitosan-Based Composite Films.

Chitosan and its derivatives are widely used in food packaging, pharmaceutical, biotechnology, medical, textile, paper, agriculture, and environmental industries. However, the flexibility of chitosan films is extremely poor, which limits its relevant applications to a large extent. In this paper, chitosan/sorbitol/nano-silica (CS/sorbitol/SiO2) composite films were prepared by the casting film method using chitosan, sorbitol, Tween-80 and nano-SiO2 as raw materials. The structure of the films was characterized by infrared spectroscopy, electron scanning microscopy, and X-ray diffraction analysis. The effects of sorbitol and nano-silica dosage on the mechanical properties, thermal properties and water vapor barrier properties of the composite film were investigated. The results show that with the gradual increase in sorbitol (≤75 wt %), the elongation at the break of chitosan/sorbitol films significantly increased. When the addition of sorbitol was 75 wt %, the elongation at break of the chitosan/sorbitol composite film was 13 times higher than that of the chitosan film. Moreover, nano-SiO2 can further improve the mechanical properties and thermal stability of the chitosan/sorbitol composite films. When the amount of nano-silica was 4.5 wt %, the composite film became more flexible, with a maximum elongation of 90.8% (which is 14 times that of chitosan film), and its toughness increased to 10.52 MJm-3 (which is 6 times that of chitosan film). This study balances the tensile strength and elongation at break of the composite films by adding a plasticizer and nano-filler, providing a reference for the preparation of chitosan composites or their blending with other polymers, and has practical guiding significance for the industrial production of biomass plastics.

Synergistic Effect of Nano-Silica and Intumescent Flame Retardant on the Fire Reaction Properties of Polypropylene Composites.

Silica nanoparticles (nano-silica) were used as synergistic agents with ammonium polyphosphate (APP) and pentaerythritol (PER) to enhance flame retardancy of polypropylene (PP) in this research. The composites were prepared using a melt-mixing method. The influences of nano-silica on the fire performance of composites were thoroughly discussed, which promotes understanding of nano-silica on the flame-retardant performance of polypropylene composite. Scanning electron microscope (SEM) and energy-dispersive spectrometer (EDS) results indicated that the nano-silica with a diameter of about 95 ± 3.9 nm were dispersed favorably in the composite matrix, which might elevate its synergistic effect with intumescent flame retardant and improve the flame retardancy of polypropylene composite. The synergistic effects between nano-silica and intumescent flame retardant on PP composites were studied using the limiting oxygen index (LOI), UL-94 test, and cone calorimeter test (CCT). The total amount of flame retardant was maintained at 30%. When the dosage of nano-silica was 1 wt.%, the LOI value of PP/IFR/Si1.0 composite reached 27.3% and its UL-94 classification reached V-1. Based on the parameters of the CCT, the introduction of nano-silica induced composites with depressed heat release rate (HRR) and peak heat release rate (PHRR). The PHRR of PP/IFR/Si0.5 was only 295.8 kW/m2, which was 17% lower than that of PP/IFR. Moreover, the time to PHRR of PP/IFR/Si0.5 was delayed to 396 s, which was about 36 s later than that without nano-silica. EDS was used to quantitatively analyze the distribution of silica in charred residue. The EDS results indicated that the silica tended to accumulate on the surface during the fire. The surface accumulation characteristic of silica endows it with the enhanced flame-retardant properties of polypropylene composite at a very small dosage (as low as 1 wt.%).

Mechanical properties and durability of geopolymer concrete based on fly ash and coal gangue under different dosage and particle size of nano silica

In order to test the engineering applicability of mixed base geopolymer concrete and analyze the modification effect of nano additive systematically, nano silica (NS) was used to reinforce fly ash and coal gangue based geopolymer concrete (FACGGC). The mechanical properties and environmental suitability of the specimens were tested to analyze the effects of different dosing amounts (0–1.5 wt%) and particle sizes (20 and 100 nm) of nano silica on FACGGC. The results showed that the appropriate amount of NS could significantly improve the performance of FACGGC, excessive NS had significant negative impact. For different performance tests, the optimal dosage of NS was different. Under the same dosage, the effect of smaller particle size NS (20 nm) on the mechanical properties and water absorption of NS-FACGGC was better than larger particle size NS (100 nm), while the effect of larger particle size NS on resistance to sulfate attack was better. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and image analysis showed that NS with smaller particle sizes had a higher filling effect and were more likely to serve as nucleation sites, but when NS was over doped, the agglomeration effect of NS with smaller particle sizes was more significant.

Properties of sustainable high-strength concrete containing large quantities of industrial wastes, nanosilica and recycled aggregates

This research aims to study the effect of adding nanosilica (NS) on the properties of sustainable high-strength concrete (SHSC). The SHSC was produced using recycled aggregates from concrete debris as a 100% alternative to coarse aggregate, and industrial waste was used as supplementary cementitious materials at 50% and 75% of Ordinary Portland cement (OPC) weight. A total of 25 mixes, including control mix (The first mix was made as the reference by using only cement without replacement materals), binary mixes (OPC and fly ash (FA)), ternary mixes (OPC, FA and ground-granulated blast-furnace slag (GGBS)) and quaternary mixes (OPC, FA, GBFS and silica fume (SF)) were developed. The dosage of NS was 0%, 1%, 3% and 5% by binder ratio. The fresh properties of SHSC were evaluated by slump test, and the mechanical properties were assessed by testing the compressive strength, splitting tensile strength, flexural strength and modulus of elasticity. The transport properties were evaluated by water permeability, water sorptivity and chloride permeability tests. Results showed that compared with the reference mixture, the SHSC containing 75% of the quaternary blends with 3% NS achieved enhanced mechanical properties at 28 and 91 days, indicating that this mixture can achieve the highest sustainability performance. The SHSC mixture containing 3% NS and 50% quaternary mixtures achieved the highest performance of 80.7, 6.46 and 10.09 MPa for compressive strength, split tensile strength and flexural strength, respectively, at 28 days. This SHSC mixture also achieved water permeability; chloride permeability was 2.54 × 10−11 (cm/sec) and 1370 coulombs at 28 days.

Highly adsorptive removal of antibiotic and bacteria using lysozyme protein modified nanomaterials

In this paper, we studied adsorption of protein lysozyme on nanosilica and their applications for removal of levofloxacin (LFX) antibiotic and bacteria Escherichiacoli(E.coli) and Bacillus in water environment. Solution pH 10, contact time 120 min, nanosilica dosage 10 mg/mL and 1 mM KCl were the best conditions for lysozyme adsorption on nanosilica to form biomaterial, namely lysozyme modified nanosilica (LMNS). The optimal parameters for the removal of LFX using LMNS were determined to be 90 min of adsorption time, pH 8, and 10 mg/ml of adsorbent. Adsorptive removal of LFX dramatically increased in ideal circumstances, going from 51.51% to 80.63% when using LMNS. Two-step and Freundlich models were used to represent isothermal adsorption of LFX on LMNS at different strengths while a pseudo-second-order achieved the best fit for LFX adsorption kinetic on LMNS. The amount of LFX that adsorbs to LMNS reduced as salt concentration increased, suggesting that electrostatic interaction was primarily responsible for the adsorption. After four regenerations, LFX removal was greater than 60%, proving that LMNS is highly effective in removing LFX. The removal of E.coli and Bacillus were reached greater than 90 % that were much higher than other materials. Both electrostatic and hydrophobic interactions governed the removal of E.coli and Bacillus. Our results indicate that LMNS is an excellent bio-adsorbent for removal of antibiotic and bacteria in aqueous solution.

REINFORCED CONCRETE BEAM AT ULTIMATE LIMIT STATE CONSIDERING VARIABILITY IN THE CONCRETE MIX DESIGN PARAMETERS

Variability in design parameters of Civil Engineering infrastructure is inevitable at implementation in most practical situations, the effect of which can best be determined at design stage using reliability concepts. This study used First Order Reliability Method (FORM) to determine the effect of variation in Nano Engineered Concrete (NEC) mix design parameters on structural safety of Nano Engineered Reinforced Concrete (NERC) beams at ultimate limit state using reliability based sensitivity analysis. The variability in NEC mix design parameters was incorporated into EN1992-1-1(2008) design formulations using predictive models of NEC characteristic compressive strength developed on the basis of experimental data with the aid of DataFit statistical package. FORTRAN based subroutines of the NERC beam performance functions were developed and used for the reliability sensitivity analysis at ultimate limit state. Results indicate that variability in NEC mix design parameters affect structural safety of NERC beams in accordance with how the mix design parameter contributes to characteristic compressive strength development. Moreover, increase in nanosilica dosage beyond optimal value was found to have negative effect on structural safety of NERC beams. The study found that compressive strength contributes to tensile strength of NERC beams through composite action. Furthermore, the study suggested that the effect of variability in concrete mix design parameters be incorporated in design formulations of Civil Engineering Codes of Practice to aid estimation of safety of structural elements to be designed and produced with NEC for improved safety, sustainability and resilience of Civil Engineering infrastructure.

Synergistic effects of nano-silica and fly ash on the mechanical properties and durability of internal-cured concrete incorporating artificial shale ceramsite

Artificial shale ceramsite, a lightweight aggregate, has been widely used in construction field. However, it can lessen concrete's mechanical properties due to its porous inner-structure. In this study, nano-silica (NS) and fly ash (FA) was adopted to improve the mechanical performance and durability of internal-cured concrete containing artificial shale ceramsite (ASC-ICC). The synergistic effects of NS and FA on ASC-ICC was assessed by performing hydration degree, mechanical properties, durability under combined sulfate and drying-wetting attack, SEM-EDS and XRD investigations. Results show that incorporating NS and FA has a positive synergistic effect when the dosage of NS and FA is less than 2.5 and 20 wt%, respectively. When the amount of FA increases to 40 wt%, both mechanical properties and durability of ASC-ICC suffer a significant decrease given that the loose microstructure due to insufficient early-age hydration provides more channels for sulfate ions to access the inner concrete. The enhancing effect of NS is improved by the internal curing of ASC since more calcium hydroxide can be produced to participate in the pozzolanic reaction with NS. Mixture C1F2 exhibits the best performance given an increase of 64.29% and 16.26% in the compressive and flexural strength (compared to mixture C0F1) and an increase of 6.46% in the flexural strength (in comparison to the initial value) even after 49 attack cycles (i.e., 294 d), which indicates that the combination of 1.0 wt% NS and 20 wt% FA is most conducive to improving ASC-ICC performance.

High-flux bacterial cellulose ultrafiltration membrane with controllable pore structure

Nanocellulose membranes have attracted widespread attention because of its nano pore size, environmental friendliness, hydrophilicity and biocompatibility. However, the low water permeation, weak wet strength and high bacterial adhesion limit their pratical application. Herein, an ultrafiltration membrane based on bacterial cellulose (BC) with high flux, high wet strength and antibacterial property was prepared by using nano silica as porogen and polyhexamethylene guanidine hydrochloride (PHGHE) as both crosslinker and fungicide. Without affecting the uniformity of the membrane, a high dosage of nano silica was conducted to construct straight-through channels in the membrane Z direction, which greatly reduces the actual capillary tube length and increases the flux. The effective pore size was successfully controlled below 90 nm and the flux reached a high level of 7147 L·m−2·h−1·bar−1. After PHGHE modification, the wet strength of the BC membrane increased by 4.5 times (up to 4.47 MPa) as well as significantly improved the antibacterial performance (zone of inhibition=15.0–15.2 mm). The underwater superoleophobicity and nanoscale pore size make it excellent at separating nanoparticles and nanoemulsions with sizes even lower than 100 nm in aqueous solutions. The developed high flux BC membrane would have wide applications in wastewater separation and purification.

The Effect of Nanosilica Incorporation on the Properties of Cement-Based Materials with and Without other Supplementary Admixtures – A Literature Review

The development of nanotechnology has made it possible to design new materials and improve existing ones. Regarding new supplementary admixtures for cement-based materials, nanosilica is more advantageous than any other nanomaterial. This is due to its high pozzolanic reactivity, besides its filling and seeding effects, which are a consequence of the higher and more reactive specific surface area of the nanosilica and its amorphous structure. Nonetheless, when used improperly or in an inadequate dosage, such a nanomaterial may negatively affect the cement admixture, compromising both fresh and hardened properties. Hence, it is fundamental to understand the nanosilica’s behavior inside the cementitious medium. This review paper is based on recent literature about the incorporation of nanosilica in cementitious materials. The analyses showed that, once incorporated in the cement matrix, nanosilica tends to agglomerate. The behavior of such agglomerates influences both the pozzolanic filling and seeding effects. Therefore, a suitable dispersion of the nanoparticles must be achieved. In this sense, third-generation superplasticizers are used, usually up to 3% of cement mass. The mechanical properties of cement-based materials with nanosilica depend on the amount of nanomaterial and on its specific surface area. There is not an agreement on the optimum dosage of nanosilica, however, percentages up to 5% in cement mass seem to provide a better performance, when compared to greater ones. It is not worthy to use nanosilicas with excessive specific surface area values, because they tend to form large agglomerates, reducing fluidity and compressive strength. Particles with surface areas up to 300 m2/g usually present good performance. Nanosilica improves the early age strength and contributes to the pore refinement of cement-based materials. The combination of nanosilica with other nanomaterials or industrial by-products can improve the mixture’s performance. Nonetheless, the use of silica nanoparticles with agricultural wastes negatively affects the mechanical properties at early ages.

Nano-Silica-Modified Concrete: A Bibliographic Analysis and Comprehensive Review of Material Properties.

Several review studies have been performed on nano-silica-modified concrete, but this study adopted a new method based on scientometric analysis for the keywords’ assessment in the current research area. A scientometric analysis can deal with vast bibliometric data using a software tool to evaluate the diverse features of the literature. Typical review studies are limited in their ability to comprehensively and accurately link divergent areas of the literature. Based on the analysis of keywords, this study highlighted and described the most significant segments in the research of nano-silica-modified concrete. The challenges associated with using nano-silica were identified, and future research is directed. Moreover, prediction models were developed using data from the literature for the strength estimation of nano-silica-modified concrete. It was noted that the application of nano-silica in cement-based composites is beneficial when used up to an optimal dosage of 2–3% due to high pozzolanic reactivity and a filler effect, whereas a higher dosage of nano-silica has a detrimental influence due to the increased porosity and microcracking caused by the agglomeration of nano-silica particles. The mechanical strength might enhance by 20–25% when NS is incorporated in the optimal amount. The prediction models developed for predicting the strength of nano-silica-modified concrete exhibited good agreement with experimental data due to lower error values. This type of analysis may be used to estimate the essential properties of a material, therefore saving time and money on experimental tests. It is recommended to investigate cost-effective methods for the dispersion of nano-silica in higher concentrations in cement mixes; further in-depth studies are required to develop more accurate prediction models to predict nano-silica-modified concrete properties.

Influence of aggressive exposure on the degradation of nano-silica admixed cementitious mortar integrated with phase change materials

The objective of the present study is to evaluate the stability of cementitious mortar incorporated with phase change material (PCM, n-octadecane) at aggressive exposure conditions such as acid (1% H2SO4), alkali (5% Na2SO4) and chloride (5% NaCl). Thermogravimetric analysis (TGA) was performed to characterize and quantify the amount of deleterious compounds such as ettringite (Ca6Al2(SO4)3(OH)12·26H2O, AFt), gypsum (CaSO4·2H2O Gy) and Freidel’s salt (Ca2Al(OH)6(Cl, OH)·2H2O, Fs) formed due to the action of SO42− (acidic and alkaline media) and Cl− (chloride media) ions at the continuous exposure period of 180 days. Mass loss associated to the thermal degradation of n-octadecane PCM (CH3(CH2)16CH3) at various exposure solutions was also calculated at the temperature boundary of 250–300 °C. This study also highlights the introduction of optimized nano-silica dosage (3%) into the PCM based cementitious mortar to counteract the undesirable facets of PCMs on cementitious system.Results revealed that incorporation of PCM in cementitious mortar augmented the amount of AFt, Gy (at acid and alkali exposure solution) and Fs (at chloride exposure solution) formation, responsible for the amplified rate of deterioration. It is important to be noted that after long term exposure of 180 days no traces of PCM was observed in PCM based cementitious mortar mixes, which signifies the mixes no longer holds the capacity to store energy. However, co-occurrence of nano-silica (3%) in PCM based cementitious mixes curtailed the negative impact of PCM on cementitious mortars exposed to aggressive conditions significantly. Further, differential thermogravimetric (DTG) curve shows an additional endothermic peak at 250–300 °C for 3% nano-silica modified PCM based cementitious mixes even after exposure to aggressive ions that implies the ability of the mix to sustain the thermal efficiency characteristics of PCMs.

Experimental investigation on the effect of Nano-silica on the silica fume-based cement composites

The purpose of this work is to explore the effects of incorporation of nano-silica, in presence of silica fume and plasticizer, in cement mortar and concrete, in order to determine their appropriateness and advantages for concrete building. The research's goals were to optimize the amount of nanosilica used and to conduct tests on different fresh and hardened characteristics. To accomplish this goal, fresh characteristics of pastes (IST, FST, Consistency) and mortars (flow) as well as hardened characteristics of concrete (compressive strength) were investigated. SEM analysis was used to characterize the specimens morphologically. Based on the experimental investigation increase in consistency and decrease in IST, FST and flow was detected with increasing dosage of nanosilica. Intensification in compressive strength was higher at early age as compared to the strength at advanced age. Maximum compressive strength in concrete mixes was observed for specimen containing 3% nano-silica in presence of 10% silica fume and thereafter decrease in strength was observed but was still higher than that of the control specimen. The findings from SEM revealed that nano particles not only serve as filler but also as a promoter of the hydration process that improved the microstructure of concrete resulting in higher strength. The appropriate usage of nano-silica may thus enhance the performance of cemented materials.

Effect of using nano silica on mechanical properties of normal strength concrete

Using nanomaterials in the concrete enhances the strength and durability due to which it finds its applicability in the construction industry. Addition of nanomaterials reduce the cement content as cement increases the emission of carbon dioxide which causes greenhouse effect. In the present work, cement is replaced with various dosages of Nanosilica to understand its influence on the mechanical response of the concrete. With increasing amount of research being diverted to nanotechnology has gained major attention with its potential uses of particles. Nano silica is a fine convergent material. The hydration of cement is characterized by different substages and nanosilica effect on the hydration could be a result of diverse, even contradictory, behaviour of nanosilica in individual stages of the hydration. The research nowadays is mainly focusing on the basic science of cementitious material at nano/atomic level. Further, researchers are continuing to improve the durability and sustainability of concrete and have realized significant increment in mechanical properties of cementitious materials by incorporating nano-silica. The present study aims to investigate the acid resistance of M40, M50, M60 grades of concrete and the influence of nano silica in it. The replacement of cement by nano silica should considerably reduce the CO2 foot print of concrete.Experimental studies are conducted by varying the dosage of Nanosilica as replacement of cement for high strength concrete mixes. From the experimental studies, it can be observed that 3% was the optimum dosage of replacement of Nanosilica. Beyond 3%, the results corresponding to the mechanical properties are not promising. The experimental results are studied, discussed and presented.

Lightweight Structural Concrete

Using of Lightweight concrete (LWC) amounts to a lower cost and a better thermal performance due to its unique properties and light density. The main disadvantage in using lightweight concrete is that its mechanical properties are relatively poor. An effective method to improve the mechanical properties of lightweight concrete is using a dosage of nano-silica in the concrete mix. The gained enhancement of mechanical properties promotes a more serious discussion of structural applications of lightweight concrete. There exists an optimum dosage of nano-silica by which the mechanical properties enhancement is maximized. Increasing the nano-silica content beyond the optimum dosage degrades the mechanical properties. However, a fixed optimum dosage is not agreed upon in literature. This paper investigates the optimum dosage of NS to enhance the mechanical properties and microstructure of a lightweight concrete made with lightweight expanded clay aggregates (LECA). The results concluded that a dosage of 0.75% of nano-silica is optimum for the studied lightweight concrete mixes.

Will the magnesium sulfate attack of cement mortars always be inhibited by incorporating nanosilica?

This paper presents a detailed investigation on the durability of nanosilica (NS) blended cement mortars with different water-binder ratios (w/b, 0.35, 0.45, and 0.55) immersed in magnesium sulfate (MgSO4) solution up to 36 months. The visual appearance, liner expansion, mass change, and strength loss of the attacked specimens were measured along with the corresponding microstructural changes. The results showed that the incorporation of the lower content of NS (such as 1 wt%) was effective for inhibiting the MgSO4 attack, irrespective of the w/b; however, further increasing the NS replacement (5–8 wt%) aggravated the deterioration of blended mortars exposed to MgSO4 solution. At the low NS replacement ratio (1 wt%), the blended mortars with the w/b of 0.45 exhibited the lowest strength losses in comparison to the those with the w/b of 0.55 and 0.35. Nevertheless, at the high replacement ratio (3–8 wt%), lowering the w/b from 0.55 to 0.35 reduced the MgSO4 resistance of the blended mortars. Increasing the NS dosage and decreasing the w/b caused the greater degradation of C-S-H gel attacked by MgSO4. Both the lower permeability and the higher amount of CH were necessary for improving the durability of cement-based materials under the MgSO4 environment.

Laboratory study on the suitability of nano-silica as a modifier for asphalt binders

This paper reports the laboratory investigations carried out to assess the effect of nanosilica (NS) on the physical, morphological and rheological properties of asphalt binder. Two base binders (VG 10 and VG 30) are modified using two dosages of laboratory prepared NS (2% and 4%) by weight of the base asphalt binder. Rheological studies (10–70°C) include high temperature performance grading (PG), frequency sweep, multiple stress creep and recovery (MSCR) and linear amplitude sweep (LAS) tests. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) studies are also done to understand the structural modification process.It is found that NS induces amorphous nature to the base asphalt binder, as observed from XRD. SEM images show inclusions of NS as a layered interlocking network within the base asphalt binder. The true failure temperature, in high temperature PG grading, increased with the increase in percentage of NS. |G*|/sinδ master curve indicates improvement in rutting characteristics with increase in dosage of NS. The extent of improvement is found to be binder dependent. Since the stiffness of the base asphalt binder increases, |G*|·sinδ master curve drawn at 20°C shows loss in fatigue resistance by inclusions of NS. In MSCR test, the rutting resistance of NS modified asphalt binder is found to be higher than the base binder. The addition of 4% NS in VG10 increases the rutting resistance by approximately 6 times, whereas it is approximately 2 times for VG30. In VG10 the stress sensitivity reduces by 48% and 74%, respectively, by addition of 2% and 4% NS. The results from LAS test are not conclusive. Statistical analysis indicates that NS has no significant effect on the fatigue life of base asphalt binders, irrespective of test temperature. In general, it is concluded that NS modification is more beneficial for locations with high pavement temperatures and heavy vehicular loading conditions.