Addition Of Nanosilica Research Articles

Engineering properties of geopolymer concrete composites incorporated recycled plastic aggregates modified with nano-silica

The novel approach of reusing recycled plastic in construction instead of landfilling has gained recognition. However, the inclusion of recycled plastic aggregates (RPA) tends to have a negative impact on various concrete properties. Previous studies have explored surface treatment techniques to mitigate these effects. Nevertheless, there is limited research on enhancing the properties of RPA geopolymer concrete (GPC) through the addition of nano-silica (NS) particles in to the GPC mixtures. This study aims to experimentally investigate the properties of GPC incorporating RPAs modified with NS particles. The experimental program consists of seventeen mixtures divided into three stages. In the first stage, the effect of NS addition on the performance of GPC mixtures was evaluated. Moreover, the effect of different percentages of RPAs was investigated in the second phase. In the third stage, the optimum percentage of NS particles found in the first stage was utilized to improve the performance of GPC mixtures which aggravated in the second stage. The total binder content for all mixtures was 450 kg/m3 which contained 90% of ground granulated blast furnace slag (GGBFS) and 10% silica fume. In the first stage the GGBFS was replaced by 1%, 2%, 3%, and 4% NS particles, while, in the second stage, the natural fine aggregate was replaced by RPAs at six volume fractions (5%, 10%, 20%, 30%, 40%, and 50%). The fresh behaviour of all GPC mixtures was investigated to assess the flowability, setting and cohesiveness of the mixtures. The mechanical behaviour was evaluated for compressive strength, splitting tensile strength, modulus of elasticity, flexural strength, and stress-strain behaviour. Moreover, the microstructure characteristics were investigated to illustrate the modifications that occurred in the microstructure scale. The results indicated that the addition of an optimum percentage of NS particles can significantly restore most properties of RPA-GPC which were degraded due to the addition of RPAs. This technique can help the construction industry to safely use the RPAs in the GPC mixtures without concern about their negative impact on concrete performance.

Synergistic effects of recycled plastic aggregate and nano-silica on the elevated temperature and durability performance of self-compacting concrete

A new approach to reusing plastic waste in construction is by incorporating recycled plastic aggregates (RPA) in concrete. However, this technique negatively affects concrete properties. Previous studies have treated RPAs to mitigate this issue, but none have investigated enhancing the properties of self-compacting concrete (SCC) made with RPAs through the addition of nano-silica (NS) particles. This study aims to explore the properties of SCC with RPAs modified by NS. Sixteen mixtures were tested in three stages: evaluating the impact of NS on SCC performance, examining various RPA percentages, and using the optimal NS percentage to improve negatively affected SCC mixtures. NS particles replaced cement at 1%, 2%, and 3% in the first stage, while RPAs replaced natural fine aggregate (NFA) at fractions of 5%, 10%, 15%, 20%, 30%, and 40% in the second stage. Compressive strength was assessed over different periods and at elevated temperatures. Durability performance, including water absorption, acid attack, electrical resistivity, chloride permeability, and bulk electrical conductivity, was extensively studied. The results revealed that the addition of the optimal NS percentage effectively restored the most degraded properties of SCCs, making it a safe and effective technique for utilizing RPAs in SCC mixtures without compromising concrete performance.

Enhanced cement formation for well completion in gas hydrates reservoirs

Natural gas hydrates (NGHs) have abundant reserves and are greener energy source compared to petroleum resources. Intense heat release of cement slurry impacts the stability of NGHs during oil well cementing operations. Conventional low hydration-heat cement slurries significantly reduce the early-stage strength. In this paper, a novel strategy to optimize the exothermic and mechanical properties of cement slurry is proposed with the synergistic effects of various mineral admixtures and additives. The hydration heat and microstructure of cement with different admixtures were studied through isothermal calorimetry (IC), semi-adiabatic temperature test (ST), scanning electron microscopy (SEM), X-ray diffraction (XRD) and mechanical strength tests. The results indicate that the addition of nanosilica (NS) and C–S–H seeds lead to high early-stage strength for cement slurry substituted with high-volume fly ash (FA) and ground granulated blast furnace slag (GGBS), which meets the engineering performance for NGHs cementing. Compared with neat cement, blended cement designed with the new strategy has a 40.46% lower cumulative heat and a 56% higher compressive strength after 24 h. However, ST showed that the separated hydration heat rate peaks recombine together at higher temperature. The thermal storage performance of solid-solid phase change material (SSP) can effectively control the temperature rise due to cement hydration and maintain the separation of hydration heat rate peaks. This study provides novel ideas for the construction of low hydration heat and high early-stage strength cement slurry, and also provides key theoretical and methodological support for the performance control of cement slurry for NGHs cementing.

Performance assessment of capric acid-ethyl alcohol/expanded vermiculite phase change material incorporated cement mortar for thermal insulation in buildings

Due to global warming, the construction sector is looking for newer materials that can be incorporated into buildings to improve occupant thermal comfort while reducing energy consumption. The ability of construction materials to store thermal energy can be enhanced by incorporating phase change materials (PCM). A PCM is a substance that releases and absorbs energy at phase transition temperatures to offer useful heating or cooling. The addition of PCM in construction materials for thermal insulation has been proven beneficial by many researchers. The current study explores the feasibility of the incorporation of an organic PCM composite, which is developed by impregnating expanded vermiculite (EV) with capric acid (CA) using ethyl alcohol (EA) under vacuum conditions in cement mortar. Cement mortar mixes with EV, CA-EA/EV based PCMs, and PCMs with partially added nano silica and coir fiber combinations (PSC) were prepared by replacing fine aggregate in varied weights. Initially, the study on the primary characteristics of the developed PCM was introduced based on mechanical behavior, microstructure observations, and thermal effects. To estimate the field exposure capacity, PCM composite mortar boards were developed and tested for their physical and mechanical characteristics. Based on the findings of these tests, it was concluded that the presence of PCM improves the thermal characteristics of the mortar boards and the addition of nano silica and coir fiber enhances the physical and mechanical strength of the mortar boards. With regard to the characterization of the mortar, there was an increase in flexural strength by 8.06 % and a decrease in chloride diffusivity by 10.24 %, in water absorption by 17 %, the capillary water absorption coefficient by 8.56 % and the ultrasonic pulse velocity by 18.48 % relative to the control sample after addition of PSC into the mortar. Apart from the strength and durability studies, differential scanning calorimetry (DSC), energy-dispersive X-ray spectroscopy (EDS), thermogravimetry analysis (TGA) and scanning electron microscopy (SEM) tests were also carried out to characterize the thermal, chemical and morphological effects of the developed cementitious composite boards. As per the SEM and EDS test results, the fine aggregate replaced with 5 % of PCM in addition to nano silica and coir fiber (PSC-5 %) possesses better compatibility with the mortar by effectively penetrating through the pores. The DSC test results showed the melting and freezing point of PSC-5 % integrated mortar as 32.47 °C and 20.91 °C, respectively. A thermal conductivity value of 0.129 W/m·K also demonstrated the efficiency of PSC-5 % mortar board for maintaining better thermal comfort in buildings. The TGA assessment reported that the proposed PCM composite cement mortar board has excellent thermal durability.

The Effects of Nano-silica Addition on the Physical Properties of Polyethylene-Modified Asphalt Binder and the Mechanical Properties and Durability of Asphalt Mixtures

The Effects of Nano-silica Addition on the Physical Properties of Polyethylene-Modified Asphalt Binder and the Mechanical Properties and Durability of Asphalt Mixtures

Optimization of Geopolymer Compressive Strength Using Response Surface Methodology

Geopolymers have issues related to cracking resistance and pore filling, decreasing their mechanical strength. However, the addition of nanosilica and Cellulose Nanocrystals (CNCs) has been found to enhance their mechanical properties. This study focused on optimizing the utilization of nanosilica and CNCs to enhance the compressive strength of geopolymers. This research employed Response Surface Methodology (RSM) with Central Composite Design (CCD). The concentrations of nanosilica and CNCs used in the experiments ranged from 2% to 4% and 1% to 3%, respectively. The experimental results consist of 13 runs, including 5 center point runs. The model suggested concentrations of nanosilica and CNCs of 3.98% and 1%, respectively, for an optimal compressive strength of 22.20 MPa. The proposed quadratic model exhibited high accuracy, as evidenced by an R2 of 0.9865, Adj- R2 of 0.9769, and predicted R2 of 0.9168. The closeness of R2 to 1 indicates a strong correlation between the actual and predicted values, thus highlighting the model's significant relevance. Ultimately, the model developed in this study holds the potential for predicting the compressive strength of geopolymers incorporating nanosilica and CNCs.

Hygrothermal effect on interfacial properties of CFRP-steel joint modified by nanosilica

The interface between the carbon fiber reinforced polymer (CFRP) reinforcement system and steel substrates may deteriorate in service environments. This study is concerned with the effect of moisture and temperature conditions on the interfacial performance of CFRP-steel joints using neat/modified adhesive. Tensile and shear tests were conducted on both unmodified adhesive specimens and those modified with nanosilica to assess the impact of nanoparticles. Water immersion tests were carried out on adhesive specimens with different nanosilica contents to determine the water absorption law of the adhesives at different immersion temperatures. The interfacial properties of CFRP-steel bonded joints were tested before and after hygrothermal aging. The results show that nanosilica significantly influences the mechanical properties of the adhesive, as well as CFRP-steel joints. In dry conditions, tensile and shear strengths, Young’s modulus and the elongation of adhesive are improved by increasing the nanosilica content up to about 1.4 wt%. A higher content of nanosilica reduces adhesive strength and modulus, while the elongation increases continuously with nanoparticles increasing to 7 wt%. The water absorption of the adhesive is significantly influenced by the content of nanosilica. More nanosilica particles lead to slower diffusion in adhesion and smaller saturated water absorption. A high immersion temperature speeds up the moisture diffusion, resulting in a larger moisture content and a more severe degradation in adhesive performance with the same immersion duration. Hygrothermal aging can be delayed by the addition of nanosilica with low content. The interfacial properties of CFRP-steel joints, including interfacial shear strength, load capacity and plasticity, are weakened by hygrothermal aging. Changing the main failure mode from cohesive failure to interfacial debonding may occur in CFRP-steel joints due to aging. The more severe deterioration is caused by longer immersion or a higher immersion temperature. However, the addition of nanosilica can enhance the durability of the aged joints in the long run by improving the water resistance, although peak shear stress decreases when the nanosilica content exceeds 1.4 wt%. The trilinear bond-slip model of reinforced adhesive joints may be reduced to a bilinear model by hygrothermal aging. The incorporation of nanosilica helps to mitigate the reduction in fracture energy due to water immersion at normal and high temperatures.

Pelindung Dinding Terhadap Hujan Asam Menggunakan Geopolimer Berbasis Nanosilika dan Cellulose Nanocrystals

Geopolymers have a weakness in durability against exposure to acid rain. Nano-silica and Cellulose Nanocrystals (CNCs) can be incorporated to enhance the acid rain resistance of geopolymers. This study aims to investigate the durability of geopolymer-based nano-silica and CNCs against exposure to acid rain. This study employed a rain simulation infiltration method. The concentrations of nano-silica and CNCs used were 4% and 1%, respectively. The compressive strength of the geopolymer specimens was tested before and after exposure to assess the effects of acid rain. Additionally, SEM and XRD tests were conducted to analyze microstructural changes. The results revealed a significant reduction in the compressive strength of the geopolymer without nano silica and CNCs (36.14% and 26.73% at pH 4 and 5, respectively). In contrast, the geopolymer paste containing nano-silica and CNCs exhibited lower reductions of 22.93% and 19.77% at pH 4 and 5, respectively. These findings indicate that the addition of nano-silica and CNCs contributes to the preservation of compressive strength. The observed effect is attributed to the ability of nano-silica and CNCs to impede acid attack on the geopolymer paste, thereby preventing the degradation of calcium levels present in the fly ash within the geopolymer. The strength degradation of the geopolymer paste resulted from the breakdown of Al–O, Si–O, and calcium bonds within the system, triggered by the reaction with H2SO4 from the acid rain. Nano-silica and CNCs-based geopolymers exhibit positive effects and can be utilized as a coating on the walls of buildings.

Nanosilica in-situ produced with sodium silicate as a performance enhancing additive for concretes

This study proposes to use an in-situ produced nanosilica to enhance the performance of cement mortar. To this end, a two-step mixing method is developed. In Step I, low-cost sodium silicate and tannic acid (TA) solutions are mixed with the mixing water, in which TA can trigger the condensation of sodium silicate to produce porous silica nanoparticles and disperse the produced nanoparticles in the mixing water. The resulting mixing water with nanosilica is then directly used to mix cement mortar. Experimental results show that the compressive strength at 28d of the cement mortar produced by the proposed method is 35% higher than the one produced using the existing method. This strength improvement far exceeds what can be achieved by the ex-situ addition of nanosilica, which can be attributed to the fact that the in-situ produced nanosilica can significantly reduce the porosity of the cement paste, as revealed by the mercury intrusion porosimetry test. For the same reason, the produced cement mortar's resistance to sulfate attack is also enhanced by the proposed method. The proposed method is ready for large-scale field application in concrete since it overcomes all challenges facing the utilization of nanoparticles in concretes, such as high cost and difficult dispersion.

Rheology, mechanical properties and peel adhesion of hot-melt adhesive based on thermoplastic polyurethane/nanosilica

A series of thermoplastic polyurethane hot-melt adhesive formulations have been synthesized by melt blending of polyether-based thermoplastic polyurethane and different nanosilica, C5, and C9 hydrocarbon loadings. Different analyses, including FESEM, tensile strength, rotational rheometry, T-peel strength with polyester fabric, and nitrogen gas permeability, are conducted to examine the properties of the prepared adhesive formulations. The results show that the addition of 0.25 wt% of nanosilica increased the tensile properties of the polyurethane slightly and improved the T-peel strength with the polyester fabric. On the other hand, adding 5 wt% of C5 hydrocarbon tackifier reduced the tensile properties a bit, reduced the storage and loss modulus, and increased the T-peel strength with the polyester fabric. On the other hand, adding the C9 tackifier reduced the tensile strength more than the counterpart formulation including C5, reduced the storage and loss modulus and increased the T-peel strength. A noteworthy result was that the addition of nanosilica in the presence of C5 or C9 tackifiers lowered the loss and storage modulus and complex viscosity Adhesive formulation with 5 wt% of C5 tackifier has the highest average and maximum peel strength with about 20 and 35% higher strength than neat TPU.

RETRACTED: Fresh and mechanical performances of recycled plastic aggregate geopolymer concrete modified with Nano-silica: Experimental and computational investigation

Concerning environmental concerns, it has become crucial to invent and develop alternative construction materials that can replace ordinary Portland cement and use waste materials instead of natural aggregates in the production of concrete. An important advancement in this area is the utilization of recycled plastics to create geopolymer concrete, which helps reduce plastic waste and minimize the environmental impact of construction materials. Since plastics have become a significant environmental issue, it is imperative to find ways to recycle them for a sustainable future. Thus, this study was conducted involving the preparation of seventeen different mixtures of geopolymer concrete (GPC) in three stages. In the first stage, five GPC mixes were created with varying amounts of nano-silica (NS) ranging from 0 % to 4 %. The main objective of this stage was to determine the optimal NS content that could enhance the performance of the GPC matrix. In the second stage, recycled plastic aggregates (RPA) were introduced to replace a portion of the fine aggregates, ranging from 0.05 to 0.5 volume percentages. This aimed to assess the impact of RPAs on the fresh GPC and its mechanical properties. The third stage involved an analysis to improve the performance of the GPC compound incorporating RPAs. The optimal NS content identified in the first stage was utilized for all mixtures with RPA. Lastly, several modeling techniques, including artificial neural network, M5P tree, multiple linear regression, full quadratic, multi-expression programming, and linear regression, were employed to predict the compressive strength of the GPC compound. The results demonstrated that the addition of nano-silica increased the compressive strength of the GPC mixtures by 6.3 %, 13.4 %, 20.5 %, 21 %, and 21.9 % at curing ages of 3, 7, 28, 90, and 180 days, respectively, when using 3 % NS content compared to the control GPC mixture. However, the inclusion of NS had a negative impact on the workability of the GPC mixes. Furthermore, incorporating RPAs reduced both the workability and compressive strength of the GPC compound. In the end, the results obtained from the modeling analysis revealed that the compressive strength of GPC could be predicted with a high degree of accuracy by taking into account the mixture proportions of its constituents. Among the various techniques used, it was found that the artificial neural network model outperformed other methods in accurately forecasting the compressive strength of GPC. This indicates that the neural network model is a superior and reliable approach for estimating the strength characteristics of GPC, providing valuable insights for optimizing its composition and enhancing its overall performance.

Experimental investigation on the performance of ground granulated blast furnace slag and nano-silica blended concrete exposed to elevated temperature

Minimising the risk of fire and structural collapse are primary goals in the design of concrete buildings. This study aimed to determine how nano-silica (NS) and ground granulated blast furnace slag (GGBFS) additives, used to replace some proportion of cement, affected the behaviorof concrete when subjected to elevated temperatures ranging from 27 °C to 1000 °C. The mechanical and durability properties of concrete containing NS (0%-5%) and GGBFS (0%-25%) were investigated after being exposed toelevated temperatures. The concrete samples were heated according to ISO 834 standardized fire curve. After exposing the concrete to a higher temperature, it was cooled using the water cooling (WC) and air cooling (AC) process. It was found that when exposed to increased temperatures, concrete containing nano-silica and GGBFS performed better than concrete without any of these additives. The addition of 4% of nano-silica and 20% of GGBFS in concrete enhanced the instinctive and resilient characteristics of concrete up to the raised temperature of 400 °C after that drastic degradation of mechanical and durability properties was recorded for higher temperatures of the range 1000 °C. It showed that using nano-silica and GGBFS in concrete needs to be done delicately when the building could be exposed to a temperature of 400 °C and beyond. The microstructure analysis was performed and it showed that the utilization of nano-silica and GGBS in concrete can enhance the post-fire performance of concrete. Further, the relationship between residual properties of concrete exposed to raised temperature was assessed and empirical relations were proposed. It was observed that the predicted result of residual properties was in good agreement with the experimental results.

Enhancement of mechanical properties of oil well cement by nano-SiO2/h-BN

In this study, high-strength oil-well cement with hybrid nanosilica (NS) and nanohexagonal boron nitride (h-BN) additives was prepared to reduce effectively the environmental pollution caused by fluid leakage from oil wells owing to weakened cementing rings and extend the lifetimes of oil wells. It was confirmed that NS/h-BN can enhanced the mechanical strength of oil-well cement at 7 and 28 days. The effects of NS and h-BN on the mechanical properties of oil-well cement at 7 days (d) and 28 d were investigated by varying the nanomaterial content to determine the weight percentages of the nanomaterials that optimized the mechanical properties. The experimental results showed that the ideal ratio content of nanomaterials was 2.5 wt% NS and 0.5 wt% h-BN, and the minimum porosity measured by a low-field nuclear magnetic resonance test was 16.48%, which was 50.24% lower than that of the blank group. After 28 d of curing, the compressive, flexural, and splitting tensile strengths were 12.15 MPa/25.99%, 3.75 MPa/42.86%, and 1.39 MPa/41.25% higher than those of the blank group. The mechanical strength of the oil-well cement increased with the NS content, whereas with the increase in h-BN content, sequential rising and falling tendencies were observed. The microstructure, pore structure, and hybridization modification mechanism of the NS/h-BN oil-well cement were analyzed using X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. This high-mechanical strength and low-porosity hybrid nanomaterial oil-well cement system can provide an experimental basis for the application of novel high-strength cement types in oil fields.

Effect of nano silica on solidification/stabilization of heavy metal in alkali-activated MSWI fly ash solidified body

Municipal solid waste incineration fly ash (MSWIFA) containing considerable heavy metals is classified as a hazardous waste. Alkali-activated technology can effectively improve the environmental safety of MSWIFA. Due to the low silica content of MSWIFA, the addition of nano silica (NS) solves the problem to enhance the ability of solidification/stabilization (S/S) and maximize the utilization of MSWIFA. NS/MSWIFA solidified body was prepared by alkali-activated technology in this work. The mechanical and environmental properties of NS/MSWIFA solidified body with various dosages (0–3 wt%). NS were characterized by compressive strength, leaching concentration, and chemical speciation distribution of heavy metals. A comparative study of MSWIFA and solidified bodies for exploring S/S mechanisms was investigated using XRD, FTIR, TG/DTG, NMR, and SEM/EDS tests. The results showed that the leaching concentration of Pb in MSWIFA based on different leaching methods was 23.54 mg/L and 31.7 mg/L, 19.6 times higher than the standard of hazardous waste landfill and 126.8 times higher than the standard of landfill site of municipal solid waste, respectively. The total amount of Zn and Pb was 4739 mg/kg and 2451 mg/kg, respectively, exceeding other heavy metals by 1–2 orders of magnitude. When the addition of NS was 2 wt% and 3 wt%, the compressive strength and the leaching concentration of heavy metals in solidified bodies reached the highest and the lowest, respectively. Comparative analysis indicated that adding NS promoted heavy metals in MSWIFA to be converted into a stable state, and increased hydration product C-(A)-S-H gels formation, making the structure denser. On a broader perspective, NS/MSWIFA solidified body was developed as a low-carbon and environment-friendly binder.

Study on foam concrete incorporated with expanded vermiculite/capric acid PCM – A novel thermal storage high-performance building material

A major part of energy consumption is reported from the residential and commercial buildings due to the large usage of mechanical devices to maintain a comfortable indoor ambiance. Thermal conductivity of the materials used in these buildings can be reduced by using low density materials and an efficient thermal energystorage strategy. In the present paper, the thermal performance ofa building envelope was improved by incorporating phase change material (PCM) into thefoam concrete mix. At first, PCM was developed by using a light weight material, expanded vermiculite (EV) impregnated with capric acid (CA) and ethyl alcohol (EA) under vacuum conditions. Different foam composite mixes were prepared and experimentally tested. Foam concrete mixtures with EV, CA-EA/EV based PCM, and PCM with added nano silica and coir fiber combinations (PSC) were prepared by the replacement of fine aggregate (M−sand) in various weight percentages. This study reveals that PCM with a CA to EV proportion of 55% (wt.) had the maximum adsorption and stability, as assessed through liquid leakage. In addition to improving thermal efficiency, PCM enhanced foam concrete composites showed improved mechanical, hydration, durability, and thermal characteristics. In comparison to the control foam concrete and PCM foam concrete mixes, the addition of nano silica and coir fiber added foam concrete mixtures (PSC) demonstrated improved strength and shrinkage qualities. These improved properties are attributed to the pozzolanic activity of nano silica and the bridging effects resulting from the fiber to micro cracks. Apart from the durability and strength characteristics, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), differential scanning calorimetry (DSC), and thermogravimetry analysis (TGA) were adopted to characterize the morphological, chemical, and thermal aspects of the different foamed concrete mixtures. The DSC results proved that the PSC-5% foam concrete mixture had latent heat capacities of 43.90 J/g for cooling and 69.16 J/g for heating, with melting and solidification temperatures of 31.51 °C and of 21.77 °C, respectively. TGA also revealed that theproposed PCM composite has a high thermal resistance. The PSC-5% shows bettercompatibilityas perSEM and EDS tests by the proper penetration of the nano silica in the foamed compositesthrough the pores. Finally, the thermal analysis tests demonstrated that the PSC-5% has a thermal conductivity of 0.129 W/m-K, which is 49.60% lesser than the foam concrete control sample, and also possesses an improved heat storage capacity, which ensures better thermal comfort in buildings.

Post-Fire Mechanical Degradation of Lightweight Concretes and Maintenance Strategies with Steel Fibers and Nano-Silica

Currently, the growth of building construction and the need for lighter but more sustainable materials are of interest. Additionally, recent fire incidents highlight the insufficient knowledge of the properties of materials after a fire. Common materials such as concrete should, to minimize their adverse environmental effects and expenses, be maintained in such a way as to increase their resistance and preserve their mechanical properties when subjected to high temperatures. Hence, in this research, the post-fire mechanical degradation of lightweight concrete (LWC) has been investigated. Moreover, the addition of steel fiber and nano-silica have been studied in terms of their ability to reduce the mechanical degradation of LWC subjected to high temperatures. For this purpose, different samples were considered in four mixture designs: the LWC samples, samples with steel fibers, samples with nano-silica, and samples with a combination of steel fibers and nano-silica. All samples were subjected to temperatures of 200, 400 and 600 degrees Celsius and compared with the control samples. The results show that, as the temperature increased, the tensile and compressive resistances of LWC decreased. The samples without fibers and nano-silica showed a greater decrease in mechanical properties with increasing temperature. The addition of steel fibers and nano-silica, individually or as a combination, can improve the compressive and tensile strength of the concrete both at room temperature and at higher temperatures.

Preparation and Properties of Poly(butylene adipate-co-terephthalate)/thermoplastic Hydroxypropyl Starch Composite Films Reinforced with Nano-Silica.

The use of biodegradable plastics is gradually increasing, but its expensive cost limits promotion. In this study, poly(butylene adipate-co-terephthalate)/thermoplastic hydroxypropyl starch reinforced with nano-silica (PBAT/TPHSg-SiO2) composite films with high hydroxypropyl starch content were prepared in a two-step process. The effect of reinforced thermoplastic hydroxypropyl starch on the mechanical, thermal, processing properties, and micromorphology of the composite films was investigated. The results showed that the tensile strength of the composite films was significantly improved by the addition of nano-silica, with 35% increase in horizontal tensile strength and 21% increase in vertical tensile strength after the addition of 4 phr of nano-silica. When the content of thermoplastic hydroxypropyl starch reinforced with nano-silica (TPHSg-4SiO2) is 40%, the horizontal and vertical tensile strengths of the films are 9.82 and 12.09 MPa, respectively, and the elongation at break of the films is over 500%. Electron micrographs show that TPHSg-4SiO2 is better homogeneously dispersed in the PBAT and exhibits a bi-continuous phase structure at a TPHSg-4SiO2 content of 40%. In this study, the blowing PBAT/TPHSg-4SiO2 composite films effectively reduce the cost and still show better mechanical properties, which are suitable for packaging applications.

Axial compression performance of CFST columns reinforced by ultra-high-performance nano-concrete under long-term loading

Abstract The addition of nano-silica to ultra-high-performance concrete (UHPC) to increase its toughness has been proposed to obtain ultra-high-performance nano-concrete (UHPNC). This work mainly studies the reinforcement effect of UHPNC on concrete filled steel tube (CFST) columns under long-term load. Ten CFST columns strengthened with UHPNC were selected and reinforced with UHPNC. The influences of different thicknesses of UHPNC reinforcement layer and different nano-silica contents on the axial compression properties of specimens were mainly studied, by loading specimens in two steps: long-term load and ultimate load. This study discussed the failure modes, compressive toughness, ultimate bearing capacity, initial stiffness, and ductility coefficient of the specimens. The results show that the outsourced UHPNC reinforcement method is an effective method to improve the performance of CFST columns during service period. With the increase in the thickness of UHPNC reinforced layer, the ultimate bearing capacity of CFST column increases greatly. The compression toughness is increased with the increase in nano-silica content and UHPNC reinforcement layer thickness. The decrease rate of initial stiffness increases with the increase in nano-silica content.

Thermodynamically-equilibrium LCST phase diagram of PCL/SAN mixtures determined by thermal analysis: Opposing effects of hydrophilic and hydrophobic silica nanoparticles

In this work, the isothermal crystallization kinetics of PCL in PCL/SAN blend and PCL/SAN/nanosilica nanocomposite systems has been applied as a useful and sensitive variable for determining the LCST phase diagram. By eliminating the impacts of kinetic variables, the variations in the equilibrium LCST phase boundary of PCL/SAN mixtures were evaluated. The presence of hydrophobic nanoparticles shifted the equilibrium LCST phase diagram to higher temperatures as expected owing to the compatibilization effect of nanoparticles, while the hydrophilic nanoparticles shifted it to lower temperature. The preferential migration of hydrophilic nanosilica into SAN-rich phase with slower molecular dynamics caused larger viscoelastic asymmetry of polymeric phases and consequently, lower area of phase miscibility window. In contrast, the addition of hydrophobic nanosilica with better dispersion state and no preferential localization in PCL/SAN blend resulted in a shift of LCST phase diagram to higher temperatures.

Effect of composition of geopolymer composites containing fly ash and waste glass powder on their durability and resistivity demonstrated in presence of a nanocarbon additive in a form of graphene

The objective of this study was to obtain a geopolymer composite with semi-conductive or conductive properties for self-control of abnormal symptoms caused by damages to its microstructure. For that purpose effects of different content of fly ash, waste glass powder, as well as two types of graphene and hydrophilic and hydrophobic nanosilica on electrical, physical and mechanical properties were tested. Measurements of resistivity showed the capacity for electrical charge flow in composites, which depended on their composition and products of the geopolymer hardening process. Based on results of the electrical charge flow intensity and observations of geopolymer composite microstructure by means of XRD and scanning microscopy, a possible course of the electrical conductivity mechanism in geopolymer materials was indicated. It was found that geopolymer composites containing fly ash, as well as addition of graphene and hydrophobic nanosilica, showed the most favourable electrical charge conductivity parameters and the highest strength gain.