Modified Silica Fume Research Articles

The Dispersion and Hydration Improvement of Silica Fume in UHPC by Carboxylic Agents.

Silica fume (SF) is an essential component in ultra-high-performance concrete (UHPC) to compact the matrix, but the nucleus effect also causes rapid hydration, which results in high heat release and large shrinkage. In this paper, the carboxylic agents, including polyacrylic acid and polycarboxylate superplasticizer, were used to surface modify SF to adjust the activity to mitigate hydration at an early time and to promote continuous hydration for a long period. The surface and dispersion properties of modified SF (MSF), as well as the strength and pore structure of UHPC, were studied, and the stability of the modification was also investigated. The results demonstrated that, after treatment, the carboxylic groups were grafted on the SF surface, the dispersion of SF was improved due to the increased negative pentanal of the particle surface and the steric hindrance effect, the early hydration was delayed about 3-5 h, and the hydration heat release was also mitigated. The compressive strength of UHPC with MSF reached a maximum of 138.7 MPa at 3 days, which decreased about 3.7% more than the plain group, while flexural strength varied insignificantly. More pores and cracks were observed in the matrix with MSF, and the hydration degree was promoted with MSF addition. The grafted group on SF fell off under an alkali environment after 1 h.

Synthesis and effect of using silica fume particles on shear properties of basalt fibers‐epoxy composites

AbstractIn this study, the effect of the addition of silica particles modified with silane agent on the mechanical properties of basalt fibers‐epoxy composites were studied with the interlayer shear strength (ILSS) test. In the first stage, silica fume particles were synthesized using the sol‐gel method and surface modified using tri mercaptopropyl trimethoxy silane agent. The results of the characterization showed that the synthesized powder is nanometric scale, amorphous and high purity. The surface‐modified silica fume particles (0, 2, 4, 6 wt.%) were distributed inside the epoxy matrix using a mechanical stirrer and ultrasonic waves. The hand lay‐up method was used to fabricate composite samples, then the effect of adding these particles on the mechanical properties of basalt fibers‐epoxy composites under interlayer shear loads was studied. The results of the research indicated that the addition of silica fume particles has a significant effect on improving the mechanical properties of basalt fibers‐epoxy composites, and the greatest improvement in mechanical properties was achieved by adding 4 wt.% of modified silica fume particles. In the case of composites without SF particles, the shear strength was 34 MPa, which was increased to 40 MPa by adding 4 wt.% of SF particles (about 20% improvement). On the other hand, results demonstrated that the optimal distribution of silica fume particles within the polymer matrix performs an impressive role in improving the mechanical response of composite samples.Highlights The use of silica fume in the polymer composite is one of the research innovations. Silica fume is a super‐fine spherical powder that is collected as a by‐product. The silane is used to better distribute and optimal interaction of the silica fume in epoxy. Sol‐gel is one of the methods to synthesis of silica fume. ILSS test was done to investigate the strength of the interface of basalt fibers and epoxy.

Interfacial nano-engineering by graphene oxide to enable better utilization of silica fume in cementitious composite

As an industrial by-product, silica fume (SF) has been widely employed as supplementary cementitious material to develop high-performance concrete, and contribute to the sustainability goals of the concrete industry. However, with the typical size in the range of 50–300 nm, SF particles tend to form agglomerations when mixed with water and quickly become covered by a gel-like layer, thus retarding hydration. In this study, SF was coated with graphene oxide (GO) to nano-engineer the interface between SF and cement, aimed to allow better utilization of SF in cementitious composites. We report the concept of a nano/microhybrid via the electrostatic adsorption of negatively charged GO on positively charged modified SF (termed as MSF@GO), which aims to improve the dispersion quality of SF as well as the SF-cement interaction. The addition of 5 wt% modified SF (MSF) and 0.04 wt% GO (by mass of binder) result in a significant improvement of 3-d and 28-d compressive strengths of a cement paste by 56% and 29%, respectively, as compared to the sample incorporating 5 wt% SF. Additionally, the 5MSF@GO paste exhibits a greatly reduced initial sorptivity, by 33% (from 1.56 mm to 1.05 mm), along with the lowest secondary sorptivity. The noticeably higher strengths and lower water transport are primarily attributable to the increased polymerization of calcium silicate hydrates and the refinement of pore structure. This study demonstrates the great potential to improve the utilization efficiency of SF by interfacial nano-engineering with GO nanocoating and provide a new strategy to develop low-carbon cementitious composites for practical applications.

Effects of silica fume powder modified by oleic acid on the settleability of bulking sludge

ABSTRACT Modified silica fume powder with oleic acid through coupling agent was prepared based on the in situ utilizing long-chain fatty acids (LCFA) properties of Microthrix parvicella (M. parvicella) in the activated sludge system. The modification was confirmed by XRD and infrared spectrum. The contact angle analysis showed that the modification gave the silica fume powder a hydrophobic surface. The modified silica fume powder had a good combination with M. parvicella from the SEM and Gram staining measurements. The addition of modified silica powder has a certain effect on the settling capacity of sludge, but has little effect on the sludge treatment capacity, while the SVI dropped from 400.1 to 100.0 mL/g. These suggested that the modified silica fume powder could be used as an excellent weight-increasing agent to inhibit sludge bulking.

Effect of Modified Silica Fume Using MPTMS for the Enhanced EPDM Foam Insulation.

Silica fume (SF) is a by-product from the production of silicon metal, which has a relatively high silica concentration. The surface modified silica fume (mSF) is treated with (3-mercaptopropyl) trimethoxysilane (MPTMS) as filler in ethylene propylene diene monomer (EPDM) foam. The FTIR spectra of mSF clearly indicated that MPTMS can be successfully bonded to the SF surface. The reinforcing efficiency of mSF-filled EPDM foam insulation indicated that the mechanical properties such as hardness, tensile strength, modulus, and compression set enhanced higher than in case of SF and calcium carbonate. While the cure characteristics such as the maximum torque (MH), the minimum torque (ML) and the differential torque (MH-ML) are increasing in proportion to increasing filler contents, mainly with mSF. For the cure behavior, the mSF-filled EPDM foam insulation showed the fastest cure time (tc90) and scorch time (ts2) due to reduced accelerator adsorption. Whereas, the calcium carbonate-filled EPDM foam insulation increased the cure time (tc90) and scorch time (ts2), therefore, it also prevents compound scorching. The results indicated that the mSF with MPTMS can be used as an alternative filler for EPDM foam insulation.

Effect of Modified Silica Fume and Cellulose Fiber Used as Fillers on Properties of Antivibration Rubber

The effect of modified silica fume (mSF) and cellulose fiber (CF) content on the cure characteristics, mooney viscosity, mechanical, durability and heat resistance properties are investigated; as compared with SF and unfilled natural rubber. From the results reveal that mSF and CF affect not only fast cure rate, high viscosity but also improve rubber mechanical and heat resistance properties. Additionally, the mSF and CF are added into the natural rubber to produce antivibration rubber product and then study the rubber product performance such as durability properties. The mSF and CF effective in improving the crack resistance of antivibration rubber product more than SF and unfilled natural rubber which is due to enhancing the stiffness. The all obtained results, it can be proved that mSF and CF as the new alternative fillers in rubber industry.

Silica and modified silica fume waste (mSF) as reinforcing fillers for rubber industry

Purpose The purpose of this paper is to evaluate the efficiency of commercial silica, silica fume-waste (SF) and modified silica fume-waste (mSF) as reinforcing filler in acrylonitrile-butadiene rubber (NBR) and ethylene propylene diene monomer (EPDM) through the mixing process of rubber. The composites were prepared using different loadings of silica fume and commercial silica in EPDM and NBR composites. Structural characterization of silica and SF was done using X-ray fluorescence and scanning electron microscopy (SEM). The surface of silica fume waste was modified using poly methyl methacrylate/butyl acrylate through emulsion polymerization to increase the interaction between silica and rubber, then consequently better dispersion in rubber matrix was obtained. The mSF waste was characterized using FT-IR spectra and transmission electron microscopy. Design/methodology/approach The investigated rubber mixes and vulcanizates were evaluated by measuring the curing characteristics, mechanical testing, thermogravimetric analysis and morphological studies (SEM). The mechanical properties of composites including tensile strength, elongation at break and modulus were estimated and analyzed. Findings The results revealed that the composites (NBR and EPDM) containing mSF as filler exhibited better rheological and mechanical properties compared to unmodified silica waste and commercial silica. The SEM analysis indicated that the mSF was homogeneously dispersed through the surface of NBR and EPDM composites. Also, results showed that (NBR and EPDM) composites exhibited remarkable improvements in tensile strength, elongation at break and hardness in the presence of mSF; they also showed an increase in the thermal stability. This means that the treatment of surface SF can improve its dispersion in rubber. Research limitations/implications Silica cannot be applied in rubber matrix without surface modification because of their incompatibility; their dispersion is not good without surface modification. Practical implications The modified silica surface is considered as effective reinforcing filler which can replace other fillers because of its lower surface energy and enhanced intercalating behavior in rubber. Social implications This study is just a start in establishing rubber projects with wide applications in the industry and providing a cheap local product while preserving the quality and that is the use of factory waste, which helps in protecting the environment from pollution. Originality/value mSF is cheap with relatively high purity, which make rubber/mSF composites appear as new grade of material that can be used in different media rather than rubber.

The effect of silane type on mechanical properties and fogging phenomenon of lamp socket rubber

Bis-(3-triethoxysilylpropyl) tetrasulphide (TESPT) and 3-mercaptopropyltrimethoxysilane (MTMO) were used as silane coupling agent for silica fume. The modified silica fume was used as reinforcing filler in ethylene propylene diene monomer (EPDM) for lamp socket rubber. The cure characteristics, rubber mechanical properties and fogging phenomenon of lamp socket rubber were investigated. Test results showed that the maximum torque (MH) and differential torque (MH-ML) increased but the minimum torque (ML), cure time at 10% and 90% decreased with the increasing of silane coupling agent loading. The comparison rubber mechanical properties of modified silica fume by TESPT and MTMO was also discussed. The TESPT showed the enhancement in rubber mechanical properties such as hardness, tensile strength and 300% modulus more than MTMO. The fogging test of lamp socket rubber by the gravimetric method used to control rubber products quality in automotive industry. The using of modified silica fume by TESPT showed the better result than MTMO due to less mass of condensable constituent.

Preliminary study on decanoic/palmitic eutectic mixture modified silica fume geopolymer-based coating for flame retardant plywood

A facile preparation of decanoic/palmitic eutectic mixture (DPEM) modified silica fume geopolymer-based hybrid coating was preliminarily studied, the effect of DPEM on its flame retardancy and microstructure was characterized by techniques including cone calorimeter (CC), TG, and SEM-EDS. The experimental results showed that the appropriate dosage of decanoic/palmitic (1:1, wt%) fatty acid was equal to 1.5 wt%, which was beneficial to form a uniform and continuous barrier layer, leading to an enhancement of flame retardant efficiency, evidenced by the result that the fire performance index (FPI) climbed from 0.14 to 0.58 s·m2·kW−1 and fire growth index (FGI) decreased from 1.97 to 0.71 kW·m−2·s−1. It determined that the incorporation of DPEM into silica fume geopolymer-based coating was an effective method to prepare an efficient and eco-friendly flame-retardant coating.

Surface Modification of Silica Fume and Adsorption Property of Pb (II) ions

In order to recycle the industrial waste, silica fume of industrial waste was modified with r-mercaptopropyltrimethoxysilane coupling agent (KH590). The adsorption of modified silica fume on lead ions (Pb2+) was studied. The structures were characterized by FTIR and X-ray photoelectron spectroscopy (XPS). FTIR showed that the surface of silica fume was successfully grafted with KH590. XPS showed that the Pb2+ adsorbed on the surface of modified silica fume with coordination Pb-S bond. The effects of reaction time, Pb2+ initial concentration, pH value and adsorbent dosage on the adsorption rate were investigated. The results showed that silica fume modified by KH590 was an efficient lead ion adsorbent and the absorption rate of modified silica fume was up to 96.7%.

Silica fume reinforced polystyrene-based composite particles used as ultra-light weight proppants in hydraulic fracturing

A new kind composite particle which could be utilized as ultra-light weight proppant was prepared via suspension polymerization in this work. The composite particles were composed of polystyrene and modified silica fume. This study indicated the composite particles had a bulk density (around 0.65 g cm−3) that is even lower than most of the commercial proppants. The pure polystyrene particles had a glass transition temperature of 130.3 °C and a crushing rate of 5.0% under the pressure of 52 MPa for 3 min. While the heat-treated composite particles had a higher glass transition temperature of 146.1 °C and a lower crushing rate of 1.0% under the same testing condition. In addition, the processes of synthesizing composite particles, procedures of heat treatment, effects of different incorporation amount and dispersion of modified silica fume in polymer matrix were systematically investigated.

The rubber damper reinforced by modified silica fume (mSF) as an alternative reinforcing filler in rubber industry

Silica fume (SF) is a by-product from the production of ferrosilicon alloy which it can be purified. The surface of SF is treated with bis (3-triethoxysilylpropyl) tetrasulphide (TESPT) to obtain modified silica fume (mSF) as reinforcing filler. FTIR and TGA results confirmed that TESPT can successfully treated onto the surface of SF. The effect of surface treatment by TESPT and mSF content on the cure characteristics and rubber mechanical properties are investigated; as compared with SF and unfilled natural rubber. Results reveal that, the mSF affects not only fast cure rate, but also improve rubber mechanical properties. Additionally, the mSF and SF are incorporated into the natural rubber to produce rubber damper and then study the rubber product performance such as static spring rate and durability property. The mSF seems effective in improving the stiffness and crack resistance of rubber damper more than SF which is due to enhancing the degree of crosslink density. It can be proved that mSF as alternative reinforcing filler in rubber industry.

A new dispersing method on silica fume and its influence on the performance of cement-based materials

Because the agglomerated silica fume can’t realize its filling effect, hydration nucleation effect and pozzolanic effect in cement-based composites, a new dispersing method on silica fume aiming to dispersing it fully is introduced. The influence of physical and chemical properties of the modified silica fume on performance of cement-based materials was investigated. In view of the presence of silanol groups and negative charges of silica fume surface, the zeta potential of silica fume surface becomes positive after reaction of silanol groups on silica fume surface and calcium ions in modification solution. The change of zeta potential generates stronger adsorption force to anionic polycarboxylate copolymer. This paper discusses in detail the effect of the modified solution with different concentrations and pH values on adsorption amount of calcium ions on the surface of silica fume, thereby the optimal modified system was determined. The optimized dispersion of the modified silica fume was characterized by infrared spectra and comparing with the result of the commercial silica fume. The performance of modified silica fume in the simulated cement pore solution was evaluated by zeta potential and adsorption amount of polycarboxylate copolymers on silica fume particles surface. Besides, laser particle distribution and SEM photos help us clarify the difference between the particle size distribution and microstructure of the modified silica fume and the commercial silica fume. Results show that zeta potential, adsorption amount of polycarboxylate copolymers on modified silica fume surface increases obviously, the homogeneous dispersion fraction of the modified silica fume in the simulated cement pore solution increases significantly. Furthermore, influence of modified silica fume on the performance of cement-based materials was evaluated. Results showed that the effects of modified silica fume on fluidity, mechanical properties, hydration heat, non-evaporable water, hydration products, pore structure and morphology of cement-based materials are optimizer than the commercial silica fume. And the Ca/Si ratio of the C-S-H gel of cement-based material containing modified silica fume is lower than that of cement-based material containing commercial silica fume.

Effect of surface modification on the compressive properties of silica fume/polyurethane composites

Abstract Silica fume was modified by a silane coupling agent (KH-550). The modified silica fume was further investigated to reinforce polyurethane (PU) composites. Unmodified and modified silica fume reinforced PU composites were prepared. Through the comparisons of Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) of unmodified and modified silica fume, the agglomerations of silica fume particles were effectively prevented as KH-550 was grafted. The compressive strength of the modified silica fume/PU composites was largely improved, because KH-550 could react with both silica fume and PU. Meanwhile, modified silica fume turned from hydrophilic to hydrophobic; a better dispersion was realized in the PU elastomers compared to the unmodified silica fume. The reinforcement effects were evaluated based on the results of a universal test machine in comparison with unmodified silica fume/PU composites.

Study on Tension and Compression Ratio and Discount Ratio of Rubber Modified Silica Fume Concrete

This paper conducted all kinds of performance testing of different rubber particle size and different dosage of silica fume rubber modified cement concrete under the condition of 10% the silicon ash content, such as: analysis research of compressive strength, splitting tensile strength, flexural strength, and pull off the pressure ratio and pressure ratio. Experimental results show that silica fume can improve rubber concrete compressive strength, splitting, bending strength, the folding ratio, adding silica fume concrete fracture pressure ratio and compression ratio are improved; the silica fume can effectively improve large brittleness and lack toughness of concrete, and improve the compactness of concrete.

Retraction: Pan, T., and Xia, K. (2012). “Micromechanical Evaluation of the Damping Behavior of Modified Silica Fume Admixed Concrete.” J. Eng. Mech ., 138(12), 1411–1419; DOI:10.1061/(ASCE)EM.1943-7889.0000446

Retraction: Pan, T., and Xia, K. (2012). “Micromechanical Evaluation of the Damping Behavior of Modified Silica Fume Admixed Concrete.” <i>J. Eng. Mech</i> ., 138(12), 1411–1419; DOI:10.1061/(ASCE)EM.1943-7889.0000446

The Evaluation of Aff ection of Methylobacterium extorquens - Modified Silica Fume for Adsorption Cadmium (II) Ions from Aqueous Solutions Aff ection

The Evaluation of Aff ection of Methylobacterium extorquens - Modified Silica Fume for Adsorption Cadmium (II) Ions from Aqueous Solutions Aff ection

Retracted: Micromechanical Evaluation of the Damping Behavior of Modified Silica Fume Admixed Concrete

AbstractVibration reduction or damping capability is highly desired for structural stability when hazardous impact loads are applied to a concrete structure. Damping capability of concrete structures depends primarily on the viscoelastic response of concrete material to the magnitudes and frequencies of impact loads, which in turn requires a minimum level of stiffness and damping capacity of concrete. A common industrial byproduct material—silica fume that showed certain antishock potential when mixed with concretes—was modified with silane in this study toward improved capabilities in both stiffness and damping. To evaluate the effectiveness of the modified silica fume (MSF), a series of dynamic flexural tests and numerical analyses were conducted, of which the results are presented. A three-dimensional micromechanical model was developed based on the discrete element method (DEM), which was then employed to study the stiffness and damping behavior of the admixed concrete. A 10% usage of MSF (by weight o...

Activation of Metakaolin/Slag Blends Using Alkaline Solutions Based on Chemically Modified Silica Fume and Rice Husk Ash

This study describes the use of alkaline silicate solutions produced by mixing silica fume (SF) or rice husk ash (RHA) with aqueous NaOH, as alternative silica-based activators for metakaolin (MK)/slag (GBFS) blended binders. Pastes prepared with these activators show similar trends in mechanical strength development as a function of activation conditions compared with the pastes obtained using commercial silicate solutions as activator. All activating solutions promote higher compressive strength development with increased contents of GBFS in the binders, which promotes the coexistence of aluminosilicate reaction products along with calcium silicate hydrate gel. Higher-silica binding systems prefer a higher GBFS content for optimal strength development compared to those with a lower overall SiO2/Al2O3 ratio. SF-derived activators give reaction products which are very similar to those obtained using commercial silicate solutions, as a consequence of the high reactivity of this precursor, supplying high concentrations of Si to the systems since the early stages of reaction. RHA-derived activators appear to have slightly delayed Si availability due to the less-reactive character of this precursor, which influences the relative rates of formation of the two types of gel in blended systems. These results show that activation of GBFS/MK blends with by-product derived silicate-based activators can generate mechanical strengths and structures comparable to those obtained using commercial silicate solutions.

Functionalized Silica Fume for Chromium (VI) Removal from Wasterwater

Chemical modified silica fume by polyaniline was studied as a sorbent for removal of chromium (VI) determined by flame atomic absorption spectrometer. TEM analysis confirmed that the mean diameter of silica fume before and after treatment was of the order of 120 nm. The functionalized nanoparticles showed an extremely high efficiency towards chromium (VI) in the pH range of 4-5. Adsorption of chromium (VI) from water using functionalized silica fume was both a simple and efficient approach compared to the traditional adsorbents from the angle of integrated utilization of the secondary resources.