Ground Silica Research Articles

Integrated Techno-Environmental Analysis of Finely Ground Silica Sand in Sustainable Mortar Production

The environmental impacts of cement production are becoming more urgent concerns. This study examined the mechanical characteristics of cement when it is partially replaced with finely crushed sand. The experimental program consisted of three different levels of sand fineness of 459 m2/kg, 497 m2/kg, and 543 m2/kg, as well as four substitution ratios of 10%, 20%, 30%, and 40%. A total of thirteen combinations were formulated and then evaluated. The results demonstrated that increasing sand fineness from 459 m2/kg to 543 m2/kg substantially impacted the compressive strength (CS), increasing it by up to 30%, and increasing the substitution ratio from 10% to 40% reduced the mechanical strength by roughly 40%. An extensive techno-environmental evaluation showed that replacing cement with finely crushed sand is technically feasible and environmentally advantageous. This technique can decrease carbon dioxide (CO2) emissions by around 40%, emphasizing its ecological benefits and coinciding with worldwide initiatives to decrease the environmental impact of construction materials. In summary, this study demonstrates the advantages of improving the mechanical characteristics of cement while minimizing its ecological footprint. It suggests that finely crushed sand can be used as a sustainable alternative in cement manufacturing, promoting the use of more environmentally friendly construction methods.

Acidification in cement paste in which clinker is partially replaced with limestone or silica

This paper examines the acid resistance of cement pastes where a portion of the cement clinker is replaced with limestone (LS or calcium carbonate, CaCO3) or ground silica (GS). Specifically, the work is intended to better understand the acid resistance of ASTM C595 IL cement as compared with ASTM C150 cement. The performance of OPC, OPC + GS, and OPC + LS systems were tested in sulfuric acid baths where the pH was held constant at 2.0 and 3.0 using an automated setup that uses titration to add acid. The degradation of the cement paste was measured as a function of time. Thermogravimetric analysis (TGA) was used to quantify changes in the calcium hydroxide (Ca(OH)2) and calcium carbonate (CaCO3) contents of the paste. In addition, the flexural strength of the cement paste specimens was measured. Results indicate that the dissolved sulfate and calcium concentrations due to acidification were not noticeably different for the OPC + GS and OPC + LS mixtures exposed to the same pH. However, as expected, differences were observed between the samples immersed in the solution of pH∼2 and pH∼3 sulfuric acid with the lower pH corresponding to more severe deterioration. TGA results showed that Ca(OH)2 is more susceptible to acid attack than limestone as evidenced by the larger Ca(OH)2 and sulfuric acid consumption in samples immersed at pH∼2. The additional acid consumption that is beyond the consumption of Ca(OH)2 can be explained by the acid attack of other hydration products such as CSH and unreacted cement phases. This results in a significant B3B flexural strength loss for the samples immersed in a pH∼2 as compared to those in the pH∼3 solution. The results demonstrated that the performance of ASTM C595 IL cements was promising and comparable with ASTM C150 cements.

The effects of arsenic trioxide addition on the mechanical and geochemical properties of the cemented paste backfill

Cemented paste backfill (CPB) technology, a densified mixture of mine tailings, binding material, and water, thickens to form a non-settling paste that is transported to fill mined cavities. CPB could provide environmental advantages by preventing the release of contaminants through hydraulic binder stabilization/solidification. Up to now, only few studies have been carried out to examine the feasibility of arsenic (As) fixation within cemented paste backfills. The main objective of the current study is to assess the impacts of incorporating pure arsenic trioxide on the geomechanical and geochemical properties of cemented paste backfill. CPB samples were prepared using pure ground silica (Sil-Co-Sil®) mimicking mine tailings, general use (GU) cement, deionized water, and reagent-grade pure As2O3 at different arsenic contents (0, 5, 10, and 15%). The samples were cured for up to 28 days and unconfined compressive strength (UCS) tests were conducted after 7 and 28 days of curing. Moreover, to evaluate the geochemical behavior of the pastes, mixtures of GU cement, pure As2O3 (0–15%), and deionized water with the same proportions as the CPB samples were prepared and mixed for up to 28 days. Then, pH, EC and chemical composition of the mixtures were evaluated. Results showed that the addition of pure arsenic trioxide (as a partial substitution for pure silica) leads to a substantial decrease in the mechanical strength of the CPB samples. However, this adverse effect was more substantial for the arsenic content of 5 wt%. The strength of the As2O3-containing samples did not improve significantly after 7 days of curing and arsenic addition lowered the pH of the solutions Microstructural analysis using SEM proved the formation of some C–S–H gels that contained arsenic in their structures as well as some complex mixture of oxides for the case of the As2O3-cement mixtures.

The Viability of the Filler Barrier Effect During the DC Dry-Band Arcing on Silicone Rubber

This article investigates the filler barrier effect on suppressing the erosion of silicone rubber composites during the dc dry-band arcing, by supplementing main microfillers in silicon rubber, i.e., ground silica and micro-sized alumina trihydrate, with fumed silica and nano-sized alumina trihydrate fillers. A study framework employing simultaneous thermogravimetric-differential thermal analyses (TGA-DTAs), the inclined plane tracking and erosion test, and the dry-arc test is employed. Fumed silica in silicone rubber increases the amount of the crosslinked residue and suppresses silicone rubber depolymerization, whereas nano-sized alumina trihydrate releasing water of hydration may adversely impact the residue coherence and promote combustion. The viability of the filler barrier effect is synergistically achieved by adding fumed silica to the main ground silica filler, thereby maintaining the residue integrity. The inclined plane-tracking erosion test confirms the importance of the filler barrier effect of fumed silica in supplementing the volume effect of ground silica in the suppression of the dc dry-band arcing. These filler effects appear to mainly govern the erosion resistance, with insignificant effect shown for thermal conductivity under dc. The dry-arc resistance test is shown as a useful method to simulate a stable dry-band arcing and obtain reproducible surface erosion patterns that correlate with the outcomes of the dc inclined plane tracking and erosion test.

Theoretical and experimental study on plasma-induced atom-migration manufacturing (PAMM) of glass

Optical manufacturing plays an important role in various fields, such as optical lenses, telescopes, and laser optics. Generally, traditional optical manufacturing techniques are all subtractive processes based on the micro-shearing effect between the tool and surface protrusions. This paper reports a plasma-induced atom migration manufacturing (PAMM) process, which is a nonsubtractive finishing approach by which angstrom level surface roughness of fused silica has been successfully achieved. Inductively coupled plasma (ICP), which is characterized by high temperature and high radical density, is used as the tool of PAMM. After obtaining instantaneous plasma energy input on the fused silica surface, the peak site atoms migrate to the valley sites, thereby reducing the roughness. According to the energy minimization principle, this migration process continues until an ultra-smooth surface with reduced surface energy is formed. Atomic-scale molecular dynamics simulations were performed to clarify the microscopic mechanisms of PAMM, and experiments were conducted to verify its smoothing capability. The roughness of a ground silica surface was drastically reduced from Sa 391 nm to Sa 0.16 nm. This study demonstrates the feasibility of the PAMM as an alternative approach for atomic-level surface manufacturing.

A Comparative Analysis by Experimental Investigations on Normal and Ground Ultrafine Mineral Admixtures in Arresting Permeation in High-Strength Concrete

This paper discusses the permeation characteristics of concrete made by increasing the fineness of the conventional mineral admixtures and using them as a partial substitute for cement. Silica fume and metakaolin ground to ultrafine state and ceramic powder obtained from grinding waste ceramic tiles were used as mineral admixtures. The mixes were designed for a compressive strength of 50 MPa and were prepared for both binary and ternary blended cases. Binary blended specimens were cast, partially replacing cement with unground silica fume, ground silica fume, unground metakaolin, and ground metakaolin separately in different replacement proportions. Ternary blended mixes were prepared using ceramic powder in 4%, 9%, and 14% and with silica fume in a constant level of 1% percentage. All the cast specimens were compared against the control concrete. A deeper comparative analysis was also made by comparing the performance of specimens made with unground mineral admixtures with that of ground mineral admixtures. Various parameters such as resistance against water absorption, percentage of voids, and sorptivity characteristics were studied. It was observed that increasing the fineness helps fill up the pores, thereby improving the resistance to permeation action.

Viability of Fillers in HTV Silicone Rubber in the AC and DC Inclined Plane Tests

The viability of fillers for inhibiting the dry-band arcing damage on high temperature vulcanized silicone rubber under the critical AC and the equivalent DC voltages of inclined plane test is investigated. Alumina tri-hydrate and ground silica are employed in the study as common fillers employed in silicone rubber formulation for outdoor high voltage insulation, and thermal analysis is applied in order to understand the protective mechanisms of the fillers. Filler volume effect plays a role in improving the erosion performance, and the dilution effect of water of hydration is shown advantageous for preventing progressive (directed) erosion. Dilution effect promoted with internal oxidation is found only notable at 50 wt% alumina tri-hydrate in this study. On the other hand, alumina tri-hydrate at 10 or 30 wt% may yield a porous residue, which is conducive to thermo-oxidation (combustion) and consequently erosion. The erosion suppression effects reported for the fillers in the composites employed in this study are found less viable under the equivalent DC as compared to the critical AC voltages of the inclined plane test. This study clarifies common perceptions about the viability of fillers in silicone rubber for AC and DC outdoor insulation applications.

Fast liquid chromatography method for separation of peptides using a sub-2 μm ground silica monolith packed column.

A stationary phase based on sub-2 μm ground silica monolith particles was fabricated by in situ polymerization and applied in micro-column for separation of peptides. The sub-2 μm silica particles were obtained from monolith using sol-gel process followed by grinding and sedimentation to remove the fines. Initially, the silica monolith particles were pretreated with 3-trimethoxysilyl propyl methacrylate to attach double-bonded ligands onto the surface, then a network structure was formed onto the surface of the particle using styrene, N-isopropylacrylamide, and ethylene glycoldimethacrylate. The effect of the flow rate of the mobile phase on the separation performance was investigated. The stationary phase was characterized by field emission scanning electron microscopy, thermogravimetry, particle size distribution, and element analysis. The resultant phase was packed in glass-lined stainless steel micro-columns (2.1 mm × 50 mm) and evaluated for fast separation. An average number of theoretical plates as high as 9800 plates/column (5.10 μm plate height) was achieved for five synthetic peptides under the optimized flow rate of 0.15 mL/min. The repeatabilities of column-to-column, intraday, and interday through relative standard deviation were found better than 4%, exhibiting satisfactory repeatability of the developed micro-column for fast separation of peptides.

A Novel Framework to Study the Role of Ground and Fumed Silica Fillers in Suppressing DC Erosion of Silicone Rubber Outdoor Insulation

This paper investigates the effect of ground and fumed silica fillers on suppressing DC erosion in silicone rubber. Fumed silica and ground silica fillers are incorporated in silicone rubber at different loading levels and comparatively analyzed in this study. Outcomes of the +DC inclined plane tracking erosion test indicate a better erosion performance for the fumed silica filled composite despite having a lower thermal conductivity compared to the ground silica composite. Results of the simultaneous thermogravimetric and thermal differential analyses are correlated with inclined plane tracking erosion test outcomes suggesting that fumed silica suppresses depolymerization and promotes radical based crosslinking in silicone rubber. This finding is evident as higher residue is obtained with the fumed silica filler despite being filled at a significantly lower loading level compared to ground silica. The surface residue morphology obtained, and the roughness determined for the tested samples of the composites in the dry-arc resistance test indicate the formation of a coherent residue with the fumed silica filled composite. Such coherent residue could act as a barrier to shield the unaffected material underneath the damaged surface during dry-band arcing, thereby preventing progressive erosion. The outcomes of this study suggest a significant role for fumed silica promoting more interactions with silicone rubber to suppress DC erosion compared to ground silica fillers.

Polystyrene Immobilized Sol-Gel Ground Silica Monolith Particles Using One-Pot Reaction of Enhanced Separation Efficiency.

The stationary phase based on sol-gel ground silica monolith particles has been produced by one-pot polymerization method incorporation of styrene and ethylene dimethacrylate. First, the ground silica monolith particles were prepared by a sol-gel process followed by sedimentation. The particles were then subjected to modify with styrene ligand via one-pot polymerization, whereas ethylene dimethacrylate was used as the cross-linker. The glass lined stainless steel columns (1mm internal diameter, 150mm length) were packed with the above phase for estimation of the chromatographic performance in high-performance liquid chromatography. An average number of theoretical plates of as high as 39,300 plates/column was obtained under the optimized elution condition. The column-to-column reproducibility was proved satisfactory in separation efficiency and retention factor. The experimental results indicate that sol-gel ground silica particles prepared by an aid of one-pot modification can provide a better way for preparation of highly efficient stationary phase.

Hydroxypropyl-β-cyclodextrin encapsulated stationary phase based on silica monolith particles for enantioseparation in liquid chromatography.

Hydroxypropyl-β-cyclodextrin-encapsulated stationary phase incorporated on silica monolith particles was prepared by physical embedding, providing a new method for the development of chiral stationary phase for enantioseparation in liquid chromatography. Ground silica monolith particles of about 2.0μm were prepared via sol-gel reaction followed by differential sedimentation. Initially, the silica monolith particles were pretreated with 3-trimethoxysilyl propyl methacrylate to attach double-bonded ligands onto the surface, then a network structure was formed onto the surface of the particle using N-isopropyl acrylamide as functional monomer. Hydroxypropyl-β-cyclodextrin was encapsulated inside N-isopropyl acrylamide copolymerized layer on the surface of silica monolith particles. The effect of the amount of chiral selector on the chromatographic efficiency of the chiral stationary phase was examined. The glass lined stainless steel columns (1mm internal diameter, 300mm length) were packed with the stationary phase for estimation of the efficiency by separation of phenylsuccinic acid, oxybutynin, equol, and naproxen enantiomers in high-performance liquid chromatography, with the resolutions of 1.54, 1.72, 2.54, and 2.31, respectively. The column to column repeatabilities through relative standard deviation were found better than 3%. The experimental results indicate that the sol-gel ground silica particles modified with β-cyclodextrin provide a promising way for the separation of chiral enantiomers.

Development of ternary blended rubberized cement mortar

Abstract The production of concrete has led to a major environmental issue with the production of cement has led to an equivalent CO2 emission in to the atmosphere, which is one among the green house gases. Secondly, the production of concrete with natural aggregates is a major challenge with the mining of silica sand from the river beds has led to an enormous environmental threat. In order to overcome these issues, M−sand obtained from the quarries has led to an effective replacement for river sand. In addition, the dumping of discarded waste tire from the vehicles in the waste land has led to an environmental degradation of the land which leads to pollution. In order to effectively utilize this waste tires, these can be effectively utilized as a partial substitution for M−sand in the construction sector. Hence, this work has been framed to investigate the effect of substituting cement with industrial byproducts such as ground granulated blast furnace slag (GGBFS) and silica fume (SF) and fine aggregate with crumb rubber at various replacement levels to assess the compressive strength of the ternary blended cement mortar.

Influence of Type of Secondary Raw Material on Consistency of Fresh Mixture for AAC Production

Autoclaved aerated concrete (AAC) is, mainly in Europe, widely used construction material. It has an optimal combination of bulk density, strength and thermal conductivity coefficient for load-bearing and non-load-bearing structures of civil facilities. The production technology is based on a mixture of ground silica sand, lime, cement, gypsum, aluminium powder and additives. The grinding of sand is most often carried out in a wet way, and the sand sludge is consequently used in production technology. The aim of the experiment was verification of the effect of partial replacement of sand with the alternative raw materials in sand sludge on the rheology of the mixture. This parameter determinates how the modified mixtures affect the sludge pumpability. As a reference the consistency of the sand sludge of the normal production density of 1.65 g/cm3 was compared to the sand sludges of different density (1.60, 1.70 and 1.75 g/cm3) and with a fresh aerated concrete (FAC) mixture of 1.60 g/cm3. Then the sludges were modified by 30 % of alternative raw materials (recycled glass, coal slag, FBC ash, FBC bottom ash) as the partial weight replacement for sand. This partial replacement resulted in water/solids ratio adjustment which recommended value is 0.47 for recycled glass and coal slag, 0.59 for fluidized bed combustion (FBC) bottom ash and for FBC fly ash it is 0.70.

Fabrication of permanent silver cement frit at the inlet of micro-columns: a significant progress toward realization of disposable micro-columns

The advent of disposable micro-columns will be a hope of workers of chromatography-related laboratories. A very critical and important requirement is the formation of affordable inlet frits. Welding a metal screen to a column inlet is not recommended because of the risk of damage to stationary phase. In this study, the Tollens probe (silver mirror reaction) was adopted to make affordable frits. Silver is reduced on the particle surface and in an empty space among the particles, forming a solid silver network structure at the column inlet area by injecting the reaction solution into the packed column at a depth of one third (10 cm) of the packed bed (0.5 mm × 300 mm). The silver cement structure was successfully formed, and the silver cement frit endured mobile phase flow well when C18 modified ground silica monolith particles were used to make the packed bed. The formation of the silver cement frit was not successful when the stationary phase based on conventional spherical silica particles was used. Negligible reduction of chromatographic performance by the silver cemented frit was observed. This study serves as the first step toward realization of disposable micro-columns.

Silica-Filled Composites from Epoxidized Natural Oils

Thermosetting cast resins, filled with varying levels of silica, were prepared from epoxidized soybean oil (ESO) and epoxidized triolein (ETO) in order to study matrix-filler interactions and effects of cross-linking density on physical properties. While ESO is characterized by a highly heterogeneous composition, ETO had very regular structure but lower epoxy content. Room temperature ring opening polymerization initiated with butanediol was catalyzed by fluoroboric acid. Epoxy matrices were almost entirely made from natural oils, with cross-link densities correlated with epoxy oxygen content in the epoxidized oils. In spite of high cross-link density, glass transitions of ESO and ETO matrices were below room temperature, which was attributed partially to the plasticizing effect of “dangling chains” and side reactions (cyclization). Ground silica particles increased strength and modulus but did not shift glass transition in a predictable way. The impact of filler on mechanical properties was more pronounced in composites prepared with lower functionality ETO. These rapidly setting materials were prepared by a simple process of mixing and casting. The resulting inexpensive epoxy composites displayed relatively low polarity and low dielectric loss, particularly in the glassy state, and therefore may show utility in electrical insulation applications.

An optimized mixed-mode stationary phase based on silica monolith particles for the separation of peptides and proteins in high-performance liquid chromatography.

A phase with both hydrophobic and hydrophilic functionalities has been synthesized by modification of ground silica monolith particles with C18 and 1-[3-(trimethoxysilyl)propyl] urea ligands. A series of phases was prepared by changing the ratio of the two ligands to determine the optimal ratio in view of separation efficiency. The resultant optimized stationary phase was packed in narrow-bore glass-lined stainless-steel columns (1×300mm and 2.1×100mm) and used for the separation of synthetic peptides and proteins. The average numbers of theoretical plates (N) of 52100/column (174000/m, 5.75µm plate height) and 35500/column (118000/m, 8.47µm plate height) were achieved with the 300mm column at a flow rate of 25 µL/min (0.86mm/s) in 60:40 v/v acetonitrile/30mM aqueous ammonium formate for the mixture of peptides (Thr-Tyr-Ser, Val-Ala-Pro-Gly, angiotensin I, isotocin, and bradykinin) and for the mixture of proteins (myoglobin, human serum albumin, and insulin), respectively. Fast analysis of the peptides and proteins was also carried out at a flow rate of 0.9mL/min (6.88mm/s) with the 100mm column and all the analytes were eluted within 2 min with good separation efficiency.

Flexural-Fatigue Properties of Sustainable Pervious Concrete Pavement Material Containing Ground Tire Rubber and Silica Fume

With the development of urbanization, pervious concrete has been increasingly used in urban road pavement structures. The objective of this paper was to investigate the effect of stress levels and modifier (ground tire rubber and silica fume) on the fatigue life of pervious concrete and establish the fatigue equations with different survival probabilities. In order to improve the deformability of pervious concrete without sacrificing its strength, ground tire rubber and silica fume were added into pervious concrete. Two kinds of pervious concrete, control pervious concrete and ground tire rubber and silica fume modified pervious concrete, were made in the laboratory. The pervious concrete beam specimens of 100 × 100 × 400 mm were casted, and the static flexural strength and flexural strain of the two kinds of pervious concrete were tested. The fatigue lives of two pervious concretes were tested using MTS fatigue testing machine under four different stress levels (0.85, 0.80, 0.75, and 0.70). The fatigue life was analyzed by two-parameter Weibull distribution. The parameters of Weibull distribution were determined by graphical method, maximum likelihood method and moment method. The Kolmogorov–Smirnov test was used to test the Weibull distribution and the fatigue equations under different survival probabilities were established. The results showed that ground tire rubber and silica fume modified pervious concrete had better deformability while ensuring strength compared to control pervious concrete. The addition of ground tire rubber and silica fume improved the fatigue life of pervious concrete. The two-parameter Weibull distribution was suitable to characterize the fatigue characteristics and predict the fatigue life of pervious concrete. Fatigue equations with different survival probabilities were a good guide for pervious concrete design.

Early and Late Compressive Strengths Behaviour of Concrete with Blended South African Extenders

The use of different supplementary cementitious materials (SCMs) has attracted the interest of researchers for years. These materials have their advantages and dis-advantages. The optimal use of these SCMs in concrete may call for blending them together in concrete instead of using them individually. The blend may increase their quality as one disadvantages may be catered for by another one advantages. The present study focusses on investigating the effect of proportional combination of these SCMs on strength development. Three different South African SCMs (Ground granulated blast-furnace slag, Silica fume and Fly ash) were blended at different proportions and used as replacement of cement in concrete. Compressive strength test based on SANS 5860:2006 standard were adopted. The compressive test was performed on 16 different mixes at 7, 14, 28, 90 and 120 days curing periods. The water/cement ratio for all the mix was maintained at 0.5. The compressive strength results are desirable for each curing age at the 30% replacement of cement in which each SCM contributes 10% to the mix, greater strength value at curing age beyond 120 days compared to control sample was envisaged for this sample.

Adjusting curing parameters for innovative and durable vegetable fibre-cement composites

This work adjusts curing parameters for innovative and durable vegetable fibre-cement composites produced by a slurry vacuum dewatering process. The raw materials used for the cementitious composite mix designs applied in this investigation include: Portland cement, ground silica as an inert filler and vegetable fibre reinforcement. The curing conditions were conducted on eight sets of samples studying the effects of: initial hydration duration (10 h or 24 h); accelerated carbonation exposure (0.035% or 20% of CO2 concentration); and accelerated aging tests (before and after 200 soak & dry cycles). The mechanical properties of cementitious composites subjected to eight different curing and aging conditions, with a statistical significance increase in carbonated composite strength that is attributed to the packing density of the mixture containing an inert filler (silica quartz).The use of unbleached pulp with silica as a mineral addition in combination with 10 h of initial hydration prior to CO2 curing is indicated to improve the efficiency of the operational steps in the carbonated fibre-cement industry.

Polystyrene bound silica monolith particles of reduced size as stationary phase of excellent separation efficiency in high performance liquid chromatograhy

Ground silica monolith particles of quite smaller average size (2 μm) have been prepared by sol-gel process followed by soft grinding and calcination. Next a highly efficient chromatographic stationary phase has been prepared by reaction of those particles with (3-chloropropyl) trimethoxysilane followed by initiator attachment and modification of polystyrene by reversible addition-fragmentation chain transfer polymerization. The resultant phase of ca 3 μm particle size was packed in micro-columns (1.0 mm × 300 mm & 1.0 mm × 150 mm) to show the separation efficiencies as high as 67,600 and 35,500 plates/ column, respectively, for the separation of 5 small test molecules at a mobile phase flow rate of 25 μL/min. The 300 mm column shows a separation efficiency better than any of the commercially available conventional packed columns so far. Multiple shapes and high surface roughness as well as reduced particle size of the stationary phase of this study seem to contribute to such enhanced separation efficiency.