Use Of Silica Fume Research Articles

Lime-based mortars with added silica fume and bioproducts for restoration and preservation of heritage buildings

Restoration of heritage buildings requires an appropriate choice of materials, as inappropriate materials can lead to degradation rather than preservation. Hydrated lime and sand mortars are the most suitable for masonry cladding. However, they have low durability regarding current requirements. This work investigates the use of silica fume and/or biopolymers (egg albumen and additive derived from the reuse of milk unfit for human consumption (complexes of whey protein with κ-casein) in producing these mortars. Some mortars were characterized by mechanical properties (compressive and diametric strength, absorption rate) and chemical properties (SEM, Infrared spectrum). The research revealed that silica fume addition allows an increase of more than 50% in the mechanical strength of the mortars when associated with animal protein. The value may be higher than 60%, especially for biopolymers (complexes of whey protein with κ-casein). Finally, the proteins in the mortar mixture provide intense air entry that results in the formation of more pores. This increase in voids allows more CO2 to enter, directly contributing to a faster carbonation process and performance mortar.

Durability Enhancement Effect of Silica Fume on the Bond Behavior of Concrete-PCM Composites under Environmental Conditions.

The long-term performance of the concrete-polymer cement mortar (PCM) interface under environmental exposure is crucial to the safety of the PCM overlaying method as the environmental exposure of the repaired structures caused further degradation of the interface, leading to a significant reduction in intended service life. This study investigates the durability enhancement effect of silica fume of the concrete-PCM interface, considering an individual action of elevated temperature (e.g., 60 °C) [constant (short and moderate duration) and cyclic conditions] and moisture content [continuous immersion and wetting/drying (W/D) cycle]. Our previous research confirmed that the use of silica fume forms more C-S-H with strong binding force and enhances the interfacial bonding strength due to the denser microstructure at the interface, and it is expected to be utilized for durability purposes under the aforementioned exposure conditions. Under all elevated temperature exposure conditions, the reduction percentage of the interfacial performance corresponding to the respective reference specimens reduced significantly with the inclusion of silica fume with overlay material. The occurrence of interface fracture at lower load and a greater number of pure interface fracture modes observed in normal PCM specimens compared to modified PCM specimens indicates a positive influence of higher adhesion with better durability of modified PCM overlay with substrate concrete. Under both conditions of moisture content, significant reduction in interfacial strength was observed in normal PCM specimens. In all cases, the reducing ratio of interfacial strength was higher in normal PCM compared to modified PCM, indicating a positive influence of silica fume under moisture content. Furthermore, silica fume inclusion shifts the fracture mode from pure interfacial fracture to composite fracture mode, indicating a positive response of silica fume to improve the resistance of interface fracture under moisture content. Conclusively, the use of silica fume improves concrete-overlay layer adhesion and enhances the bonding durability under environmental exposure.

Sustainable predictive model of concrete utilizing waste ingredient: Individual alogrithms with optimized ensemble approaches

Silica fume (SF) is a prominent mineral ingredient used to manufacture sustainable concrete in the construction industry. The use of silica fume as a partial substitute for cement has numerous advantages, including lower carbon dioxide (CO2) excretion, more economical concrete, higher strength, and improved mechanical capabilities. As the effects of climate change continue to deteriorate, it has become crucial to create machine learning approaches with predictive capacities. Therefore, the purpose of this investigation is to develop models for evaluating the compressive strength (CS) of silica fume concrete (SF-C). This study utilizes various stand alone algorithms and modified like decision tree (DT), random forest (RF), mulilayer perceptron neural network (ANN), support vector regression. Afterwards, ensembling of the algorithms is done with bagging and boosting with adaboot to minimize the variance and biasness. To develop models, comprehensive published data is gathered containing 283 samples with superplastisizer (kg/m3), cement (kg/m3), silica fume (kg/m3), fine aggregate (kg/m3), coarse aggregate (kg/m3), and water (kg/m3) as input parameters. Moreover, statistical approaches is employed to assess the models capacity, including mean absolute error (MAE), root mean square error (RMSE), and coefficient of determination (R2). The result reveals that the ensemble approach on standalone models and modified bagging depicts robust performance with R2 > 0.9. Infact, RF gives a most accurate and precise measures with R2 = 0.95. Similarly, cross-validation measures was utilized to eliminate fitting issues and evaluate the generalized modeling technique's results. The permutation importance reveals that silica fume have major influence to its outcome. Thus, uitlization of MLA in concrete industry will save time and give robust results in making an eco-friendly concrete.

Silica fume stabilized loess: Mechanical properties, microstructural evolution and environmental analysis

The stabilization of loess is gaining increasing attention due to some of its physical properties which are highly prone to trigger some geological hazards. Common stabilizers (lime, cement and fly ash) release a significant proportion of greenhouse gases during their production, so it is becoming increasingly important to find an environmentally friendly or industrial waste material to stabilize loess. Silica fume is one such industrial waste material that can be used as a stabilizer in the stabilization of loess foundations. In this work, the unconfined compression strength of samples with different silica fume contents was measured, suggested that silica fume remarkably improved the strength for the samples. Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), Scanning Electron Microscope (SEM), and energy-dispersive X-ray spectroscopy (EDXS) techniques were used to explore the microstructure and quantify the microstructural parameters through Image-Pro Plus (IPP) software to explain the variation in mechanical properties of samples with different silica fume content. The results indicated that the stabilization of the loess by silica fume consisted of both chemical and physical stabilization. Chemical stabilization was the reaction between silica fume and loess particles to produce C-S-H gels, while physical stabilization was the addition of silica fume which filled the pore volume and caused a variation in the shape and angle of the pores, thereby increasing the mechanical strength. The environmental impact of stabilizing 1 m3 of loess with a common stabilizer was studied by life cycle assessment (LCA) under similar unconfined compressed strength conditions, thus demonstrating the need to promote the use of silica fume in the loess foundation stabilization market.

Use of Silica Fume, Bentonite, and Waste Tire Rubber as Impermeable Layer Construction Materials

To avoid the potential risks associated with all hazardous wastes, it is important that containment methods are intended to prevent the migration of liquid hazardous wastes or leaks containing hazardous components. Therefore, impermeable barriers were used to prevent contamination. In this study, geotechnical tests were performed on samples by mixing rubber and bentonite with silica fume at certain percentages. The aim of the experimental studies is to evaluate the applicability of certain proportions of silica fume, rubber, and bentonite mixtures as impermeable liner material. Possible cracks in bentonite during drying are reduced by the use of silica fume. Absorption of dynamic effects that may occur on the impermeable barrier layer is achieved by adding waste rubber in a uniform size. Several geotechnical tests were performed to examine the mixed rubber and bentonite with silica fumes. Looking at the results of the whole that mixed rubber and bentonite with silica fume yielded usable results and a blend for construction of a liner.

Mechanical Activation of OPC for Lower Strength UHPC with Reduced Silica Fume Content

Ultra-High-Performance Concrete (UHPC) traditionally exhibits compressive strength exceeding 150 MPa. However, variants have been identified with slightly lesser strengths that still surpass those of standard concrete; these are termed Lower Strength Ultra-High-Performance Concrete (LSUHPC). This study focused on the strategic utilization of Ordinary Portland Cement (OPC) in LSUHPC formulation while significantly curtailing the extensive use of silica fume, which is a common practice in UHPC production. Typically, high-performance concrete, with strengths ranging from 120-150 MPa, is produced using fine aggregates, heavy doses of silica fume, superplasticizer, and fiber. Contrary to this traditional method, our research developed an LSUHPC mix design with a significantly reduced volume of silica fume. For the current research stage, the use of steel fiber was omitted. To counteract the reduction in silica fume, the OPC was subjected to mechanical grinding to enhance its particle fineness and reactivity. Additionally, a low volume of class F fly ash was incorporated into the mixture to improve its workability. This adjustment was theorized to diminish inter-particle voids, reduce the water requirement, and increase the mixture’s density. With a fixed superplasticizer dosage of 4%, the aim was to minimize the water-to-binder ratio, maintaining workability and achieving enhanced particle packing and compressive strength. Following a series of grinding, particle fineness analyses, mix design formulations, and consistency tests, it was confirmed that the strategic application of OPC, combined with fly ash and reduced silica fume levels in the LSUHPC formulation, can achieve the targeted high compressive strength. This approach opens the door for cost-efficient LSUHPC production by drastically reducing the use of silica fume.

Silica Fume Influence on Behavior of Expansive Soil

In this investigation, silica fume (SF) was used as an additive material to study its influence on the characteristics of expansive soil. The soil used in this research was prepared in a lab by mingling bentonite (50 percent by soil dry weight) with natural soil. According to (USCS), the prepared soil was classified as (CH) with a liquid limit of 67.5 percent and a plastic limit of 29.3%. Expansive soil was mixed with different percentages of (SF), (8, 9, 10, 11, 12, and 13%), and experiments were conducted for treated and untreated soil to examine the impact of (SF) on Atterberg's limits, compressibility, swelling, and shear strength parameters. The outcome of this test shows that the use of silica fume raised Atterberg's limits (L.L, P.L, and P.I) and lowered compressibility and swelling percentage, as well as shear strength parameters (c,φ), were altered by increasing the angle of internal friction (φ), and decreased the cohesion (c). From these results, it is concluded that (SF) has a positive effect as an additive material to enhance the geotechnical properties of expansive soil.

On the Combination of Silica Fume and Ceramic Waste for the Sustainable Production of Mortar

The combined use of silica fume (SF) and ceramic waste (CW) for the production of mortar is studied. Sand is replaced by 5%, 10%, 15% and 20% of CW while a fixed 5% percentage (% wt of cement) of SF is used. The results show that the best results are obtained by using silica fume and ceramic waste sand with 15% weight of sand and 5% wt of cement. With the addition of sand ceramic waste (SCW), the mortar compressive strength and density increase, while the porosity displays an opposite trend. The experimental analysis is complemented with theoretical considerations on the matrix strength and related improvements in mechanical behavior. It is shown that the agreement between the experimental values and the estimated values is good.

EVALUATION OF CURING TIME FOR MICRO CONCRETE MIXES CONTAINING SILICA FUME, NANO-SILICA AND FLY ASH

Within the scope of the study, research on the use of silica fume (SF), nano silica (NS) and fly ash (FA) together or separately in the production of micro concrete is presented. It is aimed to examine the changes in mechanical properties because of water and air curing in mixtures produced using SF, FA, and NS. While cement dosage and water/binder ratio in the mixtures were chosen as 670 kg/m3 and 0.53 respectively, the amount of SF, FA and NS was limited to 150 kg/m3 in total. In the study, samples were produced using 40x40x160 mm prism molds. All samples were divided into two different groups after 7 days of water curing and water (1st group) and air (2nd group) were applied up to 56 days. Flexural and compressive strength tests were performed on the water and air cured specimens for 7-56 days and 28-56 days, respectively. In addition, the porosity and unit volume weight values of the samples were examined. The results show that both flexural and compressive strengths of micro concretes increased after 28 days thanks to water curing.

PENGARUH SILICA FUME SEBAGAI BAHAN TAMBAH TERHADAP KARAKTERISTIK BETON MUTU TINGGI

High-strength concrete is concrete with special characteristics that ordinary concrete does not have. High-strength concrete can be defined as concrete with one or more characteristics, such as small shrinkage, low permeability, high elastic modulus, or high compressive strength. Silica Fume (SF) is used as an additive material in concrete mixtures. Silica fume is a waste product of silicon metal or ferrosilicon alloy and have a silica content (SiO2) that is very high at 93.09%. In this research, an analysis of the use of silica fume as a cement additive for high-strength concrete will be carried out with variations in silica fume of 0%, 2.5%, 5%, 7.5%, 10%. With a mixture of added material in the form of a superplasticizer (Consol SS-74) with a percentage of 0.4%. From the results of the research conducted, the highest compressive strength of concrete value is obtained at a percentage of 5% both at the age of 7, 14, and 28 days in a row the value is 43.4 Mpa, 46.3 Mpa, and 55.8 Mpa.

Sulfate soil stabilisation with binary blends of lime–silica fume and lime–ground granulated blast furnace slag

The use of silica fume and ground granulated blast-furnace slag (GGBS) as a precursor to lime has been proven to be an effective sulfate soil stabilisation technique. However, which precursor is superior, in terms of both strength and swelling, is still questionable. Accordingly, the binary blends of lime–silica fume and lime–GGBS were separately added to pure kaolin soil and sulfate-dosed kaolin soil at a fixed combination dosage of 3L7S and 3L7GGBS. Then, a multi-scale investigation including unconfined compression strength (UCS), linear expansion, derivative thermogravimetric (DTG), X-ray diffraction and scanning electron microscopy (SEM), was performed to assess their performance. The engineering tests indicated that the binary blends of lime–silica fume and lime–GGBS are effective in the stabilisation of non-sulfate and sulfate-dosed soil, with the former being superior in terms of the expansion and the latter being superior in terms of UCS. This disparity in performance is partly attributed to the higher calcium oxide content of 3L7GGBS which induces a relatively higher amount of ettringite, and partly due to the higher pozzolanic activity of silica fume which accelerates the consumption of lime and restricts the formation of ettringite on the expense of fabric modification.

Strength Study on Green Concrete

Abstract: In this study, silica fume, which is finer than cement and used to substitute cement, gave concrete structures more strength and longevity. Steel fibres are utilised to improve the ductility and strength of concrete. 50% of the coarse aggregate was replaced with the 50% demolition waste aggregate. Cement with varying amounts of silica fume added (5, 10, 15, and 20%). For hardened concrete, strength tests are carried out at 7 and 28 days to assess the strength, such as compressive and split tensile. Increasing the strength parameters was made possible by the partial replacements of 10-15% of the combined use of silica fume and fly ash.

Effect of Temperature on Mechanical Behavior of Concrete Reinforced with Different Types of GFRP Bar.

Glass fiber reinforced polymer (GFRP) bars have been increasingly used as reinforcement in concrete structures. However, when the bars are exposed to high temperatures, there is a change in the internal structure of the polymer which affects the tensile strength of the matrix and its adhesion with the fibers, reducing the mechanical strength of the bar. In addition, with increasing temperature, the bar-concrete interface is also damaged by the decomposition of hydration products from the cement paste and the loss of surface adhesion. The intensity of these changes is associated with the type of resin used as a matrix since each polymer has its own molecular structure that provides a greater or lesser ability to resist the changes imposed by temperature. The present study evaluates the mechanical behavior of reinforced concrete containing different types of GFRP bars and subjected to temperatures of 150 °C, 300 °C, and 350 °C. The GFRP bars with three types of matrices (polyester, vinyl ester, or epoxy) were mechanically evaluated under tension in two conditions: isolated and inserted into reinforced concrete specimens with a thickness of 20 mm, using two types of concrete (with and without silica fume). Degradation mechanisms at the bar/concrete interface were evaluated using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), differential thermal analysis (DTA), and bond techniques. The results showed that the type of matrix has a significant influence on the tensile behavior of GFRP bars, with the epoxy matrix showing the best performance, followed by bars with vinyl ester and polyester matrix resins. The use of silica fume improved the performance of the concrete coating and, consequently, improved the protection of GFRP bars, hindering the diffusion of oxygen and heat; bar/concrete adhesion was compromised by thermal degradation of GFRP bar ribs.

Performance Assessment of Pervious Concrete Road on Strength and Permeability by Using Silica Fume

Abstract: Pervious concrete is most sustainable material become more popular due to having some extra ordinary characteristics like permeable concrete, no fine concrete and many more. Pervious concrete is a concrete which allows water pass through its surface due to presence of voids. Generally pervious concrete is made using cement, coarse aggregates, no or little fine aggregates, water and admixture. Pervious concrete can be used for low volume roads, parking lot, tennis court, sidewalk areas etc. As the concrete have high porosity, it has low strength as compared to impermeable concrete. In order to increase the strength some cementitious materials like- Silica fume, fly ash, Metakaolin etc. are used. Silica fume is a high density, high strength and durable cementitious materials which allow to increase strength in pervious concrete. Here the aim of the study is to improve performance of permeability, strength and abrasion resistance of pervious concrete by using silica fume at different percentage. Here a high-performance pervious concrete develops using cement 43 grade, silica fume, different size of coarse aggregate, little fine aggregates, water, superplasticizer (Rheoplast). To achieve higher and better strength and permeability partial replacement of silica fume by cement is done by 0%, 4%, 8%, 12%, and 16%, various sand percentage like- 5%, 7% and 9% with a fixed water cement ratio 0.35. This paper represents a detailed overview of experimental study on compressive strength, split tensile strength, flexural strength and cantabro abrasion resistance test at 7, 14, 28 day. The test result exhibited that use of silica fume in pervious concrete have improve the compressive strength, abrasion resistance and did not have detrimental change on permeability.

Effects of Silica Fume Purity on Behavior of Ultra-High Performance Concrete

Abstract The use of silica fume in high-strength and ultra-high performance concretes has been studied from many perspectives including optimum replacement rate, implications on late-age strengths, and rheological properties. However, the effects of silica fume purity (e.g., silicon dioxide [SiO2] content) are not nearly as well documented, especially when shorter duration curing regimes at higher temperatures are utilized. In this paper, four silica fumes with varying SiO2 contents were used to quantify the effects of SiO2 purity in silica fume on the behavior of ultra-high performance concrete. Several variables were evaluated to determine if changes in SiO2 content significantly influenced properties of interest. Overall, silica fume purity had the most impact on thermal set time, maximum temperature generated during hydration, and compressive strength. Thermal set time values differed by over 7 h, and maximum temperatures differed by 7°C. After one day of room-temperature curing, compressive strength varied by 50 MPa, and elastic modulus varied by 14 GPa. When specimens were cured at elevated temperatures for short durations of time (e.g., one to six days), fc values ranged from 35 to 47 MPa.

PRODUCTION OF LOW-COST SELF-CONSOLIDATING CONCRETE (SCC) USING MANUFACTURED AGGREGATES

Limitations to the sources of aggregates and the unavailability of sand is becoming a problematic issue for concrete production. A novel technology of manufactured aggregates can produce well graded round aggregates that can substitute natural aggregates while maintaining the same characteristics needed and preserving the resources. Self-Consolidating Concrete (SCC) using manufactured aggregates is assessed in this experimental work to understand the variability of workability properties and mechanical properties with the changes in w/c ratio and percentages of Coarse Aggregates and Manufactured Sand to Natural Sand in order to choose the best mixture that satisfies an adequate overall performance. Targeting compressive strength improvement, the SCC mixes included the use of Silica Fume (SF) and Polycarboxylate Superplasticizer which exhibited a strength improvement when compared to normal SCC. After performing 6 different trial mixtures, the use of manufactured rounded aggregates of percentages 73% from total fine aggregates proportion, 2.7% of Polycarboxylate superplasticizer, and around 8% Silica Fume (SF) from total cementitious materials can succeed in reaching high strength concrete with optimum mechanical properties and a noticeable workability improvement when compared to natural aggregates.

Eco-friendly concrete pavers made with Silica Fume and Nanosilica Additions

The present research analyzes the influence of the use of silica fume and nanosilica particles as a
 partial substitute of cement on the physical-mechanical properties of concrete pavers. For this purpose, silica fume was replaced with rates of 5%, 10%, and 15%, and nanosilica in percentages of 1%, 1.5% and 3% by cement weight, and in a final stage a combination of both materials with percentages of the optimal results obtained for each one. The use of 15% of silica fume, 3% nanosilica and the combination of both materials, resulted in an increase in compressive strength by 28%, 12% and 23%, respectively in comparison with the control mix. In addition, it was understood that the simultaneous use of these materials positively influences the qualities of concrete as well as its single use. The concrete pavers with optimal percentages and their combination, subjected to the tests established in the NTE INEN 3040: 2016 standard, obtained very satisfactory results. Finally, it was concluded that the additions of silica fume and nanosilica particles in substitution of cement, allows to obtain concrete pavers with better performance both for mechanical resistance and durability and constitute a viable alternative for the manufacture of a new type of concrete pavers that contributes to reuse of alternative materials, by-products of industrial processes, generating an environmental benefit.

Basalt fiber-reinforced foam concrete containing silica fume: An experimental study

Foam concrete refers to a type of low-density concrete that is commonly known to have favorable insulation and thermal performance due to its intentionally increased porosity. However, foam concrete is known to generally have a very low physico-mechanical and durability performance mainly due to its high porosity and the connectivity of the pores that can allow the entrance of unfavorable substances into the concrete medium. As a result, most often, foam concrete is considered inapplicable to major load bearing structural elements. To counter this tendency, this study adopted the use of basalt fibers with silica fume to increase the structural integrity of foam concrete. In that respect, 18 mixes with varying content of foaming agent, basalt fiber and silica fume have been prepared. Apparent porosity, water absorption, compressive, flexural and splitting tensile strength, sorptivity, ultrasonic pulse velocity (UPV), drying shrinkage, freeze–thaw, thermal conductivity, and thermal resistance tests were performed to evaluate the physico-mechanical, durability, and insulation properties of the produced foam concretes. Based on the results, a highly durable foam concrete with a maximum compressive, flexural and splitting tensile strength of ∼ 46, 6.9 and 3.07 MPa, respectively, has been developed. Furthermore, it is observed that the inclusion of silica fume can significantly influence the pore network and enhance fiber-paste matrix. The effect of basalt fiber, however, is found to be more dependent on the use of silica fume, potentially due to its low integration with cementitious paste. The results of this study are significant and point out to the great potential for producing a highly durable and lightweight insulating foam concrete through the use of basalt fiber and silica fume.

Rheological Behavior of High-Performance Shotcrete Mixtures Containing Colloidal Silica and Silica Fume Using the Bingham Model.

There have been numerous studies on shotcrete based on strength and durability. However, few studies have been conducted on rheological characteristics, which are very important parameters for evaluating the pumpability and shootability of shotcrete. In those studies, silica fume has been generally used as a mineral admixture to simultaneously enhance the strength, durability, pumpability, and shootability of shotcrete. Silica fume is well-known to significantly increase the viscosity of a mixture and to prevent material sliding at the receiving surface when used in shotcrete mixtures. However, the use of silica fume in shotcrete increases the possibility of plastic shrinkage cracking owing to its very high fineness, and further, silica fume increases the cost of manufacturing the shotcrete mixture because of its cost and handling. Colloidal silica is a new material in which nano-silica is dispersed in water, and it could solve the above-mentioned problems. The purpose of this research is to develop high-performance shotcrete with appropriate levels of strength and workability as well as use colloidal silica for normal structures without a tunnel structure. Thereafter, the workability of shotcrete with colloidal silica (2, 3, and 4%) was evaluated with a particle size of 10 nm and silica fume replacement (4 and 7%) of cement. In this study, an air-entraining agent for producing high-performance shotcrete was also used. The rheological properties of fresh shotcrete mixtures were estimated using an ICAR rheometer and the measured rheological parameters such as flow resistance and torque viscosity were correlated with the workability and shootability. More appropriate results will be focusing on the Bingham model properties such that the main focus here is to compare all data using the Bingham model and its performance. The pumpability, shootability, and build-up thickness characteristics were also evaluated for the performance of the shotcrete. This research mainly focuses on the Bingham model for absolute value because it creates an exact linear line in a graphical analysis, which provides more appropriate results for measuring the shotcrete performance rather than ICAR rheometer relative data.

Mix Design and Engineering Properties of Fiber-Reinforced Pervious Concrete Using Lightweight Aggregates

The main purpose of this study was to investigate the mix design and performance of fiber-reinforced pervious concrete using lightweight coarse aggregates instead of ordinary coarse aggregates. There were two main stages in the relevant testing work. First, the properties of the matrix were tested with a rheological test and then different amounts of lightweight coarse aggregate and fine aggregate were added to the matrix to measure the properties of the obtained lightweight pervious concrete (LPC). In order to greatly reduce the experimental workload, the Taguchi experimental design method was adopted. An orthogonal array L9(34) was used, which was composed of four controllable three-level factors. There were four test parameters in this study, which were the lightweight coarse aggregate size, ordinary fine aggregate content, matrix type, and aggregate/binder ratio. The research results confirmed that the use of suitable materials and the optimal mix proportions were the key factors for improving the mechanical properties of the LPC. Due to the use of silica fume, ultrafine silica powder, and polypropylene fibers, the 28-day compressive strength, 28-day flexural strength, and 28-day split tensile strength of the LPC specimens prepared in this study were 4.80–7.78, 1.19–1.86, and 0.78–1.11 MPa, respectively. On the whole, the mechanical properties of the prepared LPC specimens were better than those of the LPC with general composition.