Substitution Of Silica Fume Research Articles

Effect of silica fume substitution by limestone powder and cement kiln dust on the shrinkage, durability, and sustainability of UHPC.

Silica fume is usually used in UHPC, three times more than that for normal concrete, to enhance mechanical properties and durability. However, silica fume (SF) is an expensive material and has high production costs. This work is aimed at investigating the shrinkage and durability performance of previously developed UHPC mixtures utilizing the two calcareous waste materials, namely limestone powder (LSP) and cement kiln dust (CKD), by partially replacing the silica fume. The optimally selected mixtures of UHPC, having flow and strength above the minimum required, were used for detailed investigation in terms of shrinkage and durability characteristics. The results showed that by replacing SF with up to 20% of LSP and up to 20% of CKD, the mechanical properties of UHPC remained satisfactory compared to the control mixture with 100% SF. However, the ultimate shrinkage was higher for mixtures incorporating LSP or CKD, indicating the need for more volume of steel fibers to compensate for the shrinkage strains. The developed UHPCs also exhibited high resistance against reinforcement corrosion and sulfate attack, making them suitable for use in aggressive exposure conditions. However, special attention needs to be paid to the CKD content, where it is recommended to limit the content of CKD to about 15% or less to control the durability performance of the UHPCs. In addition, the sustainability analysis of developed UHPC mixtures was carried out using the life-cycle assessment and eco-strength intensity index. The results indicated that the UHPC mixtures possess a higher life-cycle and are therefore more sustainable.

Low-alkaline activated construction and demolition waste-based geopolymers

This paper focuses on the development of environmentally friendly, easy to use and cost-effective construction and demolition waste (CDW)-based geopolymer mortars activated solely with low-alkalinity NaOH and along with large share of recycled concrete aggregates (RCAs). The low-activity CDW-based precursors used in this study included brick waste and concrete waste. Additionally, slag and silica fume were utilized as industrial waste-based precursors to provide additional sources of Ca and Si, promoting enhanced geopolymerization. NaOH was utilized at molarity levels of 4, 5, 6, 7, and 8 M. The study employed a comprehensive test methodology, enabling a thorough investigation of the different properties and performance of the geopolymer mixtures, ultimately achieving the goals set for this research. The results indicated that the 4 M NaOH concentration was insufficient for early strength development of CDW-based geopolymer systems, although it eventually provided adequate alkalinity for strength development at later ages (e.g., compressive strength of 7.2 Mpa at the end of 28-day). While higher NaOH concentrations generally improved performance, the optimal choice was found to be 5 M NaOH. Nevertheless, 100% CDW-based geopolymer mixtures activated solely with low molarity NaOH solutions showed lower performance (compressive strength of 10.5 Mpa and flexural strength of 2.3 Mpa at the end of 28-day) and were found to be susceptible to water ingression and unable to withstand freeze-thaw cycling. Incorporation of slag significantly enhanced the mechanical and durability properties of CDW-based geopolymer regardless of alkaline content. The inclusion of coarser RCAs (0–4.75 mm) and a higher amount of finer RCAs (0–2 mm) resulted reduction in the performance of the mixtures. Nevertheless, the observed negative impacts were mitigated through 5% silica fume substitution. The findings of the study indicate that low-alkaline activated CDW-based geopolymer mortars can achieve an impressive compressive strength of 24.9 MPa and flexural strength of 4.7 Mpa along with superior durability performance.

Effect of alternative silicon sources on alkali-activated carbon steel slag binder and silicon sources substitution mechanism

The high cost and carbon footprint of conventional alkali activator (sodium silicate) limit the wide-scale adaptation of alkali-activated materials. During the production of sodium silicate(SS), carbonate and silicate need to be calcined at 1400 °C, which is not environmentally friendly. In order to improve the sustainability of the activator, 10% SS was reduced in this paper. The effect alternative silicon sources (ASS) on the mechanical properties of alkali-activated carbon steel slag (CSS) prepared at room temperature were studied when the modulus is 0.5 and 1.0, and the mechanism of silicon source substitution was discussed by means of microscopic characterization. The substitution amount of ASS was 10% of the total CSS amount. ASS included waste glass powder (WGP), rice husk ash (RHA), diatomaceous earth (DE), diatomaceous earth analytical reagent (DEAR), and silica fume (SF). Microscopic characterization methods included X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetry and differential thermogravimetry (TG-DTG), and scanning electron microscope-energy dispersive spectrometer (SEM-EDS). The results show that the effect of ASS depended on the structure of SiQn, and is affected by the initial modulus of the activator. The compressive strengths of the low modulus samples are lower than that of the high modulus samples, while the effect of silicon source substitution is the opposite. However, the effect of SF is less affected by the initial modulus, and the 90d compressive strength of low modulus and high modulus differed by only 8%. 10% SF substitution can save at least 48.28% of industrial SS. SF is an economic and effective ASS, which can provide a better ecological choice for the production of alkali-activated CSS cementitious materials.

Investigation On Mechanical Properties of Silicafume Blended High Strength Concrete

The study of the mechanical properties of high performance concrete mixed with silica fume aims to study the effect of adding silica fume as a partial replacement of cement on grades M60, M70 and M80 of high performance concrete.In this study, silica fume was the cement and the resulting concrete was tested for compressive strength and splitting tensile strength. The results show that the 15 percent substitution of silica fume significantly improved the mechanical properties of concrete.It is observed that as the curing time increased, the values for compressive strength and splitting tensile strength are increased. It is concluded that the optimal proportion of silica fume contributed significantly to the strength of high-strength concrete.

Effect of Human Hair Fibers on the Performance of Concrete Incorporating High Dosage of Silica Fume

Sustainable development in structural materials is currently getting attention all around the world. Solid waste, building and demolition waste, natural resources, and their reuse are the most obvious strategies for achieving sustainability in the construction industry. Solid waste human hair fiber (HHF) with a diameter of 70 µm and a length of 30–40 mm is used as a fiber, having a dosage of 0%, 1%, 1.5%, 2%, 3%, 4%, and 5%, while silica fume (SF) with a dosage of 0%, 5%, 10%, 15%, 20%, 25%, and 30% is used as a cement substitute. A drop of 50 mm to 75 mm slump was witnessed for the water–cement ratio used in the M20 mix design of concrete. The concrete’s mechanical properties, such as compressive, split tensile, and flexural strength, were determined after 28 days of water curing. The concept of the response surface methodology (RSM) for optimizing human hair fiber concrete (HHFC) and SF substitution was used, which was validated by the polynomial work expectation. The model is statistically significant when the fluctuation of the analysis of variance (ANOVA) is analyzed using a p-value with a significance level of 0.05. The test results showed that the use of 2% human hair as fiber and 15% SF as a cementitious additive or cement replacement considerably improved the strength of concrete. The compressive, flexural, and split tensile strengths of HHFC improved by 14%, 8%, and 7%, respectively, which shows the significance of human hair and the partial replacement of cement with SF. Moreover, SEM analysis was carried out to study the microstructure of the concrete matrix.

Properties of One-Part Alkali Activated Ground Granulated Blast Furnace Slag Using Slaked Lime as Alkali Activator – A Comparative Study with Different Silicate Sources

The paper reports the results of investigating the prospect of using slaked lime as a solid activator to activate the ground granulated blast furnace slag (GGBFS) with micro-silica as an additive. The results of the above-mentioned one-part mix are compared to that of GGBFS activated with solid sodium silicate in combination with slaked lime and quick lime, discretely. The compressive strength is found to be comparable to that of slaked lime and sodium silicate activated GGBFS; the silica fume substitution is recommended at 10% with 5% slaked lime. The main hydration products are C-S-H and C-A-S-H. Although the setting is delayed, strength development is acceptable with curing at ambient temperature. The microstructural analyses conducted through Field emission gun scanning electron microscopy (FEGSEM) and X-ray diffraction (XRD) are in good correlation with the results obtained for strength development.

Investigation of mechanical and durability properties of sustainable high-strength concrete

The surge in production of cement due to the rapid growth of the construction industry has an adverse effect on the environment globally caused by the huge amount of carbon dioxide emission. To produce an environment-friendly concrete, this study investigated the effective contribution of silica fume on the various mechanical and durability characteristics of high-strength concrete. In this regard, the incorporation of silica fume was carried out with progressive proportions of 0, 5, 10, 15, 20, 25 and 30% by weight of cement constituting various concrete mixes – namely, CM, SF05, SF10, SF15, SF20, SF25 and SF30, respectively. The mechanical and durability properties of concrete improved with the incorporation of silica fume up to 15% replacement. However, excessive replacement of silica fume has an adverse effect on the mechanical and durability properties of cement due to the dilution effect on cement. Similarly, in terms of mechanical characteristics, the proposed 15% substitution of silica fume resulted in the highest compressive and flexural strengths with respect to those of CM. The maximum reduction in strength loss with respect to that of the control mix was 41.17 and 28.04% for sulfuric and hydrochloric acids due to the formation of a densified microstructure.

Rheological, mechanical and durability properties of self-compacting mortars containing basalt powder and silica fume

This study investigates the durability and mechanical performance of self-compacting mortars (SCMs) produced with basalt powder and silica fume. The novelty of the study lies in the use of both basalt powder and silica fume in the production of SCMs and investigating the sulfate resistance of the produced mortars. Different percentages of basalt powder (5%, 10%, 15%, 20%, 25%, 30%, 35% and 40%) and 10% of silica fume were used as a partial substitution of Portland cement. Mini slump-flow diameter and viscosity tests were carried out to evaluate the fresh properties of SCMs. Experiments were carried out to determine the effect of basalt powder and silica fume substitution on the mechanical properties, sorptivities, densities, water absorptions and sulfate resistances of the mortar specimens. Microstructural deteriorations after immersion in 10 wt% MgSO4 solution were analyzed by Fourier transform infrared spectroscopy. The experimental study indicated that the combined use of basalt powder and silica fume resulted in an improvement in strength. It was found that the long-term mechanical properties of SCMs containing up to 10% basalt powder were satisfactory. It was observed that the use of basalt powder had a positive effect against sulfate attack.

Workability and Strength between Poly vinyl Alcohol (PVA) and Silica Fume (SF) with Portland Composite Cement (PCC) in Cement Mixture

This paper discusses the influence of polyvinyl alcohol (PVA) and Silica Fume (SF) Portland with Composite Cement (PCC) on the workability and strength. The influence of polyvinyl alcohol (PVA) and silica fume (SF) as an addition on the properties of normal concrete containing different volume of polyvinyl alcohol (PVA) has been investigated. The first which is very often used is by adding PVA with Portland Composite Cement (PCC). The second which is recent trend is to process SF and blending it with Portland Composite Cement (PCC). Silica fume is the most common pozzolan used in the formulation of cellulose and PVA as a hydrophilic polymer is water soluble and is the largest volume synthetic resin produced in the world. Strength parameters are compared of both the types of materials. The effects of PVA and SF substitution on compressive strength were evaluated and both experimental details and preliminary results are presented. For the same target strength of the concrete cubes SF blended with Portland Composite Cement (PCC) proved to be more economical than PVA-PCC.

Mechanical and durability properties of self-compacting concrete with recycled concrete aggregate, silica fume and nanosilica

The current study addresses the effect of substitution of silica fume and nanosilica on the mechanical and durability properties of self-compacting concrete containing recycled coarse aggregate (RCAs). A self-compacting concrete (SCC) was prepared by the incorporation of silica fume and nanosilica as a replacement of cement. Two series of concrete mixtures were prepared in the laboratory. In these series, RCAs with the replacement of 25%, 50%, 75%, and 100 % respectively were used with and without supplementary cementitious materials (SCMs). J-ring and Slump flow tests were conducted to investigate the fresh properties SCC. The incorporation of supplementary cementitious materials enhanced the properties of SCC and the result showed that the use of these cementitious materials can reduce water absorption and chloride diffusion up to a great extent. The mechanical and durability properties of SCC were determined by different tests like compressive strength test, water absorption test, and rapid chloride migration test. The use of cementitious materials showed a better result after 90 days of compressive strength. The test results indicate that silica fume and nano-silica were very effective and have great resistance against chloride diffusion.

Effect of mineral admixture on the properties of engineered cementitious composite

Engineered cementitious composites are a new kind of fiber-reinforced cementitious composite that exhibits superior performance. They may be used to reduce maintenance and repair costs, extend the service life of buildings, and overcome ordinary concrete's lack of bendability. The purpose of this study was to determine the effect of replacing cement with up to 10% silica fume on the characteristics of Engineered Cementitious Composites concrete with a binder concentration of 1000 kg/m3 and two kinds of fiber (steel and carbon). Numerous experiments were conducted to determine the behavior of Engineered Cementitious Composites concrete, including compressive strength for (cubes and cylinders), tensile strength for splitting, flexural strength, and load-bearing capacity (when slabs at simply supported and fixed). The experimental findings indicated that up to 10% substitution of silica fume for cement increased the compressive strength of this kind of concrete after 28 days. Other parameters such as splitting tensile strength, flexural strength, and load-bearing capacity exhibited the similar pattern.

Mechanical Properties of Ultra-high Performance Concrete Reinforced by Glass Fibers under Accelerated Agin

Ultra-High Performance Concrete (UHPC) is a cementitious composite with fine aggregates and a homogeneous matrix with high compressive strength and excellent durability against aggressive agents. It is common to use short steel fibers in the UHPC. Besides, using steel fibers considerably increases the flexural ductility, durability and energy absorption. Using glass fibers in UHPC is a novel technique which improves its mechanical properties and it has the benefit of being lighter, and cheaper than steel fibers. Furthermore, glass fibers can be used for thin concrete plates for aesthetic purposes. However, glass fibers reinforced concrete is incompatible with the hydration reaction in the alkaline environment of concrete as it can damage glass fibers, so the mechanical properties of the concrete are decreased over long periods. The mechanical properties of UHPC containing glass fibers (GF-UHPC) was investigated under three regimes of normal curing, autoclave curing, and autoclave curing plus being in hot water for 50 days (accelerated aging). Besides, the substitution of silica fume by Metakaolin in GF-UHPC was studied to understand its mechanical properties after thermal curing. The results showed that after accelerated aging, the behavior of specimens become more brittle and the modulus of rupture and toughness indices of all prismatic specimens decreased, the modulus of rupture for samples containing glass fibers was 40% lower than autoclave curing results. However, the compressive strength under accelerated aging increased at least 4% in comparison to the normal curing. Replacement of silica fume with Metakaolin slightly increased the toughness with regard to flexural strength.

Porous Concrete as Non-Sand Concrete with Silica Fume Substitution for the Application of Sound Absorbing Materials in Buildings

Sound-absorbing acoustic materials are usually made of special materials which are sometimes expensive and prone to fire and do not have sufficient strength. This research offers materials that have sufficient properties for the above problems, namely by using porous concrete. This study aims to calculate the absorption values of porous concrete values. Porous concrete is concrete which does not use sand to forms a void in concrete that also might be used as a sound absorbent. The concrete then is substituted with silica fume to reach more compressive strength. The value of absorption was measured by the impedance method of two microphones. The sample was put in a tube with a diameter of 10 cm and a height of 5 cm. The proportion of samples using American NRMCA. Tests were carried out in the frequency range of 0-1600 Hz. The best sample is a sample with a 25% void ratio that could absorb sound over a long frequency range of 432-1600 Hz even though it only reaches class B. While the highest value of absorption coefficients was the sample with a void ratio of 20% which reach a value of 0.99997. The highest stiffness was achieved by 5% void concrete with a value of k= 5.8×106.

Effects of zeolite and silica fume substitution on the microstructure and mechanical properties of mortar at high temperatures

The exposure of concrete to high temperatures leads to mechanical and chemical changes, and the performance of concrete is extremely dependent on its mortar specification. In this study, the compressive and tensile strength of mortar in a temperature range of 28–800 °C is investigated in hot conditions. The microstructure characterization is examined by X-ray diffraction test, thermal gravity analysis, and scanning electronic microscopy test. To minimize the environmental impacts of cement consumption, the possibility of partial replacement of cement with pozzolans is investigated. The results indicate that partial replacement of cement with zeolite and silica fume in the mixing plan of the concrete structure exposed to high-temperature meet both engineering and environmental consideration. Furthermore, the XRD and the TGA results provide valuable information about the prediction of the order of strength and the temperature history of the concrete members. The results pave the way for a better understanding of the high-temperature behavior of pozzolanic mortars.

Study on Coupling of Glass Powder and Steel Fiber as Silica Fume Replacement in Ultra-High Performance Concrete: Concrete Sleeper Admixture Case Study

To investigate the substitution of silica fume (SF) with the coupling of glass powder (GP) and steel fiber (STF), a concrete sleeper admixture (CSA) contains SF is considered as the reference concrete admixture. The use of high SF content in CSAs has negative effects on concrete rheology. Furthermore, it decreases the extensive use of ultra-high performance concrete (UHPC) in concrete markets that can mainly be caused by the limitation in available resources and the high cost of SF production. The substitution of SF with GP is insufficient; therefore, the possibility of using the coupling of GP and STF as a SF replacement has been researched. In this regard, 0.5%, 1 % and 1.5% steel fiber by concrete volume and 5%, 10% and 15% glass powder and silica fume by weight of cement content have been investigated. It is found that concrete admixture with the coupling of STF and SF improves all the characteristics of the concrete. Additionally, the coupling effects of GP and STF are better than that of the SF and STF. Based on the synthetic consideration of the performance and cost, the combination of 10% GP and 1.5% STF is optimal in case of CSA mechanical performance.

Effect of silica fume on the compressive strength and modulus elasticity of self-compacting high strength concrete

Self-compacting high strength concrete is one of the concrete that is needed in a green construction of building. In order to improve the workability of self compacting high strength concrete with silica fume which can be applied on the green construction building is needed. This study is aimed to get the optimum percentage substitution of silica fume by 0%, 5%, 10%, 15%, and 20% of cement on the self-compacting high strength concrete. The workability of the concrete will be tested using slump flow test and L-shaped box test then compared to EFNARC requirement for self-compacting concrete. The results show that the slump flow test and L-shaped box test of the concrete comply with the EFBARC requirement. The compressive strength of the concrete tested at 28 days with substitution of silica fume of 0%; 5%; 10%; 15%; and 20% were 34.33 MPa, 36.78 MPa, 50.98 MPa, 52.82 MPa, and 36.78 MPa, respectively. While the modulus elasticity of the concrete tested at 28 days with substitution of silica fume of 0%, 5%, 10%, 15%, and 20% were 21883 MPa, 22410 MPa, 22590 MPa, 22680 MPa, and 21874 MPa, respectively. So the optimum substitution of silica fume in self-compacting high strength concrete using local quartz sand and quartz powder is 10% up to 15%.

Thermal Properties of Geopolymers with Silica Fume

Fly ash-based geopolymer is a renewable technology to minimize the use of cement in the construction field. The development was not only the use of fly ash but also the addition of other materials such as silica fume to geopolymer paste. Insulating materials is one of the examples of fly ash-based geopolymer applications. This paper examines the influence of varied activating solution of fly ash ratio and silica fume on the behavior of thermal properties of the geopolymer paste. The activating solution of fly ash ratio (A/F) was 40%, 45%, and 50%. Silica fume acts as a substitution of fly ash varied from 1%, 2%, and 4%. The activating solution was mixed with NaOH 10 M and Na2SiO3 with Na2SiO3/NaOH ratio constant at 2. Geopolymer paste was subjected to different tests such as thermal conductivity, bulk density, and compressive strength. The results showed that the geopolymer paste with substitution of silica fume had thermal conductivity, bulk density and compressive strength in the range of 0.051 to 0.932 W/m.C, 1752.457 to 1870.309 kg/m3 and 25.41 to 38.48 MPa respectively. The thermal conductivity values for all variations are below 1 W/m.C. Results from this work shows that the mixture suitable as a thermal insulation material.

Elevated temperature, freezing-thawing and wetting-drying effects on polypropylene fiber reinforced metakaolin based geopolymer composites

In this study, metakaolin-based geopolymer samples produced by substitution of silica fume and colemanite waste up to 20% were subjected to high-temperature effects at 300, 600, 900 °C, the wetting-drying effect of 5, 15 and 25 cycles and freezing-thawing effect of 56 and 300 cycles. At the end of the tests, compressive and flexural strengths, ultrasonic pulse velocity and weight changes’ results were examined. In addition to these, micro-computed tomography (CT), XRD and SEM analyses were performed to examine the microstructure properties as well as visual inspection. 5 series produced for high temperature and wetting-drying effects were also produced with polypropylene fiber. It has been observed that samples exposed to 900 °C maintained their stability. Polypropylene fiber has been shown to increase the samples’ flexural strength results compared to the non-fiber samples after exposing to high temperatures. For the freezing-thawing effect, air-entraining admixture was added to 5 series. An increase for compressive strength was seen after 56 cycles but a decrease was seen after 300 cycles. The geopolymer samples thus began to suffer the real distortion effect in subsequent cycles after the freezing-thawing effect, which contributed to geopolimerization in a sense occurring in the first 56 cycles. During the wetting-drying cycles, fluctuations were observed in the results and an increase in the compressive strength, UPV and weight changes’ results after 5 cycles, a decrease in the results after 15 cycles and an increase again in the results after 25 cycles were seen.

Automatic image analysis process to appraise segregation resistance of self-consolidating concrete

The segregation of coarse aggregate in self-consolidating concrete (SCC) can result in some defects in the long-term properties of concrete. In this study, an image processing algorithm has been proposed and implemented, using standard coding languages, to assess segregation of the SCC mixtures. This algorithm has been designed to evaluate the distribution of coarse aggregate and the average thickness of the mortar band layer of SCC. Seven mixtures containing fly ash and silica fume as partial replacements for cement were analysed. Slump, J-ring flow and compressive strength of the samples were also measured. The results revealed that an increase in fly ash replacement resulted in a higher segregation index and a higher ratio of mortar band thickness. However, substitution of silica fume caused a lower segregation index and a lower ratio of mortar band thickness. The results demonstrate that there is a high degree of correlation between the segregation index and the mortar band thickness in all the mixtures.

Optimization of Concrete Porous Mix Using Slag as Substitute Material for Cement and Aggregates

In recent years, sustainability and environmental effect of concrete became the main concern. Substituting cement with the other cementitious material without decreasing mechanical properties of a mixture could save energy, reduce greenhouse effect due to mining, calcination and limestone refining. Therefore, some industrial by-products such as fly ash, silica fume, and Ground Iron Blast Furnace Slag (GIBFS) would be used in this study to substitute cement and aggregate. This substitution would be applied on the porous concrete mixture to minimize the environmental effect. Slag performance will be optimized by trying out variations of fly ash, silica fume, and slag as cement substitution material in mortar mixture. The result is narrowed into two types of substitution. First, reviewed from the fly ash substitution effect on binder material, highest compressive strength 16.2 MPa was obtained from mixture composition 6% fly ash, 3% silica fume and 17% grinding granular blast-furnace slag. Second, reviewed from slag types as cement substitution and silica fume substitution, highest compressive strength 15.2 MPa was obtained from mortar specimens with air-cooled blast furnace slag. It composed with binder material 56% Portland composite cement, 15% fly ash, 3% silica fume and 26% air-cooled blast furnace slag. Considering the cement substitution, the latter mixture was chosen.