Addition Of Silica Fume Research Articles

Frost resistance and improvement techniques of recycled concrete: a comprehensive review

In the pursuit of sustainable construction practices, the utilization of recycled concrete has emerged as a pivotal strategy, distinguished by its commitment to resource conservation and environmental stewardship. Nevertheless, the inherent micro-porosity and micro-cracking within the old mortar of recycled concrete may lead to weak bonding performance at the interfacial transition zone, culminating in diminished strength, reduced density, and elevated water absorption rates compared to conventional concrete, which critically impairs its performance in cold climates subjected to freeze-thaw cycles. Consequently, this paper provides a structured examination of the frost resistance properties of recycled concrete subjected to freeze-thaw cycling. Initially, the study delineates the mechanisms of frost-induced damage in recycled concrete by synthesizing the degradation pathways observed in both conventional and recycled concrete during freeze-thaw exposure. Subsequently, a detailed analysis is conducted to identify the pivotal factors affecting frost resistance, encompassing the proportion and moisture affinity of recycled aggregates, the addition of silica fume and fly ash, the water-to-cement ratio, and the degree of water saturation. In the final segment, the study compiles and reviews the strategies for bolstering the frost resistance of recycled concrete, including the incorporation of air-entraining admixtures, fiber reinforcement, and aggregate modification approaches. The objective of this research is to offer a thorough comprehension of recycled concrete, with a concentration on the mechanisms of frost damage, the critical determinants of frost resistance, and interventions to augment its resilience against freezing conditions. On this basis, the present paper, in conjunction with the characteristics and current research status of recycled concrete, proposes recommendations for the application of recycled concrete in cold regions. This review is anticipated to facilitate researchers in gaining a comprehensive understanding of the freeze-thaw characteristics of recycled concrete and the measures to enhance its frost resistance. Furthermore, it aims to assist engineering and technical personnel in selecting appropriate treatment methods to improve the frost resistance of recycled concrete in cold regions, thereby promoting the practical engineering application of recycled concrete in such areas.

Study on the chloride ion binding rate of sulfoaluminate cement mortars containing different mineral admixtures

In this study, the chloride ion (Cl−) binding rate of sulfoaluminate cement (SAC) mortars containing different mineral admixtures was investigated. This is essential to improve the durability of concrete structures in high Cl− environments, especially where they are susceptible to Cl− attack such as coastlines and marine structures. The effects of Cl− concentration, curing age, and the type and amount of mineral admixture on the Cl− binding rate of SAC mortars were analyzed. It was found that the content of water-soluble Cl− in SAC mortars decreased with the increase of curing age, while the Cl− binding ratio increased accordingly, indicating that its resistance to internal Cl− permeation increased. The addition of fly ash (FA) and ground granulated blast furnace slag (GGBS) can significantly improve the Cl− binding rate of SAC mortars, and the Cl− binding rate increases to 46.6% with 20% of FA and 38.7% with 40% of GGBS. The effects of mineral admixtures on the microstructure and phase composition of SAC mortars were further investigated by X-ray diffraction (XRD) analysis. The results showed that the addition of FA and GGBS promoted the formation of C-S-H (calcium silicate hydrate) gels and improved the resistance of SAC mortars to Cl− penetration. On the other hand, the excessive addition of silica fume (SF) decreased the Cl− binding rate, whereas a moderate amount of limestone powder (LP) improved the Cl− binding rate. The study of the Cl− binding rate of SAC mortars can help to evaluate their resistance to Cl− erosion in real projects, thus guiding the optimization of concrete formulations and the improvement of durability.

Bonding performance and construction parameters of low-rebound shotcrete

Abstract Shotcrete has the advantages of short setting time, high early strength, simple process and flexible operation methods. It is mainly used as temporary support in domestic highway tunnels. This study investigates the development of low-rebound shotcrete for tunnel construction by adding silica fume and fly ash into the mixture. Sandstone and limestone were employed to simulate the surrounding rock. The workability and mechanical properties of the shotcrete were evaluated based on slump tests, rebound rates, compressive strength measurements, and bonding strength tests between the surrounding rock and the shotcrete. Furthermore, the research investigated construction techniques, with an emphasis on spraying distance, shrinkage angle, and wind pressure, and optimized these parameters for practical engineering uses. The outcomes demonstrate that the addition of silica fume enhances the mechanical properties of the shotcrete and reduces rebound. It was discovered that optimal spraying distance was between 1.2 m and 1.5 m, with the optimal wind pressure at 0.5 m, and the ideal shrinkage angle at 6°.Research on low rebound shotcrete is of great significance for improving construction quality, construction efficiency and engineering structural performance, and also meets the requirements of sustainable development.

Impact of silica fume on the long-term stability of cement-based materials with low water-to-binder ratio under different curing conditions

Silica fume is commonly employed in cement-based materials with low w/b. However, the properties evolution of low water-to-binder cement-based materials with silica fume and the impact of silica fume on the performance of paste are still unclear. In this study, the water absorption and desorption, linear deformation, and mechanical properties of low w/b pastes with varying silica fume contents cured under both lime-saturated water and drying conditions were conducted. Furthermore, the impact mechanism of silica fume on the performance of the paste was explored through measurements and analyses of the hydration process, hydration products, and crack characterization. The results show that the flexural and compressive strengths of the paste with silica fume cured under varying conditions exhibit fluctuations. This is attributed to the fact that, while silica fume diminishes expansion and expansion cracking under lime-saturated water curing, it also enhances shrinkage and shrinkage cracks. Under drying conditions, the strength fluctuations can be attributed to the refinement of the structure of the material by the addition of silica fume, coupled with increased shrinkage and cracking.

Evaluating the impact of industrial wastes on the compressive strength of concrete using closed-form machine learning algorithms

Industrial wastes have found great use in the built environment due to the role they play in the sustainable infrastructure development especially in green concrete production. In this research investigation, the impact of wastes from the industry on the compressive strength of concrete incorporating fly ash (FA) and silica fume (SF) as additional components alongside traditional concrete mixes has been studied through the application of machine learning (ML). A green concrete database comprising 330 concrete mix data points has been collected and modelled to estimate the unconfined compressive strength behaviour. Considering the concerning environmental ramifications associated with concrete production and its utilization in construction activities, there is a pressing need to perform predictive model exercise. Furthermore, given the prevalent reliance of concrete production professionals on laboratory experiments, it is imperative to propose smart equations aimed at diminishing this dependency. These equations should be applicable for use in the design, construction, and performance assessment of concrete infrastructure, thereby reflecting the multi-objective nature of this research endeavour. It has been proposed by previous research works that the addition of FA and SF in concrete has a reduction impact on the environmental influence indicators due to reduced cement use. The artificial neural network (ANN) and the M5P models were applied in this exercise to predict the compressive strength of FA- and SF-mixed concrete also considering the impact of water reducing agent in the concrete. A sensitivity analysis was also conducted to determine the impact of the concrete components on the strength of the concrete. At the end, closed-form equations were proposed by the ANN and M5P with performance indices which outperformed previous models conducted on the same database size. The result of the sensitivity analysis showed that FA is most impactful of all the studied components thereby emphasizing the importance of adding industrial wastes in concrete production for improved mechanical properties and reduced carbon footprint in the concrete construction activities. Also, the M5P and ANN models with R2 of 0.99 showed a potential for use as decisive models to predict the compressive strength of FA- and SF-mixed concrete.

Investigation of the influence of the addition of graphene oxide nanoparticles in mortars made with the addition of silica fume, marble powder and fibers from the crushing of the N95 face masks

The potential for reusing different waste in building material manufacture has been extensively explored in recent years, reducing their disposal and the natural resources consumption. The main objective of this research is to investigate the advantage of adding graphene oxide nanoparticles (GON) to a mortar made with Portland cement, sand, silica fume, marble powder, and the addition of polymeric fibers (obtained through crushing of the N-95 facial protection mask (FM)). The experimental program added 0%, 0.7%, 1.4%, 2.0% FM, and 0.02% GON (both about the cement weight) in the mortars, which were investigated for their physical, mechanical, and chemical properties. The results indicate the possibility of 0.7% FM since it has GON addition. Finally, the GON addition in mortars will allow the addition of other types of recycled polymeric fibers.

Porous concrete modification with silica fume and ground granulated blast furnace slag: Hydraulic and mechanical properties before and after freeze-thaw exposure

This study investigates the effects of incorporating silica fume (SF) and ground granulated blast furnace slag (GBFS), both individually and in hybrid combinations, on various properties of porous concrete (PC) were evaluated under room conditions and after freeze-thaw (F-T) cycles. The hardened density (HD), water permeability coefficient (k), apparent porosity (AP), as well as compressive strength (CS), splitting tensile strength (STS), and flexural strength (FS) at 7, 28, and 120 days. Additionally, the impact of SF and GBFS on the mass loss (ML), residual compressive strength (RCS), residual splitting tensile strength (RSTS), and residual flexural strength (RFS) of PC samples subjected to 30, 60, 120, and 180 freeze-thaw (F-T) cycles was analyzed. The findings revealed that the addition of SF and GBFS decreased the AP and k values of PC samples under room conditions. Furthermore, these materials significantly improved the CS, STS, and FS properties of PC samples, especially at the 28-day and 120-day marks, owing to their enhanced pozzolanic activity over time. SF and GBFS also contributed to higher RCS, RSTS, and RFS values in PC samples after F-T cycles compared to the control samples. This was due to their effective gap-filling properties and the formation of additional calcium-silicate-hydrate (C-S-H) gels within the matrix. Additionally, SF and GBFS led to slightly higher RDME values in the C1-C6 samples than in the control samples following F-T cycles. However, SF and GBFS did not have a significant impact on reducing the ML values of PC samples after F-T cycles.

Influence of fibers and bubble structure on thermal conductivity and mechanical performances of foam concrete

This study aims to effects of fibers and bubble structure on thermal conductivity and mechanical performances of foam concrete. The factors of fiber type, length, fiber dosage, and silica fume dosage were considered. The workability and compressive strength tests were carried out. The bubble structure was observed. Numerical simulation of thermal conductivity was performed. The results indicated that the influence of a single factor on the strength of foam concrete is slight. The addition of silica fume significantly reduces the workability of foam concrete. The synergistic effect of silica fume and PP fiber can improve the compressive strength of foam concrete. The compressive strength of foam concrete with good performance is 7.2 MPa, and the dry density is 827 kg/m3. The pore diameter of about 400 μm is the main pore diameter that affects the strength of foam concrete. The thermal conductivity of foam concrete with the same porosity but different pore size distribution is similar when the pores are closed. The defects on the hole wall, small aperture and uniform distribution are still conducive to improving the strength. When the profile of the same temperature passes through the pore, the curve is concave and convex first, and the larger the pore size, the more obvious this phenomenon is. The holes in the foam concrete play a role in dissipating energy during heat transfer.

A study on the mechanical performance, shrinkage and morphology of high-performance fiber reinforced concrete with varying SCMs and geometry of steel fibers

This paper investigates the effects of silica fume (SF) and metakaolin (MK) as cement substitutes on the mechanical properties, shrinkage, and toughness performances of steel fiber reinforced concrete (SFRC). Initially, a reference concrete mix with a water-to-binder ratio of 0.4 is blended with different volume fractions of steel fibers with varying geometries (crimped steel and straight steel), both individually and in combination, to examine their mechanical properties. Also, the possible influence of pozzolans on the variation of drying shrinkage and flexural toughness of hybrid steel fiber reinforced concrete (Hy-SFRC) was evaluated. An increase in workability was observed as a result of hybridization of steel fibers. Pozzolanic steel fiber reinforced concrete (SFRC) exhibited a more significant enhancement in compressive strength and flexural strength compared to non-pozzolanic SFRC. The hybrid combination of CS 1.5 % and SS 0.5 % was found to be the best in terms of mechanical properties. The addition of SF and MK reduced the shrinkage strain by up to 50 % compared to the reference mix. The flexural toughness values for both binary and ternary pozzolanic Hy-SFRC were notably higher than those for non-pozzolanic Hy-SFRC, indicating a stronger bond between the fibers and the matrix. Hy-SFRC containing a ternary pozzolanic mix of SF 10 % and MK 10 % gave the best results in flexural toughness. The results were consistent with morphology analysis, which revealed an increase in hydration products at the interface between the aggregate and concrete matrix, as well as between the steel fiber and concrete matrix, due to the ternary blending of SF and MK.

Influence of aluminum waste, hydrogen peroxide, and silica fume ratios on the mechanical and thermal characteristics of alkali-activated sustainable raw perlite based geopolymer paste

Geopolymer concretes have great potential in the sustainable construction industry in the future, as they can be produced without using cement and waste materials can be used as binders. This paper explores the use of sustainable, lightweight geopolymer pastes as construction materials using raw perlite as the primary ingredient. It achieves this by alkaline activation with additives such as waste aluminum lathe (Al), Hydrogen peroxide (H2O2) and silica fume (SF). The experiments were conducted in four groups: Al added in the 1st group, Al + Silica fume (SF) in the 2nd group, H2O2+SF in the 3rd group, and Al + H2O2 in the 4th group. Apparent density, compressive strength, flexural strength, and thermal conductivity tests were performed at 7, 14, and 28 days. SEM and EDX analyses were also conducted. The results showed that as the ratio of Al and H2O2, which have a aerating effect, increased, decrease in apparent density and strength was observed. However, when Al + SF were added together, significant improvements of 10%–20% were observed in compressive and flexural strengths, as well as apparent density. 35% water/pearlite ratio and 0.50% Al addition reduced compressive strength by 5% and lightened apparent density by 15%. At 40% water/pearlite ratio, 0.50% Al addition reduced compressive strength by 10% and lightened apparent density by 5%. According to these results, the best performance is obtained with 35% water/pearlite ratio and 0.50% Al addition Furthermore, the addition of lightweight SF resulted in good geomerization and reduced crack formation. This effect was evident in the internal structure based on SEM analysis. Interestingly, despite aluminum's overall high thermal conductivity, its incorporation into raw perlite-based pastes resulted in reduced thermal conductivity.

Effect of silica fume on the microstructural and mechanical properties of concrete made with 100% recycled aggregates

Recycled concrete aggregate can be utilized in structural concrete in order to reduce the use of natural resources and the harmful impacts of waste concrete on the environment. This present research aimed to assess the effectiveness of using recycled aggregate concrete with the partial replacement of cement by silica fume (SF) to analyze the microstructural and mechanical properties of recycled aggregate concrete (RAC). In this study, recycled stone was used as coarse aggregate. The main variables of the study included the dosage of silica fume that was employed as a partial replacement of ordinary Portland cement (OPC) with four different percentages: 4%, 8%, 12%, and 16% by weight. Five different mixes were prepared, with four mixes created by varying amounts of silica fume, which were designated as RSACSF4, RSACSF8, RSACSF12, and RSACSF16. The other mix was created as a reference mix without silica fume and designated RSACSF0. Slump test was conducted to investigate the workability of concrete mixes. From the test result, a decreasing trend was found after adding more percentage of SF. Compressive and splitting tensile tests were conducted to analyze the mechanical properties of RSAC at 7 and 28 days. The results showed that the addition of SF improved the performance of RSAC at early and later curing ages, and a 12% addition of SF showed the best result. Scanning electron microscopy and X-ray diffraction analysis were performed to explore SF's microstructural performance and effect on RSAC. The results showed that silica fume showed a positive pozzolanic impact, and when combined with calcium hydroxide, it underwent a secondary hydration reaction that boosted the generation of calcium silicate hydrate and improved the parameters of the interface transition zone. X-ray diffraction analysis showed that silica fume and silica fume have similar pattern intensities. Finally, 12% SF is recommended as a partial replacement for cement in RSAC.

Influence of silica fume addition and content on the early hydration of calcium aluminate cement – The role of soluble silicon

Hydration of a commercial white calcium aluminate cement (CAC) at 23 °C was modified by silica fume (SF) addition in varying amounts. The process was followed by heat flow calorimetry, quantitative in-situ XRD analysis and Gillmore needle experiments supplemented by pore solution analysis, thermodynamic modelling, and 1H-TD-NMR measurements. Lower SF/cement ratios accelerate the hydration of CAC. Higher ratios trigger an intermediate heat flow event, which is correlated to increased setting rates. This intermediate event (IE) initiates an induction period of constant duration, which appears later with increasing SF/cement ratios. Results show the IE is caused by an initially hindered CA dissolution, in which dissolved silicon provided by SF plays a crucial role. Increasing the [Si] concentration in the pore solution leads to a further retardation of the IE and eventually prevents the entire hydration reaction if a critical amount is reached. A detailed model explaining the observed behavior is proposed.

Compressive strength and gel structure improvement in the high-volume calcium carbide residue activated-blast furnace slag system combined with sodium carbonate and silica fume

Calcium carbide residue (CCR) with high alkalinity favorably corresponds to the alkaline activator in the alkali-activated materials (AAMs) production. Its utilization could reduce the carbon footprint and facilitate cast-in-situ applications compared to traditional liquid alkaline activators. A high-volumed CCR from 10 % to 25 % as alkaline activators in an alkali activated-blast furnace slag system was investigated, in which sodium carbonate (Na2CO3) and silica fume were used to improve the mechanical properties of CCR-activated blast furnace slag (CCR activated-BFS) pastes. Isothermal Calorimetry, X-ray diffraction (XRD), 29Si nuclear magnetic resonance (NMR), and scanning electron microscopy (SEM) were used to characterize the reaction process, phase transformation, and gel structure. The results show that the highest compressive strength of CCR activated-BFS pastes was obtained when the CCR proportion was 20 %. Na2CO3 addition significantly improved the compressive strength, especially at the CCR to Na2CO3 mass ratio at 1:1.5. However, the compressive strength deterioration appeared at 28 d because of the gel structure decomposition in CCR activated-BFS pastes. The silica fume addition inhibited the structure decomposition, improved the connectivity of gel structure, favored the formation of gel, and thus suppressed the compressive strength deterioration. The study established a sustainable waste recycling from acetylene gas production by using CCR as feedstock to mitigate carbon emissions from AAMs production.

Mineralogical and geochemical composition of a cementitious grout and its evolution during interaction with water

In the present study, the chemical composition, mineralogy, and mechanisms of alteration of a cementitious grout based on a CEM III/C with addition of smectite, hydrotalcite, and silica fume, are studied using a combination of chemical and physical methods. This material was designed in the context of geological repository of radioactive wastes, with a twofold aim: first, to fill the technical voids left by drilling operations at the interface between the geological formation and the disposal galleries. Second, to neutralize a potential acidic transient due to pyrite oxidation, and to create an environment that favors low corrosion rates of carbon steels. The grout is mainly composed of calcium silicate hydrates having a Ca/Si ratio of ~0.8, incorporating Al in the bridging site of the Si chains (C-A-S-H), and accounting for 29–36 wt.% of the sample. It also contains silica fume (38–48 wt.%), smectite with interlayer Na (11–17 wt.%), hydrotalcite with interlayer CO32− (3–4 wt.%), and lower amounts of portlandite, calcite, and possibly gibbsite and gypsum. Upon alteration by water in a flow-through reactor, the main modifications affecting the sample are calcite and gypsum dissolution, hence releasing aqueous Ca2+ that is adsorbed in smectite interlayer by replacing Na+, and stoichiometric C-A-S-H dissolution. The evolution of solution chemistry and of the solid phase composition are reproduced successfully using a thermokinetic model.

Effect of the Utilization of Lightweight Brick Wastes and Silica Fume Addition on the Concrete Compressive Strength

Effect of the Utilization of Lightweight Brick Wastes and Silica Fume Addition on the Concrete Compressive Strength

Strength Characteristics of Bentonite Nano Clay Stabilized with Addition of Lime, Fly Ash, and Silica Fume for Soil Environmental Sustainability

The suboptimal engineering characteristics, including low tensile strength and significant compressibility volumetric changes, are the significant challenges faced during the construction of sub-structures in expansive Soil. The instability of the sub-structure leads to the settlement of the structure and compromises its safety and endurance. This paper explores how Bentonite nano clay (BNC) reacts with varying proportions of lime, Fly Ash, and silica fume. The ratios used for these additives were 2%, 4%, and 6%. The Compaction Characteristics and the stress-strain curve are analyzed. Incorporating silica fume into BNC leads to a decrease in both the liquid limit and the plasticity index. Concurrently, this addition increases the plastic limit of the clay. As the percentage of silica fume in the mixture rises, there is a corresponding decrease in the maximum dry unit weight and an increase in the optimum moisture content. Additionally, the introduction of silica fume contributes to an increase in the free swell but also it has an increase in the swelling pressure of clay. These results suggest that silica fume stabilization is an effective method for treating expansive clay.

Proportioning Study for Low-carbon Sulfate-resistant Concrete by Microbial Corrosion Testing

In addition to water absorption and chloride permeability measurement, sulfate resistance testing by microbial corrosion was conducted on low-W/B concretes made using large amounts of supplementary cementitious materials, including GGBF slag, for use as sewage pipes. The corrosion testing was conducted in a corrosion chamber at 30°C with a H2S concentration of 100 ppm, in which specimens were exposed to the environment under two conditions: one group in the gas and the other partially submerged in circulating sewage water. After exposure for one year, the corrosion rate in the partially submerged phase tended to be 1.3 to 2.9 times higher than in the gas phase. Also, the amount of corrosion was compared, with the corrosion products being examined by EPMA. Exposure to the gas phase and partially submerged phase was thus found to represent the stage of forming monosulfates and dihydrate gypsum and ettringite, respectively. Deterioration was found to proceed at a higher rate as the pH value on the concrete surfaces decreased. Within the range of this study, the addition of silica fume and small-size GGBF slag led to no appreciable effect.

Study on static and dynamic mechanical properties and microstructure of silica fume-polypropylene fiber modified rubber concrete

Through tests and micro-observations, the static and dynamic mechanical properties and microstructure of rubber concrete samples modified with varying amounts of silica fume and polypropylene fiber content were explored. The results indicate that incorporation of silica fume and polypropylene fiber can effectively enhance the performance of rubber concrete. Moreover, at 10% and 0.1% of silica fume and polypropylene fiber content respectively, rubber concrete’s compressive strength, splitting tensile strength, flexural strength, and dynamic compressive strength reached maxima. Furthermore, microstructure characteristic analysis indicated that inadequate adhesion between rubber particles and the matrix is responsible for compromised bearing capacity in unmodified rubber concrete. However, with the addition of silica fume and polypropylene fiber, the fiber binds the rubber particles closely with the matrix, while the silica fume fills the gaps between the matrix components. This combination results in rubber concrete with a denser internal structure and enhances its bearing capacity significantly.

Effect of silica fume on the performance of high-early-strength UHPC prepared with magnesium ammonium phosphate cement

Although ultra-high performance concrete (UHPC) prepared from Portland cement has high long-term strength and durability, its early strength development is still can be enhanced for shortening the prefabrication period or using it as a rapid repair material. Therefore, magnesium ammonium phosphate cement ultra-high performance concrete (MAPC-UHPC) was prepared using magnesium ammonium phosphate cement (MAPC), sand, steel fiber, and silica fume (SF) in this study. The effects of replacing MAPC with SF (5%–15%) on the fluidity, strength, and microstructure of MAPC-UHPC were studied. The results showed that the spread diameter of the MAPC-UHPC mixture was greater than 200 mm, and the setting time was between 5.5 and 8.5 min. Meanwhile, the 6-h compressive strength of MAPC-UHPC was higher than 100 MPa and could reach about 140 MPa in 28 d. When the 5%–15% binder was replaced by SF, the MAPC-UHPC fluidity and setting time increased with the increase in SF content. When 5% SF was used, the 6-h and 28-d compressive strengths of MAPC-UHPC increased by 3.91% and 3.86%, respectively, compared with the plain sample. The addition of SF promoted the formation of struvite and refined the pore structure, which also increased the compactness of the microstructure.

Steel rebar passivation in cementitious blend solutions – Silica fume vs. glass powder

Cement industries are pursuing sustainable alternatives in cementitious materials to minimize natural resources usage and reduce CO2 emissions. Utilizing Si-based materials such as silica fume (SF) and glass powder (GP) from waste is promising as partial replacements for cement. However, the passivating behavior of carbon rebars in these alternatives must be evaluated. This work evaluates the passivating ability of steel rebars in leaches from cementitious matrices containing SF and/or GP, comparing them against the behavior in Portland mixture (Control). Addition of SF and/or GP to the mixture did not compromise the spontaneous passivation of the rebars, with no sign of rust even after 30 days of immersion. Indeed, compared to the Control condition, the addition these supplementary materials showed beneficial response in terms of some electrochemical responses, such as the polarization resistance, Rp, corrosion current density, icorr, with lower values of current density upon the anodic potentiodynamic polarization after 37 h of immersion. Besides offering sustainability, incorporating SF and GP ensure cementitious matrices capable of spontaneously passivating low-cost and conventional rebars.