Showing papers on "Silica fume published in 2015"
TL;DR: In this article, the theoretical principles, raw materials, mixture design methods, and preparation techniques for UHPC are reviewed, including reduction in porosity, improvement in microstructure, enhancement in homogeneity, and increase in toughness.
699 citations
TL;DR: In this article, the effect of the addition of steel and polypropylene fibers on the mechanical and some durability properties of high-strength concrete (HSC) was investigated, and the results showed that the incorporation of 1% steel fiber significantly enhanced the splitting tensile strength and flexural strength of concrete.
521 citations
TL;DR: In this article, the effectiveness of supplementary cementitious materials (SCMs) such as ground granulated blast-furnace slag (GGBS), fly ash (FA), and silica fume (SF) in reducing CO2 emissions from ordinary Portland cement (OPC) concrete was examined by assembling and analyzing a comprehensive database including 5294 laboratory concrete mixes and 3915 plant mixes.
376 citations
TL;DR: In this article, the effects of some admixtures including silica nanoparticles, silica fume and Class F fly ash on different properties of high performance self compacting concrete (HPSCC) were presented.
323 citations
TL;DR: In this paper, the effects of graphene oxide (GO), silica fume (SF) and graphene oxide encapsulated Silica Fume (GOSF) on the rheological properties of cement pastes were investigated.
208 citations
TL;DR: In this article, a microstructure analysis revealed that modification of the interfacial transition zone (ITZ) was responsible for this strength enhancement, and the results demonstrated that adding 3% or 5% nS to specimens free of silica fume would increase both cement paste and concrete compression strength.
198 citations
TL;DR: In this paper, the microstructure development of cement-silica fume blends is very different from plain cement, and the Ca/Si ratio in the inner product (IP) C-S-H decreases as CH is consumed to reach Ca ≈ 1.40-1.50 at the point when CH has disappeared, and then drops down to 1.00 in absence of CH.
175 citations
TL;DR: In this article, the feasibility of using marble slurry in concrete production, as partial replacement of Portland cement was examined, and the optimal replacement level of Portland cements by marble slayers was found at 10%.
167 citations
TL;DR: In this article, the effect of nano-silica, Cu 0.5 Zn 0.4 and Ni ferrite on the compressive strength, splitting tensile strength, flexural strength and modulus of elasticity of concrete was evaluated.
162 citations
TL;DR: In this paper, the effect of replacement of fine aggregates by waste rubber fibers on the impact resistance of concrete has been assessed, and the impact tests on concrete have been conducted by three different techniques; drop weight test, flexural loading test and rebound test.
157 citations
TL;DR: In this article, the characteristics of the pozzolanic reactivity of nanoSiO2 from studies of its reaction kinetics, morphology and structure of the hydrates and the influences of these features on the properties of cement-based materials were explored.
Abstract: The aim of this work is to understand the characteristics of the pozzolanic reactivity of nanoSiO2 from studies of its pozzolanic reaction kinetics, morphology and structure of the hydrates and the influences of these features on the properties of cement-based materials, so as to explore a more targeted way of using nanoSiO2 in cement or concrete. It revealed that the pozzolanic reaction of nanoSiO2 is of the first-order and the apparent reaction rate constant of nanoSiO2-4 nm is about one order of magnitude bigger than that of silica fume, but the specific reaction rate constant is about one half to that of silica fume. A compacter gel structure and poorer crystallinity of the hydrates of nanoSiO2 to those of silica fume are found, as well. The rate of hydration of cement at very early ages is enhanced by nanoSiO2, but the rate slows down with aging due to the compact gel structure. To make the use of the high pozzolanic reactivity and ultrafine particle size of nanoSiO2, as well as its resulting compact gel structure, colloidal nanoSiO2 was applied onto the hardened cement mortar by brushing technique and a less permeable surface was resulted, which shows the potential of using nanoSiO2 as a surface treatment material for cement-based materials.
TL;DR: In this article, the authors provided strength and durability test results for rubberized concrete that contains silica fume (microsilica) for road side barriers with the intent to reduce injuries and fatalities during crashes.
TL;DR: In this article, the authors used H-1 NMR signal intensities and relaxation analysis to characterise white Portland cement paste incorporating 10 wt.% of silica fume.
TL;DR: In this article, the authors developed a prediction model of the chloride diffusion coefficient for silica fume concrete under long-term exposure to a durability site located in the southern region of Iran.
Abstract: Chloride-induced corrosion is the main factor in determining the durability and service life of the reinforced concrete structures exposed to marine environments. Recognition of chloride diffusion phenomenon in concrete and developing a prediction model that can estimate the service life of the concrete structures subject to long-term exposure is vital for aggressive marine environments. The present study focuses on developing such a prediction model of chloride diffusion coefficient for silica fume concrete under long-term exposure to a durability site located in the southern region of Iran. All investigations are based on 16 concrete mix designs containing silica fume with variable water-to-binder ratios exposed to sea water for maximum period of 60 months. This empirical model is developed by applying regression analysis based on Fick’s second law on the experimental results and is compared with previous studies in this area. This comparison indicates that the predicted chloride diffusion coefficient level is within a ±25% error margin in the specimens. The results indicate that reducing the water-to-binder ratio and adding the silica fume to a dosage of 10% reduces the chloride diffusion coefficient in concrete. This study also confirms that the chloride diffusion coefficient increases with temperature and decreases over time.
TL;DR: In this paper, a broad study of Portland cement mortar mixtures containing silica fume, plain or silica-functionalized carbon nanotubes, and carbon fibers was performed to characterize changes in fracture properties.
Abstract: Fiber reinforcements provide many benefits to cementitious composites, including reduction of crack widths and increases in ductility. However, the interfacial transition zone between fibers and hydrated cement can contain a high proportion of calcium hydroxide and porosity. With their high moduli of elasticity, carbon nanotubes and carbon fibers could provide substantial mechanical reinforcement at multiple length scales, but only if their bond to the matrix can be controlled. Surface treatments of fibers and addition of supplemental materials in the matrix can influence both the mechanical interaction at the interface and the dispersion of these relatively small reinforcements. We performed a broad study of Portland cement mortar mixtures containing silica fume, plain or silica-functionalized carbon nanotubes, and carbon fibers to characterize changes in fracture properties. The early age hydration kinetics of cement pastes containing carbon nanotubes were compared using isothermal calorimetry. Early age fracture surfaces of cement pastes containing carbon fibers were observed using a scanning electron microscope. The notched beam test method of the Two Parameter Fracture Model was used to determine the fracture properties of each mix. We observed that silica fume and silica functional groups improved the fracture performance of mixtures containing carbon nanotubes and carbon fibers. Further optimization of dosage, size, and interface strength is required to fully utilize carbon nanotubes in cementitious composites.
TL;DR: In this article, the authors investigated the flowability, compressive strength, heat of hydration, porosity and calcium hydroxide content of ultra-high-strength concrete (UHSC) with cement-silica fume-slag binder at 20°C.
Abstract: This study investigated the flowability, compressive strength, heat of hydration, porosity and calcium hydroxide content of ultra-high-strength concrete (UHSC) with cement–silica fume–slag binder at 20 °C The composition of the binder was designed using seven-batch factorial design method The relationships between the binder composition and the properties were expressed in contours Results showed that proper silica fume content could improve the flowability and compressive strength of UHSC, reduce the porosity and calcium hydroxide content of UHSC Slag reduced the flowability, compressive strength, porosity, and calcium hydroxide content of UHSC to certain extent The silica fume and slag demonstrated positive synergistic effects on the flowability and 3 d compressive strength, but have negative synergistic effects on the total heat of hydration, hydration heat when the time is infinitely long(P0), 56 d compressive strength, porosity and calcium hydroxide content of UHSC
TL;DR: In this paper, the carbonation resistance of mortar and concrete is measured by the ratio between water added during production and the amount of reactive CaO present in the binder (w/CaO active).
Abstract: When cement with mineral additions is employed, the carbonation resistance of mortar and concrete may be decreased. In this study, mortars containing mineral additions are exposed both to accelerated carbonation (1% and 4% CO2) and to natural carbonation. Additionally, concrete mixtures produced with different cements, water-to-cement ratios and paste volumes are exposed to natural carbonation. The comparison of the carbonation coefficients determined in the different exposure conditions indicates that mortar and concrete containing slag and microsilica underperform in the accelerated carbonation test compared to field conditions. The carbonation resistance in mortar and concrete is mainly governed by the CO2 buffer capacity per volume of cement paste. It can be expressed by the ratio between water added during production and the amount of reactive CaO present in the binder (w/CaOreactive) resulting in a novel parameter to assess carbonation resistance of mortar and concrete containing mineral additions.
TL;DR: In this article, the properties of cement-based mortars with vermiculite and silica fume were investigated at ambient and elevated temperatures, and the results indicated that expanded vermiculate aggregate is a good fire resistant material.
TL;DR: In this article, the effect of viscosity modifying agent (VMA) and silica fume on the rheological and mechanical properties of self compacting concrete is investigated.
TL;DR: In this paper, the effects of incorporating silica fume (SF) in the concrete mix design to improve the quality of recycled aggregates in concrete are presented, and concrete properties are evaluated by means of compressive strength, tensile splitting strength, water absorption and ultrasonic pulse velocity.
TL;DR: In this article, the surface area and particle size distribution of supplementary cementitious materials (SCMs) are measured using various methods, such as air permeability, sieving, laser diffraction, optical flow analysis, image analysis, and MIP.
Abstract: The particle size distribution, surface area and shape are fundamental characteristics of supplementary cementitious materials (SCMs). Accurate measurement of these properties is required in computational efforts to model the hydration process, and the characterization of these parameters is also an important practical issue during the production and use of blended cements. Since there are no standard procedures specifically for the determination of physical properties of SCMs, the techniques that are currently used for characterizing Portland cement are applied to SCMs. Based on the fact that most of the techniques have been developed to measure cements, limitations occur when these methods are used for other materials than cement, particularly when these have lower fineness and different particle shape and mineralogical composition. Here, samples of fly ash, granulated blast furnace slag and silica fume were tested. Different results obtained using several methods for the determination of specific surface area are presented. Recommendations for testing SCMs using air permeability, sieving, laser diffraction, BET, image analysis and MIP are provided, which represent an output from the work of the RILEM Technical Committee on Hydration and Microstructure of Concrete with Supplementary Cementitious Materials (TC-238-SCM).
TL;DR: In this paper, experimental investigation is performed for producing new cement-based with relatively high strength, low density and good thermal properties for energy efficient buildings, where different types of concretes containing silica fume (SF), superplasticizer (SP) and air-entrained admixtures are prepared with a constant water-cement ratio, and normal aggregates replaced by lightweight aggregates (LWAs) including pumice (PA), expanded perlite (EPA) and rubber aggregates(RA) at different volume fractions of 10, 20, 30,
TL;DR: In this paper, the effect of different additives on the strength foamed concrete by characterising air-void size and shape parameters and identifying the influence of these parameters and changes to cement paste microstructure on strength was investigated.
TL;DR: In this article, nanoindentation was used to investigate the microstructures of cementitious composites containing silica fume and fly ash, and the mechanical properties (elastic modulus and hardness) of individual phases (like outer product, inner product, calcium hydroxide, fly ash particles, residual cement grains) were investigated and analyzed.
Abstract: In this study, nanoindentation was used to investigate the microstructures of cementitious composites containing silica fume and fly ash. With the help of scanning electron microscope, the mechanical properties (elastic modulus and hardness) of individual phases (like outer product, inner product, calcium hydroxide, remained fly ash particles, residual cement grains) in cementitious composites containing silica fume and fly ash were investigated and analyzed. Additionally, this study examined the differences between the ‘C–S–H’ phases in the different cementitious composites and provided an insight into the influence of mineral admixtures (silica fume and fly ash) on the properties of the ‘C–S–H’ phase.
TL;DR: In this paper, the compressive strength of hardened concrete was determined after 7, 28 and 90 days, and the results revealed that the concrete mixes containing magnetite coarse aggregate with 10% silica fume (SF), 20% fly ash (FA), and 30% ground granulated blast furnace slag (GGBFS) reached the highest compressive-strength values exceeding over the M60 requirement by 14% after 28 days.
TL;DR: In this paper, a critical review on UHPC mixture design methods with a discussion on the use of nano-materials in the latter aiming at reaching an eco-efficient UHCPC is presented.
TL;DR: In this article, the authors present results of a study on chemical acceleration of a neutral granulated blast-furnace slag activated using sodium carbonate. And they show that with accelerators, compressive strength up to 15MPa can be achieved within 24h in comparison to 2.5MPa after 48h for a mix without an accelerator.
TL;DR: In this paper, the performance of a two-stage approach of using limestone powder (LP) pre-coated crumb rubber and silica fume (SF) to enhance the rubberized cement mortar was investigated.
TL;DR: In this paper, the rheological properties of 57 SCC mixtures with various SCM were investigated for a constant slump flow value, and good correlations were established between plastic viscosity and V-funnel flow time values for all w/b ratios.
TL;DR: In this article, the properties of self-compacting concretes (SCCs) produced with recycled coarse aggregates and/or recycled fine aggregates compared to SCCs with natural aggregates (NAs) were addressed.