Showing papers on "Silica fume published in 2016"
TL;DR: In this paper, the early-age strength development and mechanical properties of hardened UHPFRC were reviewed, and the effects of the curing conditions, coarse aggregate, mineral admixtures, fiber properties, specimen size, and strain-rate on the mechanical performance of UHP FRC were specifically investigated.
Abstract: A comprehensive investigation into the mechanical properties of ultra-high-performance fiber-reinforced concrete (UHPFRC), considering various influential factors, is imperative in order to obtain fundamental information for its practical utilization. Therefore, this paper reviewed the early-age strength (or setting) development and mechanical properties of hardened UHPFRC. In connection with the latter, the effects of the curing conditions, coarse aggregate, mineral admixtures, fiber properties, specimen size, and strain-rate on the mechanical performance of UHPFRC were specifically investigated. It was obvious that (1) heat treatment accelerates the hydration process, leading to higher strength; (2) a portion of the silica fume can be replaced by fly ash, slag, and rice husk ash in mechanical perspective; (3) the use of deformed (hooked and twisted) or long straight steel fibers improves the mechanical properties at a static rate; and (4) high rate loading provides a noticeable increase in the mechanical properties. Alternatively, there are some disagreements between the results from various ‘size effect’ tests and the effectiveness of using twisted steel fibers at static and high rate loadings. Further research to reduce the production cost of UHPFRC is also addressed in an attempt to make its widespread use more practical.
484 citations
TL;DR: In this article, the impact of supplementary cementitious materials (SCMs) on the pore solution composition of blended cements is reviewed, leading to a set of practical guidelines and recommendations.
Abstract: This paper is the work of working group 3 of the RILEM Technical Committee on Hydration and Microstructure of Concrete with SCM (TC 238-SCM). The pore solution is an essential but often overlooked part of hydrated cements. The composition of the cement pore solution reflects the ongoing hydration processes and determines which solid phases are stable and may precipitate, and which phases are unstable and may dissolve. The study of the cement pore solution therefore contributes to the understanding of the mechanisms as well as of the kinetics of cement hydration. This paper reviews the impact of supplementary cementitious materials (SCMs) on the pore solution composition of blended cements. In a first part, the extraction and analysis methods of cement pore solutions are reviewed, leading to a set of practical guidelines and recommendations. In a second part, an extensive literature survey is used to document the effect of the addition of SCMs (blast furnace slag, fly ash and silica fume) on the pore solution. Finally, in a third part the collected literature data are compared to thermodynamic simulations. The performance and current limitations of thermodynamic modelling of blended cement hydration are demonstrated and discussed in view of future progress.
300 citations
TL;DR: In this article, the effects of graphite nanoplatelets (GNPs) and carbon nanofibers (CNFs) on mechanical properties of ultra-high-performance concrete (UHPC) are investigated.
Abstract: Effects of graphite nanoplatelets (GNPs) and carbon nanofibers (CNFs) on mechanical properties of ultra-high-performance concrete (UHPC) are investigated. A non-proprietary UHPC mixture composed of 0.5% steel micro fibers, 5% silica fume, and 40% fly ash was used. The content of the nanomaterials ranged from 0 to 0.3% by weight of cementitious materials. The nanomaterials were dispersed using optimized surfactant content and ultra-sonification to ensure uniform dispersion in the UHPC mixture. As the content of nanomaterials is increased from 0 to 0.3%, the tensile strength and energy absorption capacity can be increased by 56% and 187%, respectively; the flexural strength and toughness can be increased by 59% and 276%, respectively. At 0.2% of GNPs, the UHPCs exhibited “strain-hardening” in tension and in flexure.
254 citations
TL;DR: In this article, a simple and effective double-side pullout testing method was adopted to characterize the interfacial bond properties, which include pullout load-slip relationship, bond strength, and pullout energy, of steel fiber-matrix in ultra-high strength cement-based material (UHSC) with 0-25% silica fume by the mass of binder.
Abstract: The use of silica fume can significantly enhance mechanical properties of concrete given its beneficial filling and pozzolanic effects. In this study, a simple and effective double-side pullout testing method was adopted to characterize the interfacial bond properties, which include pullout load-slip relationship, bond strength, and pullout energy, of steel fiber-matrix in ultra-high strength cement-based material (UHSC) with 0–25% silica fume by the mass of binder. The effects of silica fume content on flowability, heat of hydration, compressive and flexural strengths, hydration products, and pore structure of matrix at different curing time were evaluated as well. Backscatter scanning electron microscopy (BSEM) and micro-hardness measurement were used to examine the quality of interfacial transition zone (ITZ) around the fiber. In terms of the results, the optimal silica fume content could be in the range of 15%–25%. UHSC mixtures with these dosages of silica fume showed significant improvement in pullout behavior. Its bond strength and pullout energy at 28 d could increase by 170% and 250% compared to the reference samples without any silica fume. The microstructural observation verified the findings on the macro-properties development. Formation of more and higher strength of hydration products and refinement of ITZ around the fiber ensured higher micro-hardness, and thus improved the bond to fiber.
239 citations
TL;DR: In this paper, a systematic experimental investigation is carried out on concrete with rubber fibers (obtained by grinding waste rubber tyres) as partial replacement of fine aggregates, to evaluate the compressive strength, density, water permeability, static modulus of elasticity, dynamic modulus, and chloride diffusion.
236 citations
TL;DR: In this paper, the dispersion of graphene oxide (GO) in simulated pore solution and cement paste was investigated, and it was found that severe GO aggregation occurred in presence of divalent calcium ions.
215 citations
TL;DR: In this article, the authors investigated the possibility of using various types of waste powders, generated from marble and granite industry, as mineral additives in self-compacting concrete (SCC).
202 citations
TL;DR: In this paper, a one-part geopolymer was synthesized from alkali-thermal activated Bayer red mud (RM) with addition of silica to optimize its composition, but the longterm strength of the binder with only RM was poor because of the unstable polymerization due to the low SiO 2 /Al 2 O 3 molar ratio.
199 citations
TL;DR: In this paper, fly ash based geopolymer concretes with different percentages of silica fume were made by using NaOH/sodium silicate and cured in an oven at 100°C.
199 citations
TL;DR: In this article, three methods to improve and then assess the mechanical performance of CRC have been examined namely, rubber pre-treatment using sodium hydroxide (NaOH) solution, using silica fume additives, and increasing concrete cement content.
187 citations
TL;DR: In this article, the current state of knowledge on durability of concrete and mortar made up of pozzolans as a partial replacement of Portland Cement is reviewed based on published documents and several potential studies have been suggested for the future research.
TL;DR: In this paper, the influence of the pozzolanic reaction of soda-lime glass powder on solid phases, pore solution in cement paste, and the ASR mitigating effect are investigated.
Abstract: It is well recognized that finely ground soda-lime glass exhibits high pozzolanic reactivity. Fine glass grains will not undergo an Alkali-silica reaction (ASR) in the presence of alkali, and can even mitigate the ASR between alkali and reactive aggregates. Influences of the pozzolanic reaction of glass powder on solid phases, pore solution in cement paste, and the ASR mitigating effect are investigated in the study. The pozzolanic reaction of glass not only consumes portlandite to form in-situ C-S-H, which appears as reaction rim around glass grains, and precipitated C-S-H, but also reduces monosulfate level. The impacts of the pozzolanic reaction on species in pore solution are characterized by increased aluminum, sulfate, sodium, and silicon concentrations and decreased calcium concentration. The increase in aluminum and sulfate concentrations results from the decrease in solid monosulfate. Glass powder controls ASR by increasing aluminum concentration in pore solution to reduce the dissolution of amorphous silica from reactive aggregates.
TL;DR: In this article, the effects of replacing cement with silica fume in the reinforced self-compacting concrete with recycled steel fiber and study its mechanical properties and impact resistance were investigated.
TL;DR: In this paper, an experimental study was conducted aiming to replace silica fume (SF) by another fine supplementary cementitious materials (SCMs), such as fly ash (FA) or ground granulated blast furnace slag (GGBS), in order to reduce the amount of autogenous shrinkage.
TL;DR: In this article, the durability performance of self-compact concrete (SCC) made with Recycled Concrete Aggregates (RCA) as partial or full replacement of natural coarse aggregates (NCA) and with selected mineral admixtures as partial replacement of Portland Cement (PC) is reported.
TL;DR: In this paper, the in situ performance of concrete containing glass powder (GP) used as a partial replacement of cement at various construction sites (in Quebec-Canada between 2006 and 2012), including interior and exterior slabs and structural wall elements.
TL;DR: In this paper, the characteristics of recycled aggregates retrieved from crushed old concrete obtained from demolished structures, and five different presoaking surface treatment method and silica fume impregnating method to improve the properties of the recycled aggregate and its effect on recycled aggregate concrete (RAC).
TL;DR: In this paper, the authors evaluated the durability properties of UHPC concretes containing metakaolin instead of silica fume and found that the results of the permeability of oxygen diffusion, migration of the chloride ions and carbonation confirm good durability properties.
TL;DR: In this paper, the differences of effect of silica fume in paste, mortar and concrete were studied by determining the non-evaporable water content of pastes, measuring the compressive strengths of pasted, mortars and concretes containing 5% and 10% raw silica Fume, respectively, with water-to-binder ratios (W/B) of 0.29 and 0.24 and investigating the properties of interfacial transition zone between hardened paste and aggregate.
TL;DR: In this article, the effect of fly ash and silica fume on the water resistance of Magnesium-Potassium Phosphate Cement (MKPC) was investigated, and the improvement mechanism was discussed based on the micro-analysis of XRD, FSEM and pore structure.
TL;DR: In this article, the surface water absorption of self-compacting concrete (SCC) containing fly ash and silica fume using sorptivity test was analyzed and it was shown that the presence of fly ash in SCC significantly reduced the surface Water absorption at a waterbinder ratio of 0.38.
TL;DR: In this paper, the effects of superplasticizer (SP) and of mineral admixtures on selfcompactability and compressive strength of mortar and of self-compacting high performance concrete (SCHPC) were investigated.
TL;DR: In this paper, the effects of activating solution type, curing procedure, and source of fly ash in relation to the resulting compressive strength of fly-ash-based geopolymer concrete were investigated.
TL;DR: In this article, the combined effects of waste polyethylene terephthalate (PET) particles and pozzolanic materials on the rheological, mechanical and durability properties of self-compacting concrete (SCC) are evaluated.
TL;DR: In this paper, the authors investigated the potential use and effectiveness of expansive clay stabilization using a mixture of cement and silica fume (CSF) as a possibly useful option from environmental, economic, and (or) technical perspectives.
TL;DR: In this article, the synthesis of silica-fume-based foams, with a multi-range macroporosity, was obtained by alkaline activation, exploiting the gaseous production of hydrogen caused by the oxidation, in alkaline medium, of metal silicon impurities contained in silica fume.
TL;DR: In this paper, the mineralogical and elemental compositions in six alkali-activated cements (AACs) prepared by sodium silicate-activated ternary systems of fly ash, slag and silica fume at ambient conditions were investigated.
TL;DR: In this paper, the effect of using binary and ternary blends of nanosilica (NS) and microsilica on the mechanical properties of low binder ultra-high performance cementitious composites (UHPCs) was presented.
TL;DR: In this paper, the hydration and microstructures of concrete containing silica fume (SF) cured with different temperatures were studied by measuring the mechanical properties of concrete, determining the content of non-evaporable water and calcium hydroxide, and investigating the pore structure of matrix and the porosity of concrete.
TL;DR: In this article, the potential use of recycled tire rubbers in roller compacted concrete pavement with the purpose of both improving its performance and reducing its environmental impacts was discussed, and a regression model was defined to find a relationship between compressive and flexural strengths.