Showing papers on "Silica fume published in 2017"
TL;DR: In this paper, the effects of different amounts of polypropylene (PP) and macro-polymeric (MP) fibers on the mechanical properties and durability of high-strength concrete containing silica fume and nano-silica were investigated.
268 citations
TL;DR: In this article, a critical review on the rheological properties of fresh concrete in recent publications is revealed, and the applications of rheograph and workability box in mixture proportioning and quality control are also illustrated.
Abstract: The rheology is an effective tool to characterize workability, consistency, flowability, and predict stability, pumpability, shootability, pressure of formwork, multi-layer casting. This paper presents a critical review on the rheological properties of fresh concrete in recent publications. The applicable rheological models for the flow of concrete are revealed. The effects of constituents of fresh concrete, including cement, supplementary cementitious materials (fly ash, ground blast furnace slag, and silica fume), limestone powder, coarse and fine aggregates, and chemical admixtures (superplasticizer, viscosity modifying agent and air-entraining agent) on the rheological properties are discussed in detail. The applications of rheograph and workability box in mixture proportioning and quality control are also illustrated.
250 citations
TL;DR: In this paper, the Taguchi method has been used to design optimum mix proportions for geopolymer concrete with ground granulated blast furnace slag (GGBFS) as aluminosilicate source at ambient curing condition.
217 citations
TL;DR: In this article, the benefits resulted from various ratios of rice husk ash(RHA) on concrete indicators through 5 mixture plans with proportions of 5, 10, 15, 20 and 25% RHA by weight of cement in addition to 10% micro-silica (MS) to be compared with a reference mixture with 100% Portland cement.
209 citations
TL;DR: In this article, two surface treatment methods (NaOH, and Silane Coupling Agent) and three coating techniques (coated with normal cement, blended cement with silica fume, and blended cement plus sodium silicate) were used to improve rubber-cement bonding.
206 citations
TL;DR: In this article, the effect of silica fume on durability properties of fly ash based geopolymer concrete have been investigated by immersing the cubes in 2% sulphuric acid and 5% sodium chloride solutions.
185 citations
TL;DR: In this paper, the effect of substitution of slag with silica fume on compressive strength and permeability of alkali activated slag concrete has been examined and analyzed in this study.
161 citations
TL;DR: In this article, the effects of silica fume on properties of fly ash-based geopolymer under thermal cycles were revealed, and it was shown that the incorporation of fume improves the microstructure and improves the thermal resistance.
Abstract: This work aims to reveal the effects of silica fume on properties of fly ash based geopolymer under thermal cycles. Geopolymer specimens were prepared by alkali activation of fly ash, which was partially replaced by silica fume at levels ranging from 0% to 30% with an interval of 10%, by mass. Microstructure, residual strength and mass loss of fly ash based geopolymer blended with silica fume before and after exposed to 7, 28 and 56 heat-cooling thermal cycles at different target temperatures of 200 °C, 400 °C and 800 °C were assessed and compared. The experimental results reveal that silica fume addition enhances strength development in geopolymer. Under thermal cycles, the compressive strength of geopolymer decreases, and the compressive strength loss, as well as the mass loss, increases with increasing target temperature. The strength loss is the same regardless of silica fume content after thermal cycles. Microstructure analysis uncovers that pore structure of geopolymer degrades after thermal cycles. The pores of geopolymer are refined by the addition of silica fume. The incorporation of silica fume optimizes the microstructure and improves the thermal resistance of geopolymer. Silica fume increases the strength of the geopolymer and even though the strength loss is the same, the strength after heat cycle exposure is still good.
160 citations
TL;DR: In this article, the effects of rice husk ash (RHA) on strength and permeability of ultra-high performance concrete (UHPC) were investigated, and the results showed that the addition of RHA to replace SF decreases the fluidity of fresh UHPC mixture and entraps more air bubbles.
153 citations
TL;DR: In this paper, a fly ash microsphere collected directly from a high-temperature furnace using ceramic dust tubes to high-strength concrete, and with silica fume as a control admixture, investigated the effects of FAM on the hydration and hardening processes of the cementitious materials and the macroscopic properties of the high strength concrete.
Abstract: This study applied a type of fly ash microsphere (FAM) collected directly from a high-temperature furnace using ceramic dust tubes to high-strength concrete, and with silica fume as a control admixture, investigated the effects of FAM on the hydration and hardening processes of the cementitious materials and the macroscopic properties of the high-strength concrete. Two cement replacement levels (8% and 15%) and two water-to-binder (W/B) ratios (0.35 and 0.25) were utilized. The results show that FAM has a relatively high level of early activity; SEM images indicate that a significant portion of the FAM reacted at early ages in the cement-FAM hardened paste. Though the early activity of FAM is lower than that of silica fume, the cement-FAM complex binder has similar hydration properties with the cement-silica fume complex binder. At 90 d, FAM consumed less Ca(OH) 2 than silica fume and a significant amount of unreacted FAM remained in the hardened pastes. The contributions of FAM to the pore structure of the hardened pastes are lower than those of silica fume at early ages; however, FAM can significantly improve pore structure at late ages, similar to silica fume. In addition, FAM can improve the flowability, late-age strength, and permeability to chloride ions of concrete, while decreasing early-age autogenous shrinkage.
151 citations
TL;DR: In this article, the authors investigated the sustainable utilisation of copper slag (CS) as fine aggregates in Self Compacting Concrete (SCC) using fly ash (FA) and silica fume (SF) as Supplementary Cementitious Materials (SCMs).
TL;DR: In this paper, a simple and practical method of reducing the water/binder ratio while adding super-plasticizers to maintain workability was proposed to increase the compressive strength of UHVFA concrete.
TL;DR: In this article, a study was conducted to determine the possibility of producing and using fine glass powder (FGP) as a silica fume (SF) partial replacement in UHPC, and the results showed that FGP with a mean particle size (d50) of 3.8 µm could be recommended as an optimal PSD to fill the gap between cement and SF particles.
TL;DR: In this article, the authors evaluate the influence of commercial densified silica fume (SF) and of recycled concrete aggregates (RA) on the behavior of high performance concrete (HPC).
TL;DR: In this article, the authors investigated the effect of pumice powder on the workability retention of concrete and the slumps were measured with elapsed time, and the results revealed that incorporation of SF substantially enhanced the properties of the mixtures.
TL;DR: In this article, the impact of two grades of calcined clay on the hydration and microstructural development of UHPFRC matrices was investigated, where 54% of the cement by volume has already been replaced by a limestone with similar PSD.
TL;DR: In this paper, the behavior of two-stage concrete mixtures incorporating different supplementary cementitious materials (SCMs) as partial replacement for ordinary Portland cement (OPC) was investigated, and two different sodium sulfate exposure regimes were studied.
TL;DR: In this article, the physical properties of eco-friendly Ultra High Performance Concrete (UHPC) incorporating industrial by-products including coal bottom ash, fly ash and two types of slag powder are characterized.
17 May 2017
TL;DR: In this article, the authors proposed a high-performance concrete which is prepared from the following raw materials: 290-305kg/m of cement, 220-270kg/mt of mineral powder, 20-30kg/t of silica fume, 104-114 kg of water, 679-720 kg of sand, 1070-1135 kg of stones and 8-9 kg of an ether regulator modified polycarboxylate superplasticizer.
Abstract: The invention relates to high-performance concrete which is prepared from the following raw materials: 290-305kg/m of cement, 220-270kg/m of mineral powder, 20-30kg/m of silica fume, 104-114kg/m of water, 679-720kg/m of sand, 1070-1135kg/m of stones and 8-9 kg/m of an ether regulator modified polycarboxylate superplasticizer. Compared with the conventional high-strength concrete, the high-performance concrete disclosed by the invention has the advantages that the cement content is reduced from 500kg/m to 209-305kg/m , and the cementing agent content is reduced from 600-750kg/m to 540-570kg/m . The slump of the high-performance concrete is 230-250mm, pump concrete without slump loss is obtained at the temperature of 32 DEG C within 3 hours, and the dumping time is less than 20 seconds.
TL;DR: In this article, the compressive strength of metakaolin-based geopolymer cements was compared to the one of alkali-based cements using a dilution of commercial phosphoric acid in distilled water.
TL;DR: In this paper, the effect of sand gradation, binder type and content, and curing regimes on concrete's compressive strength was examined, and a 90-day strength of 155 MPa was achieved with a silica fume content of 5% and without heat curing.
TL;DR: In this paper, the effects of silica fume, PVA fiber and their combinations on the mechanical properties, microstructure, abrasion resistance and volume stability of cement pastes and/or fly ash concrete were studied experimentally.
Abstract: The effects of silica fume, PVA fiber and their combinations on the mechanical properties, microstructure, abrasion resistance and volume stability of cement pastes and/or fly ash concrete were studied experimentally in this work. The results indicated that the compressive strength and tensile strength of concrete containing both silica fume and PVA fiber were obviously improved compared with the control concrete. The addition of PVA fiber in concrete considerably reduced the drying shrinkage and improved the anti-cracking resistance of cement pastes and concrete, and the abrasion resistance of concrete significantly increased with the addition of silica fume and PVA fiber. These findings have been successfully adopted to guide the design and construction of hydraulic structures in the southwest of China.
TL;DR: In this article, the combined effects of nano-silica (NS) and micro-cement (MS) on the strength and microstructure of mortar or the mortar portion of HPC were investigated.
TL;DR: In this paper, a new dispersant hydroxyethyl cellulose was used with the aids of pre-dispersion by ultrasonic wave to realize the uniform distribution of chopped carbon fibers in the cement matrix.
TL;DR: In this article, an analysis of the mechanical behavior of high-performance concrete incorporating fine and coarse recycled aggregates (FRA and CRA) was made, and the results obtained in the compressive strength, splitting tensile strength, modulus of elasticity, ultrasonic pulse velocity and bond strength tests showed that it is possible to produce highperformance concrete without NA.
TL;DR: In this paper, the effect of different binder to solution ratio (B/S) and different Si/Al molar ratio in the synthesis of binary binder based geopolymer paste on their workability, setting and compressive strength is investigated.
TL;DR: In this paper, the effect of partial replacement of slag with nanosilica and microsilica on its permeability was examined through water impermeability test, rapid chloride test, carbonation test, short-term and total water absorption tests, and compressive strength test.
TL;DR: In this article, the microstructural and chemical changes of calcium aluminate cement (CAC)-based UHPC exposed to high temperatures were investigated, which led to a significant increase in micro-pores.
TL;DR: In this article, the authors quantified and compared the interfacial transition zone (ITZ) for mortar with RAP aggregates relative to dolomite aggregates through image analysis of backscattered electron micrographs.
TL;DR: In this article, the effect of four different curing regimes namely; tap water curing (WC), wet sack curing (WSC), air curing (AC), and liquid paraffin wax curing (LPWC) and different curing times (3, 7, 28, 56 and 180) on the mechanical properties of self-compacting Mortars (SCMs) were investigated.