Showing papers on "Silica fume published in 2004"
TL;DR: In this paper, the effects of binder systems containing different levels of silica fume on fresh and mechanical properties of concrete were investigated, and the results indicated that as the proportion of fume increased, the workability of concrete decreased but its short-term mechanical properties such as 28-day compressive strength and secant modulus improved.
Abstract: This paper presents the results of experimental work on short- and long-term mechanical properties of high-strength concrete containing different levels of silica fume. The aim of the study was to investigate the effects of binder systems containing different levels of silica fume on fresh and mechanical properties of concrete. The work focused on concrete mixes having a fixed water/binder ratio of 0.35 and a constant total binder content of 500 kg/m3. The percentages of silica fume that replaced cement in this research were: 0%, 6%, 10% and 15%. Apart from measuring the workability of fresh concrete, the mechanical properties evaluated were: development of compressive strength; secant modulus of elasticity; strain due to creep, shrinkage, swelling and moisture movement. The results of this research indicate that as the proportion of silica fume increased, the workability of concrete decreased but its short-term mechanical properties such as 28-day compressive strength and secant modulus improved. Also the percentages of silica fume replacement did not have a significant influence on total shrinkage; however, the autogenous shrinkage of concrete increased as the amount of silica fume increased. Moreover, the basic creep of concrete decreased at higher silica fume replacement levels. Drying creep (total creep − basic creep) of specimens was negligible in this investigation. The results of swelling tests after shrinkage and creep indicate that increasing the proportion of silica fume lowered the amount of expansion. Because the existing models for predicting creep and shrinkage were inaccurate for high-strength concrete containing silica fume, alternative prediction models are presented here.
531 citations
TL;DR: In this paper, the effect of silica fume on the bond characteristics of steel fiber in matrix of reactive powder concrete (RPC), including bond strength, pullout energy, etc., are presented.
418 citations
TL;DR: In this article, a test program was carried out to develop information about the mechanical properties of rubberized concretes with and without silica fume, which were obtained by partially replacing the aggregate with rubber contents varying from 2.5% to 50% by total aggregate volume.
370 citations
TL;DR: In this paper, the microstructure of recycled aggregate prepared from the crushing of old concrete was studied and an increase of ~30 and 15% in compressive strength at ages 7 and 28 days was observed after the silica fume treatment.
Abstract: The microstructure of recycled aggregate prepared from the crushing of old concrete was studied. It was found that the recycled aggregate is covered with loose particles that may prevent good bonding between the new cement matrix and the recycled aggregate. The old cement paste that remained on the natural aggregate was porous and cracked, leading to weak mechanical properties of the recycled aggregate. Treatment of the recycled aggregate by impregnation of silica fume solution and by ultrasonic cleaning was studied with the objective of overcoming the above-mentioned limitations. An increase of ~30 and ~15% in the compressive strength at ages 7 and 28 days was observed after the silica fume treatment. Ultrasonic treatment led to an improvement of ~7%.
366 citations
TL;DR: In this article, the effects of elevated temperatures on the compressive strength stress-strain relationship (stiffness) and energy absorption capacities (toughness) of concretes are presented.
347 citations
TL;DR: In this paper, the authors present a wide variety of possible solutions to the problem of early-age cracking due to autogenous shrinkage in concrete, including the addition of shrinkage-reducing admixtures more commonly used to control drying shrinkage, control of the cement particle size distribution, modification of the mineralogical composition of the concrete, addition of saturated lightweight fine aggregates, the use of controlled permeability formwork, and the new concept of water-entrained concrete.
Abstract: As the use of high-performance concrete has increased, problems with early-age cracking have become prominent. The reduction in water-to-cement ratio, the incorporation of silica fume, and the increase in binder content of high-performance concretes all contribute to this problem. In this paper, the fundamental parameters contributing to the autogenous shrinkage and resultant early-age cracking of concrete are presented. Basic characteristics of the cement paste that contribute to or control the autogenous shrinkage response include the surface tension of the pore solution, the geometry of the pore network, the visco-elastic response of the developing solid framework, and the kinetics of the cementitious reactions. While the complexity of this phenomenon may hinder a quantitative interpretation of a specific cement-based system, it also offers a wide variety of possible solutions to the problem of early-age cracking due to autogenous shrinkage. Mitigation strategies discussed in this paper include: the addition of shrinkage-reducing admixtures more commonly used to control drying shrinkage, control of the cement particle size distribution, modification of the mineralogical composition of the cement, the addition of saturated lightweight fine aggregates, the use of controlled permeability formwork, and the new concept of “water-entrained” concrete. As with any remedy, new problems may be created by the application of each of these strategies. But, with careful attention to detail in the field, it should be possible to minimize cracking due to autogenous shrinkage via some combination of the presented approaches.
285 citations
TL;DR: In this article, the effect of different supplementary cementitious materials (silica fume, fly ash, slag, and their combinations) on strength and durability of concrete cured for a short period of time was studied.
243 citations
TL;DR: In this paper, improved palm oil fuel ash (POFA) was used as a pozzolanic material in producing high-strength concrete and the POFA was ground by ball mill until the median particle size was reduced to about 10μm.
Abstract: This paper presents use of improved palm oil fuel ash (POFA) as a pozzolanic material in producing high-strength concrete. The POFA was ground by ball mill until the median particle size was reduced to about 10μm. It was used to replace portland cement, ASTM Type I, by 10, 20, and 30% by weight of cementitious materials to make high-strength concrete. It was found that high-strength concrete can be achieved by using ground POFA to replace portland cement Type I up to 30%. At the age of 28days, concretes containing 10, 20, and 30% of ground POFA gave compressive strengths of 81.3, 85.9, and 79.8MPa, respectively. Concrete with 20% replacement of ground POFA had the highest strength. It is slightly higher than that of concrete containing 5% condensed silica fume and about 92–94% that of 10% condensed silica fume concrete. The ground POFA content up to 30% had slightly effect on lowering the modulus of elasticity of concrete. In addition, the use of ground POFA reduced the peak temperature rise of concrete u...
232 citations
TL;DR: In this article, the behavior of a high-strength concrete (HSC) with silica fume (SF) modified with different amounts of solid particles recycled from crumbed used truck tires is presented.
221 citations
TL;DR: In this paper, a premix method similar to the sand-wrapping technique was utilized to make expanded polystyrene (EPS) concrete, which achieved a compressive strength of 10-25 MPa.
220 citations
TL;DR: In this article, the effects of silica fume on permeability, swelling pressure and compressive strength of the compacted clay liners as a hydraulic barrier were examined, and the test results showed that the sample with silica-fume exhibits quite low permeability and swelling pressure.
TL;DR: In this paper, the effects of fire and extinguishing on the properties of concrete, mortars with and without silica fume were exposed to different temperatures, such as 100, 200, 300, 600, 900 and 1200 °C, and cooled slowly in the air and fast in water in two groups.
TL;DR: In this article, an experimental program on compressive strength, porosity, electrical resistivity and polarization curves was carried out with the purpose of evaluating the effect of different silica fume (SF) additions (0, 6% and 12%).
Abstract: The addition of silica fume (SF) in concretes has been proposed as a form to improve their performance in resisting concrete reinforcement corrosion. In this study an experimental program on compressive strength, porosity, electrical resistivity and polarization curves was carried out with the purpose of evaluating the effect of different SF additions (0%, 6% and 12%). Concretes with different water–binder ratio (cement + SF) 0.50, 0.65 and 0.80 were used. The results have allowed to show that there are significant improvements of the concrete properties with the SF addition, suggesting its use in aggressive environments.
TL;DR: In this article, a method of improving coarse fly ash in order to replace condensed silica fume in making high-strength concrete was presented, which was used to replace Portland cement type I by weights of 0, 15, 25, 35, and 50%.
TL;DR: Shrinkage cracking performance of lightweight concrete (LWC) has been investigated experimentally on ring-type specimens as discussed by the authors, and it was found that the crack opening on ring specimens was wider than 2 mm for all concretes, while compressive and split-tensile strengths, static elastic modulus, and specific creep decreased with increasing coarse aggregate content.
28 Apr 2004
TL;DR: In this article, the authors used focused ion beams (fibs) for serial sectioning of nanoindentation sites in concrete-like composites, an intermediate step to nano-level analysis in concrete like composites.
Abstract: Nanotechnology and Construction in the 21 Century From nanotechnology to new production systems: the EU perspective Nanotechnology in civil engineering Nanotechnology: business and investment opportunities Integration of European nanotechnology research in construction Application of nanotechnology in construction - current status and future potential Nanotechnology for construction beyond the imagery Techniques and Instrumentation Focused Ion Beams (fib) - tools for serial sectioning of nanoindentation sites in cementitious materials Micro - an intermediate step to nano level analysis in concrete like composites Applications of DualBeam in the analysis of construction materials Synchrotron-Radiation X-ray Tomography: a method for the 3d verification of cement microstructure and its evolution during hydration Observation of the nanostructure of cement hydration by Soft X-ray Transmission Microscopy Study of pozzolan-cement interaction by Atomic Force Microscopy (afm) Estimation of the degree of hydration and phase constitutions by the SEM-BSE image analysis in relation to the development of strength in cement pastes and mortars Modification of cement paste with silica fume - a NMR study Modelling Modelling and temperature dependence of microstructure formation in cement based materials Numerical modelling of volume changes in cement-based systems at early ages Numerical modelling and experimental observations of the pore structure of cement-based materials Virtual concrete: working at the nanometer scale Evaluation of theoretical models for assessing interfacial properties in aged grc using fibre push-in test Moving-window representation of interfacial debonding in concrete Molecular modelling of confined fluids and solid-fluid interfaces in Portland cement and related materials Density functional calculation of elastic properties of portlandite and foshagite Exploring the micro-mechanics of open-ended pile driving via discrete element modelling Materials and Products Nanostructure of single carbon fibres investigated with synchrotron radiation High-performance nanostructured materials for construction Synthesis and characterization of nanoparticulate calcium aluminates Effects of water-cement ratio and curing age on the threshold pore width of hardened cement paste Effect of curing regime and type of activator on properties of alkali-activated fly ash Take a closer look: calcium sulphate based building materials in interaction with chemical additives Investigation of the micro-mechanical properties of underwater concrete Applications Thin films and coatings: atomic engineering The Nanohouse(TM) - an Australian initiative to develop the home of the future Building fapade integrated quantum dot concentrated solar electricity production Microsystems for the control of cable vibration Carbon nanotubes and their application in the construction industry Nano-science and -technology for asphalt pavements Natural roofing slate: the use of instrumented indentation technique to measure changes in the elastic modulus and hardness due to weathering Use of instrumented indentations for quality control of building materials Subject Index.
TL;DR: In this article, the strength properties and the rheological behavior of a cement-silica fume-superplasticizer system are presented, and it is suggested that an optimal superplasticization-to-fume ratio (1:10) provides ultra-dense packing and high fluidity of the system.
Abstract: This report generalizes the results of research into silica fume based high-performance concrete. The strength properties and the rheological behavior of a cement–silica fume–superplasticizer system are presented. From the test results it is suggested that an optimal superplasticizer-to-silica fume ratio (1:10) provides ultra-dense packing and high fluidity of the system. Models of high-performance concrete are developed from the experimental data. These models provide equations for calculating W/C for the required compressive strength (up to 130 MPa) and also the volume of cement paste for the required slump (within the range of 40–200 mm). For modeling purposes, concrete slump is presented as a function of the proportion of aggregates and both the volume and fluidity of cement paste. This modeling approach suggests a new method of proportioning of high-performance concrete mixtures.
TL;DR: In this article, the effect of silica fume on the compressive strength and split tensile strength and modulus of elasticity of low quality coarse aggregate concrete was evaluated.
Abstract: This paper reports results of a study conducted to evaluate the effect of silica fume on the compressive strength and split tensile strength and modulus of elasticity of low quality coarse aggregate concrete. Concrete specimens were prepared with four types of low quality aggregates, namely calcareous, dolomitic and quartzitic limestone and steel slag. Results indicate that the type of coarse aggregate influenced the compressive strength and split tensile strength and modulus of elasticity of both plain and silica fume cement concretes. Both the compressive and split tensile strengths of steel-slag aggregate concrete were more than those of limestone aggregate concretes. Incorporation of silica fume enhanced the compressive strength and split tensile strength of all concretes, especially that of the low quality limestone aggregates.
TL;DR: In this article, an analysis of various mature silica-fume-bearing concretes using backscatter mode scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis shows that such agglomerates have reacted in situ and given rise to recognizable types of reaction products filling the space within the original outline of the aggloomate.
TL;DR: In this article, the effect of calcium formate (CF) as an accelerator on the properties of pozzolanic cement pastes was investigated and the results showed that the addition of CF shortens the initial and final setting times and increases the compressive strength and combined water content at all ages of hydration.
TL;DR: In this article, the authors investigated the effect of the addition of excess silica to the CaO-SiO2-H2O system, either as microsilica or quartz flour, which, in theory, should not affect the equilibrium chemistry.
TL;DR: The microstructural and microchemical development of heat-cured Portland cement mortars containing silica fume, metakaolin, blast-furnace slag, and fly ash were analysed using pore solution analysis, X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy-dispersive Xray analysis (EDX) as mentioned in this paper.
TL;DR: In this article, a mathematical model is proposed to fit the power consumption curve of the mixer and to choose a criterion to determine the stabilisation time of the curve, which can be expressed by using the actual and maximum solid content concepts.
TL;DR: In this article, the use of fly ash as an admixture has been shown to enhance the EMI shielding effectiveness from 4 to 8 dB at 1 GHz, whereas use of silica fume has negligible effect on the shielding effectiveness.
TL;DR: In this article, the strengths and chloride penetration resistance of a series of high-performance concretes were measured after curing either at 23 °C or accelerated by heating to 65 °C.
TL;DR: In this paper, the use of metakaolin and silica fume as supplementary cementing materials in enhancing the near surface properties of concrete was investigated, and the results showed that the inclusion of these materials greatly reduced the initial surface absorption, water absorption and sorptivity of concrete in varying magnitudes.
Abstract: This paper presents the results of an investigation on the use of metakaolin and silica fume as supplementary cementing materials in enhancing the near surface properties of concrete. Metakaolin and silica fume mixtures, each with 10% replacement, were prepared and tested for initial surface absorption, water absorption and sorptivity. Metakaolin and silica fume were found to enhance the overall near surface characteristics of the concrete. The inclusion of metakaolin and silica fume greatly reduced the initial surface absorption, water absorption and sorptivity of concrete in varying magnitudes. Generally, the curing method adopted had significant effects on the near surface properties of concrete incorporating metakaolin or silica fume.
TL;DR: In this paper, two spent fluid catalytic cracking (FCC) catalysts, byproducts from oil-cracking refineries, were evaluated as pozzolanic admixtures of concrete.
Abstract: Spent fluid catalytic cracking (FCC) catalysts, by-products from oil-cracking refineries, were evaluated as pozzolanic admixtures of concrete. In this study, the activity of two spent FCC catalysts, i.e., Ecat and Epcat, were examined and compared. The pozzolanic activity was indicated by their activity index in presence of Portland cement and the consumption of calcium hydroxide determined by DSC measurements. The effect of these two catalysts on the compressive strength of mortars was also investigated. The results were compared to those of silica fume. It was found that both Ecat and Epcat, like silica fume, show good pozzolanic activity and are reactive with CH. Furthermore, Epcat possesses much smaller particle size than the other waste catalyst. Therefore, Epcat provides a filling effect on the microstructure and enhances the compressive strength of the resulting mortars. The performance of Epcat is close to or slightly better than that of silica fume. Compared to the control mortar (W/B=0.42) cured at between 3 and 28 days, mixes with 5–15% cement replacement by Epcat increased the compressive strength by 10–36%.
DOI•
01 May 2004
Abstract: Synopsis: The influence of some pozzolanic additions – such as silica fume, fly ash and ultra-fine amorphous colloidal silica (UFACS) – on the performance of superplasticized concrete was studied. Superplasticized mixtures in form of flowing (slump of 230 mm) or self-compacting concretes (slump flow of 735 mm) were manufactured all with a water-cement ratio as low as 0.44, in order to produce high-performance concretes (HPC). They were cured at room temperature (20°C) or steam-cured at 65°C in order to simulate the manufacturing of pre-cast members. Concretes with ternary combinations of silica fume (15-20 kg/m), fly ash (30-40 kg/m) and UFACS (5-8 kg/m) perform better – in terms of strength and durability – than those with fly ash alone (60 kg/m) and approximately as those with silica fume alone (60 kg/m). Due to the reduced availability of silica fume on the market, these ternary combinations can reduce by 60-70% the needed amount of silica fume for each pre-cast HPC element at a given performance level. Moreover, at later ages the strength reduction in steam-cured concretes with respect to the corresponding concretes cured at room temperature, is negligible or much lower in mixtures with the ternary combinations of pozzolanic additions.
TL;DR: In this article, differential thermal analysis and thermogravimetry were used to evaluate the effect of some additives, such as CaSO4, CaCl2 and silica fume amorphous silica from ferrosilicon synthesis on the mechanism and kinetics of reactions occurring in fly ash-Ca(OH)2 system.
Abstract: Differential thermal analysis and thermogravimetry were used to evaluate the effect of some additives, such as CaSO4, CaCl2 and silica fume amorphous silica from ferrosilicon synthesis on the mechanism and kinetics of reactions occurring in fly ash-Ca(OH)2 system. The accelerating role of these additives was demonstrated from the data relating to Ca(OH)2 consumption in hydrated pastes, determined by TG measurements.
TL;DR: In this paper, a testing regime was developed to optimize strength and durability characteristics of a wide range of high-performance concrete mixtures, including fly ash, slag cement and microsilica.
Abstract: A testing regime was developed to optimize strength and durability characteristics of a wide range of high-performance concrete mixtures The aim of the selected designs was to offer multiple solutions for creating a highly durable and effective structural material that would be implemented on Pennsylvania bridge decks, with a life expectancy of 75-100 years A prime method for optimizing the mixtures was to implement supplemental cementitious materials, at their most advantageous levels Fly ash, slag cement and microsilica all proved effective in creating more durable concrete design mixtures These materials have also shown success in substantially lowering chloride ingress, thus extending the initiation phase of corrosion An additional benefit studied in this program is the ability of these materials to extend the propagation phase of corrosion due to the high resistivity they impart to the concrete Ternary mixtures from these materials were particularly effective, showing much higher resistivity values than the materials used separately