Papers by Keyword: Silica Fume

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Authors: Kumar S. Rajesh, Amiya K. Samanta, Dilip K. Singha Roy
Abstract: This investigation is focused on the physical and mechanical properties of Alccofine (AF) incorporating silica fume (SF) on M20 grade concrete. Normally, these industrial wastes (SF) are disposed off in landfill. The use of these industrial waste in concrete could reduce waste in the environment as well helps the environment against pollution as it is known that one ton of cement manufacture released one ton of carbon dioxide to the environment .Alccofine is a new replacement material on which very limited research has been done, its effect with flyash has been studied. The current study is a new experimental research undertaken to study the effect of alccofine on SF based concrete. Alccofine was varied in percentages of 0, 5, 10 and 15%, Silica fume was varied in percentages of 0, 5, 10, 15 % The aim of the investigation was to see the effect of alccofine on compressive strength of concrete and do a comparison on 7, and 28 days strength.The results showed that the cement replacement by 10% of alccofine gives higher values when compared with all other mix. The cement replacement by 10% alccofine gave a good improvement in compressive strength. Alccofine has the better performance when compare to the other slag material. It is helpful to make concrete workable
Authors: Desak Nyoman Deasi Triani, Januarti Jaya Ekaputri, Triwulan, Setyo Hardono, Tri Eddy Susanto
Abstract: This research use metakaolin and clay containing amorphous silica and alumina after calcination at 700°C. Mechanical properties and fire resistance of geopolymer paste increase as the ratio of silica to alumina. Mix design composition on this research based on the ratio of silica to alumina. The ratio of silica to alumina for metakaolin paste are 1.4 and 1.8. While for clay paste the ratio that used are 2.8 and 3.2. Na2SiO3 and NaOH with 10 M and 8 M were used as alkali activator at this research. Based on analysis the effect of increasing the ratio of silica to alumina increase fire resistance ability for both metakaolin and clay. However initial compressive strength is effected not only by ratio of silica to alumina but also the ratio of water to solid and SiO2/Na2O. The compressive strength decrease as the ratio of water to solid increases. Meanwhile compressive strength increase as the ratio of SiO2/Na2O increase.
Authors: Jul Endawati, Lilian Diasti, Enung
Abstract: In general, the use of massive flexible and rigid pavement for road construction causing green land reduction that have an impact on the reduction of the catchment area. Therefore, the use of porous concrete is an environmentally friendly alternative. Its usage is expected to absorb water into the ground. Permeable pavements have different design goals if compared to the conventional pavement, due to the ability to infiltrate the storm water through the pavement surface. The purpose of this research is to get the optimum proportion of porous concrete mixture using a friendly environment binder material. Fly ash (FA) and silica fume (SF) were used to replace a certain part of the Portland Cement Composite (PCC). The maximum FA replacement referred to the proportions of the FA percentage in the massive paving industry (25%) and the maximum SF replacement (6%) as recommended by ACI 225R-10. The highest 90-day compressive strength gained by specimens of 12% PCC replacement by FA (5.87 MPa), which is 10.2% higher compared to the porous concrete compressive strength which binder composed of 12% FA and 6% SF replacement. The permeability varies at 28 days, but at the age of 90 days, the porous concrete permeability almost evenly, so that the influence of the 6% silica fume in the mixture is not indicated. The ratio of 6% replacement of cement by silica fume with no fly ash gave the highest permeability of 1.4 cm/s, approaching the previous research conducted by Schaefer, et al (2006), while at the age of 90 days the permeability of porous concrete (1.11 cm/s) closed with the results done by Montes (2006).
Authors: D.S. Hazimmah, Khairunisa Muthusamy
Abstract: The results show the effect of polymer modification on the behavior of Ca (OH)2 in steel fiber reinforced concrete. The polymer modified concrete were prepared using acrylic emulsion polymer at various polymer-cement ratios; they were tested for mechanical strengths, moulded into specimens and cured. The cured specimens were subjected for compressive strength, flexural strength, splitting tensile strength and modulus of elasticity. The small specimens that moulded were subjected to X-ray diffraction (XRD). From the test results, it is concluded that formation of Ca (OH)2 in the polymer modified concrete reinforced with steel fiber is reduced possibly because of the absorption of Ca (OH)2 on polymer films formed in the concrete. The extent of reduction in the quantity of Ca (OH)2 depends upon the polymer-cement ratio, polymer type or both. Generally SFRPMC of mix 43 with 2.5% polymer-cement ratio were found to be more effective than other SFRPMC with 1.0% and 4.0% acrylic emulsion polymer in reducing the quantity of Ca (OH)2 in SFRPMC. The cement modifiers did not cause any detrimental effect on the degree of hydration as in SFRPMC therefore, does not provide a proper means for predicting their degree of hydration.
Authors: Adriana Eštoková, Martina Kovalcikova, Alena Luptáková
Abstract: The paper is aimed at comparative study of resistance of Portland cement composites with addition of silica fume as durability increasing factor in various aggressive environments (sulphuric acid with pH 4, the medium of activated bacteria and the cultivating medium without bacteria) during 150 days under model laboratory conditions. Experimental studies confirmed: the leaching of silicon ions calculated to 1 g of concrete sample affected with bacteria Acidithiobacillus thiooxidans was 2.5 times lower (31.78 mg/g of sample) for concrete sample with silica fume addition comparing to concrete sample of ordinary CEM I Portland cement without any additives (82.98 mg/g of sample). The highest concentration of calcium ions released (60.808 mg/g of sample) was observed for reference sample without silica fume addition placed in the cultivating medium. Silica fume based concrete samples were found to have better performance in terms of calcium ions leaching for all environments and silicon ions leaching.
Authors: Ting Ting Zhang, Yan Nan Du, Yan Jie Sun, Zi Ming He, Zhen Lin Wu
Abstract: Magnesium silicate hydrate (M-S-H) gel can be fabricated via the reaction of MgO with silica fume in the presence of sodium hexametaphosphate (Na-HMP). In this study, in effort to reduce the cost of the M-S-H gel system, pulverized fuel ash (PFA) was utilized as a silica source to replace silica fume. The influence of various PFA quantities on the compression strength and other properties of the M-S-H system were investigated via XRD, SEM, and TG-RTG analysis. Compressive strength was optimal when 35 wt% of silica fume was replaced. The hydration products were relatively more complex when PFA was used, containing hydrated calcium silicate, hydrated magnesium silicate, and carbonate gel, among other products. Magnesium carbonate participated in the hydration reaction process, which generated carbonated gel to form a grid structure and promoted the initial strength of the material. Taken together, the results showed that PFA can be feasibly and effectively used to form M-S-H gel cement systems at low cost.
Authors: Z. Bajja, W. Dridi, A. Darquennes, R. Bennacer
Abstract: Silica fume cement (SFC) based materials are largely used as a containment barrier for nuclear waste management. The safety of this storage mode depends on the knowledge of the effective diffusion coefficients of such materials. This work proposes a combination of computer models able to estimate the diffusion coefficients of SFC pastes and mortars, from a single investigation of the microstructure by nitrogen adsorption. The approach used consists firstly in manufacturing SFC mortars by varying sand volume fraction from 30 to 65% while silica fume replacement and water to binder ratio were respectively set at 10% and 0.4. Nitrogen adsorption tests were then performed and collected data on C-S-H nature are introduced into a SFC pastes hydration model. The latter provides the mineral composition which is an input parameter in the multilayer transport model that estimates the effective diffusion coefficient (De) of cement pastes. For mortars, a 3D biphasic model (sand and cement matrix) was used to compute the (De) of mortars at different inclusion volume fractions. The numerical results were approved by comparison to experimental data obtained from tritiated water (HTO) diffusion tests performed on manufactured mortars.
Authors: Michal Ženíšek, Tomáš Vlach, Lenka Laiblová
Abstract: Durability and high strength of concrete are closely associated with low porosity and generally denser material structure. This is achieved using the addition, which include also silica fume. This article deal with an effective dosage of silica fume in high performance concrete, in a proportion of 0-25 % by the weight of cement. Compressive strength, rheological behaviour and economic benefits were the main questions in this work. The expected increase in compressive strength showed itself in lower doses of silica fume, while higher doses did not produce a further increase in strength. In the case of rheological behaviour, we can confirm lower bleeding and segregation, but also faster drying of the surface layer. From the economic point of view, a small doses of silica fume are better, because then we have observed the highest increase in strength.
Authors: Smita Singh, M.U. Aswath, R.V. Ranganath
Abstract: The present investigation is on the effect of red mud on the mechanical properties and durability of the geopolymer paste in sulphuric and acetic acid solution. Red mud and fly ash were used to form the geopolymer paste along with the alkalies. The variation of red mud in the paste composition was from 0% to 90%. Cylindrical shaped specimens of 1 inch diameter and 1 inch height were prepared. The specimens were immersed in 5% sulphuric acid and 5% acetic acid for 1, 7, 14, 28, 56 and 84 days and tested for weight loss, visual deformation, strength loss and colour of the solvent, based on the procedure specified by ASTM C 267 – 01. SEM/EDX Tests were performed on the geopolymer specimens. Test results show that initially, the strength of the geopolymer increased upon the addition of red mud. The strength was maximum when the percentage of red mud was 30%. The maximum strength obtained was 38 MPa for the paste containing 30% red mud using 10M alkali solution as against 31.69 MPa, when only fly ash was used. Geopolymer paste containing 30% and 50% red mud showed better resistance to acid attack. The strength loss was minimum for the samples containing 30% red mud in both inorganic and organic acid i.e. sulphuric and acetic acid.
Authors: Osama Ahmed Mohamed, Waddah Al Hawat, Omar Fawwaz Najm
Abstract: Supplementary cementitious materials such as fly ash, silica fume and ground granulated blast furnace slag (GGBS) have been used widely to partially replace cement in producing self-consolidating concrete (SCC). The production of cement is associated with emission of significant amounts of CO2 and increases the human footprint on the environment. Fly ash, silica fume, and GGBS are recycled industrial by-products that also impart favorable fresh and hardened properties on concrete. This study aims to assess the effect of the amounts of fly ash and silica fume on strength and chloride penetration resistance of concrete. Rapid Chloride Penetration Test (RCPT) was used to assess the ability of SCC to resist ingress of chlorides into concrete. SCC mixes with different dosages of fly ash and silica fume were developed and tested at different curing ages. Test results showed that replacing 20% of cement with fly ash produced the highest compressive strength of 67.96 MPa among all fly ash-cement binary mixes. Results also showed that replacing15% of cement with silica fume produced the highest compressive strength of 95.3 MPa among fly ash-cement binary mixes. Using fly ash and silica fume consistently increased the concrete resistance to chloride penetration at the early ages. Silica fume at all dosages results in low or very low levels of chloride penetration at all curing ages of concrete.
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