Papers by Keyword: Silica Fume

Abstract: The effect of modified silica fume (mSF) and cellulose fiber (CF) content on the cure characteristics, mooney viscosity, mechanical, durability and heat resistance properties are investigated; as compared with SF and unfilled natural rubber. From the results reveal that mSF and CF affect not only fast cure rate, high viscosity but also improve rubber mechanical and heat resistance properties. Additionally, the mSF and CF are added into the natural rubber to produce antivibration rubber product and then study the rubber product performance such as durability properties. The mSF and CF effective in improving the crack resistance of antivibration rubber product more than SF and unfilled natural rubber which is due to enhancing the stiffness. The all obtained results, it can be proved that mSF and CF as the new alternative fillers in rubber industry.

Abstract: In the present work, the properties of Polyethylene Waste cement mortar containing Polyethylene Waste treated by a reactive material are tested and compared with normal Polyethylene Waste and normal cement mortar. The Polyethylene, which is cured by a different reactive material such as: (cement, a fly ash and silica fume) is used as fine as aggregate a volumetric fractional replacing of the sand in a cement mortar. The percent of replacement was 10% by volume, density, compressive strength, modulus of rupture, and absorption are tested for all mixes at variable ages. The current results display that the cure of Polyethylene by cement were significantly improves the characteristics of Polyethylene cement mortar. Moreover, the results show that all treatment improved properties of cement mortar as a compared with Polyethylene without treatment.

Abstract: This study evaluates the influence of utilizing silica fume as a stabilizer to the filler on the behavior of asphalt mixes. The investigation of the properties of asphalt mixes was conducted by using different percentages of Silica Fume (0, 3, 6, and 9% by filler weight). Results indicate that, the OAC is 4.7% and it achieves the best results in the Marshall tests. Marshall Stability is increased by about 27.5% and the flow is decreased by about 20.2 %. In this study the implementation of 9% of silica fume in the asphalt concrete mix showed a considerable excess in the resistance to moisture damage of 28% when compared to the original mix. A great decrease in the tensile strength of asphalt concrete mixes, in a range from (4-15)% could be noticed following the moisture damage process for both the reference and silica fume adjusted mixes. Six percent of it was the optimum percent that had developed the tensile characteristics of the hot asphalt concrete mixes. The moisture sensibility of the asphalt concrete was reduced with an increase in the silica fume content. Following the moisture damage process, Silica fume of 9% was the optimum percent that had developed the punching shear characteristics of asphalt concrete. It exhibited a positive effect of 20%, while 6-9% of silica fume exhibited a positive effect of 5-9% on the development of the tensile characteristics of asphalt concrete.

Abstract: In this research 26 mixes in six different group were studied with three groups for each of the water cementitious material ratios (w/b) of 0.3 and 0.4 and a control mix. The first and fourth groups contained five percentages of silica fume (SF) as partial replacement of cement (5%, 7.5%, 10%, 12.5, 15%) for w/b ratios of 0.3 and 0.4, respectively. The second and fifth groups contained four percentages of Class F fly (FA) ash as partial replacement of cement (10%, 15%, 20% and 25%) for the w/b ratios of 0.3 and 0.4, respectively. The third and sixth groups contained three different percentages of both Class F fly ash and silica fume as partial replacement of cement with SF 5%+ FA 10%, SF 10%+ FA 15% and SF 15%+ FA 20% for w/b ratios of 0.3 and 0.4, respectively. For all of these mixes the compressive strength was first studied then the benefit greenhouse gases (GHG) ratio and Benefit cost ratio were found for all the studied mixes. Two optimization processes were performed during the course of this research, the first optimization process results can be used when the concrete durability is not a concern (concrete durability results are not accounted for). Whereas, the results of the second optimization process can be used when the concrete durability is a concern (concrete durability results are accounted for). The details of the results and the optimization processes are presented in this paper.

Abstract: The paper considers how cullet of different particle-size distribution affects the concrete strength. Experiments have proven that large-particle cullet (1.25 cm or larger) could be used as an aggregate; the concrete strength will be on par with those of ordinary natural/crushed sand concrete. The paper proves the feasibility of injecting highly dispersed silica fume in combination with effective polycarboxylate-based superplasticizers in cullet-based concrete mixtures. Highly dispersed silica fume will positively affect the strength characteristics of concrete, as silica fume in cement rock reacts with Са (ОН)₂, which is released upon the hydration of the clinker minerals С₃S and С₂S; the reaction produces very strong compounds. Concretes containing up to 30% silica fume in combination with a superplasticizer will feature very high early strength. Use of strong aggregates with a 30% cullet content can produce strong concretes; after steamed, a concrete containing silica fume and polycarboxylate-based superplasticizer will reach 90% of the graded strength. Cement-rock microstructure studies show that the polymer component of the STACHEMENT 2280 superplasticizer will gradually transcend from the glass grains to the cement rock. The interface between the polymer-coated glass grains and the cement rock is blurred and barely present. This strengthens the glass-rock adhesion and improves the concrete strength. This is why cullet is recommended for use in the production of curb stones.

Abstract: The effectiveness of silica fume for the fine-grained concrete used for 3-D technologies is proved in the give scientific paper. The advantages of silica fume using for concretes are presented. The mathematical modeling is used for the fine-grained concrete high-quality compositions’ development. The effectiveness of silica fume has been proved by the studies. The increase in the strength characteristics of concrete with the addition of silica fume is explained by the active pozzolan reaction, which starts when the concrete mix is ​​mixed with water.

Abstract: The use of different supplementary cementitious materials (SCMs) has attracted the interest of researchers for years. These materials have their advantages and dis-advantages. The optimal use of these SCMs in concrete may call for blending them together in concrete instead of using them individually. The blend may increase their quality as one disadvantages may be catered for by another one advantages. The present study focusses on investigating the effect of proportional combination of these SCMs on strength development. Three different South African SCMs (Ground granulated blast-furnace slag, Silica fume and Fly ash) were blended at different proportions and used as replacement of cement in concrete. Compressive strength test based on SANS 5860:2006 standard were adopted. The compressive test was performed on 16 different mixes at 7, 14, 28, 90 and 120 days curing periods. The water/cement ratio for all the mix was maintained at 0.5. The compressive strength results are desirable for each curing age at the 30% replacement of cement in which each SCM contributes 10% to the mix, greater strength value at curing age beyond 120 days compared to control sample was envisaged for this sample.

Abstract: In an effort to reduce the amount of cement in the concrete industry and produce greener concrete, emphasis was put on using several industrial by-products such as silica fume, fly ash and slag as partial replacements for cement in concrete. Due to the enormous number of mega reinforced concrete projects constructed in the United Arab Emirates, it is considered to be one of the largest consumers of high strength concrete in the region. On the other hand, only limited research has been done on high strength concrete incorporating local materials in the UAE. The main objective of this research is to conduct an investigation on the performance of high strength concrete containing silica fume as partial replacement of ordinary Portland cement incorporating superplasticizers and local UAE materials by studying its mechanical properties and durability. The experimental program involved two groups: The first group had a water-to-binder material ratio (w/b) of 0.4, whereas, the second group had w/b = 0.3. For both groups the silica fume replacement percentages were 0 (control mix) 5, 7.5, 10, 12.5, and 15 percent. The mechanical properties were tested at 7, 28, and 91 days and the durability tests were performed at 28 days. The results were compared to the control mix and they showed that for all the curing ages studied the use of silica fume as partial replacement of OPC has favorable effect on the compressive strength values and the optimum replacement ratios of silica fume for the tested specimens are found to be at 12.5% and 10% replacement for the w/b ratios of 0.3 and 0.4, respectively. For all the four performed durability tests the replacement of the OPC with silica fume is found to have favorable results and the higher the silica fume percentage replacement of OPC the more favorable the results are. The detailed description of the used mixes and the main conclusions drawn from this research are presented in this paper

Abstract: The new requirements for strength and durability have led to the development of Ultra High Performance concrete (UHPC) with outstanding mechanical properties and durability. However, the application of this type of concrete is exceptional, because of the high dosage of cement and the incorporation of expensive materials, such as silica fume (SF) whose dosage can reach 30% by weight of cement. This type of concrete is formulated on two bases: A fine granular skeleton (max diameter 630μm) and high cementitious materials content. The search for local materials to exploit them in the formulation of UHPC is the current trend. It is therefore necessary to control their effect on the behavior and evolution of cement hydration.The objective of this study is to highlight the influence of blast furnace (BFS) on hydration kinetics, linear endogenous shrinkage and chemical shrinkage at very early age (before 72h), drying shrinkage after hardening, as well as, the evolution of mechanical compressive strengths as a function of time. In addition, the exploitation of dune sand in the granular skeleton is an alternative to reduce the crushing energy and avoid microcracks possibly induced.The analysis of the results showed the interest of the use of the dune sand and the partial substitution of the cement by the BFS on the properties of the UHPCs in the fresh state and in the hardened state.In addition to the high performance achieved by UHPCs, their use, in Algeria, will meet both economic and ecological requirements given the abundance of very fine dune sand (southern Algeria) and complex blast furnace BFS of EL-Hadjar (Eastern Algeria).

Abstract: Hydration is a chemical reaction in which the major compounds in cement form chemical bonds with water molecules and become hydration products. By the process of hydration Portland cement mixed with sand, gravel and water produces the synthetic rock we call concrete. The Therefore, the concrete properties always accompanies with the hydration degree of cement. This paper presents some experimental test results on how silica fume affects the cement hydration in cement pastes of the Reactive Powder Concrete as increasing levels of silica fume addition with the content from 0% to 30% of cement mass. The hydration process of cement/silica fume paste was followed from the estimation of heat of hydration, rate of heat evolution, of binder pastes obtained by isothermal calorimetry (TAM-Air). In addition, the portlandite content, the hydration degree of pure cement, reaction degree of binder paste as well as reaction degree of silica fume were investigated. The quantitative assessment on these characteristics are due to the simulation of the hydration of Portland cement pastes containing silica fume.