High early compressive strength high tensile flexural strength and modulus of elasticity very low permeability to chloride and water intrusion enhanced. The ability of high c3a cement to complex with chlorides results in the formation of insoluble compound, able to reduce the mobility of free chloride ion to the reinforcement concrete surface. Silica fume, in dry densified form, or as a slurry, is added to the concrete mixture at the rate of 7. Effect of silica fume on concrete properties and advantages for kurdistan region, iraq article pdf available in international journal of scientific and engineering research 61. The reactivity of metakaolin is based on chemical composition and reactive surface. Comparison of compressive strength values for varying amounts of condensed silica fume aitcin, 1984 advantages. Even though silica fume densifies concrete, it is not a waterproofer. Used in the right proportion it can also reduce the overall cost of the concrete. Advantages and disadvantages of silica fume in concrete silica fume is a byproduct of producing silicon metal or ferrosilicon alloys. It does not contain crystalline water, does not participate in the curing reaction, and does not affect the reaction mechanism. For more information on silica fume in concrete, the silica fume association has published the silica fume users manual. Silica fume is a pozzolanic material that is used with portland cement to produce portland pozzolana cement.
High early compressive strength high tensile flexural strength and modulus of elasticity very low permeability to chloride and water intrusion enhanced durability increased toughness increased abrasion resistance on decks, floors, overlays and marine structures superior resistance to chemical attack from chlorides, acids, nitrates and sulfates and lifecycle cost efficiencies higher bond. Advantages and disadvantages of silica fume in concrete. What are the disadvantages of silica fume in concrete. Pdf production of highperformance silica fume concrete. Pdf advantages and disadvantages of silica fume in. Silica fume was replaced by dry weight of cement 10% at wc of 0. Due to the high performance concrete in water evaporation and condensation of microtubule contraction, make the concrete surface fission, anticarbonation of high performance concrete, freezethaw cycle effect and anti chloride ion diffusion is. The specific gravity of silica fume is generally in the range of 2. Silica fume is a byproduct in the carbothermic reduction of highpurity quartz with carbonaceous materials like coal, coke, woodchips, in electric arc furnaces in the production of silicon and ferrosilicon alloys. Pdf effect of silica fume on concrete properties and. However, not all refractory producers use undensified silica fume. Admixtures n use of admixtures is mandatory in highperformance concrete. The manual is a comprehensive guide for readymix and precast concrete producers, specifiers, and contractors that describes the best practices for the successful use of silica fume in the production of highstrength concrete.
Silica fume requires a high amount of water and needs to be used with a superplasticizer. Advantages and disadvantages of geopolymer concrete viiadvantages fristly, this is one of the primary advantages of geopolymers over traditional cements. Silica fume advantages and disadvantages in concrete silica. Silica fume concrete is too viscous and difficult to apply. This paper explores the merits and practical considerations of using both methods and how each is governed by. Founded in 1904 and headquartered in farmington hills, michigan, usa, the american concrete institute is a leading authority and resource worldwide for the development, dissemination, and adoption of its consensusbased standards, technical resources, educational programs, and proven expertise for individuals and organizations involved in concrete design.
Pdf advantages and disadvantages of silica fume in concrete. Effect of fly ash and silica fume on concrete properties. To achieve a maximum improvement in strength and durability, silica fume concrete should contain a high. Test methods for chemical analysis, moisture content and loss on ignition, bulk density, specific surface, air entrainment of mortar, strength acitivity index, reactivity with cement alkalis, and sulfate resistance of silica fume shall conform to this specification. What is fly ash, slag, and silica fume and why do we use them. Four types of concrete were prepared with 0%, 5%, 7. Utilization of silica fume in cement concrete paving block. One disadvantage is low early strength development than portland ceme. Silica fume is a byproduct of the silica alloy industry. Under hydrostatic pressure, other forms of waterproofing are required. Hence the concrete technology stepped towards the development of alternative building material which can fulfil these aspects and are locally available so as to reduce the cost of construction.
Ahmad 24 studied the effect of different percentage of silica fume ranged between 0% to 30%. The combustion process creates silicon dioxide molecules, which condense to form particles. Free from the presence of salts that absorbs the moisture from the atmosphere and lead to efflorescence. Dec 04, 2017 this video introduces fly ash, slag and silica fume and discusses their properties. The largest consumer of undensified silica fume is the refractories industry. Tests were performed on some 40 mixes made using silica fume as a replacement for cement in quantities of 15, 20, and 30 percent. Silica fume reduces the permeability of the concrete. Silica fume is a grey superfine powder with a density of 2. Kurdistan region, silica fume can either be addition added separately at the concrete mixer or incorporated into a factoryproduced composite cement. Silica fume consists primarily of amorphous noncrystalline silicon dioxide sio2. Specific advantages of silica fume in shotcrete are the improved bond strength of shotcrete to. Silica fume particles have an average diameter of less than 1 micron. Abstract this research describes the importance of the effect of silica fume on concrete properties and the advantages of its use in the kurdistan region, silica fume can either be addition added separately at the concrete mixer or incorporated into a factoryproduced composite cement. The ability of high c3a cement to complex with chlorides results in the formation of insoluble compound, able to reduce the mobility of free chloride ion to the reinforcementconcrete surface.
Reactive powder concrete composition and advantages. Fly ash increases workability when compared with conventional concrete with same water content. Effect of microsilica on mechanical properties of concrete. Concrete containing silica fume can have very high strength and can be very durable. The ash is nearly pure silica glass, which is much more reactive than crystalline silica i. The effect of silica fume only on concrete was give 61% increment in compressive strength, but with polymers together give about 72% increment, flexural strength increased from 3. Highly reactive metakaolin has become available as a considerably reactive pozzolanic material in concrete. It has many advantages and its advantages outweigh its disadvantages. Effects of silica fume on different properties of fresh and hardened concrete include.
Silica fume is used in concrete and shotcrete to increase strength, decrease permeability, and enhance cohesion and adhesion. Pdf effect of silica fume on workability and compressive. One field test also specified silica fume be added to the concrete mixture at a 4% addition rate. One of the most beneficial uses for silica fume is in concrete. The durability of this type of concrete is superior to conventional concrete. Disadvantages of silica fume in high performance concrete. Compared to opc concrete, the time to reach 3000psi traffic opening strength was delayed by 1 to 2 days for 30% replacement and by 3 to 4 days for 50% replacement. Pdf self compacting concrete using fly ash and silica.
The main advantage of silica fume is high durability. Furthermore, their use reduces the consumption of portland cement per unit volume of concrete. Fa, limestone fines and silica fume microsilica on the properties of concrete. Silica fume advantages and disadvantages in concrete silica advantages of silica fume in concrete.
An overview of advantages and disadvantages of autoclaved aerated concrete conference paper pdf. Chapters 1 and 2 provide basic information explaining what silica fume is and how it is used in concrete. The relative density of silica fume is generally in the range of 2. Its an ultrafine powder recovered from the production of silicon metals and alloys in electricarc furnaces. Fresh and hardened properties of silica fume concrete is superior to conventional concrete.
Its function is to fill the small voids and also to enhance flow properties of concrete. Silica fume advantages and disadvantages in concrete. Chapter 2 types of shotcrete and applications corps of. In general, supplementary cementitious materials improve the consistency and workability of fresh concrete because an additional volume of fines is added to the mixture. Because of its extreme fineness and high silica content, silica fume is a very effective pozzolanic material. It should be selected in such a way that it should contain less quantity of impurities in it. This type of material is not like other admixtures for example fly ash, blast furnace slag, and silica fumes in terms of production because it is produced. Four silica fume concrete mixes with silica fume contents of 5%, 10%, 15%, and 20% of the total cementitious material content were prepared along with one plain portland cement concrete mix and. Silica fume consists primarily of amorphous noncrystalline. Traditionally used in highrise buildings for the benefit of smaller columns increasing usable space highstrength concrete containing silica fume is often used in precast and prestressed girders allowing longer spans in structural bridge designs. Supplementary cementitious materials such as fly ash, slag and silica fume enable the concrete industry to use hundreds of millions of tons of byproduct materials that would otherwise be landfilled as waste.
The bulk density uncompacted unit weight of silica fume varies from to 430 kgm3 8 to 27 lbft3. Nishanth premhar the effect of silica fume sf various strength properties of replacement of cement, coarse aggregate. The water demand of concrete containing silica fume increases with increasing amounts of silica fume, see carette and malhotra and scali et al. Because of its chemical and physical properties, it is a very reactive pozzolan. The effect of silica fume on the properties of concrete. Silica fume improves concrete through two mechanisms. Greatly reduces permeability due to the small particle size. Pdf an overview of advantages and disadvantages of. For instance, it has higher compressive and flexural strength. Different chapters of the manual may be of interest to concrete specifiers, concrete producers, concrete contractors, or concrete inspectors. Micro silica particles are 100 times smaller than cement particles. Benefits of using silica fume in concrete civil engineer. Fly ash, slag, silica fume, and natural pozzolans, chapter 3.
However, by 14 days, the grade 120 slag cement concrete strength equaled or surpassed that of opc concrete. Silica fume concrete is composed of cement, silica fume, fine aggregate, coarse aggregate, and water. The use of varying amounts of condensed silica fume as an additive for a cement grout to increase strength can be seen below in figure 14. Concrete with silica fume is typically used at low water contents with high range water reducing admixtures and these mixtures tend to be cohesive and stickier. The positive reactions created by nano silica in uhpc are similar to silica fume or micro silica which are in terms of performance strength and durability enhancement. Properties of the fumed silica and silica fume have been shown in table 1. Many materials are used for these purposes like ground granulated blast furnace slag ggbs, rice husk ash rha, silica fume, fly ash etc. Fresh concrete containing silica fume is more cohesive and less. Highstrength concrete enhanced with silica fume provides architects and engineers with greater design flexibility. Vw gti and golf r to get dramatic tech update, improved handling.
This increase is caused primarily by the high surface area of the silica fume. At 28 days of age, the ultrasonic pulse velocities through each concrete specimen. Effects of ground granulated blast furnace slag in. High performance concrete hpc containing silica fume has been identified as one of the more important advanced materials necessary in the effort to rebuild the nations infrastructure. Studies by qing, zenan 56, showed that concrete with addition of nano silica gained early strength as compared to that of silica fume. Addition of silica fume to concrete im proves its durability through reduction in the permeability and refined pore structure, leading to a reduction in the diffu sion. The gain in strength can be attributed to the formation of calcium silicate hydrate. Silica fumes advantages concrete construction magazine. Apr 16, 2016 silica fume is a pozzolanic material that is used with portland cement to produce portland pozzolana cement. These properties indicated silica fume concrete would have a number of advantages when used for the repair of concrete structures. Silica fume is generally obtained from ferrosilicon industries. The price of silica fume is relatively high compared to cement and fly ash.
Silica fume is a byproduct of producing silicon metal or ferrosilicon alloys. In addition to increased strength and enhanced durability, hpc produced with silica fume delivers increased toughness, increased resistance to abrasion, corrosion and chemicals, sustainability and. Fumed silica is being used in various fields such as pharmaceuticals, paints, adhesives and sealants, plastics, rubber and ink except for concrete. Silica fume is a very fine noncrystalline pozzolanic material composed mostly of silica. Some have been very successful in developing technology that allows them to use 40 lbsft3 densified silica fume to take advantage of the benefits of reduced shipping costs. Results from previous works indicated that geopolymer concrete exhibited better mechanical strength and durability properties than ordinary. Advantages and disadvantages of silica fume in concrete pdf. Effect of silica fume on concrete properties and advantages. It is observed that up to 12% replacement of cement with silica fume the compressive strength increases with increasing dose of silica fume and then reduces slightly. The material shall composed of silica fume, mostly of amorphous silica. Astm c1240 20 standard specification for silica fume. Based on this test the specific surface of silica fume typically ranges from 15,000 to 30,000 m kg. Silica fume concrete shrinkage rate is large, especially early dry shrinkage, easy to make crack in the application of silica fume concrete, affect the overall strength and using effect.