It improves the durability of the concrete by reinforcing the microstructure through filler impact and hence diminished segregation and bleeding. Investigations on microsilica silica fume as partial cement replacement in concrete by faseyemi victor ajileye university of ibadan abstract now a day, we need to look at a way to reduce the cost of building materials, particularly cement is currently so high that only rich people and governments can afford meaningful construction. Condensed silica fume pennsylvania state university. This alternative is a fulldepth silica fume concrete bridge deck. An experimental program carried out by ravikumar et al. These properties indicated silica fume concrete would have a number of advantages when used for the repair of concrete structures. Pdf study of partial replacement of cement by silica fume.
Silica fume is very high in fineness and in silica content, and a very effective pozzolanic material depending on free lime content of cement use. Silica fume concrete silica fume is an artificial pozzolona having high pozzolonic activity. Cracking tendency and drying shrinkage of silica fume concrete for. Silica fume is a very common scm that is frequently used to increase the strength and durability of a concrete structure. Silica fume concrete transportation research board. Silica fume silica fume advise change to rheological, mechanical and chemical properties. Fumed silica is being used in various fields such as pharmaceuticals, paints, adhesives and sealants, plastics, rubber and ink except for concrete. Flexural behaviour of high performance reinforced concrete.
A pozzolan is a material that when in the presence of water has a chemical reaction and forms compounds that possess cementitious properties. The objective of this program was to establish a mix for the production of superior quality concrete using silica fume and type 10 cement at lower quantities. To optimize the benefits resulting from the use of condensed silica fume, it must be thoroughly dispersed in the cement mixture. It reacts with lime and water in a similar way to fly ash, also known as pulversided fuel ash pfa, to produce a binder. Because of its chemical and physical properties, it is a very reactive pozzolan. Silica fume is used in a variety of cementitious concrete, grouts and mortars, refractory, elastomer and polymer applications. What are the main effects of adding micro silica silica.
If the silica fume concrete contains superplasticizers, both the shear resistance and the cohesiveness of the concrete will be reduced, and improved flow will result. The influence of silica fume on the compressive strength. Effect of fly ash and silica fume on compressive strength. Concrete with silica fume early strength develop quickly, the corresponding concrete hydration heat dissipation quickly, resulting to rise concrete hydration heat temperature, easy to produce high temperature stress in the concrete, the stress concentration in the top of the dry shrinkage crack, make dry shrinkage crack extend even through the formation of transfixion cracks. A disadvantage to utilizing silica fume in cement is the cost. Structural cracking in reinforced concrete youtube. For both concrete compressive and tensile strength tests, the scc with silica fume gives the highest values followed by scc with fly ash and then pc concrete for all curing periods and conditions. Silica fume in shotcrete pennsylvania state university. Investigations on microsilica silica fume as partial. Silica fume advantages and disadvantages in concrete. Silica fume is used in powder form and specific gravity of silica fume is 2. It is a by product from an electric arc furnace used in manufacture of silicon metal or silicon alloy. Timedependent deformation, and consequently cracking, of concrete has been a growing concern. Concrete mix proportioning using micro silica proceedings of 4 th irf international conference on 19 april 2015, cochin, india, isbn.
Once again, this cohesiveness is due to its fine particle content. Silica fume is used in high performance concrete as a pozzolan to improve its properties. Test methods for chemical analysis, moisture content and loss on ignition, bulk density, specific surface, air entrainment of mortar, strength acitivity index. Used in the right proportion it can also reduce the overall cost of the concrete. Concrete containing silica fume requires particular attention to avoid. The combustion process creates silicon dioxide molecules, which condense to form particles. Silica fume concrete with an hrwr is more cohesive and sticky than conventional concrete. Silicafume concrete sfc has been used in bridges outside the united states since the.
The concrete was to exhibit superior durability characteristics when exposed to freezethaw, as well as resistance to other deleterious effects such as scaling, cracking and corrosion. This report addresses various matters relating to silica fume concretes. Silica fume is often used in highstrength concrete or highperformance concrete. These combined properties lead to an extended life expectancy in corrosive environments resistance to chlorides, acids and sulphates and improved strength. Tony kojundic is a founding board member of the silica fume association, and business manager for elkem materials in pittsburgh, pa. The compressive strengths of silica fume cement paste and mortar were evaluated at various watercementitious ratios. Silica fume is a pozzolanic material that is used with portland cement to produce portland pozzolana cement. Under hydrostatic pressure, other forms of waterproofing are required. Unfortunately, this book cant be printed from the openbook. The material shall composed of silica fume, mostly of amorphous silica. Five different watercementitious ratios were used including, 0.
Concrete has a coefficient of thermal expansion and contraction of about 10 x. This download a contains several papers, technical articles and two instructional videos on finishing, and curing, silica fume concrete an integral step in the producing crack free structures. In addition to its pozzolanic properties its is also a very good filler due to its particle size. Fresh and hardened properties of silica fume concrete is superior to conventional concrete. This specification covers silica fume for use in concrete and other systems containing hydraulic cement. Silica fume on the properties of concrete as defined in concrete society report 74, cementitious materials des king hon. Development of cracking patterns in modified cement matrix. High volume silica fume municipal waste facilities experience very rapid deterioration of the concrete slabs which are exposed to low ph leachate from waste and also subject to regular abrasion from loaders managing material from the slab. Concrete containing silica fume can have very high strength and can be very durable. Silica fume concrete is composed of cement, silica fume, fine aggregate, coarse aggregate, and water. Properties of the fumed silica and silica fume have been shown in. It is an excellent for use as a portland cement supplement. Guide to using silica fume in precastprestressed concrete products. Cracking tendency and drying shrinkage of silica fume concrete for bridge deck applications authors.
However, most often, in large concrete batches, silica fume is sufficiently dispersed during mixing operations of fresh concrete by the presence of coarse and fine aggregates. The alkalisilica reaction asr, more commonly known as concrete cancer, is a swelling reaction that occurs over time in concrete between the highly alkaline cement paste and the reactive noncrystalline silica found in many common aggregates, given sufficient moisture this reaction causes the expansion of the altered aggregate by the formation of a soluble and viscous gel of sodium. Silicafume microsilica concrete in bridges in the united states. These bridge decks were monitored both during construction and after construction to evaluate their. Read control of concrete cracking in bridges at nap. This causes flexural cracking initially in the constant moment region. Silica fume is available from suppliers of concrete admixtures and, when specified, is.
The durability of this type of concrete is superior to conventional concrete. Because of its extreme fineness and high silica content, silica fume is a very effective pozzolanic material. In addition to cement and aggregate, silica fume containing 81% sio2 and high range. Even though silica fume densifies concrete, it is not a waterproofer. Silica fume modified concrete sfmc is a concrete mixture used in rigid overlays to decrease the permeability of the concrete and thus increase the durability of the bridge deck. Silica fume consists primarily of amorphous noncrystalline silicon dioxide sio2. A programme of laboratory testing has been undertaken, focussing in the main on the properties. Concrete made with silica fume can dramatically increase corrosion resistance, decrease alkalisilica reactivity and increase resistance to sulfates. Are there any special requirements for placing, finishing and curing concrete with silica fume. Tests were performed on some 40 mixes made using silica fume as a replacement for. The condensed silica fumeportland cement mixture must be protected for the first 7 days from drying shrinkage.
What is fly ash, slag, and silica fume and why do we use them in concrete. It has many advantages and its advantages outweigh its disadvantages. This increased durability and resilience can be attributed to decreased permeability and absorption. Silica fume concrete is very susceptible to plastic shrinkage cracking owing to its lack of bleeding. 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. For instance, it has higher compressive and flexural strength. Free from the presence of salts that absorbs the moisture from the atmosphere and lead to efflorescence. There fore, immediate application of fog sprays or misting after placement is essential to avoid formation of plastic shrink age cracks in silica fume concrete ozyildirim 1991. The total length of the three gorges dam is about 2308m, the dam height is 185m, and the normal water storage level is 175 meters, and the investment is rmb 5 billion 200 million yuan. Table 7 gives the experimental moment at crack mcr, expt and the. Six fulldepth silica fume concrete bridge decks were constructed in minnesota between 1997 and 1999. In the wetmix process, the silica fume can be introduced as. Silica fume concrete silica fume for sale, microsilica. Benefits of using silica fume in concrete civil engineer.
Astm c1240 20 standard specification for silica fume. Because of its fine particles, large surface area, and the high sio2 content, silica fume is a very reactive pozzolan when used in concrete. Guide to using silica fume in precastprestressed concrete. The silica fume association operates under a cooperative agreement with the fhwa to help provide technology transfer on highperformance concretehpc to state and local transportation departments. Factors that reduce the rate or quantity of bleeding include high cementitious materials content, high fines content, reduced water content, entrained air, high concrete temperature, and thinner sections. Silica fume is an ultrafine material that is approximately 100 times smaller than the average cement particle. What are the disadvantages of silica fume in concrete. In this work, to make the concrete coarse aggregate of size 20mm, fine aggregates sand of zone, ordinary portland cement opc, and silica fume were mixed properly with appropriate. The use of silica fume concrete for fulldepth bridge deck. Pdf a calculation method of cracking moment for the high. Silica fume, cstr74, properties of concrete, effects, cementitious materials, high performance concrete. Silica fume sf is the byproduct of the manufacture of silicon for the computer industry.
Cracking tendency and drying shrinkage of silica fume. Silica fume is defined by the american concrete institute as very fine noncrystalline silica produced in electric arc furnaces as a byproduct of the production. 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. Because of its chemical and physical properties, it is a very reactive pozzolana. One disadvantage is low early strength development than portland ceme. The individual particles are extremely small, approximately 1100th the size of an average cement particle. Index terms silica fume, effects, cementations materials. If you need to print pages from this book, we recommend downloading it as a pdf. At least one loaded coal truck per minute travels toward the plant on. Silica fume is a mineral admixture, a very fine powder of spherical particles that average 0.
Many articles have described silica fume sf and its effect on portland cement concrete 24. It is a very finely divided material, many hundreds of times finer than cement. Due to the very high surface area of the silica fume and the usually very low water content of silica fume concrete, there will be very little bleeding of concrete. Fict, dip m, chartered mcim, dms consultant, united kingdom keywords. Silica fume is a byproduct of producing silicon metal or ferrosilicon alloys. Silica fume concrete is widely used in concrete and fiber cement industries. Fogging the air above the concrete and erecting windshades lessen the risk of plasticshrinkage cracking. A calculation method of cracking moment for the high strength. As part of a study conducted by the federal highway administration, a variety of methods have been applied to field structures suffering from asraffected expansion and cracking. Download citation cracking tendency and drying shrinkage of silica fume concrete for bridge deck applications this paper presents the results of a study of.