Concrete protection technical drawing installation in high resistivity mortars technical drawing minimum anode cover and edge distance technical drawing minimum coverage prepack mortar technical drawing typical installation details. On request, silica fume can be included in the mix to give reduced permeability. Both repairs were performed by the same contractor and in both cases consisted of partial and fulldepth repairs followed by a 2 4 in. Because plastic shrinkage cracking is due to a differential volume change in the plastic concrete, successful control measures require a reduction in the relative volume change. However, most existing inorganic repair materials for cement concrete pavement cracks have low interfacial bonding strength. Cracks are reported in units of length because the bridges are similar in size.
Finishing must be done immediately after screeding 95 71 curing compound and polyethylene sheeting should be applied to cure silica fume concrete as soon as finishing is completed if drying shrinkage cracking is to. 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. Structural repairs and applications requiring a highquality concrete at any consistency between stiff plastic and flowing where the quantities involved or placement conditions make the use of conventional readymixed concrete impractical. Because of the handling difficulties and the poor economics of transporting asproduced silica fume, it is rarely used in concrete. In these applications, the amount of silica fume is typically much greater than that used for other durability applications 15 percent by mass of cement or higher. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. Plastic shrinkage cracks plastic shrinkage cracks are caused by a rapid loss of water from the surface of concrete before it. Khedr and idriss 1995 studied the effectiveness of silica fume concrete in resisting damage caused by corrosion of embedded steel using an accelerated impressed voltagetesting setup. Silica fume can make a significant contribution to earlyage strength of concrete. Index highway concrete pavement technology development and. Benefits of using silica fume in concrete civil engineer. Sakrete selfconsolidating concrete mix is a dry, preblended, onecomponent, selfconsolidating, cementitious, polymermodified concrete mix containing coarse aggregate, silica fume, and an integral migrating corrosion inhibitor. 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.
In the present study, the effect of addition of a mix of silica fume and activated natural silica on the properties of concrete was investigated. Silica fume sf is the byproduct of the manufacture of silicon for the computer industry. Particles of silica fume are considerably smaller than particles of cement. Investigation of properties of highperformance fiber. Silica fume is recommended for all types of concrete where improved concrete performance with reduced permeability is required to reduce the effect of corrosive chemicals, such as deicing salts, on structural steel. Research done in 1983 showed even more pronounced benefits when silica fume was used in drymix shotcrete than when it was used in wetmix shotcrete. The advantages are the low permeability and high strength that result in higher durability. The steps involved in the repair of hairline cracks in concrete are as follows. On this project silica fume was added primarily to enhance constructability. Do you need a rapid setting mortar or one with extended working time. Evaluation of bridge deck overlays silica fume association.
In such cases, i ncreasing or restoring the structural bearing capacity is not possible us ing. One pound of silica fume produces about the same amount of heat as a pound of portland cement, and yields about three to five times as much compressive strength. Silica fume is also recommended where higher density and ultimate strengths are desired. Plastic shrinkage cracking national ready mixed concrete. The only maintenance and repair cost to the oshd was the sealing of cracks on one. Silica fume improves concrete in two ways the basic pozzolanic reaction, and a microfiller effect. One disadvantage is low early strength development than portland ceme. Selfconsolidating concrete is not available at this current time and we do not have an estimated time of restock. Despite low initial permeability, silica fume is not without limitations. Quality control of silica fume concrete bridge decks youtube. Silica fume is often used in highstrength concrete or highperformance concrete. Frost resistance of concrete with and without silica fume. 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.
It has strong adhesive properties allowing it to be applied down to a featheredge. The mechanism, physical characteristics, benefits, and production aspects of concrete made with silica fume are described. The exterior concrete walls in this structure are 4. Further, the use of very early strength durable materials will facilitate rapid and effective repairs, reduce traffic interruptions, and decrease longterm maintenance work.
Second, conduct a trial placement so the finishing crews can perfect their approach to the silicafume concrete. Fly ash increases workability when compared with conventional concrete with same water content. It has many advantages and its advantages outweigh its disadvantages. Apr 08, 2017 effect of fly ash and silica fume on concrete properties. Repair mortars meet your project goals with the right repair mortar. Fogging the air above the concrete and erecting windshades lessen the risk of plasticshrinkage cracking. However, silica fume has to be very finely dispersed in the concrete mix, because agglomerated flakes of compacted silica fume can themselves also induce asr if the dispersion process is insufficient. Because of its extreme fineness and high silica content, silica fume is a very effective pozzolanic material. Fumed silica is being used in various fields such as pharmaceuticals, paints, adhesives and sealants, plastics, rubber and ink except for concrete.
This makes silica fume concrete more susceptible than conventional concrete to rapid surface drying and plastic shrinkage cracking. Silica fume seminar report, ppt, pdf for civil engineering. Inspection of the crack is done and if any oil or stains have penetrated the crack and have discoloured the concrete, the stains will have to be addressed. Silica fume is not a new product by one company but is a major raw material that has been available over 40 years.
Fresh concrete containing silica fume is more cohesive and less. Guide to using silica fume in precastprestressed concrete. Using silica fume concrete repairs for abrasion erosion damage at. The silicafume mixture can be used to increase chemical resistance, the water resistance and erosion of hydraulic structures, and where a denser concrete is needed. Silica fume concrete has a gain in flexural strength from 5 th to 20 th days upon filling the voids, silica fume densifies the mix, this increases the tensile strength of concrete and hence there is a increase in flexural strength. Silica fume usage also made some progress in the 1980s. Cementitious, polymer modified, silica fume enhanced, fiber reinforced, air entrained, corrosion inhibitor. Properties of the fumed silica and silica fume have been shown in. Cracking may be due to plastic shrinkage and plastic settlement of concrete in. Cracking tendency and drying shrinkage of silica fume concrete for. Working with silicafume concrete concrete construction.
Once the cause and significance of the concrete cracking has been diagnosed by a qualified and licenced inspector, it is important that accurate repair methods are followed. This makes silicafume concrete more susceptible than conventional concrete to rapid surface drying and plastic shrinkage cracking. Masterlife sf 100 silica fume, may also be used in concrete to combat asr. Please select ok if you would like to proceed with this request anyway. Master builders solutions repair mortars meet multiple application requirements, while keeping your end goal in mind. The use of this pozzolan reduces both concrete permeability and the alkalis that react with the silica in the reactive aggregates. Cracking tendency and drying shrinkage of silica fume concrete. Silica fume enhanced to improve concrete durability. Silica fume can make highly cohesive, sticky concrete, with little bleeding capacity. Therefore, crack repair is necessary for improving the durability of concrete. Silica fume and kim media kryton international inc. Changing the composition of the concrete mixture alters such variables as alkalinity and silica fume, as well as modification to polymers.
This will produce expansive ettringite and cracking of the concrete. Two decades of readymixed high performance silica fume. The material shall composed of silica fume, mostly of amorphous silica. Silica fume is a pozzolanic material that is used with portland cement to produce portland pozzolana cement. 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. The length of crack was the greatest for the bridges with the silica fume overlays, bridges 1. Concrete made with silica fume can dramatically increase corrosion resistance, decrease alkali silica reactivity and increase resistance to sulfates. Inspection of the kinzua dam stilling basin has indicated that the. What are the disadvantages of silica fume in concrete. Astm c1240 20 standard specification for silica fume used. Two types of concrete overlays silica fume concrete sfc and latexmodified type iii portland cement concrete lmciii were installed and tested as part of the strategic highway research program shrp project c206. This increased densification of the concrete often creates an illusion of waterproofing capability.
Investigating a new method to assess the selfhealing performance. Silica fume, a byproduct of the ferrosilicon industry, is a highly pozzolanic material that is used to enhance mechanical and durability properties of concrete. Idot of a silica fume concrete bridge deck overlay. This is the first and foremost step in the repair of hairline cracks in the concrete. Recommendations are given for measuring, mixing, handling, transporting, placing, finishing, and curing concrete with silica fume additives. 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.
Vinyl concrete patcher is ideal for making smooth repairs to crack or chipped concrete floors, sidewalks or steps. Silica fume improves the characteristics of both fresh and hard concrete. This can be the case in laboratory studies made on cement pastes alone in the absence of aggregates. The use of silica fume in concrete shows a tendency for plastic shrinkage2, drying shrinkage3and cracking resulting in water penetration and corrosion of reinforcing steel. In addition to its pozzolanic properties its is also a very good filler due to its particle size. Silica fume concrete transportation research board.
Asproduced silica fume is frequently used in bagged construction products such as grouts and repair mortars. Properties of the fumed silica and silica fume have been shown in table 1. Silica fume has become the world standard for chloride corrosion situations and also to improve dramatically the water tightness of concrete structures. Silica fume has been used all over the world for many years in the area where high strength and durable concrete were required. Silica fume concrete sfc sfc is used where low permeability, high strength, and high durability are required. Silica fume concrete included 0%, 10%, 15%, 20%, and 25% silica as equal replacement of ordinary portland cement. Silica fume concrete is widely used in concrete and fiber cement industries. Silica fume concrete silica fume for sale, microsilica. Dry white fine silica sand is used with thin viscosity slab crack repair kits.
As such, ingredients that reduce bleeding in concrete, such as silica fume can lead to plasticshrinkage cracking, unless precautions are taken to protect the surface of the concrete immediately after placing and during early finishing operations. It is a very finely divided material, many hundreds of times finer than cement. If cracks occur before the concrete is sealed, this is often the material used to repair them. Learn how to repair concrete to fix all types of concrete problems, from crack to broken corners to full section replacement. Nov 12, 2018 as such, ingredients that reduce bleeding in concrete, such as silica fume can lead to plasticshrinkage cracking, unless precautions are taken to protect the surface of the concrete immediately after placing and during early finishing operations. With heavy modern traffic and natural factors, cement concrete pavement cracks have become increasingly serious. Concrete has a coefficient of thermal expansion and contraction of about 10 x 106 per c 5.
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. Cracking tendency and drying shrinkage of silica fume concrete for bridge deck applications. Concrete repair products and concrete repair systems. In the united states, silica fume is used predominantly to produce concrete with greater resistance to chloride. Surface cracks architectural repairs structural defects deep spalling exposed reinforcement rock pockets cracking transverse. The use of silica fume in concrete should be limited to specialized applications that can take full advantage of its unique properties. For example, after construction, strengthening water and sprinkler maintenance can decrease this problem, but the cracks are still unavoidable in many. Deterioration of concrete structures can happen for many reasons such as corrosion, structural damage, water infiltration etc. The use of good quality fly ash with a high fineness and low carbon content reduces the water demand of concrete. Tyler, skanska usa civil northeast unless batched, handled, and placed with tight controls and optimal conditions, silica fume decks can suffer wide spread cracking thru.
A study of frost resistance of nonairentrained concrete was carried out to explore the possibilities of making concrete with both high strength and high frost resistance. 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. Concrete for repair purpose requires high early strength. Polymermodified cement grout is the typical material used to fill pinholes and voids in concrete during manufacture. Second, conduct a trial placement so the finishing crews can perfect their approach to the silica fume concrete. Download technical drawings in either pdf or dxf formats. Silica fume, a byproduct in the manufacture of ferrosilicon and also of silicon metal, is a very efficient pozzolanic material, though there are some problems associated with its use in concrete.
These activities may include sealing, washing, caulking, crack repair, and other minor repairs intended to prolong the functionality of the bridge element. Mechanical properties improvement mechanism of silica fume. Ea mix 6 mm concrete repair wredline 51716 quikrete. The naturally occurring amorphous silica was activated by first treating it with alkali, after which it was neutralized by acid treatment. Study of concrete containing silica fume and activated. To prevent thermally induced cracking, the designer specified very tight control over the maximum temperature rise allowed in the concrete. Ultrafine cement, silica fume sf, and other admixtures, which are superfine and used to repair fine early cracks, are prepared as the mending material in. Designed for application thickness minimum of 1 and maximum thickness of 8.
Investigating rapid concrete repair materials and admixtures. Download citation cracking tendency and drying shrinkage of silica fume concrete for bridge deck applications this paper presents the results of a study of. The selected repair methods are based on an evaluation of the crack and the repair s objectives. Hairline crack in concrete causes, repair and prevention. It reacts with lime and water in a similar way to fly ash, also known as pulversided fuel ash pfa, to produce a binder. How to repair concrete pro tips for repairing concrete. Optimization of highway concrete technologybridge deck overlays. The specially formulated mix contains super plasticizer for improved durability and placement characteristics. Silica fume has also been used to provide increased resistance for concrete exposed to a variety of aggressive chemicals. What is the effect of silica fume on healing of concrete. This increased durability and resilience can be attributed to decreased permeability and absorption. Lowslump density concrete is used to increase the abrasion resistance of cracking concrete by creating a more durable shell. Crack repair materials for concrete are often polymermodified cement grouts, silicone or latex caulking, or epoxies. Explore silica fume with free download of seminar report and ppt in pdf and doc format.
Concrete repair products and systems have been developed extensively since the late 1970s, as more of the technology and requirements for durable concrete repairs has been increasingly understood. This increased level of expertise and experience led to the first development of a complete systems approach to concrete repair and. After 5 years in service, the overlays had cracked. When a micro crack occurs in a silica fume kim mix concrete, and water begins to penetrate the structure, kim will immediately react with the unhydrated cement particles and the water causing crystals to grow throughout the crack. Mar 10, 2014 protection of concrete structures from microbial degradation can be enhanced by treatments with biocides or adding protective coatings such as water repellents. The study objective was to see if microsilica concrete mc is a viable. The combustion process creates silicon dioxide molecules, which condense to form particles. With little or no bleed water on the surface, silica fume concrete is prone to plastic shrinkage cracking on hot, windy days. 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 of elemental silicon or alloys containing silicon. Silica fume advantages and disadvantages in concrete. Frost resistance of concrete with and without silica fume, and the effects of external loads.
It may be added directly to concrete as an individual ingredient or in a blend of portland cement and silica fume. Many years of research plus decades of practical experience have enabled sika to develop full comprehensive mortar solutions to repair, restore and rehabilitate concrete structures. These combined properties lead to an extended life expectancy in corrosive environments resistance to chlorides, acids and sulphates and improved strength. There are two general recommendations regarding finishing. Silica fume concrete has a gain in flexural strength from 5 th to 20 th days upon filling the voids, silica fume densifies the mix, this increases the tensile strength of concrete and hence there is a. This shotcrete has good volume stability, good freezethaw durability, and very low chloride permeability. 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. Typically, 510% by mass of the cement of silica fume is used along with a highrange water reducer that is required for workability. Causes, evaluation, and repair of cracks in concrete structures reported by aci committee 224 aci 224. Also explore the seminar topics paper on silica fume with abstract or synopsis, documentation on advantages and disadvantages, base paper presentation slides for ieee final year civil engineering ce or ieee civil construction btech, be, mtech students for the year 2017 2018. The procedures used to evaluate cracking in concrete and the principal techniques for the repair of cracks are presented.
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