The use of silica fume concrete for fulldepth bridge deck. Effect of silica fume on concrete properties and advantages. Study of concrete containing silica fume and activated. These combined properties lead to an extended life expectancy in corrosive environments resistance to chlorides, acids and sulphates and improved strength. The tensile creep behavior is extremely important in crack prediction and stress analysis of concrete.
See the actual devices and tests used in todays video featuring dr. Silica fume concrete transportation research board. This presentation covers all aspects of using silica fume in concrete and can be viewed directly in your browser. 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. 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. If temperature differences between the concrete surface and its interior are high, cracking can occur.
Effects of steel fibre and silica fume on impact behaviour. Silica fume has become the world standard for chloride corrosion situations and also to improve dramatically the water tightness of concrete structures. Silica fume reduces the permeability of the concrete. This research focuses on concrete with a water binder ratio of 0. 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. This can be the case in laboratory studies made on cement pastes alone in the absence of aggregates. Condensed silica fume in concrete transportation research board. Silica fume particles have an average diameter of less than 1 micron. Pdf performance of corrosion inhibitors in cracked and. It is an ultrafine powder collected as a byproduct of the silicon and ferrosilicon alloy production and consists of spherical particles with an average particle diameter of 150 nm. Trial placements and supervision by a suppliers re p re s e n t a tive can be useful in training workers to finish silica fume concre t e. Effect of silica fume in concrete workability the incorporation of silica fume in concrete can improve the stability of concrete, which can reduce the segregation and bleeding of concrete.
The combustion process creates silicon dioxide molecules, which condense to form particles. Results indicate that the free shrinkage for different concretes does not depend on the unit water content or weight loss and that highstrength silica fume concrete shows higher shrinkage and lower creep. The silica fume concrete was slightly darker in color than the latexmodified concrete. It has many advantages and its advantages outweigh its disadvantages. Fresh concrete containing silica fume is more cohesive and less.
This area contains information and resources of special interest to anyone involved with producing, or placing silica fume concrete. Even though silica fume densifies concrete, it is not a waterproofer. 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. Silica fume is used in high performance concrete as a pozzolan to improve its properties. It discusses the nature and types of condensed silica fume, physical characteristics, product variation and problems involved in its handling and transportation. Development of high performance concrete and evaluation of. 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. In the wetmix process, the silica fume can be introduced as.
This study investigated the impact resistance and mechanical properties of steel fiberreinforced concrete with watercement ratios of 0. Silica fume consists primarily of amorphous noncrystalline silicon dioxide sio2. As a result of recent concrete research, new mixes were created incorporating various quantities of fly ash, silica fume, metakaolin, polycarboxylate ether superplasticizers, and caltite waterproofing admixture. As with the silica fume overlay, these cracks, in variable depth overlay areas, did not extend through the entire depth of the overlay and measured 0. Silica fume concrete is widely used in concrete and fiber cement industries. More details on working with silica fume concrete in. Tests were performed on some 40 mixes made using silica fume as a replacement for cement in quantities of 15, 20, and 30 percent. Concrete with silica fume is typically used in applications where cracking may be a major concern. Provided silica fume high strength concrete is cured for 24hrs shrinkage is likely to be similar or less than normal concrete. Aci concrete terminology silica fume, a byproduct of the ferrosilicon industry, is a highly pozzolanic material that is used to enhance mechanical and durability properties of concrete. Silica fume is also recommended where higher density and ultimate strengths are desired. Six fulldepth silica fume concrete bridge decks were constructed in minnesota between 1997 and 1999. Microsilica in concrete improves its strength and durability as it provides more uniform distribution and a greater volume of hydration products, and decreases the average size of pores in the cement paste.
Supplementary cementitious materials significantly delay set time can increase the risk of plastic shrinkage cracking. From this point of view, cement and concrete industries can be considered to be environmentfriendly since a large amount of waste materials, such as fly ash, blast furnace slag, metakaolin and silica fume in cement and concrete industries is helpful for both manufacturing cementitious products with improved properties and for reducing the. Alkaliaggregate reaction portland cement association. The impact resistance and mechanical properties of fiber reinforced. However, for hpc, autogenous shrinkage contributes quite significantly and in some cases hpc with high volume silica fume it could be as high as drying. In such cases, i ncreasing or restoring the structural bearing capacity is not possible us ing. For instance, it has higher compressive and flexural strength. 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. Quality control of silica fume concrete bridge decks youtube. Newly added to this download is a software program that uses acis 305 evaporation. The length of crack was the greatest for the bridges with the silica fume overlays, bridges 1, 4, and 5. Mar 28, 2016 what are the main effects of adding micro silica silica fume on concrete properties. This download a contains several papers, technical articles and two instructional videos on finishing, and curing, silicafume concretean integral step in the producing crack free structures. These properties indicated silica fume concrete would have a number of advantages when used for the repair of concrete structures.
Silica fume, a byproduct of the ferrosilicon industry, is a highly pozzolanic material that is used to enhance mechanical and durability properties of concrete. Properties of the fumed silica and silica fume have been shown in table 1. General information ku mix silica fume users manual crack free concrete evaporation program finishing videos. Silica fume sf is the byproduct of the manufacture of silicon for the computer industry. 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. Apr 08, 2017 effect of fly ash and silica fume on concrete properties. Silica fume will increase the autogenous shrinkage of the cement slurry, and the amount of inclusion will exceed 5%, which may increase the risk of cracking. Combined effect of silica fume and steel fibers on the.
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. The exterior concrete walls in this structure are 4. Chapters 1 and 2 provide basic information explaining what silica fume is and how it is used in concrete. A pozzolan is a material that when in the presence of water has a chemical reaction and forms compounds that possess cementitious properties. Silica fume powder is gray to offwhite in color when silica fume is used in concrete, shotcrete and repair products, it performs as a filler, improving the physical structure by occupying the spaces between the cement particles, and as a reacting chemical pozzolanic to create greater strength and durability to concrete. Causes, evaluation, and repair of cracks in concrete structures reported by aci committee 224 aci 224. Recommendations are given for measuring, mixing, handling, transporting, placing, finishing, and curing concrete with silica fume additives. 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. To optimize the benefits resulting from the use of condensed silica fume, it must be thoroughly dispersed in the cement mixture.
One disadvantage is low early strength development than portland ceme. The impact resistance and mechanical properties of fiber reinforced self compacting concrete scc containing nanosio 2 and silica fume. Then for each case the cement is replaced by 5%, 10%, 15% and 20% of silica fume. What are the disadvantages of silica fume in concrete.
Five different watercementitious ratios were used including, 0. This alternative is a fulldepth silica fume concrete bridge deck. Chapter 10 summarizes research needs for using silica fume in concrete. Reaction products of densified silica fume agglomerates in concrete the writers are pleased to dedicate this small contribution to the memory of professor h.
Silicafume concrete needs superplasticizers using silica fume in concrete re q u i r es using another innovation in conc r ete technology. The individual particles are extremely small, approximately 1100th the size of an average cement particle. Some specific meatroubleshooting concrete cracking during. Finishing the biggest difference between conventional concrete and silicafume concrete shows up during finishing. Nanoengineering concrete properties for enhanced performance. The use of silica fume in concrete shows a tendency for plastic shrinkage2, drying shrinkage3 and cracking resulting in water penetration and corrosion of. Silica fume concrete silica fume for sale, microsilica. In most concrete, aggregates are more or less chemically inert. Silica fume can make highly cohesive, sticky concrete, with little bleeding capacity. Cracking for highstrength silica fume concrete develops much faster and is signijcantly wider than that of normalstrength concrete. How to measure the impact of colloidal silica on strain. Silica fume is an ultrafine material that is approximately 100 times smaller than the average cement particle.
Methods mix proportioning of grade m35 and m40 was performed as per is 10262. The procedures used to evaluate cracking in concrete and the principal techniques for the repair of cracks are presented. With little or no bleed water on the surface, silica fume concrete is prone to plastic shrinkage cracking on hot, windy days. Summary of cracks, delaminations, and patches after overlay placements.
Silica fume has little use without them because its water demand is so high when used alone. This download a contains several papers, technical articles and two instructional videos on finishing, and curing, silicafume concretean. Even the most dense silica fume concrete cannot stop water penetration through micro cracks. Silica fume has been used all over the world for many years in the area where high strength and durable concrete were required. The latter evidence is used to support the theory that silica fume strengthens concrete by strengthening the bond between cement paste and aggregate. In outcome, hvgpshcc formulations with gp replacement of fly ash of up to 100 %. These bridge decks were monitored both during construction and after construction to evaluate their constructability and performance. Silica fume improves the characteristics of both fresh and hard concrete. Microsilica, also known as silica fume or condensed silica fume. Adds cohesiveness and reduced bleeding improves strength and durability. May 24, 2018 in the reported study, the performance of some generic and proprietary inhibitors in inhibiting corrosion of reinforcing steel in cracked and uncracked silica fume cement concrete beams was evaluated.
However, some aggregates react with the alkali hydroxides in concrete, causing expansion and cracking over a period of many years. Inclusion of fly ash and silica fume will generally increase the amount of entrapped air in a concrete mix. It is an excellent for use as a portland cement supplement. Silica fume and kim media kryton international inc.
However the pozzolanic reactions may counterbalance the uptake of calcium hydroxide, according. Silica fume and metakaolin admixtures are formulated to produce extremely strong and durable concrete. 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. To prevent thermally induced cracking, the designer specified very tight control over the maximum temperature rise allowed in the concrete. Troubleshooting concrete cracking during construction. Unless batched, handled, and placed with tight controls and optimal conditions, silica fume decks can suffer wide spread cracking thru several mechanisms. Effect of silica fume in concrete as a concrete admixture, silica fume has a certain influence on the performance of concrete.
Silica fume, also known as microsilica, cas number 69012642, einecs number 2737611 is an amorphous noncrystalline polymorph of silicon dioxide, silica. Silica fume is not a new product by one company but is a major raw material that has been available over 40 years. In an experimental investigation, the minimum length of curing of silica fume concrete was determined and compared with that of plain portland cement concrete and fly ash concrete. Jan 26, 2017 silica fume concrete silica fume is an artificial pozzolona having high pozzolonic activity. Fogging the air above the concrete and erecting windshades lessen the risk of plasticshrinkage cracking. Adding higher amounts of silica fume reduces bleeding and may eliminate it. Plastic shrinkage cracks should be distinguished from other early or prehardening cracks caused by settlement of the concrete around reinforcing bars, formwork movement, early age thermal cracking, or differential settlement at a change from a thin to a deep section of concrete. Different chapters of the manual may be of interest to concrete specifiers, concrete producers, concrete contractors, or concrete inspectors. Keywords shotcrete, silica fume, crack resistance, expansive agent, internal. On this project silica fume was added primarily to enhance constructability. Cracks are reported in units of length because the bridges are similar in size. Taylor, who over so many years contributed so much to the field of cement chemistry. It is a byproduct of the industrial manufacture of ferrosilicon and metallic silicon in hightemperature electric arc furnaces.
It is a by product from an electric arc furnace used in manufacture of silicon metal or silicon alloy. Shrinkage reducers these liquid admixtures astm c494 type s for concrete dramatically reduce drying shrinkage and the potential for drying shrinkageinduced cracking and curling. To control plastic shrinkage cracks, reduce the rate at which surface m o i s t u r e evaporates and prevent excessive bleeding. The higher proportion of silica fume may cause more cracks. Silica fume is a very common scm that is frequently used to increase the strength and durability of a concrete structure.
The mechanism, physical characteristics, benefits, and production aspects of concrete made with silica fume are described. The current study is aimed at disclosing the possibilities of reengineering. The impact resistance and mechanical properties of fiber reinforced selfcompacting concrete scc containing nanosio 2 and silica fume. Reaction products of densified silica fume agglomerates in. Experimental research on the effect of silica fume on tensile. Silica fume a dry, densified microsilica silica fume powder designed to increase concrete compressive and flexural strengths, increase durability, reduce. 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. What are the main effects of adding micro silica silica fume. This makes silicafume concrete more susceptible than conventional concrete to rapid surface drying and plastic shrinkage cracking. Silica fume concrete included 0%, 10%, 15%, 20%, and 25% silica as equal replacement of ordinary portland cement. The use of good quality fly ash with a high fineness and low carbon content reduces the water demand of concrete.
Abstract in september 1999, bridges a and b of contract tboi003511l0044 were overlaid with a silica fume concrete surface. Lower heat of hydration and less risk of thermal cracking. Benefits of using silica fume in concrete civil engineer. Figure 6 shrinkage of silica fume high strength concrete. The naturally occurring amorphous silica was activated by first treating it with alkali, after which it was neutralized by acid treatment. 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. It is a mineral admixture composed of very fine solid glassy spheres of silicon dioxide. They had been proved in highperformance concrete, which was placed. A balanced view is presented of the effect of condensed silica fume on the physical, chemical, mechanical, and durability aspects with respect to cement pase, mortar and concrete. Note that the coverage in chapters 7, 8, and 9 is somewhat brief. The construction was funded with 20% virginia department of transportation maintenance funds and 80% special istea section 6005 federal funds specifically allocated to demonstrate overlay technologies. Silicafume microsilica concrete in bridges in the united states.
Burnett csr days drying time microstrain 0 10203040 50607080 90 0 200 400 600 800 90 mpa 80 mpa 60 mpa figure 7 teamwork for silica fume high strength. Silica fume concrete technology questions and answers. Microsilica in concrete types, properties, and practical. Free from the presence of salts that absorbs the moisture from the atmosphere and lead to efflorescence. Produced through a partnership program between the sfa and the federal highway administration. Silica fume sf modifies interfacial transition zone between cement paste and aggregate at the micro level. The material shall composed of silica fume, mostly of amorphous silica. It is easy to cause cracks in mortar and concrete and need concrete maintenance. The authors disclosed receipt of the following financial support for the. Effect of silica fume in concrete silica fume supplier. Properties of sustainable concrete containing fly ash, slag and recycled concrete aggregate. Working with silicafume concrete concrete construction.
The least cracking occurred on bridge 6, with the conventional lmc overlay. Silica fume high strength concrete scancem materials. Designed for application thickness minimum of 1 and maximum thickness of 8. It is a very finely divided material, many hundreds of times finer than cement. 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. Making silica fume concrete in the laboratory pdf producing crack free concrete structures. This study is designed to explain the contradictory evidence and establish the role played by.
The bridges are located on interstate 35 in carter county, l. Under hydrostatic pressure, other forms of waterproofing are required. Silica fume concrete is composed of cement, silica fume, fine aggregate, coarse aggregate, and water. It reacts with lime and water in a similar way to fly ash, also known as pulversided fuel ash pfa, to produce a binder.
One silicafumeconcrete feature that required particular attention was the need to take measures to prevent plastic shrinkage cracking. Fresh and hardened properties of silica fume concrete is superior to conventional concrete. Astm c1240 20 standard specification for silica fume used. Used in the right proportion it can also reduce the overall cost of the concrete. Hooked steel fibers with 60mm length and an aspect ratio of 80, with three volume fractions of 0%, 0. The influence of silica fume on the compressive strength of. 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. Latexmodified and silica fume concrete overlays were placed on six bridges on i95 south of emporia, virginia, in the fall of 1994. A disadvantage to utilizing silica fume in cement is the cost. It may be added directly to concrete as an individual ingredient or in a blend of portland cement and silica fume. Silica fume is a grey superfine powder with a density of 2. The condensed silica fume portland cement mixture must be protected for the first 7 days from drying shrinkage. Cip 5 2014 national ready mixed concrete association. Properties of both fresh and hardened silica fume concrete are affected significantly compared to normal concrete.
Fumed silica is being used in various fields such as pharmaceuticals, paints, adhesives and sealants, plastics, rubber and ink except for concrete. Development of cracking patterns in modified cement matrix. Silica fume can hasten strength development and reduce curing time. Silica fume concrete is important in limiting the amount of chloride ion penetrating the overlay. Concrete mix proportioning using micro silica proceedings of 4 th irf international conference on 19 april 2015, cochin, india, isbn. This technical bulletin describes the steps required to adjust concrete mix proportions to accommodate the addition of drydensified silica fume more tb0708 shrinkage characteristics of silica fume. In the reported study, the performance of some generic and proprietary inhibitors in inhibiting corrosion of reinforcing steel in cracked and uncracked silica fume cement concrete beams was evaluated. How do you measure strain and cracking in concrete. In addition to its pozzolanic properties its is also a very good filler due to its particle size. Published on march 28, 2016 march 28, 2016 39 likes comments. Effect of expansive agent and internal curing agent on crack.