The results for the different ages of silica fume based geopolymer concrete are shown in fig. This alternative is a fulldepth silica fume concrete bridge deck. Produced through a partnership program between the sfa and the federal highway administration. Silica fume, also known as microsilica, cas number 69012642, einecs number 2737611 is an amorphous noncrystalline polymorph of silicon dioxide, silica. Evapre can be used with the meadowpatch and meadowcrete line of repair mortars from w. Silica fume concrete silica fume is an artificial pozzolona having high pozzolonic activity. Replacing cement with silica fume and observing the efficiency factor of silica fume, a lower maximum temperature rise and temperature. The material shall composed of silica fume, mostly of amorphous silica.
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 recommended that specifications for silica fume concretes in bridge deck construction include a provision for 7day continuous moist curing of exposed surfaces. Shrinkage of plain and silica fume cement concrete under hot. Cracking is dangerous due to many reasons like reduced strength and reduced durability. To optimize the benefits resulting from the use of condensed silica fume, it must be thoroughly dispersed in the cement mixture. Apr 16, 2016 silica fume is a pozzolanic material that is used with portland cement to produce portland pozzolana cement. Silica fume is a pozzolanic material that is used with portland cement to produce portland pozzolana cement. Effect of fly ash and silica fume on compressive strength of.
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. Effect of micro silica on the strength of concrete with ordinary portland cement. Silica fume high strength concrete scancem materials. Silica fume sf is the byproduct of the manufacture of silicon for the computer industry.
Working with silicafume concrete concrete construction. Silica fume concrete is widely used in concrete and fiber cement industries. This specification covers silica fume for use in concrete and other systems containing hydraulic cement. Second, conduct a trial placement so the finishing crews can perfect their approach to the silica fume concrete. The effect of condensed silica fume on the strength development in concrete was studied by replacement of 0, 5, 10, and 20% cement by silica fume. The influence of silica fume on the compressive strength. Silica fume has become the world standard for chloride corrosion situations and also to improve dramatically the water tightness of concrete structures. In addition to its pozzolanic properties its is also a very good filler due to its particle size. It is an excellent for use as a portland cement supplement. Figure 6 shrinkage of silica fume high strength concrete.
Under hydrostatic pressure, other forms of waterproofing are required. Effect of fly ash and silica fume on concrete properties. Properties of the fumed silica and silica fume have been shown in. Five different watercementitious ratios were used including, 0. Cement replacement up to 10% with silica fume leads to increase in compressive.
Silica fume has been used all over the world for many years in the area where high strength and durable concrete were required. Many articles have described silica fume sf and its effect on portland cement concrete 24. This presentation covers all aspects of using silica fume in concrete and can be viewed directly in your browser. Silica fume is a very common scm that is frequently used to increase the strength and durability of a concrete structure. Silica fume is an ultrafine material that is approximately 100 times smaller than the average cement particle. 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. In the wetmix process, the silica fume can be introduced as. It has been found experimentally that very high strength silica fume concretes undergo early cracking when deformation is restrained.
What are the disadvantages of silica fume in concrete. Fly ash increases workability when compared with conventional concrete with same water content. Compressive strength of silica fume based geopolymer concrete. It is a very finely divided material, many hundreds of times finer than cement.
Aci education bulletin e3 american concrete institute. Joe nasvik retaining moisture in concrete is a good thing if the ultimate goal is a good curing condition, but what if you must install finished flooring materials requiring low concrete relative humidity rh. One disadvantage is low early strength development than portland ceme. 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 results in a higher surfacetovolume ratio and a much faster pozzolanic reaction. Causes, evaluation, and repair of cracks in concrete structures reported by aci committee 224 aci 224. Silica fume concrete transportation research board. Silica fume is also recommended where higher density and ultimate strengths are desired. 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. Basf warrants this product to be free from manufacturing. The euclid chemical company euclid solely and expressly warrants that its products shall be free from defects in materials and workmanship for one 1 year from the date of purchase. All information in this publication is provided as is without warranty of any kind, either express or implied, includ. Concrete made with silica fume can dramatically increase corrosion resistance, decrease alkalisilica reactivity and increase resistance to sulfates.
These bridge decks were monitored both during construction and after construction to evaluate their. It has many advantages and its advantages outweigh its disadvantages. 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 not a new product by one company but is a major raw material that has been available over 40 years. Standard specification for silica fume used in cementitious mixtures, astm international. The condensed silica fumeportland cement mixture must be protected for the first 7 days from drying shrinkage. A disadvantage to utilizing silica fume in cement is the cost. 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. Aci education bulletin e3 supersedes e301 and was published august 20. Cracking tendency and drying shrinkage of silica fume. The use of silica fume concrete for fulldepth bridge deck.
Nevertheless, for a more widespread use of expanded waste glass aggregate in concrete for longterm stability in wet environments needs to be investigated. These combined properties lead to an extended life expectancy in corrosive environments resistance to chlorides, acids and sulphates and improved strength. Silica fume is often used in highstrength concrete or highperformance concrete. Second, conduct a trial placement so the finishing crews can perfect their approach to the silicafume concrete. Properties of the fumed silica and silica fume have been shown in table 1. This makes silicafume concrete more susceptible than conventional concrete to rapid surface drying and plastic shrinkage cracking. The industry standard for repair or replacement for cracked concrete is greater. Ask if the contractors offer any type of warranty on their work. This study presents an experimental study on selfcompacting concrete scc with two cement content. Silica fume a dry, densified microsilica silica fume powder designed to increase concrete compressive and flexural strengths, increase durability, reduce. The influence of silica fume on the compressive strength of. As expected, the shrinkage strains in both the plain and silica fume cement. Placing silica fume concrete to repair a spillway floor damaged by cyclic freezing and thawing and. What are the main effects of adding micro silica silica fume.
Silica fume consists primarily of amorphous noncrystalline silicon dioxide sio2. It is a by product from an electric arc furnace used in manufacture of silicon metal or silicon alloy. What are the main effects of adding micro silica silica fume on concrete properties. Silica fume is used to increase strength and durability of concrete, but generally requires the use of superplasticizers for workability. What are the main effects of adding micro silica silica. This download a contains several papers, technical articles and two instructional videos on finishing, and curing, silicafume concretean. Warranty information midwest concrete professionals. Concrete with silica fume is typically used in applications where cracking may be a major concern.
Concrete made with silica fume can dramatically increase corrosion resistance, decrease alkali silica reactivity and increase resistance to sulfates. Effect of fly ash and silica fume on compressive strength. Published by the fhwa and ncbc, hpc bridge views is a bimonthly newsletter providing timely information on high performance concrete as it. Study of concrete containing silica fume and activated. 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. 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. 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. The work involves three types of mixes, the first consisted of different percentages of fly ash fa, the second uses different percentages of silica fume sf, and the third uses a mixture of fa and sf. 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.
These bridge decks were monitored both during construction and after construction to evaluate their constructability and performance. Effect of age on compressive strength of silica fume based geopolymer concrete. It reacts with lime and water in a similar way to fly ash, also known as pulversided fuel ash pfa, to produce a binder. The product is designed to be used as a repair concrete in situations requiring a highquality concrete with a maximum aggregate size of 10 mm 38 inch. Shrinkage reducers these liquid admixtures astm c494 type s for concrete dramatically reduce drying shrinkage and the potential for drying shrinkageinduced cracking and curling. Steel reinforcement is optional, but is often used to contain cracks. Effect of silica fume in concrete on mechanical properties and. Because of its fine particles, large surface area, and the high sio2 content, silica fume is a very reactive pozzolan when used in concrete. The optimum silica fume replacement percentage for obtaining maximum 28 days strength of concrete ranged from 10 to 20 % 45. This will produce expansive ettringite and cracking of the concrete. Silica fume concrete silica fume for sale, microsilica. 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. The condensed silica fume portland cement mixture must be protected for the first 7 days from drying shrinkage.
Notes accompany each slide with extensive comments and references. In the united states, silica fume is used predominantly to produce concrete with greater resistance to chloride. Since the silica fume based geopolymer concrete are subjected to thermal curing for a period of 6 h and kept in a room temperature for a desired period. Mar 28, 2016 what are the main effects of adding micro silica silica fume on concrete properties. There are two general recommendations regarding finishing. Learn how to reduce the amount of moisture in concrete floors by. 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. Usually, cracks just pass through mortar, and propagate along the interfaces. Astm c1240 20 standard specification for silica fume used. Silica fume, a byproduct of the ferrosilicon industry, is a highly pozzolanic material that is used to enhance mechanical and durability properties of concrete. Standard specification for silica fume used in cementitious mixtures. It is a mineral admixture composed of very fine solid glassy spheres of silicon dioxide.
If a crack appears, we may be able to assist in the prevention of further cracking. The use of good quality fly ash with a high fineness and low carbon content reduces the water demand of concrete. Silica fume improves the characteristics of both fresh and hard concrete. Used in the right proportion it can also reduce the overall cost of the concrete. When a microcrack occurs in a silica fumekim mix concrete, and water begins to penetrate the structure, kim will immediately react with the unhydrated cement. Concrete containing silica fume is more sensitive to changes in wcm than conventional concrete in terms of the shrinkage that develops at early ages. The procedures used to evaluate cracking in concrete and the principal techniques for the repair of cracks are presented. This makes silica fume concrete more susceptible than conventional concrete to rapid surface drying and plastic shrinkage cracking. Provided silica fume high strength concrete is cured for 24hrs shrinkage is likely to be similar or less than normal concrete. Frequently asked questions faqs about concrete driveways. The naturally occurring amorphous silica was activated by first treating it with alkali, after which it was neutralized by acid treatment. A wide variety of silica fume concrete options are available to you, such as silica oxide micro fine 400, silica ultra fine500. Effect of micro silica on the strength of concrete with.
The combustion process creates silicon dioxide molecules, which condense to form particles. Making silica fume concrete in the laboratory pdf producing crack free concrete structures. Working with silica fume concrete concrete construction. It may be mixed to any consistency from plastic to flowable. Copies of material warranties should be obtained if available. This area contains information and resources of special interest to anyone involved with producing, or placing silica fume concrete. Fresh concrete containing silica fume is more cohesive and less. Benefits of using silica fume in concrete civil engineer. Silica fume is used in high performance concrete as a pozzolan to improve its properties. Silica fume and kim media kryton international inc. Published on march 28, 2016 march 28, 2016 39 likes comments. It can also be used with condensed silica fume concrete, concrete containing fly ash, and most other cementitous products. Target flowcrete with silica fume consists of accurately weighed portland cement, aggregates and chemical admixtures.
The compressive strengths of silica fume cement paste and mortar were evaluated at various watercementitious ratios. Published by the fhwa and ncbc, hpc bridge views is a bimonthly newsletter providing timely information on high performance concrete as it is used in transportation structures. Six fulldepth silica fume concrete bridge decks were constructed in minnesota between 1997 and 1999. Newly added to this download is a software program that uses acis 305 evaporation. Early age shrinkage and cracking of nevada concrete. 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. This increased durability and resilience can be attributed to decreased permeability and absorption. It may be added directly to concrete as an individual ingredient or in a blend of portland cement and silica fume.
Addition of silica fume to concrete has many advantages like high strength, durability and reduction in cement production. A pozzolan is a material that when in the presence of water has a chemical reaction and forms compounds that possess cementitious properties. Three specimens for each test were prepared to guarantee the. Unless authorized in writing by an officer of euclid, no other representations or statements made by euclid or its representatives, in writing or orally, shall alter this warranty. A higher rate of loss of heat from the outer surface of concrete causes cracking. Jan 26, 2017 silica fume concrete silica fume is an artificial pozzolona having high pozzolonic activity. Effect of micro silica on the strength of concrete with ordinary portland cement verma ajay 1, chandak rajeev 2 and yadav r. The individual particles are extremely small, approximately 1100th the size of an average cement particle. Fumed silica is being used in various fields such as pharmaceuticals, paints, adhesives and sealants, plastics, rubber and ink except for concrete.
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