Products For Concrete
Silica Fume INTRODUCTION Silica fume, also known as Microsilica is fine amorphous silica. Added to concrete at around 30kg/m3 it changes the rheology and reacts with the cement hydration products to dramatically improve concrete strengths, durability and impermeability, allowing concrete to be used in ways never before possible.
WHAT IS SILICA FUME? Silica fume is a filter powder generated from the reduction of high purity quartz – ferrosilicon metals or silicon metals. Silica fume consists primarily of very fine smooth spherical silicon oxide particles with an extremely high surface area. Silica fume’s chemical and physical typical composition is shown in Fig.1 in comparison with OPC cement and fly ash.
HOW SILICA FUME WORKS IN CONCRETE?
Fig. 1 Chemical and Physical Composition Unit
OPC
Flyash
SiO 2
%
17 - 25
40 - 55
Silica Fume 90 - 98
CaO
%
60 - 67
1-5
0.2 - 0.7
Al 2 O 3
%
2-8
20 - 30
0.4 - 0.9
Fe 2 O 3
%
0-6
5 - 10
1-2
Other
%
1-8
4 -15
2-3
S. G
Kg/m3
3150
2100
2200
Bulk density
Kg/m
3
900 - 1000
550 - 650
Surface Area
m2/kg
1400 200 500
200 - 600
20,000
Typical values for chemical and physical data for cementitious materials
Figure 2 – Silica Fume Reacts W ith The W eak Leachable CaOH 2 to Form Strong Dense CSH Free Lim e
Aggregate
O PC
12% Silica Fum e
Cement Silica Fume Fills The Pores
0
5
10
15
20
25
30
D ays
35
40
45
50
55
60
Figure 4 – Approximately 100,000 Silica Fume Silica Fume particles fill the space between cement grains. Figure 5 – Silica Fume Contributes Predominantly to Strength Between 3-28days.
Silica fume improves concrete through two mechanism:1. Pozzolanic effect: When water is added to OPC, hydration occurs forming two products, as shown below: CSH (Calcium OPC + H 2 O silicate hydrate) + Ca(OH) 2
superplasticizer to compensate for the higher water demand is universally recommended. Superplasticizers have a greater effect in silica fume concrete than in normal concretes because of the larger total surface area. It is possible now to dose high dosage of superplasticizers for very low water cement ratios concrete without bleeding and segregation problems encountered with normal OPC concrete. It enables
In cre ase in str en gt h
P a rtic le S h a p e a n d S ize
Figure 3 – Silica Fume Silica Fume is 100x finer than
cement and the particles are spherical. In the presence of silica fume, the silicon dioxide from the silica fume will react by weight of cement, approximately with the calcium hydroxide to produce 100,000 particles for each grain of more aggregate binding CSH as follows:- cement will fill the water spaces in fresh concrete (Fig 4). This eliminates bleed CSH Ca(OH) 2 + SiO2 + H 2 0 and the weak transition zone between The reaction reduces the amount of aggregate and paste found in normal calcium hydroxide in the concrete as concrete. This microfiller effect will shown in Fig. 2. The weaker calcium greatly reduced permeability and hydroxide does not contribute to improves the paste-to-aggregate bond of strength. When combine with carbon silica fume concrete compared to dioxide, it forms a soluble salt which will conventional concrete. leach through the concrete causing efflorescence, a familiar architectural The silica reacts rapidly (fig 5) providing problem. Concrete is also more high early age strengths and durability. vulnerable to sulphate attack, chemical The efficiency of silica fume is 3-5 times attack and adverse alkali-aggregate that of OPC and consequently vastly reactions when high amounts of calcium improved concrete performance can be obtained. hydroxide is present in concrete.
OPC
Silica Fume
Fly Ash/Slag
10hrs
7days
28 days
90 days
us to produce very flowable concrete without segregation and very high strength concrete. (70 to 120 MPa). Silica fume also lubricates the concrete and increases pumpability.
Since silica fume concrete exhibits significantly reduced bleeding, the potential for plastic shrinkage is increased. Thus it is necessary to protect the surface of freshly placed silica fume to prevent rapid water evaporation. Practices outlined in the Guide for Hot Weather Concreting (ACI 305) and for Concrete Floor and Slab Construction (ACI 302) should be followed to provide a good surface. Curing should begin immediately following the finishing operation and can include all types of FRESHCONCRETEPROPERTIES normal curing such as fogging, water 2. Microfiller effect : Silica Fume is an extremely fine material, Due to its very fine nature and thus spraying, plastic sheets and curing with an average diameters 100x finer than greater surface area, silica fume will membranes. cement (Fig 3). At a typical dosage of 8% increase the water demand. The use of a
buildings and improved construction schedule. It is also much more easier to pump silica fume concrete up the high rise buildings during construction. Because of the pozzolanic and microfiller effect of silica fume, its use in concrete can Shotcrete improve many of its properties opening up Silica fume is use in shotcrete whether a wide range of applications including:produced by wet or dry process to reduce Corrosion Resistance the rebound, to increase application The reduced permeability of silica fume thickness per pass, improve resistance to provides protection against intrusion of wash out in marine construction or wet chloride ions thereby increasing the time areas and to improve the properties of taken for the chloride ions to reach the hardened shotcrete. With fibres it can steel bar and initiate corrosion. In eliminate mesh and reduce cracking. addition, silica fume concrete has much higher electrical resistivity compared to Abrasion Resistance OPC concrete thus slowing down the Silica fume concrete has very high corrosion rate. The combined effect abrasion resistance. In floor and generally increased structures life by 5 – pavement construction it's use saves 10 times. Silica fume concrete is money and time and improves therefore suitable for structures exposed operational efficiencies for the facility to salt water, de-icing salts, ie. harbour operator. It also improves the hydraulic structures, ports, bridges, docks, on- abrasion-erosion resistance of concrete shores constructions situated in areas thus making it suitable for use in dam with chlorides in the ground water, soil spillways. and in the air.
SILICA FUME CONCRETE APPLICATIONS
Sulphate Resistance
•
SUGGESTED READING 1. 2.
3.
4.
5.
Chemical Resistance
Silica fume concrete is widely used in industrial structures exposed to an array of chemicals aggressive. In the alimentary industry the exposure comes from fat acids and other acids, detergents, etc. In 6. the chemical industry there is exposure from mineral acids, phosphates, nitrates, Heat Reduction petrochemicals, etc. Silica fume concrete By replacing cement with silica fume and is therefore invaluable in the industrial observing the efficiency factor of silica and agricultural sectors. 7. fume, a lower maximum temperature rise and temperature differential will take TECHNICAL SUPPORT place for concrete with the same strength. It performs better than slag and SCPL are able to provide technical fly-ash blends in thick sections. It is also support related to most aspects of the use 8. the most effective way of achieving low of concrete in construction. This support heat without sacrificing early age takes the form of: strength. • Meeting with the owner, architect, Silica Fume Waterproof Concrete engineer and/or contractor to Because of its low permeability, silica develop a cost effective and fume can be use as an integral technically appropriate silica fume waterproofer for below ground structures concrete option that invariably where some dampness is acceptable, eg offers advantages to all parties; “the carparks. win, win, win approach". • Presentation to interested parties on High Strength Concrete the mechanisms by which Silica Silica Fume in conjunction with Fume Concrete provides solutions superplasticizers is used to produce very to construction problems. high strength concrete (70 – 120 MPa). • Report preparation that details the High strength concretes provides large design methods and assumptions economic benefits to developers e.g. used for any analysis undertaken and reduced column and wall thickness in tall include published papers supporting Silica Fume concrete has a low penetrability and high chemical resistance that provides a higher degree of protection against sulphates than low C 3 A sulphate resisting cements or other cementitious binder systems.
the use of these design methods. Use of computer models to calculate dosages of special additives
American Concrete Institute "Guide for the Use of Silica Fume in Concrete”, ACI Detroit, 1996. Domone, P.L.J., Soutsos, M.N., "An Approach to the Proportioning of High Strength Concrete Mixes", Concrete International, 1994. FIP State of the Art Report, "Condensed Silica Fume in Concrete”, Thomas Telford. London, 1988. Holland, T., "Silica Fume Utilisation in Field Concrete”, International Workshop on the use of Fly Ash, Slag, Silica Fume and other Siliceous Materials in Concrete, Sydney, Australia, 1988. Holland, T., "Specification for Silica Fume for Use in Concrete”, Presented at the Fifth Canmet/ACI International Conference on Fly Ash, Silica Fume Slag and Natural Pozzolans in Concrete, Milwaukee, Wisconsin, 1995. Malhotra, V.M., Ramachandran, V.S., Feldman, R.F., Aitcin, P.C., "Condensed Silica Fume in Concrete", CRC Press Inc, Florida, 1987. Malier, Y., “High Performance Concrete from Material to Structure", E & FN Spoon, London, 1992. Zia.P., Leming, M.L., Ahmed, S.H., "High Performance Concrete. A State of the Art Report", Strategic Highways Research Council, Washington DC, 1991.
The information given is based on knowledge and performance of the material Every precaution is taken in the selection of the product and the responsibility is limited to the quality of supplies, with no guaranty of results in the field as SCPL has no control over site conditions or execution of works
Shakti Commodities Pvt. Ltd. Products For Engineered Concrete 79 Shyam Lal Road, 2nd Floor, Daryagunj New Delhi - 110002, Tel: 23245112-114, Fax: 91-11-23245113
Products For Concrete
Silica Fume – Shotcrete
For Building, Construction, Mining and Tunneling Fig 1a - President Hotel in Melbourne used silica fume spraycrete as the contractor found it the cheapest means of constructing curved architectural walls
CONCRETE BENEFITS WITH SILICA FUME
Fig 3 – Silica fume shotcrete provides resistance to corrosion. The very low chloride permeability is indicated here (ref Morgan 1992) Rapid Chloride Permeability 10000 6800
Formwork Elimination • •
shortens construction period reduced labour
1000 320
Low Rebound • • Fig 1b - Water tanks 20m diameter and 5m tall have been constructed in one day with silica fume shotcrete. An internal shutter about 3m long and full height is moved like a horizontal jump form.
reduced waste low clean up
High Build • •
no cold joints rapid construction
Waterproof •
no membrane required
Durable •
suitable for severe exposure
High Quality Finish •
INTRODUCTION
suitable for coating
WITH SYNTHETIC FIBRES
• •
low early age cracking high build
Shotcrete relies on three key components which ensure the ideal performance for WITH STEEL FIBRES commercial construction, mining and • eliminates mesh tunnelling applications. • low overspray Silica fume imparts the following • low preparation properties: high toughness and impact • High cohesion and adhesion (fig 2) • resistance makes Silica fume shotcrete a viable low cost construction method, particularly where formwork costs are Fig 2 – Silica fume shotcrete’s cohesion and adhesion reduces the amount of rebound, high,eg basements, curved walls, particularly with dry mix and overhead spraying. water tanks. In underground Rebound (%) construction Silica fume shotcrete 60 linings can be shot in one pass 50 without using toxic accelerators (fig 40 8). • High durability (fig 3) and strength 30 makes silica fume the ideal choice in severe exposure environments. 20 OPC Silica Shotcrete should incorporate fibre Fume 10 specifically selected for each application:• Synthetic fibres (fig 4) provide 0 Over Head Walls excellent control of early age cracking, (fig 5) enabling mesh to be excluded a particular consideration in high (fig 6). cement contents shotcrete which is • The high toughness of steel fibres highly restrained. imparts high impact resistance(fig 7). • Steel fibres impart high toughness
100
None
Undense
Fig 4 - The low early age cracking with Nycon synthetic fibres results from their high bond performance due to their hydrophilic nature 1,000
Number Of Hairline Cracks
800 600 400 200 Control
Nycon
Polyprop.
Fibrillated Polyprop.
0
Fig 5 - Toughness Using Scanfibre
Load (kg) 2500
2500
2500
2000
2000
1500
1500
1000
2000
500
1000
Double Anchorage Hooked End Fibre CHD80/60NB
0 0.00
0.50
1.00
1.50
2.00
2.50
3.00
500
0 0.00
Single Anchorage Hooked End Fibre CHO65/60 0.50
1.00
1.50
2.00
2.50
3.00
1500 1000
500 0 0.00
w/c=0.52; Slump=150mm Cement =400kg/m3 Fibre=20kg/m3
0.50
1.00
Tests by Bridgestone 17/6/99
1.50
Deflection (mm)
2.00
2.50
Fig 6 – Use of steel fiber can eliminate mesh and reduce overspray. Mesh Reinforced Steel Fibre Reinforced Shotcrete Shotcrete Rock
Plain Shotcrete Welded Wire Mesh Mesh Pinned To Rock
Rock Steel Fibre Reinforced Shotcrete
Cover To Mesh
Silica Fume Concrete – The Next Generation Construction Material
Fig 7 – Steel fibres imparts high impact resistance not obtainable with other fibre types. Synthetic fibres only give low impact resistance.
50kg/m3 Hooked steel fibre
60
No of Blows
Fig 9 – Silica fume Shotcrete, the rapid simple way of applying concrete
50 40 30
80kg/m3 Straight
Plain Concrete
20 10 0
Fig 8 – Silica fume shotcrete can be built up to 10x that of normal shotcrete
Meeting with the 2) Owner, Architect, Engineer and/or Contractor to develop a cost effective and technically 3) appropriate concrete option that invariably offers 4) advantages to all parties; “the win, win, win approach". • Presentation to interested parties on the mechanisms by which advanced materials in concrete provide solutions to construction problems. • Report preparation that details the 5) design methods and assumptions used for any analysis undertaken and includes published papers supporting the use of these design methods. 6) Use of computer models to calculate dosages of special materials. •
SPECIFICATION Where silica fume is to be used the general specification clauses outlined on the “Silica Fume” data sheet shall be included in the concrete specification. Additionally shotcrete can be specified by including the following clauses in the standard concrete specification:1. All shotcrete shall contain a minimum of 8% silica fume. 2. Steel fibre shotcrete shall have the following properties* • Re3 60% • 28Day f’c 40 MPa 3. All shotcrete shall be placed in one pass to the full thickness such that there are no cold joints. 4. All rebound shall be collected and removed from the job site.
TECHNICAL SUPPORT
7)
* Consult SCPL to give specific recommendations for your project.
We can provide shotcrete matched to design requirements for durability and toughness based on exposure conditions, or select suitable combinations of silica fume and Steel fibre to give the ideal impact 8) and abrasion resistance.
GENERAL
SUGGESTED READING
SCPL and its associates are able to provide technical support related to most aspects of the use of concrete in construction. This support takes the form of:-
1)
432. Morgan, D.R., "Advances in Shotcrete Technology for Support of Underground Openings in Canada", Engineering Foundation Conference, Shotcrete for Underground Support V, Uppsala, Sweden, 1990. Burge,. TA., 'Fiber Reinforced High Strength Shotcrete with Condensed Silica Fume", SP91-57. American Concrete Institute 1991. Wolsiefer, J., and Clear, K., 'Long Term Durability of Silica Fume Structural Concrete, Shotcrete, Grout, Slab Overlays and Patches", Fourth Canmet/ACI International Conference on Fly Ash, Silica Fume, Slag and Natural Pozzolans in Concrete, Istanbul, Turkey, 1992. Morgan, D.R., Neill, J., McAskill, N., and Duke, N., "Evaluation of Silica Fume Shotcrete', CANMET/CSCE International Workshop on Silica Fume in Concrete, Montreal, Quebec, 1987. "Structural Shotcrete Walls", International Patent Pending No. PCF/A492/0041 1. Morgan, D.R.,'Wet-Mix Silica Fume Shotcrete: "Effect of Silica Fume Form", Fourth CANMET/ACI International Conference on Fly Ash, Silica Fume, Slag and Natural Pozzolans in Concrete, Volume 2, lstanbu],Turkey, 1992. Vandewalle, M., 'Tunnelling the -World" N.V. Bekaert, Belgium 1996.
Morgan, D.R., 'Use of Supplementary Cementing Materials in Shotcrete", Proceedings International Workshop on the Use of Fly Ash, Slag, Silica Fume, and Other Siliceous Materials in Concrete, Sydney, CIA, 1988 pp 403-
The information given is based on knowledge and performance of the material Every precaution is taken in the selection of the product and the responsibility is limited to the quality of supplies, with no guaranty of results in the field as SCPL has no control over site conditions or execution of works
Shakti Commodities Pvt. Ltd. Products For Engineered Concrete 79 Shyam Lal Road, 2nd Floor, Daryagunj New Delhi - 110002, Tel: 23245112-114, Fax: 91-11-23245113
Silica Fume - High Strength Concrete SILICA FUME HIGH STRENGTH CONCRETE Silica fume high strength concrete is now readily available from many concrete plants. Strengths of 100MPa are available in some locations. Economics
The drive behind silica fume high strength concrete is economics. •
•
•
Columns. Figure 2 shows that the lowest column cost to carry a given load results by using silica fume high strength concrete and deleting expensive reinforcing steels. Shaft Walls. The great economic benefit is indirect. For example the value of extra floor space when 80MPa silica fume high strength concrete is used instead of 40 Mpa concrete could be as much as 50% of the core construction cost. General. Wherever concrete is in compression high strength concrete can be used to reduce material cost. Inevitably other cost savings are even greater. For example thinner tunnel segments leads too a great saving in excavation costs.
CONCRETE BENEFITS THINNER ELEMENTS
• • • •
•
Lower material cost Reduced self weight Reduced heat build up More space available More elegant design
• • • •
•
Lower cost Faster construction Simpler placing Lower labour cost Improved compaction
HIGH STIFFNESS/LOW CREEP
• •
•
Less column shortening Smaller beam deflections Reduced sway
C olu m n C ost
40 35
8% R ein forcem en t
30 4% R ein forcem en t
25 20
1% R ein forcem en t
15 10
REDUCED REINFORCEMENT
20
40 60 C o n c re te S tre n g th (M P a )
80
Figure 3 - Balance Between Early and Later Strength. Silica fume high strength concrete provides high early age strength as well as high long term strength. Strength (MPa)
140
Slag 40% 30% 20% 10%
100
0%
60 Total cementitious Silica Fume Water
20 20
40 60 Log Time (Days)
= 458kg/m 3 = 37kg/m 3 = 175kg/m 3
80
100
LOW SHRINKAGE SHORTER CURING PERIOD HIGH EARLY STRENGTH LOW HEAT
Physical Properties
Strength requirements are balanced between early age for stripping and long term structural performance. Silica fume is a key component of high strength concrete as it contributes to strength at early and later ages (fig 3).
Figure 2 - Column Cost. - high strength concrete can lead to direct material cost savings. However, the major return can be future income from increased lettable area due to thinner elements.
Figure 4 - E-modulus of Silica Fume high strength concrete. This does not rise as rapidly as strength and become the critical factor. 70 E-Modulus
Use AS 3
600
;AC
I 31
8;
3; C I 36 illo ;A ha h; S as q u Carr Ahm ad & ; NS34 73
50
30
Figure 1- Pumping 100MPa high flow silica fume concrete. 10
20
60 100 140 Compressive Strength
180
When designing with silica fume high Figure 5 - Creep of Silica Fume Concrete. The creep of silica fume high strength concrete is significantly lower than normal concrete. This reduces deflections and prestress losses. 40
Creep strain per unit stress (microstrain/MPa) Marine Cement
30
OPC
20 OPC+10%CSF
10 0
Water/binder = 0.35 max
0
20
40 Age (days)
60
Silica Fume Concrete – The Next Generation Construction Material
80
Figure 6 - Shrinkage of silica fume high strength concrete. Provided silica fume high strength concrete is cured for 24hrs shrinkage is likely to be similar or less than normal concrete. (ref I.Burnett CSR) 800
Microstrain
Maximum Shrinkage ____ustrain.
60 MPa
600
80 MPa
200 0
0
10
20
30
40 50 60 Days Drying Time
70
80
90
Figure 7 -Teamwork for Silica Fume high strength concrete. To successfully design, manufacture, transport, place and finish silica fume high strength concrete all parties must work together (ref Paver, 1993) Testing
Owner
QA
Design
R&D Supplier
Aggregate Cement
Supplier
days
Creep, E-modules and tensile strength shall be calculated using design formula developed for use with silica fume at the designated strength.. Before silica fume high strength concrete shall be placed these calculations shall be approved by the Engineer.
1.
Helland, S., “Slipforming of Concrete with Low Water Content”, Vol 18, No 12, December 1984, pp 19-21.
2.
Sellevold, E.J., “The Function of Condensed Silica Fume in High strength concrete”, Utilisation of High strength concrete, Proceedings of the Symposium in Stavanger, Norway, June 1987, Trondheim, Tapir Publishers, 1987, pp 39-49.
3.
Paver, I., “Construction Aspects” High Strength, High Performance Concrete Seminar, C&CA. Sydney, 1993.
4.
Baweja, D., et al “High Performance Australian Concretes for Marine Applications” American Concrete Institute, Singapore 1994.
5.
Luther, M. and Hansen, W., “Comparison of Creep and Shrinkage of High Strength Silica Fume Concretes with Fly Ash Concrete of Similar Strengths”, Proceedings, CANMET/ACI Third International Conference on the Use of Fly Ash, Silica Fyme, Slab and Natural Pozzolans in Concrete, Trondheim, SP-114, Vol 1 ACI, Detroit, 1989.
6.
Sellevold, E.J., “The Function of Condensed Silica Fume in High strength concrete”, Proceedings Symposium on Utilisation of High strength concrete, Strevenger, Norway, 1987, pp 39-49.
7.
Hansen, W., “Creep and Drying Shrinkage of Very High strength concrete”, Department of Civil Engineering, The University of Michigan, Ann Arbor, Michigan, 1987, p23.
Engineer
High strength concrete
Building
Concrete
Use of computer models to calculate the dosage of special additives.
SUGGESTEDREADING 50
TECHNICAL SUPPORT
Brief
Supplier Admixture
at
Test reports showing that the proposed mix will meet these requirements shall be provided before placing any silica fume high strength concrete.
90 MPa
400
•
Min. Characteristic Strength: 7 day ____Mpa 28 day ____Mpa 90 day ____MPa
Contractor
Producer
strength concrete it is necessary to use appropriate physical properties some of these are provided in the book “Silica Fume Concrete” available on request. Key parameters are: E Modulus – critical for elastic shortening in silica fume high strength concrete, (fig 4) Creep – greatly reduced in silica fume high strength concrete (fig 5)
High strength concrete is far more difficult to achieve at the job site than in the laboratory. Factors like pumpability (fig 1) and setting time for slip forming makes it is essential that the project team (fig 7) work together for success. Our group can assist in establishing a functional project team. GENERAL
SCPL are able to provide technical support related to most aspects of the use of concrete in construction. This support takes the form of: •
Shrinkage – reduced in silica fume high strength concrete (fig 6).
SPECIFICATION Where silica fume concrete is to be used the general specification clauses outlined on the “Silica Fume ” brochure shall be included in the concrete specification. Additionally, silica fume high strength concrete shall be specified by including the following clauses in the standard concrete specification: Concrete shall be supplied with the following physical properties:
•
•
Meeting with the Owner, Architect, Engineer and/or Contractor to develop a cost effective and technically appropriate silica fume concrete option that invariably offers advantages to all parties, “the win, win, win approach”. Presentation to interested parties on the mechanisms by which silica fume concrete provides solutions to construction problems. Report preparation that details the design methods and assumptions used for any analysis undertaken and includes published papers supporting the use these design methods.
Figure 8 - Melbourne Central. Silica fume was used to provide high strength pumpable concrete.
The information given is based on knowledge and performance of the material Every precaution is taken in the selection of the product and the responsibility is limited to the quality of supplies, with no guaranty of results in the field as SCPL has no control over site conditions or execution of works
Shakti Commodities Pvt. Ltd. Products For Engineered Concrete 79 Shyam Lal Road, 2nd Floor, Daryagunj New Delhi - 110002, Tel: 23245112-114, Fax: 91-11-23245113
Products For Concrete
SILICA FUME - WATERPROOF CONCRETE For Integral Waterproofing of Basements, Tanks, Pools, Tunnels & Other Underground Structures SILICA FUME WATERPROOF CONCRETE Any waterproofing system must meet all serviceability criteria (see fig 2) i.e.: •
Permeability – The concrete, joints and cracks must all have an acceptable water penetration rate.
•
Durability – The concrete must be durable in respect to chemical attack and corrosion resistance.
Structural – The concrete’s physical properties (strength, creep, modulus and shrinkage) must be acceptable. Silica fume WPC satisfies all these criteria in regards to the concrete matrix and provides the designer with the first rational design approach (a supporting spreadsheet is available) to this problematical area. The design of integral waterproofing is based on Valenta and Darcy equations for permeability, modified using standard factors of safety i.e.: Depth of penetration d = (2f 1 .f 2 .f 3 .k.t.h)0.5/v Flow Rate (m3/sec) Q = f 1 .f 2 .f 3 .k.Ah/d where f 3 = load factor f 2 = materials factor f 1 = test factor k = permeability (m/s) h = pressure head (m) t = time(secs) v = voids fraction (0.1) A = area of flow Using these equations, the required permeability can be calculated for any design situation. A suitable mix design can then be determined from permeability graphs like those shown in figs 4 & 5. Figure 6 shows that silica fume WPC reduces permeability by reducing the pore size. Other properties achieved include increased chemical and corrosion •
BENEFITS OF SILICA FUME WATERPROOF CONCRETE No Membranes or Drainage Required
• • •
Major cost saving in materials Reduction in programme time Less subcontract labour
Enhanced Placing Characteristics
• • • •
Better pumpability Lower heat of hydration No segregation Shorter curing period
Improved Durability
• • •
Very high sulphate resistance Corrosion resistant Resistant to mild acids
Structural Improvements
• High strength • Low creep • Low shrinkage • High modulus resistance and lower heat of hydration. Silica fume WPC should not be confused with damproof concrete achieved using water repellents in above ground concrete.
SILICA FUME WATERPROOF CONCRETE SPECIFICATION Where silica fume concrete is to
be used, the general specification clauses outlined on the silica fume concrete data sheet should be
included in the concrete specification. Additionally, Silica fume Waterproof Concrete can be specified by including the following clauses in the standard concrete specification:
Figure 1 – Concrete contains pores (magnified image shown here) of a wide range of sizes. Water flows readily through the larger ( >600Ao) Figure 2- Diagram of basement showing durability serviceability criteria. Silica Fume WPC assists in all areas.
Crack
Water Table Acid
Heat
Chlorides Sulphates
Leakage Joints
Figure 3 - Diagram of basement showing the permeability equations. Factors of safety are added to these and then they are used as the design base.
Water Table d=depth s=sorptivity t=time v=voids ratio k=permeability h=pressure head A=area q=flow rate
Silica Fume Concrete – The Next Generation Construction Material
Permeability 0.5 d= (2kth) v q= kAh d
Figure 4 – The permeability of OPC concrete is the basis from which the permeability of Silica Fume WPC is calculated (Concrete Society, 1985) 1000
2.
The contractor shall supply a 10year warranty that the structure shall not leak provided that the crack size is less than 0.2mm at the surface
3.
The contractor shall submit the proposed concrete mix design for approval together with permeability calculations, verifying that the proposed mix requirements set out in clause 1.
Permeability m/sec x10-13
300 200 100 30 20 10 3 2 1
0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75
Figure 5 – The reduction in permeability due to si;ica fume depends on the silica fume dosage and w/c ratio 100
Permeability Reduction Ratio Permeability Reduction Ratio CSF w/b ratio 0.34 0.60 1 0% 1 20 5% 6 100 10% 31
80 60 40
A spreadsheet is available which, on input of the design criteria, gives an indication of the most economic mix that will achieve the performance required. Support documentation is also available. Advice on crack width and joint design is available.
CSF 10% 9% 8% 7% 6%
20
5%
0 0,25
0,3
0,35 0,4 0,45 0,5 Water/binder ratio
0,55
0,6
Figure 6 – Reduction in pore size distribution using CSF
Mercury Penetration
0.5
Pore volume over 600 angstroms determine penetrability
0.4
0.2
Microsilica
OPC
0.1
400
4000
Pore Size (Angstroms)
40000
The structure has the following design • parameters:m Normal pressure head Minimum concrete thickness m f 3 = load factor = . • f 2 = materials factor = . f 1 = test factor = . Minimum time before any flow yrs Maximum water inflow rate lt/m2 • Minimum time before any flow yrs
1.“Permeability Testing of Site Concrete – A preview of Methods and Experience”. Concrete Society Technical Report London, 1985. 2. Sellevold, E.J., Bager, D.H., Jensen, E.K., and Knudsen, T., “Silica Fume Cement Pastes: Hydration and Pore Structure”, Report BMI 82.610, Trondheim, Norwegian Institute of Technology, 1982, pp19-50. 3. Markestaad, A., “An Investigation of Concrete in Regard to Permeability Problems and Failures Influencing the Results of Permeability Tests”, NTH report, 1969.
4. Mehta, P.K., and Gjorv, O.E., “Properties of Portland Cement Concrete Containing Fly Ash and Condensed Silica Fume”, Cement and Concrete Research, GENERAL Vol 12, No 5, September 1982, pp 587SCPL are able to provide technical 595. support related to most aspects of the use of concrete in 5. Manmohan, D., and Mehta, P.K., construction. This support takes “Influence of Pozzolanic, Slag and Chemical Admixtires on Pore Size the form of:
Distribution and Permeability of Hardened Cement Pastes”, Cement, Concrete and Aggregates, 1981, 3, No 1, Summer, 63-67.
Meeting with the Owner, Architect, Engineer and/or Contractor to develop a cost effective and technically appropriate Silica Fume Concrete option that invariably offers advantages to all parties; “the win, win, win approach".
6. Feldman, R.F., and Huang Cheng-yi, “Properties of Portland Cement 0 Silica Fume Pastes in Porosity and Surface Properties”, Cement and Concrete Research, 1985, 12, 765-774.
Presentation to interested parties on the mechanisms by which silica fume Concrete provides solutions to construction problems.
7. Hustad, T., and Loland, K.E., “Report 4: Permeability”, FCB/SINTEF, Norwegian Institute of Technology, Trondheim, 1981, Report STF65 A81031.
Report preparation that detail the design methods and assumptions used for any analysis undertaken and includes published papers supporting the use of these design methods.
8. Maage, M., “Effect of Microsilica on the Durability of Concrete Structures”, FCB/SINTEF, Norwegian Institute of Technology, Trondheim, 1984, Report STG65 A84019.
•
0.3
0 40
1.
Pores have no effect on penetrability
TECHNICAL SUPPORT
SUGGESTED READING
Use of computer models to calculate dosages of special additives.
The information given is based on knowledge and performance of the material Every precaution is taken in the selection of the product and the responsibility is limited to the quality of supplies, with no guaranty of results in the field as SCPL has no control over site conditions or execution of works
Shakti Commodities Pvt. Ltd. Products For Engineered Concrete 79 Shyam Lal Road, 2nd Floor, Daryagunj New Delhi - 110002, Tel: 23245112-114, Fax: 91-11-23245113
Products For Concrete
Silica Fume - Sulphate Resistant Concrete Ideal Alternative To Low C3A Cement
Tests in moderate sulphate environments (fig 2 & 3) show that OPC outperforms the SRPC mix. Various leading authors have ratified this alarming fact over the last 8 years.
SRPCGIVES LOWER STRENGTH THAN OPC AND HENCE HIGHER HEAT OF HYDRATION Due to its chemical nature SRPC gives a lower 28 day strength than OPC. This leads to a high cement content, higher cost and higher heat of hydration than an OPC concrete of equivalent strength.
Sodium Sulphate Concentration
Fig 2 – At moderate sodium sulphate concentrations OPC concrete performs better than low C3A sulphate resisting cement. Silica fume SRC performs far better than either of them (ref Fidjestol, 1990) 10 8
4 2
5% Silica Fume
6
10% Silica Fume
Visual Damage Scale 1. No change 2. Whole specimen colour change 3. one or two spalls 5. Delaminated area 7. Several large delaminations 9. Whole specimen delaminated
Fig 3 – At moderate magnesium sulphate concentrations low C3A sulphate resisting cement performs better than OPC. Silica fume SRC performs far better than either of them (ref Fidjestol, 1990) 7 Visual Damage Scale 1. No damage 5. Yellow all over
6 5 4 3 2 1
10% Silica Fume
C3A binds chlorides to form Friedal salts. The chemically bound chlorides cannot penetrate so the total amount of chloride available for penetration is reduced. Hence in low C3A cement concretes chloride ions diffuse to the steel rapidly exacerbating the corrosion problem.
Accelerated Tests
5% Silica Fume
Another major problem with low C3A cements is that they increase the risk of corrosion.
Moderate Exposure
OPC Concrete
SRPCHAS LOW CORROSION RESISTANCE
Acid Attack
OPC Concrete
•
Ettringite Formation
20% FA Concrete
•
Acid Attack
SRPC (low alumina content <5% C3A)
20% FA Concrete
Accelerated tests that are normally undertaken on concrete show SRPC provides high sulphate resistance. However, the effects of penetrability are not apparent and the form of attack is different to that at moderate concentrations in this rapid test.
•
Ettringite Formation
SRPC Concrete
Of particular concern is the fact that low C3A cement based concrete may provide poor protection in moderate sulphate environments. The reasons for this low protection are that SRPC:• has a poor permeability due to the interconnected interfacial layers. Hence, the contaminating fluid penetrates the concrete quickly • provides low resistance to the acidic form of attack that predominates when sulphates are not consumed in forming ettringite (fig 1)
•
OPC (high alumina content >5% C3A)
SRPC Concrete
SRPC(TYPE VCEMENT) HAS LOW SULPHATE RESISTANCE IN MODERATE EXPOSURES
•
Sulphate resistant at low and high sulphate concentrations Resistant to chloride ion penetration and corrosion propagation (NB chlorides are often present with sulphate) Silica fume represents a low proportion of the cementitious system making it • easy to store • low cost in relation to SRPC in some locations High strength leading to • low cement content low heat • low cost High early age strength for early formwork and propping removal Can be used for waterproofing
Extent Of Corrosion
Table 1 - Comparison SRPC and OPC+CSF Silica fume SRC SRPC (Low C3A Cement) Poor performance at low High performance in all sulphate concentrations normal sulphate conditions High rebar corrosion Prone to rebar corrosion protection Low chloride diffusion High chloride diffusion Very high resistivity Low Resistivity High 28 day strength Low 28 day strength Low cement content High cement content Economic design High total cost Low heat High heat of hydration Readily available Special production often required Moderate cost High unit cost Small storage volume with Large storage volume long shelf life
•
Fig 1 – Different mechanisms attack the concrete at different sulphate concentrations. Accelerated testing of low C3A cement concrete may tell us nothing about performance at moderate sulphate concentrations (ref Mehta, 1982).
Visual Damage 1200 Days
Research(2,6) over the last 10-15 years has shown several technical problems with the use of low C3A cements (SRPC or type V cement). These problems are depicted in Table 1
BENEFITS OF SILICA FUME SULPHATE RESISTANCE CONCRETE
Visual Damage 1200 Days
INTRODUCTION
0
SILICA FUME SRCOUT PERFORMS ALL OTHER CEMENT SYSTEMS Silica Fume SRC out performs other cementitious systems significantly in terms of:-
Silica Fume Concrete – The Next Generation Construction Material
• • •
The excellent performance of silica fume SRC results from:•
•
•
•
Lime consumption reduces the amount of gypsum available for formation of ettringite.
Report preparation that detail the design methods and assumptions used for any analysis undertaken and includes published papers supporting the use of these design methods.
Low permeability reduces the penetration of attacking sulphate. Of particular significance is the elimination of the transition zone which has been shown to be the main ingress path for sulphates.
•
The formation of analogs of mono sulphate hydrate that are resistant to sulphates -
1. Mehta, P.K., and Gjorv, O.E., "Properties of Portland Cement Concrete Containing Fly Ash and Condensed Silica Fume", Cement and Concrete Research, Vol 12, No 5, pp 587-595 1982.
Class
SO4
1 2 3 4a 4b 5 5b
<300 300-1200 1200-2500 2500-5000 2500-5000 >5000 >5000
Mg
<1000 <1000 >1000 <3000 >3000
CSF/Type1 Kg/m3 Refer Code 7.5% 7.5% 10% 10% Corrocem
Table 1:Design guide for SFSRC
W/c 0.50 0.50 0.45 0.45 0.45 0.40
GENERAL SCPL are able to provide technical support related to most aspects of the use of concrete in construction. This support takes the form of:
•
•
Dilution of the lime and C3A reducing the amount of ettringite that can form.
Silica fume SRC can be used to give protection against other sulphates and chemicals. Your silica fume Concrete supplier can obtain advice on this for you and provide suitable specifications.
•
on the mechanisms by which silica fume Concrete provides solutions to construction problems.
Sulphate resistance in moderate environments Sulphate resistance in aggressive environments (figures 4 & 5) Corrosion Resistance Low heat of hydration
Meeting with the Owner, Architect, Engineer and/or Contractor to develop a cost effective and technically appropriate Silica Fume Concrete option that invariably offers advantages to all parties; “the win, win, win approach". Presentation to interested parties
Fig 4 – In the ASTM C1012 expansion test Silica fume SRC out performs low C3A cement. OPC performs very poorly in these high (5%) sulphate concentration tests (ref Hooton, 1993). Expansion %
0.12
0.1
2. Mather, K., "Current Research in Sulfate Resistance at the Waterways Experiment Station", Proceedings, George Verbeck Symposium on Sulfate Resistance of Concrete, SP-77, ACI, Detroit, 1982, pp 63-74. 3. Hooton, R.D., "Influence of Silica Fume Replacement of Cement on Physical Properties and Resistance to Sulfate Attack, Freezing and Thawing, and Alkali Silica Reactivity", ACI Materials Journal, Vol 90, No 2,1993, pp 143-161.
Worst
ate lph Su nce h Hig esista SRPC R
0.06 0.04
OPC+CSF
0.02 0
Use of computer models to calculate dosages of special additives.
SUGGESTED READING
OPC
0.08
M od e R rat es e is Su ta lp nc h e ate
•
Best 0
50
100
Age (Days)
150
200
250
300
350
Fig 5 – In strength loss tests Silica fume SRC out performs low C3A sulphate resisting cements. OPC performs very poorly in these high (5%) sulphate concentration tests (ref Rasheeduzzafar, 1994) 12
Strength (psi ‘000)
10
Type I+CSF Best
8
Type V
6
Type I
4 2 0
Worst 0
100
Age (Days)
200
300
Fig 6 – Silica fume SRC was used for Blackrock sewage works. With the fascility only 500 metres from Bass Strait, all concrete used was subject to high levels of chlorides as well as sulphates
4. Buck, A., "Use of Pozzolan or Slag in Concrete to Control Alkali-Silica Reaction and Sulfate Attack", Technical Report SL-88-29, USA Army Engineer Waterways Experiment Station, Vicksburg, 1988. 5. Popovic, K., Ukraincik,V, and Djurekovic, A., "Improvement of Mortar and Concrete Durability by the Use of Condensed Silica Fume", Durability of Building Materials, Vol 2, No2,1984, pp 171186.
Resistance and Chloride Penetration Characteristics of High Strength Concrete", High Performance Concrete, Proceedings ACI International Conference, Singapore 1994. 8. "Reinforcement Corrosion-Resisting Characteristics of Silica Fume Blended Concrete", ACI Materials Journal, Vol 89, No4, ACI 1992.
6. Fidjestol, P., "Concrete For Low Sulfate Concentrations", Concrete Institute of Australia, Concrete for the Nineties, Leura, NSW, 1990. 7. Al-Khaja, W.A., Rasheeduzzafar, W.A., AlSayed, M.H., and Al-Khoder, A.A., "Sulfate
The information given is based on knowledge and performance of the material Every precaution is taken in the selection of the product and the responsibility is limited to the quality of supplies, with no guaranty of results in the field as SCPL has no control over site conditions or execution of works
Shakti Commodities Pvt. Ltd. Products For Engineered Concrete 79 Shyam Lal Road, 2nd Floor, Daryagunj New Delhi - 110002, Tel: 23245112-114, Fax: 91-11-23245113
Products For Concrete
Silica Fume – Floors & Pavements
For Building, Construction, Mining & Tunnelling SILICAFUMEFLOORAND PAVEMENTCONCRETE
Silica Fume FPC can include a range of specialist materials for industrial floors, housing slabs, pavements and agricultural hard stands: •
Steel fibres to replace and improve on conventional reinforcing
•
•
•
from a brittle material to a tougher more ductile one. The level of improvement is determined by the fibre type, geometry and dosage. Synthetic fibres give the highest level of impact resistance to concrete and are therefore of value:•
In heavy workshops
Synthetic fibres to provide early age crack control (up to 1 day)
•
In addition to Silica Fume where abrasion and impact are present
Silica Fume to give high abrasion resistance, strength and chemical resistance
•
Where tracked vehicles are used
•
Where rocks, rubble rubbish are loaded
•
Where vibration is a problem
•
Where steel wheeled trolleys, rubbish dumpsters etc are use
Pigments for a brighter finish or an environmentally sensitive appearance
ABRASIONRESISTANCE
The abrasion resistance of concrete is closely linked to the strength of the cement paste. This can be improved by using a lower water:cement ratio, reducing bleed (reduces the water:cement ratio at the surface), and by adding Silica Fume. Bleed can have a major affect on abrasion resistance. Silica Fume virtually eliminates bleed, synthetic fibres reduce it significantly. IMPACTRESISTANCE
Impact Resistance is a measure of the ability of the concrete to absorb the energy imparted to it by a sharp, short duration load or blow. Fibres enable concrete to absorb the energy by turning it
equipment
or
PLASTICCRACKING
When the concrete is fresh and still plastic i.e. in the first few hours after placing, various factors can cause early age tensile strains which exceed the tensile capacity of the young concrete. Low dosages of synthetic fibres will increase the resistance of concrete to this type of cracking. Performance is related to the fibre characteristics but, in general, synthetic fibres are superior to steel fibres in controlling plastic cracking because the comparatively low steel fibre count per kilo of fibres added results in a much lower fibre/paste bond area that cannot effectively mobilise the
load carrying capacity of steel fibres at early age. Early age strains that are of significance are plastic shrinkage, early thermal and plastic settlement. Drying shrinkage cracking, the majority of which occurs from 1 day to 90 days can not be controlled by synthetic fibre because the concrete strength and modules are far higher than the fibres. Long term strains are best controlled by steel fibre. TOUGHNESS
Toughness is the principal criteria for designing industrial floor slabs. The design is based on the fact that the concrete will behave in a ductile fashion with the steel fibres spreading the load into the surrounding concrete, and hence over a larger spread of ground. Toughness is a standard measure for steel fibre concrete and is the subject of ASTM, JIS and many European standards. The Concrete Society (UK) has maintained the JIS defined Re3 designation of toughness as being suitable for floor slab design in its Technical Report 34. The performance of fibres varies enormously depending on the steel properties, anchorage design and aspect ratio. Dramix is the leading fibre in terms of toughness performance. TENSILESTRENGTH
Fibres do not increase tensile strength significantly. Conventionally 30Mpa concrete is taken to have a flexural
Silica Fume Concrete – The Next Generation Construction Material
strength of 4Mpa. In some steel fibre slab design methods a flexural strength of 6Mpa as the principal criteria used in the elastic design. This can simply be achieved by increasing the compressive strength of the concrete to 40Mpa by lowering the w/c ratio or by using Silica Fume. In other words the steel fibre is redundant. This shows the method is invalid and a toughness basis should be used. SHEARSTRENGTH
Steel fibres provide shear capacity because many of the fibres are under a steep angle and act like stirrups in direct tension. Hence, if the slab cracks, the steel fibres will provide a locking action that prevents differential vertical movement. Steel fibres provide excellent shear capacity and hence 3 30kg/m of 60/1.00mm fibre were specified. The Silica Fume FPC with Steel fibres was pumped to the job site with ease.
expertise and specialist design. More generally steel fibre floor slabs enable joint spacing to be increased. It is recommended that the slabs are allowed to move and thickened sections should be isolated from large 5. pours. Silica Fume Concrete requires close attention to ensure plastic cracking, due to the low bleed does not occur. This low bleed 6. can be an advantage, in that finishing can be undertaken immediately with the one pass finish method. SUGGESTED READING
Hester, W.T., “Specifying High Performance Concrete Industrial Floors”, construction Specifier, 1986. “The Structural Design of Heavy Duty Pavements for Ports and Other Industries”, British Ports Federation.
1.
Holland, T.C., “AbrasionErosion Update”, Concrete Structures, Repair and Rehabilitation, Vol C-38-1, August 1983, pp 1-3,7.
7.
“High Performance Concretes, A State of the Art Report”, Strategic Highway Research Program, National Research Council, SHRPC/FR-91-103, 1991.
2.
Carlsson, M., Hope, R., 8. Pedersen, J., “Use of Condensed Silica Fume (CSF) in Concrete”, ACI SP-91, CANMET/ACI Second International Conference on the Use of Fly Ash, Silica Fume, Slag and Natural Pozzolans in Concrete, April 1986, Madrid, Vol 11, Detroit, American Concrete Institute, 1986, pp10131030.
Baluguru. P., and Shah S.P., “Fibre Reinforced Composites” Me Graw Hill 1992.
3.
Gjorv, O.E., Baerland, T., and Heinrich, R.R., “Abrasion Resistance of High Strength Concrete Pavements. Concrete International Vol 12 No 1, January 1990.
4.
Gjorv, O.E., Baerland, T., Tonning, H.R., “High Strength Concrete for
CONSTRUCTABILITY
Use of steel fibres and silica fume can make construction considerably easier and cheaper. Where steel fibres are used to replace mesh the cost and time saving associated with not placing mesh are considerable. Another benefit is that without mesh its often possible to truck the concrete up to the work face, no pumping or wheelbarrowing involved. A big decision, what joint spacing? In Europe jointless floors (40 metre plus joint centres) are not uncommon. This requires a high degree of
Highway Pavements and Bridge Decks”, Division of Building Materials, University of Trondheim, Report No 87.202, Trondheim, Norway, 1987.
The information given is based on knowledge and performance of the material Every precaution is taken in the selection of the product and the responsibility is limited to the quality of supplies, with no guaranty of results in the field as SCPL has no control over site conditions or execution of works
Shakti Commodities Pvt. Ltd. Products For Engineered Concrete 79 Shyam Lal Road, 2nd Floor, Daryagunj New Delhi - 110002, Tel: 23245112-114, Fax: 91-11-23245113
Products For Concrete
Silica Fume - Low Heat Concrete SILICAFUMELOWHEAT CONCRETE
CONCRETE BENEFITS
By substituting up to 4 parts of cement with 1 part of silica fume the total heat generating capacity of concrete is reduced. Weight for weight silica fume generates approximately the same amount of heat as cement, so the temperature rise and differential are reduced at all element thicknesses.
LOW TEMPERATURE RISE AND TEMPERATURE DIFFERENTIAL
By slowing the rate of hydration, thereby giving time for heat to escape, slag and fly ash reduce temperature rise and differential. Bamforth’s curves (fig 1) show that the effectiveness of this diminishes as the element thickness increases. In thick sections the heat is locked in.
•
•
Silica fume is the only effective supplementary cementitious material in thick sections.
HIGH EARLY AGE STRENGTH
•
No delay to prop and formwork removal Early finishing
HIGH DURABILITY
•
•
Resistant to sulphates, chlorides and acids Shorter curing period
Using Bamforth’s curves we can establish that there is a point where the WATERPROOF silica fume reduces heat more • The silica fume low heat concrete will effectively than slag (fig 2). act as an integral waterproofer as well To more precisely quantify the relative SIMPLE PLACING effectiveness of different cementitious systems tests were undertaken at • Less risk of segregation Taywood Engineering’s laboratories in • Improved pumpability Perth, Australia. The adiabatic temperature rise of four concretes mixes (Table 1) designed to have the same 28 day compressive strength (fig 3), was measured. These were input into a computer simulation of temperature rise and temperature differential in an 800mm thick section. OPC Assumptions CSF Efficiency Slagment Eff. Mix Design OPC CSF Slag Cementitious CSF (%) Slag (%) w/c Est 28d f'c
CSF
3.3 399 399 0.4 50
310 27 337 8 0.4 50
Slag
0.9 147 272 419 65 0.4 50
LOW SHRINKAGE AND CREEP
Figure 1 - As the concrete thickness increases, heat is locked in and the use of fly ash and slag to delay heat of hydration and temperature rise become ineffective. Temperature Rise (oC/100kg cement) 0%
12
30% 50%
8
70%
4 0
1.0
2.0 3.0 Slab Thickness (m)
4.0
Figure 2 - Bamforth's curves are used to show that in thicker slabs slag concrete will be out performed by silica fume concrete. 60 Max Temp Rise (C) OPC 50 OPC/CSF 40 LH
LH/CSF
30
OPC/CSF outperforms LH
LH/CSF outperforms all other mixes
20 10 0 0
C 2 3 Slab Thickness (m)
1
4
5
Figure 3 - The strength development curves show that silica fume low heat concrete has higher early age strengths than slag cements. 70
Strength (Mpa)
50
Figures 5 and 6 shows that insulation would be used to minimise temperature differentials as peak temperature is not an issue. In the 800mm section silica fume low heat concrete is as Slag & effective as the slag concrete CSF but has far higher early age strengths. In thicker sections 3.2 the silica fume low heat 0.9 concrete performs better than 124 the slag. 231 374 5 0.4 50
Table 1 - Mix designs for OPC, silica fume and slag concrete's designed to have the same strength.
Silica fume low heat concrete is designed to meet the specific maximum temperature and temperature differential requirements of a project.
GP LH GP+8% LH+5%
30 10 5
10
15 Days
20
25
30
Figure 4 - Computer analysis shows that at 800mm thick slag and silica fume concretes give similar temperature differentials. 70 60 50
Maximum temperature (oC) 58 48
50
45
GP LH GP+8% LH+5%
50 42
44
40
38
30 20 10 0
Insulated form
Forms removed
Silica Fume Concrete – The Next Generation Construction Material
Products For Concrete Figure 5 - Computer analysis based on adiabatic temperature rise shows that temperature differentials for silica fume and slag are similar at 800mm. 30
Max. Temperature differential(oC)
20 15
27
GP
25
LH
22
GP+8%
18
24 20
LH+5% 12
12
11
Proc Utilisation of High Strength Concrete, Stavenger, 1987.
LOW HEAT CONCRETE
Detailed advice can be provided on the potential temperature rise and differential for Silica fume Low Heat Concrete as placed in various curing situations. The effect on thermal cracking can be provided.
4.
Lessard, S., Aitcin, P.C., and Regourd, M., “Development of a Low Heat of Hydration Blended Cement”, Proceedings CANMET/ACI First International Conference on the Use of Fly Ash, Silica fume, Slag and Other Mineral By-Products in Concrete, Montebello, 1983, pp 747-764.
5.
Maage, M., “Strength and Heat Development in Concrete: Influence of fly Ash and Condensed Silica fume”, Proceedings CANMET/ACI First International Conference on the Use of Fly Ash, Silica fume, Slag and Other Mineral By-Products in Concrete, Montebello, 1983, pp 923-940.
6.
Meland, I., “Influence of Condensed Silica fume and Fly Ash on the Heat of Evolution in Cement Pastes”, Proceedings CANMET/ACI First International Conference on the Use of Fly Ash, Silica fume, Slag and Other Mineral By-Products in Concrete, Montebello, 1983, pp 665-676.
GENERAL
10 5 0
Insulated form
Forms removed
SILICA FUME LOW HEAT CONCRETE
SCPL are able to provide technical support related to most aspects of the use of concrete in construction. This support takes the form of:-
•
SPECIFICATION
Where Silica fume Silica fume is to be permitted the general specification clauses outlined on the “Silica Fume ” brochure should be included in the concrete specification. Additionally, Silica fume low heat concrete can be specified by including the following clauses in the standard concrete specification: Silica fume Low Heat Concrete shall be supplied with the following physical properties:
•
•
Characteristic Strength:
Min compressive strength 3 day 7 day 28 day
•
____MPa; ____MPa; ____MPa;
Meeting with the Owner, Architect, Engineer and/or Contractor to develop a cost effective and technically appropriate Silica fume Concrete option that invariably offers advantages to all parties; “the win, win, win approach” Presentation to interested parties on the mechanisms by which Silica fume Concrete provides solutions to construction problems. Report preparation that details the design methods and assumptions used for any analysis undertaken and includes published papers supporting the use of these design methods. Use of computer models to calculate dosages of special additives.
Temperature Requirements
SUGGESTEDREADING
Max. Temp. Rise:
1.
Bamforth, P., “Insitu measurement of the effect of partial Portland cement replacement using either fly ash or ground granulated blast furnace slag on the performance of mass concrete”. Proc. Inst. Civ. Engs. Parts pp777-800. London 1980.
2.
Fidjestol, P., “Use of Condensed Silica fume Concrete in Scandinavia: Case Histories,” Presented at the CANMET International Workshop on Condensed Silica fume in Concrete, Montreal, Canada, 1987.
3.
Helland, S., “Temperature and strength Development in Concrete with W/C Ratio Less than 0.40”,
Aggregate Type Gravel Granite Limestone Lightweight
70°C; Max. Temp. Differential: 20°C 28°C 39°C 55°C
A report showing that the proposed mix and placing method with meet these requirements shall be submitted to the Engineer for approval before placing any silica fume low heat concrete.
TECHNICALSUPPORT
Figure 6 - 6m deep pour at Suntec City Centre where 100kg /m3 of cement was replaced by 25kg/m3 of silica fume to reduce temperature rise by 10oC and provide the same strength.
The information given is based on knowledge and performance of the material Every precaution is taken in the selection of the product and the responsibility is limited to the quality of supplies, with no guaranty of results in the field as SCPL has no control over site conditions or execution of works
Shakti Commodities Pvt. Ltd. Products For Engineered Concrete 79 Shyam Lal Road, 2nd Floor, Daryagunj New Delhi - 110002, Tel: 23245112-114, Fax: 91-11-23245113
SCPL are able to provide technical support related to most aspects of the use of concrete in construction.
Authorized Distributor for Nepal JYOTI SHREE NEPAL PVT. LTD. Room No. 306, Radha Bhawan PO Box: 2829, Tripureshwor, Kathmandu, Nepal Tel: 4244010, 4263718, 4243109 Fax: +977-1-4220494, 42636694 Email: info@jyotishreenepal.com