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The Reef Ball Foundation, working closely with concrete experts, has developed a typical mix design suitable to create artificial reef modules in complex molds with a minimal pH and to enhance the settlement and growth of typical marine species such as hard corals. Specific biological goals, such as oyster settlement, may require specialized designs. If you can not find local materials to match these specifications because of admixture or cement type availability, there are several acceptable substitutions, contact us for information. In general, this starting mix design has the highest amount of Portland Cement to help insure that you don't break your Reef Balls when handling them. However, Reef Ball usually don't need this much Portland cement when handled carefully, and there are additional biological benefits of using less cement because this can further reduce concrete pH. If you are reaching your goal of 95% or better of your modules not being broken you might consider reducing your cement proportions. Remember that best concrete practices are required for good pH neutralization; primarily the use of fresh cement, complete mixing, and good curing conditions (high humidity for at least 30 days)....without good practices all the microsilica in the world won't prevent a high pH.
Contact us if you have any questions about your mix design, to obtain approval for deviations or if you need a custom design for a specific project.
PART I - GENERAL
1.01 Section Includes
A. Concrete proportioning and products to be used to secure concrete, which when hardened will produce a required strength, permeability, and resistance to weathering in a reef environment.
1.04 References
A. ACI-211.191-Standard Practice for Selecting Proportions for Normal, Heavyweight, and Mass Concrete.
B. ASTM C 260- Standard Specifications for Air-Entraining Admixtures for Concrete.
C. ASTM-C Type III- Standard Specifications for Fiber Reinforced Concrete or Shotcrete.
D. ACI - 305R -91- Hot Weather Concreting.
E. ACI - 306R -88- Cold Weather Concreting.
F. ACI - 308- Standard Practice for Curing Concrete.
G. ASTM C 618-Fly Ash For Use As A Mineral Admixture in Portland Cement Concrete.
H. ASTM C 494-92- Standard Specifications for Chemical Admixtures for Concrete.
I. ASTM C -91- Electrical Indication of Concrete's Ability to Resist Chloride Ion Penetration.
J. ASTM C 33- Concrete Aggregates.
K. ASTM C 94- Ready Mix Concrete.
L. ASTM C 150-Portland Cement.
M. ACI 304- Recommended Practice For Measuring, Mixing, Transporting and Placing concrete.
N. ASTM C 39 (Standard Specifications For Compressive Testing)
O. ASTM C--93 (Standard Specifications for Silica Fume Concrete)
PART II PRODUCTS
2.01 Portland Cement: Shall be Type II and conform to ASTM C-150
2.02 Fly Ash: Shall meet requirements of ASTM C-618, Type F. And must be proven to be non-toxic as defined by the Army Corps of Engineers General Artificial Reef Permits. Fly Ash is not permitted in the State of Georgia and in most Atlantic States. (In October, , The Atlantic States Marine Fisheries Commission adopted a resolution that opposes the use of fly ash in artificial reefs other than for experimental applications until the Army Corps of Engineers develop and adopt guidelines and standards for use.)
2.03 Water: Shall be potable and free from deleterious substances and shall not contain more that parts per million of chlorides or sulfates and shall not contain more than 5 parts per million of lead, copper or zinc salts and shall not contain more than 10 parts per million of phosphates.
2.04 Fine Aggregate: Shall be in compliance with ASTM C-33.
2.05 Coarse Aggregate: Shall be in compliance with ASTM C-33 #8 (pea gravel). (Up to 1 inch aggregate can be substituted with permission from the mold user.) Limestone aggregate is preferred if the finished modules are to be used in tropical waters.
2.06 Concrete Admixtures: Shall be in compliance with ASTM C-494.
2.07 Required Additives: The following additives shall be used in all concrete mix designs when producing the Reef Ball Development Group's product line:
A. High Range Water Reducer: Shall be ADVA Flow 120 or 140.
B. Silica Fume: Shall be Force 10,000 Densified in Concrete Ready Bags as manf. by W.R. Grace. (ASTM C--93) or any of the permitted equivalent silica fume Brands as defined in the training manual Appendix K
C. Air-Entrainer: ONLY IF ADVA is not used: Shall be Darex II as manf. by W.R. Grace (ASTM C-260)
2.08 Optional Additives: The following additives may be used in concrete mix designs when producing Reef Ball Development's product line.
A. Fibers. Shall be either Microfibers as manf. by W.R. Grace, or Fibermesh Fibers (1 1/2 inches or longer) as manf. by Fibermesh. Either November 1, ators: Any Non- Calcium Chloride or Daracell as manf. by W.R. Grace may be used. (ASTM C-494 Type C or E)
C. Retarders: Shall be in compliance with ASTM-C-494-Type D as in Daratard 17 manf. by W.R. Grace
2.09 Prohibited Admixtures: All other admixtures are prohibited. Other admixtures can be submitted for approval by the Reef Ball Foundation Inc. Services Division by sending enough sample to produce five yards of concrete, the current MSDS, and chemical composition (which will be kept confidential by RBDG Ltd.) A testing fee of $2,500 must accompany the sample. Temporary approval will be granted or denied within 10 days based on chemical composition, but final approval may take up to 3 months since samples must be introduced in a controlled aquarium environment to assess impacts on marine and freshwater species.
PART III Concrete Proportioning:
A. General: The intent of the following proportions is to secure concrete of homogeneous structure which will have required strength and resistance to weathering.
B. Proportions:
One Cubic Yard
One Cubic Meter
Cement:
600 lbs. (Min.)
356 kg
Aggregate:
lbs.
kg
Sand:
lbs
688 kg
Water:
240 1bs. (Max.)
142 kg
Force 10K:
50 lbs
30 kg
Grace Microfibers
.25 bag
.3 bag
*Adva Flow 120 or
Adva Flow 140
3.5-5 ounces per 100 lbs cement
or
6-10 ounces per 100 lbs cement
1
*NOTE: Adjust Adva dosage as needed to obtain workable, placeable mix (170-250mm / 7-10 inch slump), and to achieve .40 w/c ratio.
Fibers: 0-3# (Max.) as needed to reduce micro cracking 1# (Min.) required if Silica Fume exceeds 50#
Accelerator: As needed to achieve de-molding no sooner than: 3-4 hours for heavy duty molds (All Polyform side balls) 6-7 hours for standard molds (Molds with any tether balls)
NOTE: Silica Fume or Force 10K shall be dosed at a 10# minimum in Bay Balls and Pallet Balls while Ultra & Reef Balls shall require a minimum of 25#. All molds must use at least 50# for floating deployments. All mold sizes must use at least 50# for use in tropical waters unless special curing procedures are followed.* This product is being specified not only for strength, but also to reduce pH to spur coral growth, to reduce calcium hydroxide, and to increase sulfate resistance. It is a non-toxic pozzalan.
* Special curing procedures for tropical waters without 50# of Silica Fume per yard should include storage in a fresh water or high humidity environment for a minimum of 60 days or less with higher temperatures, or until the surface pH of the modules is below 9.5 pH when placed in seawater.
NOTE: End of day concrete may be used, but follow these additional requirements.
-Do not use concrete that has a temperature of over 100 degrees Fahrenheit -The original mix must have been at least 3,500 PSI -50# of added microsilica or more is required unless microsilica at that dose was already in the starting mix -Add additional Portland if needed to achieve a .4 w/c ratio. Take into account water added on site -Advise mold user to allow extra time for curing to achieve minimum de-molding strength. -Mold or module user must be notified that EOD waste was used.
NOTE: Fly Ash, when permitted, may be used as a substitution for cement up to a maximum replacement of 15% and as an additional substitute for microsilica at 30% to 40% of cementitious material. (Call RBDG for details.)
Part IV Concrete Testing Requirements:
A. Compressive strengths shall be tested in accordance with ASTM C 39. Compressive strengths shall reach a minimum of the following table at the time of use of at least:
Super/Ultra/Reef Ball
Pallet Ball
Bay Ball and all smaller sizes
Floating Deployment
8,500+
7,000+
6,000+
Barge Deployment
7,000+
5,500+
4,000+
To remove from mold
750+
750+
750+
To lift from base
1,500+
1,200+
1,000+
B. Permeability of concrete shall be tested in accordance with ASTM C -91. Coulomb requirement shall be coulombs or less at 90 days. End of day waste shall be coulombs or less at 90 days.
THIS SPECIFICATION SHEET IS ONLY A SAMPLE. CONTACT RBDG FOR CUSTOM SPECIFICATIONS.
1) All deployments made by authorized contractors must have at least 90% of modules upright and intact or they must supply free deployed replacement to purchaser. This is REGARDLESS of what the customer says is acceptable.
2) All new construction after Jan. 1, must use ADVA Flow superplastisizer rather than WRD-19, Reduce the amount of air entrainment by 35-50% so that entrainment remains at 6% +/- 2%. (This will not impact your costs).
2a) All new construction after July must have Attachment Adapter Plug system installed and at least 50% of the recommended number of attachment adapters for the particular sized Reef Ball must be usable.
3) All Reef Balls must be constructed with a "wavy" bottom formed by adding sand in the mold before inserting center bladder.
4) The rinsing of the outside layer of concrete is not optional to expose the surface texture due to the pH rise on the surface of the poorly set concrete. (If rinsing is impractical, use a non-oil based biodegradable mold-releasing compound instead of sugar water. Increase air entrainment to 8% and do not tap the concrete into the mold heavily to create as much "honeycombing" as you can.)
5) The following are MINIMUM guidelines for microsilica use, primarily for pH reduction. Again, these are REGARDLESS of what the customer says is acceptable.
Hard Corralled Waters (Florida border & south on East Coast, Hernando County and south on Gulf.) (Anywhere near the Flower Gardens of Texas, anywhere near Grey's Reef in SC)
If you want to learn more, please visit our website 90% Undensified Silica Fume.
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Deployed less than 45 days from casting = 50 lbs/yard
Deployed > 45 days < 90 days from casting = 45 lbs/yard
Deployed > 91 days < 120 days from casting = 40 lbs/yard
Deployed > 121 days < 150 days from casting = 35 lbs/yard
Deployed > 151 days < 180 days from casting = 30 lbs/yard
Deployed > 181 days < 210 days from casting = 25 lbs/yard
Deployed > 211 days < 240 days from casting = 20 lbs/yard
Deployed > 240 from casting = 15 lbs/yard
Temperate / Cool Waters (North of above & all of West Coast)
Deployed less than 29 days from casting = 50 lbs/yard
Deployed > 30 days < 90 days from casting = 30 lbs/yard
Deployed > 91 days < 120 days from casting = 25 lbs/yard
Deployed > 121 days < 150 days from casting = 20 lbs/yard
Deployed > 151 days < 180 days from casting = 15 lbs/yard
Deployed > 181 days < 210 days from casting = 10 lbs/yard
Deployed > 211 days < 240 days from casting = 5 lbs/yard
Deployed > 240 from casting = not required
6) End of day waste still requires full 50 lbs/yard of Mircosilica regardless of location/time
7) All other proprietary standards, including an approved mix design must be upheld.
FIbermess Product Guide Specifications
SI Concrete Systems
Industry Drive
Chattanooga, Tennessee
Toll Free (800) 621-
(423) 892-
Fax (423) 892-
Website www.siconcretesystems.com
Specifier Notes: This product guide specification is written according to the Construction Specifications Institute (CSI) 3-Part Format as described in The Project Resource Manual&#;CSI Manual of Practice. The section must be carefully reviewed and edited by the Architect or Engineer to meet the requirements of the project and local building code. Coordinate this section with other specification sections and the Drawings. Delete all &#;Specifier Notes&#; when editing this section.
Section numbers are from MasterFormat Edition, with numbers from MasterFormat Edition in parentheses. Delete version not required.
SECTION (03 24 00)
SYNTHETIC FIBER REINFORCEMENT
Specifier Notes: This section covers SI Concrete Systems Fibermesh® 150 polypropylene fibers for use as concrete secondary reinforcement. Consult SI Concrete Systems for assistance in editing this section for the specific application.
PART 1 GENERAL
1.1 SECTION INCLUDES
A. Polypropylene fibers used as concrete secondary reinforcement.
1.2 RELATED SECTIONS
Specifier Notes: Edit the following list of related sections as required for the project. List other sections with work directly related to this section.
A. Section (32 13 00) - Rigid Paving.
B. Section (03 21 00) - Reinforcing Steel.
C. Section (03 30 00) - Cast-in-Place Concrete.
D. Section (03 37 13) - Shotcrete.
E. Section (03 50 00) - Cementitious Decks and Toppings.
1.3 REFERENCES
Specifier Notes: List standards referenced in this section, complete with designations and titles. This article does not require compliance with standards, but is merely a listing of those used.
A. ASTM C 94 - Standard Specification for Ready-Mixed Concrete.
B. ASTM C - Standard Specification for Fiber-Reinforced Concrete and Shotcrete.
C. Southwest Certification Services (SWCS), Omega Point Laboratories No. -1.
D. UL Report File No. R-11.
1.4 SUBMITTALS
A. Comply with Section (01 33 00) - Submittal Procedures.
B. Product Data: Submit manufacturer&#;s product data, including application rate and mixing instructions.
Specifier Notes: Delete samples if not required.
C. Samples: Submit manufacturer&#;s sample of synthetic fiber reinforcement.
D. Manufacturer&#;s Certification:
1. Submit manufacturer&#;s certification that synthetic fiber reinforcement complies with specified requirements.
2. Submit evidence of manufacturer&#;s ISO : certification.
3. Submit evidence of satisfactory performance history of synthetic fiber reinforcement.
1.5 QUALITY ASSURANCE
A. Manufacturer&#;s Qualifications:
1. Synthetic fiber reinforcement manufactured in ISO : certified facility.
2. Minimum 10-year satisfactory performance history of specified synthetic fiber reinforcement.
1.6 DELIVERY, STORAGE, AND HANDLING
A. Delivery: Deliver synthetic fiber reinforcement in manufacturer&#;s original, unopened, undamaged containers and packaging, with labels clearly identifying product name, unique identification number, code approvals, directions for use, manufacturer, and weight of fibers.
B. Storage:
1. Store synthetic fiber reinforcement in clean, dry area indoors in accordance with manufacturer&#;s instructions.
2. Keep packaging sealed until ready for use.
C. Handling: Protect synthetic fiber reinforcement during handling to prevent contamination.
PART 2 PRODUCTS
2.1 MANUFACTURER
A. SI Concrete Systems, Industry Drive, Chattanooga, Tennessee . Toll Free (800) 621-. (423) 892-. Fax (423) 892-. Website www.siconcretesystems.com. .
2.2 SYNTHETIC FIBER REINFORCEMENT
A. Synthetic Fiber Reinforcement: Fibermesh 150.
1. Material: 100 percent virgin homopolymer polypropylene multifilament fibers, containing no reprocessed olefin materials.
2. Conformance: ASTM C , Type III.
3. Fire Classifications:
a. UL Report File No. R-11.
b. Southwest Certification Services (SWCS), Omega Point Laboratories No. -1.
Specifier Notes: Specify graded or single-cut lengths.
4. Fiber Length: [Graded] [Single-cut lengths].
5. Alkali Resistance: Alkali proof.
6. Absorption: Nil.
7. Specific Gravity: 0.91.
8. Melt Point: 324 degrees F (162 degrees C).
PART 3 EXECUTION
3.1 MIXING
A. Add synthetic fiber reinforcement to concrete mixture in accordance with manufacturer&#;s instructions.
B. Add synthetic fiber reinforcement into concrete mixer before, during, or after batching other concrete materials.
Specifier Notes: Lower application rates may be acceptable depending upon local building codes. Consult SI Concrete Systems for more information.
C. Application Rate: Add synthetic fiber reinforcement at standard application rate of 1.5 pounds per cubic yard (0.90 kg/m3) of concrete.
D. Mix synthetic fiber reinforcement in concrete mixer in accordance with mixing time and speed of ASTM C 94 to ensure uniform distribution and random orientation of fibers throughout concrete.
Force 10,000 Specifications (Microsilica)
Concrete Products
Technical Guide Specification
Microsilica Concrete
SECTION
PART 1 - GENERAL
1.01 SUMMARY
A. This section specifies microsilica (silica fume) admixture for the reduction of concrete permeability to protect against intrusion by chlorides and other aggressive chemicals, and for the production of high-strength concrete.
B. Related Sections: Other specification sections which directly relate to the work of this Section include, but are not limited to, the following:
1. Section - Cast-In-Place Concrete.
2. Section - Post-Tensioned Concrete.
3. Section - Precast Concrete.
1.02 SUBMITTALS
A. Product Data: Submit manufacturer&#;s product data, installation instructions, use limitations and recommendations for each material.
B. Test and Performance Data: Submit independent test data substantiating the product&#;s ability to reduce concrete permeability by chlorides and other aggressive chemicals.
1.03 QUALITY ASSURANCE
A. Manufacturer: Concrete admixture shall be manufactured by a firm with a minimum of 5 years experience in the production of similar products. Manufacturers proposed for use but not named in these specifications shall submit evidence of ability to meet all requirements specified, and include a list of projects of similar design and complexity completed within the past five years.
B. Materials: For each type of material required for the work of this Section, provide primary materials which are the products of one manufacturer.
C. Pre-Construction Conference: A pre-construction conference shall be held two weeks prior to commencement of field operations to install the specified product in order to establish procedures to maintain optimum working conditions and to coordinate this work with related and adjacent work. Agenda for meeting shall include concrete and admixture handling, placing, finishing, and curing.
D. Manufacturer&#;s Representative: A representative of the manufacturer shall be present for project start-up during initial concrete placement. Engineer may waive requirement for manufacturer&#;s representative if Contractor provides sufficient evidence that producer and finisher have adequate experience with admixtures required.
E. Trial Mix: Provide a minimum 4 cubic yard (3 m3) trial mix containing proposed concrete design mix placed at the job site in location acceptable to the Engineer. Engineer may waive requirement for trial mix if Contractor provides sufficient evidence that producer and finisher have adequate experience with low water cement ratio mixes.
1.04 PROJECT CONDITIONS
A. Perform work only when existing and forecasted weather conditions are within the limits established by the manufacturer of the materials and products used.
PART 2 - PRODUCTS
2.01 MANUFACTURER
A. Provide Force 10,000® microsilica concrete admixtures by Grace Construction Products meeting specified requirements. For customer service in North America:
Call toll free: 877-4AD-MIX1 (877-423-)
Fax toll free: 877-4AD-MIX2 (877-423-)
2.02 MATERIALS
A. Microsilica Admixture: Provide Force 10,000 concrete admixture by Grace Construction Products complying with ASTM C .
2.03 CONCRETE MIXES
A. Application Rate:
NTS This section may be used for concrete permeability requirements or high-strength concrete. Application rate (dosage rate) of microsilica may vary depending on individual project requirements. Application rates may be stated in dry pounds per cubic yard, percent of weight of cement, or as required to meet a performance criteria. Typical application rates for low permeability concrete varies from 30 to 60 lbs/cy. Specifier should use only one of the three sections which follow for A. Application Rate.
NTS Force 10,000 Sample Specification For Permeability Requirements
This sample specification may be used by the design engineer when specifying Force 10,000 microsilica for the reduction of concrete permeability to protect against intrusion by chlorides or other aggressive chemicals. Force 10,000 is a microsilica-based admixture manufactured by Grace Construction Products of W. R. Grace & Co.-Conn.
The high silicon dioxide content of microsilica combines with the excess calcium hydroxide in the concrete to form more calcium silicate hydrate &#;glue.&#; This chemical reaction plus its fine particle size allows Force 10,000 to fill in the voids between the cement grains and aggregate to deliver less permeable concrete. When chlorides migrate through the concrete and attack the steel reinforcing, corrosion occurs. By reducing the permeability of the concrete, chlorides take much longer to reach the steel which extends the service life of the structure considerably. Chlorides are typically present from deicing salts or from a marine environment. Structure applications of Force 10,000 include parking garages, bridge decks and overlays, reinforced pavements, and all structures in a marine environment. Structural concrete design criteria shall follow ACI 318, 357 and 201 guidelines. Parameters used in this sample specification, such as water/cementitious ratio and concrete cover over reinforcing steel, are taken from these guidelines and are conservative values.
There are two ways to specify microsilica concrete for permeability requirements: by prescription or by performance. The prescription method mandates the number of pounds of microsilica per cubic yard to be used while the performance method uses ASTM C test method to measure &#;coulombs.&#; Please use one method (prescription or performance) but not both. If the &#;performance method&#; is the preferred choice, use ASTM C for mix design purposes only, not as a mix acceptance or rejection criteria during the construction phase. Since the chloride&#;s loading rate and final concrete quality are unknown factors, W. R. Grace cannot guarantee the longevity of the protection offered by Force 10,000. Quality concrete as recommended by ACI and the addition of Force 10,000 will slow the ingress of chlorides into the concrete. Neither quality concrete nor Force 10,000 will stop corrosion forever, but both will retard the onset of corrosion.
Prescription Method
1. Provide microsilica admixture Force 10,000 as manufactured by Grace Construction Products.
2. Microsilica shall be added at a rate of (50) pounds dry weight of microsilica per cubic yard [(30) kg/m3] of concrete.
3. Compressive strength shall be a minimum of (5,000) psi [35 MPa] at 28 days as measured using (4&#; x 8&#;) (100 mm x 200 mm) cylinder specimens.
4. A maximum water-to-cementitious ratio of 0.40 is required.
5. Microsilica may be counted as cementitious material in calculations.
6. Add microsilica as a liquid slurry or in dry densified form in 25 lb (11.4 kg) Concrete Ready BagsTM packaging.
7. Blended cements with interground microsilica will not be allowed.
Performance Method
1. Provide microsilica admixture Force 10,000 as manufactured by Grace Construction Products.
2. Microsilica shall have a minimum of (5,000) psi [35 MPa] at 28 days as measured using (4&#; x 8&#;) (100 mm x 200 mm) cylinders.
3. Permeability of microsilica concrete shall be tested by ASTM C . Results of tests shall be expressed in electrical units of coulombs. Coulomb tests shall be made on two (4&#; x 8&#;) (100 mm x 200 mm) representative samples, moist cured for 56 days. Test cylinders shall be made according to ASTM C 31. Coulomb requirement shall be (_____) coulombs or less at 56 days. ASTM C testing shall be used as an indicator of concrete permeability at mix design submittal only.
4. A maximum water-to-cementitious ratio of 0.40 is required.
5. Microsilica may be counted as cementitious material in calculations.
6. Add microsilica as a liquid slurry or in dry densified form in 25 lb (11.4 kg) Concrete Ready Bags packaging.
7. Blended cements with interground microsilica will not be allowed.
NTS: Force 10,000 Sample Specification For High-Strength Concrete Requirements
This sample specification may be used by the design engineer when specifying Force 10,000 microsilica for the production of high-strength concrete. The design engineer should fill in the compressive strength required. Force 10,000 is a microsilica-based admixture manufactured by Grace Construction Products of W. R. Grace & Co.-Conn. The high silicon dioxide content of microsilica combines with the excess calcium hydroxide in the concrete to form more calcium silicate hydrate &#;glue.&#; This produces a stronger, tighter bonding paste structure. Additionally, the extreme fineness of the microsilica enables it a less permeable paste. These two factors contribute to providing higher strength, more durable concrete.
Structural applications for high strength Force 10,000 concrete are broad, but include usage in structural columns, beams and girders. Structural concrete design criteria shall follow ACI 318, 357 and 201 guidelines. Parameters used in this sample specification, such as water-to-cementitious ratio are taken from these guidelines and are conservative values. This sample specification is based on the performance method, whereby the compressive strength of the concrete is mandated by the design engineer.
High-Strength Concrete Requirements
1. Provide microsilica admixture Force 10,000 as manufactured by Grace Construction Products.
2. Microsilica high-strength concrete shall have a minimum of (____) psi [(___) MPa] at 28 days.
3. Test cylinders shall be 4&#; x 8&#; (100 mm x 200 mm).
4. A maximum water-to-cementitious ratio of 0.40 is required.
5. Microsilica may be counted as cementitious material in calculations.
6. Add microsilica as a liquid slurry or in dry densified form in 25 lb. (11.4 kg) Concrete Ready Bags packaging.
7. Blended cements with interground microsilica will not be allowed.
B. Concrete Cover Over Reinforcement: Minimum concrete cover over reinforcement shall be (____) inches [(____) mm].
NTS: Follow ACI 318 recommendations for concrete cover over reinforcement. For deicing salt and marine environments, ACI 318-89, section R7.7.5, requires 2 inches (50 mm) for walls and slabs and 2-1/2 inches (64 mm) for other members. For marine environments, ACI 357 recommends 2-1/2 inches (64 mm).
C. Air Entrainment: For freeze-thaw durability comply with ACI 318 freezing and thawing exposure requirements, as determined by ASTM C 173 or ASTM C 281.
D. Water-to-Cementitious Ratio: Provide 0.40 maximum. Microsilica, fly ash, blast furnace slag and cement are considered cementitious materials. The water content of Force 10,000 slurry shall be included as mix design water.
E. Recommended Cementitious Content for Workability:
Maximum Aggregate Minimum Cementitious
3/8&#; (10 mm) 700 pounds/cu.yd. (415 kg/m3)
1/2&#; (13 mm) 680 pounds/cu.yd. (400 kg/m3)
3/4&#; (20 mm) 650 pounds/cu.yd. (385 kg/m3)
1&#; (25 mm) 630 pounds/cu.yd. (375 kg/m3)
F. Compressive Strength: Minimum 28 day compressive strength for microsilica concrete shall be (5,000) psi [(35) MPa] unless stated otherwise in Section 2.03 A. Application Rate.
G. Concrete Slump for Flatwork: 5 to 8 inches (125 to 200 mm). Concrete slump may be 2 inches (50 mm) over normal concrete slumps as microsilica concrete can be sticky and has a surface that is harder to close than normal concrete.
H. Concrete Admixtures: High-range water reducers are mandatory to control slump, mixing, cementitious ratio and proper distribution of the microsilica, and shall be plant added. Additional water reducers may be added at the job site when required.
I. Additional Concrete Admixtures: Additional concrete admixtures conforming to ASTM C 494 or equivalent CSA 266 standards may be used as required including the following:
1. Type A: Water-reducing admixture, WRDA® series or Daracem®-55 by Grace Construction Products.
2. Type D: Water-reducing and retarding admixture, Daratard®-17 by Grace Construction Products.
3. Type F or G: Water-reducing, high-range admixture, WRDA-19, Daracem-100 by Grace Construction Products. This type of admixture must be included in all Force 10,000 concrete.
4. Type C: Accelerating admixture, PolarSet® by Grace Construction Products.
5. Grace MicroFibers® for flatwork, at 1 pound per cubic yard (600 grams/m3) addition rate.
6. DCI® or DCI-S Corrosion Inhibitor by Grace Construction Products may also be used if required at rate recommended by manufacturer.
J. Special Mixing Requirements for Densified Microsilica: Densified microsilica requires enhanced mixing to ensure full dispersion. The following mix requirements shall be adhered to:
1. For all types of mixing equipment, mix times shall be increased by 40% over the minimum mix time required to achieve mix uniformity as defined by ASTM C 94.
2. For truck-mixed and central mixed concrete, maximum allowable batch size shall be 80% of the maximum as called out by ASTM C 94.
PART 3 - EXECUTION
3.01 EXAMINATION
A. Examine conditions of substrates and other conditions under which work is to be performed and notify Owner, in writing, of circumstances detrimental to the proper completion of the work. Do not proceed until unsatisfactory conditions are corrected.
3.02 CONCRETE PLACEMENT, FINISHING AND CURING
A. Concrete Finishing and Curing: Microsilica concrete typically exhibits little or no bleeding. To reduce plastic or drying shrinkage cracks, comply with ACI 302 &#;Guide for Concrete Floor and Slab Construction&#;, ACI 308 &#;Standard Practice for Curing Concrete&#;, ACI 306 &#;Standard Practice for Cold Weather Concreting&#;, and ACI 305 &#;Hot Weather Concreting.&#;
1. Underfinish microsilica concrete by limiting finishing operation to screeding, bull-float, and broom finish. Curing shall be initiated within one hour of concrete placement.
2. The use of wind breaks, sun shades, and fog misting are recommended to minimize the rate of evaporation at the concrete surface.
3. Light fog misting above the concrete to keep the environment above the concrete surface at high humidity is recommended during the placing and finish operations.
4. Fog misting is required when the rate of evaporation at the concrete surface exceeds 0.1 pound per square foot per hour as determined by ACI 308 Section 1.2.1. Fogging shall continue after the finishing operation until prewetted burlap or other approved curing material is placed over the concrete. When fog misting is not available or possible, an evaporation retarder shall be applied before and after bull-floating and during final finish to protect the concrete.
5. Wet curing is the preferred method for curing. Use prewetted burlap to cover all flatwork and keep wet for a minimum of seven days or until the time necessary to attain 70 percent of the specified compressive strength, as recommended by ACI 308 Section 3.1.3.
3.03 PROTECTION
A. Protect completed work from damage and construction operations throughout finishing and curing operations.
As detailed in the previous section, the protocol with colloidal silica and a 50 °C curing yielded the highest content of M-S-H and the lowest content of other species. In this section, the samples analyzed originate from this protocol exclusively. Two types of mixing were tested, mechanical and manual. Three M/S ratios were studied: 0.78, 1 and 1.3. The pastes considered for Section 4.1 and Section 4.2 were MS_0-78_CS_T50_M, MS_1_CS_T50_E and MS_1-3_CS_T50_M.
The morphology of M-S-H pastes was observed by SEM on fractured samples ( ), proving to be similar to the morphology reported by Tonelli et al. [ 46 ]. M-S-H did not show crystalline facies but rather aspects of gel with globular chains. M-S-H showed high porosity at high magnification ( c), as we will discuss in Section 4.3 .
The two analyses allowed to describe the pastes as composed only of M-S-H. The evolution of the structure with M/S appeared in the XRD and TGA. Talc-like characteristics were observed at low M/S, while serpentine-like reflections were associated with high M/S. Moreover, we detected an increase in the Mg&#;OH content of M-S-H as M/S increased.
The structure of M-S-H has been compared to that of many phyllosilicates (sepiolite, talc, etc.) and characterized as a sheet structure evolving with the M/S [ 32 , 33 , 35 , 38 , 43 ]. The silicate sheets would be linked by layers of octahedral-coordinated Mg 2+ ions [ 32 ], with water present both as adsorbed water and in structure as H 2 O and hydroxyl groups [ 43 ]. As the X-ray diffractograms ( ) illustrate, the interlayer distance decreases while M/S in M-S-H increases [ 43 ], as is the case for C-S-H when the calcium to silicon (C/S) ratio increases [ 69 ]. According to the TGA results ( ), this reduction of the interlayer distance would be associated with the formation of Mg&#;OH in M-S-H, with internal silanol groups being reduced. The evolution mechanism of the M-S-H structure with the variation of M/S would then be similar to that of the C-S-H with the variation of C/S. A possible parallel could be inferred between the Ca&#;OH that forms between the chains of Ca&#;Si and the Mg&#;OH that would form between the layers of Mg&#;Si as C/S or M/S increase.
The second water loss region between 280 °C and 750 °C differed with the M/S ratio ( ). For M/S = 0.78 and M/S = 1, the second hump was located in the same place, while for M/S = 1.3 the second hump was shifted to the right. The offset of the hump (400&#;500 °C) resulting from the increase in M/S from 0.78&#;1 to 1.3 also appeared on the TGA on M-S-H powders from Bernard et al. and Nied et al. [ 32 , 43 ]. The height of the last water loss region between 750 °C and 840 °C also evolved with the M/S. The amount of bound water increased along with the magnesium content. As the weight loss around 400 °C has been associated to surface Si&#;OH and the weight loss around 500 °C to Mg&#;OH in M-S-H [ 43 ], the offset of the hump would indicate the formation of more Mg&#;OH groups with the increase in M/S. For M/S = 1.3, the broader weight loss around 500 °C covered the weight loss around 400 °C of M/S = 0.78 and M/S = 1, indicating that the amount of surface Si&#;OH groups remains stable. Conversely, the decrease in height of the weight loss peak around 800 °C as M/S increases would indicate a decrease in the internal Si&#;OH content of M-S-H. Thus, the internal structure of M-S-H would evolve with M/S.
The position shared by the authors quoted is the following: (i) the weight losses between 200 °C and 800 °C for M-S-H systems are linked to the dehydroxylation of a hydroxyl group in M-S-H, and (ii) the potential offsets of the losses are linked to the evolution of the structure of M-S-H. With regard to the type of hydroxyl groups associated with each temperature, the most recent and documented assumption (Bernard et al. [ 43 ]) was chosen.
The second and third water losses have been attributed to silanol and/or magnesium hydroxyl groups in M-S-H, but they may also comprise water present as a monolayer on the M-S-H surface [ 32 , 43 , 52 ]. Their attribution is controversial. recaps the views and assumptions of various authors. The structure of M-S-H has been compared to that of many phyllosilicates (sepiolite, talc, etc.) [ 32 , 33 , 35 , 38 , 43 ]. Nied et al. [ 32 ] suggested that the weight loss between 280 °C and 750 °C corresponds to hydroxyl groups with Mg 2+ , while the one between 750 °C and 840 °C would be linked to silanol groups on M-S-H. In the case of synthetic talc, Dumas et al. [ 67 ] attributed the weight loss (150&#;450 °C) to silanol (Si&#;OH) and magnesium (Mg&#;OH) hydroxides on the sheet edges. The next loss (450&#;750 °C) would be linked to the dehydroxylation of small particles, whereas the high temperature loss (750&#;850 °C) would correspond to the dehydroxylation of bigger particles and the formation of enstatite and silica. For Bernard et al. [ 43 ], and according to the work of Zhuravlev [ 68 ] on amorphous silica, the weight loss around 390 °C (observable IN on curves M/S = 0.78, 0.8 and 1) would match the dehydroxylation of silanol groups (on the surface) while the weight loss at 500 °C would be related to dehydroxylation of Mg&#;OH in M-S-H. Moreover, the removal of internal OH groups of silanols happened at around 900 °C.
X-ray diffractograms of three M-S-H pastes are presented in . The humps of M-S-H (see for positions) were observed on all diffractograms [ 32 , 46 , 66 ]. No brucite peaks were identifiable. The proportion of second broad reflection (~26 [2Θ] CuKα) relative to the rest of the diffractogram increased along with the M/S ratio, as was the case for diffractograms of M-S-H powders of Bernard (dashed lines in ) [ 43 ]. The first broad reflection (20 [2Θ] CuKα) simultaneously decreased, indicating a rearrangement of the structure as the M/S ratio increased. As proposed by Bernard, the first broad reflection would be linked to a structure similar to talc (a natural analogue of M-S-H) while the second broad reflection would be linked to serpentine. Thus, the X-ray diffractograms indicated a rearrangement of the structure with the increase in M/S, from a talc-like structure to serpentine, as Nied et al. observed in [ 32 ].
4.3. Microstructure and Porosity
Several techniques were used to characterize the microstructure and porosity of M-S-H pastes. illustrates the panel of porosity characterizations associated with the dimensional range of solids and pores in an M-S-H paste. In this section, we propose the characterization of the porous structure starting from the smallest (physisorption) to the largest scale (water saturation). Since the mixing protocol and the w/b could influence the structure and porosity of a paste, the tests were carried out on both pastes with manual (noted M, w/b~1.45) and mechanical (noted E, w/b~1.1) mixing. The results presented correspond to pastes MS_0-78_CS_T50_M/E, MS_1_CS_T50_E, and MS_1-3_CS_T50_M/E.
shows the N2 adsorption-desorption isotherms of M-S-H samples made with M/S = 0.78, M/S = 1.0 and M/S = 1.3, mixed manually ( b) or mechanically ( a). The mixing protocol and the w/b seemed to influence the form of the isotherm at relative pressures > 0.7 (for both the adsorption and desorption curves). The mechanical mixing&#;associated to a lower w/b&#;resulted in a smoother desorption for very high relative pressures and a lower adsorbed quantity. In the range p/p0 = {0; 0.7} the mixing process and w/b had no influence, probably due to the creation of &#;bigger&#; pores with manual mixing (where the w/b was higher). The internal structure of M-S-H remained the same since low pressures were not affected.
illustrates the different types of isotherms and hysteresis loops following the IUPAC classification [70]. The isotherms presented a hysteresis loop characteristic of a Type IV isotherm according to this classification. The adsorption part of the Type IV isotherm could be attributed to a monolayer-multilayer adsorption. The initial vertical slope at low p/p0 was characteristic of the presence of microporosity (equivalent diameter between 0.4 nm and 2 nm).
Hysteresis has been associated with capillary condensation taking place in mesopores (2&#;50 nm in diameter) [43]. M-S-H pastes made by mechanical mixing (lowest w/b), exhibited hysteresis comparable to H4 types with a small portion of the curve (on desorption at high p/p0) which would correspond to H2 type. The Type H4 loop is associated with narrow slit-like pores while the Type H2 is harder to interpret and is often associated with pore size and a not well-defined shape [70]. The form of the high pressure hysteresis for mechanically mixed pastes could therefore relate to the presence of specific bottleneck-shaped pores [71]. Overall, the structure we observed corresponded to plate-like materials with mesopores. The shape of the isotherms&#;especially of manually mixed pastes (highest w/b)&#;resembled that of synthetic saponite-like materials prepared by traditional hydrothermal crystallization at 513 K with H2O/SiO2 = 50 by Bisio et al. [72]. The form of the hysteresis was also similar to that of the M-S-H powders synthesized by Bernard [43] under hydrothermal treatment (180 °C for 4 days).
According to , the M/S ratio of M-S-H pastes appeared to influence the amount of N2 adsorbed: the lower the M/S, the higher the total N2 adsorbed.
The specific surface areas calculated with BET (SSABET) on M-S-H pastes hydrated from 2 (mechanically mixed) to 7.5 months (manually mixed; M/S = 1 is an exception, as it was hydrated for 2.5 months) are displayed in . illustrates the evolution of the specific surface as a function of the M/S ratio and the mixing protocol. Bernard&#;s data obtained on synthetic powders [43] are plotted in blue and green.
Table 5
Mechanically MixedManually MixedM/S0..30..3w/b1.111.11.451.451.45Age (days)Average specific surface area BET (m2/g)556......6Medium uncertainty1.20.81.10.81.10.6Standard deviation11.73.76.68.78.13.0External average specific surface area (t-plot) (m2/g)416......8Standard deviation6.51.87.426.35.49.5Vtot (cm3/g)230......3Standard deviation5.02.12.55.02.92.9Pore volume (cm3/g)0......245Open in a separate window
High SSABET were close to large surface areas reported by Bernard [43] for powders with a similar curing (1 year at 50 °C). As expressed by Bernard, specific surfaces were much lower for samples cured for 3.3 years at 20 °C due to a longer hydration time. Over time, the porous network could evolve. Initially, magnesium phases are formed upon contact between water and magnesium oxide and/or silica. As is the case with inner C-S-H [73], denser M-S-H could gradually be formed in the inner layer of reacted silica fume clusters, which would result in finer porosity, lower specific surface areas and lower pore volumes. In the case of M-S-H pastes with colloidal silica, no silica clusters were formed, reducing the possibility of a more dense M-S-H formation.
Contrary to Bernard&#;s hypothesis, according to which M-S-H forms in non-diluted systems or might exhibit a smaller SSA in field experiments, the experiments presented in this paper proved that M-S-H pastes showed similar specific surfaces to powders, both cured at 50 °C. The specific surface seemed independent of the mixing protocol for low M/S ratios (0.78 and 1). The SSABET decreased with the M/S ratio in M-S-H with a slightly different slope from that of Bernard&#;s data. At high M/S (M/S = 1 and M/S = 1.3), a gap arose between the data of Bernard, the data for manual mixing (w/b = 1.45) and the data for mechanical mixing (w/b = 1.1). The measurement uncertainty and the standard deviation (obtained by repeating the test) are too low to explain the difference in value between the protocols for these M/S values. High M/S ratios seem to be more affected by curing time and type of mixing. As for the effect of the mixing protocol at high M/S&#;highlighted in Section 3.2.&#;the high content of MgO compared to SiO2 implies a slower consumption of brucite. This could explain a different low-scale organization of the material between the pastes, following the initial brucite content (brucite is a crystallized phase, as opposed to M-S-H). The consumption of brucite to form M-S-H in a hardening shape could produce a different porous network.
Pore volumes and SSAext are plotted in . As was the case with SSABET, the values measured were higher than those of Bernard on powders equilibrated for 3.3 years at 20 °C [43]. No value was presented by Bernard on samples equilibrated for 1 year at 50 °C. SSAext and pore volumes were notably high for all our samples, implying a high content of micro- and mesopores. A clear trend was visible with the evolution of the M/S ratio. An increase in M/S implied a decrease in external surface area and pore volume. The porosity of samples with high M/S ratios (M/S = 1.3) seemed to contain less micro- and mesopores than the porosity of samples with low M/S ratios (M/S = 0.78).
The pore size distribution between 2.5 and 8 nm&#;according to the BJH method&#;is shown in . All samples showed a peak around 4 nm. The incremental pore volume (cm3/g) increased as the M/S atomic ratio decreased, confirming that the M-S-H pastes with high M/S contained less micro- and mesopores than the pastes with lower M/S. The common location of the peak and the similar appearance of the curves indicated that the mixing protocol and the w/b did not influence this range of pores.
In order to characterize the pore size distribution at the higher scale, MIP was used. The pore size distribution between 8 and 4 × 105 nm is shown in . The pastes manually mixed showed a family of small pores between 8 and 10 nm with a high peak centered at 26 nm, while the mechanically mixed pastes only exhibited a family of pores with a mean value centered at 9 nm. A manual mixing associated to a high w/b (1.45) therefore influenced the size and distribution of the mesopores by creating supplementary capillary pores (26 nm in diameter). The porosity values ( ) obtained with MIP will be discussed in the following paragraphs.
Table 6
Mechanically MixedManually Mixed
M/S0..30..3
w/b1.111.11.451.451.45
Age (days)MIPPorosity (%)46.....38-Kerdane and helium pycnometryBulk density (g/cm3)0.830.880.840.750.670.71True density (g/cm3)2.232.302.222.302.342.31Porosity (%)62......17Auto-radiographyPorosity (%)-Aged of 180 days---75.2-66.4Water PorosityPorosity (%)77......69Open in a separate window
Autoradiography was useful for establishing a link between the pore distribution and the overall porosity of the material, since it provides a 2D image of void percentage on samples and a histogram of the void percentage distribution. Autoradiography analyses were carried on three samples (one for M/S = 0.78 and two for M/S = 1.3). a&#;c show the autoradiography maps. A cracking phenomenon&#;similar to shrinkage&#;appeared in the samples ( b,c) as soon as water was removed from them by drying, vacuum, etc. This experimental perturbation did not prevent us from analyzing the porosity of the samples through the extraction of cracks and bubbles by deconvolution of the porosity histograms. The histograms associated with the maps ( d&#;f) show the distribution of the void ratio (porous areas and cracks). In the histograms&#;where all kinds of features were taken into account&#;the highest values approximately reach 100%. For M/S = 1.3, three Gaussian distributions were used to reproduce the histogram. For M/S = 0.78, only one Gaussian distribution was necessary. The characteristics of the Gaussian distributions are displayed in the histogram ( d&#;f). For M/S = 1.3, the first Gaussian distribution with µ = 58% (sample 1) or µ = 56.4% represented more than 80% of the histogram. The two other Gaussian distributions&#;with µ = 72% and µ = 89% (sample 1) or µ = 68.9% and µ = 85%&#;would correspond to bubbles and cracks. The removal of cracks corresponded to considering only the first Gaussian for each histogram. The average value of the porosity obtained by further treatment would then be 57.2% for M/S = 1.3 and 67.5% for M/S = 0.78.
The M/S-dependent effect on cracking was observed in the autoradiography maps. As explained in Section 4.3 and observed in , the sample with M/S = 1.3 showed numerous bubbles and cracks. The sample with M/S = 1 cracked during impregnation while the samples with M/S = 0.78 did not show large cracks. According to , the samples in question did not exhibit any difference in low-scale pore distribution, except for the amount of N2 adsorbed. Thus, the difference in the cracking pattern was not due to the finer distribution of the pores. While the pastes with the lowest M/S (M/S = 0.78) were the most porous, they underwent the least cracking. Preferential and faster cracking appearing for high M/S could therefore be linked to lower mechanical properties of the material.
Autoradiography and MIP provided a first idea of the total open porosity of the material. Other measurements were carried out in order to obtain a clearer picture of the porosity of the pastes ( ). The lowest porosity value was obtained with MIP, followed by the values acquired with helium pycnometry and kerdane, autoradiography and water porosity. These observations can be explained by the range and type of pores considered depending on the test.
MIP explored only the connected porosity; while pores > 8 nm were taken into account, large defects (air bubbles and very open cracks) were ignored. The porosity values obtained by helium pycnometry correspond to the open porosity, including cracks and bubbles. Autoradiography measured the connected porosities, with air bubbles and cracks being removed during post-processing (smallest visible pores = 10 μm). Water porosity took into account the connected porosity, bubbles and cracks. The latter is therefore the largest measured value. Moreover, the 105 °C drying protocol used for water porosity may consume certain hydrates, resulting in a potential small overestimation of the actual porosity. As each method had its limitations, it was interesting to combine them all to characterize the material.
A general trend could still be observed. Manually mixed pastes had a slightly higher porosity (10% more) than mechanically mixed ones (these results were consistent with the higher w/b ratio used for manual mixing). Overall, the porosity of these pastes was high. The influence of the M/S ratio on the overall porosity was difficult to assess because the pastes were very porous (due to the high w/b ratio imposed). C-S-H pastes cast with a similar protocol (colloidal silica) also have a high porosity, close to 60% according to Kangni-Foli [74]. The effect of mixing and w/b disappeared only on a smaller scale. According to Bernard [75], the molar volume of M-S-H increases with increasing M/S. It is expected that the higher the solid molar volume, the lower the pore volume [76]. This observation can be found in our study through N2 physisorption and MIP. The more the M/S increases, the more the absorbed amounts of N2 and Hg and the specific surface area decrease, thus indicating a higher mesoporosity. On a larger scale, the porosities measured by the different techniques show this same trend. The pastes were mainly mesoporous, with a small amount of micropores and some defects appearing on a larger scale (bubbles due to mixing and cracks due to pre-treatments).
The microstructure of M-S-H pastes was characterized in this study. On a smaller scale, at the level of silica sheets ( ), physisorption analyses described the material as a highly porous phase with plate-like micropores and mesopores. The increase in M/S implied a decrease in the quantity of N2 adsorbed, as well as a reduction of the specific surface (SSABET), the SSAext and the micro- and mesopore volume. At the level of capillary pores to clusters of globules of M-S-H ( ), MIP was useful for distinguishing the effect of the mixing protocol. Mechanically mixed pastes exhibited a mesopore family around 10 nm, while manual mixing also created a high amount of mesopores around 30 nm. The mechanical mixing&#;which lasted longer and used a higher speed and strength&#;helped reduce the w/b, leading to a denser paste with less porosity. On a larger scale, porosity measurement protocols provided information about open porosity. On autoradiography maps, we observed the formation of cracks as soon as the water was removed from the samples. This mechanism highlighted the mechanical strength and sensibility of M-S-H in a relatively humid environment. The removal of cracks and bubbles from histograms of porosity showed the high open porosity of the pastes (approximately 60% for manually mixed pastes). This high value was supported by other characterization methods, although the porosity measurements were influenced by pre- or post-treatment of the samples. Drying at 105 °C after water saturation and bulk density measurements could lead to the calcination of hydrates, resulting in an overestimated porosity. Overall, the open porosity of M-S-H pastes could be considered to be 70% for manually mixed pastes and 62% for mechanically mixed pastes, with this percentage increasing as the M/S ratio decreases.
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