Section 04-72-00-04 Architectural Cast Stone
This specification encompasses basic requirements for Cast Stone, a refined architectural concrete building unit manufactured to simulate natural cut stone, used in unit masonry applications. Cast Stone is a masonry product, used as an architectural feature, trim, ornament or facing for buildings or other structures.
Materials and processes used for manufacturing Cast Stone vary widely according to the aggregates locally available to the manufacturers and the processes and techniques used by the manufacturers to obtain the desired appearance and physical properties. Of paramount importance in molding Cast Stone is the need to employ a properly proportioned mixture of white and/or grey cements, manufactured or natural sands, carefully selected crushed stone or well graded natural gravel and mineral coloring pigments to achieve the desired appearance while maintaining durable physical properties.
Although a variety of casting methods are used, production conforming to this standard will exceed minimum requirements for compressive strength and weathering qualities essential for normal installations as a suitable replacement for natural cut limestone, brownstone, sandstone, bluestone, granite, slate, keystone, travertine and other natural building stones.
1.1. Section Includes – Architectural Cast Stone.
A. Scope – All labor, materials and equipment to provide the Cast Stone shown on architectural drawings and as described in this specification.
1. Manufacturer shall furnish Cast Stone covered by this specification.
2. Installing contractor shall unload, store, furnish all anchors, set, patch, clean and seal (optional) the Cast Stone as required.
1.2. Related Sections
A. Section – 01 33 00 – Submittal Procedures.
B. Section – 04 05 13 – Masonry Mortaring…
C. Section – 04 05 16 – Masonry Grouting.
D. Section – 04 05 19 – Masonry Anchorage and Reinforcing.
E. Section – 07 90 00 – Joint Protection.
A. ACI 318 – Building Code Requirements for Reinforced Concrete.
B. ASTM A 185 – Standard Specification for Steel Welded Wire Reinforcement, Plain, for Concrete.
C. ASTM A 615/A 615M – Standard Specification for Deformed and Plain Billet-Steel Bars for Reinforced Concrete.
D. ASTM C 33 – Standard Specification for Concrete Aggregates.
E. ASTM C 150 – Standard Specification for Portland Cement.
F. ASTM C 173 – Standard Test Method for Air Content of Freshly Mixed Concrete by the Volume Method.
G. ASTM C 231 – Standard Test Method for Air Content of Freshly Mixed Concrete by the Pressure Method.
H. ASTM C 260 – Standard Specification for Air-Entrained Admixtures for Concrete.
I. ASTM C 270 – Standard Specification for Mortar for Unit Masonry.
J. ASTM C 426 – Standard Test Method for Linear Shrinkage of Concrete Masonry Units.
K. ASTM C 494/C 494M – Standard Specification for Chemical Admixtures for Concrete.
L. ASTM C 618 – Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use as a Mineral Admixture in Concrete.
M. ASTM C 666 – Standard Test Method for Resistance of Concrete to Rapid Freezing and Thawing.
N. ASTM C 979 – Standard Specification for Coloring Pigments for Integrally Pigmented Concrete.
O. ASTM C 989 – Standard Specification for Ground Granulated Blast-Furnace Slag for Use in Concrete.
P. ASTM C 1194 – Standard Test Method for Compressive Strength of Architectural Cast Stone.
Q. ASTM C 1195 – Standard Test Method for Absorption of Architectural Cast Stone.
R. ASTM C 1364 – Standard Specification for Architectural Cast Stone.
S. ASTM D 2244 – Standard Test Method for Calculation of Color Differences from Instrumentally Measured Color Coordinates.
T. Cast Stone Institute® Technical Manual (Current Edition)
A. Cast Stone – a refined architectural concrete building unit manufactured to simulate natural cut stone, used in unit masonry applications.
1. Dry Cast Concrete Products – manufactured from zero slump concrete.
a. Vibrant Dry Tamp (VDT) casting method: Vibratory ramming of earth moist, zero- slump concrete against a rigid mold until it is densely compacted.
b. Machine casting method: manufactured from earth moist, zero-slump concrete compacted by machinery using vibration and pressure against a mold until it becomes densely consolidated.
B. Wet Cast Concrete Products – manufactured from measurable slump concrete.
1. Wet casting method: manufactured from measurable slump concrete and vibrated into a mold until it becomes densely consolidated.
1.5. Submittal Procedures
A. Comply with Section 01 33 00 – Submittal Procedures.
B. Samples: Submit pieces of the Cast Stone that are representative of the general range of finish and color proposed to be furnished for the project.
C. Test results: Submit manufacturers test results of Cast Stone previously made by the manufacturer.
Shop Drawings: Submit manufacturers shop drawings including profiles, cross-sections, reinforcement, exposed faces, arrangement of joints (optional for standard or semi-custom installations), anchoring methods, anchors (if required), annotation of stone types and their location.
1.6. Quality Assurance
A. Manufacturer Qualifications:
1. Manufacturer shall have sufficient plant facilities to produce the shapes, quantities and size of Cast Stone required in accordance with the project schedule.
2. Manufacturer shall submit a written list of projects similar in scope and at least three (3) years of age, along with owner, architect and contractor references.
B. Standards: Comply with the requirements of the Cast Stone Institute® Technical Manual and the project specifications. Where a conflict may occur, the contract documents shall prevail.
C. Mock-up (Optional) Provide full size unit(s) for use in construction of sample wall. The approved mock-up shall become the standard for appearance and workmanship for the project.
1.7 Acceptable Manufacturer
2.1. Architectural Cast Stone
A. Comply with ASTM C 1364
1. Physical properties: Provide the following:
2. Compressive Strength – ASTM C 1194: 6,500 psi (45 Mpa) minimum for products at 28 days.
3. Absorption – ASTM C 1195: 6% maximum by the cold water method, or 10% maximum by the boiling method for products at 28 days.
4. Air Content – ASTM C173 or C 231, for wet cast product shall be 4-8% for units exposed to freeze-thaw environments. Air entrainment is not required for VDT products.
5. Freeze-thaw – ASTM C 1364: The CPWL shall be less than 5% after 300 cycles of freezing and thawing.
6. Linear Shrinkage – ASTM C 426: Shrinkage shall not exceed 0.065%.
B. Job site testing – One (1) sample from production units may be selected at random from the field for each 500 cubic feet (14 m 3) delivered to the job site.
1. Three (3) field cut cube specimens from each of these samples shall have an average minimum compressive strength of not less than 85% with no single specimen testing less than 75% of design strength as allowed by ACI 318.
2. Three (3) field cut cube specimens from each of these samples shall have an average maximum cold-water absorption of 6%.
3. Field specimens shall be tested in accordance with ASTM C 1194 and C 1195.
2.2. Raw Materials
A. Portland cement – Type I or Type III, white and/or grey, ASTM C 150.
B. Coarse aggregates – Granite, quartz or limestone, ASTM C 33, except for gradation, and are optional for the VDT casting method.
C. Fine aggregates – Manufactured or natural sands, ASTM C 33, except for gradation.
D. Colors – Inorganic iron oxide pigments, ASTM C 979 except that carbon black pigments shall not be used.
E. Admixtures- Comply with the following:
1. ASTM C 260 for air-entraining admixtures.
2. ASTM C 494/C 495M Types A – G for water reducing, retarding, accelerating and high range admixtures.
3. Other admixtures: integral water repellents and other chemicals, for which no ASTM Standard exists, shall be previously established as suitable for use in concrete by proven field performance or through laboratory testing.
4. ASTM C 618 mineral admixtures of dark and variable colors shall not be used in surfaces intended to be exposed to view.
5. ASTM C 989 granulated blast furnace slag may be used to improve physical properties. Tests are required to verify these features.
F. Water – Potable
G. Reinforcing bars:
1. ASTM A 615/A 615M. Grade 40 or 60 steel galvanized or epoxy coated when cover is less than 1.5 in. (37 mm).
2. Welded Wire Fabric: ASTM A 185 where applicable for wet cast units.
H. All anchors, dowels and other anchoring devices and shims shall be standard building stone anchors commercially available in a non-corrosive material such as zinc plated, galvanized steel, brass, or stainless steel Type 302 or 304.
2.3. Color And Finish
A. Match sample on file in architect’s office.
B. All surfaces intended to be exposed to view shall have a fine-grained texture similar to natural stone, with no air voids in excess of 1/32 in. (0.8 mm) and the density of such voids shall be less than 3 occurrences per any 1 in.2 (25 mm2) and not obvious under direct daylight illumination at a 5 ft (1.5m) distance.
C. Units shall exhibit a texture approximately equal to the approved sample when viewed under direct daylight illumination at a 10 ft (3 m) distance.
1. ASTM D 2244 permissible variation in color between units of comparable age subjected to similar weathering exposure.
a. Total color difference – not greater than 6 units.
b. Total hue difference – not greater than 2 units.
D. Minor chipping resulting from shipment and delivery shall not be grounds for rejection. Minor chips shall not be obvious under direct daylight illumination from a 20-ft (6 m) distance.
E. The occurrence of crazing or efflorescence shall not constitute a cause for rejection.
F. Remove cement film, if required, from exposed surfaces prior to packaging for shipment.
A. Reinforce the units as required by the drawings and for safe handling and structural stress.
B. Minimum reinforcing shall be 0.25 percent of the cross section area.
C. Reinforcement shall be noncorrosive where faces exposed to weather are covered with less than 1.5 in. (38 mm) of concrete material. All reinforcement shall have minimum coverage of twice the diameter of the bars.
D. Panels, soffits and similar stones greater than 24 in. (600 mm) in one direction shall be reinforced in that direction. Units less than 24 in. (600 mm) in both their length and width dimension shall be non-reinforced unless otherwise specified.
E. Welded wire fabric reinforcing shall not be used in dry cast products.
A. Cure units in a warm curing chamber approximately 100ºF (37.8ºF) at 95 percent relative humidity for approximately 12 hours, or cure in a 95 percent moist environment at a minimum 70ºF (21.1ºF) for 16 hours after casting. Additional yard curing at 95 percent relative humidity shall be 350 degree-days (i.e. 7 days @ 50ºF (10ºF) or 5 days @ 70ºF (21ºF)) prior to shipping. Form cured units shall be protected from moisture evaporation with curing blankets or curing compounds after casting.
2.6. Manufacturing Tolerances
A. Cross section dimensions shall not deviate by more than 1/8 in. (3 mm) from approved dimensions.
B. Length of units shall not deviate by more than length/ 360 or 1/8 in. (3 mm), whichever is greater, not to exceed 1/4 in. (6 mm).
1. Maximum length of any unit shall not exceed 15 times the average thickness of such unit unless otherwise agreed by the manufacturer.
C. Warp, bow or twist of units shall not exceed length/ 360 or 1/8 in. (3 mm), whichever is greater.
D. Location of dowel holes, anchor slots, flashing grooves, false joints and similar features – On formed sides of unit, 1/8 in. (3 mm), on unformed sides of unit, 3/8 in. (9 mm) maximum deviation.
2.7. Production Quality Control
1. Test compressive strength and absorption from specimens selected at random from plant production.
2. Samples shall be taken and tested from every 500 (14 m3) cubic feet of product produced.
3. Perform tests in accordance ASTM C 1194 and C 1195.
4. New and existing mix designs shall be tested for strength and absorption compliance prior to producing units.
2.8. Delivery, Storage And Handling
A. Mark production units with the identification marks as shown on the shop drawings.
B. Package units and protect them from staining or damage during shipping and storage.
C. Provide an itemized list of product to support the bill of lading.
A. Installing contractor shall check Cast Stone materials for fit and finish prior to installation. Do not set unacceptable units.
3.2. Setting Tolerances
A. Comply with Cast Stone Institute® Technical Manual.
B. Set stones 1/8 in. (3 mm) or less, within the plane of adjacent units.
C. Joints, plus – 1/16 in. (1.5 mm), minus – 1/8 in. (3 mm).
A. Joint size:
1. At stone/brick joints 3/8 in. (9.5 cm).
2. At stone/stone joints in vertical position 1/4 in. (6 mm) (3/8 in. (9.5 mm) optional).
3. Stone/stone joints exposed on top 3/8 in. (9.5 mm).
B. Joint materials:
1. Mortar, Type N, ASTM C 270.
2. Use a full bed of mortar at all bed joints.
3. Flush vertical joints full with mortar.
4. Leave all joints with exposed tops or under relieving angles open for sealant.
5. Leave head joints in copings and projecting components open for sealant.
C. Location of joints:
1. As shown on shop drawings.
2. At control and expansion joints unless otherwise shown.
A. Drench units with clean water prior to setting.
B. Fill dowel holes and anchor slots completely with mortar or non-shrink grout.
C. Set units in full bed of mortar, unless otherwise detailed.
D. Rake mortar joints 3/4 in. (18 mm) in. for pointing.
E. Remove excess mortar from unit faces immediately after setting.
F. Tuck point unit joints to a slight concave profile.
3.5. Joint Protection
A. Comply with requirements of Section 07 90 00.
B. Prime ends of units, insert properly sized backing rod and install required sealant.
3.6. Repair and Cleaning
A. Repair chips with touchup materials furnished by manufacturer.
B. Saturate units to be cleaned prior to applying an approved masonry cleaner.
C. Consult with manufacturer for appropriate cleaners
3.7. Inspection and Acceptance
A. Inspect finished installation according to Bulletin #36.
B. Do not field apply water repellant until repair, cleaning, inspection and acceptance is completed.