[About Cast Stone]

Attribute

Cast Stone Limestone

Architectural
Precast Concrete

Constituents Portland cement, fine crushed natural stone, and  manufactured or natural sand.   Iron oxides added for color. Carbonated lime Sand, cement, larger aggregates
Size of aggregate 3/8" or less none 3/8" to 3/4"
Structural use Can be reinforced, but has limited structural applications. Cannot be reinforced, used primarily as non- structural veneer Structural or non structural
Typical uses Architectural feature, trim, ornament, or facing:   copings, sills, banding, door and window surrounds, bases Architectural feature, trim, ornament, or facing:   copings, sills, banding, door and window surrounds, bases Architectural concrete structural pieces and non-structural panels, window units, etc.
Anchors supplied
by manufacturer
No No Usually supplied by on-site erector.
Method of anchor
attachment to stone
Anchor attaches to pre-formed anchor slots and dowel holes Anchor attaches to cut anchor slots and dowel holes Inserted in piece as it is poured at manufacturing facility or installed separately at the job site
Surface texture Fine grain to simulate natural stone, textures optional Fine grain, with directional grain lines Usually exposed aggregate or other finishes not intended to simulate natural stone
Method of forming
into shapes
Ramming moist zero-slump mix into rigid formwork until densely compacted and demoulded immediately Mined, cut, and fabricated Pouring wet concrete mix into form, vibrating, and removing forms the following day
Colors available Almost unlimited Limited to white, buff, gray Almost unlimited
Compressive strength 6,500 psi minimum ASTM C1194 4,000 psi minimum ASTM C170 5,000 PSI minimum ASTM C39
Water absorption 6% maximum 7.5% maximum 7% maximum
Bug holes or air voids No No Yes
Metal reinforcing Yes No Yes
Specification division 04720 04423 03450
Industry association Cast Stone Institute
813 Chestnut Street, PO Box 68
Lebanon, PA 17042
Phone: (717) 272-3744
Fax: (717) 272-5147  www.caststone.org

staff@caststone.org
Indiana Limestone Institute of America, Inc., Stone City Bank Building, Suite 400, Bedford, IN  47421
(812) 275-4426
www.ilia.com
Architectural Precast Association
6710 Winkler Road, Ste.8
Fort Myers, FL 33919
(239) 454-6989
Fax (239) 454-6787 www.archprecast.org

info@archprecast.org 
weight/cubic foot 140 144 145
Keys to optimum economy Piece repetition, average sizes 1.5 - 2.0 cu. ft., one flat unexposed surface Pieces with simple profiles, short distance of job site from mines ideal for larger structural pieces such as panels, precast lintels

Uses:

Cast stone is used mostly as a decorative exterior veneer product, similar in detail to natural limestone, marble and granite.  Cast stone is usually used to replicate the look of  limestone.  Cast stone is typically used as an architectural feature, trim, ornament, or facing.   Typical units include base, banding, sills, door and window surrounds, coping, quoins, and water tables.  Less common but popular are decorative pieces such as columns, balls, and balusters.  Cast stone is specified under section 04720.

Cost:

Keys to economical manufacturing and competitive pricing depends on the size of individual piece, piece design, repetition of the individual profile, ornamentation, and the color desired.

Size:  Rather than cost per lineal foot or cost per square foot, the wide range of sizes that can be made in Cast Stone makes it more convenient to view cost in terms of cubic feet per piece.  The ideal unit cost (per cubic foot) is achieved when individual piece sizes are 1.5 to 2.0 cubic feet.  The ideal length for straight pieces such as copings, sills, banding is between 4' to 6'.

Piece Design:  By including one flat unexposed side in the design of the individual piece (see Value Engineering section), production time and curing time will be reduced to a minimum, and costs will be kept low.  Typical profiles with one flat unexposed side include base, water table, banding, sills, header, and coping.  If more than one flat unexposed side is designed such as L-shaped or U-shaped pieces, costs increase due to the intricate mold required and the additional production time.  Pieces such as balusters and balls that require molds that are two-sided, with minimal unexposed surface, add costs due to the longer time to construct molds and extreme care that must be used during the production process.

Profile Repetition:  The more that an individual mold can be amortized over a production run, the lower the cost per piece, even if the length of the profile varies.  Various piece lengths can made by using an adjustable filler or stop in the mold during the production process.

Profiles and Rustication:  Cast stone can be molded to a variety of shapes and the architect is encouraged to exercise design freedom when drawing Cast Stone profiles.  In contrast to natural cut stone, profiles with curves and bevels are encouraged because the additional cost to incorporate these shapes into molds is minimal compared to flat pieces with defined edges. 

Ornamentation: It should be noted that highly intricate designs that require making a model, a "positive" needed to make the mold be sculpted from clay or other material, adds to the cost.  This would be the case when reproducing shapes on historical buildings.

Color:  The more chromatic the desired color, the more each piece costs.  Cast stone colors that are standard and that have no additional costs are the colors that are indicated as "Natural Colors" in the colors section of this website.

Advantages:

The advantages of Cast Stone include its ability to:
  • Replicate natural stone at a fraction of the cost
  • Offer precise colors and form a wide variety of shapes
  • Consistently deliver quality because it is a manufactured product
  • Be easily cut to length in the field
  • Simulate the look of natural stone
  • Deliver a time-tested freeze thaw durability
  • Replace the stone on historical buildings.

Limitations:

Although Cast Stone can be used as a substitute for limestone and architectural precast concrete, there are some limitations.  Where precast concrete, division 03450, is specified and is designed as non-structural or minimally load bearing, Cast Stone can be used.  In instances where the precast concrete is structural or a combination of structural and decorative, Cast Stone should not be used. 

Since Cast Stone is a division 4 masonry material, sizes and connection methods should be within the scope of work to be performed by the masonry contractor.  In addition to not designing structural pieces, the vibrant dry tamp method of Cast Stone, which involves ramming earth-moist concrete against rigid formwork until ready for immediate removal from the mould, does not lend itself to large panels.  The ideal panel size is approximately 2' x 5'.  Typical panel thickness is 3 5/8".  This size enables our plant to be most productive, and therefore, we can be most competitive on bids that contain this or similar sizes.  The typical maximum size should be no larger than 3' x 8'.

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