Manufacturing > Production
 Below is an overview of the fundamentals of Cast Stone, the manufacturing process, and gives an overview of detailing it with the Project Budget in mind. Please click on the highlighted links to obtain further information on a particular topic. In addition, our Related Links Page can direct you to organizations such as the Cast Stone Institute and the AIA where additional information is available.
Cast Stone is a highly refined architectural precast concrete building stone manufactured from a blend of Portland cement and coarse and fine aggregates such as limestone, quartz, granite and/or marble and inorganic iron oxide pigments to achieve the desired color and appearance while maintaining durable physical properties which exceed most natural cut building stones. Cast Stone is an excellent replacement for natural cut limestone, brownstone, sandstone, bluestone, granite, slate, marble and other natural building stones as well as terra-cotta. Cast Stone is generally used as an architectural feature, trim, ornament or facing for buildings or other structures.
Manufacturing Cast Stone
Manufacturing Cast Stone is generally regarded as the most labor-intensive of all concrete products' manufacturing processes. There are seven distinct disciplines inherent to Corinthian Cast Stone’s production sequence:
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Estimating and Value Engineering:
During this phase the project is discussed with the buyer and ideas are reviewed that will enhance the project aesthetically as well as reducing the budget required, while conforming to the Architects’ design intent. Items thoroughly examined are repetition (the economy of scale), profile design, maximum dimensional considerations and anchoring details. Estimating and takeoffs are done from Architectural Drawings or if the job is simple, only faxed sketches may be required.
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Cast Stone Detailing:
 is of premier importance to proper fabrication of custom Cast Stone and to the overall project. The Cast Stone Detailing Department is where the Architects’ and Designers’ Visions turn into production drawings. Corinthian Cast Stone generates drawings that conform to the standards of the Cast Stone Institute. Shop drawings are prepared showing details of the stone to be provided including: profiles, cross-sections, reinforcement, exposed faces, arrangement of joints, annotation of stone types and their layout and location on the structure. Comprehensive dimensions are shown on all shop drawings. Units are identified with a piece marking system. Finished surfaces are shown, where exposed to view. Additionally, when required to do so, or when it will simply benefit the project, our drafting department will 3-D render a particular stone or an entire façade.
Before beginning a new job, the detailer verifies that the contract drawing set is the most recent available and secure the Full Set of Construction Documents (predicated by the scope of work, all elevations. sections, details, structural drawings and surveys are essential, less Mechanicals, Electrical and Plumbing documents). Additionally the construction schedule or the sequence of how the building is to be built is essential, as the shop drawings are prepared in that sequence
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Pattern and Mould Shoppe:
 The Mould Shoppe is where the Architects Vision begins to turn into a tangible product. Shop drawings and assembly details are reviewed and layouts are done. According the size of the project and the amount of detail, moulds are made of different materials. High quantity or fast track jobs generally have moulds built of wood, plastics and fiberglass. Very ornate pieces may have moulds built of rubber or fiberglass. In either case, the Craftsman responsible for the project determines the best material for the job.
Patterns are made in the same area of the Shoppe. Patterns or Models are a positive image, actual size of the piece to be recreated. If necessary, Corinthian’s Craftsmen will make moulds in the field. If an actual piece from the building is brought for replication, the Artisan will re-sculpt the stone building back all of the original details, from an oak leaf or an egg and dart to the rake lines on a piece of terra-cotta. The model is then back to the Mould Shoppe for final inspection and production of the working mould.
Whether made in the Shoppe or in the field, out of wood or from rubber, the Craftsmen painstakingly pay attention to detail. Pattern and Mould Making is an art form that is passed from a Craftsman to an Apprentice allowing the techniques of old to pass to the next generation of Mould Makers.
Corinthian Cast Stone Inc. manufactures using the "Vibrant Dry Tamp" (VDT) system. This requires a precisely proportioned mix design consisting of carefully graded and washed natural gravel and sand combined with crushed graded stone such as granite, marble, quartz, or limestone conforming with ASTM C 33.The mixtures are proportioned for maximum density and to produce the required color and finish, defined as:
"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."
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Cast Stone fabricated using the VDT production system
Cast Stone fabricated using the VDT production system is made by vibratory ramming earth moist, zero-slump concrete against rigid formwork until it is densely compacted and ready for immediate removal from the form.; enabling as many as 100 pieces to be cast from a single mold in an eight-hour day thus it is ideally suited to fast-track construction projects due to its production capability. The VDT process guarantees total absence of bug holes and a fine grained finish which is almost impossible to distinguish from natural stone.
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Curing is an integral component to proper Cast Stone fabrication
 Curing is an integral component to proper Cast Stone fabrication. Although the actual mix designs that Corinthian Cast Stone Inc. uses are proprietary, it is common knowledge that a rich cement/aggregate ratio is normally used in the fabrication of Cast Stone. The matrix achieves its strength through a process called hydration. With the addition of the correct amount of water, cement gels into a paste that binds the components of the mix design together to form hardened concrete.
The climate during the hardening of the concrete is of enormous importance for the quality of the hydration and the strength gain. The ambient temperature plays an important role in determining the speed of the hydration process. The warmer the air is, the warmer the concrete is and the quicker the concrete gains strength. The three most important elements in the curing chamber are: moisture, temperature and carbon dioxide. All three have a significant effect on the hydration process at elevated, though controlled levels. Properly cured Cast Stone (CSI 4720) will have a substantially higher compressive strength and a lower cold water absorption rate than natural limestone (CSI 4400) or precast concrete (CSI 3450). The VDT method, due to its low water/cement ratio typically yields higher compressive strengths than low-slump concrete.
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The final procedure in the manufacturing of Cast Stone
The final procedure in the manufacturing of Cast Stone is the removal of the cement skin from the outer surface. This exposes the fine aggregates, which make up the matrix. The removal of the cement skin assures the product will undergo minimal color and texture changes as a result of weathering. The use of siloxane water repellant is a reliable way to keep the Cast Stone looking new without changing its appearance. When sealers are used, be sure to follow the manufacturer’s instructions and always test a small inconspicuous area prior to full scale application.
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Inspection and Packaging:
To ensure proper fit and to facilitate the setter’s job, the Cast Stone is inspected dimensionally using approved shop drawings. The Cast Stone Institute tolerances are applied to the required dimensions, if they are more stringent than the project specifications, or if no specifications are available. On a daily basis, the production runs are checked for color and finish against the approved sample, regardless of whether they are standard colors. All Corinthian Cast Stone units are permanently marked on an unexposed side of the stone, according to the approved shop drawings.
Corinthian Cast Stone will arrive at your jobsite on flatbed trucks; shrink wrapped on readily identifiable pallets that can be easily coordinated with the approved shop drawings.
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Degrees of Customization:
Cast Stone is often the defining element on the façade of the building. It serves to accent the other masonry as well as the architecture of the project. Corinthian Cast Stone strives to detail Cast Stone units that conform to the Architects Design Intent while gaining the economy of scale and the benefits derived thereof. Cast Stone is available in various degrees of customization.
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Finishes
Corinthian Cast Stone Inc. offers a variety of finishes that simulate natural cut building stone. While our standard finish is a fine grained texture similar to limestone, the Company has successfully completed projects with Bush Hammed , ADA nonslip compliant, Natural Cleft, and simulated Terra-Cotta Rake Line finishes. In short any finish that has been tooled or carved into natural cut building stones ( and many others that can’t) can be achieved by Corinthian Cast Stone Inc.
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Economy of Scale
The cost per unit depends greatly on the design of the individual stone unit, the amount of repetition, the specified finish and the bid documents. On average, however, Cast Stone costs less than quarried (and then milled or carved) stone. There are several reasons. One is that Cast Stone is a molded product and once the mould is made, there is no additional tooling cost incurred, whereas each piece of cut stone must be carved individually. Another reason is speed; VDT Cast Stone is produced rapidly, depending upon the size and profile required, up to 100 pieces may be fabricated from one mould in one work shift. Additionally freight may be an issue; usually quarried stone must be hauled over long distances. Most of the limestone in this country is hauled from Indiana adding additional cost and possibly time to the project.
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Summarily
attributable to its physical and aesthetic properties, its price point, speed of fabrication and consistency in the finished product, Cast Stone is a truly superior alternative to natural cut building stone.
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