• Cast Stone Applications
• The Manufacturing of Cast Stone
• Casting Methods
  

• Attributes
• Comparison of Cast Stone to Natural Stone
• Pricing of Cast Stone

Cast stone is most commonly used in a decorative application similar to natural limestone and other stones. Cast stone is typically used as an architectural feature, trim, ornament, or facing. The most commonly used units include banding, sills, door and window surrounds, coping, quoins, and water tables. Other less common uses include columns, balls, medallions and a variety of others that are all suited to cast stone.

Cast Stone has been a prime building material for hundreds of years. The earliest known use of Cast Stone dates back to around the year 1138 in France. Cast Stone was first used extensively in London in the year 1900 and gained widespread acceptance in America in 1920.

Cast Stone is generally regarded as the most labor-intensive of all concrete products' manufacturing processes. Every aspect of the cast stone process is crucial. It is this process that allows cast stone to be available in the variety of custom designs it is today.

The process begins with the drafting department. A vast knowledge of architectural styles and designs, experience, familiarity of the manufacturing methods and the techniques of the masonry contractor are vital to ensuring that a job is completed with the highest degree of quality.

The mold shop is another important step in the process. An eye for detail and excellence in craftsmanship are required. Because a variety of materials are available for use, an experienced mold maker must know which material will fit a particular application. Wood is the most commonly used material, but fiberglass, steel and rubber are also better-suited to certain projects. The variety of materials available to build molds with allows the manufacturer the ability to create cast stone pieces to fit a large range of different projects. Molds must be built with a high degree of quality because that one mold can produce up to 250 pieces. This is what allows cast stone to become a cost-effective alternative.

After the piece is removed from the mold, it must be cured. This curing process is crucial. When cured in a warm and moist environment, a compressive strength of 6500 psi or higher is obtained and a water absorption of 6% or lower; both exhibiting the strength of cast stone. The surface layer of cement is removed with an acid wash to reveal the white stone aggregates creating a look that is similar in color, texture and appearance to natural stone.

This process creates a vast array of customization options. Because of the customization available with cast stone, it can add the most personalized and unique element to the project.

The two casting methods used by Superior Precast are the “Vibrant Dry Tamp" method (otherwise known as “dry cast”) and the "Wet Cast" method. Both methods are required to adhere to the highest standards. Cast stone is usually produced with a low water-to-cement ratio mixture that has a "dry" consistency, yielding higher compressive strengths than low-slump concrete. The mixture of earth moist, zero-slump concrete is consolidated into a mold until it is densely compacted using an air driven tamping device. It is ready for immediate removal from the form. This method allows a great number of pieces to be cast from a single mold in a work day and enables fast-track production. The dry cast process guarantees total absence of bug holes and a look that is very similar to natural stone.

Each method requires a carefully proportioned mix design. Our mix designs consist of graded and washed natural gravel and sand combined with crushed limestone to meet the latest requirements of ASTM C 33. The mixtures are proportioned for maximum density. White cement is used as the base for all of our standard colors. A mixture of Grey Portland cement, white cement and coloring pigments are used to achieve a variety of other colors. Numerous admixtures are available today to be used in the dry cast method. We add a waterproofing admixture to increase strength and reduce absorption for improved freeze-thaw durability. An admixture is also added to wet cast concrete to allow it to withstand numerous freeze-thaw cycles for long-lasting durability.

Today, Cast Stone is considered a highly versatile, long-lasting, cost-effective and truly superior alternative to natural cut stone. Combined with its ability to simulate a variety of natural stones, cast stone offers many positive characteristics and advantages over cut stone. It is readily available with a relatively short lead time – an average of four to six weeks after the approval of shop drawings. Perhaps most importantly, it is pleasing to the eye.

Advantages:

• Integrally reinforced with steel
• Repetitive profiles allow manufacturing at a fraction of the cost
• Consistent quality
• Weathers better because the process is controlled
• Offers a wide range of precise colors and a variety of shapes
• Easily cut to length in the field
• Deliver a time-tested freeze-thaw durability
• Ability to replication deteriorating stone on historical buildings for restoration
  
  

Limitations:

• Should not be used to serve a structural function
• Sizes and connections should always be within the range of work required by the mason contractors
• The dry cast method does not work well with large panels – the optimum size is around 3 5/8” x 2’ x 5’
  
  

Cast stone is a Portland cement-based product manufactured with high quality fine and coarse aggregate. Simulated stone or other products that attempt to replicate the look of natural stone are less durable and not nearly as well time-tested. Using a high percentage of fine aggregate creates a very smooth, consistent texture for the products being cast, allowing them to resemble natural cut stone. In general, cast stone will cost less than natural stone.

The pricing of cast stone depends on various factors including the job size, repetition of pieces and mold reuse, the complexity of the job, size and design of the piece, how many sides of the piece are exposed and color.

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, production time, curing time and costs will be reduced to a minimum. Typical profiles with one flat unexposed side include base, water table, banding, sills, header, and coping. Some pieces are designed with more than one flat unexposed side, which causes costs to increase due to the intricate mold required and the additional production time. The more complicated a piece is, the higher the cost will be.

Profile Repetition:
Cost can be lowered tremendously the more times that an individual mold can be used over a production run. Different lengths of the same profile can be easily achieved by using an adjustable block in the mold during the production process.

Profiles:
Cast stone can be molded to a variety of shapes. Profiles with curves, radius, bevels and chamfers can be built into the mold at a minimal cost.

Ornamentation:
Highly intricate designs with heavy mold work or molds that need to be made from a material other than wood will add to the cost.

Color:
The more chromatic the desired color, the more each piece costs. Standard colors are listed in the Product Catalog section and are at no additional cost. Colors other than those listed will raise the cost.