Types of Architectural Precast ConcreteCast Stone and Glass-Fiber-Reinforced Concrete
Unlike concrete used solely for utilitarian purposes, the function of architectural precast concrete is primarily aesthetic. That means special concrete mixes, such as cast stone and glass-fiber-reinforced concrete, are often used to achieve the best appearance without compromising performance.
Cast stone is a type of architectural precast concrete that combines the strength and durability of reinforced concrete with the appearance of natural stone. It's typically made of portland cement, fine and coarse aggregates (usually granite, quartz or limestone), natural or manufactured sands and high-performance chemical admixtures. As an architectural trim or ornament, high-quality cast stone is a time-tested alternative to natural cut stone. It has a high compressive strength, excellent long-term durability, low water absorption, enduring freeze-thaw resistance, and good resistance to abrasion and dirt. With the inclusion of steel reinforcement in structural elements, such as columns, cast stone also possesses good tensile and flexural strength.
Glass-fiber-reinforced concrete (GFRC) is a lightweight alternative to cast stone combining cement, sand, and glass fibers in place of coarse aggregate, resulting in a product that's only about a third of the weight of conventional precast concrete. "GFRC is better for the installer. It's lighter and easier to cut and less susceptible to chipping and breaking. GFRC can also be used for structural elements, and no rebar is needed because its compressive strength is more than twice that of regular concrete," says Tommy Cook of Absolute ConcreteWorks (ACW).
In addition to being easier to work with, GFRC can be cast into ornate shapes with a high degree of detail. GFRC can mimic the look of terra cotta, carved stone and even cast-iron building elements. Typical architectural applications include spandrels, column covers, cornices, brackets, quoins, railings, pilasters, copings and trim.
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