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As the principal building material for landmarks from the ancient Great Pyramids to modern marvels like the Empire State Building, the enduring beauty and durability of limestone has reached across time and borders to preserve moments in history. Given its staying power, it’s no wonder that limestone is still the preferred choice for adding structure and elegance to commercial buildings and private residences.
But, despite its seeming universality, not all limestone is the same — and not every type is appropriate for every application. Before deciding on limestone for your project, it’s important to understand the various American Society for Testing and Materials (ASTM) limestone classifications that speak to how limestone stands up to its surroundings.
In the broadest sense, limestone is defined as sedimentary rock composed principally of calcium carbonate, the double carbonate of calcium and magnesium or a combination of the two minerals. Recrystallized, compact microcrystalline and travertine limestone are capable of being converted to dimensional stone — that is, natural stone that has been selected and finished to specific sizes and shapes.
While finishing characteristics like trimming, polishing, grinding, etc., are important, durability often trumps aesthetics for building projects, making density a priority. To that end, dimensional limestone is divided into three density sub-classifications based on approximate ranges, specifically:
- Low density: Limestone having a density ranging from 110 through 135 lb/ft3 (1760 through 2160 kg/m3); commonly known as Type I
- Medium density: Limestone having a density greater than 135 and not greater than 160 lb/ft3 (2160 through 2560 kg/m3); commonly known as Type II
- High density: Limestone have a density greater than 160 lb/ft3 (2560 kg/m3); commonly known as Type III
The Graphic Standards Guide to Architectural Finishes further delineates limestone by type:
- Oolitic limestone, like Indiana limestone, is particularly noncrystalline, consisting of calcite-cemented calcareous rock formed from precipitated lime, shell fragments and shells.
- Dolomitic limestone is somewhat crystalline and stronger than oolitic limestone. Dolomite is created when magnesium-bearing water, such as seawater, replaces the calcium in calcitic limestone with magnesium at any point during or after limestone formation.
Comparing densities alone, Type III Dolomitic Limestone is the standard bearer. It also outperforms lesser classifications in:
- Freeze-thaw durability as it loses no mass and is not unduly distressed when repeatedly frozen and thawed
- Longevity as it performs best in class in density (165 lbs./cu.ft.), compressive strength (15,000-32,600 psi), bending strength (1,669 psi) and abrasion resistance (18-29.75)
- Safety as it is naturally solar reflective and remains cool to the touch, keeping pool coping and pavers safe for bare skin. Plus, Type III Dolomitic Limestone boasts a 0.65-0.95 slip resistance — a particularly important safety measure in pool areas.
Eden Valders Stone quarries and manufactures Type III Dolomitic Limestone into a wide variety of architectural cut stone products including building elements, cladding and components that take any project to the next level. Click the button below to request free samples of this long-trusted and high quality building material.