DEVELOPMENT AND UTILIZATION OF THE SALEM LIMESTONE(MISSISSIPPIAN) FROM THE INDIANA BUILDING-STONE DISTRICT. U.S.A

摘要

For more than 100 years, production of the Salem Limestone (Mississippian) from the Indiana building-stone district has exceeded production from all other dimension-limestone districts in the United States. The current producing outcrop belt is about 1.6 k (1 mile) wide and 48 k (30 miles) long and extends from Ramona, about 19 k (12 miles) northwest of Bloomington, at the north to Bedford at the south.The extended popularity of the Salem, known in the trade as Indiana Limestone, for dimension stone results from its adaptability to trends in architectural style and its proven durability. The stone is buff, gray, or variegated, is fine-grained, and is notably uniform in composition and texture. It is a freestone that can be quarried in massive ledges many kilometers thick without splitting. The physical properties when considered together are optimum for a dimension limestone and permit the Salem to be sawed, cut, and planed to exacting specifications for use in architectural styles from rustic fieldstone applications to elaborate Greek and Victorian styles. Moderate porosity (15 percent average) and permeability (50 millidarcies average) lead to the advantageous properties of ease of fabrication and breathing in place, that: is, the passage of water vapor out from within the wall. These same properties, however, require constraints in building design to prevent passage of water into the stone through soil, cement, or mortar. Water absorption can cause staining or disruption of the stone as a result of the freezing or depositing of salts.Quarrying and fabricating methods have evolved slowly through the years; current methods are a blend of both old and new. Advanced quarrying techniques, including wire, chain, and band sawing, have generally replaced channeling machines. Underground mining using a gallery saw, capable of horizontal as well as vertical cutting, was introduced into thedistrict in 1987. Improved fabrication techniques have produced lower costs in both quarries and mills as advanced technology has increased production efficiency. The resulting lower costs have stimulated a growth in demand for stone in construction. These factors, plus innovative installation techniques, have produced such engineering designs as floor-to-floor panel sizes with and without strongbacking, composite curtain-wall systems of stone, metal, and glass in unitized frames, multistone panels assembled with high-strength adhesives, and post-tensioned systems. The current architectural trend toward old-world architecture with massive arches and rusticated enclosures and, at the same time, a growing interest in renovation of and addition to historic buildings have created a resurgence of the Indiana limestone industry that is unparalleled in modern times.