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Project Details

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Project Information Sheet 1999-22

Formation and remediation of pad marks on Indiana Limestone

Funding Source:	Indiana Geological Survey
Period of Contract:	15 Jun 2000
Status:	extended — Definition of status type
Project Director:	John R. Hill and Margaret Ennis

Issue

The fibrous material called homasote has been used for many years by the dimension limestone industry for padding between milled slabs of stone that are prepared for shipping to a job site. If allowed to remain in the open at a construction site, the surface of the stone in contact with the homosote pads may discolor as a result of chemical changes that occur beneath and adjacent to the limestone. The discoloration usually fades if the dimension stone is installed where it receives sunlight, but when applied to northern exposures, for example, the stone often retains the discoloration for periods as long as several years.

Objective

In this study, we tested a variety of padding materials to determine which produced the least discoloration on weathering.

Approach

Eighty-six slabs of milled limestone ashlar measuring 3 feet by 2 feet by 3 inches thick were stacked four deep on wooden pallets, as they would be for shipping. Various padding materials and moisture barriers were used to separate the stone ashlar specimens and the stone was inspected and photographed monthly to document discoloration. A recording rain gage was used to measure precipitation during the course of the experiment. In several cases, the pH of limestone dust used as a buffer was determined in situ. Several new methods for removing the pad marks will be tried at the end of the 4-month field study.

Products

A report was published of the results of this study; see J.R. Hill and M.V. Ennis, 2003, Formation and Remediation of Pad Marks on Indiana Limestone, Indiana Geological Survey Report of Progress 33.

Benefits

The dimension limestone industry in Indiana is the principal beneficiary of this work, but architects and users of Indiana Limestone will share in the value of this work.

Locations Affected:

Lawrence

Monroe

Indiana House Districts Affected:

60

62

65

Information Updated February 1, 2007

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