Heritage Testing Ltd has considerable expertise in the analysis of historic building materials, including hydraulic lime mortar, & building stone, for conservation & preservation purposes.
The use of lime binders and hydraulic lime for new build projects has also regained popularity as architects and engineers have become increasingly more aware of the benefits of these materials over cement-based binders.
Westminster Hall, Palace of Westminster was originally constructed in the 11th Century, mainly of Caen Stone, a fine grained Middle Jurassic limestone from Normandy. This limestone showed poor durability, and high susceptibility towards erosion and pollution damage.
Thus there has been a long history of regular restoration and repair using a wide variety of other limestones, many of which have themselves eroded. Continued modern repair has benefited from a scientific perspective re. identification of these stone types, their durability, and cause of decay.
Image on left shows a photomicrograph of a sample of Limestone, taken from one of the parapet walls of Westminster Hall during 2000. The image shows a well-sorted, medium to coarse grained, porous, Oolitic limestone; the ooliths are welded and cemented at points of contact by a fine, isopachous, fringe of calcite crystals (blue areas due to resin dye which has been used to impregnate the sample voids).
This suggests a likely source in the Middle Jurassic Lincolnshire Limestone quarries of the Stamford area in Lincolnshire; notably the Casterton quarries (now defunct) or Ketton quarries (still quarried) of that area.