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Table 7 Measurements carried out on cubes before and during exposure trial

From: The design of a legacy indicator tool for measuring climate change related impacts on built heritage

Method and requirements Procedure Comment
Photography
  Digital colour photographs, of each exposed face Low tech, low cost; comparison will be visual
Average surface roughness (Ra)
 Diavite DH-6 or similar. Industry standard settings used = Lt 4.80 mm trace (sample length) and Lc 0.8 cut off filter (does not measure wavelengths >0.8 mm) The profile of the surface is measured using a stylus, magnified through software and quantified as roughness average (Ra) in µm, accurate to 0.01 mm Average from 10 profiles on each exposed face Highlights any changes in surface characteristics, e.g. smoothing or roughening Standard deviation in the Ra measurements can be used to indicate homogeneity of the surface
Colour meter
 Ultra Scan Pro USP1577 Hunter Lab. Mode #3 RSEX or similar Values for brightness (L*) redness (a+) and yellowness (b+) are taken. Average values are calculated from the five points by the Ultrascan Colorimetry has successfully been used as a measure of biomass on stone [10, 43]. Visual examination must accompany this assessment
Callipers
 Vernier callipers Digital Vernier callipers. Measurements taken in three dimensions (width, depth and height). Three measurements taken in each case Measurements accurate to ± 0.1 mm; quantifiable but of low accuracy
Weight
 Digital laboratory scales (measure to 0.00 g) Demounted stones (including internally fixed nut) weighed in grams. Stones must be dry before weighing The requirement for bringing the stones to a standard RH (approx 50–60 %) can delay this method of assessment for several weeks after demounting
3D profile scanning
 Renishaw Cyclone Series 2 SP600M machine or similar. Used Tracecut programme Profiling done in Z plane in increments of 5–10 mm (i.e. profiles taken at 45, 40, 35, 30, 20 and 10 mm from base). Profiles stored as DXF lines and arcs in CAD The CAD software will compare profiles over time, quantify change and can produce visual overlays that show the progression of loss
  1. CIE LAB system where L* can have a positive or negative value