Where areas to be inspected are hidden (e.g. bridge deck at abutment, or cavity wall) a mobile C.C.T.V. rig allows easy access. Images may be saved and replayed on video and captured as photographs

In many cases, visual inspection alone will not see areas of greatest degradation. In this assessment of parapet post corrosion, sealant at each post base was removed to assess 'hidden' corrosion. Spot removal of certain entire posts confirmed that corrosion was worst just behind the sealant

Where the integrity or durability of a material is in doubt, a visual survey is the first step in ascertaining the scale of the problem. Using modern software, colour categorisation of defects and mapping onto drawings will show the areas and extent of defects at a glance, without the need to read through lengthy reports. Visual inspection is augmented by the methods below;

Until recently, no successful non-destructive test method for timber had been developed. We are now pleased to conduct timber integrity testing, using the sibert digital microprobe.

Testing comprises the drilling of a nominal 1mm diameter hole through the timber section at constant pressure. Measurements of drill rotation and displacement are logged on a microprocessor, and can be plotted to show relative timber hardness (No. of rotations) with distance through the section (See below). A laptop is carried for onsite interpretation of results.

Chart showing results of timber hardness testing. Distance through the section is seen on the x-axis and hardness (as No. of rotations) on the y-axis. The blue line denotes timber hardness. Annual growth rings can clearly be seen. Troughs indicate soft spring growth, peaks indicate hard late growth. Degradation due to woodworm can be seen from 72mm onwards.

This method enables a vast amount of information to be gathered quickly and shown clearly.

Night concrete testing on a rail overbridge. PTS qualified staff, rail mounted trolley scaffold towers and hoists are available to facilitate easy access

Durability of concrete structures may be assessed as follows;

• Determination of probability of active corrosion of steel reinforcement. The electrical potential of reinforcing steel is measured using a copper/copper sulphate half-cell, as per ASTM C876-91.
• Depth of carbonation in the concrete is measured
• Chloride content of concrete may be checked at increasing depth. This will determine the presence of corrosive salts and whether they are inherent or have ingressed from an external source.
• Depth of concrete cover to reinforcement is measured using a covermeter, in accordance with BS1881: Part 204 : 1988. The depth of reinforcement may then be compared with the concentration of chloride and the depth of carbonation, in order to assess the cause and likelihood of corrosion.
• Resistivity of concrete is measured using the dram two probe method, to assess the likely rate of corrosion. A highly permeable concrete allows a greater corrosion rate and will show a low resistivity value.