Innovative concrete coring, sawing and scanning expert, QA Coring,has become the first company in South Africa to successfully drill through three concrete bridges with such pinpoint accuracy, that the bridges can now be linked together by contractors using reinforcing steel bars.

The five weekproject, which formed part of the Gauteng Freeway Improvement Project (GFIP), was completed by QA Coring in August 2011 and involved the drilling of 560 holes– each measuring 32mm in diameter and 2m in depth – into the bridges along the Rietfontein Interchange where the R21 and N12 freeways cross.

QA Coring managing director, HenryDippenaar, believes that the company was able to complete the project on time and within budget by making use of custom-designed core barrels supplied by Diamond Products.
Due to the overwhelming complexity of the project,which involved drilling the holes at angles between 23 and 30 degrees, QA Coring required a range of barrels measuring up to 3 m in length. Diamond Products director, DarrylGray, points out that the company supplied several barrels to QA Coring in a variety of lengths ranging between 450mm and 3m.

“The custom-built core barrels consisted of hollow 40mm diameter steel tubes that were fitted with diamond segments atthe front cutting edge of the tool; thereby, enabling the barrels to drill neatly through the concrete when rotated using the Hilti DC 350 and DC 200 electric diamond core drilling machines, which feed water through the centre of core barrel,” he explains.

Dippenaar notes that QA Coring accurately drilled the required amount of holes without any major setbacks, which will ultimately enable the contractor to link the bridges by splicing the reinforcing steel bars; allowing for increased strength to evenly distribute the weight of the vehicles that will be moving over the bridge. He admitsthat the unusual drilling angle resulted in an increased amount of wear on the core barrels; but highlights the fact that Diamond Products remained committed to replacing and re-tipping the diamond segments on a regular basis throughout the project.

“During the drilling process, we had to use the deck of the bridge to anchor the drill, and then swing the drill stand, in order to get it to the required angle of between 23 and 30 degrees. Diamond Products provided us with unrivalled after-sales support during this process, and experts from the company were available to service our requests when we required them. What’s more, the quality of the Diamond Products range of core barrels proved to be more durable and reliable than other products available in the local market,” he maintains.