Civil Engineering March 2022 | Vol 30 No 2

Civil Engineering March 2022 29 Q Q An additional waterproofing mem- brane was included below the bridge joint to drain water into the gutter system. Q Q A waterproofing membrane was installed between the top of the deck concrete and the bottom of the bitu- minous surfacing to keep salt water from the road from leaking through the deck slab. Q Q Galvanic anodes were installed in the pier seating beams, abutment seating platforms and deck, where joints were installed. This was done to control the electrochemical reaction leading to the corrosion of the reinforcement, a technique very rarely used on bridges in Africa. Q Q All parapet reinforcement was hot- dipped galvanised. Q Q All steel for the laminated elastomeric bearings and in the bridge joints was 3CR12. Q Q A specified construction sequence for placing the beams and casting the in-situ deck was followed during construction to limit the horizontal movements of the beams. The beams were required to reach a certain age before the deck was made continuous and a specific, optimised sequence for the order of the different span construction was specified. CONCLUSION The Omaruru River Bridge is situated in a location with extremely harsh environ- mental conditions and has suffered se- vere concrete damage and deterioration. It was found that the best repair solution would be a combination of demolishing and replacing the bridge deck and seating platforms and repairing less severely damaged areas. In addition, the points of water ingress through the deck had to be reduced. This was achieved by replacing the simply supported deck with a continuous deck to reduce the number of expansion joints and bearings used for the bridge. Additional measures to increase the durability of the structure were adopted in the design, such as installing cathodic protection for the reinforcement, applying waterproofing membranes in the deck and joints as well as optimising the construc- tion sequence for erecting the beams and casting the in-situ slab to limit the horizontal movements of the deck.  Figure 11 Original deck effect on piers – simply supported Figure 12 New deck effect on piers – continuous Figure 13 Placing of the beams on temporary supports