The selection and design of the waterproofing system are paramount to the performance and durability of parking decks, says a.b.e. Construction Chemicals, which has supplied membranes and sealants for hundreds of such structures throughout South Africa.
a.b.e. is part of the CHRYSO Southern Africa Group.
Christopher Norbury, Technical Sales Consultant for a.b.e. in the Western Cape, says the installation quality of waterproofing membrane is vitally important because the integrity and continuity of the membrane determine the performance and durability of parking decks.
“Structural parking decks typically consist of reinforced concrete slabs over precast supporting units. Unlike covered structures, concrete parking decks are exposed to aggressive elements and prone to deterioration, such as spalling, scaling, cracking and delamination. The decks are also subjected to dynamic loading conditions and destructive chemical attacks.
“Parking decks are costly to build, repair and replace so water management is vital. Designing, installing, and then testing, waterproofing systems are the keys to divert water away from the structural elements. Water is the major cause of concrete deterioration and steel rusting and this is why a.b.e.’s protective waterproofing membranes are so widely used. Flood testing using ASTM D5957-98 ‘Standard Guide for Flood Testing Horizontal Waterproofing Installations’ is a good method to verify the waterproofing membrane,” Norbury states.
He says a.b.e.’s double-layer waterproofing system has proved particularly successful in wide-ranging applications. The system typically comprises of a.b.e.’s Index 4mm membrane followed by an Index 3mm membrane, laid with staggered side laps and end laps. The 4mm membrane is fully sealed by torch fusion to the primed substrate as well as the overlaying 3mm membrane.
a.b.e.’s popular Index range of membranes are elasto-plastomeric polymer-bitumen waterproofing membranes, manufactured from distilled bitumen, modified with elastomers and plastomers. The product is reinforced with a non-woven continuous extruded spun bond polyesterfabric, which is rot proof.
Norbury says for parking decks, the blacktop is often the cheapest wearing surface but in hot climates not always the best long-term solution. In such cases, other trafficable systems should be considered such as paving over a sand bed that includes a drainage layer – a more beneficial option in the long-term.
Other products supplied by a.b.e. for waterproofing parking decks include VIP QuickSeal, a polyurethane/polyurea product that provides flexible, seamless, hard-wearing protection. It is applied by a high-pressure rig, can cover 1 000m2 per day, and cures so rapidly that light traffic can be handled in under five minutes.
Jointing products include the renowned range of imported Dowsil silicone joint sealants (Dowsil DC 890SL, Dowsil DC888, and Dowsil DC813), and flexothane G and HS elastic polyurethane sealants, durakol GHM high modulus polysulphide sealants, and durasheet polyethylene semi-rigid joint fillers used for forming expansion joints or as backing material for joints. durajoint flexband, a high performance waterproofing bandage comprising thermoplastic elastomers is also frequently specified for decks.