The Existing Membrane Failure Results
From the analytical results the information showed that the existing membrane system was a cold applied Polyurethane based material that had curing conversion issues which could of be down to a number of reasons, application at the wrong time of year, weather condition or was applied by unskilled applicators causing error's when mixing the two part components, this would have played a key part in its failure.
Polyurethane Failure Explained
As cold applied liquid coating Polyurethanes are Hydrophilic (do not like water) and suffer from Hydrolysis Degradation (degrade when in contact with water) it is not an ideal product to use long term as it has an expiry date of life. Polyurethane based products use a catalyst to cure and as moisture sensitive species positive application must be done under controlled weather and air monitoring platforms with results recorded morning, midday and afternoon. Key monitoring during application of dew points, air temperatures, weather conditions to avoid moisture both in the substrate or air, as this will cause catalyst problems. For example 19 grams of moisture will destroy 200 grams of catalyst in the Polyurethane so for many reasons using or specifying it in the wrong circumstances can result in short service life and imminent failure, failure as seen here which occurred approximately 8 months into service it may have been sooner but was undetected. Another issue for the failure is long curing times especially at lower temperatures Polyurethanes will take hours if not days to cure and during the open cure periods whilst they are trying to convert & cure they will scavenge moisture either in the air or wetting from rain fall all of which will impede the overall performance and cause failure. Many Polyurethane systems require a reinforcing fleece or mat which will restricts any elongation properties in the membrane required for thermal or expansion movement, in fact your totally restricting the one key attribute in Polyurethane. On this project there were mechanical expansion joints in the road the existing membrane terminations were at the joint thresholds they then start again on the opposite side not encapsulating the joint to stop water ingress again the matt or fleece restricts its performance.
Removal of the Existing Failed Membrane & Road Surface
The previous structural waterproofing membrane had failed only months into service, with the manufacturer using clauses with the warranty to avoid costly rectification.
Surface Profile Complete Ready for the Next Stage
Preparation Phase Continued
Once the road concrete substrate had been prepared various repairs and edge detailing needed to be completed prior to the coating application phase commencing, all coating applications are 99% preparation dependent but unfortunately the previous application carried out did not apply the same specification or methodology in fact the analytical testing was confirmed once we started removing the road wear course. Expansion joints were serviced and chase channels cut ready to receive a new hypalon de-bonding strip, which would eventually be coated directly over. The 136T CE Certified Pure Polyurea has 330% elongation it will allow for full load deflection & constent movement when coated over the concrete slab de-bonding strip joints.
Once the lower deck area is sealed and fully waterproof it is independently holiday tested as part of the QA/QC plan to ensure the continuity of the coating membrane, when this test has been completed these areas are ready to be in filled and the gardens prepared for re-planting.
ELD Testing (Electronic Leak Detection) Was Carried Out Constantly to Ensure the New Membranes Integrity this was Monitored By an Independent NACE Coating Inspector
Communal Garden Areas Over Lower Level Garages are Now Back Filled
Next Phase Main Road Membrane Completion
The Prokol Primer sealer Profast R is applied to the road deck area by hand, the Profast primer is moisture tolerant and designed for damp mineral based surfaces with 5 - 10% moisture content. Prokol Polymers QA/QC process is followed strictly by the approved applicator & monitored by Prokol onsite quality managers, this includes calibrated substrate adhesion testing and recording as part of their daily QA/QC recording criteria. Once the primer sealer has cured (within 30 minutes) the next phase of spray applied CE Certified Pure Polyurea 136T membrane is completed to a dft. (dry film thickness) of 3 mm.
Once the Prokol CE Certified Hydrophobic Pure Polyurea had cured (8 seconds) the last phase could be applied, using Prokol Rocathaan PU 300-BA aggregate binder with 0.18 aggregate broadcast into the slow cure product this will provide a protective flexible wear course during the application of new hot tarmac to complete the application.