Following a request for a survey from an existing client London Quadrant Housing & Martin Arnold LLP - Prokol Polymers UK we were asked to specify a solution for a failing waterproofing membrane applied by another company after only 6 months into its service life.
The Client Brief
Prokol Polymers UK were asked to review a failing road membrane application applied by another well known manufacturer that was just 6 months into its service life. Water was still causing heavy structural damage to the underside of the concrete deck. Directly beneath the deck there is car park garage area used by the public.
The Initial Survey
After carrying out some destructive core sampling the physical specimen’s were submitted for tests to Prokol Polymers Holland commercial laboratories, using Bruker analytical equipment in conjunction with Opus Software (this test platform is supported by most of the key coating independent test houses around the world) we were able to understand why this existing application had failed and with the defined report it would allow the client to predict their next move forward.
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.
Prokol Polymers UK Engaged to Produce New Specification
Spray Applied CE Certified Hydrophobic Pure Polyurea 136T Seamless Membrane System
The new application would see the entire road wear course removed again causing disruption to occupants and services, so it was key that the new application was fast with minimal impact and would have a long term maintenance free service life.
Prokol Polymers UK specified a complete system of CE Certified Hydrophobic Pure Polyurea which was fully Hydrophobic with a fast chemical cure chemical cure (not catalyst) of 8 seconds closing any curing window immediately, Prokol Pure Polyurea is also moisture tolerant and can be applied to damp surfaces in conjunction with our primer systems, it will also cure at low minus degree temperatures. A Pure Polyurea based slow cure-bonding agent would then be applied with a broadcast of aggregate separate from the main membrane to give a bond to final hot roll road wear course. At aggregate stage the road could be used by heavy plant without damage to the membrane it could also have been left as the final wear course as the aggregate was highways approved but we decided to take a belt and braces approach to give the asset owner L&Q more confidence in the new application.
Hydrophobic Explained
The Work Begins
The road was closed and the existing road wear course was removed quickly, plants and trees from the communal grounds were also removed and stored ready for re-planting once reinstatement works commenced at the end of the project, Prokol Polymers UK approved applicators following the specification started works excavating the lowest points at the base of the garages where cleaning and captive blasting would prepare the concrete facades ready for the initial sealer primer phase.
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.
Once The Existing Road Membrane Was Removed Cleaning & Dust Free Captive Blasting Was Carried Out Along With Substrate Profiling.
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 concrete is fully prepared and checked by Prokol Polymers UK quality inspectors the next phase of primer sealer is ready for application.
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.
Final Calibrated Adhesion Testing Process Prior to Sign Off
Adhesion of the Prokol CE Certified Pure Polyurea is very high and bond strength is achieved per mm at around 8 to 9 mpa, no termination details are required, where the membrane stops is where the waterproofing begins.
Application Complete
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.
The communal gardens are growing nicely and are well established again
Prokol Summary
Prokol Polymers quality inspectors have monitored the underside of the road deck since its application in March 2010 annually and to date there is no water ingress at all. Prokol Polymers UK will continue to monitor its performance for the entire 30 years of the manufacturer warranty, when specified correctly & competantly these are the results.
- Total Application Area 6500m2
- Application Monitored Constantly by Prokol Polymers UK for Quality & Client Sign Off
- Total Project Cost of Road Membrane Application £197,784.89p
- Duration of Works 8 weeks (Including inclement weather issues)
- Zero Defects
- End of Defects March 2011
- 30 Year Manufacturer Warranty
- Application Performance Inspected Annually by Prokol Inspectors for 30 years.
Prokol Polymers are an ISO Registered Company
www.prokol.co.uk - info@prokol.co.uk