LONDON UNDERGROUND
Managing water ingress in a reliable, safe and cost effective manner
Professor Denis Chamberlain, technical director at Epicuro Protective Materials, explains how to avoid the unnecessary use of costly and time-consuming waterproofi ng methods.
W
hat would be your answer to the question, “How many rivers does London have?”
Based on historical maps the correct answer, including so-called ‘lost rivers’, is approximately 285. In the evolution of this great city, these have become diverted or built over. Add to this the network of water supply and waste services and it is no wonder that water ingress is a major issue with tunnels, retaining walls, basements and car parks.
Water ingress is a common cause of deterioration in building materials, threatening both the integrity and ambiance of the affected asset. Remedial measures are frequently complicated by the occurrence of heritage masonry of high aesthetic value.
Its presence tells the story of London’s unique evolution. Under the action of seeping water, the natural mortar used in such masonry is prone to lime leaching, a process by which mortar’s lime content is transferred to the masonry surface. Whilst a reoccurring requirement for cleaning and repointing are indicated, prolonged periods of uncontrolled leaching result in hidden voids. Whilst underground masonry tends to be very substantial, extreme occurrences of leaching can have structural implications.
In the case of concrete structures underground, water transmitting defects include high porosity, cracks, joints and holes. This situation can be aggravated by expansive corrosion of embedded or compositely acting steel. As with leaking masonry, the ground formation to the exterior of the boundary envelope can be substantially disturbed by the continuing passage of water, especially in the case of clay and silt. Identifi cation of the source of water
98 | rail technology magazine Jun/Jul 14
can be diffi cult, if not impossible, on account of the hidden pathways thus formed between the water source and the water yielding defect.
Epicuro provides a high level of technical backup with its products, including on- site investigations to support ingress water remediation projects. An example of this is in its use of Lockin Infrared Thermography to help identify hidden water around a seepage point. This method takes advantage of the way that water affects the natural heating and cooling of surfaces.
Projects frequently include applications of Permbloc, a water-based crystallisation treatment that uses available moisture within the affected surface to reduce bulk permeability and fi ll small cracks. This is effective on both masonry and concrete, when used as part of Epicuro’s ‘Moisture Blocking Method’ (MBM). This avoids covering up aesthetically pleasing masonry with unsightly canopies. These make surfaces diffi cult to inspect and risk the concealment of destructive lime leaching.
Where coating or rendering is applicable, CemCrystal, a special cement-based coating with deep penetrating crystallation, can be part of the water remediation solution. A staged approach to installation allows even active water leaks to be addressed.
The core idea of the MBM is to control and manage water ingress in a reliable and cost- effective manner, avoiding unnecessary use of costly and time-consuming injected waterproofi ng, for example. Following removal of any surface contamination, an initial spray treatment clarifi es the often confused water ingress picture. Discrete water ingress points are thus distinguishable from general seepage
i.e. the treatment focuses water ingress. Water extraction can then be implemented using evaporation trays or site plumbing. Unwanted leakage points are addressed by localised injection of water proofi ng grout, for example. In the case of general seepage and damp conditions, the moisture blocker is applied suffi ciently to achieve dry conditions.
For successful outcomes, it is necessary to move beyond the notion of a product applied at a fi xed dosage. Skill and experience are demanded of those undertaking the work. For this reason, Epicuro operates an Approved Applicator scheme with certifi cated training for each product. We fi rmly believe that all manufacturers and suppliers have a responsibility to do all they can to safeguard the correct installation of their products, maximising the benefi ts with them. Technical support is also provided where monitoring of installation outcomes is required, including use of internet supported, surface mounted and embedded sensors.
In collaboration with our research partner, Brunel University, Epicuro is developing new materials, including ones that will reduce dependency on resins and cement. We are also one of the fi rst manufacturers to support the supply chain with electronically tagged packaging. As well as enabling transparency and auditability, it gives reality to the concept of ‘intelligent packaging’. On the environmental front, we are pioneers in our commitment to EN15804:2012, working to produce ‘Environmental Product Declaration’ statements for our products.
FOR MORE INFORMATION
T: 0207 125 0071 W:
www.epicuro.co.uk
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