Solve the problem of water vapour in concrete slabs causing vinyl or resin flooring failure by using Koster VAP I 2000. This proven vapour barrier system can be applied to new build or existing concrete and will stop moisture from permeating through the concrete and compromising the flooring, thus preventing the need for costly remedial work.
The Koster Water Vapour Control System (Koster VAP I 2000) was successfully introduced to the American Market in 1992 and has an impressive track record with thousands of satisfied customers including The Pentagon, where the system was installed as a vapour barrier on the concrete floors in the hallways, offices and washrooms.
Flooring failures due to water vapour in concrete floor slabs have been plaguing the construction industry for decades, causing millions of pounds worth of damage. Typical damage patterns (indicating a serious failure of the flooring system) can be blisters in epoxy coatings, bubbles in sheet flooring, unsightly staining at seams, adhesive bond failure, loose, curling and cracking VCT (vinyl composite tile), warped wood floors and damp and mould infested carpets.
Water is present in the ground almost everywhere, as moisture or in liquid form as ground water. A concrete floor slab or basement slab can come into contact with water where it is immersed, or merely in contact with moist ground. Moisture can originate from a lower laying ground water table rising in the ground due to capillary action.
When a concrete slab is in direct contact with the moisture in the ground, capillary action transports that moisture into the concrete. Water that is present in the ground can also turn into water vapour and rise through the ground until it comes into contact with the bottom of a concrete slab into which it can then penetrate.
Water is one of the key ingredients of concrete. At the time concrete is made, it contains liquid water. While part of that water is used up in the hydration process, another part of it remains in the concrete and evapourates over time. The more water that is added into concrete at the time it is produced or during curing, the longer it is going to take to dry to a level that is acceptable for a flooring system . In fast track construction programs this can lead to expensive delays. Air conditioning systems de-humidify the air in buildings. Since vapour will move from an area of
high concentration to an area of low concentration, a stream of water vapour from the floor slab into the air is set in motion. Water vapour readings should always be taken at a time when the heating, ventilation and air-conditioning systems (HVAC) have been turned on in order to assess the vapour drive of the building under normal use. Further sources of water can be broken pipes under a slab, spills onto concrete, building use such as kitchens or washroom areas, cleaning and maintenance, rain and snow, ambient relative humidity and condensate forming on the concrete due to condensation.
As long as the water vapour can simply pass through the concrete, it does not do much harm although it can act as a transport mechanism for salts of various types causing efflorescence on the surface of the concrete.
When a flooring system is installed, it typically has lower vapour permeability than concrete. The water vapour can no longer pass through the concrete due to the installation of the flooring system. As a result the amount of water vapour that is present in the slab will slowly rise. This can be measured as an increase in the relative humidity in the concrete. Wood floors can expand and buckle when exposed to moisture over a period of time. Also, microbial growth can develop under floor coverings leading to health hazards for the occupants. Various coatings and adhesives will de-bond when the moisture level underneath the impermeable flooring becomes too high. In cases where different patching compounds have been used on top of each other underneath a vapour tight floor covering, they can react with each other in the presence of accumulated moisture. If concrete contains aggregate that is susceptible to Alkali Silica Reaction (ASR), the moisture now present in concrete can cause this to start, leading to the destruction of the concrete. Also, in old concrete which is already affected by carbonation, moisture can cause reinforcement steel that has been embedded in the concrete to start corroding.
Once the relative humidity at the surface of a concrete slab becomes high, temperatures below the dew point of water in the surface area will cause condensation within the surface layer. Such temperature regimes can be caused by the operation of air conditioning systems. Now the pores of the concrete below the surface are saturated with water. Adhesives that bond floor coverings to the concrete can degrade and fail as a result of the high pH and moisture present in the concrete. The high alkalinity that develops in the surface of the concrete due to moisture can also discolour floor coverings. Cured concrete contains soluble salts of calcium, potassium and sodium. In contact with water, these salts form hydroxides. Once dissolved in water, high alkaline conditions develop with pH readings up to 14. Potassium hydroxide in particular is known to be very aggressive against mineral building materials such as silica sands.
Once a highly alkaline condensation layer has developed underneath the surface of a tightly adhered vapour tight floor covering, the primer and the adhesive are directly exposed to this. This is the prerequisite for the formation of liquid filled blisters, which are frequently observed as part of a failure of a flooring system. Such blisters are often referred to as �osmotic blisters� although osmosis as a damage mechanism is much debated in the scientific community. Typically with this type of damage mechanism it will usually takes 3 to 6 months for coatings to delaminate. The exact time frame in which this delamination takes place depends on the level of vapour drive and the composition of the coating as well as that of the concrete. The liquid in blisters can have a pH of 14.