When it comes to waterproofing, there are a couple of issues in particular,
that more often than not, has a negative impact on construction programs
and the quality of the installation; wet concrete or masonry substrates and
a sometimes-accompanying high internal relative humidity and high moisture
vapour emission rates (MVER). It is important that contractors understand the
differences between the two moisture vapour issues to adequately mitigate
any effects on the installation itself and time pressures of the project.
Water is an essential ingredient in the making of concrete and the use of
excess water to facilitate installation and exposure to additional environmental
water, at times needs to be quantified to avoid installation problems with
subsequent coatings or finishes. The relative humidity of the concrete is the
amount of moisture in vapour form contained in the concrete and the
moisture vapor emission rate is a measurement of the speed and amount
of water that is released from concrete slabs.
Where more precise humidity and moisture vapour emission information is
required, standards and industry recommend ASTM F2170 Standard Test
Method for Determining Relative Humidity in Concrete Floor Slabs Using
In-situ Probes or ASTM F1869 Standard Test Method for Measuring
Moisture Vapor Emission Rate of Concrete Subfloor Using Anhydrous
Calcium Chloride, to determine the current moisture vapour conditions.
ASTM F2170 Standard Test Method for Determining
Relative Humidity in Concrete Floor Slabs Using
In-situ Probes (Primary Method)
This method of testing involves placing probes into drilled holes into the
concrete and taking readings with a hygrometer. It is worth noting that this
method is only accurate to interior concrete slabs. Generally, results of 75%
RH or below are acceptable for most tile and stone application, however
anything higher above this will need further preventative steps before
installation begins.
ASTM F1869 Calcium Chloride (Standard Test Method
for Measuring Moisture Vapour Emission Rate of
Concrete Subfloors Using Anhydrous Calcium Chloride)
High MVER can be problematic to waterproof membranes. HYDRO BAN®,
when applied over concrete with a high RH and high MVER rates will likely
cause the membrane to blister and lead to delamination issues. As pictured
right, the installation of HYDRO BAN was over a substrate with high
moisture vapour, causing the membrane to blister and retard the curing
process. When using HYDRO BAN, maximum amount of moisture content
should not exceed 24g/m2/24Hrs per ASTM F-1869 or 75% relative
humidity as measured with moisture probes per ASTM 2170. In cases
where moisture content exceeds these requirements, the first option first
and foremost is to allow the slab to dry and reach the required parameters.
However, this is quite often the unfavourable option due to the time and
cost with projects coming to a halt. Therefore, the use of a LATICRETE
moisture vapour reduction product is advised to protect the membrane
from the high moisture content.
LATAPOXY® Moisture Shield, is a 2 component, roller applied epoxy coating
specifically designed to reduce moisture vapour emissions in concrete and
other substrates. The product is mixed on a 1:1 ratio, and rolls like
paint. HYDRO BAN should be applied within 24 hours of the Moisture
Shield drying. For more information and installation instructions for
LATAPOXY Moisture Shield, click here.
As well as substrate moisture, HYDRO BAN Slurry can also be used to
reduce negative hydrostatic pressure. This is a cement based, one
component, polymer fortified material that mixes with water and easily
applies with brush, roller or trowel. For more information on HYDRO BAN
Slurry and installation instructions, click here.
For more information on LATICRETE and Moisture Vapour Emission Rate
(MVER), Relative Humidity and Moisture Testing of Concrete,
see TDS -1166.
Contact LATICRETE for product details and procedures - call 1800 331 012 or email sales@laticrete.com.au
