September 2012 Rapid RH Newsletter – Silicates: Friend or Foe?
When Admixtures Turn Us Into Chemists
Admixture (definition): ingredients (other than water, aggregate, hydraulic cement and fiber reinforcement) added to a batch of concrete or mortar before or during its mixing.
The world of building and technology collide with the evolution of concrete admixture. This is due to the rise of chemical admixtures, those compounds which produce a chemical reaction with the components inside concrete slabs. The installer’s goal is to produce high-quality concrete with lower setting times. However, the chemical reaction is a chemist’s world. Admixtures play an increasingly prominent role in concrete installation, and that makes chemists out of building contractors…
Tracing Moisture Problems to Source
Among many safeguards, ASTM International (formerly the American Society for Testing and Materials) has established standard ASTM F2170 for the use of in situ probes to measure concrete moisture content. However, F2170 recognizes relative humidity (RH) measurement as the standard for determining concrete moisture content in slabs.
When concrete moisture appears, the age-old building conundrum emerges: “where did that come from?..”
Forum Post: Calcium Carbide testing and Silicates
I have a project were Calcium Carbide testing is being used to attempt to show the performance of a topical silicate.
Is the test capable of determining Moisture Content (of the sample) once the concrete is contaminated with a silicate? I believe the surface test sample has the highest concentration of the silicate which may be altering the results.
I believe the test only shows the MC of the surface at best and has no way of determining to moisture reservoir that will ultimately make it’s way to the surface where it will over time affect an adhesive.
The job is in the USA but the product linoleum is made in Europe by Armstrong.
The adhesive Mapei Ultra-Bond G 21 2 part Urethane only references 2170 or 1869. 75 % and 5 lb .
The opposing consultant position is that the Calcium Carbide test is a valid test showing a dry condition.
My F- 2420 Dome testing reading which started out at 52% increased to 85% (a gain of 33% ) after only 5 days. Ambient conditions were under permanent house HVAC of 70 f and 40 % ambient. I did not flush the domes with Nitrogen. I have Wagner reading averaging 89 % and CC readings of 5.4 lbs.
I say the Silicate is NOT working. What say you?
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