Colloidal silica versus vapour retarders

By Sheldon White

Colloidal silica post-placement pozzolan technology differs from vapour retarders or barriers. In this article, we will explain the difference between colloidal silica post-placement technology and vapour retarders or barriers. You will also learn that our colloidal silica post-placement pozzolan technology is effective with or without the use of water-vapour retarders or barriers.

Colloidal silica deployed successfully
Colloidal silica post-placement pozzolan technology has been deployed successfully on numerous projects where vapour barriers were not specified by professional teams. Our colloidal silica post-placement pozzolan technology has provided excellent water-vapour protection for flooring, adhesives and coatings.

SCP is a pre-mixed, spray-applied treatment that penetrates into Portland cement concrete substrates at the time of placement. It provides permanent concrete protection and waterproofing from the inside out, leaving no surface residue. At the same time, it facilitates optimal conditions for concrete curing and flooring applications.

Colloidal silica – effective moisture-management system
Colloidal silica post-placement technology stops water vapour that originates from the concrete slab itself. Alternatively, vapour retarders or barriers have only been designed to minimise the transmission of water vapour through a concrete slab from sources below. They do not stop water vapour that originates from the concrete slab itself.

At present, there is no formal definition of the difference between vapour retarders and barriers that has been accepted by industry. According to ASTM E1745, however, both vapour retarders and barriers must not exceed 0,1 perms. The American Society for Testing and Materials E1745 is the Standard Specification for Plastic Water Vapour Retarders Used in Contact with Soil or Granular Fill under Concrete Slabs. This standard requires products undergo conditioning testing designed to simulate in-service (under-slab and installation conditions), and it classifies vapour retarders based on their tensile strength, puncture resistance and water-vapour permeance ratings. A perm rating is a standard measure of the water vapour permeability of a material. The higher the number, the more readily water vapour can diffuse through the material.

Colloidal silica overcomes typical challenges
Colloidal silica post-placement pozzolan technology overcomes many of the challenges encountered with water vapour barriers and retarders.

The location of the vapour barriers has been an ongoing debate for built environment professionals. Curling and shrinkage can occur when vapour barriers have been placed within direct contact of the bottom of the slab. To offset these problems, a layer of sand is commonly placed between the vapour barrier and the bottom of the concrete slab. However, this layer can provide access to moisture from the outside to the bottom of the slab. This can lead to problems associated with water-vapour transmission, potentially delaying your projects.

Colloidal silica fast-tracks projects
Colloidal silica post-placement pozzolan products reduce water-vapour transmission. This is to the point where the performance of moisture-sensitive flooring, adhesives and coatings are not affected after 14 days of treatment of the concrete slab with SCP.

However, an effective plan to address moisture transmission through cracks and joints should always accompany the design of moisture-sensitive concrete slabs. This is even though colloidal silica post-placement pozzolan technology is always effective whether or not a vapour barrier has been specified.

Spraylock Africa recommends that project design teams consider their local codes and intended performance of the proposed vapour barrier before deciding to replace it with our technology.

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