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Tue February 18 2020

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Cementitious coating passes 29-year test

26 Jan 18 Flexcrete’s Cementitious Coating 851 has received the thumbs up from scientists at the Vinci Construction Technology Centre in Bedfordshire, who have confirmed that it provides an effective barrier to chlorides for at least 29 years.

Chloride-affected concrete and a typical application for Cementitious Coating 851
Chloride-affected concrete and a typical application for Cementitious Coating 851

In 1988, a 2mm thick film of Cementitious Coating 851 was applied to a concrete slice and sealed in a chloride ion diffusion cell.

Independent tests carried out by the Vinci lab show that the barrier properties of 851 have not changed after 29 years (10,586 days).

Cementitious Coating 851 is two-component, waterborne cementitious modified polymer coating, providing structural protection against chloride attack. Originally introduced by Flexcrete Technologies back in 1985, it is also recognised in various overseas markets under the AkzoNobel brand name of Intercrete 4841. AkzoNobel acquired Flexcrete Technologies in 2017.

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Flexcrete co-founder Chris Lloyd said: “Cementitious Coating 851 has not shown any signs of deterioration despite being fully immersed in the chloride solution for over 29 years. In Vinci’s experience, many coating systems degrade over time when on test in the cell and even products that initially perform well can subsequently blister, resulting in more chloride ions passing through the product. The performance of Cementitious Coating 851 in this test is unparalleled.”

Following the latest studies in concrete technology, Vinci’s testing can determine a chloride ion diffusion coefficient from non-steady state conditions. Based on the total chloride quantity that has been determined to diffuse through the 851 coating during 29 years on test, it has been calculated that this equates to a chloride ion diffusion coefficient of 1.23x10-12 cm2/s. By comparison for the uncoated reference concrete specimen, a chloride ion diffusion coefficient of 1.03x10-8 cm2/s was calculated based on the total chloride quantity that had diffused in the first 98 days on test when steady state was achieved.

In other words, it would have taken 271 years for the product cell with Cementitious Coating 851 to reach the same chloride concentration that the uncoated specimen reached in just 98 days.

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