[article]
| Titre : |
Moisture testing in below-grade concrete wastewater structures |
| Type de document : |
texte imprimé |
| Auteurs : |
R. A. Nixon, Auteur |
| Année de publication : |
2016 |
| Article en page(s) : |
p. 32-40 |
| Note générale : |
Bibliogr. |
| Langues : |
Américain (ame) |
| Catégories : |
Humidité -- Mesure
Humidité dans les constructions
Matériaux cimentaires -- Teneur en humidité
|
| Index. décimale : |
667.9 Revêtements et enduits |
| Résumé : |
When establishing the minimum conditions suitable for coating concrete, many coating manufacturers, and hence specifying engineers and contractors, rely on unrealistIc moisture content and moisture vapor emission rate (MVER) requirements. These compulsory values are founded on laboratory testing rather than field experience, or worse still, on supposition rooted in unachievable and unrelated requisites. Repeatability problems and margin-of-error concerns must be taken into account for these widely specified thresholds. Case histories demonstrate the inaccuracy and unsubstantiated reliance on these commonly used test methods. Coating failures can occur even when we meet the MVER target value and successful coating performance can occur when the specified target values are not achieved. Recommendations that establish some practical criterion for deciding when, and where, not to coat concrete must be considered.
The most commonly specified quantitative moisture-related test standards for coating concrete are ASTM F1869 and ASTM F2170 (Fig. 1). These standards are routinely listed in product data sheets and specifications without any qualification as to the type of structure to be coated. Floor slabs on-grade within office buildings are treated exactly the same as below-grade
wet wells in wastewater pump stations. For each test standard, manufacturers and engineers have generally adopted threshold values for deeming concrete suitable to be coated. For ASTM F1869, the target value is less than 3.0 ibs. of moisture per 1,000 square feet in 24 hours. This establishes an MVER. For ASTM F2170, the generally accepted maximum relative humidity (RH) for concrete is 80 percent. Scientifically derived data demonstrates that these threshold values are neither achievable nor realistic for below-grade structures. |
| Note de contenu : |
- Applicability
- Repeatibility and margin of error concerns
- Real-world case histories
- Consideration of qualitative moisture testing
- Practical recommendations |
| Permalink : |
https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=26191 |
in JOURNAL OF PROTECTIVE COATINGS & LININGS (JPCL) > Vol. 33, N° 4 (04/2016) . - p. 32-40
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