In-situ Evaluation of Long-Term Performance of CLT Panels in Below-Grade Applications: Mould Risk, Dimensional Stability, and Hygrothermal Responses
Notice bibliographique
Résumé
Reinforced concrete basements are the most popular solution in North American low-rise construction. However, cement and concrete production account for 5 to 8% of the global CO2 emission, corresponding to 3 to 6% of greenhouse gas emissions. Resilient and mechanically stable cross-laminated timber (CLT), a construction material for mid-rise buildings, is promising in basement construction. CLT panels have the potential to be more thermally efficient and offer better interior comfort than concrete wall basements. In addition, mass timber produces lower carbon emissions than concrete in the life cycle. However, research and applications of CLT panels in basement construction remain limited, leading to a knowledge gap in the in-situ performance of this innovative construction. The present study was developed as part of an extensive program to create the design concepts and methodology for constructing house basements using mass timber panels, focusing on CLT usage. A large-scale experiment was developed to assess the durability, deformation and thermal performance of using CLT panels in basement building construction. This research program investigated the mould growth risk, moisture content uptake, swelling and shrinkage coefficient and deformation modes, and the thermal performance CLT used as basement walls by monitoring a 6 m × 3 m basement in the field experiment constructed at the University of Alberta campus in Edmonton, Canada. An in-situ monitoring instrumentation program was established to measure the lateral earth pressure, CLT deflection, timber strain, soil temperature, soil moisture content, panel relative humidity and CLT panel temperature, and the program lasted for 24 months. In addition, a laboratory experiment was conducted to test the efficiency of a liquid waterproofing barrier in protecting the panels from moisture. A second laboratory experiment was conducted to calibrate the strain gauges in conditions similar to the filed construction and to derive shrinkage and swelling coefficients of a Spruce-Pine-Fir solid wood specimen to guide field testing determinations of these parameters. A mould growth risk assessment was conducted to evaluate the behaviour of the CLT panel under the below-grade environment throughout the year. The results indicated that the acceptable mould index of three was surpassed during periods of abundant water below the basement floor due to flood events, showing that the CLT panels were at risk of mould growth development. The average swelling and shrinkage coefficients calculated for CLT were around 2 times larger than the longitudinal and 20 times smaller than the transverse coefficients obtained from the laboratory experiment on solid wood specimens, indicating the effect of the cross-lamination on these coefficients. Cracks were the most visible in areas of the panel surface that presented knots and in the end-to-end joints of the panel lumber. Four deformation modes were observed according to the strain measurements and verified with the displacement measurements.The average heat loss per square meter calculated for the CLT basement wall was 0.793 W/m2, and the average cumulative heat loss for 720 days was 112.07 MJ/h/m2. The calculated thermal conductivity varied from 0.022 W/(m°C) to 0.363 W/(m°C). The average confirmed the value from the literature, 0.11 W/(m°C). This study explores a sustainable solution for concrete basements by proposing CLT as an alternative to enhance thermal efficiency and comfort in below-grade living spaces in cold climates. While research on CLT basement walls remains undeveloped, this is the first CLT basement to be reported, and this research may lead to a more sustainable approach to basement construction. This research aims to foster growth in the forestry industry and open new opportunities for CLT adoption in the Canadian housing market.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».