Print Email Facebook Twitter On the necessity of new hydrophobic treatment after repointing of water repellent masonry Title On the necessity of new hydrophobic treatment after repointing of water repellent masonry Author Nijland, Timo G. (TNO) Lubelli, B. (TU Delft Heritage & Architecture) van Zundert, Kim (TNO) van Hunen, Michiel (Cultural Heritage Agency of the Netherlands) Date 2024 Abstract The impregnation of the exterior surface of a masonry wall with a water repellent is a common intervention in (historic) building renovation and maintenance. Such treatments, whilst degrading at the surface with time under influence of ultra violet light, remain effective below the surface several decades after their application. During renovation works of masonry previously treated with a water repellent, the question arises whether it is necessary to repeat the hydrophobic treatment of the entire masonry after repointing. Opposing opinions exist with this regard, but no research clearly supporting one or the other. This research investigates for the first time the effect of hydrophobic treatment when applied on previously treated and repointed masonry walls. Small masonry walls were subjected to rain periods in the laboratory and their water uptake and drying behaviour were studied. Moreover, this laboratory research was followed by 30 months of outdoor exposition of the masonry specimens. The following cases were considered: (1) wall treated with water repellent, (2) wall treated with water repellent, followed by repointing but without new water repellent treatment, (3) wall treated with water repellent, followed by repointing and retreatment. This was done for three different types of pointing mortar: ordinary Portland cement and natural hydraulic lime with standard sand, and natural hydraulic lime with sand with one grain size. The results show that, after prolonged rain periods, the water uptake by repointed but not retreated masonry is comparable to that of untreated, non-hydrophobic masonry, whereas drying is considerably slower. This leads to a high saturation degree in repointed but not retreated masonry, which, in turn, increases the risk of damage to the masonry by e.g. frost. Therefore, retreating repointed hydrophobic masonry should definitively be considered. Subject Absorption behaviorDrying behaviourHydrophobic treatmentMasonryPointing mortarRe-pointing To reference this document use: http://resolver.tudelft.nl/uuid:44c80a1d-ad64-4c88-992c-e6ec02cf71d4 DOI https://doi.org/10.1016/j.conbuildmat.2023.134732 ISSN 0950-0618 Source Construction and Building Materials, 411 Part of collection Institutional Repository Document type journal article Rights © 2024 Timo G. Nijland, B. Lubelli, Kim van Zundert, Michiel van Hunen Files PDF 1_s2.0_S0950061823044537_main.pdf 10.18 MB Close viewer /islandora/object/uuid:44c80a1d-ad64-4c88-992c-e6ec02cf71d4/datastream/OBJ/view