A comparison of standard and realistic curing conditions of natural hydraulic lime repointing mortar for damp masonry: Impact on laboratory evaluation

Fusade, Lucie; Viles, Heather

doi:10.1016/j.culher.2018.11.011

Cited by 24 publications

(14 citation statements)

References 24 publications

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“…Previous drying tests have shown that mortars dried under such high humidity (15 °C, 85% RH) show a longer stage I drying [63]. This long stage I can also be seen in Fig.…”

Section: Discussionsupporting

confidence: 67%

Drying response of lime-mortar joints in granite masonry after an intense rainfall and after repointing

et al. 2019

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When rain impacts a building façade, it is essential that once it has entered, it leaves by evaporation to help the building dry out. Accumulation of moisture can lead to internal dampness, mould and decay of valuable masonry by salt weathering. In a solid masonry wall where the stone is of low permeability, such as granite which is found in many historic buildings, rain water mainly enters and leaves through mortar joints. If granite stone masonry needs repointing, the repair mortar must allow the overall masonry to dry out. This study evaluates the drying response of various lime-based repointing mortars mixes in small granite stone masonry constructions (test walls) subjected to a simulated intense short rain event and then left to dry. It determines the moisture movement through mortar joints, the influence of materials, joint types and workmanship, and whether repointing could mitigate moisture ingress and help masonry dry out. This study developed a novel experimental protocol which allowed comparison of the drying response of different mortar types in a low-porosity stone masonry system and the effect of repointing. Five test walls were built of Cornish granite with five different lime mortar mixes combining NHL 3.5 (St Astier) gauged with non-hydraulic quicklime (Shap), quartz and calcitic sand and biomass wood ash as additives. Simulated intense rain was sprayed on each wall over a 3.25 h spell. Drying was monitored over a week with a microwave moisture device (MOIST350B). Measurements were done at surface and depth on both mortar joints and granite units. Each wall was then repointed with the same mortar mix initially used when built and the same rain simulation was performed to evaluate differences repointing could make to the moisture dynamics. The importance of mortar in dealing with moisture movements in the test wall and absorbing moisture from the stones was demonstrated. Gauged binder and wood ash additives decreased the capillary absorption capacity of mortars while retaining a good drying rate. This study has also showed that after repointing water did not penetrate as deep under the same conditions. Therefore repointing reduces the threat of water ingress and shows that it could be a suitable conservation intervention to mitigate water ingress and accelerate drying.

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“…Previous drying tests have shown that mortars dried under such high humidity (15 °C, 85% RH) show a longer stage I drying [63]. This long stage I can also be seen in Fig.…”

Section: Discussionsupporting

confidence: 67%

Drying response of lime-mortar joints in granite masonry after an intense rainfall and after repointing

et al. 2019

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“…The hardening process time of hydraulic lime mortar is longer than that of Portland cement. In the literature [40,41], this process, and for lime mortars similar to those in this study, was established at around 90 days. For an adequate organization of the experimental tests, 84 days was established as the hardening process time for the specimens of this study.…”

Section: Compressive Strength Of Thin-tile Masonrysupporting

confidence: 54%

Experimental Behavior of Thin-Tile Masonry under Uniaxial Compression. Multi-Leaf Case Study

et al. 2021

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In this study, experimental analysis on the compressive strength of multi-leaf thin-tile masonry is presented. A compressive strength test was carried out on thin-tile, mortar and 48 specimens with two- and three-leaf thin-tile masonry. The results obtained were compared with literature on brick masonry loaded parallel to a bed joint. Based on the results of this study, the failure mode presented the first crack in the vertical interface; this crack grew until the leaf was detached. From this point until collapse, lateral buckling of the leaves was generally observed. Therefore, the detachment compressive strength value was considered relevant. Up to this point, both masonries exhibit similar stress–strain behavior. The experimental values of the detachment compressive strength were compared with the values calculated from the equation generally used in the literature to evaluate the compressive strength of brick masonry. From the results obtained, the following conclusion can be drawn: This equation is only suitable for tree-leaf thin-tile masonry but with more relevant influence on the compressive strength of the mortar. This study concluded that only three-leaf specimens behave similarly to brick masonry loaded parallel to a bed joint. Finally, whether the failure mode was due to shear or tensile stresses in the vertical thin-tile-mortar interface cannot be identified.

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“…The general distribution of SH values at Reigate centres, putty edges and old edges, and their adjacent mortar joints reflects ambient conditions, with lower values recorded during the wetter, winter survey. The increase in NHL SH from November 2017 to August 2018 could reflect ongoing setting of the hydraulic binder [2]. The corresponding lower SH along NHL block edges may indicate a higher MC, resulting from the denser NHL performing a less effective poulticing.…”

Section: General Distributionmentioning

confidence: 99%

“…However, there are knowledge gaps and persistent misunderstandings as to their correct application, particularly on vulnerable masonry. Whilst the potential damage caused by excessively strong, hydraulic lime mortars is well documented, imprecise specification or product description often results in the use of material that may be unsuitable [1,2]. Furthermore, the properties of a non-hydraulic lime mortar are determined by a wide range of parameters during the production process, and there are ongoing concerns about…”

Section: Introductionmentioning

confidence: 99%

In Situ, Non-Destructive Testing for Evaluating the Role of Pointing Mortar in Preventive Conservation Strategies. A Case-Study on Reigate Stone at the Wardrobe Tower, Tower of London

et al. 2021

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The correct choice of pointing mortar is considered crucial to the conservation of historic masonry. A proliferation of cement and eminently hydraulic lime mortars since the late 19th century has accelerated the deterioration of built cultural heritage in many parts of the world. Whilst the use of softer, lime-based mortars in stone conservation is now common practice, their role in the overall conservation strategy of highly vulnerable building stones such as Reigate Stone requires assessment. In this paper non-destructive testing (NDT) is used across a two-year period to investigate the impact of different pointing mortar types in situ. NDT data on surface hardness and moisture are interpreted at different scales to assess moisture regulation of Reigate Stone masonry at the Wardrobe Tower, a ruined structure at the Tower of London, following repointing carried out in Spring 2017. Joints repointed using a hydraulic lime mortar (NHL3.5) are shown to regulate moisture in adjacent Reigate Stone blocks less well than those repointed using a lime putty mortar. However, despite an initially inappropriate recipe, older hydraulic lime mortars are in some instances shown to perform similarly to the lime putty mortar, suggesting that NHL can weather sympathetically. The results also indicate that, whilst pointing mortar type does play a role in the moisture regulation of individual stones, its effect is outweighed by both properties of the stone itself, such as strength and past decay, and by wider micro-contextual factors, such as exposure or adjacent topography. Findings from the Wardrobe Tower indicate that pointing mortar only plays a part in overall moisture regulation; to enable its effective functioning and minimise the need for repeated interventions, it may be necessary to take additional protective measures to mitigate moisture ingress, such as water run-off and channelling following heavy rainfall. The overall implication is that in vulnerable historic masonry such as Reigate Stone, sustainable conservation strategies must incorporate a broad appraisal of, and tailored response to, specific decay mechanisms. With careful calibration across repeated survey campaigns, data collected in situ using NDT can inform the role of pointing mortar within such strategies.

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A comparison of standard and realistic curing conditions of natural hydraulic lime repointing mortar for damp masonry: Impact on laboratory evaluation

Cited by 24 publications

References 24 publications

Drying response of lime-mortar joints in granite masonry after an intense rainfall and after repointing

Drying response of lime-mortar joints in granite masonry after an intense rainfall and after repointing

Experimental Behavior of Thin-Tile Masonry under Uniaxial Compression. Multi-Leaf Case Study

In Situ, Non-Destructive Testing for Evaluating the Role of Pointing Mortar in Preventive Conservation Strategies. A Case-Study on Reigate Stone at the Wardrobe Tower, Tower of London

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