A platform for research: civil engineering, architecture and urbanism
A platform for research: civil engineering, architecture and urbanism
Environmental conditions can affect the curing and performance of lime mortars. Especially in the case of natural hydraulic lime (NHL) mortars to be used for repointing in exposed conditions, it is essential to assess what if any differences these environmental conditions would make to mortar properties through laboratory evaluations before repointing work begins. This study considers a specific historic environment: traditional masonry exposed to high humidity and rainfall, with a particular focus on Devon. Realistic curing conditions (as likely found on-site) of 15 °C, 85% RH, representing an average of summer climate in Devon were compared with standard recommended laboratory conditions of 20 °C, 65% RH. A range of mixes, representing some conservation pointing mortars, was prepared using NHL 2 (St Astier), quartz sand, and crushed Portland limestone in 1:3 and 1:2 binder to aggregate ratios. The influence of curing conditions on carbonation depth, strength development, internal textural structure, pore structure and water uptake at 28 and 90 days is discussed (called here early and medium ages) and the response of NHL mortars to this humid environment during evaporation and salt crystallisation have been assessed. Results show that significant differences are found in laboratory evaluations of mechanical properties of the same NHL mortar exposed to different curing conditions especially at an early age and for mortar made with quartz sand. Laboratory evaluation should be made on samples cured under realistic conditions if information on the early to medium-term (up to 90 days) characteristics of NHL mortar is required. Overall, realistic humid curing conditions help NHL mortars gain good internal structure more quickly, minimising the risk of early failure of pointing mortar exposed in a harsh humid environment.
Environmental conditions can affect the curing and performance of lime mortars. Especially in the case of natural hydraulic lime (NHL) mortars to be used for repointing in exposed conditions, it is essential to assess what if any differences these environmental conditions would make to mortar properties through laboratory evaluations before repointing work begins. This study considers a specific historic environment: traditional masonry exposed to high humidity and rainfall, with a particular focus on Devon. Realistic curing conditions (as likely found on-site) of 15 °C, 85% RH, representing an average of summer climate in Devon were compared with standard recommended laboratory conditions of 20 °C, 65% RH. A range of mixes, representing some conservation pointing mortars, was prepared using NHL 2 (St Astier), quartz sand, and crushed Portland limestone in 1:3 and 1:2 binder to aggregate ratios. The influence of curing conditions on carbonation depth, strength development, internal textural structure, pore structure and water uptake at 28 and 90 days is discussed (called here early and medium ages) and the response of NHL mortars to this humid environment during evaporation and salt crystallisation have been assessed. Results show that significant differences are found in laboratory evaluations of mechanical properties of the same NHL mortar exposed to different curing conditions especially at an early age and for mortar made with quartz sand. Laboratory evaluation should be made on samples cured under realistic conditions if information on the early to medium-term (up to 90 days) characteristics of NHL mortar is required. Overall, realistic humid curing conditions help NHL mortars gain good internal structure more quickly, minimising the risk of early failure of pointing mortar exposed in a harsh humid environment.
A comparison of standard and realistic curing conditions of natural hydraulic lime repointing mortar for damp masonry: Impact on laboratory evaluation
2018-12-07
Journal of Cultural Heritage (2018) (In press).
Article (Journal)
Electronic Resource
English
DDC:
690
| BASE | 2019
Structural Repointing of Masonry Structures
| British Library Conference Proceedings | 2019