Clay barriers for protecting historic buildings from ground moisture intrusion

Abstract

Background: Conservators and architects working with built heritage at risk from ground moisture intrusion face a difficult choice. Leaving the building unprotected can lead to moisture related deterioration; installing vertical and/ or horizontal barriers using standard materials requires chemical or mechanical intervention with the historic fabric. The use of compacted clay to form a barrier is commonplace in some areas of environmental engineering, and can be applied to built heritage conservation. Naturally occurring or slightly modified soils were traditionally used for protecting buildings in a number of vernacular techniques. Knowledge of what types of soils are suitable for use could provide certain regions with a low-cost, low-impact alternative for protecting historic buildings. Three commercially available products previously shown to have low hydraulic conductivity were analysed in order to identify waterproofing mechanisms; these included two specialised bentonite-sand mixtures and a Saxonian glacial till. Results:The till relies on a high proportion of densely agglomerated fine grains to achieve a low permeability when consolidated, possibly assisted by the presence of calcite. The specialised mixtures rely on an engineered grain size distribution, with practically no silt sized grains, and a fraction of sodium bentonites capable of forming colloidal suspension when compacted. All materials showed a low risk of shrinkage when compacted at optimum moisture content. Conclusion:Different mechanisms appear to account for the low hydraulic conductivities found in clay barrier material. The implication is that a range of soil material may be suitable for protecting built heritage from ground moisture intrusion and its associated decay mechanisms. The suitability of glacial till may present large areas of Northern Europe with locally available barrier material.

Intercalation and calcination as methods to reduce expansive soil properties

“…Various efforts have been made to reduce the potential swelling-shrinking properties of soil. Efforts often used include the use of organic matter (Hidalgo et al, 2019) and lime (Khadka et al, 2020), building structures to retain fluctuation groundwater (Michette et al, 2017), mixing soil with sand (Sholeh, 2012), and soil compaction (Zhao et al, 2014). Most of these efforts focus on maintaining the water content so as not to experience large fluctuations or to increase the bonds between soil aggregates.…”

Grain Size Analysis and Permeametry for Estimating Hydraulic Conductivity in Engineered Porous Media

“…Some engineering applications, in which the grain shape and packing can be highly controlled, have found grain size analyses to be of value (Aubertin et al ; Mondal ; Henderson ; Côté et al ; Scannell ; Choo et al ). However, most of these studies, including many in the geotechnical literature, only report grain size K estimates for the purposes of relative comparisons, or comparisons between laboratory methods, and the absolute accuracy of the K values vis‐à‐vis field scale is not evaluated in detail (St. Marseille ; Rice ; Michette et al ).…”

Understanding the Role of Ca2+, Na+ on Swelling Behaviour of Natural Expansive Soils: A field Application Prespective

“…But the bentonite utilization is not economical where the degree of contamination is minor. Considering these factors, many researchers used natural and modi ed expansive soils as compacted clay liners(Daniel 1993;Wanigarathna et al 2012;Michette et al 2017) and achieved different success rates. In this connection, natural expansive soils (Fig.…”