Walls overgrown with plants can have a positive impact on urban comfort and contribute to biodiversity in the city. In particular, quay walls, thanks to their close contact with water, have the potential to be ecologically engineered to encourage the growth of herbaceous plants. Different factors can affect growth of vegetation on walls. This research aims at experimentally investigating the effect of several variables, including quay wall design, building materials and environmental conditions, on receptivity of brick masonry quay walls for herbaceous plants. To this scope, ten quay walls (size 2 m × 2 m x 0.43 m), have been built and placed in a canal in the city of Breda (the Netherlands). The survival and growth of vegetation and the moisture content in the wall were monitored during a period of about 2 years. The results show that the presence of a layer of soil substrate with high capillary suction, positioned in between the masonry cladding and the concrete structure of the wall, has the most relevant positive effect on vegetation growth on the masonry. Mortar composition and irregularities of the wall surface influence bio-receptivity too, but to a less extent; orientation had only a limited effect. Moreover, the strategy of using a mechanically strong bedding mortar in combination with a weaker but more bio-receptive pointing mortar has proven successful at favouring growth of herbaceous plants, while providing sufficient strength to the masonry.@en

The effect of mortar and brick properties on the growth of ivy-leaved toadflax (Cymbalaria muralis) and yellow corydalis (Pseudofumaria lutea) has been investigated in laboratory. Different mortar compositions were designed and tested in combination with two different bricks. Highly porous bricks and mortars showed good bioreceptivity; mortars with lime-trass and, in lower extent, those with natural hydraulic lime binder, gave the best results in terms of bioreceptivity. The addition of vermiculite to the mortar was beneficial for plant growth. The brick-mortar combinations most favourable for plant growth were those with estimated low compressive and flexural bond strength values. Proposals are advanced for obtaining a compromise between mechanical strength and bioreceptivity.

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Aan de zuidwestzijde van de binnenstad van Breda ligt de deels gedempte rivier de Mark. Deze wordt de komende jaren uitgegraven en getransformeerd tot een blauwgroene ader: de Nieuwe Mark. De Nieuwe Mark moet straks de lokale ecologie verstevigen en het stedelijk klimaat verbeteren. Onderdeel van deze natuurinclusieve transformatie is het realiseren van met muurplanten begroeide kademuren. Wat daar technisch voor nodig is wordt momenteel onderzocht binnen het GreenQuays project.@en