Abstract
Increased urbanisation will put an increasing strain on our green spaces, which is expected to have a significant effect on our physical and mental health, as well as the health of our ecosystems. As such it is important to integrate more green spaces in our urban fabric. One way of doing this is by making use of so-called bioreceptive concrete on our façades and other structures, which allows for biological growth to take place on the concrete substrate itself, without requiring any additional systems or maintenance. However, the challenge is to create an affordable concrete mixture that is sufficiently bioreceptive for biological growth to take place. As such, in our research we test four possible measures to make concrete more bioreceptive: changing the aggregate to CEC (crushed expanded clay), adding bone ash to the mixture, increasing the wcf (water cement factor) and using a surface retarder on the concrete. Of these measures, changing the aggregate to CEC (p = 0.024), the addition of bone ash (p = 0.022) and the use of a surface retarder (p < 0.001) were found to significantly increase bioreceptivity. Increasing the wcf factor, however, was not found to significantly increase bioreceptivity (p = 0.429). It was also found that whereas it was previously though a pH below 10 is necessary for biological growth to take place, this does not appear to be the case. Although further research under natural conditions is necessary, the creation of an inexpensive bioreceptive concrete looks to be feasible.
Highlights
By 2050 over 68% of the world population will live in urban areas, constituting an increase of 2.5 billion people to the worldwide urban population [1]
We will first discuss the effect the proposed measures have on the concrete characteristics that are expected to be important for bio receptivity: pH, surface roughness, capillary water content and capillary water retention
Whilst coverage data for the magnesium phosphate cement (MPC) samples was not available, from a visual inspection it is clear that the OPC samples showed significant biofilm development in most instances, whereas their MPC counterparts showed little to no development
Summary
By 2050 over 68% of the world population will live in urban areas, constituting an increase of 2.5 billion people to the worldwide urban population [1]. If no measures are taken, this increased urbanisation will likely lead to a further reduction of the amount of green areas in and around our cities This reduction in green spaces brings with it several problems, including but not limited to, a loss in biodiversity, heat stress, increased air pollution and more, bringing with them concerns for ecological and public physical and mental health [2,3,4]; McKinney, 2008). This means that the addition of extra green spaces in our cities is necessary in order to mitigate these problems. This means that these systems incur addi tional costs both in construction and maintenance, while they put higher structural demands on the buildings they are attached to Refs. [5, 6]
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