The urban heat island effect on frost damage of natural building stones.

Daphne Guilbert,Tim De Kock,Steven Caluwaerts,Nathan Van Den Bossche,Klaas Calle,Veerle Cnudde

doi:10.1051/matecconf/201928202086

Abstract

Climate plays a major role in the weathering of building stones. This study specifically investigates the influence of the urban heat island (UHI) in Ghent, Belgium, on freeze-thaw (F-T) weathering of natural building stones and their hydrophobic equivalent. Climatic analysis of data of two places in and around Ghent indicates higher temperatures and lower wind speeds in the city center. This leads to a reduced number of F-T cycles and a lower wind-driven load. Hygrothermal modelling of a natural building stone, Savonnières limestone, is performed for the urban and rural climate of Ghent on the untreated limestone and on the treated limestone to assess the freeze-thaw risk inside these materials. Urban climate has a mitigating effect on the potential frost risk in natural building stones as a result of the urban heat island. Additionally, the application of a water repellent product reduces the potential frost risk even more, since the water density in the stone is reduced.

Highlights

Building stones are strongly susceptible to weathering, which is triggered to the prevailing climate and air pollution (e.g. [1,2])
Several weathering mechanisms are already studied in function of the climate and climate change
The urban heat island of Ghent is evaluated by the climatic analysis of the MOCCA climatic data of two locations in and around Ghent during the 2016-2017 winter (Table 1)

Summary

Introduction

Building stones are strongly susceptible to weathering, which is triggered to the prevailing climate and air pollution (e.g. [1,2]). Several weathering mechanisms are already studied in function of the climate and climate change. Bonazza et al [3] studied the impact of climate change of limestone surface recession, while Grossi et al [4] studied this climate change impact on salt weathering and Bonazza et al [5] studied the thermal stress on marbles. The influence of the climate change on freeze-thaw risk is studied by Grossi et al and Lisø et al [6,7]. Several methods are used to reduce wetting of wall assemblies by wind driven rain. A common method is the application of a water repellent layer on the pore walls of the outer layer of the wall assembly, which reduces the water absorption coefficient of the wall, without substantially changing the drying rate of the material

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Results

Conclusion