Drying kinetics of building materials capillary moisture Nikos Karagiannis, Maria Karoglou, Asterios Bakolas ⇑ , Magdalini Krokida, Antonia Moropoulou School of Chemical Engineering, National Technical University of Athens, Zografou Campus, 15780 Athens, Greece highlights  The drying process of capillary absorbed water of building materials is examined.  The effect of several environmental factors on the drying kinetics is investigated.  A first order mathematical model is successfully applied.  Drying process depends on environmental conditions and on material characteristics. article info Article history: Received 19 September 2016 Received in revised form 24 December 2016 Accepted 25 January 2017 Keywords: Drying kinetics Building materials Mathematical modelling Capillarity abstract Drying of building materials capillary absorbed water is one of the main factors that determine buildings materials durability. Thus, the investigation of drying kinetics of capillary absorbed water can be very useful in understanding the causes of decay of building materials and in saving cost and improving the energy efficiency of constructions. In general, environmental conditions, such as air temperature, air velocity and air relative humidity, affect drying kinetics of various building materials. Most of the drying kinetics mathematical models use as initial moisture content the amount of water resulting by saturation of samples through immersion. In the present work, the drying process of capil- lary absorbed water, which describes more accurately materials behavior in buildings, was experimen- tally studied. An existing mathematical model was utilized. Several natural and artificial building materials were selected and examined (stones, clay bricks and natural hydraulic lime based mortars). The proposed mathematical model was found to fit successfully experimental drying kinetics data. Moreover, this model incorporated the environmental conditions, as well as the materials characteristics on the drying process. Thus, it can be applicable for use in building simulators concerning moisture trans- fer phenomena in building physics. Ó 2017 Elsevier Ltd. All rights reserved. 1. Introduction Moisture is one of the main decay factors in building materials. Water penetrates into a building material through capillary rise of ground moisture, rain and condensation of air humidity causing several physical, chemical and biological problems to buildings [1]. Rising damp is the most important and serious decay factor of a building material because it causes condensation in a building envelope and develops appropriate conditions for mold growth and harmful indoor air for occupants, affecting their health and their comfort [2–7]. Porous building materials have the ability to adsorb and desorb moisture with the variations of adjacent condi- tions. The durability of a building material is compromised when significant amount of moisture accumulates into it for a long time period [8] and the seriousness of the rising damp phenomenon is dependent upon a balance between the upwards flow of water drawn into the wall from the ground through the capillary rise and the water loss by evaporation from the masonry. The moisture content is not only determined by the water absorbed by the mate- rial, but also by the amount of water that evaporates, as described by the drying process [9]. Thus, drying of a building component is a crucial process because, in combination with wetting, it regulates the insulation of a building envelope controlling the energy effi- ciency of the structure [10–12], decreasing the cost of a construc- tion and affecting its life-time [13]. In general, drying is a three-dimensional heat and moisture transport problem and it depends on: [14]  The material properties (moisture storage and transport)  The climatic conditions (air velocity, temperature and relative humidity) http://dx.doi.org/10.1016/j.conbuildmat.2017.01.094 0950-0618/Ó 2017 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: abakolas@mail.ntua.gr (A. Bakolas). Construction and Building Materials 137 (2017) 441–449 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat