Technical University of Lodz,
Keywords: innovative building materials
Summary:Innovative building materials should be characterized by a sufficient durability which is a key factor for possible recycling or reuse of building elements - a fundamental requirement for modern sustainable buildings. External surfaces of building structures are exposed to combined action of variable in time, climatic conditions and other physicochemical factors, which can reduce their durability due to materials’ deterioration and/or degradation of their service properties. The possible deterioration processes include frost damage due to cyclic water freezing – ice thawing, cracking due to repeating shrinking – swelling in variable hygrothermal conditions, and cracking caused by various chemical processes producing expansive phases, like: salt crystallization – dissolution, alkali silica reaction (ASR), concrete carbonation, delayed ettringite formation (DEF), among others. A deep understanding of the physical and chemical processes involved and causing these adverse effects is necessary to mitigate them, for example by creating innovative building materials with enhanced durability, thanks to creation of proper porosity microstructure. For this purpose, both standardized laboratory tests and more sophisticated methods can be used. They usually include experimental and theoretical analysis of the materials’ microstructure, deterioration of their physical properties (mechanical strength, elastic and plastic strains, thermal properties, air and water permeability), and resistance against various chemical agents (crystallizing/dissolving salts, leaching of chemicals by water, development of expanding chemical phases, etc.). In addition, mathematical models can be used for numerical assessment of a building envelope durability in various, ambient conditions. An application of the theoretical analysis and numerical modelling of concrete deterioration processes due to the frost-thaw action are discussed, as well as, salt crystallization and dissolution processes. In this work, the obtained theoretical results, which were verified by the experimental study performed with use of an original testing methodology. In addition, the research work considered a chemo-physical degradation of concretes, and novel concrete based composites, containing, for example, polymeric micro-spheres or super absorbent polymers added to the concrete mix. A correlation between the material deterioration and related changes of physical characteristics, like microstructure, strength properties, air and water permeability, are discussed as well.