In the field of construction and particularly in civil engineering, organic materials are essentially perceived as bonding additives. Whether we are talking about bitumens for road surfacing, polymers for formulating products for repair and structural gluing or admixtures for a more compact concrete, all these products are intended for realizations where we want to ensure the cohesion of granular groups.
This is in fact the primary role assigned to this class of materials, but we must not forget that there are other fields where plastic materials have been developed successfully, particularly sealing, environmental protection and engineering geology in general.
Here, we enter into the field of manufactured products where the term “organic material” takes on its fullest meaning. We may also note in passing that industrial wood, the discovery of which is of course not recent, but whose industrial development is changing rapidly, falls under this second category.
The presentation of organic materials used in civil engineering therefore compels us to study these two aspects in depth. As such, we will deal with these in the first few chapters, but we will not place our main focus on them, as our study is based on a physico-chemical approach, as suggested by the subtitle of this book.
This point calls for a few explanations. In a construction project, the designer expects from the materials that he intends to use a set of properties, in particular: − mechanical properties, such as a certain compressive strength for the realization of a load-bearing unit, bending strength and therefore tensile strength for a structure that must present a certain flexibility, resistance to impact or other types of aggressions;
− physical properties, if necessary, with respect to water or gas-tightness; sound insulation, for instance;
− aesthetic or more generally sensorial properties, in order to better meet the aspirations of the project owner and future owners;
− practical properties, as regards their handling or their use in general.
All this is part of the art of the engineer and the architect, but also implies requirements in terms of the minimal durability of all the above properties as well as in terms of the waste management at the end-of-life of the materials used.
These two aspects deserve particular attention insofar as they are today as important as the requirements in terms of mechanical strength. Man in the 21st century must know that he is not building for eternity and that his project must take into account the service life that he requires from the builder.
It follows logically that he is compelled to comply with, willy-nilly, health and environmental requirements imposed on him to preserve the living environment of the community. The durability of a material structure brings into play the nature of the materials that constitute it.
The manner in which they are arranged with respect to each other, the manner in which they are assembled, and their potential evolution within the structure, without forgetting the conditions under which they are placed. We thus enter the physico-chemical field: the evolution of a material under static or dynamic stress depends on its structure and its composition.
The knowledge of these data and the laws that govern them is fundamental for anyone interested in the durability of structures and buildings. In some cases, this can even be a decisive criterion in the choice of materials.
We must therefore never neglect the physico-chemical aspect in all the operations that involve materials. Even in cases where it might not seem useful to us, it is a precaution that can prove invaluable in responding efficiently in the event of an unfortunate development.