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Deutsche Bauchemie e.V.

Chemistry in Civil Engineering

Whoever thinks of buildings, streets and bridges will certainly have pure physics on their mind: Structures must be solidly built, statically stable and able to withstand tensile stress and compressive forces. By following the laws of static engineering mechanics and strength theory, engineers design and build our infrastructure. The ultimate objectives are the usability, safety and durability of the structures.

For more than 10,000 years, however, man has not just used the building materials mother nature put at our disposal. New building materials have been created and existing ones are altered systematically. Chemistry is the discipline which deals with forming new substances from different basic materials. For this reason it can be said that chemistry is inextricably linked with civil engineering - although this link is not as obvious as that to physics.

Most building materials that are used for erecting a new building are man-made or artificial:

  • To produce cement limestone and clay are made to react at high temperatures. The individual elements Ca, Si, O, Al, Fe rearrange themselves to form reactive cement. When mixed with water this cement will harden to become hydrated or hardened cement. 

  • In the production of concrete grit or stone particles as well as water are added to cement. In order to make the properties of concrete, e.g. its flowability or hardening speed, meet the special requirements of a building project, concrete additives are used. These additives also use chemical processes to change first the fresh concrete and later on the solid concrete.

  • Lime mortar or cement mortar - often used as tile adhesives, floor fillers or plaster in the construction of interiors and the making of facades - are also the result of chemical reactions.

  • The most different types of engineering Plastics are used in the construction industry as well. Concrete components, floors, roofs and facades are sealed or soundproofed to protect them from damages.

  • Wood cannot become a long-lasting building material unless wood preservatives are used to protect the building components against pest infestation. And also flame inhibitors that make wood and woodworking materials flame resistant cannot dispense with chemical substances.

The life cycles of all buildings are limited irrespective of the diligence and precautions that were applied during their erection. Manifold environmental influences act upon buildings and are likely to damage their structure. Hereby not only mechanical stress (e.g. a high traffic volume) plays an important role but also chemical deterioration mechanisms. Due to the chemical reaction of alkaline concrete and carbon dioxide from the air, for example, the building material carbonates, its ph-value decreases and steel that is embedded in the concrete may corrode. Penetrating moisture and salts can trigger various deterioration mechanisms such as the efflorescence of salts which has a considerable blast effect, the conversion of beta phases into weaker substances or the corrosion of structural steel. In addition to this, component damages often result from chemical reactions that modify the original material and thereby strongly affect the strength of a structure or its aesthetic value.

To enable useful counteracting the damaging mechanisms have to be recognized first. After this identification process, effective countermeasures can be developed. Corrosion prevention not only has to consider the mechanical stress buildings are exposed to but also the chemical impact on buildings and structures.

Damaged structures can often be rescued by restoration and renovation. For these purposes the building industry knows a range of products that is equally large as that available for the construction of new buildings.

An important aspect that goes beyond the purely functional aspect of construction chemistry is the interaction of construction chemical products with people, their health and the environment. A responsible use of the applied materials and additives means that the effects of these substances after the initial construction period are taken into consideration.

  • What can be done to optimise the total energy balance in the production of these materials?
  • How can an optimum recycling rate be guaranteed?
  • How can we make products that contain substances with the least possible health and environmental risk?

Building without chemistry is not feasible. The better we understand the chemical processes involved, the clearer we can target at influencing them and the better and the more durable the results will be. This is the reason why it makes sense for all architects and civil engineers to concern themselves with the chemistry of building materials.