Civil and industrial engineering building structures are subjected to various loading conditions during their service life. Besides permanent or frequently recurring actions, extraordinary stresses can occur. These can also include fire, for example. The behaviour of concrete in case of fire is principally characterized by the temperature-dependent change in the physical, chemical and mechanical behavior of its constitutive materials. This behaviour can cause impairment in load-bearing capacity right up to failure of the construction material and structure. This article is based on the results of current research into the action of polymer fibres in reducing concrete spalling. It summarizes important new knowledge as to how measures and optimizations in concrete technology can be employed to improve the fire resistance of concrete. This first part of the report at hand is concerned with the general aspects and action of fibres. The influence of cement type and aggregates will be dealt with in the second part of this article in CPI 1/2019.