Author(s)

R. Brueckner & P. Lambert

Abstract

Construction methods and building materials have been in development since the dawn of civilisation. Simple timber and stone dwellings were followed by more modern construction methods such as fired clay and mortars with continual development until the present day. Early evidence of the use of concrete dates back at least 7,000 years and there has since been a continuous timeline, through the development of pozzolanic concrete by the Romans, to the first patent for Portland cement at the beginning of the 19th Century. Portland cement based concrete has undergone many developments based on field experience and extensive research to improve the performance of the resultant concrete, not always successfully. To reduce construction time, calcium chloride has been used as a set accelerator since 1873. This then state-of-the-art admixture has since caused significant damage due to chloride-induced corrosion of embedded reinforcement. Concretes based on other binders also appeared, such as high alumina cement (HAC) which was patented in 1908 but is now all but banned for structural use in many countries due to a number of high profile failures. This paper will discuss a number of once state-of-the-art building materials which may still be encountered in the renovation of heritage structures, and the methods and precautions required when carrying out remediation. Keywords: concrete, calcium chloride, high alumina cement, super-sulphated, asbestos, corrosion, repair. 1 Introduction Building materials have been appeared, developed and been replaced by innovations throughout millennia. The earliest development of concrete as a building material can be dated back to 5600 BC on the Balkan Peninsula. More widespread and considered use is recorded from 3000 BC onwards (Schaeffer [1]). In Egypt a mud consisting of lime and gypsum was employed which also

Keywords

concrete, calcium chloride, high alumina cement, super-sulphated, asbestos, corrosion, repair.