Concrete Petrography is a forensic analytical technique developed over many years to help the construction industry diagnose the cause or causes of problems in old and new concrete structures. This presentation highlights the various techniques typically employed in concrete petrography and the specialized sample preparation required to undertake this work. It also demonstrates some examples of the features and conclusions which can be drawn from these investigations. Topics covered will include; macroscopic examinations, hardened air void analysis, water to cementitious ratio determination, degree of hydration, freeze thaw attack, alkali silica reaction, and various forms of sulfate attack. Examples demonstrating the cause(s) of low strength, surface scaling/delamination, set time problems and mix homogeneity will also be shown. Finally case studies are included in which the final conclusions drawn were not as obvious as might have initially been expected.
Dr. Ted Sibbick is currently a Principal Scientist with GCP Applied Technologies in Cambridge, MA. He has worked for 34 years in the Construction Industry working primarily on investigations of Concrete, Mortar, Aggregates, Cement Clinker and Cement, durability and long term performance by the use of microscopy and other analytical testing techniques. Prior to working at GCP Applied Technologies, Ted worked at the Transport Research Laboratory and Building Research Establishment in the UK where he specialized in studies of the alkali silica reaction (ASR), various forms of sulfate attack and other long term degradation related processes. His first degree was a Bachelor of Science (Hons) in Geology from the University of Derby and he subsequently obtained a PhD in Civil Engineering at Aston University in Birmingham, UK, where he was studying various aspects of the alkali silica reaction (ASR), the initial results of which led to further postdoctoral investigations. Ted has written over 50 papers and articles on the various topic listed above. He is an active member of ACI and ASTM C09.65 sub-committee which looks at on various aspects of concrete investigation methods. He is also presently the President of the Society of Concrete Petrographers.