Abstract
In 2010 burnt lime blocks were accidentally mixed with limestone concrete aggregates at a Belgian limestone and lime production plant. The contaminated limestone aggregates were used in precast concrete factories. The concrete elements used in several constructions quickly showed pop-outs, caused by swelling of lime nodules. The appearance of pop-outs in suspected constructions was recorded. An extensive experimental program as well as on site observations have been made, to monitor the evolution of the pop-out phenomenon with time. The pop-out evolution in outside exposure conditions is compared to the evolution of pop-outs under inside climatic conditions. Outside, the phenomenon becomes marginal after about 2 years. In inside exposure conditions, the phenomenon still continues after 7 years, be it at a low rate.
About the authors
Dionys Van Gemert, dr ir., is professor-emeritus of building materials science and renovation of constructions at the Department of Civil Engineering of KU Leuven, Belgium. He was head of the Building Materials and Construction Techniques Division, and head of the Reyntjens Laboratory for Materials Testing (1991-2008). His research concerns repairing and strengthening of constructions, deterioration and protection of building materials, concrete polymer composites. He was President of WTA International 1997-2001. He was President of ICPIC 2001-2007.
He is chairman of Triconsult n.v., spin-off of K.U.Leuven.
Luc Taerwe is a Senior Full professor of Structural Engineering at Ghent University and Director of the Magnel Lab for Concrete Research. Moreover he is an elected member of the Royal Belgian Academy of Technical Sciences and a High-End Foreign Expert at Tongji University (Shanghai, China). He is recipient of the “Robert L’Hermite Medal 1988” of RILEM and the IABSE Prize 1991, Fellow of the American Concrete Institute and the International Institute for FRP in Construction and also Honorary Life Member of fib. Since 2006 he serves as Editor-in-chief of the journal “Structural Concrete” and he is chairman of several national and international scientific and technical committees.
Kristof Verreydt is MSc in Civil Engineering Technology (KU Leuven, Sint-Katelijne-Waver, 2010), and PhD researcher at Leuven Arenberg Doctoral School for Science and Engineering (2014). He is project engineer at Triconsult nv since 2010.
Acknowledgements
The authors are thankful to the aggregate producer who provided the results of the confinement tests with hydrating lime nodules. Further thanks go to the concrete factory, for the sustained efforts in recording the pop-out evolution in the exposed outside elements. Also thanks to Ghent University, for providing the records of the yearly pop-out inspections in the student housing complex.
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