Smectites: The key to the cost overruns in the construction of the third set of locks of the Panama Canal

Abstract

The third set of locks of the Panama Canal is one the most impressive civil infrastructures in the world. Its construction, however, was delayed by two years incurring cost overruns in billions that were mainly related to the use of the local basalt as the raw material for concrete production. The rapid degradation during the construction of an apparent sound basalt resulted in the huge loss of fines during the manufacturing of concrete. In the rock, olivine and glass are, respectively, altered to iddingsite and palagonite that are mainly composed of smectites. Smectites are also found around plagioclase and pyroxene crystals and filling the dense network of micro- and nano-cracks. Moreover, these smectites are spatially interconnected, which is the key to explaining the unexpected behavior and the rapid degradation of the basalt. Such a rapid degradation of basic igneous rocks – exposed to the weather and then utilized as a construction material – is not frequent, yet it is significant enough to call for the development of a new standard for the use of these materials in construction.