Damage to cement concrete pavements due to exposure to organic compounds in a cold region

摘要

Pop-out and disaggregation of aggregate in a 1-year old cement concrete pavement originally mixed with air-entraining (AE) water-reducing agent was observed after the pavement had been exposed to ethylene glycol based snow-melting agent on the surface in the winter. The study used: gas chromatography-mass spectrometry (GC-MS) tests, ~1H Nuclear Magnetic Resonance (NMR) tests, X-ray fluorescence analysis, emission spectral analysis (ICP), elution tests in anion type surfactant solution conducted for mortar and aggregate taken from the cement concrete where pop-out had occurred, as well as samples made by cement paste in the laboratory. Tests of the tensile strength, thermal-stress, and three-dimensional crack analysis by micro-focus computerized tomography (CT) scanner were conducted for specimens (2.5 × 2.5 × 10 cm) taken from the cement concrete where pop-out had occurred and with cement concrete samples made in the laboratory. Microscope observations and Electron Probe Micro Analyzer (EPMA) analysis were conducted for thin samples (2.5 × 2.5 cm and 20 μm thick) taken from the cement concrete where pop-out had occurred. The tests results showed that organic compounds contained in the cement reacted with the cement during the hardening process, generating cracks and gel in the cement paste. It was established that these caused the pop-out of the aggregate, together with the effects of the ethylene glycol based snow-melting agent that the cement concrete had been exposed to. No pop-out or disaggregation of aggregate were found in cement concrete at a repaired section, at the same location, with aggregate of low absorbing water ratio in this cold region and in place for 2 years.