Quantification of shrinkage microcracking in young mortar with fluorescence light microscopy and ESEM

In this paper a method is described to quantify shrinkage microcracking in young mortar by means of crack mapping. Visualisation of the microcracks is realised with two techniques: Fluorescence Light Microscopy (FLM) and Environmental Scanning Electron Microscopy (ESEM). The preliminary results obtained with the microcrack mapping method showed an increase in extent of shrinkage microcracking as a function of the hardening time of the young mortar, probably due to autogenous shrinkage. In the ESEM it was observed that microcracks in the young mortar open upon drying from relative humidities of about 25% to 1%. It is concluded in this paper that quantitative microcrack mapping at constant magnification should be done as a function of relative humidity of the sample and its environments.