New methodological approach for the mechanical testing of aerial lime-based binders and mortars: the effect of PEG-1000 addition

So far, the mechanical testing at the macro scale of aerial lime-based materials has mainly been focused on the analysis of mortars, while binder specimens have not been studied as much. In the present work an alternative, material-effective and low-waste methodology to evaluate the mechanical properties of aerial lime binders and mortars is proposed. The core of this methodology is based on specimen size reduction, minimizing quantities of material required during development and testing. In particular, the proposed methodology is aimed at studying the interaction of different quantities of a phase change material (PCM) with aerial lime binders and mortars. The mechanical properties of pure aerial lime binders were successfully characterized, whereas mortar specimens provided less detailed information. The mechanical characterization showed that aerial lime binders, and consequently mortars, are weakened in the presence of Poly(ethylene glycol) - PEG, a PCM. It was observed that 8 % of PEG in the binder lower the resistance to compression by 36 %, resistance to scratch on 76 % and flexural resistance by 32 %. Finally, this study also proposes a model for the physical interaction between the PCM and the aerial lime-binder to explain the observed weakening mechanism: PEG can hinder the correct crystalline interlocking between the calcite crystals in the carbonated binder, and act as a lubricant promoting their sliding under compressive forces.