The topic of emission reduction and recycling in civil engineering is highly discussed topic over last years. With respect to construction waste production, it is obvious to reuse materials such as concrete. Coarse aggregate recycling and reinforcement rebars separation are the most used procedure in this field so far. Recently, methods including recycling of concrete cementitious matrix were introduced to the market. As such, the concrete matrix consists of matured hydration products of the cement (calcium hydroxide, calcium silica hydrate, etc.) as well as non-hydrated Portland cement particles (clinker), which can represent up to 5 % of the matrix. The focus of this article is placed on microscopic level of cementitious composite with admixture of finely grounded recycled concrete. The impact of recycled addition on micro-structure of the composite, namely the percentage representation of individual material phases, is investigated by image analysis of micro-graphs obtained with scanning electron microscopy. The micro-mechanical performance of each composite is examined with displacement driven grid indentation on several levels of the sample. In consideration of the complexity of the cementitious composite with addition of finely grounded concrete, additional testing of input materials and referential cement paste sample is indispensable to properly distinguish mechanical properties of each composite phase. Young’s modulus of individual phases is thus determined from spectral deconvolution of obtained indentation data with respect to the composite structure.Keywords: Recycled concrete, phase, nano-indentation, SEM, spectral deconvolution, image analysis
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