The X-ray diffraction (XRD) technique has been widely used in order to investigate anhydrous and hydrated cement phases. In this study, XRD was used in order to analyze the concrete floor polishing waste (CFPW) and cementitious paste containing CFPW. The diffractograms obtained were compared with literature data in order to identify the phases of analyzed materials. Rietveld refinement of XRD pattern of paste containing 12% of CFPW addition was also carried out, in order to analyze calcite and aragonite structures, as these phases are calcium carbonate polymorphs that contribute to matrix filling. XRD pattern of CFPW showed a high concentration of carbonate phases, indicating that the concrete waste was carbonated. The CFPW addition in the cementitious matrix changed the hydrate cement products, as it induced the formation of carboaluminate phases, such as hemicarbonate. Calcite, which is a stable phase, contributed better to the filler effect, as its particles have higher volume than aragonite.
Flexible films of a conductive polymer nanocomposite-based castor oil polyurethane (PUR), filled with different concentrations of carbon black (CB) nanoparticles or multiwall carbon nanotubes (MWCNTs), were obtained by a casting method. The piezoresistive, electrical, and dielectric properties of the PUR/MWCNT and PUR/CB composites were compared. The dc electrical conductivity of both PUR/MWCNT and PUR/CB nanocomposites exhibited strong dependences on the concentration of conducting nanofillers. Their percolation thresholds were 1.56 and 1.5 mass%, respectively. Above the threshold percolation level, the electrical conductivity value increased from 1.65 × 10−12 for the matrix PUR to 2.3 × 10−3 and 1.24 × 10−5 S/m for PUR/MWCNT and PUR/CB samples, respectively. Due to the better CB dispersion in the PUR matrix, the PUR/CB nanocomposite exhibited a lower percolation threshold value, corroborated by scanning electron microscopy images. The real part of the alternating conductivity of the nanocomposites was in accordance with Jonscher’s law, indicating that conduction occurred by hopping between states in the conducting nanofillers. The piezoresistive properties were investigated under tensile cycles. The nanocomposites exhibited piezoresistive responses and, thus, could be used as piezoresistive sensors.
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