The physical-mechanical behavior and chemical bonding nature of poly-N-vinylpyrrolidone modified cement concrete

In this study, the various amounts of poly-N-vinylpyrrolidone (PVPr) were added to the cement paste, and some parameters - flowing, initial and final setting points, water absorption, compressive strength, and flexural strength were determined. The concrete containing 0.8% PVPr exhibited high water absorption, specifically, at 14 and 28 days, increased from 15.65% to 20.71% and from 16.74% to 21.67%, respectively. The final setting time increased from 238 min to 261 min. It was determined that the compressive strength of the cement mortar increased from 54.8 MPa to 58.5 MPa when the PVPr content was 0.8–1.0%. The flexural strength also improved due to the presence of PVPr, increasing from 11.58 MPa to 14.27 MPa. According to the FTIR characterization, the PVPr macromolecule interacts with Ca2+ and Al3+ ions. TGA analysis reveals that the chemical interaction of PVPr with calcium and aluminum ions limits its mass loss up to 4–5% until 400 °C.