Enhancement of Cement Paste with Carboxylated Carbon Nanotubes and Poly(vinyl alcohol)

Abstract

Cement has been a major consumable material for construction in the world since its invention, but its low flexural strength is the main defect affecting the service life of structures. To adapt cement-based materials to a more stringent environment, carboxylated carbon nanotubes (CNTs-COOH) and poly­(vinyl alcohol) (PVA) are proposed to enhance the mechanical properties of cement paste. This study systematically verifies the synergistic effect of CNTs-COOH/PVA on the performance of cement paste. First, UV–Vis spectroscopy and FTIR spectroscopy prove that CNTs-COOH can provide attachment sites for PVA and PVA can improve the dispersion and stability of CNTs-COOH in water, which demonstrates the feasibility of synergistically enhancing cement paste. When a 0.015% CNTs-COOH suspension with 0.1% PVA is added, the flexural strength of the cement paste increases by 73, 32, and 42% compared with control specimens at curing ages of 3, 7, and 28 days, respectively. The strength enhancement mechanism is revealed from the aspects of cement matrix enhancement and interface enhancement. Thermogravimetric (TG) analysis and mercury intrusion porosimetry (MIP) prove that CNTs-COOH can enhance the hydration degree of the cement matrix and fill the pores introduced by PVA. Based on the fact that PVA can improve the dispersibility and the nucleation site effect of CNTs-COOH in cement paste, molecular dynamics simulation confirms that PVA can bridge CNTs-COOH and C–S–H to enhance the interfacial bonding by 64.1%.

A Biomimetic Cement-Based Solid-State Electrolyte with Both High Strength and Ionic Conductivity for Self-Energy-Storage Buildings

“…It has high ionic conductivity, superior water retention prowess, and cycling stability, can be a viable filling candidate [ 30 – 32 ]. PVA has also shown commendable interface compatibility with cement [ 33 , 34 ], effectively filling voids and mending fissures. Additionally, compared to other commonly used electrolyte materials such as sulfuric acid and sodium sulfate [ 35 ] which may cause corrosion to the cement, KOH brings a stronger alkaline environment and is conducive to the hydration reaction and strength development.…”

Review of Boron Nitride Nanosheet-Based Composites for Construction Applications

“…Conventional concrete has been a great limitation to the modernization of the construction industry, over the past few decades, due to its low tensile strength, quasi-brittle structure, and vulnerability to chemical attacks. − Nanotechnology appears to be a promising way to revolutionize concrete manufacturing, and study in this field can bring significant performance rewards for the construction industry. A review of the literature shows that nanoparticles such as nanosilica, − carbon nanotube (CNT), − and graphene oxide (GO) − can improve microstructure, ,, enhance mechanical properties, − and provide better electrical and thermal properties of cementitious composites. − …”