Characterization of Titanium Nanotube Reinforced Cementitious Composites: Mechanical Properties, Microstructure, and Hydration

Tuning the Hydration Acceleration Efficiency of Calcium Carbonate by Pre-Seeding with Calcium Silicate Hydrate

Nanomaterials are promising candidates for refined performance optimization of cementitious materials. In recent years, numerous studies about the performance improvement of nanomaterials using polymers have been conducted, but the modification of cement-oriented nanomaterials with inorganic modifiers is seldom assessed. In this study, we explored the performance tuning and optimization of nanomaterials by inorganic modification. In this work, hydration acceleration efficiency of calcium carbonate (CaCO₃, CC) was tuned via surface deposition with calcium silicate hydrate (C-S-H) nanogel through seeding. Multiple calcium carbonate-calcium silicate hydrate (CC-CSH) samples with varying degrees of surface modification were prepared via dosage control. According to characterizations, the degree of C-S-H modification on the CaCO₃ surface has a maximum that is controlled by available surface space. Once the available space is depleted, excessive C-S-H turns into free form and causes adhesion between CC-CSH particles. The resultant CC-CSH samples in this work showed enhanced hydration acceleration efficiency that is tuned by the actual degree of C-S-H modification. Elevated C-S-H modification causes CC-CSH's acceleration behavior to shift to enhanced early-age acceleration. According to mortar strength tests, CC-CSH with 5% C-S-H modification showed the most balanced performance, while CC-CSH with higher C-S-H modification showed faster early-age strength development at the cost of lower later-age strength. The inferior later-age strength of highly C-S-H-modified CC-CSH samples may be due to the coarsening of hydration products and stiffening of their network, as well as agglomeration caused by C-S-H adhesion. This study may offer a novel route for performance tuning of cement-oriented nanomaterials.

Portland Cement: An Overview as a Root Repair Material

Portland cement (PC) is used in challenging endodontic situations in which preserving the health and functionality of pulp tissue is of considerable importance. PC forms the main component of mineral trioxide aggregate (MTA) and demonstrates similar desirable properties as an orthograde or retrograde filling material. PC is able to protect pulp against bacterial infiltration, induce reparative dentinogenesis, and form dentin bridge during the pulp healing process. The biocompatibility, bioactivity, and physical properties of PC have been investigated in vitro and in animal models, as well as in some limited clinical trials. This paper reviews Portland cement's structure and its characteristics and reaction in various environments and eventually accentuates the present concerns with this material. This bioactive endodontic cement has shown promising success rates compared to MTA; however, considerable modifications are required in order to improve its characteristics and expand its application scope as a root repair material. Hence, the extensive chemical modifications incorporated into PC composition to facilitate preparation and handling procedures are discussed. It is still important to further address the applicability, reliability, and cost-effectiveness of PC before transferring into day-to-day clinical practice.

Synthesis of Highly-Dispersed Graphene Oxide Nanoribbons-Functionalized Carbon Nanotubes-Graphene Oxide (GNFG) Complex and Its Application in Enhancing the Mechanical Properties of Cementitious Composites

In this study, a graphene oxide nanoribbons–functionalized carbon nanotubes–graphene oxide (GNFG) complex was hydrothermally synthesized as a nanomaterial for reinforcing cementitious composites, using a modified Hummers’ method. Three types of components existed in the GNFG: Type I, the functionalized carbon nanotubes–graphene oxide nanoribbons (FCNTs–GNR); and types II and III are graphene oxide (GO) and functionalized carbon nanotubes (FCNTs), respectively, which exist independently. The dispersivity of GNFG and its effects on the mechanical properties, hydration process, and microstructures of cement pastes were evaluated, and the results were compared with those using cement pastes incorporating other typical carbon nanomaterials. The results demonstrated that dispersion of GNFG in aqueous solutions was superior to that of the CNTs, FCNTs, and GO/FCNTs mixture. Furthermore, the highly-dispersed GNFG (0.05 wt.%) improved the mechanical properties of the cement paste after 28 days of hydration and promoted the hydration of cement compared to CNTs, GO, and GO/FCNTs mixture (0.05 wt.%). The results in this study validated the feasibility of using GNFG with enhanced dispersion as a new nano-reinforcing agent for various cementitious systems.

Photocatalytic Performance Evaluation of Titanium Dioxide Nanotube-Reinforced Cement Paste

Considering the increase in research regarding environmental pollution reduction, the utilization of cementitious material, a commonly used construction material, in photocatalysts has become a desirable research field for the widespread application of photocatalytic degradation technology. Nano-reinforcement technology for cementitious materials has been extensively researched and developed. In this work, as a new and promising reinforcing agent for cementitious materials, the photocatalytic performance of titanium dioxide nanotube (TNT) was investigated. The degradation of methylene blue was used to evaluate the photocatalytic performance of the TNT-reinforced cement paste. In addition, cement paste containing micro-TiO₂ (m-TiO₂) and nano-TiO₂ (n-TiO₂) particles were used for comparison. Moreover, the effect of these TiO₂-based photocatalytic materials on the cement hydration products was monitored via X-ray diffraction (XRD) and thermogravimetric analysis (TG). The results indicated that all the TiO₂ based materials promoted the formation of hydration products. After 28 days of curing, the TNT-reinforced cement paste contained the maximum amount of hydration products (Ca(OH)₂). Furthermore, the cement paste containing TNT exhibited better photocatalytic effects than that containing n-TiO₂, but worse than that containing m-TiO₂.

Effects of Highly Crystalized Nano C-S-H Particles on Performances of Portland Cement Paste and Its Mechanism

In order to improve the early age strength of ordinary Portland cement-based materials, many early strength agents were applied in different conditions. Different from previous research, the nano calcium silicate hydrate (C-S-H) particles used in this study were synthesized through the chemical reaction of CaO, SiO2, and H2O under 120 °C using the hydrothermal method, and the prepared nano C-S-H particles were highly crystalized. The influences of different amounts of nano C-S-H particles (0%, 0.5%, 1%, 2% and 3% by weight of cement) on the setting time, compressive strength, and hydration heat of cement paste were studied. The hydration products and microstructure of the cement paste with different additions of nano C-S-H particles were investigated through thermogravimetry-differential thermal analysis (TG-DTA), X-ray powder diffraction (XRD), and scanning electron microscope (SEM) tests. The results show that the nano C-S-H particles could be used as an early strength agent, and the early strength of cement paste can be increased by up to 43% through accelerating the hydration of tricalcium silicate (C3S). However, the addition of more than 2% nano C-S-H particles was unfavorable to the later strength development due to more space being left during the initial accelerated hydration process. It is suggested that the suitable content of the nano C-S-H particles is 0.5%−1% by weight of cement.