Francis Gerard Collins

Bio: Francis Gerard Collins is an academic researcher from Monash University. The author has contributed to research in topics: Portland cement & Compressive strength. The author has an hindex of 27, co-authored 62 publications receiving 3956 citations. Previous affiliations of Francis Gerard Collins include Monash University, Clayton campus & Deakin University.

Reinforcing effects of graphene oxide on portland cement paste

Abstract: In this experimental study, the reinforcing effects of graphene oxide (GO) on portland cement paste are investigated. It is discovered that the introduction of 0.03% by weight GO sheets into the cement paste can increase the compressive strength and tensile strength of the cement composite by more than 40% due to the reduction of the pore structure of the cement paste. Moreover, the inclusion of the GO sheets enhances the degree of hydration of the cement paste. However, the workability of the GO-cement composite becomes somewhat reduced. The overall results indicate that GO could be a promising nanofillers for reinforcing the engineering properties of portland cement paste.

The influences of admixtures on the dispersion, workability, and strength of carbon nanotube-OPC paste mixtures

Abstract: Carbon nanotubes (CNT) have excellent mechanical properties and have the potential, if combined with Ordinary Portland Cement (OPC), traditionally a brittle material in tension, to become a nano-composite with superlative mechanical properties. However, highly attractive van der Waals forces between CNTs create coherent agglomerates that prove difficult to disperse within the cement matrix and reduce the fluidity of the fresh mixture. Good dispersion of CNTs, while maintaining good workability of fresh OPC–CNT paste mixtures, is a prequalification before CNT-cement nanocomposites can be considered as a future building and construction material with enhanced mechanical properties. This paper reports the results of investigations of the dispersion, workability, and strength of CNT aqueous and CNT–OPC paste mixtures, with and without several generically different dispersants/surfactants that are compatible as admixtures in the manufacture of concrete. These include an air entrainer, styrene butadiene rubber, polycarboxylates, calcium naphthalene sulfonate, and lignosulfonate formulations. Aqueous mixtures were initially assessed for dispersion of CNTs, followed by workability testing of selected OPC–CNT-dispersant/surfactant paste mixtures. A broad range of workability responses were measured and the CNT dispersion within hardened pastes was qualitatively assessed by SEM analysis.

Microcracking and strength development of alkali activated slag concrete

Abstract: Alkali activated slag concrete (AASC) is made by activating ground granulated blast furnace slag with alkalis without the use of any Portland cement. This study investigates the level of microcracking which occurs in AASC when subjected to various types of curing regimes. The corresponding compressive strength developments of AASC were monitored. The level of microcracking were measured using three different types of tests: (1) frequency and size of surface cracks using crack-detection microscope (2) water sorptivity tests measuring absorption of water by capillary attraction and (3) mercury intrusion porosimetry (MIP) tests which measured the pore size distribution of AASC and AAS pastes (AASPs). The results show that the lack of moist curing of AASC increased the level of microcracking measured using all three different tests mentioned above. The strength development of AASC is also significantly reduced by lack of moist curing.