Ailar Hajimohammadi

Analysing and Manipulating the Nanostructure of Geopolymers

Geopolymer concretes are currently being commercialised in Australia and elsewhere around the world, with a view towards enhancing the sustainability of the world’s construction industry. The fundamental geopolymer binder is an aluminosilicate gel which displays key structural features on every length scale from Angstroms up to centimetres, meaning that multiscale analysis is key to the development of a detailed understanding of geopolymer formation and performance. Here, we present results from investigations of geopolymer nanostructure, focusing on the use of infrared spectroscopy as an analytical tool. The effects of different combinations of precursors in geopolymer formation provides critical information, in particular with regard to the rate of reaction and its impact on the final distribution of elements and structures within the geopolymer binder. Formulations are designed so that the same composition is obtained by the use of precursors which release their constituent elements at very different rates under alkaline attack during geopolymerisation, and this provides essential information regarding the role of different elements in forming strong and durable geopolymer structures. Seeding the geopolymer mixture with very low doses of oxide nanoparticles presents several unexpected effects, both in terms of reaction kinetics and also in altering the nature of the zeolitic crystallites formed within the predominantly X-ray amorphous geopolymer binder.

Characterising fundamental properties of foam concrete with a non-destructive technique

ABSTRACT Lightweight foam concrete has been developing rapidly in construction industry due to its sustainability, excellent thermal insulation, excellent fire resistance and affordability. It is desired to assess the performance of the foam concrete structure on site instead of testing isolated specimen in laboratory condition, as the changes in site environment and different construction procedure will affect the testing result. For on-site testing of foam concrete, non-destructive methods are required to avoid damage to structures. Ultrasonic pulse velocity method (UPV) is one of the attractive methods used for onsite testing of concretes due to its benefits such as accurate results, high sampling rate and cost-effectiveness. UPV method can determine various concrete properties such as strength, dynamic elastic constants, defects, uniformity and effects of curing time. However, for foam concrete application, the effect of high porosity on the UPV test results is largely unknown in current literature. Existing research explored the relationship between porosity and strength for metals, as well as the relationship between UPV and porosity for normal mortars. Yet no correlation between UPV and porosity for lightweight foam concrete is developed, which is very critical in the strength estimation and site quality control of the construction. In this research, a comprehensive laboratory experiment was designed to establish the correlations between UPV, porosity, and compressive strength using UPV experiments and compressive strength tests. New equations are developed which can be used as reference for estimating the mechanical properties of lightweight foam concrete using ultrasound testing technique in civil engineering practice.