Materials development and innovation

This special issue of the Australian Journal of Civil Engineering contains seven papers relating to the theme Materials Development and Innovation. In the past decade a significant goal of research in civil engineering has been to achieve improved performance and durability of reinforced concrete structures and infrastructure. A great breadth of research has been conducted in this area ranging from developing a fundamental understanding of the mechanisms that control the durability of cementitious materials, through to the development of high performance materials and retrofitting techniques. This special issue contains seven articles from across a wide range of aspects of materials in civil engineering including both experimental and analytical modelling. Motivated to improve the performance of concrete, nano-scale graphene materials can be introduced. Mohammed et al. (2018) reviews the literature on the addition of graphene oxide (GO) materials into the cementitious matrix. Research shows that the modified cementitious mixture exhibits enhanced strength and durability above that of control mixes. At a microstructural level, the addition of GO enhances the hydration process by increasing the number of gel pores and reducing the number of capillary pores. Future challenges are finally identified that relate to the larger-scale application of nanomaterials in concrete, the development of efficient mixing procedures, as well as environmental challenges arising from the use of nanomaterials. In a bid to reduce the carbon footprint associated with cement production, El-Hawary and Nouh (2018) investigate the partial replacement of cement in concrete mixes with filler materials. Two filler materials are considered, namely, crushed limestone and crushed dolomite, while various cement replacement ratios are experimentally investigated. The tests show the main advantage associated with introducing the fillers is increased dimensional stability leading to a reduction of shrinkage and cracking. In addition, resistance to alkali-aggregate reaction is improved. The addition of fillers, however, largely leads to increased water penetration and absorption, in addition to reduced strength properties. The importance of investigating filler fineness in future studies is identified. In Visintin et al (2018) a methodology for predicting the influence of blending macroand micro-fibres on the serviceability behaviour of ultra-high performance fibre reinforced concrete (UHPFRC) is presented. This work presents the outcomes of an experimental study undertaken to measure the influence of fibre blending on the direct tension and tension stiffening behaviour of UHPFRC, and it is shown that mixes with blended fibres have more ductility in tension and undergo more tension stiffening than mixes with a single fibre type. The analysis procedure presented shows how the serviceability behaviour of UHPFRC members can be predicted based on the results of simple experimental tests, and hence limits the need for expensive member level testing when designing new types of fibres or new types of UHPFRC. Concrete is consumed on a massive scale around the world and hence the ability to minimise the use of raw materials in its manufacture can have tremendous benefit to the natural environment. In addition, the incorporation of waste materials into concrete offers an added benefit by utilising the waste stream. The incorporation of silica mineral waste, also referred to as ‘eco sand’, into high strength concrete is investigated by Murthi et al (2018). Tests show workability and morphology to not be compromised with the additional of the eco sand. Also, optimal concrete strength is achieved with a 25% eco sand content and this strength is higher than the reference mix that contains conventional naturally occurring aggregate. Smyl (2018) proposes a new approach to analytically relate the hydraulic conductivity of cement based materials to the unsaturated electrical conductivity based on a van Genuchten-Mualem framework. The approach allows the easily measured electrical conductivity to be used to predict the difficult to measure hydraulic conductivity. Application of the approach should significantly reduce the scatter of predictions for the hydraulic conductivity and hence improve the ability to make predictions of the durability of cement based materials. Understanding of the performance of the cement sheaths in wells is essential to preventing leaks between formation fluids and the surrounding environment. Despite the environmental risk associated with sheath failure, there is currently a lack of information on the basic mechanical properties of the class G cements used in their construction. To address this limitation Arjomand and Bennett (2018) seek to expand the inventory of mechanical property observations, focusing particularly in the influence of curing temperature and confining pressure. The results of their work show AUSTRALIAN JOURNAL OF CIVIL ENGINEERING 2018, VOL. 16, NO. 2, 79–80 https://doi.org/10.1080/14488353.2018.1552507