## 1 Introduction  
Concrete is a ubiquitous engineering material comprised of a mixture of fine and coarse aggregates, which are consolidated together using a hydrated cement binder that hardens over time. The estimated annual global production of concrete has now exceeded 16 billion tonnes [1]. This amount to a large consumption of cementitious and mined aggregate materials. The environmental impact of increasing extraction and consumption of naturally mined materials such as sand, gravel, and crushed rock aggregates could be mitigated by substitutions with solid wastes materials. Therefore, the exploration of the potential of alternative aggregates to reduce the quantity of quarried materials used in the production of concrete is a worthwhile endeavour.  
The construction industry is widely regarded as one of the biggest consumers of natural resources, with reports stating that Australia alone extracts 130 million tonnes of aggregate annually [2]. The sustainable credentials for concrete production have long been a subject of debate, and considerable efforts have been placed into research (e.g., refs [2; 3; 4; 5; 6; 7]) on the use of recyclable materials in an attempt to reduce the consumption of naturally mined components. A further step forward in achieving sustainable concrete production would be accomplished if unmined, recycled materials could be used to replace any of the components that are normally sourced from geo-formed origins. One such material of particular interest is the use of crushed waste glass (CWG) as a replacement for any of the mined components used in the compositional mixture of concrete.  
Waste resource centres in Australia and many of the western world have now made many of these recyclable materials available through systematic waste processing. With new processing technologies, glass components are easily recovered, separated, and processed into CWG and graded as coarse/fine aggregates and powder when further processed to particle size of the order of 10 \(\upmu\)m. Aggregate CWG materials are now available in quantities significant enough that a case for constant supply can be explored. In 2016 alone, it was reported that 1.1 million tonnes of glass waste was produced in Australia, with only an estimated recycling rate of 57% where the primary mode of recycling consists of lower-value products [8]. It is also reported [9] that in 2017, China produces over 20 m tonnes of waste glass with only 53% recycled, while the USA produced 11.4 million tons with only a 26% recycle rate. The average recycle rate of waste glass in EU was 73% with some countries reaching more than a 90% recycle rate. While the recycle rate may be high in the EU zone, the varying low recycle rate in the rest of the world and the low value recycle products makes a viable case for a worldwide construction materials resource in CWG.  
The utilisation of waste materials as a replacement for traditional aggregates has been a key topic of research within the construction industry such that the application of CWG in concrete has been subjected to numerous studies [3; 10; 11; 12; 13]. However, the vast majority of research has produced inconsistent outcomes regarding the benefits of CWG in concrete mixes. Furthermore, the results for the optimal proportion of CWG substitutions and the subsequent effects on functional properties are too varied. In this work, we explore the use of recycled glass (CWG) as a fresh sand replacement and report the comparison between the mechanical properties of concrete containing varying ratios of CWG.