Fracture Behaviour of Concrete with Reactive Magnesium Oxide as Alternative Binder

Abstract

This research evaluates the fracture behavior of concrete with reactive magnesium oxide (MgO). Replacing cement with MgO is an attractive option for the concrete industry, mainly due to sustainability benefits and reduction of shrinkage. Four different MgO’s from Australia, Canada, and Spain were used in the concrete mixes, as a partial substitute of cement, at 5%, 10%, and 20% (by weight). The fracture toughness (KI) intensity factor and the stress–strain softening parameters of the wedge split test were evaluated after 28 days. The experimental results showed that the replacement of cement with MgO reduced the fracture energy between 13% and 53%. Moreover, the fracture energy was found to be correlated with both compressive strength and modulus of elasticity. A well-defined relationship between these properties is important for an adequate prediction of the non-linear behavior of reinforced concrete structures made with partial replacement of cement with MgO.

MgO-Based Cementitious Composites for Sustainable and Energy Efficient Building Design

“…Reactive MgO is not only used for self-healing but also frequently used to optimize the shrinkage behavior of concrete. While M92-200 is a moderately reactive grade of MgO that has been used for a variety of applications, researchers have also used highly reactive grades of MgO to reduce shrinkage in concrete [49]. Both reactive MgO types, therefore, have a high potential for self-healing of drying shrinkage cracks.…”

“…Because of these huge quantities, the impact on the environment is substantial in terms of embodied energy consumption, raw materials required, and greenhouse gas emissions. Indeed, the latter aspect amounts to around 5-7% of the anthropogenic carbon dioxide emitted, contributing to global warming, mostly because of the Portland cement, one of the widely used binders of modern concrete mixtures, which is not environmentally friendly [49]. A building's total life cycle energy consumption is divided into two categories: embodied energy and operational energy.…”

“…Examples are recycled metals, bio-based polymers, and materials for renewable energy. In some cases, biomaterials can be interesting for combined applications, such as bioremediation and fuel production [49]. There are also eco-friendly binders that lead to less carbon dioxide emissions than OPC, namely including magnesium phosphate cement, geopolymer, alkali-activated slag cement, and super sulfate cement [51][52][53][54][55][56][57][58][59][60].…”

Deformation and Cracking Resistance of MgO-Incorporated Cementitious Material: A Review

“…In addition, with the increase in the MgO content, the growth rate of concrete expansion becomes higher, and the time to reach a constant strain becomes longer [ 28 , 29 ]. Though the expansion of concrete or mortar increases with the content of MgO, mechanical properties such as compressive strength decrease in the range of 8.8% to 24.7% when using MgO contents of 5% to 20% [ 30 ]. The reduction in compressive strength grows with increasing MgO content [ 7 , 31 , 32 ], and the flexural strength decreases with the addition of MgO as well but reduces less than compressive strength [ 12 , 31 ].…”

“…J.A. Forero et al [ 30 ] investigated the fracture toughness of concrete with MgO as a partial substitute for cement at 5%, 10%, and 20% using the wedge splitting test at 28 d. The incorporation of MgO reduces the fracture energy by 13%–53%, and the reduction in fracture energy rises as MgO content is increased. This can be related to the weakening of the interfacial transition zone since the decrease in CSH content and the increase in brucite content both take place.…”