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Concrete Infrastructure Research Group (CIRG)




Interface properties of multi-mix elements

Functionally graded “multi-mix” elements in which high cement concrete mixes are located only where necessary within an element offer a promising option for cement reduction in traditional RC structures. To apply this technology, the properties of the interface between different concrete mixes are of interest. Our research looks to establish the durability of this interface to ensure that an uplift in mechanical and durability properties can be achieved without weakening other properties. 

Multi-mix elements result in varying interface zones within the element where concretes with different fresh state and hardening properties meet. At these zones, intermixing or reduced bond strength can occur if the concrete mixtures are not compatible and/or the casting processes are not chosen carefully. The aim of our research group is to identify properties and casting processes that promote interlayer bond strength and control any intermixing. Acceptable thresholds to maintain the mechanical and durability properties of multi-mix elements are being evaluated. Work includes investigation into how multi-mix elements behave when exposed to aggressive substances, as well as tensile and shear stresses, designed to isolate any potential weakness generated by layering of multiple mixes. 


Forsdyke, JC, Lees, JM. (2023) Model fitting to concrete carbonation data with non-zero initial carbonation depth. Mater Struct 56, 22.
Brault A, Lees JM. (2020) Wet casting of multiple mix horizontally layered concrete elements. Construction and Building Materials, 247, 118514.

Torelli G, Giménez Fernández M, Lees JM. (2020) Functionally graded concrete: Design objectives, production techniques and analysis methods for layered and continuously graded elements. Construction and Building Materials, 242, 118040.

Torelli G, Lees JM. (2019) Fresh state stability of vertical layers of concrete. Cement and Concrete Research, 120, 227-243.



The Concrete Infrastructure Research Group develops sustainable infrastructure, through an improved understanding of existing infrastructure assets, the use of new materials, and the creation of innovative structural solutions.


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