Partial replacement of cement for waste aggregates in concrete coastal and marine infrastructure: a foundation for ecological enhancement?

Published source details McManus R.S., Archibald N., Comber S., Knights A.M., Thompson R.C. & Firth L.B. (2018) Partial replacement of cement for waste aggregates in concrete coastal and marine infrastructure: a foundation for ecological enhancement?. Ecological Engineering, 120, 655-667.
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This study is summarised as evidence for the following.

	Action	Category
	Use environmentally-sensitive material on subtidal artificial structures Action Link

Use environmentally-sensitive material on subtidal artificial structures

A replicated, randomized, controlled study in 2016 in a marina in the Plym estuary, UK (McManus et al. 2018) found that replacing standard Portland-cement with Ground Granulated Blast-Furnace Slag (GGBS), Pulverized Fly Ash (PFA), or a mix of both, in concrete settlement plates did not affect the diatom species richness or abundance on plates, or the non-native macroalgae and non-mobile invertebrate species richness or community composition, but had mixed effects on the native species richness and community composition, depending on the cement used. Over four weeks, diatom species richness and live cover was similar on GGBS-concrete (2 species/plate; 19% cover), PFA-concrete (2/plate; 12%), mixed-concrete (2/plate; 20%) and standard-concrete (2/plate; 12%) settlement plates. After seven weeks, native macroalgae and non-mobile invertebrate community composition differed on different materials (data reported as statistical model results), but it was not clear which materials differed. Native species richness was similar on PFA-concrete (8 species/plate) and standard-concrete (9/plate), but lower on GGBS-concrete (8/plate) and mixed-concrete (7/plate) than standard-concrete. Non-native community composition and species richness was similar on all materials (1–2 species/plate). Settlement plates (20 × 20 mm) were moulded with recycled cement (GGBS, PFA, or a mix of both) or standard Portland-cement. Eighty of each were suspended vertically, randomly arranged, beneath floating pontoons at 0.5 m depth in June 2016. Diatoms on plates were counted using a scanning electron microscope over four weeks, and macroalgae and invertebrates in the laboratory after seven weeks.

(Summarised by: Ally Evans)