This document discusses research into how marine biofouling affects the durability of concrete sea defences. The research investigates how cleaning methods can alter the susceptibility of concrete to algal growth and how factors like nutrients, surface roughness, and moisture influence colonization. A predictive model will be developed to show how cleaning impacts colonization over time. Trials are testing photocatalytic self-cleaning concrete coatings to reduce maintenance costs by destroying organic pollutants that cause deterioration. The research aims to understand how surface topography and coatings can prevent spore settlement and develop long-term testing of coatings and precast units in marine environments.

1. Marine Biofouling and its implications on the Durability of Concrete Sea Defences The action of concrete cleaning methods (both physical and chemical) on concrete sea defences can alter their properties and may alter the susceptibility of the concrete to algal growths. In this research the colonisation of concrete revetment armour units at Blackpool’s Central Area Coast Protection Scheme, by algal growths is investigated in terms of their dependence on certain physical and chemical parameters of the environment and the concrete including the supply of nutrients, surface roughness and moisture availability. It is hypothesised that changes in these characteristics caused by cleaning will affect the colonisation of the concrete by organisms. By identifying the important factors which determine the extent of colonisation of a concrete by algal growths, a predictive model can be constructed regarding the importance and controllability of various factors in the colonisation of concrete by algae. This research will investigate Biofouling, changing the colonisation and growth patterns of organisms (especially Enteromorphaintestinalis) on concrete. The essence of this programme will be to trial Photocatalytic, Self-Cleaning Concrete, reducing costly maintenance by destroying most organic/inorganic pollutants that contact marine concrete and cause biodeterioration and discoloration. Fig. 1 A spore release rate of 5 billion spores per day per metre square of colonised surface has been estimated. Swimming spores look for a home Fig. 2 EnteromorphaIntestinalis;A portion of an un branched, hair like filament. A tran-section of an axis demonstrates a single layer of cells, making a hollow structure. Fig. 3 Sea Defence Revetment Armour colonised by EnteromorphaIntestinalis. Colonisation takes only days to completely cover the steps, forcing the council to steam clean every few weeks providing safe public access to the beach. Surface Bonding Marine organisms are known for their remarkable adhesive properties, forming very strong bonds, to a variety of surfaces ranging from rocks to concrete and to other organisms, under a wide range of conditions of temperature and salinity. These adhesives are also remarkable for their strength. It is the constant breaking of this strong bond by cleaning away the Enteromorpha from the concrete and its effect on the surface with its implications on permeability, and long term durability which will be the essence of this research. Anti Fouling Coatings Trials (underway) A considerable body of work is going on around the world to understand better the characteristics of surfaces that lead to low adhesion and foul release. Site Trials are underway of several photocatalytic coatings as part of this research, (Figure 4). Applications and monitoring are ongoing and the results will form part of the authors PhD thesis. Surface Engineering Enteromorphaspores are strongly attracted to grooves (scratches) that are of similar dimensions to that of the spores (Figure 1). It may therefore come as a surprise to find that scientists are investigating manipulating surface topography to prevent settlement. Researchers are trying to create a surface that the spores cannot ‘recognise’ or find inhospitable for settlement. This wall will be the site of the Photocatalytic coatings. Fig.6 ESEM shows spore settlement and adhesive Fig 4. Coatings Trial site. These steps are on New South Promenade. The Council have to keep algae free for safe access. A Chlorine based product is used Photocatalytic, Self-Cleaning Concrete The novel manufacturing process has been developed and verified in laboratory research and is now ready for demonstration of practical use in a marine context. Product concepts for e.g. self-cleaning windows, hydrophilic ceramic tiles or antibacterial refrigerators have been developed and evaluated – why not marine concrete? Titanium dioxide is widely used as a white pigment in paint, plastics, cosmetics, and a host of other products. Making it photocatalytic requires manipulating the material to create extremely fine nanotechnology-sized particles with a different atomic structure. Extensive research into photocatalysts is being conducted worldwide, however before the materials can be widely used with confidence, this research will develop long-term exposure tests of precast units and coatings in a hostile environment to determine the best dosage rates and application techniques, compatibility with admixtures and fibres, the longevity of treatments, and the treatment’s effect, if any, on the durability of marine structures in the United Kingdom. Fig. 5insert shows spore settlement Fig. 7 Abrasion damage to the concrete, partly by sand, pebbles, salt and debris. However the chlorine is poured down the steps on a regular basis, accelerating the damage Marine Biofouling and its implications on the Durability of Concrete sea defences This poster is a an introduction to the proposed study submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy The author gratefully acknowledges support from the University. The contents of this poster reflect the views of the author, who is responsible for the accuracy of the data presented herein. 9 June 2009 PHughes1@uclan.ac.uk Image no. 2 www.plingfactory.de/.../Chlorophyta.htmImages 1,5,6 - Professor J Callow Peter Hughes University of Central Lancashire 2009