Photocatalytic Concrete and De-Pollution - Oakdale (Contracts) Ltd


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Welcome to our AirPave CPD photocatalytic concrete and depollution.

Our learning aims and outcomes are to learn about the effective air pollution on our population’s health, the use of titanium dioxide as a photocatalyst, the science behind photocatalysis, the application of photocatalysis in concrete paving and, the depolluting benefits of photocatalytic concrete. This presentation will show you how our industry can take direct action to reduce the level of harmful NOx in our towns and cities. This type of concrete will give you the ability to tackle the high pollution levels that have become a serious problem for us all. The concrete products I will introduce today have been developed by Oakdale in partnership with Hanson cement.


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Air pollution

Now let's look at the problem of air pollution. Public awareness of this problem is increasing in the light of new data from DEFRA and recent criticism of the government by the courts who accused them of repeated delaying tactics instead of trying to deal with the problem. Air pollution or poor air quality has become a major problem as Britain’s cities are choked with toxic pollutants. Air pollution caused by noxious exhaust gases are collectively referred to as NOx. So what is NOx? NOx is a genetic term every first to nitrogen oxide and nitrogen dioxide both of which are produced during the combustion of diesel fuel. NOx is a toxic gas which inflames the lungs and puts asthmatics at increased risk of attacks. Heart attack rates rise during air pollution surges children exposed to Knox have smaller lungs. Air pollution has been linked to slower improvement in cognitive development in children, and cognitive decline in older people. Britain's 12,000,000 diesel cars, 4,000,000 diesel vans, 68,800 diesel trucks and buses now burn 22,000,000 tons of diesel a year. Scientists estimate air pollution is linked to 40,000 premature deaths a year. About a tenth of Britons annual total, more than obesity and alcohol combined. At its simplest and public health terms invisible air pollution is where smoking was 30 years ago, in terms of the scale and certainty of the risks and the lack of public understanding of them.


Oxford Street has recorded the highest level of NOx in the world. It's so bad that apps have been developed for pedestrians and cyclists to plot safe routes around London. It is clear air pollution is a huge problem. NOx gases also react to form smog and acid rain as well as being central to the formation of fine particles and ground level ozone, both of which are also associated with adverse health effects.


Let's look at the latest different DEFRA air pollution in the UK. Here's an extract from the report, evidence on the health impact of exposure to nitrogen dioxide has strengthened significantly. It is well established that exposure to high concentrations of nitrogen dioxide causes inflammation of the Airways, decreased lung function and respiratory symptoms. However more recently evidence has been released directly linking nitrogen dioxide exposure to mortality. Applying this evidence to the exposure levels across the UK suggests that exposure to nitrogen dioxide is increasing mortality by the equivalent of 23,500 deaths per year. Additionally many of the sources of NOx are also sources of particulate matter. The impact of exposure to particulate matter pollution is estimated to have an effect on mortality equivalent to nearly 29,000 deaths in the UK. There may be overlap between these two estimates of mortality but the combined impact of these two pollutants is a significant challenge to public health.


Lack of compliance

Let's examine the lack of compliance with regulations and limits. Pollution levels of NOx are measured in micrograms per cubic meter. The one hour limit for nitrogen dioxide is 200 micrograms per cubic meter. It is permitted to exceed this value 18 times per year. The annual mean average nitrogen dioxide limit is 40 micrograms per cubic meter. The UK is divided into 43 monitoring zones. During 2015 two zones had locations where the one hour limit of 200 micrograms was exceeded on more than the permitted 18 occasions. These were Greater London urban area and South Wales and only 6 zones met the annual mean average limit of 40 micrograms in 2015. The remaining 37 had higher concentrations. Out of interest the six compliant zones were Brighton, Blackpool, Preston, the Highlands, the Scottish Borders and Northern Ireland.


Lack of government and local authoritity enforcement

Let's now look at the lack of government and local authority enforcement. The government are dragging their heels and were recently defeated in the courts over their continued failure to tackle the UKs air pollution crisis. Mr justice Garnham said the Secretary of State Andrea Leadsom was in breach of a court order to take action in the shortest possible time and that further delays would constitute a further breach. James Thornton chief executive officer of client earth was quoted as saying the government has never stopped deleting when it comes to cleaning up our air.


So what strategies have been put forward to combat NOx. On the 17th of December 2015 the UK government and the devolved governments published their national air quality plan for nitrogen dioxide. The plan sets out how the UK will achieve compliance with EU limit values for nitrogen dioxide in the shortest possible time. One of the aims is to make the data more openly available, so that the whole country people, businesses and the public sector can use them to take better decisions and to spur innovation. This is what Oakdale has done as I will go on to explain.


What is Titanium dioxide and how is it created?

In this part of the presentation we will examine the properties of titanium dioxide and how it is manufactured. Titanium dioxide is derived from the ore ilmenite. The manufacturing process removes the iron leaving titanium dioxide crystals. The crystals are then ground to the required particle size dependent upon the end use. Its most well known as a white pigment because of its high brightening and covering capacity. It is used in the manufacture of lacquers, paints, plastics and paper as well as cosmetic and pharmaceutical products. Because of its non-toxic properties the use of titanium dioxide is also permitted in the food industry. When milled to a size of 50 nanometres it has excellent photocatalytic properties.


What is photocatalysis?

As you will know a catalyst is a substance that increases the rate of a chemical reaction, without itself undergoing any permanent chemical change. Ultraviolet light causes titanium dioxide to release an electron, a negatively charged particle. The titanium dioxide is now positively charged. The freed electron attaches itself to the oxygen atoms in the atmosphere. The oxygen becomes negatively charged and becomes a superoxide anion. The negatively charged titanium dioxide wants to be neutral so it takes an electron from water vapour present in the atmosphere. This loss of an electron from the water molecule causes it to become a hydroxyl radical. Superoxide anions and hydroxyl radicals decompose organic compounds through oxidation and also by the same method hazardous NOx converted into homeless nitrates. During the photocatalytic process the titanium dioxide is neither eroded nor degraded, it remains unchanged.


Use and development of titanium dioxide in construction

Let's now look at the historic use and development of titanium dioxide in the construction sector. In the early 1970s work done by professor Fujishima and Honda on the photocatalytic properties of titanium dioxide, prompted research resulting in viable alternatives for dealing with air pollution. Prior to this abatement strategies were essentially based on electrostatic filters and membranes to reduce fine particulates. Chemical and catalytic processes were also used to purify air from hazards like sulphur dioxide, nitrogen dioxide, carbon monoxide etcetera. Application of photocatalysis to construction materials began towards the end of the 1980s, where two important effects had been observed. The self-cleaning effect and the depolluting effect due to the oxidation of harmful gases such as NOx. Adding titanium dioxide to cement brings the depolluting benefits of photocatalysis to concrete products. Photocatalytic cements have been trademarked by Hanson Heidelberg branded TioCem. The main reasons why titanium dioxide is the most used photocatalysis for such applications are its brilliant white colour hence very suitable for white cement concrete and it is extremely stable, it does not undergo photo another corrosion and does not react with cementitious phases. So now we understand the science behind photocatalytic concrete but, how do we know it works in practice? Well Italcemente part of the Hanson Heidelberg group have gone to great lengths to measure its effectiveness using extensive laboratory testing. They have created a model village to illustrate its effectiveness.


The model village has been constructed using photocatalytic cement and placed under a sealed glass Dome to create and control levels of polluted air and to measure the level of depollution achieved by the cement. The photocatalytic reaction is triggered by light. Before the light is switched on NOx is passed over the model and the concentration level is measured and plotted overtime. As the light is switched on the NOx levels are monitored and full significantly despite the continuous flow of knocks over the model. The graph illustrates a decrease in NOx concentration of over 50% and that decreases maintained overtime. After 10 minutes the light is switched off and NOx levels are slowly increased back to the level at the start of the test.


Thus proving the depolluting effect of the photocatalytic cement in a controlled environment. But how would it perform in real life conditions? Well the picada project was commissioned to find out. Picada photocatalytic innovative covering applications for depollution assessment started in 2002 lasting 4 years and costing 3.4 million euros. It assessed the benefits provided by the use of photocatalytic cement. Laboratory results were compared to results in real world conditions by monitoring the efficiency of photocatalytic pavers in a car park and in a simulated street Canyon.


Experimental evidence showed that abatement of hazardous gas pollutants like NOx can reach and in some optimal conditions of light exposure and wind circulation, breakthrough the threshold of 60%. So we've seen evidence of photocatalysis at work in the laboratory and in simulated tests. Now let's have a look at some real life projects. In 2002 a photocatalytic water was used to cover the asphalt surface of a section of Villa Marandi in Milan. A road which is 230 meters long and 10 metres wide and which everyday says traffic flow of around 1,000 vehicles per hour.


Monitoring proved a reduction in nitrogen oxides on this urban road of around 60%. In 2003 photocatalytic self-locking blocks were laid over 8,000 square metres on an industrial site in the province of Bergamo. The tests showed that in the area covered by the photocatalytic blocks the concentration of nitrogen oxides measured was clearly lower than in a compatible area. The reduction calculated on the basis of the average values recorded is around 45%. This was also confirmed by other independent tests for instance, the implementation of photocatalytic concrete over a total area of about 7,000 square meters of the roads in Milan contributed to a reduction by 60% of the NOx concentration in the air. A city centre St and burger Moore was repaved with photocatalytic concrete paving blocks, about 12,000 square meters NOx concentration was measured simultaneously on two sites. One with photocatalytic blocks and one with normal bituminous concrete. The daytime air monitoring showed an average NOx abatement of 45%. This short CNN bulletin explains further.


The Romans invented concrete over 2000 years ago. The Dome of the pantheon in Rome probably the best preserved example but concrete gets dirty very easily discoloured by pollution and rain and concrete buildings end up getting grubby before their time, that is until now. I'm here at Italcemente one of the biggest cement producers in the world and its R&D lab is simply stunning.


But what particularly sets it apart is the special ingredient that went into the concrete. You have a combination of photocatalysts, light and construction material, decomposed pollutants. So its self-cleaning concrete self-cleaning concrete. Is that not an amazing thing? It is an amazing thing. TX active as it's called was first patented in 1995. It does for cement what enzymes did for washing powder. How does the pollution disappear? The pollutant which is dirtier material can be deformed into non coral material. This doesn't change the fate of the pollutant but just accelerate the oxidation process. It's known as photocatalysis, speeding up a chemical reaction in the presence of light, which can be demonstrated with an artificial pollutant in the lab. TX active's first major project in 2003 was Richard Myers Jubilee Catholic Church in Rome. 11 years on still white brilliant white. We ever a perfect maintenance of the colour. This is the most relevant result obtained in the in our first industrial application. But to everyone's surprise TX active didn't just clean the surface of the cement but the surrounding air as well. If you cover the surface of Milan 50% of the surface with this material not all you can reduce the pollution by 50%. That's astonishing. That's astonishing. 


As we've just seen the Jubilee church in Rome utilised photocatalytic concrete. Other the key buildings that have used the material are:

  • The Vodafone village in Milan,
  • Eagle in flight in Tirana,
  • Palazzo Italia in Milan,
  • The Frost Museum of Science in Miami.


As we can see photocatalytic concrete reduces NOx and its use is growing. However it is worth pointing out that it is an extremely expensive material, and this can be a limiting factor for some applications.


Who are Oakdale (Contracts) Ltd?

I would now like to introduce you to Oakdale and the rule weight play in the reduction of air pollution. We are an independent manufacturer of concrete hard landscaping products. We are based in Catterick North Yorkshire. Our ethos is to manufacture quality products that represent good value but crucially or sustainable and kind to the environment. We call us ethos green scaping. A concept which is unique to Oakdale. Up to 85% of the material content of our products is locally sourced and recycled. Through the use of recycled local materials, our products achieved what we believe to be the smallest carbon footprint in the industry. We work closely with and have gained accreditation from CO2 Sense, an ethical investor in renewable energy projects and are members of the UK green building council, a charitable organisation which campaigns for the sustainable built environment. One of our key innovations is AirPave a revolutionary yet affordable development and photocatalytic concrete to facilitate the reduction of pollution in the urban environment. Airpave also sets new standards in environmental benefits, with up to 80% of its raw material content coming from recycled local sources. Due to Oakdale's unique production processes it is now economically viable to incorporate the latest in nanotechnology paving into any hard landscaping design without compromise to carbon footprint durability or looks.

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