CEMENT CONTAMINATION


Wash Out and Wash Water in Construction

Concrete is a product that has no place in modern construction, not least for its damaging effect on the planet at the birth of the odious stuff, but for the after effects it leaves behind. In the past, I have discussed the massive embodied energy emissions this outdated and unwelcome material creates as well as many other reasons for not using it in construction. There are two very undesirable and hugely unwanted effects of concrete production and use, that the vast majority of us do not know about, simply because they are never brought to our attention! The first effect I refer to is:

Washout

Washout is exactly what it says it is – Washing out concrete carrying or delivering apparatus, such as mixers, pumps, trucks and hoppers. In each case after every operation, the equipment must be thoroughly cleaned – its obvious why, because if the machinery was not cleaned with copious quantities of water, the concrete would set and very expensive plant would have to be sent to the scrap yards. It has been a known “punishment” in the industry for a disaffected concrete worker to leave a couple of cubic metres in a drum or in a chute over the weekend, resulting in a massive solid problem for the boss on Monday!

So where does the washout and wash water go? This is an operation that is rarely mentioned, because although rules may exist, nobody supervises the washout operations. If the residue of the washout operation permeates the earth or worse a drain, it leaves deposits of Chromium V1, Copper, Iron, Selenium, Vanadium and Zinc

The lime found in cement and concrete products easily dissolves in water, just like sugar. Lime is alkaline, so as a result concrete slurry and any water that comes into contact with cement or concrete, becomes strongly alkaline (pH11-13). This is deadly to aquatic life.

Plants, insects and animals can be burnt or killed by high pH water. High pH substances such as slurry or concrete wash water will attack the sensitive membranes of fish and eels, including the gills and the skin; effectively burning them much the same way acid burns us.

Often fish and eels try to jump out of the stream to escape the burning water resulting in death by suffocation. All life in a stream can be wiped out by a concrete or cement slurry or washout discharge, and will take years to rectify. A recent report from New Zealand indicated that 30% of fish that died as a result of poison discharge were killed by washout discharge.

In the USA alone the amount of concrete washout material and wash water generated each year accumulates to approximately:

34 times more concrete than was used to build the Sears Tower in Chicago (2 million cubic fee/72,000 cubic yards), the World’s tallest building until 1996

or

Enough concrete to build an 8-lane freeway system 175 miles long

or;

Nearly 3/4 the amount of concrete used to construct the entire Hoover Dam and

Enough water to provide a city of 50,000 people for nearly three months.

Imagine how much wasted water is used not just making concrete, but with the wash water needed several times a day.

The second little known, but large problem is Cement Carbon Emissions

We all hear about the effect of concrete in construction and the main carbon emission offender is only one component of concrete – Cement.

While most of the population has been busy worrying about travelling by air and car in a responsible manner, the cement industry has been quietly pumping more CO2 emissions into the air, more than the entire aviation industry. Cement manufacture is responsible for 5% of all global industrial carbon emissions and is increasing rapidly. China alone was responsible for 540,000 tonnes of carbon dioxide emission last year, as a result of cement manufacture. Predictions are that global cement manufacture will rise to a figure in excess of 5 billion tonnes by 2050. To give you some idea of the scale of the problem, Lafarge, the global concrete manufacturer has purchased 17 factories in China over the past few years and in the last 16 years the increase in carbon emission, the Lafarge contribution increased from 79.2 million tonnes to 94.4 million tonnes. Concrete production is set to rise by around 80% more by 2020 as demand from the developing world increases. Carbon emissions will increase accordingly.

It is a very low-profile industry and the vast population of the planet who do care about environmental issues, are not even aware that making cement produces any carbon emission, let alone in such massive quantities.

The cement manufacturing process depends on burning vast amounts of coal to more than 1,500ºc and the decomposition of limestone, a chemical change that frees carbon dioxide as a by-product. It does not matter what governments try to do, cement production will always release carbon dioxide. Nothing can change the chemistry, so emission cuts are impossible. The only way to reduce these alarming figures is to reduce the demand of the products that require cement.

Construction must start shouldering responsibility and turn to Modern Methods of Manufacture. There are many solutions for off-site construction, using renewable materials that are approved worldwide. Many engineered systems are available at a much lower cost both fiscal and environmental, much faster and provide 21st century living conditions, so why continue to use such ancient and dangerous materials and methods.