During any concrete production process it is important to ensure water quality standards are maintained and this can be achieved with a regular programme of concrete mixing water testing.
In this guide the water quality experts at Water Treatment Services consider the role of water in the concrete production process. The guide looks at current standards for sampling, testing and assessing the suitability of water; common mixing water sources together with potential alternatives, what you need to test for, potential pitfalls, and when and where to test.
Testing mixing water for concrete production
If you are involved in the construction industry, any water used to form the concrete you use in your projects must conform to the British Standard for Mixing Water for Concrete. The standard to look out for is called BS EN 1008:2002.
BS EN 1008:2002 deals with mixing water for concrete but also provides a specification for sampling, testing and assessing the suitability of water, including water recovered from processes in the concrete industry, as mixing water for concrete.
How often should concrete mixing water quality be tested?
Mains water is generally suitable for mixing concrete used in construction.
Other water sources can be used too, as long as steps are taken to ensure it is of high enough quality.
The industry standard is to test non-mains water at least annually in plants which are producing concrete.
In the UK, most plants which have been awarded the BSI quality kitemark also submit samples of water for testing each year to ensure their product remains up to scratch.
The importance of water in concrete
There are three main reasons why good quality water is of critical importance when making concrete.
- Wetting the surface before cement is applied. Cement sticks better to a wet surface than it does to a dry surface.
- To mix with dried materials and make it more “plastic” and easy to manipulate.
- Water is mixed with cement and other products and as it dries, the surface sets, hardens and eventually cures to reach its full strength.
The amount of water used in the mix will determine the strength of the end product of the concrete.
Getting the quantity of water wrong, or using poor quality water, can have a seriously adverse effect the finished product.
Can tap water be used for mixing concrete?
The most common practice is just to use water from the mains to mix concrete for domestic or commercial use.
Generally, if the water is safe for drinking (potable quality), it should be chemically safe for mixing concrete too.
In some situations though, and especially when construction is taking place a long way from a mains supply, contractors might prefer to use different sources of water instead. These could include:
This is particularly an issue in arid areas of the world such as the Middle East where fresh, clean, drinking water is a valuable commodity.
If contractors can prove that water drawn from other sources is just as clean and safe as mains water, then this could result in a considerable cost saving over the course of a construction project.
On larger civil engineering projects the general guidelines are to test water quality before starting to use it to mix concrete, and then at set intervals over the lifetime of the project to ensure water quality is maintained on an ongoing basis.
Water quality tests for concrete production
The exact types of testing carried out on concrete mixing water will depend on where the water is drawn from. However, the range of standard tests typically involves the following:
How and where to sample water used for mixing concrete
All construction companies should draw up a detailed schedule of concrete mixing water testing depending on the requirements of the project they are undertaking.
When drawing water from a source other than the mains supply, it is important to recognise that the chemical composition of the water may change over time.
Advice should be sought from experts, such as Water Treatment Services about how often water should be sampled and tested, depending on the particular source being used.
There are also general guidelines about where to take samples from.
Samples of water should always be taken midstream in flowing water, or at mid-depth in a static body of water.
The aim is to take water samples which are neither right at the top of the body of water, and avoid dredging the bottom.
Water samples should be taken in the same way each time testing is required.
Samples should not be shaken after being taken, as this may cause some of the dissolved gases to escape from the sample and give a false reading.
Testing should take place as soon as possible after taking the water sample, and at the very least within 24 hours… this is because wastewater decomposes quickly when stored at room temperature.
It is usually best to have on-site testing for water quality wherever possible or use a lab that is able to transport samples quickly.
Using concrete washout water for mixing
One common tactic is to use concrete washout water to mix the next batch.
As the name suggests, concrete washout water is the wastewater generated by cleaning hoppers or lorries after they have been used to contain or transport concrete or cement.
Containers have to be cleaned properly or the cement hardens and the container becomes clogged.
Additionally, washout water has a high level of suspended minerals and can’t simply be poured into the drain… in some cases, it might be possible to recycle this water for reuse.
Studies have shown that as long as washout water passes the requirements for both pH and specific gravity, there tends to be no adverse effect on the quality of the end product, although to be sure a full suite of required water tests should be completed and recorded for future reference.
Problems with water sampling
Most operations have no difficulty in keeping within the upper concentration limits for solids and other contamination as laid out in the British Standard (BS EN 1008:2002) guidelines.
However, there are some common issues which can cause water samples to fail to come up to scratch and these include:
- Incorrect water sampling techniques used
- Missing paperwork or other sampling documents
- High levels of brine and other chlorides in the water from natural sources such as boreholes
- High levels of sulphates due to the use of concrete washout water
- Using recycled water which has a higher than acceptable level of sediment
- Contamination in the sampling equipment
Using recycled water in the concrete mixing process
Many producers are still only using mains drinking water for concrete production because of worries about the quality of the product when mixed using other water sources.
However, understanding the BS EN 1008:2002 concrete mixing water guidelines, coupled with a regular programme of sampling and water testing, should give producers the confidence to go ahead and draw water from other sources.
Can trade effluent be used for concrete mixing?
Being open-minded to the possibility of using trade effluent to mix concrete can have a number of benefits, including considerable cost savings.
It can also improve the quality of trade effluent released into the sewerage system.
In turn, this reduces the possibility of the organisation being hit with penalties and remediation charges should local water sources become polluted.
If water is of a higher quality when discharged as trade effluent, then the cost for processing or removal from site reduces too.
Financial and environmental benefits
From a financial and environmental point of view, there is much to be gained from trying to reuse as much mixing water as possible on site rather than simply getting rid of it.
It’s therefore worthwhile considering the various water sources that may be available and how regular concrete mixing water testing can help maintain quality, reduce costs and improve environmental performance.
Laboratory water quality testing for concrete production
Water Treatment Services offer a comprehensive range of water testing and laboratory analysis solutions to support concrete producers, building contractors and others involved in the concrete production process.
Our experts can provide advice and support to help you identify the most appropriate strategies to ensure water used in the concrete mixing process meets the required quality standards.
With offices in London serving the South and South East England, Manchester (North West), Birmingham (Midlands), Bristol (South East England and Wales), Leeds (North and North East) and Glasgow (Scotland), supported by regional teams of specially trained technicians, in-field specialists and consultants we can offer professional, cost effective water testing and laboratory analysis solutions across the whole of the UK and internationally.
Contact us today to learn how our expert water testing and analysis services can help you maintain your water quality standards.
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