Concrete – Part 1 - Understanding the basics

If installed correctly, newly installed reinforced concrete should last for many years with a minimal amount of maintenance; however it can be vulnerable in certain locations/uses to a number of possible defects, especially where used externally 

Source: https://www.flickr.com

Concrete is an extremely popular material for construction and can be found in most parts of the World in one form or another.  In many countries, along with the use of steel, concrete is the primary material used for buildings/structures of all shapes and sizes, because of its many positive attributes. These include; being extremely strong in compression, which means that it can sustain large loads which are applied, before it will start to deteriorate or fail. It is extremely flexible as it can be poured into infinite shapes/forms and sizes, it can be applied in situ (on site in its wet form), or it can be cast in a  factory and delivered site as a complete component (pre-fabricated), it has very good fire resistant qualities and is durable if constructed correctly and maintained well.  A significant disadvantage however is that concrete is extremely weak in tension, which in basic terms means that it will break up very easily when forces are applied that try to push or pull it apart.

Compressive and Tensile forces - To understand compression and tension forces let us think about a spring as an example.  If an even ‘push’ force is applied to each end of the spring at the same time then the spring will compress and shorten.  This action is adding compressive forces into the spring.  When a load is applied to the top of a concrete component in a building then exactly the same forces are being introduced, however concrete has the ability to withstand high levels of compressive forces, particularly when certain mixes are used or when steel reinforcement is added. Tension or tensile forces are effectively the opposite of what is described for compression.  Using our spring again as an example, instead of applying an equal ‘push’ force at either end, let us now apply a ‘pull’ force. This will lengthen the spring and add tensile forces within it.  This is what will happen toward the bottom of a concrete beam.  Whereas the compressive forces applied at the top of a concrete beam will apply load in a downward direction and compress the beam, this can also result in tensile forces appearing near the bottom of the beam which will have a tendency to want to ‘pull apart’, as identified in the image below:

Source: http://www.concretecountertopinstitute.com/

Concrete’s weakness in tension is therefore mitigated by introducing steel reinforcement (which is strong in tension) at the position in the concrete which is weakest in tension, which is near the bottom of the beam.  The result is a complete component which is strong in both compression and tension and capable of withstanding extremely large loads/forces, which is ideal for building and construction.

If installed with the correct materials/mix and good workmanship, newly installed reinforced concrete should last for many years with a minimal amount of maintenance; however it can be vulnerable in certain locations/uses to a number of possible defects, especially where used externally.  Some of the more serious concrete defects are a result of deterioration of the concrete which results in the reinforcement being exposed and starting to corrode.  Concrete is a very alkaline material, typically 12.5 to 13 on the PH scale.  When encapsulated in the very high alkaline environment of concrete, reinforced steel will passivate.  This means that the steel will be much less chemically active than it would normally be as the alkaline concrete is effectively protecting it.  A particular problem however is that concrete is porous allowing moisture and other contaminants to enter the concrete which can eventually lead to corrosion problems of the steel reinforcement.  If corrosion to the reinforcing steel occurs this will result in the build-up of corrosion generating internal stresses and subsequent cracking and spalling (breaking and falling away) of the concrete. This is demonstrated in the image below.

Source: http://www.corrosion-club.com/

As explained above, when first installed the reinforcement in the concrete does not corrode because the concrete provides a protective alkaline environment due to the presence of large quantities of calcium hydroxide which is produced as Portland Cement hydrates and cures (hardens). (Portland Cement is the most common form of cement used in concrete for general purposes, which is produced from firing a mixture of clay or shale, and limestone or chalk.  The clinker that is produced in the kiln, as a result of the firing process is ground to the fine light grey powder which most people will be familiar with). However, when moisture and other contaminants enter the concrete an environment for a range of different concrete defects is created.

Over the next two weeks I will consider a number of different concrete defects including Carbonation, Chloride Attack, Alkaline Silica Reaction and Sulphate Attack.  Specific concrete defects are difficult to identify from a purely visual inspection, however, armed with the information discussed above and a little knowledge of what to look for it is possible arrive at a reasonable prognosis, which can be later confirmed with sampling and testing of the concrete.

Concrete is a very dense/heavy material and when it starts to exhibit defects that can result in cracking and spalling it can be very serious from a structural perspective as well as a health & safety perspective. The images below provide some examples of what can happen when concrete starts to exhibit defects, some of which I will discuss in more detail next week.

Source: http://www.structurearchives.org/

Source: Source: http://cbiconsultinginc.wordpress.com/

Source: http://stopconstructiondisasters.com/

Please feel free to share this article and other articles on this site with friends, family and colleagues who you think would be interested

Information/opinions posted on this site are the personal views of the author and should not be relied upon by any person or any third party without first seeking further professional advice. Also, please scroll down and read the copyright notice at the end of the blog.

10 Longest Bridges in the World in Pictures

I present below the current 10 longest bridges in the World, where you will note that these are dominated by bridges in China with 7 out of the 10 being located in that part of the World!

A few months ago I published an article, which provided a pictorial record of the World’s current 10 highest bridges in the World (Link). The article proved to be very popular and a number of comments were left asking about the longest bridges in the World.  I therefore present below the current 10 longest bridges in the World, where you will note that these are dominated by bridges in China with 7 out of the 10 being located in this part of the World!

Number 1

Danyang–Kunshan Grand Bridge – Beijing – China - Length - 164,800 metres 540,700 feet – Rail Bridge – Completed 2010

Source: Source: http://glamgrid.com/

Number 2



Tianjin Grand Bridge – Beijing – China - Length - 113,700 metres 373,000 feet – Rail Bridge – Completed 2010

Source: http://afaqahmedjamadar.blogspot.co.uk/

Number 3



Weinan Weihe Grand Bridge – Zhengzhou – China - Length – 79,732 metres 261,588 feet – Rail Bridge – Completed 2008

Source: http://www.dialmenowblog.com/

Number 4

Bang Na Expressway – Thailand - Length – 54,000 metres 177,000 feet – Road Bridge – Completed 2000

Source: http://toptencollections.com/

Number 5

Beijing Grand Bridge – Beijing – China - Length – 48,153 metres 157,982 feet – Rail Bridge – Completed 2010

Source: http://www.dialmenowblog.com/

Number 6

Lake Pontchartrain Causeway – Louisiana – USA - Length – 38,442 metres 126,122 feet – Road Bridge – Completed 1969

Source: http://commons.wikimedia.org/

Number 7

Manchac Swamp Bridge – Louisiana – USA - Length – 36,710 metres 120,440 feet – Road Bridge – Completed 1979

Source: http://www.youbioit.com/

Number 8

Yangcun Bridge – Beijing – China - Length – 35,812 metres 117,493 feet – Rail Bridge – Completed 2007

Source: http://ramadhangj.blogspot.co.uk/

Number 9

Hangzhou Bay Bridge – Hangzhou – China - Length – 35,673 metres 117,037 feet – Road Bridge – Completed 2007

Source: http://steelbuildingshq.com/

Number 10

Runyang Bridge – Jiangsu – China - Length – 35,660 metres 116,990 feet – Road Bridge – Completed 2005

Source: http://www.chinadaily.com.cn/

Please feel free to share this article and other articles on this site with friends, family and colleagues who you think would be interested

Information/opinions posted on this site are the personal views of the author and should not be relied upon by any person or any third party without first seeking further professional advice. Also, please scroll down and read the copyright notice at the end of the blog.

Asbestos - Part 3 – More places to find asbestos in buildings

…..the inspection, identification and testing of asbestos is a specialist activity which is shrouded in a wide range of policies and procedures written into legislation.  It is therefore imperative that specialist advice is sought where there is a possibility of the existence and/or discovery of asbestos or asbestos containing products or components in buildings

Source: http://www.ultimatehandyman.co.uk/

Over the last few weeks I have introduced asbestos and in particular its extensive use in UK construction.  In Part 1 (link) I discussed the health risks associated with being exposed to asbestos fibres and subsequently why asbestos is no longer used in UK construction. I also explained that asbestos containing products/components in buildings only becomes a problem if they are disturbed or become damaged and that there is no need to panic if asbestos containing products/components are discovered in buildings. In last week’s article (link) I went onto explain that asbestos is not easy to identify, even for the trained eye as it is often concealed or decorated, making it difficult to differentiate from other building products/components. I finally gave some examples of the wide use of asbestos cement in UK construction with some images of its typical uses.  In the final part of this three part article I will gives some examples of the wider uses of asbestos containing products and components in buildings, some of which you may find surprising.

It is first worth re-emphasising that the inspection, identification and testing of asbestos is a specialist activity which is shrouded in a wide range of policies and procedures written into legislation.  It is therefore imperative that specialist advice is sought where there is a possibility of the existence and/or discovery of asbestos or asbestos containing products or components in buildings.

Textured Coatings – used as a finish onto ceilings or wall surfaces to give a decorative appearance. Textured coatings that may contain asbestos are difficult to identify from a visual inspection, as many have been painted over. The asbestos fibres are held in place within the coating and are not easily released unless sanded down, or during removal.

Textured coating - Source: http://hawkenvironmental.com/

Floor tiles, textiles and Composites – You may be surprised to learn that asbestos can be found in PVC floor tiles. Discovery is often further complicated as these types of floor tiles are often covered over with newer floor coverings. 

PVC Floor tiles - Source: http://www.mesotheliomahelpnow.com/

As previously discussed in Part 1, asbestos is an extremely flexible material as such it could be woven and spun, allowing it to be used for products such as fire blankets as well as textiles within electrical fuse boxes which allowed additional fire protection behind the actual fuses.

Asbestos fire blanket - Source: http://houseinvestigations.com/

Electrical fuses - Source: http://www.hse.gov.uk/

Asbestos composites allowed asbestos to be used for a variety of products for which typical examples are toilet cisterns and seats, window sills, and bath panels. These are products that many people do not readily associate with asbestos.

Asbestos cistern and seat - Source: http://asbestosadvisor.net/

Spray Coatings - often found as insulation on the underside of roofs and sometimes on the sides of buildings and also used as fire protection on steel beams/columns as well as on the underside of separating floors. Identification of suspected asbestos containing spray coatings is usually made with the presence of a rough surface, white or grey in colour, although painting of a spray coating can make this more difficult to identify. Some spray coatings can contain up to 85% asbestos.  When this is added to the fact that spray coatings can be very friable (break up easily), this use is one of the most dangerous asbestos containing products found in buildings.

Asbestos spray coatings - Source: http://www.asbestostesting.com.au/

Asbestos Insulating Board (AIB) – Can be found in a number of different locations within a building as it was used for a variety of fire proofing applications.  AIB can therefore be found as ceiling panels/tiles, soffit boards, partition walls, lift shaft linings, panels within fire doors amongst other applications.

Asbestos insulating boards - Source: http://www.ekii.co.uk/

Lagging and Insulation – Mostly found as insulation around heating pipework and has many different appearances, which is commonly a fibrous material that can break up easily. When applied to pipes it is often covered with a protective coating, which can be a variety of different colours that sometimes makes it difficult to identify. As with spray coatings, this is a particularly dangerous form of asbestos.

Asbestos pipe lagging - http://www.topasbestosremoval.co.uk/

Loose Fill Asbestos – used as insulation and found in cavity walls, in floors and loft spaces. Due to its loose nature this is possibly the most dangerous form of asbestos used in buildings.  Its appearance is blue/grey in colour or sometimes off white and is often made of pure asbestos.  Although much of this form of asbestos has now been removed it is still likely to be discovered and should only be inspected and dealt with by a specialist wearing and using the correct protective equipment.

Loose fill asbestos in roof space - Source: http://www.torontorealtyblog.com/

The information and images discussed above and within last week’s article provide some typical examples of the use and identification of asbestos containing materials and components within buildings.  Please bear in mind that the examples provided are far from exhaustive and asbestos can be found in numerous other locations within buildings.  Having said this I hope these articles have provided a good introduction to asbestos is buildings.

Please feel free to share this article and other articles on this site with friends, family and colleagues who you think would be interested

Information/opinions posted on this site are the personal views of the author and should not be relied upon by any person or any third party without first seeking further professional advice. Also, please scroll down and read the copyright notice at the end of the blog.

Asbestos - Part 2 - Where to find asbestos in buildings

Asbestos in buildings is not easy to identify even for those with experience of buildings and construction.  This is not only due to the vast use of asbestos in buildings but also due to the fact that it is often concealed or decorated, making it difficult to differentiate from other components/products

http://www.house-extension.co.uk/

In last week’s article (Link) I discussed the many positive characteristics of asbestos, which led to the extensive use of asbestos in UK buildings for a wide variety of components/products.  I also explained that due to the serious health risks associated with either working with or being exposed to asbestos fibres, that asbestos is no longer used in building construction in the UK.  Having said that asbestos was so widely used in UK buildings particularly between circa 1950 to 1980 that it’s discovery in buildings is still highly likely today and something that will continue to be an issue well into the future.  It is therefore worthwhile trying to understand how to identify asbestos and where it may be discovered in buildings.

The first thing to make clear is that asbestos in buildings is not easy to identify, even for those with experience of buildings and construction generally.  This is not only due to the vast use of asbestos in buildings but also due to the fact that it is often concealed or decorated, making it difficult to differentiate from other components/products.  The only real way of knowing whether something that may be suspected as asbestos is actually asbestos is to have the component/product tested.  There are very strict procedures for sampling and testing of asbestos as set out in the Control of Asbestos Regulations 2012, which will require the services of a specialist.  As you would imagine this can sometimes prove to be costly, however if you do not follow the legislation you are obviously breaking the law and secondly, possibly compromising the health of yourself and others. 

Without wishing to go into too much technical detail for this article there are six different types of asbestos that may be found in UK buildings; Amosite, Chrysotile, Crocidolite, Tremolite, Actinolite and Anthophyllite, for which the first three were the most commonly used in UK construction. The health risks associated with all types of asbestos are very similar however Crocidolite, sometimes referred to as blue asbestos is considered to be the most dangerous of all.  As stated previously, in order to establish whether asbestos is present and if so which type it is it will be necessary for sampling and testing to take place in accordance with the procedures detailed in the Control of Asbestos Regulations 2012.

So where is asbestos likely to be found in buildings? Interesting the answer is pretty much anywhere!  Remember asbestos is not easy to identify so an awareness of where it was used will help those to identify ‘suspected’ asbestos and recommend subsequently sampling and testing to confirm the presence of asbestos, or not.  Asbestos cement products are discussed below and in next week’s article I will provide some further typical examples of where asbestos may be found in buildings. Also, if you want to undertake further research into the uses of asbestos in UK buildings then you will find that the examples provided in my articles are far from exhaustive.

Asbestos Cement - Asbestos cement is ordinary cement mixed with asbestos, in some cases the asbestos can make up over a third of the overall content however, typically however the overall asbestos content is often much lower.  Asbestos cement is generally considered as one of the lower risk asbestos products as the asbestos fibres are effectively held or ‘trapped’ within a ‘rigid’ component, once the cement, water and asbestos has cured (hardened).  Asbestos cement products start to become a problem if they become damaged or disturbed, so it is worth knowing where these could be found.


The photographs below demonstrate that asbestos cement sheeting was a very popular way of providing roof coverings for outhouses and garages in domestic buildings as well as roof and wall cladding for industrial or low specification commercial buildings. Asbestos cement roof and wall cladding sheets are usually identified by their distinctive ‘corrugated’ form and their dull grey colour, (although the colour can sometimes be affected by the impact of weathering and decorations):

Source: http://www.roofersinedinburgh.co.uk/

Source: http://www.asbestostesting.com.au/

Associated with asbestos cement roof and wall cladding sheets were also products such as asbestos cement rainwater downpipes and hoppers. Hoppers are located at the top of a rainwater downpipe, or at the junction of a number of rainwater pipes, as detailed in the image below: 

Source: http://www.hse.gov.uk/

Due the excellent fire resistant properties of asbestos, asbestos cement was often used for flue pipes for boilers and heaters.  This enabled combustion waste products, often at high temperatures to be discharged from a building safely and with minimal risk of fire. Asbestos cement pipes were also used for air conditioning and ventilation systems:

Source: http://www.bsafeconsultancy.co.uk/

Source: http://www.biacs.co.uk/

Asbestos cement products and components were used and installed in UK construction for many years and are arguably the most commonly used asbestos product installed.  There were however many other uses/applications of asbestos in UK construction and next week I will provide some examples of these wider applications and how they may be identified.

Please feel free to share this article and other articles on this site with friends, family and colleagues who you think would be interested

Information/opinions posted on this site are the personal views of the author and should not be relied upon by any person or any third party without first seeking further professional advice. Also, please scroll down and read the copyright notice at the end of the blog.

Asbestos - Part 1 - Is asbestos really a problem in buildings?

Despite popular belief the discovery of asbestos containing materials in a building does not need to be a serious problem.  There is nothing written in the Control of Asbestos Regulations 2012 that states that asbestos must be removed from a building

Source: https://www.nachi.org

Most of the publicity that asbestos has received for many years is negative and would have us believe that anyone who works or occupies a building that contains asbestos are at significant risk, however this is far from the truth. It is also true to say that those who worked with asbestos, whether it’s extraction or use/installation in buildings and were oblivious to the associated health risks at the time are those who are suffering asbestos related diseases such as Mesothelioma, Lung Cancer, Asbestosis and the like for which many have sadly died.  Having said that, the answer to the article title is quite simple, Asbestos is not a problem in buildings as long it is identified, managed and controlled.

Before delving into the many publicised problems with asbestos it is first worth understanding why its use was so popular and why it is still found extensively in buildings throughout the UK.  Asbestos was such a versatile and durable mineral that it lent itself to so many different uses in buildings due to its many positive qualities.  You may be surprised to learn that Asbestos has been used for many centuries in different forms throughout the World however its use became much more widespread in the UK from the early part of the twentieth century and was extensively used in UK buildings between 1950 and 1980. In fact asbestos is still used in some countries today despite the many know health risks associated with it.  There are still vast amount of asbestos deposits present around the World which are extracted using mining techniques which are much the same as processes used for extraction of other minerals.

Source: http://www.nzdl.org/

Positive qualities of Asbestos for use in buildings - Asbestos is chemically inert which means that it does not react with other chemicals, it is heat resistant making it non-flammable even at high temperatures, it is alkaline and acid resistant, water resistant, strong in tension, flexible (it can be used and made into rigid components or spun and woven like cotton), it has no detectable smell, it is resilient and can last for many years and it is extremely resistant to abrasion.  All in all, when you read through these qualities it is easy to see why asbestos was so popular and used for so many different products/components in buildings.

For a number of years in the UK asbestos has been classified as a ‘deleterious material’, which is defined by Longworth Consulting as ‘materials or building techniques which are dangerous to health, or which are environmentally unfriendly, or which tend to fail in practice. Often listed in property agreements, appointments and building contracts where the developer, consultant or contractor is required not to use them’.  The Health & Safety Executive’s (HSE), ‘Working with Asbestos in Buildings’ leaflet identifies the point at which asbestos was banned from use in the UK, ‘blue and brown asbestos (the two most dangerous forms) have not been imported into the UK for nearly 20 years and their use was banned in 1985. White asbestos was banned (except for a small number of specialised uses) in 1999’. Therefore, although asbestos has not been used as a building component/produce for nearly fifteen years we are still seeing deaths and serious illnesses as a result of exposure to asbestos many years ago.

The positive attributes of asbestos described above are conversely the main reasons why asbestos related diseases are nearly always incurable. Working on or near damaged asbestos-containing materials or breathing in high levels of asbestos fibres, which may have been many hundreds of times that of environmental levels could increase the chances of getting an asbestos-related disease.  Due to asbestos fibres being so hard to destroy, the body cannot break them down or remove them once they are lodged in lung or body tissues. They remain in place and over a period of time they can cause disease.  There are many instances where asbestos related symptoms have not manifested themselves for almost 30 years, however this will also depend on the general health of an individual, which can significantly reduce the point in which symptoms will show themselves. 

Source: http://globalnews.ca/

Although the above may seem to be alarmist the truth of the matter is that asbestos containing materials in buildings are perfectly safe as long as they are identified, managed and controlled. Asbestos will only become a problem in buildings if it is disturbed or becomes damaged.  Despite popular belief the discovery of asbestos containing materials in a building does not need to be a serious problem.  There is nothing written in the Control of Asbestos Regulations 2012 that states that asbestos must be removed from a building, in fact If existing asbestos containing materials are in good condition and are not likely to be disturbed, they may be left in place as long as their condition is monitored and managed to ensure that they do not become damaged.

Over the next few weeks I will provide some guidance of the many uses of asbestos in buildings and also provide some examples of where you may find asbestos in a building. For those who are not familiar with asbestos I suspect that some of the uses will come as a surprise.

Please feel free to share this article and other articles on this site with friends, family and colleagues who you think would be interested

Information/opinions posted on this site are the personal views of the author and should not be relied upon by any person or any third party without first seeking further professional advice. Also, please scroll down and read the copyright notice at the end of the blog.