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There have been no updates on the site recently due to prolonging proceedings of the concrete technology board. However, it was a time well spent. There were many great discussions about cement related research that could spawn many new, exciting products. In the coming weeks, many new articles will be posted and the topics will vary greatly.

Report on foam concrete durability

The fundamental principle behind the development of foam concrete has always been the drive the optimize the strength of low density materials. Although foam concrete is currently used in many countries, there is a basic lack of research on its durability when made from locally available materials. What is inside the scope of this paper, is to present the conclusions of research programs and studies on some indicators that make it clear whether the material being produced is of adequate quality or not. What is more, the paper also contains conclusions about the durability of foam concrete, which is itself, a very interesting topic. Furthermore, there is a need to investigate the influence of admixtures and other materials on foam concrete. One such material, that has seen a lot of interest lately is fly ash. Its effect on the durability of foam concrete has been thoroughly studied.

The durability of foam concrete is very strongly connected with phenomena, such as water absorption, permeability and porosity. The permeability of foam concrete is usually very high compared to traditional concrete. The exact parameter depends on the structure of air bubbles inside the material. Mix proportions also play a very important role in determining this parameter. It has been found, that for regular types of concrete, the differences in water resistance are typically small and rather negligible. However, for foam concrete, the situation is rather different.

The observations carried out during the experiments revealed that there are large differences between samples, which have been tested for gas permeability. More precisely, it has been found that foam concrete can be as much as 20 times as gas permeable compared to other types of concrete. This observation has been thus far confirmed by many independent research groups worldwide. The research programs also led to some other interesting discoveries. It was found that foam concrete may have significantly larger paste volumes, but is much less permeable in comparison to autoclaved aerated concrete.

The low water to binder ratios can have a dramatic influence on the performance of foam concrete mixes. Also, the wide use of materials with cementing properties can largely redefine the pore structure of the foam concrete we know today, by making it much more durable. Many researchers have observed that introducing other binders into cellular concrete mixes can be beneficial. Extra fine powders in the paste can result in a substantial improvement of flowability.

Foam concrete for bridge abutments

Traditionally, bridge abutments have always been a problem for the construction industry. They pose many challenges during their construction and can significantly delay the time needed to complete the whole project. Aggregate compression under the bridge can be one of those problems. Under normal circumstances, sand is typically used to mitigate this problem. However, this may cause excessive pressure on the side walls, which usually forces the designers to increase the wall thickness, so that they can withstand the weight imposed by the sand. Without this procedure, the lateral forces imposed by the sand could cause the bridge to fail prematurely.
All of this causes many problems, the biggest of which is, of course, money. Thick walls, expensive infrastructure can be very costly and time consuming to build, but also very costly to maintain. Another possible solution is to build the bridge using traditional materials only. There are two main areas that may pose a problem in this scenario. The first is that the soft ground upon which the bridge would be based can eventually compress, causing subsidence, that would lead to significant cracking in the structure of the bridge. The weight imposed by the aggregate on the soft ground is the reason for this phenomenon. The second problem is that the aggregate itself can also subside also causing the problems described above.

These problems can be aggravated even more if building on softer grounds such as peat, for example. All of them can however be reduced using foam concrete. The major benefits of using it are: lower labor costs and much shorted construction times. The biggest advantage foam concrete has over other materials and methods is that it can be adapted to specific requirements of a particular job. It is therefore an extremely versatile material. By selecting the right combination of source materials it is possible to achieve properties that fit the design as well as possible. Adapting foam concrete to local conditions is very easy, which permits the design team to have as much freedom as possible.

- Loose aggregate is known very well for settling into soft soils. A very good method for eliminating this problem is simply using foam concrete in its place. The reason why it is a better material is that it is a continuous surface, that is not broken up into many pieces. This allows the material to distribute the weight across the whole surface area, which eliminates the problem of settling into soft ground.

- With sinking and settlement virtually eliminated, road subsidence is not a problem as well. Therefore, the amount of work necessary to maintain the bridge after it has been build is significantly reduced. Because of this, the total operational cost during the lifetime of the bridge is also drastically reduced.

- The lateral forces imposed on the side walls are reduced, thus making it possible to build much thinner walls, meaning much lighter foundations. The savings that can be achieved using this method are immense.

- Because foam concrete has load spreading capabilities, it is possible to pour the material gradually, with each larger poured on the of the previous being stronger. This allows significant cost savings, as the bottom layers do not need to be as strong as the top ones. This is achieved simply by using less cement while pouring the bottom layers, and using less while pouring the top ones, which will carry more weight.

It is clear that foam concrete not only offers excellent performance, but also cost savings. It allows the design team to use less pillars than traditionally and allows the contractor to complete the project faster and cheaper.

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