SubscribeDuring early 2006, Foam Concrete Ltd was approached by Fitzpatrick Contractors Ltd to manufacture and supply foam concrete as the sub-base for a road through a new industrial estate being constructed in Hertfordshire.
Location: Hoddesdon, Hertfordshire, UK
Main Contractor: Fitzpatrick Contractors Ltd
Structural Engineer: T R Collier & Associates Ltd
Foam concrete has been used successfully in (road) construction around the world, for a number of years. This versatile material is highly suitable for all kinds of civil engineering applications. Its various volumetric masses of between 250 and 1,600 kgs/m3, compressive strengths of between 0.2 and 12.0 N/mm2, rigidity, thermal insulation
and water absorption properties in particular, promote its application in tailor-made structures.
Lightweight Foam Concrete: Tensile / Compressive Strength
The sub-soil on site comprises peat and is subject to flooding due to high groundwater levels in the area. Indeed because of this, the site required extensive de-watering both prior to and during construction. Traditional construction
was ruled out as repeated wet/dry cycles could eventually result in 'heave' and consequent damage to the finished road. A road structure in which foam concrete is used nearly always aims at limiting deformation of the sub-grade of both the structure and any adjoining structures. Future maintenance costs are therefore minimised.
Fresh foam concrete conforms to the subsoil and after hardening, provides a superior, monolithic structure with advantageous mechanical properties: As well as having a tensile strength of around 10 to 15% of its compressive strength, at densities below 1,000 kg/m3, foam concrete has the capacity to 'float' (see diagram overleaf), providing the contractor with a stable sub-base on which to place a granular capping layer - such as Type 1 - and finally an asphalt wearing course to complete the road. Correctly designed and constructed, the finished structure will be able to
withstand any subsequent movement of the sub-strata.
Simple logistical advantages together with the rapid production rates achievable are two of the major benefits of using foam concrete and these were both crucial in Fitzpatrick's decision to use Foam Concrete Ltd as their supplier. The technically advanced on-site batching plant operated by the Kent-based company, is able to produce around 400m3 of lightweight foam concrete in an average day. In addition, the plants' remarkable performance allows its crew to pump foam concrete over distances of more than 500 metres in any direction from the plant location and in doing so, minimise disruption caused by having to re-site equipment during a pour.
Foam Concrete Energy Absorption and Construction Cost Savings
Advantages of using foam concrete for road construction:
Ease and speed of placement
When judged against other more labour/time intensive methods, the ability to produce quantities of up to 400m3 a day means that construction times can be significantly reduced, with consequent cost savings.
Total void-fill
The flowing, self-compacting properties of foam concrete mean that you can be assured that all voids are completely eliminated.
Good energy absorbing qualities
As the foam concrete is compressed during the collapse or subsidence of material above, due to its
cellular structure, the resistance of the foam concrete increases, absorbing the kinetic energy.
Susceptibility to breakdown
Unlike some synthetic lightweight foams (polystyrene for example), hardened foam concrete is not
susceptible to breakdown due to the presence of hydrocarbons, bacteria or fungi. It is insect,
rodent and fireproof.
Environmentally sound
Using Foam Concrete Ltd''s on-site batching plant means less traffic disruption both on-site and in
the surrounding area. Around 109m3 of 400 kgs/m3 density lightweight foam concrete can be
produced from one bulk powder tanker delivery, making it safer for site-workers and local residents
as well as being friendlier to the environment.
Principle of Equilibrium
By replacing the weight of the excavated soil (W1), with a similar or lower combined weight of foam concrete and construction (W2 + W3), the completed structure will be stable and able to resist any subsequent movement of the sub-strata.
 | We are able to pump foam concrete over distances of more than 500 metres in any direction from the batching-plant.... |
| ....which means less disruption to your site operations |  |