Soil Stabilisation in Construction
Stabilised Soils on Construction Sites
Stabilising construction sites using cement as a soil binder is an extremely cost effective method of converting difficult or lightly contaminated soils into construction materials.
Most soils including most lightly contaminated soils found on site can be recovered and improved using cement or lime.
By using 'on site' soils or materials, construction can be carried out cheaply and quickly.
In addition, the use of site won materials will lead to significant savings in lorry movements and big reductions in the environmental damage that this causes to the surrounding area.
Recycling in-situ offers the potential for reduced environmental impacts otherwise associated with the extraction of primary aggregates, transportation of materials and land fill with all its escalating tax implications.
Whilst cement/lime stabilisation has been used for some time it's effectiveness in all but ideal conditions can be difficult to predict and sampling and testing must be carried for each and every application.
There is now a proven cement additive available in the UK which takes all the guesswork and risk out of cement stabilisation.
PowerCem, available as RoadCem, ConcreCem, ImmoCem and NucliCem is designed to enhance and increase the strength and flexibility of all cement bound materials. As little as 1% will dramatically improve the overall performance allowing previously untreatable soils and waste streams to be kept on site and used for construction.
Early establishment of stabilised working platform provides a safe and sufficiently durable working surface from which construction plant, such as piling rigs and cranes can operate.
Platforms are essential when in situ soils give insufficient support or if the existing ground conditions are wet or contaminated, and good design can ensure maximum efficiency of all future construction processes.
Clear economic and environmental benefits can be derived from the use of platforms, particularly:
- Where increased use can be made of
either site-won or recycled materials
- When platforms can be used and re-used and/or re engineered for a variety of purposes throughout the construction process
- When platforms can become permanent works.
Examples can be found of stabilised working platforms formed by treating the existing site soils that are utilised many times through a construction site life-cycle; they may provide support for the ground works plant, early temporary access roads, avoiding degradation or improving the existing sub soils to enable them to be used for purpose engineered sub base, act as form work for casting pad foundations, provide a surface for steelwork erection and act as a structural element within a floor slab or pavement.
Our stabilised bound product can be produced by either ex situ or in situ methods.
- Soils or granular materials can be mixed with our binding compound in a stationary mixing plant and the resulting product placed and compacted by non-specialist plant. Plant for laying and compaction of our product is similar to that required for the laying and compacting of other paving materials such as unbound layers or bituminous bound products.
- The blending process for our recycled product can be carried out using a nearby "fixed plant" off site or "mobile plant” working within the project area, when space and through put volume allow.
- Alternatively, surface soils on site can be mixed in-place with our binder using specialist plant such as binder spreaders and rotavators, before compacting.
A competent person from Soil Stabilisation Solutions will be able to estimate the likely volume/percentage of binder required from a visual examination of the site materials; this can be carried out initially so that a decision can be made, on economic grounds, on whether to proceed with the laboratory testing of the site soils. From which we will provide you with a firm price and a guaranteed result.
Some materials are difficult to stabilise because they are unsuitable chemically or may require excessive mechanical modification. Peat and other organic soils can delay the curing of the product and unless RoadCem is added to the cement bider.
RoadCem can cope with other difficult materials such as Sulphate rich soils which can cause swelling and disintegration of cement-bound layers and clays/chalks which other binders have difficulty drying.
Unlike other alternative stabilisation methods our product can still be effective up to -10 Cen.
Seasonal working is no problem at all and normal summer and winter weather is not going to hold up work.
The approach to platform design should be related to the risks which have been identified in connection with the plant for which a platform is required and with the operations to be carried out, as well as the pre-existing soil conditions.
A simple design approach for working platforms may be appropriate for many routine temporary cases. Where the stabilised layer also forms part of the permanent works, a design method appropriate to that end use should also be carried out.
The design of a working platform is a geotechnical design process and should be carried out by a competent person.
The designer should have full access to the health and safety plan, including the desk study and all other site investigation information. This information we provide is not intended to replace or reduce the designer's input, but rather to inform and educate the designer and his team of alternative and new developments.
The platform level may be dictated by construction requirements rather than the final design of the permanent structure.
This should be considered early in the design and construction process to ensure that where possible working platforms can be re-used for other purposes.
Attention needs to be given to the edges of working platforms. It should be determined how near the edge of the platform plant and vehicles can be permitted while avoiding instability.
With other stabilisation system platforms a minimum distance of half a machine width is usually required for tracked plant to avoid degradation and break off, with our additive this is not such a critical factor as the bound material will very quickly attach itself to the base on which it is laid and also to the surrounding ground, as the copolymer molecules (seeking out any moisture) form bonds between the platform and surrounding soils.
Sloping sites do present particular problems for stability, and these inherent problems should always be addressed in the platform design.
Generally for site platforms our binder will be added to achieve strengths of around 2N/mm2 (strength class C1.5/2.0) which has been found reasonable for platforms for most construction activities.
Different construction processes carried out on or through the platform may impose greater strength requirements that need to be taken into account in the design and this is can easily be engineered in to the product.
A platform that is very strong though may form an ideal running surface for plant but may cause problems in the construction process if drainage runs cannot be cut out of the base. We feel our product is unique in this aspect as the bound strength increases without becoming rigid or inflexible and is still workable up to high strength levels.
Our bound product does have very low permeability, which is beneficial from a construction point of view, preventing water and therefore frost from penetrating the base. Drainage design will therefore be critical, to ensure that the platform remains suitable for use and will not carry standing water.
In general this can be carried out by careful construction of the platform layer. Falls can be constructed into the platform by means of grading during final compaction.
In all cases the requirements of the construction timescale should be taken into account - winter working may require drainage design for heavier rainfalls and account taken of the raising of the water table beneath the platform.
Similarly ice forming on the platform due to the presence of standing water can render construction activities dangerous.
The incorporation of the platform into the permanent works can save significantly on cost.
Where this is pre-planned there is a tendency on site to take greater care of the platform if it is seen as part of the permanent structure.
Examples of subsequent uses of the platform may be:
- Re-use as temporary works for later construction activities, such as use of the platform for form work
- Re-use as pavement layer, for car parking and access roads
