Lime stabilisation and modification is the addition of binder product (usually quicklime) to the host material which reduces moisture dramatically turning the unusable material into a valid construction material with a 5% CBR.
Cement Stabilisation refers to the addition of cementitious binders (Portland Cement, FlyAsh, GGBS) to a host material to give increased strengths and long-term durability.
When adding cementitious binders to existing in-situ materials then more stringent contractor on-site checks must take place (including working temperatures) alongside the Compliance Testing Regimes which are undertaken by an independent laboratory.
The amount of binder to be applied has to first be determined and this will depend on the overall end CBR requirement. Representative samples of the host material are collected and taken to a UKAS accredited laboratory where a mix design exercise is carried out to determine this optimum binder addition. Once works commence on site regular spread checks take place to confirm that the amount of binder determined within the design had been applied to the host material.
How does Soil Stabilisation work?
Soil Stabilisation has a wide range of benefits and attractions in today’s construction industry. The process of lime modification and soil stabilisation typically consist of four levels:
1) Lime Improvement / Bulk Modification (5% CBR)
The lime modification process involves the addition of small amounts of binder (quicklime) to the host material to substantially reduce moisture content transforming the wet/unsuitable material into a useable and compactable construction material with a 5% CBR.
2) Capping Replacement Layer (15% CBR)
To enable the formation of a capping replacement layer, binders (quicklime and cement) are incorporated into the host material along with the addition of water. The material is then compacted and trimmed leaving a layer with a 15% CBR. This treatment level can also be used as a Piling Platform.
3) Sub-base Replacement Layer (30% CBR)
Additional binders are incorporated into the material giving a stronger, more durable end product with non-frost susceptibility and a 30% CBR.
4) HBM Layer (Hydraulically Bound Mixture)
Cement is introduced into the material giving high mechanical strength for wearing resistance. After trimming to tight tolerances the end material can be directly overlaid with blacktop.
The Benefits of Soil Stabilisation
Treatment with lime (lime stabilisation) and/or cement (cement stabilisation) allows production of a long lasting and stable material comparable to those of graded aggregates. Hard wearing, with greater stiffness and strength they provide excellent performance within the construction process and have become widely recognised as a strong alternative to typical construction methods.
The recycling and re-use of insitu materials gives significant savings, as it minimises the stripping and removal to landfill of material along with their associated transport costs and also saves on the import of aggregates.
In addition to this, the duration of the works are also shorter, giving further savings to the contract program.
There are significant environmental benefits of soil stabilisation in comparison to traditional construction methods including energy savings by reducing the transport of materials (this also reduces the indirect effects including nuisance to the public), minimising the use of aggregate resources and utilising some binders that are by-products of the energy industry.