Rehabilitating a road in China, using non-traditional road equipment.

We recently rehabilitated a section of a haul road, in a sugar cane plantation near Laibin in Guangxi Province, in Southern China.  This haul road carries approximately up to thirty to fifty, two axle, trucks ranging from 10 to 30 ton loads per day.

The road was treated with CBR PLUS to improve its performance in both wet and dry weather and most importantly to reduce maintenance. Typically, when untreated, these roads have to be rebuilt once a year or at times even more frequently.  The area is also prone to high rainfall with a monsoon season and during the sugar cane harvesting season, there is rainfall almost daily.

The soil is reddish brown, silty clay, with 15% coarse material content in the range of 2 to 10 mm sized particles.  The rest of the soil is very fine grained and contains some very fine-grained silt and clay.  The liquid limit 42.7, plastic limit 23.7, plastic index is 19%. Actual clay content is 33%.

In view of the high axle loads and essentially a good sub base, it was decided to scarify and treat to a depth of 20 cm.  The dosage rate of the CBR PLUS was 0.008 liters per square meter. 

The first step was to clear and reshape the road with the drains being cleared and formed at the same time.  Three hoes were used for this purpose.  The hoes were then used to break up the surface of the road and break lumps to a depth of 20cm.  Half the dosage amount of CBR PLUS was poured into the water tanker and sprayed onto the road surface.  The layer was then scarified using a tractor and rotary hoe, which mixed the layer and broke down the larger lumps.  The rest of the CBR PLUS/water mixture was then sprayed onto the surface and the layer was then scarified again.

Final shaping was done with a hoe and some hand labor.  The layer was then compacted with a smooth drum roller compactor.  The road was then sprayed twice a day with a light application of water to cure.

 Road Before Treatment

Clearing and Shaping

 Adding CBR Plus to Water in Tanker

 Spraying CBR Plus / Water mixture onto the road

Tractor & hoe scarifying and mixing soil

 Final Shaping

 Compacting

Completed road

By: Reinhold Rohrs

President of Rhide Technologies Inc.

www.cbrplus.com / www.gravelock.com

Soil Stabilizers

I would like to make some points to try to explain ionic soil stabilizers. 

Soil stabilizer is not the correct term, but it is the one commonly used.  Compaction aid or soil consolidation aid are the more correct descriptive words, but the soil is modified and performance is much more stable in high clay soils – so the term stabilizer does apply.

In order to be able to conduct some performance testing on treated soil, one needs to understand the way in which the product reacts with the soil.  Clays contain certain cations with an ionic imbalance, and in nature the way this ionic imbalance is satisfied by water.  These cations attract and “hold on to” a large number of water molecules, called adsorbed water, which surround the clay particle and these water molecules can only be removed by high pressure or temperature e.g. in a potters kiln.  The fact that you try to compact water coated molecules reduces particle interlock and so reduces strength, this is usually referred to as plasticity.

The ionic stabilizer exchanges these cations in the clay with ones that are in ionic balance and the adsorbed water that was previously held onto by the clay is now released and has to make its way up to the surface of the treated layer to evaporate from there. This water release takes time and depending upon the soil type, traffic and weather conditions can take up to 30 days.  During this time, the treated layer becomes more dense as well as drying out and so increases in strength. Depending upon the product used the soil will not re-adsorb the water as it has previously and therefore exhibit higher strength even in wet weather.  In essence the effect is one of the reduction in susceptibility to moisture of clay based roads.

The treatment is non cementitious like lime or cement or other methods like polymers. So the soil will achieve it natural strength rather that that provided by the above methods.

In testing the effects of this treatment, one has to prepare two sets of samples, one treated and one untreated.  Both samples have to be let to dry out for 10 to 20 days and then tested and a significant improvement in the treated samples will be noted over the untreated samples. 

By: Rhino Rohrs

www.cbrplus.com / www.gravelock.com