POINTS TO CONSIDER IN ENGINEERING SPECIFICATIONS FOR AGGREBIND POLYMER STABILIZED ROADS, USING ONLY ON-SITE MATERIALS.
It is now generally accepted internationally that there is an urgent need to investigate new solutions for the construction of roads and this is achievable using AggreBind utilizing cross-linking polymers which coats the aggregate and results in soil stabilization. The future availability of graded aggregates is now causing some concern as they are expensive, environmentally damaging to transport, and there are limited stocks available for use in the future. The answer is to use locally available on-site sub-soils and other readily available materials, like non-potable water, crushed construction waste etc, and to stabilize the road with water based environmentally safe polymers. AggreBind is formulated with cross-linking polymers which are water-based polymers, to enable and implement soil stabilization with impressive results.
On-site sub-soils are, however, subject to many variations over the length of the road to be soil stabilized and this must be investigated, and evaluated, before preparing any specifications.
- Take samples of the available sub-soils at regular intervals over the entire length, and proposed layer depth, of the road to be soil stabilised.
- Check the moisture level of the sub-soil. Dry the sub-soil and carry out a sieve analysis. Determine the Optimum Moisture Content (OMC) for the sub-soil.
- The sieve analysis will indicate the percentage of fine soils that pass through a 0.63 sieve. It will also provide an analysis of the stone content in the soil, paramount for soil stabilization.
- If desired, the sub-soil can now be classified against the International ASSHTO standard that provides an indication of the properties of the soil for Soil Stabilization.
- The layer below the soil to be stabilised must be investigated to determine its bearing capacity and also to check if there is any in-situ water. Any sub-base problems must be corrected before the road is stabilised.
- The ideal grading for the layer to be stabilised is 35% fines and no stone larger than 20% of the layer depth. Subject to the type of installation machinery available, and the quality of the stone in the road, additional fines may be produced during the crushing of the on-site soil. Cement or crushed construction waste can be used to produce more fines.
- Subject to the on-site conditions below the layer to be soil stabilised the normal layer depth is 150mm for loads of 80 tonnes and 200mm for heavier loads
- The polymer dosage rate will be between 3ltrs and 5ltrs per cubic mtr of soil treated and the water addition will be calculated when the moisture content of the soil is determined at the time of the installation. Ideally, the combined polymer/water addition should be sufficient to wet the soil to +/- 10% above the moisture level required for compaction. This ensures that all the fine soils are coated with the polymer. The soil should then be worked with the grader to bring the moisture level required for compaction. IF THE SOIL IS ADHERING TO THE ROLLER IT IS TOO WET. KEEP WORKING THE SOIL TO REDUCE THE MOISTURE LEVEL. IF THE LAYER IS TOO DRY FOR COMPACTION THEN SPRAY WITH WATER.
- If it rains during installation wait until it stops and then keep working the soil to bring the moisture back to a level for compaction. THE POLYMER WILL ONLY SET WHEN ALL THE WATER HAS BEEN RELEASED AND SUBJECT TO TEMPERATURE IT WILL CONTINUE TO CURE FOR +/- 28 DAYS.
- Ideally the road should be sealed immediately after compaction with a mixture of 1 part polymer to 3 parts water at a rate of +/- 0.25ltrs per sq mtr.
NOTE: Based on Soil Stabilization installations in a number of Countries a mix of 1 part polymer to 7 part water sprayed at a rate between 3.60 ltrs to 5ltrs per sq mtr X 150mm deep (subject to variable fines and moisture content) produces good results.
Standard road compression testing equipment can be used to determine the compressive strength of the layer during and after compaction Soil stabilization(stabilization) is the core function of AggreBind, it is referred to as ‘green soil stabilization because of its unique environmentally friendly properties. AggreBind is a soil binder comprising cross-linking polymers that are extremely effective when stabilizing soil. Soil stabilization can be implemented on, dirt roads, gravel roads, rural roads, haulage roads and so much more