Road base stabilisation: performance improvement and pavement life cycle consequences

It is well known that soil or/and base stabilization can result in an effective pavement rehabilitation technique. Indeed, they can provide public and private sectors with a strong, durable base capable of withstanding a wide range of traffic loads. Hydrated lime, quicklime or/and cement are used to improve the characteristics of the soil subgrade and/or the aggregate base course underneath the pavement surface. Improvements leading to longer life pavement are generally categorized as subgrade or base stabilization when, for example, a higher quantity of lime, typically 5-8% of the dry weight of the soil, is used. On a chemical standpoint, lime stabilization generates a long term pozzolanic strength-gaining reaction between lime and the silica and alumina minerals solubilized at high pH from the clay, forming calcium silicates and calcium aluminates. In cement stabilization, as the cement hydrates, a gel is formed that upon hardening forms a cellular matrix that encapsulates the soil particles or forms strong bridges between the aggregates. As a result, stabilization originates improvements in CBR, in resistance (e.g. unconfined compressive strength) and resilient modulus. Freeze-thaw resistance is usually increased too. Although pavement durability is usually increased, many drawbacks can arise. Stabilization can be costly and economically not feasible and many consequences can be originated in case of particular soils or when high traffic volumes are present. In the light of the abovementioned facts the objectives and scopes of this paper were focused into the quantification of benefits and drawbacks associated to a case-history. Criteria previously established for the assessment of the technical sustainability were employed. The analysis indicated that under given conditions soil stabilization can have a considerable and positive impact on life cycle cost.