Cold-mix asphalt for road foundations: use of cement and foamed bitumen in "high performance" pavements

The reduced availability of traditional aggregate, increasing environmental sensitivity and the high intrinsic value of marginal materials from the milling of the old damaged road pavements, have in recent years justified growing interest in “cold recycling” as a technique which can be used in the construction or rehabilitation of pavements, in spite of the use of “poor” materials. Cold recycling can be developed by means of cement and foamed bitumen. The technique gathers the benefits of the cold in situ recycling and those related to the use of the foamed bitumen. Despite its undisputed advantages, the above-mentioned technique has not yet been supported by a consolidated experimentation in Italy that attests to which factors could mainly affect the performances of the foamed mixture. The paper describes an investigation aimed at testing foamed mixtures to be used in major roads. In particular, the influence of moisture, temperature and fine content on the mechanical performances of the material have been checked. The results demonstrate that pavements with cement and foamed bitumen foundations can be compared – in terms of bearing capacity and durability – with flexible pavements, on the basis of the Italian Design Pavement Catalogue.