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The paper reviews current knowledge of damage by soluble salts to thin bituminous highway and runway surfacings in warm climates. It critically examines the various recommended maximum salt limits for materials in highway construction and reviews preventative and remedial practices.The study included a laboratory simulation of salt damage using climatic cabinets to identify the cause of salt damage to thin bituminous surfacing of a runway in the West Indies.The work shows the importance of linking relationships and influences of geology, hydrogeology and construction practice with material and salt types, migration and crystallization pressures, crystal properties, hydration/dehydration and climate in order to prevent damage occurring.The term soluble salt is generally used to describe those salts which are relatively soluble in water and

The USA field experiences in the 1960s with lime treatment of marginal materials for pavement layers resulted in the introduction of a ‘mellowing’ period of between 24 and 72 hours, after mixing and prior to final compaction. This period facilitates reaction between the soil and the lime so that pulverization criteria and compact-ability can be achieved. As a result of these early experiences, the ‘mellowing’ period has become an integral part of specifications for lime-treatment processes used globally but it has been based on limited scientific justification. Under the Department of Transport (DoT) Specification for Highway Works (1991 and 1993 amendments) a ‘mellowing’ period of between 24 and 72 hours is mandatory. This period of mellowing is also recommended in volume 4 of the Design Manual for Roads and Bridges HA/74/95. 1 Part 1 of this paper, 2 also presented in Transport, discussed results of a research programme that investigated the effect of mellowing on the modification process of four British soils (Mercia Mudstone, Oxford Clay, Lower Lias and London Clay) treated with quicklime. This second paper presents the findings of the second phase of this research, which investigated the effect of mellowing on the stabilization process of the same four soils discussed in Part 1. Both papers suggest a need to improve the design methods for lime treatment of clays in the international procedures. 3

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