Devising dosages for soil–fly ash–lime blends based on tensile strength controlling equations

• Equations that govern the tensile strength of soil–fly ash–lime blends are proposed.
• All equations involve a unique ratio between porosity and volumetric lime content.
• These equations can be used to devise dosages that allow a more rational use of resources.
• Dosages devised using these equations and their environmental implications are discussed.

Compaction of layers of soil–fly ash–lime blends is often used to improve soil conditions for infrastructure projects. As system failures usually start up under tensile stresses at the base of such layers, splitting tensile strength can be used as a direct measure of the mechanical strength. In spite of that, there is not yet an understanding of the effect of distinct variables on the splitting tensile strength. Such understanding is the starting point to develop more rational dosages that allow for a more efficient use of resources (i.e. energy and raw materials). A series of splitting tensile tests were carried out. An equation linking the effect of porosity and lime content to the tensile strength was found for each curing temperature studied (20 °C, 27.5 °C, 35 °C and 50 °C). For all equations, it was found that a unique ratio between porosity and volumetric lime content controls the tensile strength. These equations could be further generalized into a single equation (linking the effect of curing temperature, porosity, and volumetric lime content to the tensile strength) that is valid for the studied blends and curing temperatures between 20 °C and 35 °C. An example showing how the proposed equations can be used to devise more rational dosages is also presented and highlights the practical application of this study.