Greening stabilized rammed earth: devising more sustainable dosages based on strength controlling equations

• Equations that govern the strength of soil-fly ash-lime blends are proposed.
• All equations involve a unique porosity/volumetric lime content ratio.
• These equations can be use to devise dosages that minimize resources consumption.
• An example shows how the equations can be use to devise and assess dosage options.

Rammed earth is an ancient construction technique that has been gaining renewed attention due to its potential to produce more environmentally sustainable constructions. Yet, studies that quantify the gains in strength by varying key parameters (binder content, dry unit weight) are still limited, hindering an efficient use of resources (materials and energy) when adopting this technique. Seeking to fulfil this gap, this paper presents equations that quantify the effect of parameters (dry unit weight, lime content, and fly ash content) on the compressive strength of Botucatu residual soil – fly ash – lime blends. Such equations allow different values to be assigned to each of these parameters (resulting in distinct strength results). This enables dosages that minimize resource consumption and maximize resource reuse/recycling to be devised. To illustrate that, eight dosages options are proposed for a target strength using the proposed equations and assessed against a number of criteria. The results indicate that dosages that are able to simultaneously minimize resources consumption and maximize resource recycling can be produced.