Advances in the use of biological stabilisers and hyper-compaction for sustainable earthen construction materials.

In the majority of cases, earthen construction materials for real buildings require amendment to deliver suitable material properties, which could be some additional strength or resilience to erosion. In modern earthen construction, in India, Australia and other parts of the world, cement and lime have been successfully used as stabilisers, providing both strength and durability benefits. However, the use of cement is detrimental to the green credentials of earthen construction materials, due to the large carbon footprint of that material’s manufacture and, for some time, researchers have been motivated to find more appropriate stabilisers and manufacturing methods. In this paper, we present recent findings from two projects that are linked by this motivation, and involve the study of bio-based stabilisers and alternative manufacturing methods for insitu and unit-based materials. Results are presented from laboratory testing of strength and durability of a range of materials, bio-stabilisers and manufacturing processes, indicating that there could be viable alternatives to cement and lime, certainly for many current uses of earthen construction materials

Evaluating the effect of fines on hydraulic properties of rammed earth using a bench scale centrifuge

Unstabilized Rammed Earth (RE) has been historically used to form earth walls or blocks. Recently RE has resurfaced as a sustainable building material with little attention given to it in building codes and manuals. The percentage of the fine-grained fraction in RE is one of the most important factors affecting its behavior. Such percentage has been selected in practice based on experience and rules of thumb, not on a scientific rationale. This research examines the influence of the amount and type of fine particles on the hydraulic conductivity and water retention characteristics of compacted soils using a bench scale centrifuge. A Durner curve (1994) was applied to describe the water retention curve as it allows portraying a bimodal pore structure. In an attempt to understand the basis on which fines contribute to the strength of RE, two different types of fine grained soils were used in the mixtures, plastic fines (PF) and non-plastic fines (NPF). Each type was divided further into different mixtures, each with different percentages of fines. The influence of the fines' percentage was tested using different methods and by using saturated and unsaturated samples of the soil mixtures. Larger suction developed in samples with PF in comparison to those with NPF. Suction increased as the percentage of fines in the mixture increased. Such effect is more pronounced in samples with PF