Cow-dung is a widely used stabiliser applied in traditional earthen buildings with one objective to improve water resistance. However, most research has focused on explaining its mechanical strength, with only one study suggesting water resistance mechanism via formation of insoluble compounds at high pH, a phenomenon uncommon in natural cow dung and soil mixtures. This article investigates the water-resistance behaviour of cow-dung stabilised compressed earthen blocks (CD-CEBs) through an extensive experimental programme to understand the influence of cow-dung and soil related factors and to characterise the components of cow-dung responsible for its water resistance. It was found that the small-sized microbial aggregates (SSMA) present in cow-dung, which are negatively charged hydrophobic aggregates of low specific surface area, are responsible for enhanced water resistance of CD-CEBs. The insights gained from experiments are compiled to recommend the following strategies for improved performance of CD-CEBs: (i) The use of wet cow-dung is advised over dry cow-dung as it provided over 80 times better water resistance; (ii) Adopting a higher compaction liquid content (by 3%) improved the water resistance by over 40 times; (iii) The water resistance of CD-CEBs was improved over 30 times by using soils rich in low-swelling clay minerals such as kaolinite. A case study applying these findings demonstrates the successful scaleup from the lab to field showcasing potential of cow-dung and soil in low-carbon construction.

Housing is a cross-cutting issue that is crucial to achieving several of the Sustainable Development Goals. Earthen housing is found across the globe, particularly in developing countries, but there is a lack of up-to-date information about its distribution and trends. This knowledge gap is a barrier to developing more effective research and policy for earthen housing. In this study, national demographic datasets were used to investigate the distribution, trends and attitudes towards earthen housing worldwide. Data was collected and analysed for the most populous 26 countries, which make up >75% of the global population. Globally, earthen housing is in decline relative to non-earthen housing, driven by demographic changes and negative perceptions of earthen materials in developing countries. The proportion of households living in earthen dwellings worldwide is estimated to be 8–10%, and the average across developing countries to be 20–25%. There is a negative correlation between countries’ level of development and prevalence of earthen housing. Whilst data is more sparse for highly developed countries, the development of standards and commercial interest suggests more favourable attitudes to earthen housing. A focus is encouraged on high-quality earthen dwellings which can help meet housing needs in both developing and developed countries.

There is an enormous demand for rural housing in India that needs to be catered for within a short span of time. Building with earth (mud) is proposed as an economical and environmental friendly alternative due to the rising costs of conventional building materials. However, the construction of earthen houses has significantly declined in India and thus it is necessary to evaluate if they can make a valuable contribution to contemporary housing shortage. Therefore, an informal survey was conducted in India to understand factors favouring or limiting the construction and daily use of earthen houses. The outcome of the survey suggests that ‘Image’ is the key barrier against a wide acceptance of traditional earthen houses which are linked to poverty. While modern earthen construction is desired, it is expensive for low-income households. The role of earth in addressing the contemporary housing shortage is analysed and suggestions are given for the implementation of modern earthen technologies for low-cost affordable rural housing. Initiatives by middle-high income households, entrepreneurs and government can trigger a widespread interest in earthen construction. Successful demonstration of durable earthen structures at diverse locations and contexts can act as catalysts for change of the image of earth and make it a desirable material for low-cost housing in rural India.

Starch is a natural polymer which is commonly used as a cooking ingredient. The renewability and bio-degradability of starch has made it an interesting material for industrial applications, such as production of bioplastic. This paper introduces the application of corn starch in the production of a novel construction material, named CoRncrete. CoRncrete is formed by mixing corn starch with sand and water. The mixture appears to be self-compacting when wet. The mixture is poured in a mould and then heated in a microwave or an oven. This heating causes a gelatinisation process which results in a hardened material having compressive strength up to 26 MPa. The factors affecting the strength of hardened CoRncrete such as water content, sand aggregate size and heating procedure have been studied. The degradation and sustainability aspects of CoRncrete are elucidated and limitations in the potential application of this material are discussed.