Stabilized Earth Road Construction: Compressed Blocks, Rammed Earth, and Poured Earth

Good roads are essential community infrastructure. Dirt roads create nuisance dust and present continual maintenance requirements, due to the formation of ruts and potholes. Covering roads with imported aggregates, and binding them with tar is both expensive and environmentally harmful. The use of native soils, as aggregates, combined with sand, a stabilizer (cement, lime, proprietary stabilizers), can result in roads that meet local needs, are much less expensive, and have a much lower adverse environmental impact.

Since 2012 AVEI has explored the use of CSEB, rammed earth, and poured earth technologies for road-building, from initial laboratory tests, to pilot scale, and finally full-scale projects.

Numerous reports are available regarding these efforts in our library.

Follow up: the viability of these road projects, to determine how well they have held up during normal usage, will be an on-going study over the course of years. The more information we can gather regarding the road performance characteristics, the more able we will be to design additional tests, or to experiment with additional formulations.

Masonry (CSEB) Vault Insulation Study

In 2012, Lara Davis, et al, conducted a study to determine the optimal mix ratio for a non-structural layer of insulation to be applied on the outside of earthen masonry vaults, using expanded polystyrene pellets (Thermocol) in a stabilized earth matrix. The aim of this testing was to determine consistent workability for a well-compacted, properly adhering, and easily applied layer of insulation. A number of samples of differing mix ratios of [sand:cement:soil:thermocol:water] were prepared and subjected to a series of performance tests. A satisfactory mixture was derived and applied to the surface of a CSEB 26 m2 vault, as the innermost element of the insulating, durable, and waterproof vault outer-shell, which is also detailed in this article.

Follow up: additional work could be conducted in the following areas; 1.) find a local renewable sustainable by-product to substitute for the expanded polystyrene pellets; 2.) perform studies to determine the effectiveness of this insulating layer verses a vault with no insulating layer.

Poured Earth Concrete

Research into Poured Earth Concrete (PEC) has been an active area of research at AVEI since 2011. PEC is presently underutilized, and has great potential for poured walls, slabs, and roads. The research conducted at AVEI has centered around deriving PEC mixes that achieve desired flow characteristics, while maintaining dry and wet strength, low water absorption, and low shrinkage. Deriving mixes appropriate to local soils, the necessary testing and finalization of formulations, with additions of plasticizers, and waterproofing agents, have been explored.

Tadelakt & Other Lime Plasters

In 2016, Solène Delahousse, a French lime artisan, came to AVEI and conducted research focused on lime plasters on rammed earth walls. Research was conducted on three different lime samples: an industrial lime, which was heavily processed; a burned shell commercial product, from Kerala, and finally a 'village' lime, which was also produced from shells, but in a local village where strict quality protocols were not employed. Test batches of plaster were prepared from these lime sources, with an admixture of either sand, quarry dust, or marble dust. Application of these plasters also utilized the Marmarino and Taldelakt techniques. The test sample plasters were applied to an external wall surface, exposed to rain and sun, and their performance characteristics are monitored. An area of further study is to properly evaluate the waterproof effectiveness of black soap to the top surface layer.

Durability of CSEB

"Good Hat, Good Boots!" This succinct phrase captures an essential aspect of effective design for earth construction. Through the use of generous roof overhangs, proper drainage, and well designed/engineered foundations earthen buildings can last for thousands of years. Problems can and do however crop up when these guidelines are not well adhered to. Research has been conducted to determine the susceptibility to degradation not only due to direct rainfall, but also through capillary action, absorption, and through additional attack by fungi, mildew, mold, and algae when in contact with moist biomass.

Waste Water Treatment Systems in Auroville

TBD