Technology transfer of roads technology (NANO modified treatment) to engineered rammed earth house construction

Abstract

Rammed Earth (RE) is an ancient house construction technique which stood the test of time in various parts of the world. As the name indicates, it is literally built by compacting natural earth, soil and gravel between wooden plank shutter formwork forming the RE wall. The earth was traditionally compacted with hand tampers in succeeding layers of approximately 100 mm to 150 mm to refusal density in widths of 300 mm to 500 mm and even thicker walls. The parallel with road layer construction is obvious in the layer lifts of compaction and the compactive effort done at optimum moisture content (OMC). The only difference is this construction is done in successive layers compacted vertically between the boxed in shutter works. The vertical progression of such compacted layers forms the Rammed Earth (RE) wall when the formwork shutters are removed. This layered compacted earth wall forms a sturdy aesthetically pleasing ‘earthy’ wall structure. The wall is basically compacted to “refusal density”, thus being very solid and durable. The RE wall is a solid thick walled structure capable of significant load bearing and suitable for house wall construction. It has very good temperature and humidity control in the house due to the generally thicker walls than normally found in brick wall houses. In South Africa there is not a national guideline or SANS code for such house type construction. It is presented for acceptance as an engineered or engineered design per SANS definition. Australia upgraded their RE specifications and guidelines to include cement stabilisation of the rammed earth, thus resulting in an Engineered Rammed Earth (ERE) solution with obvious improvement in strength and durability. House building technology with a green footprint are promoted on Boschhoek Mountain Estate inclusive or mini wetland systems for sewerage, and mostly solar electricity, etc. Previously (2015), such an ERE house was designed and constructed to pleasing aesthetical standards and strength at half the cost of conventional brick-built houses. The latest roads stabilisation technology with Nano-silane in Nano Modified Emulsion (NME) and Nano Polymer Nano Silane (NPNS) offered an opportunity to replace the cement stabilisation. Various advantages with the Nano Silane were realised, inclusive of the desired water resistance, strength and encapsulation of clay particles or any deleterious minerals that would normally lead to the cracking of a road or such a cement-stabilised ERE wall panel. The technology transfer from roads to the house construction field is described and the end result or end use is clearly demonstrated meeting the end use specifications advocated in the new TRH 24 (2023) for gravel road upgrade to surfaced standards.