Quality control of earth construction in developing areas

Current quality control of earth construction in developing and disaster areas is very basic, relying on highly operator-dependent, non-standardised tests. The uncertainty in material properties has led to over-conservative design, increasing construction costs where it can least be afforded. The development of a quality control kit is described; to be fit for purpose it had to be cheap and easy to use. The equipment included had to be portable, resilient and independent of mains power. The hydrometer and Atterberg limit test methods from BS 1377 (soil investigation) are slightly modified to be more suitable for field application. The modified methods are deemed acceptable if they provide sufficient accuracy to be useful as a design tool. In an adaptation of cement mortar tests, the compressive strength of bricks or blocks is tested over a 100 mm × 100 mm area. This has been shown to give safe but not over-conservative values of strength using portable equipment. The report concludes that an accurate, quantitative kit can be compiled for under £350 (US$560), excluding labour for its construction, with a mass of 10–25 kg, depending on the types of tests required. This is less than the mass of soil and blocks required for equivalent tests in a commercial laboratory.