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Inclusion of fibres in soil blocks has been shown to enhance strength development. This study investigates the effect of aspect ratio of coconut, bagasse and oil palm fibres on the mechanical properties of soil blocks. Experiments were conducted on soil blocks with fibre aspect ratios (25-125) to determine the compressive and tensile strength of the blocks. Blocks with coconut and oil palm fibres showed increasing strength with increase aspect ratio, while bagasse fibres showed an initial increase followed by a decline at higher aspect ratio. The study concludes that generally longer aspect ratios produce better mechanical properties of soil blocks.

Several studies have focused on improving the properties of soil blocks/bricks due to perceived and real strength and durability limitations. A review of 56 published studies is presented on the effect of stabilization on the performance characteristics of soil blocks. The review found that few studies have been conducted on durability properties of enhanced soil blocks as compared with physico-mechanical properties. Fibre-enhanced soil blocks tended to have peak performance with an optimal content that achieved maximum performance. The maximum performance improvement was generally less than a doubling of the strength of the soil without the fibres. Binders showed a continual improvement with greater concentrations, so much greater improvements can be obtained if the economic and social costs can be justified. Both fibres and binders have variable performance on water absorption with both reductions and increases possible. Generally, both fibre and binder inclusion in soil blocks enhance the performance characteristics of the blocks. Binders are typically more effective on a mass-fraction basis.However the supply of fibres is usually at a lower cost and a reduced environmental impact, and therefore may have a better performance on a per-cost or per-impact basis.

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Studies on sustainable construction materials are on the rise with their environmental, social, and economic benefits. This study identifies the key indicators for measuring sustainable construction materials. The design used for the study was that of a survey which relied on a questionnaire with five-point Likert scale to generate data for the analysis. For this purpose, 25 indicators from the three dimensions (environmental, social, and economic) identified from the literature were presented to the respondents in a structured questionnaire, and responses were collected and analysed using SPSS. The study identified three key environmental indicators for measuring sustainable construction materials, and these indicators are human toxicity, climate change, and solid waste. Furthermore, adaptability, thermal comfort, local resources, and housing for all were identified as the four key social indicators for sustainable construction materials. In addition, maintenance cost, operational cost, initial cost, long-term savings, and life span were found to be the five key economic indicators for measuring sustainable construction materials. The study therefore suggests that these twelve indicators should be considered in future studies that seek to measure sustainable construction materials.

Soil blocks are widely used for construction, especially in less economically developed countries. Addition of agricultural waste fibres has been shown to improve the properties of these blocks, however unlike most composites the fibres are not bound to the soil matrix. Therefore the reinforcement mechanisms are different and not well characterised. This paper investigates these mechanisms through a series of experimental studies to inform the development of better guidance for practitioners, and hence improve housing for low-income communities. The microstructural characteristics were investigated using SEM, CT scan, optical microscope analysis and pull out testing. It was established that fibres in the soil matrix are randomly distributed with gaps between the fibres and soil matrix due to fibre shrinkage during drying of the blocks. It was also found that natural fibres in soil matrix can either be pulled-out or rupture under load depending on the depth of fibres embedment in the soil matrix.

In order to check the suitability of soil to be used as construction material for earth construction, its geotechnical properties are required to be assessed. The purpose of this study is to review previously published studies soil samples and compare them with soil suitability criteria and for selecting suitable soil for earth construction. The geotechnical properties of soil samples used in previous studies were compiled and compared with various requirements to ascertain their suitability for construction purposes. Eighty-nine ( 89) studies in all were consulted and useful data were found in fifty-two (52) of them. Five geotechnical properties of soil were compiled and analysed. These properties are particle size distribution, Atterberg limits, specific gravity, maximum dry density and optimum moisture content. Based on the values of soil properties found in literature, recommendations were made for the suitability of different soil samples for three main techniques (adobe, rammed earth and compressed earth blocks) application in earth construction, while other soil samples were found to be outside the recommendations. It was found that some of the earth construction techniques which were adopted in the previous studies are different from the recommended techniques. It was also observed that some of the soil samples found to be suitable for a particular property test were unsuitable for the other property tests. The study concludes that determining the suitability of the soil for earth construction is important and any soil that is found unsuitable should be enhanced with stabilisers before use.