Ultrasonic, Molecular and Mechanical Testing Diagnostics in Natural Fibre Reinforced, Polymer-Stabilized Earth Blocks

Abstract

The aim of this research study was to evaluate the influence of utilising natural polymers as a form of soil stabilization, in order to assess their potential for use in building applications. Mixtures were stabilized with a natural polymer (alginate) and reinforced with wool fibres in order to improve the overall compressive and flexural strength of a series of composite materials. Ultrasonic pulse velocity (UPV) and mechanical strength testing techniques were then used to measure the porous properties of the manufactured natural polymer-soil composites, which were formed into earth blocks. Mechanical tests were carried out for three different clays which showed that the polymer increased the mechanical resistance of the samples to varying degrees, depending on the plasticity index of each soil. Variation in soil grain size distributions and Atterberg limits were assessed and chemical compositions were studied and compared. X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), and energy dispersive X-ray fluorescence (EDXRF) techniques were all used in conjunction with qualitative identification of the aggregates. Ultrasonic wave propagation was found to be a useful technique for assisting in the determination of soil shrinkage characteristics and fibre-soil adherence capacity and UPV results correlated well with the measured mechanical properties.

Seaweed biopolymers as additives for unfired clay bricks

“…However, specimen PR22W offered the greatest increase in strength (an increase of 123% compared to the control mix) of all the specimens studied. Overall the range of values for soil U and V are comparable to the flexural results achieved by Galán-Marín et al (2013), however this study additionally demonstrated the level of flexural strength increases compared to control samples. Interestingly, in the case of the dosage study, as shown in Figure 6, increasing the dosage of alginate added to the soil mix did not significantly improve the flexural strength of the blocks.…”

“…Indeed the final compressive strength values achieved by Galán-Marín et al (2013), even for the control specimens, are greater than those observed in this study suggesting that differences in the production process, particularly in the compaction technique should be taken into account. The unconfined compressive strength results are also lower than the typical results reported for cement stabilised earth blocks depending on the cement content and product techniques used.…”

“…All of the soils used within this study fall within these ranges. The importance of PI is further highlighted in the conclusions of Galán-Marín et al (2013) where it is proposed that success of the best performing soil is attributed to its high illite content (50%) and PI value (15.7%). In this study, the overall strength also appears to increase with increasing PI and illite content but this factor has been shown to have a negative impact on the percentage increase in strength when the alginate is added.…”

“…As previously mentioned, the most detailed investigations to date are those conducted by Galán-Marín et al (2010) and subsequent studies (Galan-Marin et al, 2012;Galán-Marín et al, 2013;Rivera-Gómez et al, 2014) which discuss the use of alginate, in combination within lignin and natural or synthetic fibres, as additives for unfired clay bricks. Maximum compressive strengths of over 4 N/mm 2 are reported and it is claimed that this material could offer a suitable replacement for convential internal walling systems.…”

“…Furthermore, more recent studies showed variable results when the same alginate was used with alternative soils and different types fibres (Galán-Marín et al, 2013). The type of alginate products used in the studies included both a liquid 'seaweed extract' (Galán-Marín et al, 2010) and a dried alginate powder (Rivera-Gómez et al, 2014) , with the authors concluding that the type of product and the specific alginate-clay interactions required further investigation.…”