Molecular characteristic of phosphoric acid treated soils

The expansive nature of soils containing high amounts of clay minerals can be altered through chemical stabilization, resulting in a material suitable for construction purposes. The primary objective of this investigation was to study the changes induced in the molecular structure of phosphoric acid stabilized bentonite and lateritic soil using Nuclear Magnetic Resonance (NMR) and Fourier Transform Infrared (FTIR) spectroscopy. Based on the obtained data, it was found that a surface alteration mechanism was the main reason responsible for the improvement of treated soils. Furthermore, the results indicated that the Al present in the octahedral layer of clay minerals were more amenable to chemical attacks and also partly responsible for the formation of new products

Reducing Print Time While Minimizing Loss in Mechanical Properties in Consumer FDM Parts

Fused deposition modeling (FDM), one of various additive manufacturing (AM) technologies, offers a useful and accessible tool for prototyping and manufacturing small volume functional parts. Polylactic acid (PLA) is among the commonly used materials for this process. This study explores the mechanical properties and print time of additively manufactured PLA with consideration to various process parameters. The objective of this study is to optimize the process parameters for the fastest print time possible while minimizing the loss in ultimate strength. Design of experiments (DOE) was employed using a split-plot design with five factors. Analysis of variance (ANOVA) was employed to verify the model significance or otherwise. Once the model was developed, confirmation points were run to validate the model. The model was confirmed since the observations at the optimum were within the prediction interval with a confidence value of 95%. Then, the model was used to assess the ultimate strength and print time of FDM parts with consideration to nozzle diameter, the number of outer shells, extrusion temperature, infill percentage, and infill pattern. Recommendations are discussed in detail in this study to reduce print time without sacrificing significant part strength

Lime stabilized Malaysian lateritic clay contaminated by heavy metals

This paper highlights the essential tests for assessing the suitability of lime as a binder for contaminated Malaysian remediation by reducing the leachability of contaminants. The contaminated soils can achieve a higher strength after lime solidification/stabilization process. However, contaminants in soils may interfere with the process of stabilizer hydration, and as a result lead to a more complicated strength development than conventional st abilized soils. For soils contaminated by different types of heavy metals, the lime stabilized products may have different strength properties since heavy metal in the soils would influence the extent of chemical fixation among lime-soil and contaminations mixtures. This paper presents an experimental study on the unconfined compressive strength of lime stabilized lateritic clay soils contaminated by copper and zinc. The control sample (lime stabilized soil without heavy metals) is also prepared for comparison purpose. The test results show that the presence of heavy metals in soils interferes with lime hydration process, which is directly reflected by the variation in the strength development of samples. It is found that the metal concentration, the stabilizer content, and the type of heavy metal are the main factors which affect the stabilizer hydration and strength

Experimental investigations on behaviour of strip footing placed on chemically stabilised backfills and flexible retaining walls

The gradual increase in population, as well as rapid development in the construction industry in recent years, has made it more urgent than ever to gain the sufficient knowledge and information needed to improve existing soil for geotechnical engineering purposes. This study focuses on the experimental investigations of small-scale physical model tests to evaluate the performance of selected locally manufactured non-traditional additives (SH-85 and TX-85) in field applications, particularly as the backfill of retaining walls. Unconfined compressive strength (UCS) tests, a set of physical model tests and a field emission scanning electron microscope (FESEM) were conducted. The physical models were different in terms of parameters such as the type of additive and the strip footing distance from the wall. The UCS test results showed that the addition of 9 % (as the optimum amount) of both additives increased more than 80 % of the compressive strength after 7-day curing periods. The results from the physical model tests showed that the ultimate capacity of the footing placed on the stabilised backfill soil increased greatly while the settlement reduced noticeably compared to the untreated backfill. Additionally, by increasing the distance of the strip footing from the wall, it increased the ultimate capacity of the footing. Besides that, the addition of additives in either powder or liquid form to the backfill led to a reduction in wall horizontal displacement and the strain distribution on the wall. Furthermore, less porous and denser soil fabric was observed on the surface of clay particles from FESEM images

Tropical residual soil stabilization: A powder form material for increasing soil strength

Stabilization of problematic soils for earthwork applications can be performed using a variety of chemical additives, with lime, cement, or fly ash all being traditionally employed for this purpose. More recently, various new calcium-based additives have been actively marketed by a number of companies for soil stabilization applications. The stabilizing mechanisms of these commercially available products are not fully understood, and their proprietary chemical composition makes it difficult to predict their effectiveness. The current study examines the effectiveness of SH-85, a new calcium-based powder additive which is prepared from biomass silica, for stabilization of a tropical residual laterite soil. At the macro-level, changes in soil strength due to additive stabilization were assessed using a series of unconfined compression strength (UCS) tests. The underlying mechanisms that contributed to the stabilization process were explored using spectroscopic and microscopic techniques, including X-ray diffractometry (XRD), energy-dispersive X-ray spectrometry (EDAX), field emission scanning electron microscopy (FESEM), and Fourier transform infrared spectroscopy (FTIR). The UCS test results indicated that the addition of SH-85 powder had a significant stabilizing effect on the laterite soil, with the UCS values increasing fivefold after a 7-day curing period. At the micro-level, addition of SH-85 had a weathering effect on the clay minerals, changing the peak intensities of the observed minerals in the XRD spectrums as the stabilized soil was cured. A significant change in the soil fabric was also observed with curing time in the FESEM tests, with additive stabilization yielding a less porous and denser soil fabric, and changes in the surface appearance of treated clay particles. This research study confirms the potential of SH-85 as an alternative to traditional stabilizers for construction involving tropical residual soils