Improving Very High Plastic Clays with the Combined Effect of Sand, Lime, and Polypropylene Fibers

Abstract

Improving the mechanical properties of low-strength soils (e.g., high plasticity clays) is one of the main branches of geotechnical engineering. The adoption of stabilization techniques for ensuring that structures will be founded on an adequately strong soil base is a common practice. Stabilization techniques for clay soils may include inert materials (cohesionless soils), chemical substances (cement, lime, or industrial additives), or the use of randomly distributed fibers. While all of these additives are added to low-strength soils by mixing, the question remains whether an optimal combination of stabilization techniques can be achieved for maximizing soil strength. Besides, each one of these additives contributes to an increase in soil strength in a different manner (soil replacement, chemical bonding of soil particles, and soil reinforcement respectively), while, according to the literature, each technique has its limitations. The latter refers to a limited effect on strength improvement and a maximum possible percentage, beyond which an additive has an adverse effect on strength; it also refers to other factors, such as brittleness failure, material availability, overall cost, and environment-related issues. Hence, in the present study, the efficiency of improving the basic geotechnical properties of a very high plasticity clay (liquid limit ωl = 86%) with a coupled effect between dune sand, lime, and polypropylene (PP) fibers has been investigated. The samples prepared by combining the three aforementioned soil improvement techniques were compared in terms of plasticity, compaction characteristics, unconfined compressive strength (UCS), and California Bearing Ratio (CBR) index. The experimental results show that the combination of these additives may lead to a considerable improvement in the strength and ductility of soils, even with a small amount of lime additive. Also, it was observed that 20% of sand, 3.4% of lime and 0.9% of fibers (by wt%) offers the best performance in terms of strength improvement for the clay tested (i.e., 12.75 times improvement compared to the untreated clay).

Evaluation of the Permeability of Clay-Lime Mixtures for Hazardous Waste Insulation Barriers, Case of Southern Algeria (Adrar)

“…All the MDD values range from 17.7 to 17 KN/m 3 . This result is perfectly consistent with previous works [43,83,97,[102][103][104][105][106][107][108]. This decrease can be explained by the fact that lime tends to absorb water to complete its hydration, as well as the pozzolanic reaction [20,80,96,108].…”

“…The pH increases from 7.8 for natural clay to 12.35 after adding 2 % lime and stabilizes from 12.62 to 12.82 for 4 and 6 %. According to this method, a minimum of 3 % of lime is required to obtain a pH value of 12.4, which corresponds to the Lime Fixation Point (LFP); [82,90,[94][95][96][97]. The increase in pH values is ascribed to the decrease in the relative amount of clay mineral content in the treated sample (see Table 1), 2, 4 and 6 %) due to the reaction of lime with clay, allowing the consumption and dissolution of clay minerals and possibly the creation of new minerals with linking characteristics [82,83,87,88,91,[98][99][100].…”

Development of Clay-Composite Plasters Integrating Industrial Waste

“…In clay composites, NaCl was introduced as an 8% saline solution prepared by dissolving the salt in potable water. -Hydraulic lime was chosen based on initial experimental tests and numerous literature findings that highlight its positive impact in reducing drying shrinkage and the likelihood of fissuring, due to the added calcium oxide content [62][63][64][65][66][67][68][69][70][71]. In this instance, preliminary experimental research examined the effects of partially substituting clay with hydraulic lime in compositions consisting of clay, fly ash, and limestone sludge.…”

Clayey Soil Improvement with Polyethylene Terephthalate (PET) Waste

“…Since then, research into improving soils with fibres has advanced, and nowadays both natural and waste fibres are used in the process. Research has been performed on improving soils with fibres from bamboo [14,15], jute [16,17], coir [18,19], palm [20,21], sugar cane [22], waste rubber [23,24], and waste plastics [25][26][27]. In most cases, the results showed an increase in the geotechnical parameters considered in the studies such as an increase in the internal friction angle and cohesion, an increase in the shear strength of the soil, improved compressibility, and improved behaviour of the studied soil to moisture variations.…”