Physico-chemical and microstructure of artifical soils atabilised with lime-zeolite

Abstract

The chemical stabilisation by admixing soil with lime is widely used in soft soil stabilization but its effectiveness in organic soil is low. Studies have shown that besides the organic content, the type of organic matter also influences the effectiveness of lime stabilisation. Artificial soils were utilized in this study to minimize potential influential factors that may be affected by the geochemistry variability of natural organic soils. Two types of organic matter, namely organic acid (contains humic acid and fulvic acid) and coco peat were utilized to simulate humified and non-humified organic matters that are normally found in natural organic soils. Commercially processed kaolin with different fineness and nSi/nAl were chosen as the base soil. The base soil and organic matter were manually mixed in different ratios based on their dry unit weight. Lime was partially replaced with zeolite with the aim to produce additive with self cementing matrix. The effectiveness of blended lime zeolite was investigated in this study. The total amounts of additives ranged from 7.5% to 15% were utilized based on the results of the Initial Consumption of Lime (ICL). Half of the remoulded test specimens were cured with a constant temperature of 50°C in an oven while the other part of the samples was cured at room temperature. The curing periods were set as 7, 28 and 56 days before being tested for unconfined compressive strength. Strength is utilized to determine the effectiveness of additives in stabilising artificial soils. The morphology of the stabilised and unstabilised materials was examined using a Field Emission Scanning Electron Microscope (FESEM), while the mineralogy of the materials was determined using X-Ray Diffraction (XRD) in order to unveil the hardening mechanisms of stabilised soils. General Linear Model (GLM) was utilized to determine the significant main factors, and interactions factors on the strength of artificial soil. The significant factors were used as the input parameters for multiple regression analysis to develop the strength prediction model. The models were utilised to predict the strength of stabilised materials within the inference space defined by the experiment. Overall, the mixture of coco peat and organic acid showed a deleterious effect on the strength of lime-zeolite stabilised artificial soils by lowering the soil’s pH and increasing its porosity. However, the results of the organic acid samples with different pH and cured in different curing temperature were inconsistent. The availability of needle-like structures or Calcium Silicate Hydrate (C-S-H) phase was used as an indicator of successful in the cementation process without being inhibited by organic matter. The 20% replacement of lime with zeolite was found to achieve the highest strength when used to stabilise artificial soils with 30% of organic acid under a laboratory environment. A 20% replacement of lime with zeolite was found to experience only a slight decrease in pH and was able to enrich the elemental properties of lime with silica and alumina, which are important for producing a cementing matrix in an alkaline environment.