Investigation on Soil Strength and Microstructure of Palm Oil Boiler Ash with Sodium Hydroxide and Sodium Silicate as Alkaline Solution

Abstract

Palm oil boiler ash is a type of industrial waste from palm oil production, which abundantly disposed on landfill, and contaminate the soil and environment. Recently, boiler ash as a by-product is introduced as an additive in chemical stabilization, known as geopolymer. An alkaline solution functions to activate the silica-alumina structure bonding to replace the Ordinary Portland Cement in concrete application but few in soil stabilization study. This study investigates the strength of laterite with a geopolymer. Boiler ash was chosen as source material, with sodium hydroxide and sodium silicate mixed at a ratio of 1:2. Unconfined compressive test (UCT) and SEM were conducted for laterite soil with different geopolymer percentages. The test was conducted by adding a different geopolymer percentage at 0%, 5%,10%,15%, and 20% mixed with laterite soil. The soil sample was cured for seven days for an unconfined compression test (UCT). The result shows that the highest compressive strength was obtained at 15% of geopolymer in laterite soil at 340kPa. SEM tests show that the increased compressive strength was attributable to the 15% of the geopolymer, which had a compact and dense structure and less unreacted raw materials. In conclusion, the results indicated that 15% of geopolymer gives optimum value in enhancing laterite properties' strength. The findings support boiler ash usage as by-products in geopolymers' production for potential use in soil strength stabilization.

A Review of Advances in Peat Soil Stabilisation Technology: Exploring the Potential of Palm Oil Fuel Ash Geopolymer as a Soil Stabiliser Material

“…Meanwhile, the use of POFA-based geopolymers has also been studied by Malaysian researchers in recent years, but these studies focused on the stabilisation of silt and clay soils. For example, Zainuddin et al [43] produced POFA geopolymers to stabilise very silty soil, while Abdeldjouad et al [44] focused on the improvement of residual soil and marine clay using POFA geopolymers, and lastly, [45] conducted a study on the use of POFA geopolymers to enhance the shear strength of silts and clays. The studies carried out by Yusof [42] and Zainuddin et al [43] showed promising results, with stabilised soil UCS ranging from 900-4180 kPa.…”

“…For example, Zainuddin et al [43] produced POFA geopolymers to stabilise very silty soil, while Abdeldjouad et al [44] focused on the improvement of residual soil and marine clay using POFA geopolymers, and lastly, [45] conducted a study on the use of POFA geopolymers to enhance the shear strength of silts and clays. The studies carried out by Yusof [42] and Zainuddin et al [43] showed promising results, with stabilised soil UCS ranging from 900-4180 kPa. At the time of writing, there are no known studies conducted on the improvement of tropical peat soils with POFA-based geopolymers.…”

“…Table 5 shows a summary of the recent studies conducted on the stabilisation of weak soils using POFA-based geopolymers. Further discussions on the results of these research findings are given in the following paragraphs: A very recent study was published by Zainuddin et al [43] pertaining to the use of Palm Oil Fuel Ash geopolymer to increase the strength properties of Pasir Gudang laterite soil. The soil, which is classified as very silty sand, was found to have a natural UCS value of 106 kPa.…”

Physicochemical and Microstructural Characterization of Klias Peat, Lumadan POFA, and GGBFS for Geopolymer Based Soil Stabilization

“…More recently, the use of agricultural and industrial waste-derived geopolymer materials as soil stabilizers has been applied in the geotechnical field, with published studies reporting on the enhancement of engineering properties and improved durability of weak soils [6,7]. Various types of geopolymer source materials were used for soil stabilization purposes, such as coffee grounds [8], tea wastes [9], fly ash [10,11], GGBFS [6,12], and POFA [13][14][15]. In the context of this study, the outcomes of selected studies conducted on POFA-based geopolymers used as construction and weak soil stabilizer materials are discussed below.…”

“…On the other hand, the existing studies on the use of POFA-based geopolymer materials are very limited, and the outcome of these studies has been discussed in depth in a recent review paper [18]. In the study conducted by Zainuddin et al [15], POFA geopolymer was used as a soil stabilizer for weak laterite soil. They reported that the strength of laterite soil improved from 106 kPa to 340 kPa after 7 days of curing, with a 15% POFA geopolymer content.…”