Experimental Investigation and Mechanism of Fly Ash/Slag-Based Geopolymer-Stabilized Soft Soil

Abstract

In response to the high carbon emissions and energy consumption of traditional cement curing agents, in this paper, we propose a fly ash/slag-based geopolymer as an alternative to cement for stabilizing soft soils. In this study, the effects of the activator modulus, activator, and slag content on the geopolymer-stabilized clay were investigated by unconfined compressive strength (UCS) tests on Hangzhou soft soils, and the water stability and resistance to wet–dry cycles of the geopolymer-stabilized soils were studied. The changes in the microstructure and mineral phases were investigated using X-ray diffraction and scanning electron microscopy, respectively, and the inner evolution of the properties of the stabilized soft soil under different conditions was clarified. The test results revealed that the UCS of the geopolymer-stabilized soft soils increased and then decreased as the content and modulus of the alkali activator increased. The optimum mix proportion of geopolymer-stabilized soil required a modulus of the alkali activator of 0.6, a content of the alkali activator of 6%, and a slag-to-fly ash ratio of 1:1. Its 28-day UCS of the test specimens reached 2 MPa. When the content of the geopolymer was 25%, the water stability coefficient reached 87.53%, and the strength was still 1.6 MPa after eight wet–dry cycles. Based on the microscopic analysis, the cementing substances in the geopolymer-stabilized clay were calcium silicate hydrate (C-S-H) and sodium aluminosilicate hydrate (N-A-S-H), which made the soil’s structure denser through bonding and filling effects.

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

“…In Figure 8-a, Klias peat showed the presence of voids, similar to those reported by Sutarno & Mohamad [26], Latifi et al [99], and Hassan et al [100], interspersed with particles possessing honeycomb structures, an indication that the peat soil is fibrous [101]. Meanwhile, the GGBFS material seen in Figure 8-b shows particles that are smooth and possess semi-polygonal shapes [102], that are angular [97], and that are sharp-edged in nature [73].…”

“…Subsequently, for GGBFS, its main constituents are oxygen (O), calcium (Ca), silicon (Si), and aluminum (Al), with the rest of the elements amounting to 6.37% of the sample mass. The GGBFS material was chosen as the second aluminosilicate source to produce geopolymer compounds due to its ability to improve the mechanical and durability properties of fly ash-based geopolymer mixes, as reported by recent studies [11,82,97]. This is due to the contribution of the oxygen (O) and calcium (Ca) elements within the GGBFS material, and the GGBFS presence is required in the geopolymer mix in order to maintain the Si/Al ratio of the geopolymer so that it remains between the required range of 2-4, as recommended by Khanday et al [98].…”

An Application of Geopolymer stabilized expansive soil to reduce the rainfall-based erosion in slopes

“…Geopolymer has recently gained attention as a viable substitute for Portland cement [12][13]. In addition to its environmental benefits, geopolymer-stabilised soils have demonstrated enhanced qualities that satisfy the demands of engineered clayey soil.…”

Mechanical Properties of Slag-Based Geopolymer Grouting Material for Homogenized Micro-Crack Crushing Technology

“…Sofri et al [26] explored the effects of FAG on road base layer properties using a mechanistic laboratory evaluation and its practicability in pavement base layers. Wu et al [27] proposed a fly-ash-/slag-based geopolymer as an alternative to cement for stabilizing soft soils. Li et al [28] conducted research on the mechanical properties of fly ash-slag-based geopolymer to solve various problems, such as difficulty to store and transport liquid activator of the existing geopolymer grouting materials.…”