Abstract
One-part or “just add water” geopolymer is a cementitious material, which is friendly to environment and users in applications. However, the mechanical behavior of the soft soil stabilized by one-part geopolymer is not well acknowledged. In this study, soft clay was stabilized with ground granulated blast furnace slag (GGBFS) and fly ash (FA)-based geopolymer, which is a mixture of solid aluminosilicate precursor (Al-Si raw materials: GGBFS and FA), solid alkali activator, and water. The objective was to adopt one-part geopolymer as an alternative soil binder to completely replace ordinary Portland cement (OPC) for stabilizing the soft clay and evaluate the effect of the factors (i.e., GBFS/FA ratio in Al-Si precursor, activator/Al-Si precursor ratio, and water/binder ratio) that influenced the early strength. Results showed that the increase of the FA content in the Al-Si precursor increased the unconfined compressive strength (UCS) values significantly through the geopolymerization process. The highest UCS values were achieved with 90% GGBFS to 10% FA in the precursor when the activator/precursor and water/binder ratio is 0.15 and 0.7, respectively. The UCS values of geopolymer-stabilized clay could reach 1.5 MPa at 14 days at ambient temperature, which is much higher than that of OPC-stabilized clay. The microstructure and mineralogy analyses indicated that the prolific hydration products, such as calcium silicate hydrate (C-S-H), calcium aluminum hydrate (C-A-H), and calcium aluminum silicate hydrate (C-A-S-H), contributed greatly to strengthen the soft clay by forming the soil skeleton and infilling among clay particles, while sodium aluminosilicate (N-A-S-H) gel is only served to fill the part of porosities in the soil and cannot effectively enhance the UCS of the one-part geopolymer-stabilized soft clay. This paper results suggested that one-part GGBFS-FA–based geopolymers have the potential to replace OPC in the manufacture of stabilized soft clay.
Highlights
Geopolymer is an alternative binder agent that belongs to a new type of cementitious material, which is polymerized from Al-Si raw materials
When the fly ash (FA) content was less than 10%, the unconfined compressive strength (UCS) values of one-part geopolymerstabilized soil increased with an increase in the FA content; while for the FA content being more than 10%, further increasing FA content would decrease the UCS values of the stabilized soft soil
This paper studied the early strength development of the one-part ground granulated blast furnace slag (GGBFS)-FA–based geopolymer-stabilized soft clay
Summary
Geopolymer is an alternative binder agent that belongs to a new type of cementitious material, which is polymerized from Al-Si raw materials. With the activation of alkali-activator, the Al-Si raw materials produce hydration materials with the characteristics of high early strength. The OPC-stabilized soft clay often has the problem of insufficient early strength. Since the Al-Si raw materials of the geopolymer came from industrial by-products with the lower cost compared to OPC, adopting the geopolymer as the binder agent to stabilize the soil had a great potential to solve the “3H” problems (high pollution, high energy consumption, and high cost) induced by the application of OPC binder. The early strength development of geopolymer paste was faster than that of OPC paste, which might enhance the early strength of stabilized soil and shorten the constriction time
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