Freeze-Thaw Performance Characterization and Leachability of Potassium-Based Geopolymer Concrete

Abstract

It is well known that concrete is one of the most widely used construction materials in the world, and cement as its key constituent is partly responsible for global Carbon Dioxide (CO2) emission. Due to these reasons, high strength concrete with lower CO2 emission, and concrete with lower reliance on natural resources is increasingly popular. Geopolymer Concrete (GPC), due to its capability to minimize the consumption of natural resources, has attracted the attention of researchers. In cold regions, frost action is one of the primary GPC deterioration mechanisms requiring huge expenditures for repair and maintenance. In this regard, two types of GPC (fly-ash based GPC and bottom-ash based GPC) were exposed to the harsh freeze-thaw conditions using a standard test method. The dynamic elastic modulus of both types of GPC was determined using a Non-Destructive Test (NDT) method called Resonant Frequency Test (RFT). The results of RFT after exposing to 300 freeze-thaw cycles showed that bottom-ash based GPC has better freeze-thaw resistance than fly-ash based GPC. Moreover, in this study, the leachability of bottom-ash based GPC was also investigated to trace the heavy metals (including Si, Al, Na, Cr, Cu, Hg) using Toxicity Characteristic Leaching Procedure (TCLP) test. The results of the TCLP test showed that all of the heavy metals could be effectively immobilized into the geopolymer paste.

Durability of Alkali-Activated Materials Made with a High-Calcium, Basic Slag

“…This agrees with former authors: Bakharev et al [20], following experiments with sodium sulfate solutions, found strength increase in AAS concrete. Similarly, Luga [29] evidenced that slag geopolymers increased compressive strength by 14-24% respectively following wet-dry cycles, and other authors found a compressive strength increase after freeze-thaw cycling [32][33]35]. The strength increase can be attributed to the presence of smaller pores [34] but is is likely the result of continuing hydration [20].…”

“…Fu et al [31] evidenced weight loss under 1% a frost resistance coefficient of ∼90% after 300 cycles. It is also relatively common to find instances of strength increase following durability cycling in the literature [32][33][34][35].…”

Fresh, Mechanical, and Durability Behavior of Fly Ash-Based Self Compacted Geopolymer Concrete: Effect of Slag Content and Various Curing Conditions

“…Internal microcracks are formed as a result of the expansion pressure. An increase in freeze–thaw cycles contributes to the extension of micro-cracks over time [ 29 ]. There are very limited investigations on the performance of geopolymer concrete and SCGC under freeze–thaw tests, and studies in this field need to be extended.…”

Coal Fly Ash–Clay Based Geopolymer-Incorporating Electric Arc Furnace Dust (EAFD): Leaching Behavior and Geochemical Modeling

“…In this way, there are some studies that show the results of incorporating EAFD in processes of geopolymerization of coal fly ash [16,17,37]. On the other hand, it should be noted that there is a significant number of published studies that evaluate the environmental implications of geopolymeric systems based on industrial waste through leaching behavior, but exclusively using a leaching test, mostly the TCLP [38][39][40][41][42]. Although geochemical modeling of inorganic waste and stabilized waste has been extensively used, only limited research has determined the chemical species and leaching of oxyanions [32,35,43,44], and only some authors studied the geochemical modeling of FA based geopolymer [23,38,45].…”