Bonding Behavior of Repair Material Using Fly-Ash/Ground Granulated Blast Furnace Slag-Based Geopolymer

Abstract

Fly ash/ground-granulated blast-furnace slag geopolymer (FGG) contains reaction products with a high volume of Ca, hydrated CaSiO3, and hydrated AlCaSiO3. These compounds enable the filling of large air voids in a structure, thus increasing compactness. Therefore, FGG is a more effective repair material to stabilize structures and can function as a sealing and insulating layer. This study used FGG as the repair material for concrete with ground-granulated blast-furnace slag (GGBFS) as the main cement material. The bond strength of the repair was discussed from different aspects, including for fly-ash substitution rates of 0%, 10%, 20%, and 30% and for liquid–solid ratios of 0.4 and 0.5. The slant shear test, and the split tensile test were employed in this analysis. Moreover, acoustic emission (AE) and scanning electron microscopy were used to confirm the damage modes and microstructural characteristics of these repairs. The results revealed that when the liquid–solid ratio increased from 0.4 to 0.5, the slant shear strength of the repaired material decreased from 36.9 MPa to 33.8 MPa, and the split tensile strength decreased from 1.97 MPa to 1.87 MPa. The slant shear test and split tensile test demonstrated that the repair material exhibited the highest effectiveness when the fly-ash substitution was 10%, and revealed that the repair angle directly affected the damage modes. The AE technique revealed that the damage behavior pattern of the FGG repair material was similar to that of Portland concrete. The microstructural analysis revealed that the FGG–concrete interphase contained mostly hydration products, and based on energy-dispersive X-ray spectroscopy (EDX), the compactness in the interphase and bond strength increased after the polymerization between the geopolymer and concrete. This indicated that the geopolymer damage mode was highly related to the level of polymerization.

Experimental and theoretical study of bond behaviour between FRP bar and high-volume fly ash-self-compacting concrete

“…It could introduce different failure modes in the steel and FRP reinforced HVFA SCC specimens, which will be discussed in the next section. Fly ash and limestone powder, as the substi tutes for cement cementitious material, were added into HVFA-SCC, which can improve the compactness property of HVFA-SCC [25,26]. As a result, using HVFA-SCC to replace NC resulted in higher bond strength in this test due to the denser internal structure and stronger chemical adhesion.…”

Characterisation at the Bonding Zone between Fly Ash Based Geopolymer Repair Materials (GRM) and Ordinary Portland Cement Concrete (OPCC)

“…A geopolymer precursor with a composition-featuring high silica (SiO 2 ) and alumina (Al 2 O 3 ) content is highly recommended for development into repair materials [ 9 , 10 ]. Class F FA (ASTM C618), sourced from Manjung, Perak, Malaysia, was used as the main precursor, and this was combined with an alkaline activator solution to produce the geopolymer.…”

Properties of a New Insulation Material Glass Bubble in Geopolymer Concrete

“…Fly-ash based geopolymer concretes have been synthesised from different power stations, resulting in substantially different particle size, morphology, and composition due to the different coal powders and combustion conditions in those plants [ 2 , 30 , 33 , 34 , 35 , 36 , 37 , 38 ]. Fly-ash is excellent for improving early strength and durability, rendering it suitable as the primary source materials in the synthesis of geopolymer concrete [ 2 , 33 , 36 , 37 , 38 , 39 , 40 ].…”