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.

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In this study, environmentally friendly ground granulated blast furnace slag (GGBFS) based alkali activated materials and basic oxygen furnace slags (BOFs) were used as bonding materials and aggregates, respectively, to produce novel, environmentally friendly GGBFS based porous concrete. Porous concrete with a particle size of 4.75–9.5 mm and 9.5–19.00 mm was used as an aggregate. The “liquid-to-solid ratios” (L/S) variable was set at set at 0.5 and 0.6, and the “percentage of pore filling paste ratio” variable was controlled at 40%, 50%, and 60%. The curing period was set at 28 d, and the relationship between connected porosity and permeability, as well as that between unit weight and the pore filling paste ratio percentage were explored using analysis of variance. The results showed that the porous concrete had a maximum compressive strength of 8.31 MPa. The following results were obtained. An increase in percentage of pore filling paste ratio increased compressive strength. Permeability was measured at 4.67 cm/s and was positively correlated with porosity. An increase in porosity increased permeability, in which porosity was positively correlated with the percentage of pore filling paste ratio. The maximum splitting strength achieved during the 28 d was 1.46 MPa, showing a trend similar to that of compressive strength.

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This study investigated the effect of substituting cement with incense ash on material properties and hydration of cement-based composite materials. Test specimens with incense ash replacing up to 30% (volume) of cement were produced and cured at 25 °C and 75 °C for up to 120 days. The researchers of this study observed the effect on setting time, heat conduction, compressive strength, and water absorption, and conducted a microanalysis to observe the structural change of hydration products. The results indicated that by substituting cement with incense ash, the hydration reaction was hastened, and the setting time shortened. When 5% of cement was replaced, incense ash had the effect of filling the voids between particles. At a higher curing temperature, the frequency of particle collisions increased, expediting the hydration reaction and improving the strength of the specimens. At a longer curing time, voids in the specimens were gradually filled by colloids, and pozzolanic reaction caused the amount of Ca(OH)2 to diminish and C–S–H gel to increase, which in turn improved the structural cohesion, reduced the water absorption, and increased the strength and thermal conductivity of the specimens.