Characteristics of boroaluminosilicate geopolymers

Flexural strength of plain and fibre-reinforced boroaluminosilicate geopolymer

“…2e shows a different fracture surface than the former three ones and is related to a medium strength specimen. Although flexural strength of this specimen is not much higher than the previous three ones, very few needle-like crystals are observed that are suggested to be the main reason of strength gain in boroaluminosilicate geopolymers [9]. This is more evident in Fig.…”

“…In both of them, a brittle fracture is occurred and large crystals are appeared after fracture. Formation of these crystals is observed in the authors' previous work [9]. Although large crystals in some cases may indicate the possibility of high strength paste, here, sudden crack growth occurs, causing low strength.…”

“…In the present study, same alkali activator has been used for activation of fly ash and hence, it is anticipated that boroaluminosilicate geopolymers form. Formation of BAO bonds has been shown in the authors' previous work [9]. In that work, possibility of achieving boroaluminosilicate geopolymers with higher strength than aluminosilicate one from a specific fly ash source was achieved.…”

“…1, borax to NaOH solution weight ratios of 0.593 and 0.912 have the similar shape of curve, but this is not the case for the ratio of 0.700. As indicated in the previous work [9], the behaviour of boroaluminosilicate geopolymers requires further studies in terms of their chemical characteristics. There are two challenging effect to determine strength of these types of geopolymers: formation of aluminosilicate or boroaluminosilicate compounds.…”

Utilization of Mineral Wools as Alkali-Activated Material Precursor

“…Theoretically, Si-O-Si are stronger bonds than Si-O-Al or Al-O-Al bonds [32], and the very high Si/Al ratio of GW2 could explain its high compressive strength. However, boron, which was present in GW, has also been noticed to increase the strength of the AAMs [33,34]. One possibility is that silicon and aluminum do not dissolve at the same proportions, as they are present in the mineral wools and, thus, the calculated molar ratios would not represent the real molar ratios of the binder system.…”