Physical performances of alkali‐activated portland cement‐glass‐limestone blends

Abstract

The potential of calcium aluminosilicate (CAS) glasses as supplementary cementitious materials is studied in terms of the development of compressive strength for mortars containing a mixture of portland cement, CAS glass, and limestone. In addition, the impact of internal and external alkali activation of the cementitious systems on the mortar performances is investigated. Internal alkali activation is obtained by adding alkali oxides to the CAS glass system, whereas external alkali activation is realized by hydration of the blended cements containing alkali‐free CAS glasses using alkaline solutions. For the internally alkali‐activated systems and the alkali‐free mortars, higher strengths are achieved in comparison to the reference mortar prepared from plain ordinary portland cement. In contrast, the externally alkali‐activated mortars exhibit lower compressive strengths, implying the importance of both the immediate availability of alkali ions in the cementitious system and the increased dissolution rate of the glass particles caused by the network depolymerization. The glasses are also studied by thermal analysis and the results are used to calculate the theoretical CO2 emissions. The lowest embodied CO2 emission is estimated for the blends containing alkali‐activated CAS glasses.

Supplementary cementitious materials: New sources, characterization, and performance insights

“…Thomsen et al [96] showed the contrasting impact of alkali versus calcium network modifiers on aluminosilicate glass structure where alkali cations preferentially charge balance AlO4 3tetrahedra, while calcium ions are more associated to depolymerized SiO4 4-tetrahedra. The resulting local structural heterogeneities in the aluminosilicate glass structure were shown to positively affect reactivity [97]. Similarly, Kinnunen et al [98] found unmixing or phase separation of aluminosilicate glasses by rapid cooling to increase glass reactivity in alkaline solutions.…”

Portland Versus Alkaline Cement: Continuity or Clean Break: “A Key Decision for Global Sustainability”

“…The most prominent consequence to be drawn from the preceding sub-section may be that glass formulation may be understood and programmed as a flexible exercise that addresses two challenges: 1) optimizing glass composition for subsequent use as a precursor (flyglass); and 2) minimizing fluxing temperatures. Several studies have been conducted on reactive glass manufacture for possible use as SCMs or AAB precursors ( Rajaokarivony-Andriambololona et al, 1990 ; Garcia-Lodeiro et al, 2014 , 2016a ; Newlands et al, 2017 ; Schöler et al, 2017 ; Thomsen et al, 2017 ; Golek et al, 2019 ; Kucharczyk et al, 2019 ; Nie et al, 2020 ), with (variable) compositions located on the Na 2 O-SiO 2 -Al 2 O 3 and CaO-SiO 2 -Al 2 O 3 ternary diagrams. All aimed to develop a universal procedure for producing a uniform and optimal glass, simulating the formation of glass with compositions similar to that of fly ash and/or slag.…”

The Charge-Balancing Role of Calcium and Alkali Ions in Per-Alkaline Aluminosilicate Glasses

“…In the optimization of this replacement process, it is important to characterize the dissolution behavior as well as the pozzolanic reactivity of such glass materials in a cementitious environment. − Studies of blended Portland cements (PC) containing waste glasses have shown that chemically durable mortars with compressive strengths comparable to those of conventional PC blends can be obtained by replacing up to 30 wt % of the Portland clinkers with calcium aluminosilicate (CAS) glasses, leading to a significant reduction in CO 2 emissions of the binder material . In particular, the combination of CAS glasses with specific CaO–Al 2 O 3 –SiO 2 compositions and limestone as SCMs may result in a synergetic effect with respect to physical performances and reductions in CO 2 emissions for PC blends with a replacement level of at least 30 wt %. − For such glasses, dissolution studies have shown a congruent dissolution behavior for the Al and Si species in the glasses . Hence, the dissolution rate is strongly influenced by the overall network connectivity that is governed by the network modifiers.…”