Alkaline activation via in-situ caustification of one-part binders of composite precursors of waste glass and limestone

Mixtures of powders of waste glass (WG), limestone (LS), Na 2 CO 3 and CaO were used to formulate novel one-part in situ alkali-activated cement (WG-AAC). The in-situ interaction Na 2 CO 3 -CaO-H 2 O promoted the formation of CaCO 3 and NaOH, which promoted the WG and LS dissolution and influenced the micro- and molecular features of the resulting cementitious products. Pastes and mortars developed 1-year strengths of up to 29 MPa and were stable underwater. Characterization by XRD, SEM, EDS, and 29 Si -NMR indicated that a Na 2 CO 3 :CaO ratio close to 1:1 resulted in polymerized C-S-H, CaCO 3 , silica gel, and Ca-modified silica gel, which were intimately intermixed and possibly crosslinked through Q 3 bonds. Such phases interacted synergistically improving the underwater stability of the WG-AAC, indicating that in-situ caustification is a suitable and practical alkaline activation for SiO 2 -rich precursors. • One-part activation of waste glass produced mortars with up to 29 MPa and stable underwater. • Caustification reactions positively influenced the micro and molecular features of the matrix. • Ca-modified silica gel, CaCO 3 , C-S-H and silica gel coexisted synergistically.