Title: Environmentally Friendly Concretes Manufactured with CSA Cement
Author(s): Luigi Coppola, Denny Coffetti, and Elena Crotti
Publication: Symposium Paper
Appears on pages(s): 51.1-51.10
Keywords: Calcium sulphoaluminate cement, Portland cement, supplementary cementitious materials, sustainability, ternary binders, concrete
A ternary binder based on ordinary Portland cement (OPC), a commercial CSA clinker and a technical grade anhydrite (CS̅) was used to manufacture the reference concretes (CSA:OPC:CS̅ = 40:40:20). Ground granulated blast furnace slag (S), low calcium siliceous type V fly ash (FA) and an hydrated lime (CH) CL90-S were employed to replace totally OPC in environmentally friendly mixtures (CSA:SCM:CH:CS̅= 40:35:5:20). Tartaric acid-based set-retarding admixture was added at 0.4% vs binder mass and the mixing water was fixed equal to about 200 kg/m3. Experimental data show that the water/binder ratio does not strongly influence the slump of concretes and the workability loss over time. In general, it is possible to conclude that, for practical uses, OPC- or S-based concretes require greater set-retarding admixture dosage than that needed for FA compounds. Furthermore, results indicated that water/binder is, similarly to OPC-based concretes, a key factor in the development of mechanical performances. Moreover, by replacing OPC with hydrated lime and SCMs, negligible changes in 24-hours strength are noted while 30% reduction in compressive strength at 7 and 28 days from casting is achieved, independently of w/b ratio adopted. Also, the curing conditions strongly influence the performances of mixtures. In fact, reference concrete cured in dry environment (T = 20°C, R.H. 60%) are characterized by strength greater than 15% compared to that of wet cured mixture. On the contrary, mixtures containing SCMs show more marked differences between wet and dry curing. Finally, total replacement of OPC with CSA:SCM:CH:CS̅ determines a sharp reduction in greenhouse gases emissions and energy requirement up to 60% at equal strength class respect to reference OPC-mixture.