Ordinary Portland Cement composition for the optimization of the synergies of supplementary cementitious materials of ternary binders in hydration processes

Abstract

The synergistic effects of using several supplementary cementitious materials (SCMs), such as Blast Furnace Slags plus Limestone Filler or Fly Ashes, depend on the OPC composition. When using an OPC which is poor in C 3 A and alkalis in ternary formulations, a similar initial strength gain to that of a plain OPC is detected and at longer hydration ages, the formation of monocarboaluminate, hemicarbonate and hydrotalcite instead of monosulphate can be seen. If an OPC with a higher C 3 A content and alkalis is used with SCMs, the higher availability of Al causes the early formation of monocarboaluminate and a lower initial strength gain. At longer hydration times, in ternary blends with both OPCs, the mechanical strengths are higher and the C-S-H gels formed are richer in Al and poorer in C/S ratio with a subsequent lowering of the alkali content in the pore solution when compared to that in plain OPC.

Influence of the synergy between mineral additions and Portland cement in the physical-mechanical properties of ternary binders

“…mixed with BFS and FA resulted in 32-59% lower compressive strength than for the plain PC after 7 days of hydration. In contrast, Menéndez et al (15) saw that ternary blends using PC with 2% C 3 A, LF and BFS showed better strength than binary blends and similar than plain PC during hydration from 1 to 90 days, which were attributed to the LF at early ages and to the BFS hydration at long term (11,15,21). The good mechanical strength of the ternary blends at long term has been also related to the refinement of the pore structure (21-23) which has a further positive response on durability (26).…”

“…The good mechanical strength of the ternary blends at long term has been also related to the refinement of the pore structure (21-23) which has a further positive response on durability (26). Besides, present authors in a previous paper (21) found that ternary blends with high blended content formed more C-S-H that contained more Al and less C/S ratio than C-S-H gels formed with plain PC and retained more alkalis in their structure.…”

“…Different causes can be contributing to this fact, the LF at early ages favors higher effective water/PC ratio for reaction and provides additional sites for the nucleation of hydration products (30,31). Besides, the BFS also contributes to accelerate the clinker hydration (19), but its role depends on the PC composition as found in (21). In fact, higher portlandite content was detected at early ages of hydration with PC L 30BFS6LF but lower content in Al and Si in the pore solution with respect to PC H 30BFS6LF.…”

“…Different studies showed that ternary blends using PC with relatively high alkali and C 3 A content had lower initial mechanical strength than plain PC (5,18,19,22,24), while in mixes with PC containing low alkali and/or C 3 A content this effect is less relevant (11,15,20,21,23,25). Dehuai and Zhaoyuan (24) found that in ternary blends composed of 50-70% PC with 8% C 3 A and 0.9% Na 2 O eq .…”

“…This effect is more relevant when additions with different hydration mechanism are combined (11,15,(17)(18)(19)(20)(21)(22)(23). The future of CEN (European Committee for Standardization) is on the way to include the ternary blends in the standards (9).…”