Portland metakaolin cement containing dolomite or limestone – Similarities and differences in phase assemblage and compressive strength

Abstract

The scarceness of high-quality limestone obliges the cement industry to consider alternative supplementary cementitious materials (SCMs) for the production of blended cements. This study investigated the potential usage of dolomite instead of limestone as an addition to Portland metakaolin cement by measuring the development of the compressive strength and phase assemblages at 5 °C, 20 °C or 38 °C. Laboratory grade materials were used to identify potential differences in the impact of the carbonate on the phase assemblages. As with limestone, a strength increase was observed when dolomite is added at temperatures >5 °C due to the formation of additional carbonate AFm phases and the stabilization of ettringite. Differences were observed in the amount and type of the carbonate AFm and AFt phases formed. Thermodynamic modelling in combination with the experimental results indicate that the dolomite and limestone affect Portland metakaolin cement in a similar way, with the reactivity being the major difference between the two carbonate sources. This indicates that with regard to the strength development up to 90 days dolomite can be used instead of limestone to replace parts of a Portland metakaolin cement.

Effects of Light-Burnt Dolomite Incorporation on the Setting, Strength, and Drying Shrinkage of One-Part Alkali-Activated Slag Cement

“…Hailong Ye et al [41] found that the incorporation of dolomite induced porosity reduction and strength development, by enhancing the reaction degree of slag because of a filler effect. Machner et al [47] showed similar enhancement of compressive strength results and attributed the compressive strength development to the use of dolomite through carbonate addition. The addition of dolomite induced an ettringite stabilization effect and the formation of carbonate AFm phases.…”

Recycling Blast Furnace Ferronickel Slag as a Replacement for Paste in Mortar: Formation of Carboaluminate, Reduction of White Portland Cement, and Increase in Strength

“…Meanwhile, the diffraction peak of the ettringite in Figure 8 was clearly detected since the available CO 3 2− dissolved from the calcite could restrain the transformation of the ettringite into the Ms; thus, it indirectly stabilized the existence of the ettringite although the gypsum as the source of sulfate was depleted [32,39]. This chemical process respectively increased the bulk of the total hydration products and thus was beneficial to refining the microstructure and increasing the strength of the mortar [38].…”

Calcined Clay as Supplementary Cementitious Material

“…Machner et al [ 142 ] have studied the possibility of using dolomite to replace limestone as a third component in mixtures with OPC and metakaolin. The test mixtures were composed of Portland clinker, dolomite, limestone, metakaolin and gypsum.…”