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An overview of the effect of mineral additives on hydration reactions in ternary cement systems is of high importance for concrete design and durability. In this paper, the combination effect of limestone filler and slag on hydration reactions in ternary cements was investigated. Tests were carried out on cement pastes with various replacement levels of cement by limestone filler and slag (15, 25 and 45%) and two w/b ratios (0.35 and 0.48). The hydration reactions of ternary cement pastes were evaluated by measuring their degree of reaction at 7, 28 and 90 days. The degree of reaction was followed by thermogravimetric analysis (TGA) method. The results showed that the reaction degree was dependent on the replacement level and w/b ratio. The hydration heat and the compressive strength were further examined to verify the results obtained. Both hydration heat and compressive strength were found to be proportional to the reaction degree. [ABSTRACT FROM AUTHOR]

The global cement industry is striving to reduce its carbon footprint. Common approaches have included reduced clinker factors by blending cement clinker with supplementary cementitious materials (SCM). However supplies of SCMs are not sufficient to achieve replacement above about 30%. Limestone ternary cements offer the opportunity to reduce the clinker factor of cements while maximizing the efficiency of SCMs. In these cements, calcite from limestone reacts with dissolved aluminates to form carboaluminate and in the process influence hydration of other constituents. However, sulfates which are conventionally added to regulate the early reactions in cement also compete for aluminates. Here we have used complementary techniques to investigate the effects of calcium sulfate additions on hydration, microstructure and performance of composite Portland clinker-slag-limestone cements. The results show that the presence of sulfate influenced the early-age reaction kinetics of the clinker phases and supplementary cementitious materials. However, even after sulfate depletion, the course of hydration and microstructures formed were significantly influenced. Increasing the sulfate level resulted in a gradual increase of the fraction of ettringite over AFm phases, coarser porosity and lower water content of the C-S-H. These microstructural changes impact the total porosity and hence cement strength in opposing ways, namely porosity is reduced with increasing ettringite fraction while the space filling capacity of the C-S-H is also reduced due to the lower water content of the C-S-H. These findings have important implications for optimizing the mechanical properties and durability of ternary blends. [ABSTRACT FROM AUTHOR]

• The reaction between aluminates of SSA and limestone leads to the formation of carboaluminates. • The formation of carboaluminate phases refines the pore structure and promotes the strength development. • The dissolution of SSA changes the composition of C-A-S-H in ternary blended cements. The hydration kinetics and phase assemblage of ternary blended cements composed of sewage sludge ash (SSA) and limestone were investigated. Isothermal calorimetry reveals an inhibition effect of SSA on the hydration of C 3 S within the first day, while the hydration degree of C 3 S in ternary blended cements exceeds that in PC after 3 days. The reaction between SSA and limestone generates additional carboaluminate phases and inhibits the transformation of AFt to monosulfate, increasing the stability of AFt. This reaction is reflected on the second peak in the deceleration period of heat flow curves. The generation of a large amount of carboaluminate phases has a significant effect on porosity refinement and strength development of ternary blended cements. The pozzolanic reaction of SSA generates C-(A)-S-H with high Si/Ca and Al/Ca atomic ratios. Iron from the dissolution of SSA is captured by C-(A)-S-H, leading to the increase in Fe/Ca atomic ratios of C-(A)-S-H. [ABSTRACT FROM AUTHOR]

While there is ample information in the literature on the mechanical performance and durability of concrete made with either limestone or granulated blast furnace slag,very little is known about the effect of the combined action of these two additions on concrete properties. The present paper evaluates the early stage properties and mechanical strength of binary and ternary cement concrete containing up to 18% limestone and 20% granulated blast furnace slag. The results show that the use of ternary cements has no substantial effect on concrete setting time, although it does reduce bleeding and enhance mechanical strength with respect to unadditioned Portland and/or binary cement concrete.

The behavior of ternary blended cements with limestone filler and fly ash additions into 5% magnesium sulfate solution was evaluated. The presence of both limestone and fly ash in cement does not seem to decrease the vulnerability of cements to magnesium sulfate attack at 5 °C in comparison with limestone filler or fly ash cements. After 90 days, the compressive strengths decrease for all specimens (from 33.5 MPa to 16.4 MPa for Portland cement mortar and from 35 MPa to 13.8 MPa for 10% fly ash cement mortar) as a consequence of higher amount of deterioration products which exerts pressure in the capillare pores. [ABSTRACT FROM AUTHOR]

Mineral admixtures are blended with Portland cement to improve strength and durability, and/or to reduce the cost and environmental footprint of concrete mixes. Some mineral admixtures such as fly ash have also been reported to enhance workability of blended cements. This study shows that the key parameter controlling the yield stress of ternary Portland cement-blast furnace slag-fly ash pastes, in the absence of an added rheology-modifying admixture, is the width of the particle size distribution (PSD) at a given water/solid mass ratio. A small addition of fly ash has a significant effect on workability because of its broad PSD, and any other precursors with a similar PSD could possibly have a comparable effect. A model to predict the yield stress is therefore derived based on the Rosin-Rammler PSD width parameter, n, and the water/solid mass ratio, which provides a good description of the experimental yield stress data. It is believed that a broader PSD provides a higher packing density of particles which reduces the volume of water volume required to fill the voids. The excess water is then used to disperse particles and reduces inter-particle forces, hence yield stress. Therefore, at a given water/solid ratio, PSD width is able to be used as a sole parameter to correlate the yield stress of such concentrated suspensions. Also, a very low yield stress can be approached if the PSD is broad enough, in the absence of any rheology-modifying admixtures. [ABSTRACT FROM AUTHOR]