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This study examines the role of cavitation in drying cementitious materials. Classical nucleation theory is used to understand and study the parameters that influence cavitation pressures. The water desorption isotherms indicate that both heterogeneous and homogeneous cavitation occur during the drying of saturated cement pastes and the commonly observed large moisture loss at 0.3 p v / p sat can be explained by homogeneous cavitation. The homogeneous cavitation is suggested to occur in the gel porosity of the inner product that is accesible by the interlayer spaces. The findings of this study indicate that it is important to consider the effects of cavitation for characterization of pore sizes from moisture desorption isotherms. [ABSTRACT FROM AUTHOR]

This study investigates the difference between the reactivity of slag in NaOH solution (w/s = 100) and in cement paste (w/b = 0.4). The reactivity of slag is much higher in NaOH solution than in cement paste. When the NaOH solution is saturated with portlandite, the rate of reaction of slag decreases to approach that in cement paste. This suggests that the slower reaction of slag in cement paste might be due to the presence of calcium ions released by the clinker phases. At 28 days, relative humidity measurements indicate that water is only present in pores less than 6 nm. Above 6 nm, hydration cannot take place due to the lack of water. From a thermodynamic point of view, the small size of water filled pores may slow down the slag reaction due to the high concentration of species in solution required for hydrate growth to balance the increase of the surface energy. [ABSTRACT FROM AUTHOR]

This study compares the influence of two limestone fineness on strength development and cement hydration. The replacement of clinker by 20% of fine limestone (d v,50 = 2 μm and SSA = 4,21 m2/g) gives similar strength development to PC up to 7 days. Fine limestone enhances cement hydration and offsets the dilution effect caused by the decrease of clinker amount. The accelerating effect of the limestone was explained by a higher degree of undersaturation with respect to C 3 S. The influence of coarse limestone (d v,50 = 130 μm and SSA = 0,46 m2/g) on cement hydration is limited to dilution effect. The combination of fine and coarse limestone was also studied. A linear correlation was obtained between strength and gel space ratio for all investigated systems. Furthermore, the results showed that despite the similarity of specific surface area, limestone is more effective than quartz for the enhancement of cement hydration. [ABSTRACT FROM AUTHOR]

The effect of additions of limestone and dolomite powder on the properties of blended cements cured at 40 and 60°C was investigated using a multi-method approach. The presence of limestone leads to the formation of hemi- and mono-carbonate and to the stabilization of ettringite at 40°C. An increase of temperature to 60°C results in the destabilization of ettringite and formation of monosulfate in the limestone cement. The dolomite is almost depleted in the cementitious matrix over the hydration time at the studied temperatures. As a result, the formation of hydrotalcite is observed which binds part of the alumina from clinker dissolution. At 60°C, no monosulfate is found and the CSH contains less alumina in the presence of dolomite in comparison to when limestone is present. The dolomite dissolution increases the strength at higher temperatures as a result of the additional hydrotalcite formation. [ABSTRACT FROM AUTHOR]

Ternary cements are a promising option to further reduce CO 2 emissions and environmental impact from cement production. The current study investigates in detail the impact of water to binder ratio (0.4, 0.5, 0.6) and curing temperature (5, 20, 40 °C) on the hydration kinetics of a ternary cement comprising clinker, slag and limestone in a 50:40:10 mass ratio, respectively. The results show that the water to binder ratio mainly affected the hydration degree of slow reacting phases, such as slag and belite, at later ages. The curing temperature accelerated the hydration of alite to a lesser extent than that of C 3 A and slag, which could lead to changes in the hydration reaction sequence at elevated curing temperatures. Elevated temperature curing did not lead to cross-over effects in terms of slag hydration degree at later ages but led to reductions in the portlandite and ettringite levels. • Higher water to binder ratio increased late age slag and belite reaction. • Higher curing temperatures strongly accelerated early age hydration of clinker and slag. • C 3 A,C 4 AF and slag hydration showed higher apparent activation energies than C 3 S. • Higher curing temperatures resulted in lower portlandite and ettringite levels. [ABSTRACT FROM AUTHOR]

Factors which could explain the slowing down of the metakaolin reaction in LC3 blends are investigated. Portlandite availability and the presence of aluminium ions in the pore solution are shown not to be limiting factors. Hydrates can only precipitate in solution filled pores. Internal relative humidity measurements indicate that at 28 days solution is present only in pores with radii below 13 nm. An enhancement of metakaolin reaction was obtained at late ages when the larger capillaries are filled with solution. The lower limit of the water filled pores was more difficult to analyse since there is a lack of precision in determining interfacial energies of hydrates and pore solution of the system. However, this study gives an indication of order of magnitude where the growth of hydrates could be slowed down. [ABSTRACT FROM AUTHOR]