Setting of alkali-activated slag cement. Influence of activator nature

This study aims to investigate the effect of limestone powder (LP) on the reaction of sodium carbonate activated slag. The results show that the incorporated LP up to 30% improves the strength development, especially at advanced curing ages. A slightly accelerated reaction is observed for samples containing low amount of LP (B5%), while mixture with 10% LP shows the optimized results with respect to the heat release and strength development. Chemical effect of incorporating LP is observed at high replacement levels (C15%), indicated by the formation of a new phase, natron (Na 2 CO 3 Á10H 2 O). Besides, relatively high contents of hydrotalcite-like phases are generated when increasing the dosage of limestone powder. The chemical changes, including the volume changes of generating natron and the transformation of natron to calcite, is potentially responsible for the enhanced mechanical properties.

Section: Compressive Strengthmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Assessing the chemical involvement of limestone powder in sodium carbonate activated slag

Yuan

Brouwers

2017

“…Although alkali-activated slag (AAS) cements can be produced with much lower global warming potentials than Portland cement (PC) [4], the use of sodium hydroxide and sodium silicate as activators can bring higher impacts than that of PC in other environmental aspects, including human toxicity, fresh water and marine ecotoxicity [4][5][6]. In the search for more cost-effective, low-toxicity and environmentally friendly alternatives, the use of nearneutral salts such as sodium carbonate as activators for blast furnace slag has attracted the attention of academia and industry [7][8][9][10][11][12][13][14]. However, the factors controlling the durability and mechanical performance of sodium carbonate-activated slag cement are not yet fully understood.…”

Section: Introductionmentioning

confidence: 99%

Chloride binding and mobility in sodium carbonate-activated slag pastes and mortars

Bernal

Hussein

et al. 2017

This study evaluates the chloride binding capacity and the migration of chloride in sodium carbonate-activated slag cements and mortars. The effect on chloride mobility and binding of adding a calcined layered double hydroxide (CLDH) to the binder mix was also assessed. Significantly improved durability characteristics can be achieved for sodium carbonate-activated slag mortars by the addition of small fractions of CLDH, as a consequence of a higher degree of reaction, higher chloride binding capacity, and the refined pore structures present in these modified materials, in comparison with alkali-activated cements produced without CLDH. The addition of CLDH enables the production of sodium carbonateactivated slag cements with notably reduced chloride ingress compared to silicate activated slag cements.

“…It is known that the reaction products, mechanical properties and durability of AAS significantly differ with different activators applied [4,5]. The material properties of AAS together with the effect of additives [6][7][8][9] using various sole activators have been extensively reported.…”

Section: Introductionmentioning

confidence: 99%

Phase modification induced drying shrinkage reduction on Na2CO3 activated slag by incorporating Na2SO4

Yuan

Brouwers

2017

This paper aims to study the phase modification, reaction kinetics, mechanical properties and drying shrinkage of sodium carbonate activated slag by incorporating sodium sulfate in the activator. The results show that the reaction process is firstly controlled by CO 3 2-anions, and later runs similar to that of sodium sulfate activation. Besides, the relatively unstable phase gaylussite, commonly found in the sodium carbonate activation, is not observed in the reaction products upon hybrid activation, and monosulfoaluminate rather than ettringite is identified, probably caused by the reduced aluminate-to-sulfate ratio and increased pH value. The drying shrinkage is considerably reduced by up to 41% when replacing 50 wt% sodium carbonate by sodium sulfate, most possibly attributed to the induced phase modification. Furthermore, the relationships between the phase modification and drying shrinkage, and the potentially involved chemical reaction are discussed.