Effect of calcium hydroxide on fresh state behavior of sodium carbonate activated blast furnace slag pastes

Aktürk, Büşra; Kizilkanat, Ahmet B.; Kabay, Nihat

doi:10.1016/j.conbuildmat.2019.03.328

Cited by 44 publications

(11 citation statements)

References 54 publications

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“…These phenomena could be attributed to the high degree of reaction between the activator and CRCF. In the aqueous solution, the CRCF directly reacted with Na 2 CO 3 and generated CaCO 3 , which resulted in the rapid consumption of CO 3 2− while also increasing the amount of OH − , which determined the dissolution degree of GBFS [ 6 ]. When the binders were activated by a low concentration (Na 2 O-E: 3%) of Na 2 CO 3 , insufficient CO 3 2− reacted with Ca 2+ released from CRCF, leading to a relatively low level of OH − in the aqueous solution.…”

Section: Resultsmentioning

confidence: 99%

“…The cementitious properties of GBFS are majorly determined by the type and concentration of activators due to GBFS dissolution, depending on the pH values of the pore solution [ 5 ]. With the development of AAS cements, many activators have been reported in previous studies, with sodium hydroxide (NaOH) and sodium silicate (Na 2 O·nSiO 2 ) being the most extensively applied activators, which can ensure that the GBFS is activated to a high degree [ 4 , 6 , 7 ]. However, the AAS mortars with activators of NaOH and Na 2 O·nSiO 2 tend to have a high cost, a rapid setting, and micro-cracking issues [ 8 , 9 ].…”

Section: Introductionmentioning

confidence: 99%

“…However, the AAS mortars with activators of NaOH and Na 2 O·nSiO 2 tend to have a high cost, a rapid setting, and micro-cracking issues [ 8 , 9 ]. In addition, a considerable carbon footprint is released in the manufacturing process of NaOH and Na 2 O·nSiO 2 [ 6 ], and, therefore, these activators contribute less to the sustainability of AAS cements.…”

Section: Introductionmentioning

confidence: 99%

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Accelerating the Reaction Kinetics of Na2CO3-Activated Slag Mortars by Calcined Recycled Concrete Fines

Wang

et al. 2022

Materials

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Sodium carbonate (Na2CO3), an environmentally friendly activator, has been shown to have vast potential for the development of sustainable alkali-activated slag mortars. However, Na2CO3-activated slag mortars exhibit a delayed reaction process and limited early-age strength development, restricting their wider application. In this work, the recycled concrete fines were calcined at a temperature of 800 °C for 1 h and then used as an auxiliary activator to improve the reaction kinetics of Na2CO3-activated slag mortars. The impact of the calcined recycled concrete fines (CRCF) dosage and Na2CO3 concentration on the compressive strength, hydration kinetics, and phase assemblage of mortars was evaluated. The results show that CRCF can react directly with Na2CO3 in the early stages, swiftly removing the CO32− in aqueous solution and providing an alkaline environment suitable for the dissolution of slag. This promotes the development of C-(A)-S-H, hydrotalcite, hemicarbonate, and monocarbonate. The hydration process and strength-giving phase of mortars can be improved further, as an increase in Na2CO3 concentration increases the initial alkaline content. Additionally, the most remarkable compressive strength value of 39.2 MPa was observed at 28 days in the mortar with 6% sodium oxide equivalent (Na2O-E) of Na2CO3 and 15% CRCF because of the synergistic effect of CRCF and Na2CO3.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Accelerating the Reaction Kinetics of Na2CO3-Activated Slag Mortars by Calcined Recycled Concrete Fines

Wang

et al. 2022

Materials

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“…Previously, Akturk and Kizilkanat [2] investigated the effect of Ca (OH) 2 on Na 2 CO 3 activated blast furnace slag and reported that the use of lime would decrease the concentration of CO 3 2-in the pore solution.…”

Section: Role Of Wifd and Na 2 Comentioning

confidence: 99%

The utilization of waste incineration filter dust (WIFD) in sodium carbonate activated slag mortars

Ling

Schollbach

Liu

et al. 2021

Construction and Building Materials

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“…Kovtun et al [ 29 ] enhanced the 1 day compressive strength of Na 2 CO 3 -activated slag concretes cured at ambient temperature up to 25 MPa via the additions of slaked lime (Ca(OH) 2 ) and silica fume. Akturk et al [ 30 ] observed that only the 3% Ca(OH) 2 addition promoted the hardening of the pastes within 6.5 h. Wang et al [ 31 ] revealed that the CaO addition was beneficial for the formation of C-A-S-H. Gao et al [ 32 ] suggested that the initial reaction between Ca(OH) 2 and Na 2 CO 3 was effective in removing the CO 3 2− ions in the aqueous phase to enhance the alkalinity. Besides CaO and Ca(OH) 2 , some Mg-rich auxiliary activators have also been reported to be effective in expediting the reaction kinetics.…”

Section: Introductionmentioning

confidence: 99%

Properties and Microstructure of Na2CO3-Activated Binders Modified with Ca(OH)2 and Mg(OH)2

Xie

Liu

2022

Materials

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Delayed strength development and long setting times are the main disadvantageous properties of Na2CO3-activated slag cements. In this work, combined auxiliary activators of Ca(OH)2 and Mg(OH)2 were incorporated in one-part Na2CO3-activated slag binders to accelerate the kinetics of alkali activation. The properties and microstructure evolution were investigated to clarify the reaction mechanism. The results showed that the additions of auxiliary activators promoted the hardening of the pastes within 2 h. The 28 days compressive strengths were in the range of 39.5–45.5 MPa, rendering the binders practical cementitious materials in general construction applications. Ca(OH)2 was more effective than Mg(OH)2 in accelerating the kinetics of alkali activation. The dissolution of Ca(OH)2 released more OH− and Ca2+ ions in the aqueous phase to increase alkalinity in the aqueous phase and promote the formation of the main binding gel phase of calcium-aluminosilicate hydrate (C-A-S-H). An increase in the Ca(OH)2/Mg(OH)2 ratios increased autogenous shrinkage and decreased drying shrinkage of the binders. The formation of a compact pore structure restricted the water evaporation from the binders during the drying procedure.

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Effect of calcium hydroxide on fresh state behavior of sodium carbonate activated blast furnace slag pastes

Cited by 44 publications

References 54 publications

Accelerating the Reaction Kinetics of Na2CO3-Activated Slag Mortars by Calcined Recycled Concrete Fines

Accelerating the Reaction Kinetics of Na2CO3-Activated Slag Mortars by Calcined Recycled Concrete Fines

The utilization of waste incineration filter dust (WIFD) in sodium carbonate activated slag mortars

Properties and Microstructure of Na2CO3-Activated Binders Modified with Ca(OH)2 and Mg(OH)2

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