scholarly journals Influence of Na2O Content and Ms (SiO2/Na2O) of Alkaline Activator on Workability and Setting of Alkali-Activated Slag Paste

Materials ◽  
2019 ◽  
Vol 12 (13) ◽  
pp. 2072 ◽  
Author(s):  
Sung Choi ◽  
Kwang-Myong Lee
Keyword(s):  
Setting Time ◽  
High Strength ◽  
Abrupt Decrease ◽  
Na2o Content ◽  
Alkali Activated Slag ◽  
Granulated Blast Furnace Slag ◽  
Type Composition ◽  
Activated Slag ◽  
Binary Alkaline ◽  
Alkali Activated

The performance of alkali-activated slag (AAS) paste using activators of strong alkali components is affected by the type, composition, and dosage of the alkaline activators. Promoting the reaction of ground granulated blast furnace slag (GGBFS) by alkaline activators can produce high-strength AAS concrete, but the workability might be drastically reduced. This study is aimed to experimentally investigate the heat release, workability, and setting time of AAS pastes and the compressive strength of AAS mortars considering the Na2O content and the ratio of Na2O to SiO2 (Ms) of binary alkaline activators blended with sodium hydroxide and sodium silicate. The test results indicated that the AAS mortars exhibited a high strength of 25 MPa at 24 h, even at ambient temperature, even though the pastes with an Na2O content of ≥6% and an Ms of ≥1.0 exhibited an abrupt decrease in flowability and rapid setting.

scholarly journals A Review of Durability and Strength Characteristics of Alkali-Activated Slag Concrete

Materials ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1198 ◽  
Author(s):  
Osama Ahmed Mohamed
Keyword(s):  
Rapid Development ◽  
Setting Time ◽  
High Rate ◽  
Alkali Activation ◽  
Promising Alternative ◽  
Alkali Activated Slag ◽  
Granulated Blast Furnace Slag ◽  
High Alkalinity ◽  
Activated Slag ◽  
Alkali Activated

Alkali-activated slag (AAS) is a promising alternative to ordinary Portland cement (OPC) as sole binder for reinforced concrete structures. OPC is reportedly responsible for over 5% of the global CO2 emission. In addition, slag is an industrial by-product that must be land-filled if not re-used. Therefore, it has been studied by many investigators as environmentally friendly replacement of OPC. In addition to recycling, AAS offers favorable properties to concrete such as rapid development of compressive strength and high resistance to sulfate attack. Some of the potential shortcomings of AAS include high shrinkage, short setting time, and high rate of carbonation. Using ground granulated blast furnace slag (GGBS) as an alternative to OPC requires its activation with high alkalinity compounds such as sodium hydroxide (NaOH), sodium sulfate (Na2SO3), sodium carbonate (Na2CO3), or combination of these compounds such as NaOH and Na2SO3. The mechanism of alkali-activation is still not fully understood and further research is required. This paper overviews the properties, advantages, and potential shortcomings of AAS concrete.

scholarly journals Properties of Alkali-Activated Slag Paste Using New Colloidal Nano-Silica Mixing Method

Materials ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1571 ◽  
Author(s):  
Taewan Kim ◽  
Jae Hong Kim ◽  
Yubin Jun
Keyword(s):  
Substitution Rate ◽  
Setting Time ◽  
High Strength ◽  
Nano Silica ◽  
Replacement Rate ◽  
Substitution Method ◽  
Alkali Activated Slag ◽  
Activated Slag ◽  
Mixing Water ◽  
Alkali Activated

Previous studies of alkali-activated slag cement (AASC) using nano-silica have mentioned mostly powdered nano-silica and binder weight replacement methods, which have a rapid decrease in fluidity, a short setting time and a low nano-silica replacement rate (< 5%). In this study, colloidal nano-silica (CNS) was used and the mixing-water weight substitution method was applied. The substitution method was newly applied to improve the dispersibility of nano-silica and to increase the substitution rate. In the experiment, the CNS was replaced by 0, 10, 20, 30, 40, and 50% of the mixing-water weight. As a result, as the substitution rate of CNS increased, the fluidity decreased, and the setting time decreased. High compressive strength values and increased rates were also observed, and the diameter and volume of pores decreased rapidly. In particular, the increase of CNS replacement rate had the greatest effect on decrease of medium capillary pores (50–10 nm) and increase of gel pores (< 10 nm). The new displacement method was able to replace up to 50% of the mixing water. As shown in the experimental results, despite the high substitution rate of 50%, the minimum fluidity of the mixture was secured, and a high-strength and compact matrix could be formed.

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

Materials ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 2874 ◽  
Author(s):  
In Kyu Jeon ◽  
Jae Suk Ryou ◽  
Sadam Hussain Jakhrani ◽  
Hong Gi Kim
Keyword(s):  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Setting Time ◽  
Drying Shrinkage ◽  
Slag System ◽  
Strength Development ◽  
Alkali Activated Slag ◽  
Granulated Blast Furnace Slag ◽  
Activated Slag ◽  
Alkali Activated

This study investigates the potential of light-burnt dolomite (LBD) as a supplementary cementitious material with ground granulated blast furnace slag (GGBFS) and Ordinary Portland cement (OPC). In this work, LBD was substituted for up to 20% of GGBFS in sodium sulfate-activated slag systems. The effects of LBD incorporation on the flow, setting time, compressive and flexural strength development, and drying shrinkage were explored with, X-ray diffraction and thermogravimetric analyses. LBD incorporation resulted in greater strength development of an alkali-activated slag system. The optimum LBD content for strength development was 10%, regardless of ordinary Portland cement content. In addition, LBD decreased the drying shrinkage, accelerated the hydration process, and induced hydrotalcite formation, which can be attributed to the reactive MgO inside LBD.

Research on Set Retarder of High and Super High Strength Alkali -Activated Slag Cement and Concrete

2011 ◽  
Vol 477 ◽  
pp. 164-169 ◽  
Author(s):  
Chang Hui Yang ◽  
Fang Wu ◽  
Ke Chen
Keyword(s):  
Setting Time ◽  
High Strength ◽  
Heat Evolution ◽  
Strength Development ◽  
Slag Cement ◽  
Alkali Activated Slag ◽  
Negative Effect ◽  
Cement And Concrete ◽  
Activated Slag ◽  
Alkali Activated

The set of alkali-activated slag cement (AASC) and concrete and the measures for set-retarding were reviewed. Due to the fast set of high and super high strength alkali-activated slag cement and concrete, an inorganic compound set retarder YP-3 was developed. The effect of the retarder on setting time and strength as well as heat evolution of AASC were tested, and the mechanism of the retarder was analysed. Results show that the retarder can regulate the initial set of high strength AASC in the range of 29hrs with little negative effect on its strength development. The retarder could react with silicate ions from liquid to rapidly form a compact film in early age of hydration of AASC, the film covered the surface of slag and obstructed R+ and OH- in contact with slag particle directly. Consequently the set of AAC was delayed.

Experimental Study on Alkali-Activated Slag-Lithium Slag-Fly Ash Environmental Concrete

2011 ◽  
Vol 287-290 ◽  
pp. 1237-1240
Author(s):  
Lan Fang Zhang ◽  
Rui Yan Wang
Keyword(s):  
Experimental Study ◽  
Compressive Strength ◽  
Fly Ash ◽  
Setting Time ◽  
Alkali Activated Slag ◽  
Percent Increase ◽  
Compressive Strength Of Concrete ◽  
Activated Slag ◽  
Lithium Slag ◽  
Alkali Activated

The aim of this paper is to study the influence of lithium-slag and fly ash on the workability , setting time and compressive strength of alkali-activated slag concrete. The results indicate that lithium-slag and fly-ash can ameliorate the workability, setting time and improve the compressive strength of alkali-activated slag concrete，and when 40% or 60% slag was replaced by lithium-slag or fly-ash, above 10 percent increase in 28-day compressive strength of concrete were obtained.

scholarly journals Mitigating the Drying Shrinkage and Autogenous Shrinkage of Alkali-Activated Slag by NaAlO2

Materials ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 3499
Author(s):  
Bin Chen ◽  
Jun Wang ◽  
Jinyou Zhao
Keyword(s):  
Autogenous Shrinkage ◽  
Drying Shrinkage ◽  
Nitrogen Adsorption ◽  
Partial Substitution ◽  
Hydration Reaction ◽  
X Ray Diffraction ◽  
Na2o Content ◽  
Alkali Activated Slag ◽  
Activated Slag ◽  
Alkali Activated

The shrinkage of alkali-activated slag (AAS) is obviously higher than ordinary Portland cement, which limited its application in engineering. In this study, the effects of NaAlO2 in mitigating drying shrinkage and autogenous shrinkage of AAS were studied. To further understand the shrinkage mechanism, the hydration products and microstructures were studied by X-ray diffraction, scanning electron microscopy and nitrogen adsorption approaches. As the partial substitution rate of NaAlO2 for Na2SiO3 increased, the drying shrinkage and autogenous shrinkage reduced significantly. The addition of NaAlO2 could slow down the rate of hydration reaction and reduce the porosity, change the pore diameter and the composition of generated paste and cause more hydrotalcite and tetranatrolite generated—which contributed to reduced shrinkage. Additionally, raising the Na2O content rate caused obvious differences in drying shrinkage and autogenous shrinkage. As the Na2O content elevated, the drying shrinkage decreased and autogenous shrinkage increased. A high Na2O content would cause complete hydration reactions and provoke high autogenous shrinkage. However, incomplete hydration reactions left more water in the paste, and the evaporated water dramatically influenced drying shrinkage. The results indicate that addition of NaAlO2 could greatly mitigate the drying shrinkage and autogenous shrinkage of AAS.

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