scholarly journals Effects of CO2 Curing on Alkali-Activated Slag Paste Cured in Different Curing Conditions

Materials ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 3513 ◽  
Author(s):  
Yubin Jun ◽  
Seong Ho Han ◽  
Tae Yong Shin ◽  
Jae Hong Kim
Keyword(s):  
Compressive Strength ◽  
Co2 Concentration ◽  
Strength Development ◽  
X Ray Diffraction ◽  
Curing Conditions ◽  
Alkali Activated Slag ◽  
X Ray ◽  
Compressive Strength Development ◽  
Activated Slag ◽  
Alkali Activated

The effect of CO2 curing on alkali-activated slag paste activated by a mixture of sodium hydroxide and sodium silicate solutions is reported in this paper. The paste samples after demolding were cured in three different curing environments as follows: (1) environmental chamber maintained at 85% relative humidity (RH) and 25 °C; (2) 3-bar CO2 pressure vessel; and (3) CO2 chamber maintained at 20% CO2 concentration, 70% RH and 25 °C. The hardened samples were then subjected to compressive strength measurement, X-ray diffraction analysis, and thermogravimetry. All curing conditions used in this study were beneficial for the strength development of the alkali-activated slag paste samples. Among the curing environments, the 20% CO2 chamber was the most effective on compressive strength development; this is attributed to the simultaneous supply of moisture and CO2 within the chamber. The results of X-ray diffraction and thermogravimetry show that the alkali-activated slag cured in the 20% CO2 chamber received a higher amount of calcium silicate hydrate (C-S-H), while calcite formed at an early age was consumed with time. C-S-H was formed by associating the calcite generated by CO2 curing with the silica gel dissolved from alkali-activated slag.

scholarly journals Strength Development and Microstructure of Alkali-activated Slag-MgO in Air Curing Condition

2018 ◽  
Vol 186 ◽  
pp. 02003
Author(s):  
Chao-Lung Hwang ◽  
Duy-Hai Vo ◽  
Mitiku Damtie Yehualaw ◽  
Vu-An Tran
Keyword(s):  
Compressive Strength ◽  
Strength Development ◽  
X Ray Diffraction ◽  
Alkali Activated Slag ◽  
X Ray ◽  
Binder Ratio ◽  
Curing Condition ◽  
Activated Slag ◽  
Water To Binder Ratio ◽  
Alkali Activated

The aim of this study is to analysis the effect of MgO on strength development and microstructure of alkali-activated slag (AAS) in air curing condition. Four mixtures of AAS are prepared using different MgO content (0%, 5%, 10%, and 15 % by weight of slag) at water to binder ratio of 0.4. The flow, compressive strength, scanning electron microscopy, and X-ray diffraction are tested under relevant standards. The addition of MgO significantly accelerated the hydration rate of AAS. AAS with adding MgO tended to increase the compressive strength and to reduce the flow. The higher adding MgO content was associated with higher hydrotalcite-like phase (Ht) formation which improved the microstrure of AAS in the air curing condition.

Effect of Steel Fiber Volume Fraction and Curing Conditions on the Compressive Behavior of Alkali-Activated Slag Concrete

2014 ◽  
Vol 525 ◽  
pp. 491-494
Author(s):  
Dae Hyun Kang ◽  
Hye Ran Kim ◽  
Hyun Do Yun
Keyword(s):  
Compressive Strength ◽  
Fiber Volume Fraction ◽  
Steel Fiber ◽  
Volume Fraction ◽  
Compressive Behavior ◽  
Fiber Volume ◽  
Curing Conditions ◽  
Alkali Activated Slag ◽  
Activated Slag ◽  
Alkali Activated

In this paper, an experimental investigation was carried out to examine the influence of hooked end steel fiber volume fraction and curing conditions on the compressive performance of concrete produced by using ordinary portland cement (OPC) and alkali-activated slag (AAS). Three different volume fractions of 0.5%, 1.0% and 1.5% were used in OPC and AAS concrete mixtures. Cylindrical specimens with 100 x 200mm were tested for compressive behavior of both concretes at 3, 7 and 28 days of curing age. Test results showed that curing conditions had a significant effect on compressive properties in the hardened OPC and AAS concretes. The addition of steel fibers generated a decrease in compressive strength of OPC while an increase in the compressive strength of AAS concrete was shown with adding steel fiber.

Preparation and Composition Optimization of Low-CO2-Emission Cement Containing Belite, Calcium Sulfoaluminate and Ferrite

2017 ◽  
Vol 727 ◽  
pp. 1067-1073 ◽  
Author(s):  
Wu Yao ◽  
Qiao Ling ◽  
Meng Xue Wu
Keyword(s):  
Compressive Strength ◽  
Cement Clinker ◽  
Strength Development ◽  
Optimal Composition ◽  
X Ray Diffraction ◽  
Scattered Electron ◽  
X Ray ◽  
Calcium Sulfoaluminate ◽  
Compressive Strength Development ◽  
Composition Optimization

Cement clinker with low CO2 emission was prepared in laboratory, which mainly consist of belite (C2S), calcium sulfoaluminate (C4A3S), and ferrite (C4AF). The mineral composition of clinker was optimized for better compressive strength development. The chemical and physical properties of this prepared cement were characterized through X-ray diffraction (XRD), back scattered electron-scanning electron microscopy (BSE-SEM) and differential thermal analysis (DTA). The results reveal that C4A3S governs most of the compressive strength at early ages, while C2S contributes to the later strength development. C4AF is in liquid when fired to 1300°C, beneficial to the mass transfer but causing high crystallinity of C2S when excessive. Finally the results of experiments suggest that the optimal composition of clinker is 50wt. % C2S, 40wt. % C4A3S and 10wt. % C4AF.

Shrinkage-Reducing Admixture Efficiency in Alkali-Activated Slag across the Different Doses of Activator

2018 ◽  
Vol 761 ◽  
pp. 19-22 ◽  
Author(s):  
Vlastimil Bílek Jr. ◽  
Lukáš Kalina ◽  
Ondřej Fojtík
Keyword(s):  
Compressive Strength ◽  
Drying Shrinkage ◽  
Strength Development ◽  
Alkali Activated Slag ◽  
Reducing Ability ◽  
Wide Range ◽  
Shrinkage Reducing Admixture ◽  
Negative Effect ◽  
Activated Slag ◽  
Alkali Activated

One of the largest obstacles for the wider use of alkali-activated slag (AAS) in a building industry is its severe drying shrinkage. According to some studies shrinkage-reducing admixtures (SRAs) could be a solution of this problem, but they were also reported to have a fatal impact on AAS hydration resulting in a serious strength development slowdown. The aim of this paper was to investigate this phenomenon in a wide range of the waterglass doses (4–12% Na2O of the slag mass). Mortars without and with 2% of SRA based on hexylene glycol were prepared and their shrinkage and compressive strength development was tested. By far the highest shrinkage reduction was observed for the lowest doses of waterglass, but these were also the cases of the highest compressive strength decrease. However, it is possible to suppress the negative effect of SRA on AAS strength development through the activator dose increase with certainly decreased shrinkage reducing ability of SRA.

scholarly journals The Effect of Different Types of Internal Curing Liquid on the Properties of Alkali-Activated Slag (AAS) Mortar

2021 ◽  
Vol 13 (4) ◽  
pp. 2407
Author(s):  
Guang-Zhu Zhang ◽  
Xiao-Yong Wang ◽  
Tae-Wan Kim ◽  
Jong-Yeon Lim ◽  
Yi Han
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Deionized Water ◽  
Internal Curing ◽  
Control Group ◽  
Alkali Activated Slag ◽  
Different Types ◽  
Naoh Solution ◽  
Activated Slag ◽  
Alkali Activated

This study shows the effect of different types of internal curing liquid on the properties of alkali-activated slag (AAS) mortar. NaOH solution and deionized water were used as the liquid internal curing agents and zeolite sand was the internal curing agent that replaced the standard sand at 15% and 30%, respectively. Experiments on the mechanical properties, hydration kinetics, autogenous shrinkage (AS), internal temperature, internal relative humidity, surface electrical resistivity, ultrasonic pulse velocity (UPV), and setting time were performed. The conclusions are as follows: (1) the setting times of AAS mortars with internal curing by water were longer than those of internal curing by NaOH solution. (2) NaOH solution more effectively reduces the AS of AAS mortars than water when used as an internal curing liquid. (3) The cumulative heat of the AAS mortar when using water for internal curing is substantially reduced compared to the control group. (4) For the AAS mortars with NaOH solution as an internal curing liquid, compared with the control specimen, the compressive strength results are increased. However, a decrease in compressive strength values occurs when water is used as an internal curing liquid in the AAS mortar. (5) The UPV decreases as the content of zeolite sand that replaces the standard sand increases. (6) When internal curing is carried out with water as the internal curing liquid, the surface resistivity values of the AAS mortar are higher than when the alkali solution is used as the internal curing liquid. To sum up, both NaOH and deionized water are effective as internal curing liquids, but the NaOH solution shows a better performance in terms of reducing shrinkage and improving mechanical properties than deionized water.

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.

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