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.

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 Investigation of the Effects of Magnesium-Sulfate as Slag Activator

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 305 ◽  
Author(s):  
Choonghyun Kang ◽  
Taewan Kim
Keyword(s):  
Compressive Strength ◽  
Pore Structure ◽  
Magnesium Sulfate ◽  
Great Influence ◽  
Hydration Products ◽  
X Ray Diffraction ◽  
Binder Ratio ◽  
Mechanical And Microstructural Properties ◽  
Activated Slag ◽  
Alkali Activated

This study is about the mechanical and microstructural properties of alkali-activated slag (AAS) paste using magnesium sulfate (MS) as an activator. MS is 2%, 4%, 6%, 8% and 10% contents of binder weight and water-binder ratio is 0.35. Compressive strength, X-ray diffraction, mercury-intrusion porosimetry, and thermal analysis were performed for analysis. The MS contents at which the maximum compressive strength appeared varied according to the measurement age. Hydration products affecting compressive strength and pore structure were ettringite and gypsum. As a result, the changes of ettringite and gypsum depending on the contents of MS have a great influence on the pore structure, which causes the change of compressive strength. The high MS contents increases the amount of gypsum in the hydration products, and the excess gypsum causes high expansion, which increases the diameter and amount of pores, thereby reducing the compressive strength.

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 Effects of the alkaline solution/binder ratio and curing condition on the mechanical properties of alkali-activated fly ash mortars

2017 ◽  
Vol 24 (5) ◽  
pp. 773-782
Author(s):  
Maochieh Chi
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Fly Ash ◽  
Alkaline Solution ◽  
Drying Shrinkage ◽  
Strength Development ◽  
Initial Surface ◽  
Binder Ratio ◽  
Curing Condition ◽  
Alkali Activated

AbstractThe study investigates the effects of the alkaline solution/binder ratio and the curing condition on the mechanical properties of alkali-activated fly ash (AAFA) mortars. Class F fly ash was used as the raw material, and sodium hydroxide and liquid sodium silicate were used for the preparation of alkaline activators. Three alkaline solution-to-binder ratios (0.35, 0.5, and 0.65) and four different initial curing conditions (curing in air at ambient temperature for 24 h, 30°C for 24 h, 65°C for 12 h, and 85°C for 6 h) were considered. Test results show that AAFA mortars with alkaline solution-to-binder ratio of 0.35 had higher compressive strength, lower drying shrinkage, lower water absorption, and lower initial surface absorption rate than the other mortars. Furthermore, the curing condition influenced the compressive strength development and drying shrinkage of AAFA mortars at early ages. AAFA mortars cured at 65°C for 12 h appeared to have superior mechanical properties. XRD demonstrates that the hydration products of AAFA mortars are mainly amorphous alkaline aluminosilicate gel, which attributed to the compressive strength. Consequently, the alkaline solution-to-binder ratio significantly affects more the mechanical properties than the curing condition based on the presented results.

Properties of Mortar Containing Rice Husk Ash at Different Temperature and Exposed to Aggressive Environment

2012 ◽  
Vol 620 ◽  
pp. 87-93 ◽  
Author(s):  
Ramadhansyah Putra Jaya ◽  
Mohd Al Amin Muhamad Nor ◽  
Zainal Arifin Ahmad ◽  
Zakaria Mohd Amin
Keyword(s):  
Compressive Strength ◽  
Rice Husk ◽  
Rice Husk Ash ◽  
X Ray Diffraction ◽  
X Ray ◽  
Compressive Strength Test ◽  
Binder Ratio ◽  
Different Temperatures ◽  
Good Potential ◽  
Water To Binder Ratio

The properties of mortar containing rice husk ash at varying temperatures were studied. Three rice husk ash samples were prepared at different temperatures and with various colors, i.e., 600°C (pink), 800°C (grey), and 1000°C (white), all were used for this study. Ordinary Portland cement (OPC), a well known universal binder, was partially replaced with rice husk ash at 10, 15, 20, and 30% by weight of binder. The water to binder ratio (W/B) of the mortar was kept constant at 0.45. The mortars were subjected to seawater or saturated Ca (OH)2 solution. The controlled and exposed mortars were characterized using X-ray diffraction, FTIR spectroscopy and compressive strength test. The results show that the amount of silica present in RHA are varied with burning temperature and colors, approximately in the range of 95 to 97%. White RHA produced higher compressive strength both in seawater and Ca (OH)2 solution. Finally, white RHA with 15% replacement was most suitable to be used as additive in OPC, and showed good potential for use in seawater applications and alkaline environment.

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