Variation in Polymerization Degree of C-A-S-H Gels and Its Role in Strength Development of Alkali-activated Slag Binders

2021 ◽  
Vol 36 (6) ◽  
pp. 871-879
Author(s):  
Qing Liu ◽  
Jiakang Zhang ◽  
Yuewei Su ◽  
Xianjun Lü
Keyword(s):  
Strength Development ◽  
Polymerization Degree ◽  
Alkali Activated Slag ◽  
Activated Slag ◽  
Alkali Activated

scholarly journals Sustainable batching water options for one-part alkali-activated slag mortar: Sea water and reverse osmosis reject water

PLoS ONE ◽  
2020 ◽  
Vol 15 (11) ◽  
pp. e0242462
Author(s):  
Tero Luukkonen ◽  
Juho Yliniemi ◽  
Paivo Kinnunen ◽  
Mirja Illikainen
Keyword(s):  
Reverse Osmosis ◽  
Sea Water ◽  
Strength Development ◽  
Alkali Activation ◽  
Similar Amount ◽  
Alkali Activated Slag ◽  
Reject Water ◽  
Concrete Production ◽  
Activated Slag ◽  
Alkali Activated

Concrete production is globally a major water consumer, and in general, drinking-quality water is mixed in the binder. In the present study, simulated sea water and reverse osmosis reject water were used as batching water for one-part (dry-mix) alkali-activated blast furnace slag mortar. Alkali-activated materials are low-CO2 alternative binders gaining world-wide acceptance in construction. However, their production requires approximately similar amount of water as regular Portland cement concrete. The results of the present study revealed that the use of saline water did not hinder strength development, increased setting time, and did not affect workability. The salts incorporated in the binder decreased the total porosity of mortar, but they did not form separate phases detectable with X-ray diffraction or scanning electron microscopy. Leaching tests for monolithic materials revealed only minimal leaching. Furthermore, results for crushed mortars (by a standard two-stage leaching test) were within the limits of non-hazardous waste. Thus, the results indicated that high-salinity waters can be used safely in one-part alkali-activated slag to prepare high-strength mortars. Moreover, alkali-activation technology could be used as a novel stabilization/solidification method for reverse osmosis reject waters, which frequently pose disposal problems.

Strength Development and Pore Structure of Alkali-Activated Slag Cement in Bittern Environment

2014 ◽  
Vol 584-586 ◽  
pp. 1440-1443
Author(s):  
Qiang Song ◽  
Jian Hui Zhu ◽  
Xiao Yan Zhang
Keyword(s):  
Pore Structure ◽  
Pore Volume ◽  
Total Pore Volume ◽  
Experimental Results ◽  
Strength Development ◽  
Soaking Time ◽  
Alkali Activated Slag ◽  
Chemical Attack ◽  
Activated Slag ◽  
Alkali Activated

The effect of bittern on alkali-activated slag (AAS) cement and OPC was studied by testing on the strength and pore structure of the specimens stored in artificial bittern solution at certain periods. The experimental results show that the (AAS) cement exhibits excellent resistance to chemical attack of bittern. The significant increase of strength of (AAS) mortar stored in bittern solution was observed with the soaking time, and the strength increases very quickly before 27 d. But the strength of OPC decreases fast after17d. The more the contents of NaOH activator in AAS cement, the more the strength gained. And the more the contents of activator, the less porosity is. Curing the AAS cement in bittern environment leads to a reduction in the total pore volume and to a refinement of the pore structures.

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.

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 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.

Sign in / Sign up

Export Citation Format

Share Document