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.

scholarly journals A Systematic Study on Polymer-Modified Alkali-Activated Slag–Part II: From Hydration to Mechanical Properties

Materials ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 3418 ◽  
Author(s):  
Zichen Lu ◽  
Jan-Philip Merkl ◽  
Maxim Pulkin ◽  
Rafia Firdous ◽  
Steffen Wache ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Pore Structure ◽  
Analytical Techniques ◽  
Hydration Products ◽  
Ion Diffusion ◽  
X Ray Diffraction ◽  
Alkali Activated Slag ◽  
Activated Slag ◽  
Alkali Activated ◽  
Polymer Latex

The effect of styrene-acrylate (SA) polymer latex on alkali-activated slag (AAS) was systematically studied in the aspects of hydration, hydration products, pore structure and mechanical properties through the combined analytical techniques including calorimetry, X-ray diffraction, thermogravimetric analysis, mercury intrusion porosimetry, and mechanical measurement. It was found that the addition of SA does not retard the AAS hydration, but slightly accelerates it, possibly due to the increasing ion diffusion through the loosely structured hydration products. Pore structure analysis indicates that the addition of polymer increases the cumulative pore volume and the portion of pores with size >100 nm in the hardened AAS paste. The addition of SA latex results in a continuous decrease of the compressive strength, but the flexural strength firstly increases and then decreases with the increase of polymer dosage. The polymer dosage of 2.5 wt % is optimal when applying polymer latex in the AAS system in this study.

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 Effect of CaSO4 Incorporation on Pore Structure and Drying Shrinkage of Alkali-Activated Binders

Materials ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1673 ◽  
Author(s):  
Hyeongmin Son ◽  
Sol Moi Park ◽  
Joon Ho Seo ◽  
Haeng Ki Lee
Keyword(s):  
Fly Ash ◽  
Pore Structure ◽  
Drying Shrinkage ◽  
Phase Changes ◽  
X Ray Diffraction ◽  
Activated Slag ◽  
Capillary Tension ◽  
Alkali Activated Binders ◽  
Internal Pore Structure ◽  
Alkali Activated

This present study investigates the effects of CaSO4 incorporation on the pore structure and drying shrinkage of alkali-activated slag and fly ash. The slag and fly ash were activated at a 5:5 ratio by weighing with a sodium silicate. Thereafter, 0%, 5%, 10%, and 15% of CaSO4 were incorporated to investigate the changes in phase formation and internal pore structure. X-Ray Diffraction (XRD), thermogravimetry (TG)/derivative thermogravimetry (DTG), mercury intrusion porosimetry (MIP), nuclear magnetic resonance (NMR), and drying shrinkage tests were carried out to find the correlation between the pore structure and drying shrinkage of the specimens. The results showed that CaSO4 incorporation increased the formation of thenardite, and these phase changes affected the pore structure of the activated fly ash and slag. The increase in the CaSO4 content increased the pore distribution in the mesopore. As a result, the capillary tension and drying shrinkage decreased.

scholarly journals Effect of Sodium Aluminate Dosage as a Solid Alkaline Activator on the Properties of Alkali-Activated Slag Paste

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Bin Chen ◽  
Jun Wang ◽  
Jinyou Zhao
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Setting Time ◽  
Sodium Aluminate ◽  
Hydration Reaction ◽  
Hydration Products ◽  
Alkali Activated Slag ◽  
Alkaline Activator ◽  
Activated Slag ◽  
Alkali Activated

Extensive research into alkali-activated slag as a green gel material to substitute for cement has been done because of the advantages of low-carbon dioxide emissions and recycling of industrial solid waste. Alkali-activated slag usually has good mechanical properties, but the too fast setting time restricted its application and promotion. Changing the composition of alkaline activator could optimize setting time, usually making it by adding sodium carbonate or sodium sulfate but this would cause insufficient hydration reaction power and hinder compressive strength growth. In this paper, the effect of sodium aluminate dosage as an alkaline activator on the setting time, fluidity, compressive strength, hydration products, and microstructures was studied through experiments. It is fair to say that an appropriate amount of sodium aluminate could obtain a suitable setting time and better compressive strength. Sodium aluminate provided enough hydroxyl ions for the paste to promote the hydration reaction process that ensured obtaining high compressive strength and soluble aluminium formed precipitate wrapped on the surface of slag to inhibit the hydration reaction process in the early phase that prolonged setting time. The hydration mechanism research found that sodium aluminate played a key role in the formation of higher cross-linked gel hydration products in the late phase of the process. Preparing an alkali-activated slag with excellent mechanical properties and suitable setting time will significantly contribute to its application and promotion.

scholarly journals Effect of Rheology of Fresh Paste on the Pore Structure and Properties of Pervious Concrete Based on the High Fluidity Alkali-Activated Slag

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 593
Author(s):  
Haining Geng ◽  
Qing Xu ◽  
Saiful B. Duraman ◽  
Qiu Li
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Pore Structure ◽  
Water Permeability ◽  
Coarse Aggregate ◽  
Pervious Concrete ◽  
Alkali Activated Slag ◽  
Activated Slag ◽  
Alkali Activated

Pervious concrete is made of cementitious materials, coarse aggregate, water and additives, with characteristic macro- and meso-connected pore structure, which enables the acceptable mechanical properties and high water permeability for pavement and road applications. In this study, the effect of rheology of fresh alkali-activated slag paste on the sedimentation of paste on the bottom of pervious concrete, meso-structure, connected porosity, mechanical properties and water permeability was investigated by a range of analytical techniques through varying the equivalent alkali content to control the rheology of fresh paste in the pervious concrete. The compressive strength of pervious concrete was related to the percentage area of paste and the average thickness of paste on the surface of coarse aggregate. The tensile strength and water permeability were correlated to the connected porosity of pervious concrete and the rheology of fresh paste. A relative lower fluidity, higher viscosity and shear stress of fresh alkali-activated slag paste favoured lower sedimentation of paste on the bottom of pervious concrete, higher connected porosity, tensile strength and water permeability. There was no correlation between compressive strength and tensile strength of pervious concrete.

Effect of Curing Time on the Pore Structure of the Portland Cement Concrete

2010 ◽  
Vol 44-47 ◽  
pp. 2592-2596
Author(s):  
Wei Lun Wang ◽  
Peng Liu
Keyword(s):  
Compressive Strength ◽  
Portland Cement ◽  
Pore Structure ◽  
Mercury Intrusion Porosimetry ◽  
Curing Time ◽  
Hydration Products ◽  
Portland Cement Concrete ◽  
X Ray Diffraction ◽  
Cement Concrete ◽  
X Ray

In this paper, the influence of curing time on the compressive strength and pore structure of the Portland cement concrete was investigated. The phase composition and morphology of hydration products of Portland cement were analyzed with X-ray diffraction (XRD). In addition, the porosity and pore distribution of the concrete were also researched using mercury intrusion porosimetry (MIP), surface area and porosity analyzer (BET). The results show that the influence of curing time on the compressive strength and pore structure of the concrete is obvious. With curing time increasing, the compressive strength of the concrete increased and the porosity decreased. The corresponding fractal dimension of the pore and the microstructure were changed, as well. With time increasing, more hydration products were produced.

scholarly journals The Relationship between Compressive Strength and Pore Structure of the High Water Grouting Material

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 865
Author(s):  
Youmin Han ◽  
Junwu Xia ◽  
Linli Yu ◽  
Qiong Su ◽  
Xiaomiao Chen
Keyword(s):  
Compressive Strength ◽  
Pore Structure ◽  
Pore Diameter ◽  
High Water ◽  
Hydration Products ◽  
Characteristic Parameters ◽  
Grey Correlation ◽  
Grouting Material ◽  
Binder Ratio ◽  
The Relationship

To elucidate the relationship between compressive strength and pore structure of the high water grouting material with different water-binder ratios and CaO contents, the compressive strength was tested while pore structure including pore characteristic parameters and pore diameter distribution were investigated by BET, MIP, and 3D-XRM. Moreover, the evolution of hydration products was observed by TGA and SEM, illustrating the reactive mechanism of the material. Furthermore, the grey correlation coefficients between compressive strength and pore structure parameters were illustrated according to the grey correlation theory. The results show that CaO content in lime is proportional to the compressive strength with the water-binder ratio of 1.0 or 1.5, while the inverse trend appears with the water-binder ratio of 2.0. The high water grouting material belongs to the macropore material with the pores mainly within 100 nm to 2 μm. Its hydration products contain ettringite crystals, aluminum gels, and C-S-H gels. The productions of the hydration products are positively correlated with its compressive strength. In addition, the compressive strength of the high water grouting material is closely related to the pore characteristic parameters and the pore size distribution, especially the porosity, the most probable pore diameter, and the pore volumes within 100~500 nm and 10~100 nm.

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.

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