Thermal Activation on Phase Formation of Alkaline Activated Kaolin Based System

2013 ◽  
Vol 770 ◽  
pp. 262-266 ◽  
Author(s):  
Somsak Boonjaeng ◽  
Kedsarin Pimraksa ◽  
Arnon Chaipanich ◽  
Sutin Kuharuangrong ◽  
Prinya Chindaprasirt
Keyword(s):  
Calcium Silicate ◽  
Calcium Silicate Hydrate ◽  
Thermal Activation ◽  
Pozzolanic Reaction ◽  
Zeolite X ◽  
High Concentration ◽  
Phase Development ◽  
Naoh Solution ◽  
Calcium Aluminosilicate ◽  
Alkali Activated

The research aim was to investigate phase development after pozzolanic reaction between metakaolin (MK) and calcium hydroxide (CH) with alkaline and thermal activations. The CH to MK ratio (C/M) of 0.4 generating CaO/SiO2 of 1.18 was selected in this study. Various concentrations of NaOH solutions (0.01, 0.1, 1, 3, 5 and 10 M) were used. The alkali activated samples were thermally activated at 25 °C, 70 °C, 90 °C and 130 °C for 4 h. Phase development under thermal activation of alkali activated metakaolin based system were investigated. At every temperature, C/M mixtures with 0.01 and 0.1 M NaOH promoted the formations of poorly crystalline calcium silicate hydrate (C-S-H(I)) and calcium aluminosilicate hydrate (CASH) compounds. With 3 and 5 M NaOH activations, sodium aluminosilicate hydrate (NASH) and sodium calcium silicate hydrate (NCSH) was formed. 1 M NaOH was found to be a boundary of phase transformation from C-S-H(I) and CASH to NASH and NCSH. In addition, zeolite X and sodalite appeared when NaOH solution reached 10 M. Thermal activation significantly affected phase development at high concentration of alkaline activation (1-10 M). At 1 M NaOH, NASH compounds in a form of gmelinite and zeolite ZK-14 were found at 70-90 °C. At 3-5 M, katoite was found at 70-130 °C. At 10 M, zeolite X was found at 70-90 °C. Sodalite was also found at 130 °C with 10 M NaOH.

Micromechanical Properties of Calcium Silicate Hydrate

2013 ◽  
Vol 539 ◽  
pp. 75-79
Author(s):  
Wu Yao ◽  
Li He
Keyword(s):  
Fly Ash ◽  
Reaction Zone ◽  
Calcium Silicate ◽  
Calcium Silicate Hydrate ◽  
Cement Hydration ◽  
Cementitious Materials ◽  
Pozzolanic Reaction ◽  
Indentation Modulus ◽  
Micromechanical Properties ◽  
Secondary Hydration

The indentation modulus of several cementitious materials is discussed with the assumption that the C-S-H gel is an aggregation of precipitated, colloidal-sized particles. At least two kinds of structurally distinct but compositional similar phases are found existent during the hydration process. In addition, the C-S-H originated from the pozzolanic reaction of fly ash is found to be the same to that of cement hydration in micromechanical properties; however, the C-S-H gel formed from the secondary hydration is inclined to develop into high density packing configuration, due to the limitation of reaction zone available.

scholarly journals Characterization of Early Pozzolanic Reaction of Calcium Hydroxide and Calcium Silicate Hydrate for Nanosilica Modified Cement Paste

2013 ◽  
Vol 4 (3) ◽  
pp. 6-10
Author(s):  
J.Z. Chong ◽  
N.M. Sutan ◽  
I. Yakub
Keyword(s):  
Calcium Hydroxide ◽  
Cement Paste ◽  
Calcium Silicate ◽  
Calcium Silicate Hydrate ◽  
Pozzolanic Reaction ◽  
Pozzolanic Reactivity ◽  
Characterization Technique ◽  
Binder Ratio ◽  
Ft Ir

This  study  intends  to  investigate  the  early   pozzolanic  reaction  of  Nanosilica (nS)         modified cement paste (NMCP)  by  the characterization technique  of Calcium Hydroxide (CH) and Calcium Silicate Hydrate (C-S-H ) using Fourier Transform Infrared Spectroscopy (FT-IR). NMCP samples were prepared with water-binder ratio of 0.50. nS of 5-15nm particle size were used as 1%, 3% ,5% ,7% and 10% replacement of cement by weight. All samples were cured in the concrete laboratory at daily room temperature (T) and relative humidity (RH) in the range of 18-28oC and 65-90%, respectively. Powdered samples were prepared and tested at day 1,7,21 and 28. It was found that characterization technique used were able to give satisfactory qualitative indication of pozzolanic reactivity of NMCP by the presence and absence of C-S-H and C-H that can indicate which replacement has higher pozzolanicity. NMCP exhibited a higher pozzolanic reactivity compare to conventional cement paste by which cement performance was enhanced.

Effect of Calcium Hydroxide Content on Pozzolanic Reaction of Calcined Clays: Their Mechanical Properties and Microstructures

2021 ◽  
Vol 1034 ◽  
pp. 161-168
Author(s):  
Supaluk Suttikul ◽  
Kanyarat Ano ◽  
Kedsarin Pimraksa
Keyword(s):  
Mechanical Properties ◽  
Calcium Hydroxide ◽  
Clay Minerals ◽  
Pozzolanic Reaction ◽  
Montmorillonite Clay ◽  
Strength Development ◽  
Calcined Clay ◽  
Pozzolanic Material ◽  
Phase Development ◽  
Calcium Aluminosilicate

The research aimed to investigate the effect of calcium hydroxide content on pozzolanic reaction of calcined clays. Pozzolanic reaction of calcined clay was determined in terms of its mechanical properties, phase development and microstructures. Three clay minerals (two kaolinitic clays and kaolinite-montmorillonite clay) were chosen to produce pozzolanic materials via calcination at temperature of 700 °C to allow dehydroxylation of clay minerals. Ratios of calcium hydroxide to calcined clays were varied from 0.1 to 0.5. Mixing water contents or liquid to solid ratios (0.62, 0.75 and 0.80) and curing times (7 and 28 days) were also studied. It was found that calcium aluminosilicate hydrate (stratlingite) could be formed after pozzolanic reactions of all clay minerals. The development of stratlingite agreed with the strength development showing the highest compressive strength at 26 MPa (28 days) when kaolinite-montmorillonite clay was used as pozzolanic material and the ratio of calcium hydroxide to calcined clay was 0.5.

Hydration Products, Microstructure and Durability of Concrete with Metakaolin Addition

2016 ◽  
Vol 680 ◽  
pp. 420-428
Author(s):  
Qiu Li ◽  
Hai Ning Geng ◽  
Yun Huang ◽  
Zhong He Shui
Keyword(s):  
Diffusion Coefficient ◽  
Calcium Hydroxide ◽  
Calcium Silicate ◽  
Calcium Silicate Hydrate ◽  
Analytical Techniques ◽  
Pozzolanic Reaction ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Hydration Products ◽  
Durability Of Concrete

The durability, microstructure and hydration products of concrete containing 0-6wt% metakaolin (MK) were studied by analytical techniques. The hydration products were calcium hydroxide (CH), ettringite and calcium silicate hydrate gels in the control concrete, and additional monocarboaluminate and hemicarboaluminate were identified in concrete containing MK. CH content decreased by 28 days hydration in concrete containing MK, due to the pozzolanic reaction between MK and CH. Chloride diffusion coefficient decreased with the increase of MK content. By addition of 6wt% MK, chloride diffusion coefficient decreased by 60%.

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.

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