Effects of NaOH concentrations on physical and electrical properties of high calcium fly ash geopolymer paste

Abstract The effects of sodium hydroxide (NaOH) concentration on setting time, compressive strength and electrical properties at the frequencies of 100 Hz–10 MHz of high calcium fly ash geopolymer pastes were investigated. Five NaOH concentrations (8, 10, 12, 15 and 18 molar) were studied. The liquid to ash ratio of 0.4, sodium silicate to sodium hydroxide ratio of 0.67 and low temperature curing at 40 °C were selected in making geopolymer pastes. The results showed that NaOH concentration had significant influence on the physical and electrical properties of geopolymer paste. The pastes with high NaOH concentrations showed increased setting time and compressive strength due to a high degree of geopolymerization as a result of the increased leaching of silica and alumina from fly ash. The dielectric constant and conductivity increased with NaOH concentration while tan δ decreased due to an increase in geopolymerization. At the frequency of 103 Hz, the dielectric constants of all pastes were approximately 104 S/cm and decreased with increased frequency. The relaxation peaks of tan δ reduced with an increase in NaOH concentration and ranged between 2.5 and 4.5. The AC conductivity behavior followed the universal power law and the values were in the range of 3.7 × 10−3–1.5 × 10−2 at 105–106 Hz.

[1]  Chai Jaturapitakkul,et al.  NaOH-activated ground fly ash geopolymer cured at ambient temperature , 2011 .

[2]  W. McCarter,et al.  The complex impedance response of fly-ash cements revisited , 2004 .

[3]  Rubina Chaudhary,et al.  Mechanism of geopolymerization and factors influencing its development: a review , 2007 .

[4]  Prinya Chindaprasirt,et al.  Preparation of fly ash and rice husk ash geopolymer , 2009 .

[5]  Warren A. Dick,et al.  Compressive strength and microstructural characteristics of class C fly ash geopolymer , 2010 .

[6]  Ali Nazari,et al.  Prediction early age compressive strength of OPC-based geopolymers with different alkali activators and seashell powder by gene expression programming , 2013 .

[7]  V. Sirivivatnanon,et al.  Workability and strength of coarse high calcium fly ash geopolymer , 2007 .

[8]  Diptikanta Swain,et al.  Structure, ionic conduction and dielectric relaxation in a novel fast ion conductor, Na2Cd(SO4)2 , 2007 .

[9]  Prinya Chindaprasirt,et al.  Influence of NaOH solution on the synthesis of fly ash geopolymer , 2009 .

[10]  M. Ahmaruzzaman,et al.  A review on the utilization of fly ash , 2010 .

[11]  P. Chindaprasirt,et al.  Comparative study on the characteristics of fly ash and bottom ash geopolymers. , 2009, Waste management.

[12]  Lianyang Zhang,et al.  Production of geopolymeric binder from blended waste concrete powder and fly ash , 2012 .

[13]  Prinya Chindaprasirt,et al.  Utilization of blended fluidized bed combustion (FBC) ash and pulverized coal combustion (PCC) fly ash in geopolymer. , 2010, Waste management.

[14]  William John McCarter,et al.  CHARACTERIZATION AND MONITORING OF CEMENT-BASED SYSTEMS USING INTRINSIC ELECTRICAL PROPERTY MEASUREMENTS , 2003 .

[15]  Prinya Chindaprasirt,et al.  Electrical conductivity and dielectric property of fly ash geopolymer pastes , 2011 .

[16]  P. Chindaprasirt,et al.  Effect of SiO2 and Al2O3 on the setting and hardening of high calcium fly ash-based geopolymer systems , 2012, Journal of Materials Science.

[17]  A. Van Beek,et al.  Dielectric measurements to characterize the microstructural changes of young concrete , 1999 .

[18]  Hugo Marcelo Veit,et al.  The effects of Na2O/SiO2 molar ratio, curing temperature and age on compressive strength, morphology and microstructure of alkali-activated fly ash-based geopolymers , 2011 .

[19]  Ali Nazari,et al.  Production geopolymers by Portland cement: Designing the main parameters’ effects on compressive strength by Taguchi method , 2012 .

[20]  Kenneth J. D. MacKenzie,et al.  Thermal behaviour of inorganic geopolymers and composites derived from sodium polysialate , 2003 .

[21]  Ji Zhou,et al.  A novel aluminosilicate geopolymer material with low dielectric loss , 2011 .

[22]  Fernando Pacheco-Torgal,et al.  Alkali-activated binders: A review: Part 1. Historical background, terminology, reaction mechanisms and hydration products , 2008 .

[23]  S. Alonso,et al.  Calorimetric study of alkaline activation of calcium hydroxide–metakaolin solid mixtures , 2001 .

[24]  Shigemitsu Hatanaka,et al.  High-Strength Geopolymer Using Fine High-Calcium Fly Ash , 2011 .

[25]  M. Cyr,et al.  Properties of inorganic polymer (geopolymer) mortars made of glass cullet , 2012, Journal of Materials Science.

[26]  H. Kamarudin,et al.  Microstructure of different NaOH molarity of fly ash-based green polymeric cement , 2011 .

[27]  Warren A. Dick,et al.  Alkali-activated complex binders from class C fly ash and Ca-containing admixtures. , 2010, Journal of hazardous materials.

[28]  Ji Zhou,et al.  A study on electrical conductivity of chemosynthetic Al2O3–2SiO2 geoploymer materials , 2008 .

[29]  P. Chindaprasirt,et al.  Effect of chemical admixtures on properties of high-calcium fly ash geopolymer , 2011 .

[30]  J. Deventer,et al.  Geopolymer technology: the current state of the art , 2007 .

[31]  J.S.J. van Deventer,et al.  Effect of the Alkali Metal Activator on the Properties of Fly Ash-Based Geopolymers , 1999 .

[32]  Yu Zhou,et al.  Thermal evolution and crystallization kinetics of potassium-based geopolymer , 2011 .