Lightweight geopolymer made of highly porous siliceous materials with various Na2O/Al2O3 and SiO2/Al2O3 ratios

Abstract The syntheses of lightweight geopolymeric materials from highly porous siliceous materials viz. diatomaceous earth (DE) and rice husk ash (RHA) with high starting SiO 2 /Al 2 O 3 ratios of 13.0–33.5 and Na 2 O/Al 2 O 3 ratios of 0.66–3.0 were studied. The effects of fineness and calcination temperature of DE, concentrations of NaOH and KOH, DE to RHA ratio; curing temperature and time on the mechanical properties and microstructures of the geopolymer pastes were investigated. The results indicated that the optimum calcination temperature of DE was 800 °C. Increasing fineness of DE and starting Na 2 O/Al 2 O 3 ratio resulted in an increase in compressive strength of geopolymer paste. Geopolymer pastes activated with NaOH gave higher compressive strengths than those with KOH. The optimum curing temperature and time were 75 °C and 5 days. The lightweight geopolymer material with mean bulk density of 0.88 g/cm 3 and compressive strength of 15 kg/cm 2 was obtained. Incorporation of 40% RHA to increase starting SiO 2 /Al 2 O 3 and Na 2 O/Al 2 O 3 ratios to 22.5 and 1.7 and enhanced the compressive strength of geopolymer paste to 24 kg/cm 2 with only a marginal increase of bulk density to 1.01 g/cm 3 . However, the geopolymer materials with high Na 2 O/Al 2 O 3 (>1.5) were not stable in water submersion.

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

[2]  M. Dietzel.  Dissolution of silicates and the stability of polysilicic acid , 2000 .

[3]  K. Rangsriwatananon,et al.  Synthesis of sodium zeolites from natural and modified diatomite , 2005 .

[4]  Catherine L. Nicholson,et al.  The composition range of aluminosilicate geopolymers , 2005 .

[5]  X. Querol,et al.  Environmental, physical and structural characterisation of geopolymer matrixes synthesised from coal (co-)combustion fly ashes. , 2008, Journal of hazardous materials.

[6]  Prinya Chindaprasirt,et al.  Sulfate resistance of blended cements containing fly ash and rice husk ash , 2007 .

[7]  T. Bakharev,et al.  Geopolymeric materials prepared using Class F fly ash and elevated temperature curing , 2005 .

[8]  J. Phair,et al.  Effect of the silicate activator pH on the microstructural characteristics of waste-based geopolymers , 2002 .

[9]  Brian C. Smith.  Infrared Spectral Interpretation: A Systematic Approach , 1998 .

[10]  Prinya Chindaprasirt,et al.  Lightweight bricks made of diatomaceous earth, lime and gypsum , 2009 .

[11]  J. Provis,et al.  Geopolymers for immobilization of Cr(6+), Cd(2+), and Pb(2+). , 2008, Journal of hazardous materials.

[12]  J. Deventer,et al.  The effects of inorganic salt contamination on the strength and durability of geopolymers , 2002 .

[13]  Lesile Glasser.  The chemistry of silica: By Ralph K. Iller. Pp. vii+ 866. Wiley, Chichester. 1979, £39.50 , 1980 .

[14]  K. Okada,et al.  Preparation and properties of potassium aluminosilicate prepared from the waste solution of selectively leached calcined kaolinite , 2002 .

[15]  J. Deventer,et al.  Understanding the relationship between geopolymer composition, microstructure and mechanical properties , 2005 .

[16]  Haihong Li,et al.  Synthesis and mechanical properties of metakaolinite-based geopolymer , 2005 .

[17]  J. Deventer,et al.  The geopolymerisation of alumino-silicate minerals , 2000 .

[18]  J. Phair,et al.  Characteristics of aluminosilicate hydrogels related to commercial “Geopolymers” , 2003 .

[19]  J. Deventer,et al.  Structural reorganisation of class F fly ash in alkaline silicate solutions , 2002 .