Lightweight concretes of activated metakaolin-fly ash binders, with blast furnace slag aggregates

Abstract This work investigated geopolymeric lightweight concretes based on binders composed of metakaolin with 0% and 25% fly ash, activated with 15.2% of Na2O using sodium silicate of modulus SiO2/Na2O = 1.2. Concretes of densities of 1200, 900 and 600 kg/m3 were obtained by aeration by adding aluminium powder, in some formulations lightweight aggregate of blast furnace slag was added at a ratio binder:aggregate 1:1; curing was carried out at 20 and 75 °C. The compressive and flexural strength development was monitored for up to 180 days. The strength diminished with the reduction of the density and high temperature curing accelerated strength development. The use of the slag had a positive effect on strength for 1200 kg/m3 concretes; reducing the amount of binder used. The thermal conductivity diminished from 1.65 to 0.47 W/mK for densities from 1800 to 600 kg/m3. The microstructures revealed dense cementitious matrices conformed of reaction products and unreacted metakaolin and fly ash. Energy dispersive spectroscopy and X-ray diffraction showed the formation of amorphous silicoaluminate reaction products.

[1]  K. Ganesh Babu,et al.  BEHAVIOUR OF LIGHTWEIGHT EXPANDED POLYSTYRENE CONCRETE CONTAINING SILICA FUME , 2003 .

[2]  V. Sirivivatnanon,et al.  Kinetics of geopolymerization: Role of Al2O3 and SiO2 , 2007 .

[3]  Grant C. Lukey,et al.  Thermal Conductivity of Metakaolin Geopolymers Used as a First Approximation for Determining Gel Interconnectivity , 2006 .

[4]  P. L. Pratt,et al.  Factors affecting the strength of alkali-activated slag , 1994 .

[5]  K. Sagoe-Crentsil,et al.  Dissolution processes, hydrolysis and condensation reactions during geopolymer synthesis: Part I—Low Si/Al ratio systems , 2007 .

[6]  J. Deventer,et al.  Microstructural characterisation of geopolymers synthesised from kaolinite/stilbite mixtures using XRD, MAS-NMR, SEM/EDX, TEM/EDX, and HREM , 2002 .

[7]  Laurence O. Williams.  An end to global warming , 2002 .

[8]  J. Davidovits.  Geopolymers and geopolymeric materials , 1989 .

[9]  Subaer,et al.  Thermo-mechanical and microstructural characterisation of sodium-poly(sialate-siloxo) (Na-PSS) geopolymers , 2007 .

[10]  Dali Bondar,et al.  Alkali-activation of natural pozzolan for geopolymer cement production , 2007 .

[11]  M. W. Grutzeck,et al.  Cement-based materials: Present, future, and environmental aspects; Ceramic transactions: Volume 37 , 1993 .

[12]  T. Bakharev,et al.  Resistance of geopolymer materials to acid attack , 2005 .

[13]  A. Neville.  Properties of Concrete , 1968 .

[14]  C. Kaps,et al.  Alkali-activated metakaolin-slag blends—performance and structure in dependence of their composition , 2007 .

[15]  Brian H. O'Connor,et al.  Chemical optimisation of the compressive strength of aluminosilicate geopolymers synthesised by sodium silicate activation of metakaolinite , 2003 .

[16]  J. I. Escalante-García,et al.  Statistical Analysis of Strength Development as a Function of Various Parameters on Activated Metakaolin/Slag Cements , 2010 .

[17]  I. Odler.  Special Inorganic Cements , 2000 .

[18]  J.S.J. van Deventer,et al.  THE EFFECT OF COMPOSITION AND TEMPERATURE ON THE PROPERTIES OF FLY ASH- AND KAOLINITE -BASED GEOPOLYMERS , 2002 .

[19]  J. I. Escalante García,et al.  Cementitious composites of pulverised fuel ash and blast furnace slag activated by sodium silicate: effect of Na2O concentration and modulus , 2006 .

[20]  J. Vlček,et al.  Properties of lightweight materials on the base of blast furnace slag evaluation , 2008 .

[21]  T. Cheng,et al.  Fire-resistant geopolymer produced by granulated blast furnace slag , 2003 .

[22]  T. Bakharev,et al.  Durability of Geopolymer Materials in Sodium and Magnesium Sulfate Solutions , 2005 .

[23]  Ramazan Demirboga,et al.  Effects of expanded perlite aggregate and mineral admixtures on the compressive strength of low-density concretes , 2001 .

[24]  C. Shi,et al.  Alkali-Activated Cements and Concretes , 2003 .

[25]  C. Vargel,et al.  The corrosion of aluminium , 2004, Corrosion of Aluminium.

[26]  Keun-Hyeok Yang,et al.  Properties of alkali-activated mortar and concrete using lightweight aggregates , 2010 .

[27]  J. Deventer,et al.  The coexistence of geopolymeric gel and calcium silicate hydrate at the early stage of alkaline activation , 2005 .

[28]  Jianzhong Xu,et al.  Study on the factors of affecting the immobilization of heavy metals in fly ash-based geopolymers , 2006 .

[29]  Jay G. Sanjayan,et al.  Damage behavior of geopolymer composites exposed to elevated temperatures , 2008 .

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

[31]  J. I. Escalante-García,et al.  Hydration Products and Reactivity of Blast‐Furnace Slag Activated by Various Alkalis , 2003 .

[32]  John L. Provis,et al.  Microscopy and microanalysis of inorganic polymer cements. 2: the gel binder , 2009, Journal of Materials Science.