A brief history and review of geopolymer technology is presented with the aim of introducing the technology and the vast categories of materials that may be synthesized by alkali-activation of aluminosilicates. The fundamental chemical and structural characteristics of geopolymers derived from metakaolin, fly ash and slag are explored in terms of the effects of raw material selection on the properties of geopolymer composites. It is shown that the raw materials and processing conditions are critical in determining the setting behavior, workability and chemical and physical properties of geopolymeric products. The structural and chemical characteristics that are common to all geopolymeric materials are presented, as well as those that are determined by the specific interactions occurring in different systems, providing the ability for tailored design of geopolymers to specific applications in terms of both technical and commercial requirements.

Geopolymer technology: the current state of the art

Carbon nanotube–polymer composites: Chemistry, processing, mechanical and electrical properties

http://p30p30-cement.persiangig.com/cement/Industrially%20interesting%20approaches%20to%20%e2%80%98%e2%80%98low-CO2%e2%80%99%e2%80%99%20cements.pdf

Industrially interesting approaches to “low-CO2” cements ☆

Polymer nanocomposites based on functionalized carbon nanotubes

The Role of Inorganic Polymer Technology in the Development of ‘Green Concrete’

The reaction below 100 °C of a dehydroxylated clay (metakaolinite: (Al2O3)(SiO2)2(H2O)005) suspended in an alkaline sodium silicate solution ((Na2O)(SiO2)14(H2O)x) leads to an amorphous glassy aluminosilicate, called in this work “low-temperature inorganic polymer glass” (LTIPG or IPG)

Low-temperature synthesized aluminosilicate glasses

The low-temperature reaction between an aqueous sodium or potassium silicate solution and metakaolinite yields a solid aluminosilicate. The influence of the molar ratios H2O/R2O (between 6.6 and 21.0) and SiO2/R2O (between 0.0 and 2.3) of the silicate solution (R=Na or K) on the aluminosilicate's production, on the reaction stoichiometry and on the aluminosilicate's molecular structure is studied with differential scanning calorimetry, 27Al and 29Si magic angle spinning nuclear magnetic resonance (MAS NMR), cross-polarization MAS NMR, Fourier transform infrared spectroscopy and X-ray diffractometry. The reaction stoichiometry is determined by a one to one ratio for R/Al. H2O/R2O has no influence on the molecular structure of the aluminosilicate. Aluminium in the aluminosilicate is four-fold coordinated for the whole range of silicate solutions investigated. Moreover, Si and Al are homogeneously distributed and the ratio Al/Si in the aluminosilicate is the same as in the reaction mixture if the stoichiometric one-to-one ratio for R/Al is used. If SiO2/R2O in the Na-silicate solution is equal to or higher than 0.8, the low-temperature reaction yields an amorphous aluminosilicate or “inorganic polymer glass”. For smaller values of SiO2/R2O the Na-aluminosilicates are partially crystalline. Thermomechanical analysis and dynamic mechanical analysis indicate that a variation in the composition of the amorphous aluminosilicates can shift the glass transition over a few hundreds of degrees, with a minimum value of 650°C.

Low-temperature synthesized aluminosilicate glasses. Part III Influence of the composition of the silicate solution on production, structure and properties

The reaction kinetics and mechanism of geopolymers are studied. The dissolved silicate concentration decreases from the beginning of the reaction. A characteristic time ‘t
 0,vit’ for the setting of the reaction mixture is derived from isothermal Dynamic Mechanical Analysis experiments. ‘t
 0,vit’ increases with SiO2/R2O but goes through a minimum for increasing water content. The reaction is slower for K compared to Na-silicate based systems. 29Si and 27Al solution NMR are used to probe the molecular changes. 27Al NMR and FTIR reveal that an ‘intermediate aluminosilicate species’ (IAS) is formed from the start of the reaction. The concentration decrease of OH− during low-temperature reaction is related to the formation of IAS. The rate law of this process seems to be obeyed by a total reaction order of 5/3, with a partial order of 1 for OH− and 0 for Na+ in the silicate solution. During first heating after polymerization water is lost leading to a distortion of the Al environment. According to XRD, no crystallization occurs below 900 °C. However, between 950 and 1100 °C a crystallization exotherm of nepheline is observed with DSC for a geopolymer with SiO2/Na2O = 1.4. Neither T
 g of the amorphous geopolymer, nor the shrinkage and expansion around T
 g during first heating, cause a measurable heat effect.

B. Van Mele

Papers

Low-temperature synthesized aluminosilicate glasses

Low-temperature synthesized aluminosilicate glasses. Part III Influence of the composition of the silicate solution on production, structure and properties

Reaction mechanism, kinetics and high temperature transformations of geopolymers

The Claims Demonstrated

Modulated differential scanning calorimetry: isothermal cure and vitrification of thermosetting systems