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

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

New cements for the 21st century: The pursuit of an alternative to Portland cement

Geopolymerization is a developing field of research for utilizing solid waste and by-products. It provides a mature and cost-effective solution to many problems where hazardous residue has to be treated and stored under critical environmental conditions. Geopolymer involves the silicates and aluminates of by-products to undergo process of geopolymerization. It is environmentally friendly and need moderate energy to produce. This review presents the work carried out on the chemical reaction, the source materials, and the factor affecting geopolymerization. Literature demonstrates that certain mix compositions and reaction conditions such as Al2O3/SiO2, alkali concentration, curing temperature with curing time, water/solid ratio and pH significantly influences the formation and properties of a geopolymer. It is utilized to manufacture precast structures and non-structural elements, concrete pavements, concrete products and immobilization of toxic metal bearing waste that are resistant to heat and aggressive environment. Geopolymers gain 70% of the final strength in first 3–4 h of curing.

Mechanism of geopolymerization and factors influencing its development: a review

The coexistence of geopolymeric gel and calcium silicate hydrate at the early stage of alkaline activation

Alkali-activated fly ash/slag cements: Strength behaviour and hydration products

Alkaline activation of metakaolin and calcium hydroxide mixtures: influence of temperature, activator concentration and solids ratio

Reaction products formed during alkaline activation, with 8M NaOH solutions, of fly ashes have been characterized with 29Si and 27Al magic-angle spinning nuclear magnetic resonance (MASNMR) spectroscopy. In particular, the influence of curing conditions (time and temperature of reaction) has been analyzed. NMR results show the formation of amorphous tecto-silicates in which the amount of aluminum decreases in the two consecutive formed phases. The Si/Al ratio of zeolite precursor obtained at 85°C changes from 0.95 to 1.86 when curing time is increased from 5 h to 1 week. The evolution of the mechanical properties of prepared cements has also been discussed in terms of the phases formed and texture and morphology of samples.

Alkaline Activation of Fly Ashes: NMR Study of the Reaction Products

Calorimetric study of alkaline activation of calcium hydroxide–metakaolin solid mixtures

The alkali activation of metakaolin (MK) leads to the production of high-mechanical-performance network-structure materials. Adding calcium hydroxide (Ca(OH) 2 ) to the raw MK produces a somewhat different reaction: a network structure and C-S-H gel form. In the present study, MK and (MK + Ca(OH) 2 ) mixes were activated with 5M and 12M NaOH solutions and cured at 45°C. A 5M concentration, in the absence of Ca(OH) 2 , did not produce MK activation within the test time. An activator concentration of 12M resulted in complete activation and the formation of a network structure. When Ca(OH) 2 was present in the raw mix, a small amount of C-S-H gel formed.

Santiago Alonso

Papers

Alkali-activated fly ash/slag cements: Strength behaviour and hydration products

Alkaline activation of metakaolin and calcium hydroxide mixtures: influence of temperature, activator concentration and solids ratio

Alkaline Activation of Fly Ashes: NMR Study of the Reaction Products

Calorimetric study of alkaline activation of calcium hydroxide–metakaolin solid mixtures

Alkaline Activation of Metakaolin: Effect of Calcium Hydroxide in the Products of Reaction