Geopolymer concrete: A review of some recent developments

Effect of GGBFS on setting, workability and early strength properties of fly ash geopolymer concrete cured in ambient condition

Fly ash-based geopolymer: clean production, properties and applications

A new type of geopolymer composite was synthesized from two industrial wastes, red mud (RM) and rice husk ash (RHA), at varying mixing ratios of raw materials and the resulting products characterized by mechanical compression testing, X-ray diffraction, and scanning electron microscopy to assess their mechanical properties, microstructure, and geopolymerization reactions. Prolonged curing significantly increases the compressive strength and Young’s modulus, but reduces the ductility. Higher RHA/RM ratios generally lead to higher strength, stiffness, and ductility, but excessive RHA may cause the opposite effect. The compressive strength ranges from 3.2 to 20.5 MPa for the synthesized geopolymers with nominal Si/Al ratios of 1.68–3.35. Microstructural and compositional analyses showed that the final products are mainly composed of amorphous geopolymer binder with both inherited and neoformed crystalline phases as fillers, rendering the composites very complex composition and highly variable mechanical properties. Uncertainties in the composition, microstructure, the extent of RHA dissolution, and side reactions may be potential barriers for the practical application of the RM–RHA based geopolymers as a construction material.

Synthesis and characterization of red mud and rice husk ash-based geopolymer composites

In this study, geopolymer mortar was produced using Class F fly ash from the thermal power plant in Kutahya Seyitomer (Turkey). The changes caused by the geopolymerization on the properties of the final product were investigated by applying curing on geopolymer mortars in different NaOH concentrations at different temperatures and for different curing times. The purpose of this process was to determine the relationship between alkali solution concentration, curing temperature and curing time. In order to determine the effect of NaOH concentration on geopolymer mortars, three different molarities of NaOH concentrations (3 M, 6 M and 9 M) were used together with sodium silicate (water glass) solution. The samples were cured at two different temperatures (65 and 85 °C). Physical properties such as porosity, bulk density, apparent density and water absorption, and mechanical properties such as flexural strength and compressive strength were determined from the 7-day geopolymer mortar samples after the curing process. As a result, this study determined that curing temperature and curing time had an effect on the physical properties of the geopolymer mortars. It was observed that NaOH concentration had a clear effect on the properties of the mortar cured at 85 °C. Compressive strength values of 21.3 MPa and 22 MPa were obtained from the mortar of 6 M concentration cured at 65 °C for 24 h and from a sample of the same mortar cured at 85 °C, respectively. Compressive strength values of the geopolymer mortars cured at 85 °C increased depending on the curing time and the increase in NaOH concentration. Given the strength values obtained, the optimal thermal curing temperature and the optimal NaOH concentration were 85 °C and 6 M, respectively.

The influence of the NaOH solution on the properties of the fly ash-based geopolymer mortar cured at different temperatures

NaOH-activated ground fly ash geopolymer cured at ambient temperature

Microstructures of calcium carbide residue (CCR) and CCR–ground fly ash (CCR-GFA) pastes were examined. A ratio of CCR to GFA of 30 to 70 by weight was used as a binder without portland cement. CCR-GFA pastes with three different water-to-binder (W/B) ratios of 0.3, 0.4, and 0.5 were prepared. Scanning electron microscopy (SEM) was used to study the morphology of the CCR-GFA pastes. X-ray diffractometry (XRD) and Fourier transform infrared (FTIR) spectroscopy were used to provide fundamental information about the specimens. Microstructures of CCR-GFA pastes were studied at 60 days. The compressive strengths of CCR-GFA pastes were determined at 7, 14, 28, 42, and 60 days. The morphology of CCR-GFA paste was composed of gelatinous particles of different sizes. The fracture surface was inhomogeneous with rough textures. Calcium silicate hydrate (CSH) product as Ca5(SiO4)2(OH)2 was found in all CCR-GFA pastes. This new compound was also found by FTIR analysis at wavelengths of 435 and 970  cm-1. Results from ...

Kiatsuda Somna

Papers

NaOH-activated ground fly ash geopolymer cured at ambient temperature

Microstructure of Calcium Carbide Residue-Ground Fly Ash Paste

Rice Husk Ash and Fly Ash Geopolymer Hollow Block Based on NaOH Activated

Calcium carbide residue-ground fly ash mixture as a new material to encapsulate zinc