Use of glass waste as an activator in the preparation of alkali-activated slag. Mechanical strength and paste characterisation

2014 ◽  
Vol 57 ◽  
pp. 95-104 ◽  
Author(s):  
F. Puertas ◽  
M. Torres-Carrasco
Materials ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 1789 ◽  
Author(s):  
Tai Thanh Tran ◽  
Hyuk Kang ◽  
Hyug-Moon Kwon

The aim of this work was to study the mechanical strength and microstructure changes of alkali-activated slag mortar (AAS mortar) after being heat treated in the temperature range of 200–1000 °C. The AAS mortar was cured in the ambient condition (20 ± 5 °C, 60 ± 5% RH) (Relative humidity: RH) and high temperature condition (80 °C) for 27 days with three different heating regimes: curing in a dry oven, curing in sealed plastic bags, and in a steam environment. The activator for the AAS synthesis was a mixture of sodium silicate solution (water glass) and sodium hydroxide (NaOH) with a SiO2/Na2O weight ratio of 1, and a dosage of 4% Na2O by slag weight. Thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) incorporated with energy-dispersive X-ray spectroscopy (EDX) were used to assess the mortar microstructure change. The results revealed that the curing method significantly affected the mechanical strength of AAS at temperatures lower than 800 °C. The heat treatment at late age of 28 days was more beneficial for compressive strength enhancement in specimens without using heat curing methods.


2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Zikai Xu ◽  
Jinchao Yue ◽  
Guanhong Pang ◽  
Ruixia Li ◽  
Peng Zhang ◽  
...  

Geopolymers have distinct advantages such as having energy-saving properties, being an environmentally protective material, and having high mechanical strength and durability. However, the shrinkage of the geopolymer materials is one of the major problems to affect its practical application. In this study, blast furnace slag-based geopolymer pastes were prepared using sodium silicate and sodium hydroxide as activators to investigate the effect of the activator concentration and solid/liquid ratio on strength and shrinkage properties. For a better understanding of the reaction mechanism and microstructure of the geopolymer pastes, a multitechnique approach including scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectra was carried out. The results showed that the geopolymers compressive strength increased significantly as the activator concentration increased. The increase in activator concentration first increased the flexural strength and then decreased and reached the maximum when the activator concentration was 40%. A higher activator concentration, as well as a lower solid/liquid ratio, generally led to serious geopolymers drying shrinkage. These findings are expected to be ascribed from the changes in the content of the alkali-activated product (i.e., hydrate calcium aluminosilicate), which depends on the activator concentration. The increase in C-A-S-H gel (hydrate calcium aluminosilicate) compacts paste densifiers but causes shrinkage fracture concerns. These results provide an appropriate proportion for alkali-activated slag geopolymer pastes with better mechanical strength and antidry-shrinkage cracking properties, which are beneficial for the further applications of geopolymer materials.


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