Influence of the Composition of the Activator on Mechanical Characteristics of a Geopolymer

Abstract

Geopolymer materials are characterized by their high durability and low carbon dioxide emissions, when compared with more traditional materials, like concrete made from ordinary Portland cement. These are interesting advantages and might lead to a more sustainable construction industry. The aim of this study is the characterization of the mechanical behavior of the materials obtained by the activation of metakaolin. The activator is a mixture of sodium hydroxide with sodium silicate in different proportions. The influence of the composition of activator is studied. For the analysis of the mechanical properties of the different mixtures two different types of tests were performed, bending tensile strength tests and compressive strength tests. The results show that an activator with not less than 300 g of sodium hydroxide and not exceeding 600 g of sodium silicate per 750 g of metakaolin gives the best results, for both tensile strength and compressive strength.

Geopolymers as Alternative Sustainable Binders for Stabilisation of Clays—A Review

“…However, the alkaline solutions are the most common activators used in research. For example, sodium hydroxide (NaOH) or potassium hydroxide (KOH) as single activators [25] or in combination with sodium silicate (Na2SiO3) or potassium silicate (K2SiO3) to expedite the reaction rate [26,27] for the formation of strength-giving compounds such as sodium-aluminosilicate hydrate (N-A-…”

“…However, the alkaline solutions are the most common activators used in research. For example, sodium hydroxide (NaOH) or potassium hydroxide (KOH) as single activators [25] or in combination with sodium silicate (Na 2 SiO 3 ) or potassium silicate (K 2 SiO 3 ) to expedite the reaction rate [26,27] for the formation of strength-giving compounds such as sodium-aluminosilicate hydrate (N-A-S-H). The type and amount of activator or mixture of activators utilised for geopolymerisation with Al-Si resource influences the porosity and bond strength of the resulting geopolymer [28,29].…”

“…Upon increased temperatures say 80 • C, Na 2 SiO 3 may be utilised as a single activator without reduction in strength as the increased temperature aids the breakdown of the existing bonds within the starting material for the dissociation of Al-Si units [32]. Since the hydroxide and silicate combination of the activator both contribute to the quality of the resulting geopolymer, it is logical to conclude that there is an optimum ratio of NaOH to Na 2 SiO 3 for best performance [25]. Na 2 SiO 3 has the added advantage of compensating for shortage in silicon in the precursor leading to increase in bond strength with a reduction in porosity.…”

Experimental Study on the Flexural Behavior of Alkali Activated Fly Ash Mortar Beams

“…Fly ash is one of the materials that can be used in alkaline activated products. The authors have tested other materials [16], but the current document reports a study on the behavior of fly ash in structures, particularly in beams under bending. It is interesting, in particular, to evaluate the behavior of these beams under bending action, for different levels of the loading, and to compare it with that of beams built with traditional Portland cement.…”

The Effect of Polymer Waste Addition on the Compressive Strength and Water Absorption of Geopolymer Ceramics

“…Geopolymer alkali-activation of metakaolin studies has increased in recent decades. This is partly due to the lower CO 2 emission during geopolymerization processes compared to the use of Portland Cement [23,24]. Sodium hydroxide (NaOH) and potassium hydroxide (KOH) are alkali-activation solutions commonly used for geopolymerization processes at low temperatures [25][26][27][28].…”