Mechanical and Thermal Evaluation of Diatomite Doped Fly Ash Based Geopolymers

Abstract

In this work, the properties of alkali silicate geopolymer type materials and diatomite as additive to fly coal ash was investigated using thermic coal plant’s fly ash in alkaline solution. The reacted products of alumino-silicate geopolymers using fly ash plus diatomite were pseudo-amorphous aluminosilicate gel and calcite and their mechanical and thermal properties were evaluated by the addition of diatomite. The compressive strength of this geopolymer is similar to that of the Portland cement mortar of PC20 (± 20 %) when cured for 28 days while the density and thermal properties are much lower that indicates the insulator properties. Alkaline solution was produced by NaOH in different concentrations to determine the least alkaline solution molarity in the range of 1 M, 3 M and 5 M. The characterization of geopolymers were done by using XRD for phase analysis, SEM for surface and morphological evaluation, compression tests for mechanical properties and transient plane source thermal analysis for thermal insulation properties. The results showed that, 1 M of NaOH alkaline solution and 10wt% diatomite addition can provide enough strength of 18 MPa which is a good candidate for constructional materials. The thermal conductivity coefficient of 10 wt.% diatomite added geopolymer was evaluated as 0.0018 W/m×K which can also be a good candidate for insulator materials to be used in green lateral wall production.

The Influence of Diatomite Addition on the Properties of Geopolymers Based on Fly Ash and Metakaolin

“…The large amount of diatomite caused a higher reduction in compressive strength. A reduction in compressive strength as an effect of diatomite addition has been observed previously for geopolymers based on fly ash [12,16]. However, other investigation showed that diatomite addition increased mechanical properties [32].…”

“…been observed previously for geopolymers based on fly ash [12,16]. However, other investigation showed that diatomite addition increased mechanical properties [32].…”

“…The same aim, reducing alkaline solution consumption in geopolymers through diatomite addition, was the main motivation of the research provided by Şahbudak [16]. Their results show that geopolymers with a very small amount of sodium hydroxide (1M) supplemented with diatomite (10 wt.%) can be applied as construction materials with reasonable strength properties-18 MPa compressive strength [16]. Furthermore, some more recent research is focused on this topic.…”

Improving Sag Resistance in Geopolymer Coatings Using Diatomite Filler: Effects on Rheological Properties and Early Hydration

“…Due to the numerous internal pores in geopolymer coatings, diatomite can act as a fine aggregate filler [ 48 ]. Initially, due to its higher water absorption, an increase in diatomite concentration results in higher adsorption of free water, thereby slowing down the progress of geopolymer hydration reactions [ 84 ]. This delay resulted in the surface hardness of the geopolymer coatings with added diatomite being lower than that of the blank group.…”

The Impact and Mechanism Analysis of Diatomite on the Sag Resistance of Geopolymer Coatings

“…The bonding strength and surface hardness, crucial performance indicators for coatings, effectively reflect the protective effect of geopolymer coatings on concrete structures. The interfacial bonding between geopolymer coatings and concrete arises from physicochemical interactions at the contact surfaces between phases [43][44][45][46][47]. Figure 11a illustrates the bond strength of geopolymer coatings with varying diatomite concentrations at curing ages of 3 days, 7 days, and 28 days.…”