The effect of efflorescense in geopolymer concrete is unavoidable due to the presence of alkali content. When exposed to water, it exhibits efflorescense in GPC. Will it affects the strength of the concrete?
Yes,
The effect of efflorescence will definitely affect the performance and strength of Geopolymer.
Efflorescence will lead to the formation of carbonic acid ,it is formed when atmospheric carbon dioxide enters into the concrete through fine pores and react with free water.
A small quantity of efflorescence on the surface of the sample or structure is not a threat to its durability and strength. However, when a higher quantity is formed due to certain types of activators used or curing condition employed, the integrity of the concrete might be breached. A higher quantity of efflorescence on the surface of the concrete might impair the appearance, increase permeability thereby reducing its durability.
Generally, the presence of efflorescence on a concrete surface is a sign of moisture penetration/leakage from the concrete. In the case of geopolymers, in the absence of Ca-based salt, it could be a sign showing that a high concentration of activator have been used to activate the Si-Al bearing precursors. Very high concentration of alkali activators usually affects the strength and durability of geopolymers.
The efflorescence is often happens in geoplymer concrete when higher concentrations of alkali solutions are taken as referred by @Dr. Hassan, we have also noticed this many time during our experimentation. The high efflorescence of GPC may cause strength reductions and concerns regarding durability aspects ( due to increased porosity).
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