Geopolymer Recycled Aggregate Concrete: From Experiments to Empirical Models

Area of Science:

• Materials Science
• Civil Engineering
• Sustainable Construction

Background:

• Ordinary concrete production has significant CO2 emissions and consumes natural resources.
• Sustainable development and circular economy principles drive the search for eco-friendly construction materials.
• Recycled aggregates and alternative binders are key challenges for the construction sector.

Purpose of the Study:

• To investigate the potential of non-conventional concrete using recycled aggregates and an alkali-activated binder.
• To evaluate the influence of mix design parameters and curing conditions on geopolymer recycled aggregate concrete (GRAC).
• To assess the applicability of modified empirical models for predicting GRAC compressive strength.

Main Methods:

• Specimens prepared using low calcium fly ash, sodium silicate, sodium hydroxide, river sand, and recycled coarse aggregate.
• Investigated factors include alkali-activated solution (AAS) to fly ash ratio, curing temperature, and superplasticizer content.
• Microscopic analyses evaluated the interfacial transition zone; modified Feret's and De Larrard's models were used for strength prediction.

Main Results:

• Geopolymer recycled aggregate concrete (GRAC) exhibited positive performance characteristics.
• Microscopic analyses provided insights into the interfacial transition zone of GRAC.
• Modified empirical models showed relevancy in predicting the compressive strength of GRAC.

Conclusions:

• GRAC is a viable and sustainable alternative to ordinary concrete.
• The study validates the use of recycled aggregates and alkali-activated binders in concrete.
• The proposed models offer a reliable method for predicting GRAC compressive strength.