# Comprehensive Study on Design Optimization and Retardation Mechanism of SS-GGBS-FA Ternary Geopolymer Mortar

## TL;DR

This study explores how to optimize the setting time of a geopolymer mortar made from industrial byproducts and how different mixing methods affect its properties.

## Contribution

The study introduces a novel pre-coating mixing method that significantly retards the setting of geopolymer mortar using BaCl2.

## Key findings

- Increasing steel slag content significantly shortens the setting time of the geopolymer mortar.
- The pre-coating mixing method (C) outperforms other methods in delaying the hydration process.
- BaCl2 forms a BaSiO3 coating on precursor particles, which retards hydration.

## Abstract

A ternary geopolymer mortar (TGM) was synthesized using steel slag (SS), granulated blast furnace slag (GGBS), and fly ash (FA) as raw materials. The effect of the SS content (0–60%) and the GGBS/FA mass ratio (5:1 to 1:5) on the TGM’s setting time was studied. To address the issue of rapid setting, the impact of different mixing methods ((A) dry mixing, (B) pre-dissolution, and (C) pre-coating) and dosages of BaCl2 on the setting and hardening properties of TGM was further explored. The hydration product evolution and microstructural characteristics were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectrometry (EDS), with an in-depth analysis of the retarding mechanism of BaCl2. The results indicate that, as the steel slag content increases, the setting time of TGM significantly shortens. The setting time decreases slightly with an increase in the GGBS/FA mass ratio. The mixing method influences the retarding effect of BaCl2, with the C method showing significant advantages over both the A and B methods. Under the C mixing method, BaCl2 consumes the alkaline components (SiO32−) in the alkaline activator and forms a BaSiO3 coating layer on the precursor surface, which further delays the hydration process of the precursor particles. This study provides a promising approach for the high-value utilization of multi-source solid waste and suggests that future research should focus on large-scale application strategies and long-term performance evaluation to support its practical use in sustainable construction.