# Effects of Four Nanomaterials on the Performance and Microstructure of Coal Gangue-Based Geopolymers

## TL;DR

This study explores how adding four nanomaterials to coal gangue-based geopolymers affects their performance and structure, aiming to improve their use in construction.

## Contribution

The paper introduces the comparative effects of four specific nanomaterials on the properties of coal gangue-based geopolymers.

## Key findings

- Graphene oxide nanosheets significantly reduced the fluidity of the geopolymer slurry.
- Nano-SiO2 improved compressive strength and shortened setting time at an optimal dosage.
- Nano-CaCO3 reduced porosity and water absorption when added at an appropriate dosage.

## Abstract

This study aimed to enhance the slurry performance and durability of coal gangue-based geopolymers (CGGP) by incorporating four types of nanomaterials: nano-SiO2 (NS), graphene oxide (GO) nanosheets, nano-CaCo3 (NC), and nano-Al2O3 (NA). The microstructure and underlying mechanisms were thoroughly investigated using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The results indicate that the type and dosage of nanomaterials significantly influence the rheological properties, strength development, setting time, porosity, and water absorption of CGGP. Specifically, the addition of GO nanosheets drastically reduced fluidity, with a 73.33% decrease in flowability compared to the control group at a 2.0 wt.% dosage. Nano-SiO2 exhibited the most pronounced effect in improving compressive strength and shortening the setting time, with the optimal accelerating effect observed at a 1.5 wt.% dosage. Nano-CaCO3 primarily acts as a filler. Though its reactivity is relatively low, at an appropriate dosage (1.5 wt.%), it can effectively reduce porosity and water absorption. Moreover, at a dosage of 1 wt.%, it exhibits the optimal 28-day compressive strength, which is 54.18% higher than that of the blank group. Nano-Al2O3 demonstrated a relatively stable accelerating effect on setting and yielded the best pore structure and strength at a 1.5 wt.% dosage. SEM analysis revealed that the incorporation of an appropriate amount of NC particles significantly improved the microstructural densification of the polymer. Concurrently, EDS results confirmed the positive influence of the nano-Al2O3 material on the distribution of hydration products and the interfacial structure. This research provides an important theoretical basis and technical support for the high-performance design and widespread engineering application of coal gangue-based geopolymers.