# A Study on the Pre-Hardened Shrinkage Reduction of Grout Using Carbon Materials

## TL;DR

This study explores using charcoal as an expansive agent in grout to reduce pre-hardening shrinkage, finding it more effective than traditional agents but with trade-offs in strength.

## Contribution

The study introduces charcoal as a novel expansive agent for grout, comparing its performance to conventional CSA.

## Key findings

- Charcoal increased pre-hardening expansion more effectively than CSA.
- Higher charcoal content reduced compressive strength after hardening.
- Different charcoals showed varying shrinkage/expansion rates, suggesting pore structure impacts performance.

## Abstract

In this study, the characteristics of grout mixed with charcoal as an expansive agent were examined to reduce the pre-hardening shrinkage of cementitious materials. This study compared and reviewed the application of CSA, a conventional expansive agent, to grout. The setting time, fluidity, compressive strength, and pre-hardening shrinkage/expansion were evaluated to explore the usability of charcoal as an expansive agent. The test results confirmed that, as the incorporation rate of charcoal increased, the pre-hardening expansion rate of the grout also increased, making it more effective for pre-hardening expansion than the conventional expansive agent CSA. However, when charcoal was used as an expansive agent, the compressive strength decreased after hardening, indicating the need for caution regarding the amount of charcoal used. Furthermore, the pre-hardening shrinkage and expansion rates of the various types of charcoal used in this study showed some differences, suggesting the need for further research on the internal pore volume and pore size of the charcoal.