# Use of pumice stone and silica fume as precursor material for the design of a geopolymer

## TL;DR

This study explores using pumice stone and silica fume to create a geopolymer with improved mechanical properties.

## Contribution

The study introduces an optimal 10% silica fume replacement to enhance geopolymer strength.

## Key findings

- A 10% silica fume replacement achieved maximum compressive and flexural strengths of 14.10 MPa and 4.78 MPa.
- Geopolymer strength is influenced by factors like sodium silicate ratio, water content, and curing time.
- The geopolymer is suitable for non-structural applications but could be improved with finer pumice powder.

## Abstract

Geopolymers are alternative materials to cement because they require less energy in their production process; hence, they contribute to the reduction in CO
2 emissions. This study aims to evaluate the possibility of using industrial residues such as silica fume (SF) to improve the physical and mechanical properties of a pumice stone (PS)-based geopolymer.

Through an experimental methodology, the process starts with the extraction, grinding, and sieving of the raw material to carry out the physical and chemical characterization of the resulting material, followed by the dosage of the geopolymer mixture considering the factors that influence the resistance mechanical strength. Finally, the physical and mechanical properties of the geopolymer were characterized. This research was carried out in four stages: characterization of the pumice stone, design of the geopolymer through laboratory tests, application according to the dosage of the concrete, and analysis of the data through a multi-criteria analysis.

It was determined that the optimal percentage of SF replacement is 10%, which to improves the properties of the geopolymer allowing to reach a maximum resistance to compression and flexion of 14.10 MPa and 4.78 MPa respectively, showing that there is a direct relationship between the percentage of SF and the resistance.

Geopolymer preparation involves the use of PS powder with a composition rich in silicon and aluminum. The factors influencing strength include the ratio of sodium silicate to sodium hydroxide, water content, temperature, curing time, molarity of sodium hydroxide, and binder ratio. The results showed an increase in the compression and flexural strength with 10% SF replacement. The geopolymer’s maximum compressive strength indicates its non-structural use, but it can be improved by reducing the PS powder size.