New Zealand Pumicite as a Precursor in Producing Alkaline Cement with Aluminate-Based Activators

Kalatehjari, Roohollah; Khaksar Najafi, Elmira; Asadi, Afshin; Brook, Martin

New Zealand Pumicite as a Precursor in Producing Alkaline Cement with Aluminate-Based Activators

Files

Journal article(13.94 MB)

Date

2024-12

Authors

Kalatehjari, Roohollah

Khaksar Najafi, Elmira

Asadi, Afshin

Brook, Martin

Item type

Journal Article

Publisher

Elsevier BV

Abstract

This study investigates the activation of New Zealand pumicite (pumice powder) using sodium aluminate (NaAlO₂) solution, both alone and in combination with 10 M KOH solution, at various weight ratios of 1, 3, and 5, to produce alkali-activated cement. Compressive strength tests and microstructural analyses were conducted to assess the effects of activator/precursor ratios, activator type, aging time, and curing temperature (65°C for 72 hours or room temperature). The internal porosity of the pumicite played a key role in aluminosilicate phase dissolution and mobility, resulting in similar compressive strengths across different ratios. NaAlO₂ alone achieved compressive strengths of 60 MPa and 67 MPa after 4 and 65 days, respectively, while the binary solutions showed reduced strength with increased aging. Room temperature curing required almost three times the aging period to match the 28-day compressive strengths achieved after curing at 65°C for 72 hours. Microstructural analyses revealed that NaAlO₂ solution adjusted the Si/Al ratio, forming high-Al and high-Si gels as well as zeolite-A, underscoring its benefits. This study demonstrates the potential of using locally sourced New Zealand pumicite as a precursor in alkali-activated cement, particularly in regions lacking traditional industrial by-products.