Effect of Fineness of Basaltic Volcanic Ash on Pozzolanic Reactivity, ASR Expansion and Drying Shrinkage of Blended Cement Mortars.

Kaffayatullah Khan,Muhammad Nasir Amin,Muhammad Ghulam Qadir,Majdi Adel Al-Faiad,Muhammad Umair Saleem,Hisham Jahangir Qureshi

doi:10.3390/ma12162603

Kaffayatullah Khan, Muhammad Nasir Amin + Show 4 more

Open Access

https://doi.org/10.3390/ma12162603

Copy DOI

Journal: Materials	Publication Date: Aug 15, 2019
Citations: 34	License type: CC BY 4.0

Affiliation: King Faisal University, COMSATS University Islamabad

Abstract

This study focuses on evaluating the effect of the fineness of basaltic volcanic ash (VA) on the engineering properties of cement pozzolan mixtures. In this study, VA of two different fineness, i.e., VA fine (VF) and VA ultra-fine (VUF) and commercially available fly ash (FA) was used to partially replace cement. Including a control and a hybrid mix (10% each of VUF and FA), eleven mortar mixes were prepared with various percentages of VA and FA (10%, 20% and 30%) to partially replace cement. First, material characterization was performed by using X-ray florescence (XRF), X-ray powder diffraction (XRD), particle size analysis, and a modified Chappelle test. Then, the compressive strength development, alkali silica reactivity (ASR), and drying shrinkage of all mortar mixes were investigated. Finally, XRD analysis on paste samples of all mixes was performed to assess their pozzolanic reactivity at ages of 7 and 91 days. The results showed increased Chappelle reactivity values with an increase in the fineness of the VA. Mortars containing high percentages of VUF (20% and 30%) showed almost equal compressive strength compared to corresponding FA mortars at all ages, however, the hybrid mix (10% VUF + 10% FA) exhibited higher strength than that of the reference mix (100% cement), particularly, at 91 days. At low percentages (10%), ASR expansion in both VF and VUF mortars was higher compared to the corresponding FA mortar and the opposite behavior was observed at high percentages (20% and 30%). Among all the mixes including the control, mortar with VUF was found to be most effective in controlling drying shrinkages at all ages. The rate of consumption of calcium hydroxide (Ca(OH)2) for pastes containing VUF and FA was almost the same, while VF showed low Ca(OH)2 intensity. These results indicate that an increase in the fineness of VA significantly improvs performance, and therefore, it could be a feasible substitute for commercial admixtures in cement composites.

Highlights

CO2 emissions have increased in the past two decades to such an extent that a sustainable environment for living species on earth has become endangered
The recent advancements in the cement manufacturing industry and increasing demand for concrete have enabled production units to produce high volumes of cement that pose a significant threat to greenhouse gases [4]
A comparison of the chemical composition of volcanic ash (VA) and Fly Ash (FA) is presented in Table 1, which shows the

Summary

Introduction

CO2 emissions have increased in the past two decades to such an extent that a sustainable environment for living species on earth has become endangered. Around 25 billion metric tons of concrete is produced every year, which includes 3.3 billion metric tons of Portland cement [1,2]. This high level of cement production has a massive impact on the green life cycle and the environment. The recent advancements in the cement manufacturing industry and increasing demand for concrete have enabled production units to produce high volumes of cement that pose a significant threat to greenhouse gases [4]. Higher rates of concrete production and consumption have encouraged worldwide research to study and understand the effect of cement manufacturing on the environment [5]

Methods

Results

Conclusion