Feasibility of backfilling mines using cement kiln dust, fly ash, and cement blends

H Beltagui,S Taylor,K Maguire,M Sonebi

doi:10.1051/matecconf/201814901072

Abstract

Cement kiln dust (CKD) is an industrial by-product of the cement manufacturing process, the composition of which can vary widely. Recent years of using alternative fuels have resulted in higher chloride and alkali contents within CKDs; as such, this limits the applications in which CKDs can be utilised. Using a CKD containing a high free lime content of 29.5%, it is shown that this CKD is capable of activating pulverized fuel ash (PFA) due to its high alkalinity, which can be utilised in low strength un-reinforced applications. One potential application involves the backfill of mines, reducing the need for continuous maintenance of the mine. This study focuses on the compressive strength achieved by various blends of CKD, PFA, and cement. Samples were hand mixed and compacted in 100 mm x 50 mm diameter cylinders, and unconfined compressive strength measurements taken at 28 and 56 days. The hydration products were assessed through the use of x-ray diffraction and thermogravimetric analysis. Aiming to maximise the use of CKD at a water to binder (w/b) ratio of 0.2, it was found that the maximum CKD content possible to achieve the required strength was 90% CKD blended with 10% cement.

Highlights

Cement kiln dust (CKD) is an industrial by-product of the cement manufacturing process, the composition of which can vary widely
This study focuses on the compressive strength achieved by various blends of CKD, pulverised fly ash (PFA), and cement
The present study showed that CKD, containing high free-lime content, has the potential to activate the pozzolanic reaction of PFA and provide sufficient mechanical properties for low strength applications

Summary

Introduction

Cement kiln dust (CKD) is an industrial by-product of the cement manufacturing process, the composition of which can vary widely. A portion of the CKD produced can be returned to the cement production process. Recent years of using alternative fuels, such as solid recovered fuel (SRF), have resulted in higher chloride and alkali contents within CKDs. The high alkalinity of these CKDs can be exploited by blending with alkali activated materials, such as pulverised fly ash (PFA) or slags. Portland cement is blended to provide high early strength, while the alkali activation can improve the long term strength and durability of the concrete. It has previously been shown that additions of up to 10-15% CKD by weight to high volume fly ash and slag concretes can produce improved strengths to blends with no added CKD [1,2]

Methods

Results

Conclusion