Structural-grade concrete containing FBC and PCC residues. Part I: Non-cement concrete

Abstract

This research study aimed to evaluate the extent to which by-products of two distinct coal combustion technologies – pulverised coal combustion (PCC) fly ash and fluidised bed combustion ash (FBC spent bed) – can be used in the production of non-cement and partial-cement structural-grade concretes. The first part of this work focuses on fresh properties, strength and dimensional stability of non-cement concretes having various dosages of PCC fly ash as a binder and FBC spent bed as a primary fine aggregate. The test results revealed that non-cement concretes could produce adequate strength for structural applications, particularly for FBC spent bed to PCC fly ash ratio of 3/1 and up to 40% substitution of FBC spent bed by natural fine aggregate. While the performance of the non-cement concretes was acceptable under dry and sealed conditions, high dimensional instability was observed under soaked conditions due to high sulfate-induced expansion. The setting times of the non-cement concretes were extremely long, capable of limiting their applications. An extension of this study (presented as Part II of this study) included the use of Portland cement as a secondary binder in order to mitigate the concerns over extreme setting times and soaked expansions.