Investigation of Strength and Microstructural Characteristics of Blended Cement-Admixed Clay with Bottom Ash

This research presents an experimental study of the strength and microstructural characteristics
of cement-bottom ash-admixed Bangkok clay, paying special attention to the efficiency of adding
up the bottom ash (BA) of different finesses as a cementitious material and the role played by BA in
enhancing the strength of the mixture. The obtained results were discussed with cemented clay mixed
with other industrial ashes (i.e., fly ash and risk husk ash). The pozzolanic reaction and packing effect
of BA on strength development were also discussed with tests of mixtures with insoluble material.
The experimental study was performed through unconfined compression (UC), thermogravimetric
analysis (TGA), and scanning electron microscopy (SEM) tests. The obtained results demonstrate that
the BA could be advantageously supplemented as cementitious material into the cement-admixed
clay mixture to improve the strength characteristic. The finer particle size of BA could be beneficial
for achieving a high strength due to the pozzolanic reaction and packing effects. By adding up a BA
content of larger than 15% when the base cement content is not less than 20%, the strength of the
mixture increased efficiently with the increasing BA content. Compared with fly ash of a similar grain
size, the higher efficiency of BA is obtained when a BA content of greater than 15% is considered.
Finally, the microstructure and changes in elemental composition/distribution were analyzed by
TGA and SEM tests to explain the mechanism to improve the strength of cement–BA-admixed clay.