ABSTRACT:
To realize high-value synergistic
utilization of the three major solid wastes from thermal power generation (fly
ash-FA,
coal-fired slag-CS, desulfurization
gypsum-DG), a Box-Behnken response surface model was established with CS, DG,
and cement as factors and FA as the matrix. Unlike existing research focusing
on single or binary solid waste composites, this study systematically optimized
the synergistic blending ratios of the three wastes without additional
activation. The 7d/28d strength models showed significant statistical validity
(
R2 = 0.9918/0.9979,
p < 0.001). The optimal mix
ratio (CS 21.38%, DG 10.96%, cement 16.15%, FA 51.51%) achieved 7d strength of
13.60 MPa and 28d strength of 19.07 MPa, with a model deviation rate below 2%.
The statistical model results are deeply correlated with the mechanisms of
hydration and microstructural evolution: cement and DG drive early-stage
hydration reactions to form rapid-strength products, while CS continuously
generates hydration gel through slow pozzolanic reactions to develop late-stage
strength. XRD/SEM analysis confirmed significant formation of
calcium-aluminum-silicate hydrate (C-(A)-S-H), calcium hydroxide (CH), and ettringite (AFt), verifying full activation
of pozzolanic substances in FA and CS. This study innovatively overcomes
bottlenecks in the simultaneous high-value utilization of three thermal wastes,
providing a scientific pathway for optimizing cementitious materials from
multi-source solid wastes.
