The stabilization of soft Bangkok clay by the mixture
of CCR and BA increases the unconfined compressive
strength and improves the microstructure due to the
pozzolanic reaction. The strength development depends
on certain key factors: CCR:BA ratio, soil water
content, binder content, and curing times. This study
leads to the following conclusions: (1) The initial soil
water content of 1.2 OWC is the most appropriate
mixing state for the initiation of physical and chemical
processes. The CCR:BA ratio of 60:40 is the
most suitable proportion in achieving the maximum
strength of stabilized clay. (2) The strength development
in the stabilized clay is classified into two
zones: active (B = 5–15%) and inert (B > 15%). The
15% binder is the appropriate quantity or the practical
amount for the stabilization of Bangkok clay. In the
active zone, the input BA increases the SiO2
content
and induces the strength development. The high CCR
content in the inert zone causes unsoundness due to
free lime, hence insignificant strength development.
(3) Ettringite and gismondine are the main products
found in stabilized clay with the blend of CCR and
BA at room temperature. Gismondine is responsible
for the long term strength gain. The hydrolysis of
CCR with water causes the very high pH solution
and then rapid dissolution of amorphous Si and Al
as well. Amorphous Si from BA is the reactant in
pozzolanic reaction because of its high reactivity in
base solution comparing the other Si oxides in clay.
(4) The denser clay structure is observed for higher
binder content due to the growth of the cementitious
products from pozzolanic reaction. Over the curing
times, the silica from the BA and clay is gradually
dissolved and reacted with the CCR to form supplementary
cementitious products (C-A-S-H), leading to
the subsequent filling of pore space and the higher
strength.