| dc.description.abstract | The transport and :!.on-exc.hange propert ies
of mortar (cement-sand) membranes have been
experimentally investigated by determining the
transferenc..e numb er s of sodium chloride (Na.C'l)
through such membranes. The transferenc.e
phenomena of sodium c.hloride was studied due to
the deleterious elfec.ts of c.hloride (CI-) ions
on imbedded steel 1n rejnforc.ed mortar/concrete
struc.tures exposed to m~rine environments.
This was done by setting up conc.entration
cells of the type
1 'mortar ' ,
Ag/AgCI NaCIC ) mb INaCIC- ) AgCI/Ag
aq,c1 me rane dq,C2
c1>c2' using diffe~~e.Rtmembrane thicknesses and
,.,.
concentrations "i and •.c,2. The measured emf of the
various cells with the corresponding equilib rium
chloride ion concentrations were used for the
computation of the transference numbers. Th8 pH
values of the solutions from both cell cornpa rt meu t s
were also measured until a constant value of about
12 was achieved.
The chloride ion constituent ~ransference
number was found to vary between 0.8028 and
0.8104' while that of the sodium ion constituent
(iv)
was found to vary between 0.1896 and 0.1972
for a fixed merrb r ane thic.kness (5mm) and a
concentration range of O.05M to O.5M.
The transference numbers were however
found to be' invariant with different rnembrarie
thicknesses (4mm, 5mm and Gmm) for a constant
set of external electrolyte concentration, and
we ref 0un d to bet C1- :=0 O. 806 an d t Na + = O. 19 3
(to 3 dec. placEs). The ion exchange capacity
of the mort ar merrbr arie s 1'1 as found to increase
with increasing rnembr an c thickness, as depieted
from the quantity 01 chloride ions retained in
- the mernbr ane matrix with increasing membrane
thickness. The investigation has shown that a
mort ar membrane can act as an an i.on exchange
-.....- -
.-
.,
mernbrane, and the experiment ally determined
transference nurrb eTS u s i.ng the mort ar membr ane s
were in very good agreement with the empirical
formula
E =
2 tN +
a
RT
F
used for the comput ation of trans ference nuirb ers. | en |
