CONCRETO & Construções | Ed. 93 | Jan – Mar • 2019 | 61
dubbed chemoresistivity). Concrete
developed at UBC has highly sensitive
responses to both stimuli.
In the past, attempts to en-
hance the electrical conductivity of
concrete have been limited to use
of conducting fibres (pitch or poly-
acrylonitrile-based carbon fibre,
for example). In the concrete de-
veloped at UBC, carbon fibres are
hybridized with multi-walled carbon
nano-tubes (MWCNT) that makes
the concrete extremely responsive
to stress and chemical changes. Im-
pedance Spectroscopy is then used
to separate the influences of various
stimuli. Comparisons with traditional
sensors indicate that the stress sen-
sitivity of the cementitious sensors
is two orders of magnitude greater.
There is unfortunately no traditional
chemical sensor available with which
to compare these.
The sensors developed can also
detect strength gain in concrete,
and can be used in precast plants
for arriving at decisions related to
form removal, transportation, cold
joints, etc.
In addition to sensing, numer-
ous novel applications for electri-
cally conductive concrete can be
envisaged; these include: electri-
cal grounding, lightning arresters,
self-heating bridge decks for de-
icing, electromagnetic interference
shielding and static-free computer
room floors.
4. CONCLUSIONS
Structural failures around the
world have indicated that our struc-
tures are deteriorating rapidly and
this has created a crisis of unprec-
edented proportions. Even a bigger
concern is that we have poor un-
derstanding of what condition our
structures are in, and where the crit-
ical locations of deterioration are. It
is imperative therefore that we install
sensors on both new and old struc-
tures so a real-time structural health
monitoring can be performed. Such
sensors can not only alert us of an
impending collapse and safe lives,
but can also provide very useful
data needed for decisions pertain-
ing to infrastructure management in-
cluding functional obsolesce, repair
and rehabilitation.
u
Figure 7
Smart concrete; Left: sensor in compression; Right: sensor in tension
u
Figure 8
Sensor interface from a smart concrete used as a sensor
