Citation: Jannat, T.; Huang, Y.; Zhou,
Z.; Zhang, D. Influences of CNT
Dispersion Methods, W/C Ratios,
and Concrete Constituents on
Piezoelectric Properties of
CNT-Modified Smart Cementitious
Materials. Sensors 2023, 23, 2602.
https://doi.org/10.3390/s23052602
Academic Editors: Ki-Hyun Kim
and Deepak Kukkar
Received: 24 January 2023
Revised: 22 February 2023
Accepted: 23 February 2023
Published: 27 February 2023
Copyright: © 2023 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
Article
Influences of CNT Dispersion Methods, W/C Ratios, and
Concrete Constituents on Piezoelectric Properties of
CNT-Modified Smart Cementitious Materials
Tofatun Jannat
1
, Ying Huang
1
, Zhi Zhou
2
and Dawei Zhang
1,
*
1
Department of Civil, Construction and Environmental Engineering, North Dakota State University,
Fargo, ND 58105, USA
2
School of Civil Engineering and Architecture, Hainan University, Haikou 570228, China
* Correspondence: dawei.zhang.1@ndsu.edu; Tel.: +701-799-8358
Abstract:
In order to achieve effective monitoring of concrete structures for sound structural health,
the addition of carbon nanotubes (CNTs) into cementitious materials offers a promising solution
for fabricating CNT-modified smart concrete with self-sensing ability. This study investigated the
influences of CNT dispersion method, water/cement (W/C) ratio, and concrete constituents on the
piezoelectric properties of CNT-modified cementitious materials. Three CNT dispersion methods
(direct mixing, sodium dodecyl benzenesulfonate (NaDDBS) and carboxymethyl cellulose (CMC)
surface treatment), three W/C ratios (0.4, 0.5, and 0.6), and three concrete constituent compositions
(pure cement, cement/sand, and cement/sand/coarse aggregate) were considered. The experimental
results showed that CNT-modified cementitious materials with CMC surface treatment had valid
and consistent piezoelectric responses to external loading. The piezoelectric sensitivity improved
significantly with increased W/C ratio and reduced progressively with the addition of sand and
coarse aggregates.
Keywords:
smart concrete; piezoelectricity; carbon nanotubes; dispersion method; water-cement
ratio; concrete constituent
1. Introduction
As the most widely used construction material, concrete has taken our civilization
forwards for centuries. However, concrete structures may be subjected to various environ-
mental threats including erosion, impact forces, and harsh weather conditions. Excessive
exposure to such adverse environmental conditions could induce cracking and delamina-
tion of concrete, leading to potential long-term safety concerns. Thus, close monitoring of
concrete structures in these environments is needed to prevent catastrophic failure [1,2].
The most popular methods to inspect of concrete damage and deformations include
visual inspection and the usage of attached or embedded sensors [
3
–
5
]. Although visual
inspection is a cost-effective inspection method, it represents a tremendous workload due
to the large size and complexity of most civil infrastructures. In addition, the results of
visual inspection are sometimes unreliable given that most instances of concrete damage
occur on the inaccessible parts of the structure [
2
,
6
,
7
]. For attached or embedded sensors,
there are several types of sensing technologies available to monitor the conditions of
concrete structures, such as resistance strain gauges, shape memory alloys, and fiber optical
grating sensors. However, the attached or embedded sensors also have limitations such
as challenges in compatibility with concrete and local measurements [
2
,
6
,
8
]. The needs
for structural health assessment of civil infrastructures have necessitated research on the
development of real-time and in situ monitoring techniques. Such techniques should allow
the system to monitor its structural integrity while the infrastructure is in service, and the
monitoring can be performed throughout the whole service life of the infrastructure.
Sensors 2023, 23, 2602. https://doi.org/10.3390/s23052602 https://www.mdpi.com/journal/sensors
