Self-sensing concrete with nanomaterials - Nanotechnology in Eco-efficient Construction - page 52

4
Self-sensing concrete with nanomaterials

Z. CHEN and Y. DING, Dalian University of Technology,
China, F. PA CHECO-TORGAL and Y. ZHANG
University of Minho, Portugal

DOI : 10.1533/9780857098832.1.53

Abstract : Conductive concrete containing nano carbon black (NCB) and
carbon fi bre (CF) to enable the self-diagnosis of strain and damage was
studied. The effect of NCB and CF on workability, mechanical properties
and fractional change in resistance (FCR) in fresh and hardened
concrete was analysed. The relationship between the FCR, the strain of
initial geometrical neutral axis (IGNA) and the degree of beam damage
was established. The results showed that the relationship between the
FCR and the IGNA strain can be described by the First Order
Exponential Decay function, and that the slope of this function refl ects
the sensitivity of conductive concrete. Based on the above relationship
and damage mechanics theory, internal damage to the concrete is
indicated by the relationship between the degree of damage and
resistance. This self-sensing of strain in conductive concrete can be
applied in monitoring damage to fl exible components.

Key words : conductive concrete, nano carbon black, carbon fi bre,
self-diagnosing of damage, fractional change in resistance, strain.

4.1 Introduction

Degradation, cumulative structural damage or material resistance are
common reasons for the failure of conventional concrete structures such as
dams and bridges which undergo differing levels of load, fatigue or corro-
sion. In order to prevent the possibility of sudden failure and to prolong
the service life of concrete structures, the study of cumulative damage has
concentrated on strain behaviour and fatigue process (Li and Ou, 2007; Ou,
1996). Monitoring is valuable for structural safety and the application of
conductive cementitious composite materials was reported by Wen and
Chung (2000, 2004, 2005, 2006, 2007), using electric resistance measurement
to monitor strain and damage.
Over the last decade, nanomaterials have been used as smart fi llers for a
broad range of multifunctional composites as well as in strain or damage
sensors (Li et al. , 2008; Chung, 2012). This chapter considers the addition of
both nano carbon black (NCB) and carbon fi bre (CF) as conductive phases
which enhance electrical conductivity and produce diphasic electric conduc-

￿ ￿ ￿ ￿ ￿ ￿

53