TY - JOUR
T1 - Combined effects of vertical spacers and segregation on mass transport properties of reinforced concrete
AU - Muslim, F.
AU - Wong, H. S.
AU - Cheng, G.
AU - Alexandrou, C.
AU - Liu, B.
AU - Buenfeld, N. R.
N1 - Funding Information:
F. Muslim gratefully acknowledges the Indonesian Endowment for Education (LPDP) for funding her PhD at Imperial College London. We thank Mr. Andrew Morris, Dr Marcus Yio and Ms. Marwa El-Fassi for their assistance with the laboratory work. The research leading to this publication benefitted from EPSRC funding under grant No. EP/R010161/1 and from support from the UKCRIC Coordination Node, EPSRC grant number EP/R017727/1, which funds UKCRIC’s ongoing coordination.
Publisher Copyright:
© 2020, The Author(s).
PY - 2020/12
Y1 - 2020/12
N2 - All concrete structures contain reinforcement spacers, and deep sections can be affected by bleeding and segregation without displaying visible indications during casting. However, their effects on mass transport and long-term durability are not well studied. In this paper, reinforced concrete columns were prepared with plastic and cementitious spacers to achieve 50 mm cover, and compacted at different vibration frequencies and durations. 28d cured samples were extracted along the height, conditioned to equilibrium (21 °C, 75% RH or 50 °C, 7% RH), and then subjected to water absorption, electrical conduction, epoxy impregnation and fluorescence imaging. Samples from the top of the column consistently gave higher accessible porosity and mass transport compared to samples from the bottom. Presence of spacers caused additional increases in mass transport because of preferential flow through the spacer-concrete interface which is more porous and microcracked compared to bulk concrete farther away. Image analysis on cross-sections showed that the columns experienced some aggregate segregation despite care taken to avoid over-compaction. The resistance of concrete to ingress of aggressive agents decreases with increasing height due to the combined negative effects of reinforcement spacers and segregation.
AB - All concrete structures contain reinforcement spacers, and deep sections can be affected by bleeding and segregation without displaying visible indications during casting. However, their effects on mass transport and long-term durability are not well studied. In this paper, reinforced concrete columns were prepared with plastic and cementitious spacers to achieve 50 mm cover, and compacted at different vibration frequencies and durations. 28d cured samples were extracted along the height, conditioned to equilibrium (21 °C, 75% RH or 50 °C, 7% RH), and then subjected to water absorption, electrical conduction, epoxy impregnation and fluorescence imaging. Samples from the top of the column consistently gave higher accessible porosity and mass transport compared to samples from the bottom. Presence of spacers caused additional increases in mass transport because of preferential flow through the spacer-concrete interface which is more porous and microcracked compared to bulk concrete farther away. Image analysis on cross-sections showed that the columns experienced some aggregate segregation despite care taken to avoid over-compaction. The resistance of concrete to ingress of aggressive agents decreases with increasing height due to the combined negative effects of reinforcement spacers and segregation.
KW - Bleeding
KW - Durability
KW - Reinforcement spacer
KW - Segregation
KW - Spacer-concrete interface
KW - Transport properties
UR - http://www.scopus.com/inward/record.url?scp=85097317127&partnerID=8YFLogxK
U2 - 10.1617/s11527-020-01591-9
DO - 10.1617/s11527-020-01591-9
M3 - Article
AN - SCOPUS:85097317127
SN - 1359-5997
VL - 53
JO - Materials and Structures/Materiaux et Constructions
JF - Materials and Structures/Materiaux et Constructions
IS - 6
M1 - 151
ER -