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Crack repair by activation of the pozzolanic or slag reaction

Elke Gruyaert UGent, Kim Van Tittelboom UGent, H Rahier and Nele De Belie UGent (2012) Microstructural-related Durability of Cementitious Composites, RILEM Proceedings PRO 83. p.1-8
abstract
Nowadays, industrial by-products like fly-ash (FA) and blast-furnace slag (BFS) are commonly used as cement replacing material. In combination with ordinary Portland cement (OPC), the BFS reaction is activated by the presence of alkali hydroxides in the pore solution and the Ca(OH)2 released during the OPC hydration. However, former research has shown that the slag hydration degree significantly decreases in pastes containing very high amounts of slag (> 80%). Also for FA-OPC mixes with a high FA/OPC ratio (> 50%), the activation level of the pozzolanic reaction is strongly reduced. While FA and BFS concrete seem to be inferior with regard to the early age microstructure and strength development, their self-healing capability can be much higher, precisely because of the low hydration degree of the slag and fly-ash particles. Upon cracking, the unreacted particles can be activated again in order to close the crack and to regain water impermeability and strength. In this study, autogenous as well as autonomous healing of mixes containing BFS or FA was investigated. First of all, calorimetric measurements were performed in order to evaluate the renewed hydration reactions of crushed pastes (age ~ 1 - 2 months), which were brought into contact with water to simulate autogenous healing, or with different activators (NaOH, Na-silicate,…) to simulate autonomous healing by alkali activation. Secondly, cracks were created in mortar bars with different binder compositions at an age of 28 days. The specimens were then stored under water or in alkaline solutions and the extent to which cracks close was monitored by optical microscopy. The results clearly showed the self-healing capacities of BFS and FA mixes. Based on this study, the most appropriate activators for BFS and FA were chosen.
Please use this url to cite or link to this publication:
author
organization
year
type
conference
publication status
published
subject
in
Microstructural-related Durability of Cementitious Composites, RILEM Proceedings PRO 83
editor
Guang Ye UGent, Klaas van Breugel, Wei Sun and Changwen Miao
pages
1 - 8
publisher
RILEM Publications
place of publication
Bagneux, France
conference name
2nd International Conference on Microstructural-related Durability of Cementitious Composites
conference location
Amsterdam, The Netherlands
conference start
2012-04-11
conference end
2012-04-13
ISBN
9782351581292
language
English
UGent publication?
yes
classification
C1
copyright statement
I have transferred the copyright for this publication to the publisher
id
2106209
handle
http://hdl.handle.net/1854/LU-2106209
date created
2012-05-14 15:15:07
date last changed
2012-05-16 11:36:05
@inproceedings{2106209,
  abstract     = {Nowadays, industrial by-products like fly-ash (FA) and blast-furnace slag (BFS) are commonly used as cement replacing material. In combination with ordinary Portland cement (OPC), the BFS reaction is activated by the presence of alkali hydroxides in the pore solution and the Ca(OH)2 released during the OPC hydration. However, former research has shown that the slag hydration degree significantly decreases in pastes containing very high amounts of slag ({\textrangle} 80\%). Also for FA-OPC mixes with a high FA/OPC ratio ({\textrangle} 50\%), the activation level of the pozzolanic reaction is strongly reduced. While FA and BFS concrete seem to be inferior with regard to the early age microstructure and strength development, their self-healing capability can be much higher, precisely because of the low hydration degree of the slag and fly-ash particles. Upon cracking, the unreacted particles can be activated again in order to close the crack and to regain water impermeability and strength. In this study, autogenous as well as autonomous healing of mixes containing BFS or FA was investigated. First of all, calorimetric measurements were performed in order to evaluate the renewed hydration reactions of crushed pastes (age {\texttildelow} 1 - 2 months), which were brought into contact with water to simulate autogenous healing, or with different activators (NaOH, Na-silicate,{\textellipsis}) to simulate autonomous healing by alkali activation. Secondly, cracks were created in mortar bars with different binder compositions at an age of 28 days. The specimens were then stored under water or in alkaline solutions and the extent to which cracks close was monitored by optical microscopy. The results clearly showed the self-healing capacities of BFS and FA mixes. Based on this study, the most appropriate activators for BFS and FA were chosen.},
  author       = {Gruyaert, Elke and Van Tittelboom, Kim and Rahier, H and De Belie, Nele},
  booktitle    = {Microstructural-related Durability of Cementitious Composites, RILEM Proceedings PRO 83},
  editor       = {Ye, Guang and van Breugel, Klaas and Sun, Wei and Miao, Changwen},
  isbn         = {9782351581292},
  language     = {eng},
  location     = {Amsterdam, The Netherlands},
  pages        = {1--8},
  publisher    = {RILEM Publications},
  title        = {Crack repair by activation of the pozzolanic or slag reaction},
  year         = {2012},
}

Chicago
Gruyaert, Elke, Kim Van Tittelboom, H Rahier, and Nele De Belie. 2012. “Crack Repair by Activation of the Pozzolanic or Slag Reaction.” In Microstructural-related Durability of Cementitious Composites, RILEM Proceedings PRO 83, ed. Guang Ye, Klaas van Breugel, Wei Sun, and Changwen Miao, 1–8. Bagneux, France: RILEM Publications.
APA
Gruyaert, E., Van Tittelboom, K., Rahier, H., & De Belie, N. (2012). Crack repair by activation of the pozzolanic or slag reaction. In G. Ye, K. van Breugel, W. Sun, & C. Miao (Eds.), Microstructural-related Durability of Cementitious Composites, RILEM Proceedings PRO 83 (pp. 1–8). Presented at the 2nd International Conference on Microstructural-related Durability of Cementitious Composites, Bagneux, France: RILEM Publications.
Vancouver
1.
Gruyaert E, Van Tittelboom K, Rahier H, De Belie N. Crack repair by activation of the pozzolanic or slag reaction. In: Ye G, van Breugel K, Sun W, Miao C, editors. Microstructural-related Durability of Cementitious Composites, RILEM Proceedings PRO 83. Bagneux, France: RILEM Publications; 2012. p. 1–8.
MLA
Gruyaert, Elke, Kim Van Tittelboom, H Rahier, et al. “Crack Repair by Activation of the Pozzolanic or Slag Reaction.” Microstructural-related Durability of Cementitious Composites, RILEM Proceedings PRO 83. Ed. Guang Ye et al. Bagneux, France: RILEM Publications, 2012. 1–8. Print.