Activation of Pozzolanic and Latent-Hydraulic Reactions by Alkalis in Order to Repair Concrete Cracks

AbstractThe low degree of hydration of fly ash (FA) and slag (BFS) particles in high-volume FA and BFS concrete offers the possibility to activate the unreacted particles upon crack formation to close the crack. In this paper, a preliminary study is performed to evaluate the use of alkaline activators to stimulate the formation of reaction products in the crack. First, the reaction rates of crushed pastes mixed with alkaline solutions or water were monitored by calorimetry. These tests showed that alkaline activators stimulate the reactions more than water. Secondly, cracked mortar beams were stored in different alkaline solutions or water and the crack self-closing ratio was calculated after microscopic investigation at different time intervals. The results indicated that reference mixes, containing only ordinary portland cement as binder, heal very well autogenously, while a solution of Ca(OH)2+Na2CO3 seems to be the most suitable activator to stimulate crack closing of BFS concrete. Thirdly, the regain...

[1]  Raktipong Sahamitmongkol,et al.  Self-crack closing ability of mortar with different additives , 2011 .

[2]  Nele De Belie,et al.  Use of silica gel or polyurethane immobilized bacteria for self-healing concrete , 2012 .

[3]  G. K. Moir,et al.  Degrees of reaction of the slag in some blends with Portland cements , 1996 .

[4]  W. Verstraete,et al.  Use of bacteria to repair cracks in concrete , 2010 .

[5]  Patric Jacobs,et al.  Self-healing efficiency of cementitious materials containing tubular capsules filled with healing agent , 2011 .

[6]  Tran Diep Phuoc Thao,et al.  Implementation of self-healing in concrete – Proof of concept , 2009 .

[7]  D. Roy,et al.  Chemical Activation of Low Calcium Fly Ash Part 1: Identification of Suitable Activators and their Dosage , 2001 .

[8]  D. Roy,et al.  Chemical Activation of Low Calcium Fly Ash Part II: Effect of Mineralogical Composition on Alkali Activation , 2001 .

[9]  P. Dubruel,et al.  Self-healing cementitious materials by the combination of microfibres and superabsorbent polymers , 2014 .

[10]  Gert Baert,et al.  Physico-Chemical Interactions in Portland Cement - (HighVolume) Fly Ash Binders. , 2009 .

[11]  Henk M. Jonkers,et al.  Quantification of crack-healing in novel bacteria-based self-healing concrete , 2011 .

[12]  R. H. Atkinson.  Recent advances in the applied chemistry of the rare metals. Jubilee memorial lecture , 1940 .

[13]  Nele De Belie,et al.  Acoustic emission analysis for the quantification of autonomous crack healing in concrete , 2012 .

[14]  Nele De Belie,et al.  Purdocement: application of alkali-activated slag cement in Belgium in the 1950s , 2015 .

[15]  Erich D. Rodríguez,et al.  Effect of binder content on the performance of alkali-activated slag concretes , 2011 .

[16]  Carolyn M. Dry,et al.  Three-part methylmethacrylate adhesive system as an internal delivery system for smart responsive concrete , 1996 .

[17]  B. Münch,et al.  Quantification of fly ash in hydrated, blended Portland cement pastes by backscattered electron imaging , 2013, Journal of microscopy.

[18]  K. Scrivener,et al.  Methods for determination of degree of reaction of slag in blended cement pastes , 2012 .

[19]  E. Gruyaert.  Effect of blast-furnace slag as cement replacement on hydration, microstructure, strength and durability of concrete , 2011 .

[20]  Hubert Rahier,et al.  Influence of mix composition on the extent of autogenous crack healing by continued hydration or calcium carbonate formation , 2012 .

[21]  N. Robeyst,et al.  Study of the hydration of Portland cement blended with blast-furnace slag by calorimetry and thermogravimetry , 2010 .

[22]  Nele De Belie,et al.  Mechanical and self-healing properties of cementitious composites reinforced with flax and cottonised flax, and compared with polyvinyl alcohol fibres , 2012 .