Contraction gradient induced microcracking in hardened cement paste

Drying induced cracking of concrete surfaces and repair layers is a common problem. A principal cause for this type of cracking is the moisture and resulting contraction gradient that develops in the cement paste matrix upon drying. This phenomenon has been experimentally quantified in unconfined hardened cement paste samples using a fluorescent resin impregnation technique. The effects of sample thickness and drying method on surface crack density and crack penetration depth are reported and explained. Finite element modelling of moisture gradients indicate the important role of the film coefficient in desiccation cracking of unconfined samples. The critical thickness for samples to remain crack-free upon drying was in the range of 2-5 mm depending on drying method. In thicker samples a crack spacing doubling process was observed that is in agreement with theoretical predictions.

[1]  Farid Benboudjema,et al.  Analysis of microcracking induced by differential drying shrinkage , 2008 .

[2]  Akhter B. Hossain,et al.  The Role of Specimen Geometry and Boundary Conditions on Stress Development and Cracking in the Restrained Ring Test , 2006 .

[3]  Geoffrey Mays,et al.  Durability of Concrete Structures : Investigation, repair, protection , 1990 .

[4]  H.-J. Weiss,et al.  Multiple crack propagation in a strip caused by thermal shock , 1988 .

[5]  J. Bisschop,et al.  Drying shrinkage microcracking in cement-based materials , 2002 .

[6]  Yunping Xi,et al.  Moisture diffusion in cementitious materials Moisture capacity and diffusivity , 1994 .

[7]  Mohammed H. Baluch,et al.  Calculating Drying Shrinkage Stresses , 2008 .

[8]  W. Clegg,et al.  The effect of porosity in thermal shock , 2008, Journal of Materials Science.

[9]  Raoul François,et al.  Effect of crack opening on the local diffusion of chloride in cracked mortar samples , 2008 .

[10]  Jean-Michel Torrenti,et al.  Thoughts about drying shrinkage: Experimental results and quantification of structural drying creep , 1997 .

[11]  Sidney Mindess,et al.  Acoustic Emission in the Drying of Hardened Cement Paste and Mortar , 1981 .

[12]  A. Leemann,et al.  Shrinkage and restrained shrinkage cracking of self-compacting concrete compared to conventionally vibrated concrete , 2009 .

[13]  David Darwin,et al.  Effect of Cracking on Chloride Content in Concrete Bridge Decks , 2006 .

[14]  Edward L Cussler,et al.  Diffusion: Mass Transfer in Fluid Systems , 1984 .

[15]  B. E. Alaca,et al.  Junction formation during desiccation cracking. , 2006, Physical review. E, Statistical, nonlinear, and soft matter physics.

[16]  Z. Bažant,et al.  Initiation of parallel cracks from surface of elastic half-plane , 1995 .

[17]  Z. Bažant,et al.  Stability and post-critical growth of a system of cooling or shrinkage cracks , 1979 .

[18]  J. Bisschop.  Size and boundary effects on desiccation cracking in hardened cement paste , 2008 .

[19]  E. Jagla.  Stable propagation of an ordered array of cracks during directional drying. , 2002, Physical review. E, Statistical, nonlinear, and soft matter physics.

[20]  Y. Couder,et al.  Hierarchical crack pattern as formed by successive domain divisions. I. Temporal and geometrical hierarchy. , 2005, Physical review. E, Statistical, nonlinear, and soft matter physics.

[21]  Zdeněk P. Baǎnt,et al.  Effect of cracking in drying and shrinkage specimens , 1982 .

[22]  P. Acker,et al.  Drying cracks: Kinematics and scale laws , 2000 .

[23]  Leon M Keer,et al.  Unstable growth of thermally induced interacting cracks in brittle solids , 1978 .

[24]  George W. Scherer,et al.  Mechanism for Salt Scaling , 2006 .

[25]  J. R. Bruyn,et al.  Development and geometry of isotropic and directional shrinkage-crack patterns. , 1999, Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics.

[26]  H.-J. Weiss,et al.  Thermal-shock crack patterns explained by single and multiple crack propagation , 1986 .

[27]  J. Mier,et al.  Effect of aggregates and microcracks on the drying rate of cementitious composites , 2008 .

[28]  E. Kaplan,et al.  An Experimental Study of Cracking Induced by Desiccation , 1994 .

[29]  Sven Thelandersson,et al.  Tension softening and cracking in drying concrete , 1988 .

[30]  S. Shah,et al.  Restrained shrinkage cracking: the role of shrinkage reducing admixtures and specimen geometry , 2002 .

[31]  Chao-Lung Hwang,et al.  Drying shrinkage of portland cement pastes I. Microcracking during drying , 1984 .

[32]  J.G.M. van Mier,et al.  Temporal and spatial development of drying shrinkage cracking in cement-based materials , 2003 .

[33]  J. Dr..  Optimal spacing and penetration of cracks in a shrinking slab. , 2005 .