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Chapter 8.
Curing and Autogeneous shrinkage of concrete
Link to NIST internal curing web site
This chapter describes experimentally, with some modeling ideas, the
autogeneous shrinkage
of concrete. Some means of ameliorating this ubiquitous phenomenon in
high performance concrete are also discussed.
This section discusses experimental results on the use of various means of
internal curing (having internal sources of water) to alleviate autogeneous
shrinkage in low water:cement ratio concrete.
(1)
Mitigating Autogeneous Shrinkage by Internal Curing
(10 pages of text, 1027K of figures)
This section describes computer modelling and experimental studies of the influence of cement particle size distribution on the autogeneous properties (internal RH, strain, and stress) of cement pastes.
(2) Influence
of cement particle size distribution on early age autogenous strains and
stresses in cement-based materials (12 pages of text, 120K of
figures)
This section discusses experimental results on the use of various means of
alleviating autogeneous
shrinkage in low water:cement ratio concrete, using surface tension reducing
admixtures, saturated light-weight aggregate, and a coarser silica fume.
(3a) On the Mitigation
of Early Age Cracking (5 pages of text, 24K of figures)
(3b) Mitigation Strategies for
Autogenous Shrinkage Cracking (13 pages of text, 90.5K of figures)
(3c) Suspended hydration and loss of freezable water in cement pastes exposed to 90 %
relative humidity (36 pages of text, 138.4K of figures)
(3d) Curing,
Hydration, and Microstructure of Cement Paste (24 pages of text, 365.1K of
figures)
(3e) Potential Applications of
Shrinkage-Reducing Admixtures beyond Drying Shrinkage Reduction (11 pages of
text, 130K of figures)
The SLABS model for the simulation of curing concrete bridge decks was developed
with new boundary condition formulations that can accurately account for a wide
variety of atmospheric conditions, addressing limitations of previous studies.
Equivalent ages, estimated from the temperature predictions of SLABS, can vary
up to 40 h over the conditions simulated after 24 h of hydration. Depth variations of equivalent ages reach 15 h.
(4a) The Influence
of the Atmosphere on Curing Concrete Temperatures and Maturity (10 pages of
text, 70.4K of figures)
(4b) A Computer Model to
Predict the Surface Temperature and Time-of-Wetness of Concrete Pavements
and Bridge Decks, (19 pages of text, 70.6K of figures)
Proportioning concrete with internal curing requires careful consideration
of the water demand of the hydrating cement paste and the water readily
available from the saturated lightweight aggregates. A preliminary
methodology for this mixture proportioning in presented here.
(5a)
Mixture Proportioning for Internal Curing
(5b) Protected
Paste Volume in Concrete: Extension to Internal Curing Using Saturated
Lightweight Fine Aggregate (7 pages of text, 54K of figures)
(5c) Materials Science-Based
Models in Support of Internal Water Curing (16 pages of text, 791K of
figures)
(5d) Four Dimensional X-Ray Microtomography Study of Water Movement During Internal Curing
The concept of internal curing can be extended from the delivery of curing
water to the potential delivery of chemical admixtures, from the saturated
lightweight fine aggregates to the hydrating cement paste, for example.
A preliminary experimental validation of this concept is provided in this
section.
(6) Capitalizing on
Self-Desiccation for Autogenous Distribution of Chemical Admixtures in
Concrete (10 pages of text, 22.6K of figures)
References
(1) M. Geiker, D.P. Bentz and O.M. Jensen, American Concrete Institute
Special Publication 218, High Performance Structural Lightweight Concrete,
John P. Ries and Thomas A. Holm, eds., pp. 143-154 (2004).
(2) D.P. Bentz, O.M. Jensen, K.K. Hansen, J.F. Olesen, H. Stang, and C.J.
Haecker, J. Amer. Ceram. Soc. 84 (1), 125-139 (2001).
(3a) D.P. Bentz, M. Geiker, and O.M. Jensen, Self-Desiccation and Its
Importance in Concrete Technology, Eds. B. Persson and G. Fagerlund, Lund Sweden,
June (2002).
(3b) D.P. Bentz and O.M. Jensen, Cement and Concrete Composites 26 (6), 677-685 (2004).
(3c) K.A. Snyder and D.P. Bentz, Cement and Concrete Research 34 (11),
2045-2056 (2004).
(3d) D.P. Bentz and P.E. Stutzman, ACI Materials Journal 103 (5), 348-356 (2006).
(3e) D.P. Bentz, Concrete International 27 (10), 55-60 (2005).
(4a) G. Wojcik, Advances in Cement and Concrete, Proceedings of the Engineering
Conferences International, Copper Mountain, CO, August 10-14, 2003, 491-500
(2003).
(4b) D.P. Bentz, National Institute of Standards and Technology Internal Report 6551 August (2000).
(5a) D.P. Bentz, P. Lura, J. Roberts, Concrete International 27 (2), 35-40 (2005).
(5b) D.P. Bentz and K.A. Snyder, Cement and Concrete Research 29
(11), 1863-1867 (1999).
(5c) D.P. Bentz, E.A.B. Koenders, S. Mönnig, H.−W. Reinhardt, K.
van Breugel, and G. Ye, to be published as part of a RILEM state-of-the-art
report (2007).
(5d) D.P. Bentz, P.M. Halleck, A.S. Grader, and J.W. Roberts, Proceedings of
the International RILEM Conference: Volume Changes of Hardening Concrete:
Testing and Mitigation, Eds. O.M. Jensen, P. Lura, and K. Kovler, RILEM
Publications S.A.R.L., 2006, pp. 11-20.
(6) D.P. Bentz, Proceedings of the 4th International
Seminar on Self-Desiccation and Its Importance in Concrete Technology, Eds.
B. Persson, D. Bentz, and L.-O. Nilsson, Lund University (2005) pp. 189-196.