Cement paste drying shrinkage

Fig. 5.57 Proposed shrinkage mechanisms of cement paste drying a capillary forces, b disjoining pressure, c surface tension, (according to [89])...

Jankovic, D. and Van Mier, J.G.M. (2002) Preliminary Investigation of Drying Shrinkage Cement Paste Specimens. Proceedings of International Conference on New Challenges in Mesomechanics, Aalborg University, Denmark 1, 265-271. 

Neubauer, C.M. (1997) On the Chemistry, Micro structure, and Deformation Properties of Cement Pastes Towards a New Strategy for Controlling Drying Shrinkage. PhD. Thesis, Northwestern University. 

A program of work on cement pastes [45] showed that subsequent rewetting and drying in the presence of neutralized wood resins showed no increase in shrinkage in comparison to a plain paste. The results are given in Fig. 3.37. 

Aggregates are natural or artificial materials with particles of size and shape suitable for the production of concrete. Normally, aggregates occupy a high fraction of the volume of concrete (60-85 %). They allow a reduction in the amount of cement paste (and thus a reduction in both the cost of concrete and the consequences of heat of hydration, drying shrinkage and creep) and they contribute to the mechanical properties of concrete (compressive strength, elastic modulus, wear resistance, etc.). 

Fig. 5.59. a Typical creep curve of cement paste, b creep of paste at simultaneous loading and drying free shrinkage, basic creep, creep at drying, total creep stress, total stress (simultaneous loading and drying)... 

It has been suggested, but is not widely accepted (Kutti, 1992), that—in addition to this C-S-H phase— another amorphous phase that is siUca-rich and which exhibits properties similar to those of silica gel is formed in the initial stage of hydration It contains significant amounts of loosely bound water, which escapes upon drying and is responsible for the shrinkage of the hardened cement paste and the formation of microcracks. 

Figure 21.2 Volume changes and stresses in OPC, shrinkage-compensated and self-stressing cement pastes due to hydration and drying.

McGreath, D. R., Newman, J. B., Newman, K. (1969) The influence of aggregate particles on the local strain distribution and fracture mechanism of cement paste during drying shrinkage and loading to failure . Bull. RILEM, 2(7). 

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