Aggregate-cement paste interface

Monteiro, P. J. M. Mehta, P. K. 1985. Ettringite formation on the aggregate-cement paste interface. Cement and Concrete Research, 15, 378-380. 

W.A. Tasong, C.J. Lynsdale and J.C. Cripps Aggregate-cement Paste Interface Part I. Influence of Aggregate Geochemistry, Cement and Concrete Research Vol. 29 (1999), p. 1019-1025. 

Tasong, W.A., Lynsdale, C.J., Cripps, J.C., 1998. Aggregate-cement paste interface I Influence of aggregate physical properties. Cement Concrete Res, 28(10) 1453-65. 

Figure 7.1 Scheme of aggregate-cement-paste interface. Possible positions of debonding fracture in composites with different components are indicated, after Odler and Zurz (1988). 

Aligizaki, K. du Rooij, M.R. Macdonald, D.D. (2000) Analysis of iron oxides accumulating at the interface between aggregates and cement paste. Cement Concrete Res. 30 1941-1948... 

Interfaces of calcium aluminate cements with aggregates were discussed in Chapter 10. The interfacial zone between Portland cement paste and steel has been studied by SEM, using various techniques of specimen preparation (e.g. A31,B153). The major features observed have been substantial deposits of CH and, further away from the interface, a relatively weak, porous zone. Bentur ct al. (B135) also reported the occurrence of a duplex film. Interfaces of cement or CjS pastes with zinc (A32,T58) or copper (T58) have been studied. 

K.L. Scrivener A.K. Crumbie P. Laugesen. The interfacial transition zone between cement paste and aggregate in concrete. Interface Science (2005). DOI 10.1023/B INTS.0000042339.92990.4c. 

The construction of interfacial transition zone aroiuid the reinforcement in concrete is very similar to the aggregate paste interface. This is presumably the consequence of locally occurring higher w/c ratio, promoting dissolution of cement components and crystallization of cement hydration products from the liquid phase. This interfacial transition zone reveals also higher porosity and lower strength than the bulk cement matrix. 

Tamimi, A.K., and Al-Najeim, H. (1994) XRD and SEM investigations of the cement paste—aggregate interface for concrete produced by both the conventional mixing and a new mixing technique, in Proceedings 16th International Conference on Cement Microscopy, pp. 354-368. 

Xie, P., and Tang, M. (1988) Effect of Portland cement paste—aggregate interface on electrical conductivity and chemical corrosion resistance of mortar. II Cemento 85,33-42. 

Figure 6.10 shows how the permeability of cement paste increases with the tvic ratio. At first it increases slowly and beyond wIc = 0.5 it increases rapidly. The permeability may therefore be regarded as an indirect and partial measure of porosity. Considering the components of cement-based composites it may be assumed that the permeability is determined more by matrix properties than by aggregate ones. Particularly, the matrix/aggregate interface may have the largest content of pores and microcracks which affect the overall permeability (cf. Chapter 7). 

Figure 7.3 Variation of micro-hardness in the interface between aggregate grains and cement paste for various kinds of aggregate, after Lyubimova and Pinus (1962).

The mechanical role of the interface is visible in the overall behaviour of the cement-based composites. Both components - aggregate grains and hardened cement paste - behave separately as linear elastic and brittle bodies in a relatively large domain of applied stresses. However, these two components form a material with a non-linear and inelastic stress-strain relation almost at the beginning of the stress-strain cnrve. This is cansed by the microcracks, which appear and develop nnder tension, shearing and bending mostly in the system of interfaces. 

Scrivenei K. L., Crumbie, A. K., Laugesen P. (2004) The Interfacial Transition Zone (ITZ) between cement paste and aggregate in concrete Interface Science, 12(4) 411-21. 

Struble, L. (1988) Microstructure and fracture at the cement paste-aggregate interface , in Proc. Symp. Bonding in Cementitious Composites, Boston, 2—4 December 1987, Pittsburgh, Pennsylvania Materials Research Society, pp. 11-20. 

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