An investigation into the influence of inter-aggregate spacing and the extent of the ITZ on properties of Portland cement concretes

• Published in: Cement and concrete research Vol. 40; no. 11; pp. 1601 - 1608
• Main Authors: Rangaraju, Prasada Rao, Olek, Jan, Diamond, Sidney
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.11.2010; Elsevier
• Subjects: Applied sciences; Buildings. Public works; Cements; Chlorides; Compressive strength (C); Concretes; Concretes. Mortars. Grouts; Elastic moduli (C); Exact sciences and technology; General (composition, classification, performance, standards, patents, etc.); Grains; Interfacial transition zone (B); Materials; Mean inter-aggregate spacing; Particle size distribution; Pastes; Permeability; Sand; Transport properties (C); Elastic moduli (C); Interfacial transition zone (B); Mean inter-aggregate spacing; Transport properties (C); Compressive strength (C); Scanning electron microscopy; Elastic modulus; Transport properties; Construction materials; Concrete mix design; Mechanical properties; Cement concrete; Spacing; Compressive strength; Experimental study; Transition zone; Portland cement; Interfacial area; Comparative study
• ISSN: 0008-8846; 1873-3948
• DOI: 10.1016/j.cemconres.2010.07.002

Conventionally-designed concretes were prepared with different sand particle size distributions, so as to systematically vary the extent of aggregate-cement paste interface and the mean spacing between sand grains. The range of fineness modulus of the sands fully encompassed the range of sands normally used in concretes. The concretes were batched at w/c ratios of 0.30 and 0.50 and cured for various periods before carrying out determinations of mechanical properties and of “rapid chloride permeability”. The conventional notions of the effect of the ITZ on concrete properties would predict that a reduction in strength and an increase in chloride permeability would accompany increased ITZ interfacial area and closer spacing between sand grains. In general, no such influence was found. It appears from this research that the traditional notions of the adverse influence of the ITZ on the properties of conventional concretes may not be accurate, within the realms of conventional concrete and typical inter-aggregate spacings.