TG–DTG–DTA in studying white self-compacting cement mortars

• Published in: Journal of thermal analysis and calorimetry 2012-08, Vol.109 (2), p.797-806
• Main Authors: Petkova, V., Stoyanov, V., Pelovski, Y.
• Format: Article
• Language: English
• Subjects: Analysis; Analytical Chemistry; Applied sciences; Buildings. Public works; Carbonates; Chemistry; Chemistry and Materials Science; Concretes. Mortars. Grouts; Exact sciences and technology; General (composition, classification, performance, standards, patents, etc.); Hydrates; Inorganic Chemistry; Materials; Measurement Science and Instrumentation; Physical Chemistry; Polymer Sciences; Powders; Zeolites
• ISSN: 1388-6150; 1588-2926; 1572-8943
• DOI: 10.1007/s10973-012-2447-7

Self-compacting cement mortars and concretes are characterized with an excellent workability and with high early strengths, which makes them suitable for elements in pre-cast concrete. Both the dense structure and the non-defected surface of self-compacting mixes are achieved by the incorporation of relatively large amounts of fine mineral additives and use of polycarboxylate admixtures. All these advantages determine the great potential for manufacturing of architectural elements and details. However, there exist many features in the structure-formation and the hardening of these systems. The authors investigate in this study the evolution of the process of curing and the crystal formation up to the 120th days of water-curing. Moreover, the effects of replacement of 10 wt% white cement with natural zeolite are studied. Special attention is paid to the thermal analysis through which one determines the effects of dehydration of the new-formed crystal hydrates, de-carbonization of carbonate-containing phases, and zeolite incorporation. Differences in the thermal behaviour of self-compacting mortars are compared with two types of referent samples. The thermal experiments were complemented with physical–mechanical and structural measurements, including mercury intrusion porosimetry, powder X-ray diffraction and scanning electron microscopy. Experiments and analysis, both determining the development of the microstructure, indicate the formation of a dense structure of white self-compacting mortars. This is achieved at the early age impeding the growth of new crystals. The incorporation of zeolite increases the early strengths of samples, thus making the structure denser, and completely blocking the water permeability. As the zeolite is a soft and ductile mineral, it can be expected that the volume deformations of microstructure of the zeolite-containing mortars, are reduced.