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Doctoral thesis (Dissertations and theses)
Re-use of fine recycled concrete aggregates for the manufacture of mortars
Zhao, Zengfeng
2014
 

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Keywords :
fine recycled concrete aggregates; water absorption; hardened cement paste content
Abstract :
[en] Very large quantities of construction and demolition wastes and especially concrete wastes are produced yearly. At the same time, high amounts of natural aggregates are needed for construction industry. Up to now, only a small fraction of these concrete wastes is re-used as recycled concrete aggregates (RCA) for the manufacture of concrete. RCA are composed of an intimate mix between aggregates and hardened cement paste (HCP). Hardened cement paste is much more porous than the natural aggregates and the properties and proportions of HCP largely influence the properties of RCA. As a consequence, the fine fraction of RCA (FRCA), essentially composed of mortar and cement paste, possesses a large water demand which makes it harder to recycle into concrete. The objective of this research was to better understand the role played by HCP on the properties of RCA in relation with the improvement of the characterization methods of these materials and their reuse in the manufacture of mortar or concrete. Firstly, an experimental method based on salicylic acid attack of RCA allowed us to determine a soluble fraction in salicylic acid (SFSA) that is related to the HCP content. FRCA properties were then studied as a function of SFSA, particle sizes and properties/composition of the original concrete. From the obtained relationship between water absorption and SFSA, the water absorption coefficient of the smaller fraction (0/0.63mm) was estimated as it is not accurately measured with the standard methods. Secondly, different industrial RCA were characterized which allowed us to expand the preceding conclusions to “real RCA”, meanwhile, the influence of carbonation on the properties of FRCA was also carried out. Finally, the influence of the saturation state of FRCA on the properties of fresh and hardened mortars and on their microstructure was explored. The recycled mortars with dried FRCA had better compressive strength than that made with saturated FRCA, which was confirmed by the study of ITZ properties. The mechanical properties of mortars with different RCA content and replacement fraction were determined. The finer fraction of RCA had a worse influence on the mechanical properties of RAC than the coarser fraction.
Disciplines :
Civil engineering
Author, co-author :
Zhao, Zengfeng ;  Université de Liège - ULiège > Département ArGEnCo > Matériaux de construction non métalliques du génie civil
Language :
English
Title :
Re-use of fine recycled concrete aggregates for the manufacture of mortars
Alternative titles :
[en] Valorisation des sables de béton recyclé pour la fabrication de mortiers
Defense date :
14 February 2014
Number of pages :
197
Institution :
Université Lille 1, Lille, France
Degree :
PhD degree
Promotor :
Sébastien REMOND
Available on ORBi :
since 07 November 2019

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