Influence of lightweight aggregates on internal curing and fracture of concrete

Title: Influence of lightweight aggregates on internal curing and fracture of concrete
Author(s): Burcu Akcay, Mehmet Ali Tasdemir
Paper category : conference
Book title: International RILEM Conference on Volume Changes of Hardening Concrete: Testing and Mitigation
Editor(s): O. M. Jensen, P. Lura, K. Kovler
Print-ISBN: 2-35158-004-4
e-ISBN: 2351580052
Publisher: RILEM Publications SARL
Publication year: 2006
Pages: 31 - 40
Total Pages: 10
Nb references: 23
Language: English

Abstract: Early age autogenous deformations and self-desiccation are usually considered major problems in new generation high performance and ultra high performance concretes (HP/UHPCs). In order to mitigate the effects of early age deformation, dispersed saturated lightweight aggregates (LWAs) can be used as water reservoirs. In this study, experiments have been conducted to determine the effects of volume fractions and the size of saturated LWAs on fracture and mechanical properties of concrete. For this purpose, in concretes prepared with a constant low water to cement ratio, normal aggregates have been replaced by natural LWAs with size fractions of 2-4 mm or 4-8 mm at three different volume fractions such as 10%, 20% and 30% of the total aggregate volume of concrete. The effects of volume fraction and average particle size of LWAs on the load-displacement at mid-span curve are investigated by measuring the fracture energy, the characteristic length, and final displacement. In addition, the nearest surface distribution of LWAs is investigated using the image analysis, and its effects on the autogenous deformation and the fracture properties are determined.
The results imply that the inclusion of fine fraction of LWAs in concrete reduces the autogenous deformation significantly compared to that of the coarse fraction. It is also shown that the fracture energy, final displacement at the mid-span curve of the beam, splitting tensile strength and compressive strength of concrete with fine fraction are higher than those of the concrete with coarse fraction. Within the limits of this work, it is demonstrated that the distance between LWAs is more effective than the mean particle size of LWAs on both the autogenous deformation and fracture properties of concretes. Increasing the replacement ratio of LWAs mitigates autogenous deformation, while having an unfavourable effect on fracture and mechanical properties of concrete for both fine and coarse fraction replacements.

Online publication: 2006-07-30
Publication type : full_text
Public price (Euros): 0.00
doi: 10.1617/2351580052.004