Autogenous and drying shrinkage of structural concretes incorporating recycled concrete aggregates from different sources

Abstract

The main relevant difference between recycled concrete aggregates (RCAs) in comparison with the companion natural ones, is the presence of the Attached Mortar content which confers to the RCAs higher porosity and, consequently, higher water absorption capacity. In the last decades, several studies have been performed worldwide for unveiling the role of the employed RCAs on the resulting concrete mixture performances at both fresh and hardened states. On the other hand, the effects of RCA on the early‐age and/or long‐term concrete deformations (e.g., shrinkage) are still very limited. In this context, this article summarizes the results of a wide experimental campaign aimed at evaluating the influence of RCAs on the autogenous and drying shrinkage of normal (35 MPa) and high (60 MPa) strength recycled aggregate concrete (RAC) mixtures. A total of 10 mixtures were realized by considering the variation of both the original source and size of employed RCAs. The results showed a clear correlation between the intrinsic properties (i.e., Attached Mortar content) of the employed RCAs and the resulting concrete deformation. Moreover, although the drying shrinkage is higher for RAC mixtures, the presence of a more porous aggregates mitigates the observed autogenous shrinkage. Consequently, the overall total shrinkage result to be almost unaffected by the presence of the recycled particles.

Flexural stiffness of recycled aggregate concrete beams under combined effect of load and steel corrosion

“…In addition, there is a great deal of micro‐cracks formed in RCA because of the damage accumulation in the early crushing process of waste concrete. As a result, RCA has the characteristics of large porosity, high water absorption, low bulk density, high crushing index, and high micro‐powder content 6,7 . A large amount of defects is introduced in RAC, which includes the old mortar, more types and larger content of interfacial transition zones 8 .…”

“…As a result, RCA has the characteristics of large porosity, high water absorption, low bulk density, high crushing index, and high micro-powder content. 6,7 A large amount of defects is introduced in RAC, which includes the old mortar, more types and larger content of interfacial transition zones. 8 Resulting from these defects, the mechanical properties [9][10][11][12] and durability [13][14][15][16] of RAC are lower than those of NAC.…”

Compressive stress–strain model for the estimation of the flexural capacity of reinforced geopolymer concrete members

“…Although based on the material cost, the cost of GPC is greatly superior to the CVC due mainly to the used alkali activators and, in addition, fly ash and ground granulated blast slag (GGBS) are hardly available in several regions of the globe, its positive effect to the environment is one of its driving reason for preference over CVC. Thus, researchers try to come up with new sources to be utilized in the construction practice other than CVC and ordinary steel 5–8 . Globally, there are many ongoing research and development studies on the GPC as a promising alternative to CVC 9–13 .…”

“…Thus, researchers try to come up with new sources to be utilized in the construction practice other than CVC and ordinary steel. [5][6][7][8] Globally, there are many ongoing research and development studies on the GPC as a promising alternative to CVC. [9][10][11][12][13] While these studies have mainly positioned on the investigation of thermal characteristics, microstructural properties, electrical conductivity, and durability, some limited research on structural performance has been conducted by testing large-scale structural components.…”