The combined effect of load and corrosion on the flexural performance of recycled aggregate concrete beams

The use of Recycled aggregate (RA) enhances concrete sustainability. If used on an industrial‐scale, structural verification, and testing will be required to confirm that RA concrete can meet relevant industrial standards and the requirements of manufacturers, especially in the precast‐concrete industry. In this paper, an experimental campaign with the participation of a precast‐concrete manufacturer is reported. The objective is to test a self‐compacting concrete (SCC) mix, designed for structural applications, that contains maximum amounts of 100% coarse RA, in order to establish its compliance with the habitual requirements of precast‐concrete manufacturers. Thus, scaled beams (12 × 24 × 180 and 24 × 24 × 130 cm) were subjected to bending, shear‐bending, shear, and long‐term‐deflection tests. In addition, the performance of that SCC mix in the bending and shear‐bending tests was compared with the performance of an SCC mix of similar compressive strength containing 0% coarse RA. In the failure tests, the experimental results were between 1.5 and 3 times higher than the required values. The elastic behavior of both SCC mixes was also very similar in those tests, regardless of the amount of coarse RA, due to the robust design of the water and superplasticizer content of the SCC, which balanced the decreased flowability and the lower compressive strength of SCC that resulted from the additions of coarse RA. The SCC mix with 100% RA showed a lower load‐bearing capacity after failure and narrow compliance margins with the deflection limits of the long‐term‐deflection test. Even though the SCC mix with 100% RA met all the standard technical specifications of the precast‐concrete manufacturer, reference should always be made to the serviceability limit states that are applicable at the time of the structural design phase.

Section: Introductionmentioning

confidence: 99%

Scaled concrete beams containing maximum levels of coarse recycled aggregate: Structural verifications for precast‐concrete building applications

Fiol

Revilla‐Cuesta

Skaf

et al. 2023

“…[33][34][35][36] To date, a number of researchers have investigated several properties of RAC with notable reviews on RAC that proved to be much more effective in terms of durability and mechanical aspects. 5,[37][38][39][40][41][42] Different studies suggested a reduction in the COS by 10%-20% with enhancement in the substitution of natural coarse aggregates (NCA) by recycled coarse aggregates (RCA). [43][44][45] Setting the cement content and water-to-cement (W/C) ratio the same, when NCA was substituted by RCA, the COS of RAC was dropped by 20%-25% in comparison to traditional concrete.…”

Section: Introductionmentioning

confidence: 99%

Effectiveness of FRP confinement for low strength recycled aggregate concrete compressive members having optimized combination of fibers

Raza,

Elhag,

Ouni

et al. 2023

The quantity of recycled concrete aggregates is increasing day by day due to the enhanced demolition rate of old infrastructures, which is dangerous to the environment's sustainability. Therefore, it is essential to handle these recycled aggregates for sustainable development. Furthermore, due to the low compressive strength (COS) of recycled aggregate concrete (RAC), it has always remained an active research area to ameliorate the mechanical performance of such concrete by either adding fibers and/or laterally confining with carbon fiber reinforced polymer (carbon‐FRP) wraps. The main objective of the current investigation is to improve the strength of hybrid fiber‐reinforced recycled aggregate concrete (HFRAC) transversely wrapped with carbon‐FRP wraps. The axial COS, axial strain, and compressive stress–strain graphs of the tested samples were assessed by manufacturing a total sum of 18 cylindrical samples wrapped with either one or two carbon‐FRP wraps. Two different grades of HFRAC were fabricated that is, 15 and 20 MPa containing hybrid fibers (steel and polypropylene fibers). The results showed that the transverse wrapping effectively ameliorated the axial strain, COS, and axial stiffness of HFRAC samples. By using a single layer of carbon‐FRP wraps, an enhancement of 115.7% was observed while using two layers of carbon‐FRP wraps, an enhancement of 130.7% was observed in the COS of 15 MPa group HFRAC samples. Similarly, by using a single layer of carbon‐FRP wraps, an enhancement of 37.4% occurred while using two layers of carbon‐FRP wraps, an enhancement of 112.6% occurred in the COS of 20 MPa group HFRAC samples. Hence, the lateral wrapping of low‐strength HFRAC is more efficient than the high‐strength HFRAC. A theoretical investigation based on the analysis of 11 different models was also performed to predict the COS of carbon‐FRP‐wrapped HFRAC samples.

“…In their test, there were three beams in each group, of which one beam was the control beam, and the other two beams were loaded (i.e., 60% of the flexural capacity), and the corrosion‐induced cracking and degradation of flexural performance of RAC beams under combined effect of load and steel corrosion were studied. Wang and Xu 30 investigated the combined effect of load and steel corrosion on the flexural performance of RAC beams, and found that both yield bending moment and ultimate bending moment of corroded RAC beams decreased with the increase of load level (i.e., the ratio of the load applied to beams to the ultimate load) and RCA replacement ratio. Wang et al 31 found that for the corroded beams with 50% RCA replacement ratio, when the load level increased from 0 to 0.6, the ultimate load and ultimate deflection reduced by 10.4% and 21.2%, respectively, whereas for the corroded beams with 100% RCA replacement ratio, the corresponding reduction of ultimate load and ultimate deflection were 8.9% and 35.5%, respectively.…”

Section: Introductionmentioning

confidence: 99%

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

Wang

Qin

2023

Self Cite

Since reinforced concrete members suffer from different types of loads during their service life, the steel bars embedded in reinforced concrete members can be easily corroded in chloride‐laden environment. To investigate the influence of combined effect of load and steel corrosion on the flexural stiffness of recycled aggregate concrete (RAC) beams, 12 RAC beams were prepared and tested. The effects of load level (i.e., the ratio of the load applied to beams to the ultimate load) and recycled coarse aggregate (RCA) replacement ratio (i.e., the ratio of RCAs to replace natural coarse aggregates) on the internal force arm coefficient of cracking cross‐section, the elastoplastic resistance moment coefficient of cross‐section, and the strain incongruity coefficient of corroded tensile steel bars were analyzed, and a calculation model for flexural stiffness of RAC beams under combined effect of load and steel corrosion was established. The results showed that when the ratio of bending moment to ultimate bending moment of the pure bending part of beams was within 0.55–0.80 and the average mass loss of tensile steel bars was less than 3.23%, 0.85 could be adopted as the internal force arm coefficient of cracking cross‐section. The elastoplastic resistance moment coefficient of cross‐section was approximately a constant when the corroded RAC beams were in the service stage, while it increased obviously with the load level. There was a strong linear relationship between strain incongruity coefficient and average mass loss of tensile steel bars during the service stage of corroded RAC beams, and the strain incongruity coefficient increased linearly with the load level. The calculated values of the model of flexural stiffness proposed in this paper were in reasonable agreement with the experimental values.