Abstract
Sixteen full-scale recycled aggregate concrete (RAC) beams were cast and tested to study their time-dependent behavior under long-term loading. The test parameters include the replacement rate of the recycled coarse aggregates (RCAs), the replacement rate of the recycled fine aggregates (RFAs), the concrete strength, and the stress ratio. The influence of the above variables on the deflection and stiffness is discussed. The results show that the RCAs will increase the deflection of the specimen at a low stress ratio; at a high stress ratio, the beams will experience nonlinear creep, and the deflection of the specimen will be affected by the RCAs and the stress ratio. The RFAs have a substantial influence on the time-dependent behavior of the specimen, and the deflection of the specimen with 100% replacement of recycled aggregates can increase by 30%; the strength of the concrete does not have a substantial influence on the time-dependent behavior of the specimen; and the stress ratio has an influence on the initial deflection of the specimen. A deflection calculation formula is established based on the stress–strain relationship of the beam under long-term loading and the characteristics of the RAC. The calculation results are in good agreement with the test results.
Highlights
Recycled aggregate concrete (RAC) is a kind of concrete that is made by replacing different percentages of the coarse and fine aggregates in natural aggregate concrete (NAC) with coarse and fine aggregates obtained by waste materials, such as, waste concrete, brick, tile, and rubber [1,2]
The deformation of RAC under long-term loading is mainly composed of instantaneous deformation under loading and continuous deformation under long-term loading
It can be seen the and there is no obvious difference in the stiffnesses of the specimens at a low stress ratio; at a high change trends of the stiffnesses of the specimens under different recycled coarse aggregates (RCAs) replacement rates are similar, stress ratio, theobvious regularity of the stiffness is the same as its compressive strength, and there is no and there is no difference in the stiffnesses of the specimens at a low stress ratio; at a high stress ratio, the regularity of the stiffness is the same as its compressive strength, and there is no obvious relationship with the RCA replacement rate
Summary
Recycled aggregate concrete (RAC) is a kind of concrete that is made by replacing different percentages of the coarse and fine aggregates in natural aggregate concrete (NAC) with coarse and fine aggregates obtained by waste materials, such as, waste concrete, brick, tile, and rubber [1,2]. In the study of the time-dependent behavior of RAC beams [25,26,27], it is generally accepted that the addition of recycled aggregates will increase the long-term deflection of RAC beams because of the large creep and shrinkage of RAC. For calculation of the long-term deflection of RAC beams, a large number of studies are based on a partial correction by considering some influencing factors [35,36,37,38], which cannot accurately measure the long-term deflection of recycled concrete beams. It is important to study the influence of different factors on the time-dependent behavior of full-scale RAC beams through experiments and to propose a long-term deflection calculation formula for RAC beams. To study the time-dependent behavior of full-scale RAC beams under different influencing factors, 16 full-scale RAC beam specimens are tested under long-term loading scenarios. Based on the stress–strain analysis of the beams and the characteristics of the RAC, a long-term deflection calculation formula for RAC beams is established
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