# Experimental Study on a Prediction Model of the Shrinkage and Creep of Recycled Aggregate Concrete
## 1 Introduction
This proves that the shrinkage prediction model of ordinary concrete is not suitable for RAC, so research on a prediction model of the shrinkage and creep of RAC has become the focus of solving the problem of the shrinkage and creep of RAC. [PERSON] et al. [18] pointed out that the prediction model of RAC creep should consider the influence of mortar attached to the aggregate surface. Based on the MC90 model, the predicted values of the model agree well with the experimental values. [PERSON] et al. [19] studied the Gomez-Soberon test data, and the concrete creep coefficient was corrected considering the difference in apparent density or water absorption between recycled aggregate and natural aggregate. Based on the European standard EC2 model, [PERSON] (D) and [PERSON] (R) obtained two kinds of RAC creep prediction models. The prediction accuracy of the two models is good. [PERSON] et al. [20] explored the effect of recycled aggregates on the creep of concrete. It was pointed out that when using the creep prediction model of fib Model Code 2010 to predict the creep coefficient of RAC, the creep coefficient of RAC is underestimated relative to the performance of the model on the accompanying natural aggregate concrete (NAC). At the same time, compared with NAC, RAC shows a larger creep coefficient, and the average increase in the coefficient of creep is 39% for RAC at full replacement rate. [PERSON] et al. [21] studied the correction coefficient of the concrete creep of different recycled aggregates and a prediction model suitable for recycled aggregate concrete. Compared with conventional concrete, the use of recycled aggregate to absorb part of the mixed water and cement slurry for coating produces a stronger ITZ (Interface transition zone), which can reduce the creep strain by up to 23%. [PERSON] et al. [22] explored the calculation method of the long-term deformation of recycled concrete beams based on the creep adjustment coefficient. At the same time, the adjustment coefficient of the mortar creep bond was proposed. Three typical ordinary concrete shrinkage and creep prediction models were modified and used for long-term deformation calculation of recycled concrete beams. [PERSON] et al. [23] proposed a model for the shrinkage and creep of RAC that considered the two factors of the regenerated aggregate grade and substitution rate, and the regression coefficient was used to obtain the influence coefficient expression. This can quantitatively calculate the influence coefficient of the shrinkage and creep of recycled aggregates with different quality and different substitution rates. [PERSON] et al. [24] studied the influence coefficient of aggregate pretreatment on the creep behavior of RAC. [PERSON] et al. [25] corrected the q2 and q4 parameters in the B3 model based on the test results. Considering the influence of the replacement rate of the RCA, the calculated results of the modified model were in good agreement with the experimental results. However, the existing method of proposing the correction coefficient by a certain influencing factor fails to establish the prediction model of the shrinkage and creep of RAC. In particular, for the effect of recycled aggregate-attached mortar on concrete shrinkage and creep, there is a lack of predictive models with universal significance. In this paper, the key difference between recycled aggregate and natural aggregate-attachment mortar is taken as the entry point, and the coefficient of increase and the coefficient of contraction increase of the attached mortar are proposed. Based on the two increasing factors, the shrinkage and creep model of RAC is established, and the applicability of the model is checked.