## 1 Introduction  
The progress of modern construction methods and technology requires shortening project construction time as much as possible to ensure construction quality, which requires that the concrete can bear a certain external load in the early stage. Thus, some micropores and microcracks are often produced at early age load-bearing process [1, 2]. The incorporation of supplementary cementitious materials (SCMs) has been widely used in the concrete community to improve performance durability [3, 4]. Thus, the study on the influence of early age damage of concrete on its long-term strength development with the incorporation of SCMs is of great importance in durability prediction. The acoustic emission (AE) method has been widely used to study the internal damage to concrete structures and materials [5, 6]. The characteristic of real-time monitoring of acoustic emission technique can evaluate the material performance or structural integrity by analyzing the elastic wave signals. Thus, compared to other non-destructive testing (NDT) methods, such as digital imaging technology [7], ultrasound method [8], electrical resistivity [9, 10, 11], and computed tomography scanning method [12], the acoustic emission method is more convenient in data collection and analysis. In recent years, the acoustic emission method has developed considerably. [PERSON] [13] introduced a promising acoustic emission model with good noise control performance. [PERSON] and [PERSON] [14] studied the acoustic emission signals on core drilling samples. They found that AE monitoring in the core tests is to be a useful method for the damage estimation of concrete. [PERSON] et al. [15]studied the acoustic emission signals during the uniaxial compression tests on mortars with different mixtures. It was found that the damage constitutive model under uniaxial compression tests accurately reflected the strength and deformation of mortar under different loading rates. [PERSON] et al. [16] studied the uniaxial compressive strength of air-entrained concrete after high-temperature exposure by acoustic emission method. The results indicated that the characteristics of AE event counts during the deformation and failure of concrete samples are basically the same as those of the AE energy. The influence of early age damage on the long-term compressive strength of concrete structures has not been fully understood. On the one hand, the initiation and propagation of microcracks in concrete in the early age pre-loading process might be resolved in the following curing process [17; 18; 19]. Thus, the long-term strength might not be influenced. However, if the early age damage exceeds the damage threshold, the microcracks might not be effectively cured. As a result, the long-term compressive strength might be lower than expected. The addition of supplementary cementitious materials (SCMs) to concrete is an effective method of addressing the early age damage issue since the pozzolanic reaction between SCMs and the hydration products can generate calcium silicate hydrate (C-S-H) products which can heal the microcracks. [PERSON] et al. [20] studied the healing capacity of cementitious composites with different SCMs. The results showed that incorporating SCMs, the microscale pore structures, and the macroscale durability performances of concrete composites showed the same properties as the concrete without early age pre-loading. [PERSON] et al. [21] studied the mechanical properties and self-healing behavior of micro-cracked engineered cementitious composite (ECC) with different dosages of SCMs. It was found that increasing fly ash content results in a higher ECC ductility. Besides, the crack width of ECC with more fly ash content is reduced, which can be attributed to the self-healing effect. In this work, the curing effect of concrete with SCMs after early age damage was studied by acoustic emission technique. Concrete samples with and without SCMs were pre-loaded at different ages up to 28 d with different damage degrees.