Concrete is one of the essential construction materials that requires many natural resources for production and releases much pollution such as greenhouse gases. As a cement replacement material, fly ash is an essential tool to reduce the environmental impacts of cement production. The main objective of this study was to evaluate the bond strength between concrete and reinforcement for different fly ash levels. In the experiments, 5%, 15%, and 25% of Portland cement were replaced by fly ash, while the water-to-binder ratio (w/b) was kept constant at 0.42. Standard test specimens of 15 cm containing a 16-mm-diameter bar at the center were used in bond strength tests. Bond strength was measured at 7, 28, and 90 days of age through a direct pull-out test. The results show that adding fly ash with any percentage reduces the bond strength at an early age while replacing 15% cement with fly ash has more positive effects as it enhances bond strength up to 20% in the long term. Evaluation of existing models for predicting bond strength also showed that these models' average provided greater bond strength than experimental results in 28 days. Therefore, it is necessary to provide an appropriate model for estimating the bond strength of concrete containing fly ash.

混凝土是基本的建筑材料之一，需要大量的自然资源进行生产并释放出许多污染物，例如温室气体。作为水泥的替代材料，粉煤灰是减少水泥生产对环境的影响的重要工具。这项研究的主要目的是评估不同粉煤灰水平下混凝土与钢筋之间的粘结强度。在实验中，用粉煤灰代替了5％，15％和25％的波特兰水泥，而水灰比（w / b）保持恒定在0.42。在结合强度测试中使用15 cm的标准试样，其中心有一个16 mm的直径的试条。通过直接拉出测试在7、28和90天龄时测量粘合强度。结果表明，以任何百分比添加粉煤灰会降低早期的粘结强度，而用粉煤灰替代15％的水泥则具有更积极的作用，因为从长远来看，它将提高粘结强度至20％。对现有模型预测粘结强度的评估还显示，这些模型的平均值在28天之内提供的粘结强度高于实验结果。因此，有必要提供一个合适的模型来估算含粉煤灰的混凝土的粘结强度。