Pathan Qazi Amjad Ali, Qureshi Abdul Sami, Mangi Sajjad Ali
Department of Civil Engineering, Mehran University of Engineering and Technology, Jamshoro, Pakistan.
Department of Civil Engineering, Mehran University of Engineering and Technology, SZAB Campus, Khairpur Mir's, Sindh, Pakistan.
Environ Sci Pollut Res Int. 2022 May;29(21):32238-32245. doi: 10.1007/s11356-021-17807-6. Epub 2022 Jan 11.
Durability performance of concrete is enhanced by adding supplementary cementitious materials such as fly ash. The concrete made with addition of fly ash with Portland cement is called fly ash cement concrete (FACC). Generally, modelling approach is applied to predict the service time of concrete in aggressive environment. Most degradation of concrete is found in marine environment, due to the exposure of concrete to chlorides. Service life modelling is performed using diffusion equation (Eq. 1) with diffusion coefficient (D) equation (Eq. 2), and to get the diffusion coefficient (D) over time, ageing factor is used for analysis. During modelling stage, as this phase of study is started well before construction, concrete for its durability performance is checked. As well, service life modelling is performed for the existing structures, so that the time to failure may be obtained. In recent times, failure of Miami Building, USA, June 2021, has raised the importance of service life modelling (SLM) of reinforced concrete structures (RCC) in chloride environment. So, in such environments, a more need of more reliable results is raised. Presence of a number of ageing factors in literature raises a question which ageing factor is more approximate. Dependency of performance of modelling approach is on the selection of more approximate values. So, in present study, performance of ageing factors for fly ash cement concrete (FACC) is checked. So, literature was surveyed and the long-term chloride diffusion coefficient (D) values were obtained for fly ash cement concrete (FACC). It was found that a significant difference is present in the predicted values with different available ageing factors. Since results obtained from modelling depend on the parameters, so it can be assumed that the variation of chloride diffusion coefficient (D) will vary the results. So, in present study, a new ageing factor was developed. Service life modelling for durability with fly ash cement concrete (FCC) may be relied on the newly developed ageing factors, as this will give better results, which will be more reliable.
通过添加粉煤灰等辅助胶凝材料可提高混凝土的耐久性。在波特兰水泥中添加粉煤灰制成的混凝土称为粉煤灰水泥混凝土（FACC）。一般来说，采用建模方法来预测混凝土在侵蚀性环境中的服役时间。混凝土的大部分劣化发生在海洋环境中，这是由于混凝土暴露在氯化物中。使用寿命建模是使用扩散方程（式1）和扩散系数（D）方程（式2）进行的，为了得到随时间变化的扩散系数（D），使用老化因子进行分析。在建模阶段，由于该研究阶段在施工前很早就开始了，因此要检查混凝土的耐久性性能。同样，也要对现有结构进行使用寿命建模，以便获得失效时间。最近，2021年6月美国迈阿密大楼的倒塌事件提高了氯化物环境中钢筋混凝土结构（RCC）使用寿命建模（SLM）的重要性。因此，在这种环境下，人们对更可靠结果的需求更大。文献中存在许多老化因子，这就引出了一个问题，即哪个老化因子更合适。建模方法的性能取决于更合适值的选择。因此，在本研究中，对粉煤灰水泥混凝土（FACC）老化因子的性能进行了检查。为此，对文献进行了调研，并获得了粉煤灰水泥混凝土（FACC）的长期氯化物扩散系数（D）值。结果发现，不同的可用老化因子预测值存在显著差异。由于建模得到的结果取决于参数，因此可以假设氯化物扩散系数（D）的变化会使结果发生变化。因此，在本研究中，开发了一种新的老化因子。使用粉煤灰水泥混凝土（FCC）进行耐久性的使用寿命建模可以依赖新开发的老化因子，因为这将给出更好的结果，从而更可靠。
