Semnan University Press Journal of Rehabilitation in Civil Engineering 2345-4415 6 2 2018 08 01 Prediction of Lightweight Aggregate Concrete Compressive Strength 154 163 2641 10.22075/jrce.2017.11556.1192 EN Omid Fatahi M.Sc., Discipline of Civil Engineering, Islamic Azad University, Eyvan-e-Gharb Branch, Eyvan, Iran Saeed Jafari M.Sc., Department of Civil and Environmental Engineering, Shiraz University of Technology, Shiraz, Iran Journal Article 2017 06 07 Nowadays, the better performance of lightweight structures during earthquake has resulted in using lightweight concrete more than ever. However, determining the compressive strength of concrete used in these structures during their service through a none-destructive test is a popular and useful method. One of the most original approach of non-destructive testing to obtain of compressive strength of concrete used in structures is ultrasonic pulse velocity test. The purpose of this research is predicting the compressive strength of LWA concrete by proposing an accurate mathematical formulation. Many samples of lightweight aggregate concrete, made by expanded clay, have been produced and tested. After determining the actual compressive strength and indirect ultrasonic pulse velocity for each sample, a relationship was derived to estimate the compressive strength through Gene Expression Programming (GEP). The results show the presented equation shows high accuracy in predicting the compressive strength of LWA and the estimated outcomes have a considerable compatibility with actual samples. https://civiljournal.semnan.ac.ir/article_2641_67001b6a3ff2346d04f57e657192e70a.pdf