To investigate the quantitative relationship between pore distribution characteristics and the compressive strength of medium-to-high strength concrete,we conducted comprehensive compressive strength tests by using a low-field nuclear magnetic resonance(NMR)imaging analysis system in conjunction with a fully automatic pressure testing machine.By validating and modifying the Ryshkewitch semi-empirical equation model,we established the quantitative relationship model between pore distribution characteristics and compressive strength.Test results dem-onstrate several key findings.First,an increase in sand rate and initial entrapped air content of concrete leads to a gradual increase in porosity.Increasing the initial air content proves to be more effective in generating a more varia-ble porosity compared to increasing the sand rate.Specifically,by increasing the sand rate,the percentage of non-capillary pores increases by 17.2％while the percentage of capillary pores decreases by 13.0％.On the other hand,increasing the initial air content results in a 12.7％increase in capillary pores and a 12.6％decrease in gel pores.By employing the model based on modified Ryshkewitch semi-empirical equation,we achieved accurate results with an R2 value close to 1 and a P-value less than 0.05,effectively describing the quantitative relationship between pore distribution characteristics and compressive strength.
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