Abstract：To explore the influence of pore structure of nano-SiO2 fly ash concrete on compressive strength, the content of nano-SiO2 additional rate 1%, 3%, 5% and 7% and fly ash additional rate 10%, 20% and 30%, respectively, the water to binder ratio was 0.35, and the two are mixed together for the test. Determine the cube microstructure compressive strength 3 d, 7 d and 28 d. The pore structure and micro morphology were comprehensively analyzed and studied by nuclear magnetic resonance technology, field emission scanning electron microscope and differential thermal gravimetric technology. The primary and secondary factors affecting the compressive strength of concrete are found out by gray correlation entropy analysis, and the GM(1, 4)gray prediction model is established. The results show that the nano-SiO2 and fly ash can promote the hydration of concrete, and improve the early compressive strength of concrete, meanwhile its optimal mix proportion when the mass fraction of fly ash and nano-SiO2 are 20% and 3%. The main factors affecting the compressive strength are(0,0.01］μm pore size ratio,(0.01,0.10］μm pore size ratio and bound fluid saturation to establish a GM(1, 4)gray model. The average relative errors between the predicted values of 3, 7 and 28 day and the experimental values are 3.28%, 4.00% and 2.64%, respectively. Using the pore structure to predict the compressive strength of concrete has better accuracy. This study can provide reference for the application of nano-SiO2 and fly ash in concrete engineering.
