In order to explore the pore structure characteristics of phase change energy storage backfill and their influence on the strength deterioration of backfill

a composite phase change material was prepared with butyl stearate as the phase change material and expanded perlite as the adsorption medium. Cement and tailings were mixed to prepare backfills with different additive amounts of the composite phase change material. The strength and structure characteristics of the phase change energy storage backfill with different addition amounts were obtained by using the methods of CT (computer tomography) scanning

MRI (magnetic resonance imaging) analysis

and uniaxial compression test

and the influence mechanism was analyzed. The results show that: i) The porosity of phase change energy storage backfill increases gradually with the increase of the addition amount. The macropore porosity increases approximately linearly

the proportion of macorepores increases gradually

and the pores approximate to sphere. ii) With the increase of the amount of phase change material

the connectivity of the backfill increases

the pore throat length increases

and the number of macropores increases. The pore throat coordination number is concentrated below 5

and the fractal dimension decreases first and then increases significantly

resulting in complex pore distribution. iii) With 5% additive amount

the uniaxial compressive strength of backfill decreases by 30.2% due to the increase of macropores and pore connectivity. With 10% additive amount

the pore size distribution becomes uniform and the uniaxial compressive strength decreases by 48.9%.