AbstractBiobased green plasticizers are preferred in the production of plastics in light of the environmental and human health issues posed by traditional plasticizers. Epoxidized soybean oil is an environmentally friendly admixture that is a significant alternative for biobased polymer concrete rather than petroleum-derived products such as polyethylene terephthalate, rubber, and polyvinylchloride. This study aims to determine the effect of epoxidized soybean oil additives on cement paste properties, and to compare the effects of epoxidized soybean oil and dioctyl terephthalate on cement paste properties. With the addition of 10% epoxidized soybean oil to cement paste, electrical resistance was 1.91 times higher, and thermal resistance was 1.70 times higher, than the control sample, while water absorption and porosity decreased by 65%±4.0%. Compared to dioctyl terephthalate-impregnated cement pastes, epoxidized soybean oil cement pastes have higher values for calcium hydroxide content and ultrasonic pulse velocity (91%±0.3% and 182%±2.0%, respectively), and lower values for porosity and thermal conductivity (30%±3.0% and 16%±0.1%, respectively). Moreover, epoxidized soybean oil can form three times more hydrogen bonds than dioctyl terephthalate, which allows for the formation of less porous and more compact cement pastes.