Ceramics-Silikáty 68, (2) 225 - 233 (2024)

The article analyses the effect of cellulose fiber on the properties and structure of hardened cement paste. Nine batches of concrete were mixed: one batch for the control sample without cellulose fiber, and eight batches with cellulose fiber introduced at the rate from 0.25% to 2 %. The modification of hardened cement pastes with cellulose fiber showed that the addition of cellulose fiber at 2 % caused a 5.4% drop in the heat of hydration, which increases the workability of concrete mix and has a positive effect on concrete manufacturing. The cellulose fiber obtained from waste paper has a positive effect on the microstructure of hardened cement paste as it bonds well to the cement matrix in mortars containing 1 % of cellulose fiber. The flexural strength of hardened cement paste was found to increase with higher cellulose fiber content. The control sample without cellulose fiber had the flexural strength of 3.24 MPa and the sample modified with 2% of cellulose fiber had the flexural strength of 6.89 MPa, which is more than twice the value of the control sample. Thus, cellulose fiber can be added up to 1 % in the production of modified concrete products subjected to flexural force during operation.