The impact of paper sludge waste on physical & mechanical properties of cementitious materials

Abstract

The global production of paper is on the rise, thus leading to increasing amounts of waste in different stages of paper manufacture. Paper sludge waste is the most abundant and there is a big potential to reuse it after appropriate processing. This research paper analyses paper sludge waste fired at 900°C temperature for 2 h in terms of mineral composition, particle density and water demand in cement-based mixtures, as well as the effect of paper sludge waste on the density, ultrasonic pulse velocity, compressive strength and mineral composition of cement-based specimens. In the cement paste mixtures 0%, 2.5%, 5%, 7.5% and 10% of cement was replaced with paper sludge waste fired at 900°C temperature for 2 h. The ratio between water and solid substances was 0.35. Gehlenite and calcium oxide were found to prevail in the mineral composition of paper sludge waste, whereas water demand of cement-based mixture incorporating paper sludge waste was 30%. The intensity of XRD curves revealed that a higher content (more than 5%) of paper sludge waste fired at 900° C temperature for 2 h in the mix increases the amount of portlandite and reduces the amounts of cement minerals: alite and belite. An empirical equation was drawn on the grounds of statistical analysis to calculate the compressive strength according paper sludge waste content fired at 900°C temperature for 2 h. The correlation and determination factors more than 0.9 demonstrate that the change of compressive strength in relation to paper sludge waste content can be described by the second-degree polynomial equation and the optimum content of paper sludge waste fired at 900°C temperature for 2 h in the cement matrix is 5%. The highest density and ultrasonic pulse velocity values of cement stone specimens after 28 days of curing were obtained of specimens containing 5% paper sludge waste