Synergic effects of the substitution of Portland cement for water treatment plant sludge ash and ground limestone: Technical and economic evaluation. (20th March 2019)

• Record Type: Journal Article
• Authors: Hagemann, S.E.; Gastaldini, A.L.G.; Cocco, M.; Jahn, S.L.; Terra, L.M.
• Is Part Of: Journal of cleaner production. Volume 214(2019)
• Page Start: 916
• Page End: 926
• Publication Date: 2019-03-20
• Subjects: Eco-eficient -- Pozzolanic activity -- Water treatment plant sludge -- Limestone -- Compressive strength -- Response surface methodology; Factory and trade waste -- Management -- Periodicals; Manufactures -- Environmental aspects -- Periodicals; Déchets industriels -- Gestion -- Périodiques; Usines -- Aspect de l'environnement -- Périodiques; 628.5
• DOI: 10.1016/j.jclepro.2018.12.324
• Languages: English
• ISSNs: 0959-6526

Abstract

Abstract: The coupled use of calcined clay and ground limestone has been a promising alternative to partially replace Portland cement due to the synergic effects between these two additions. Therefore, substituting calcined clay with a material of similar chemical composition, such as water treatment plant sludge ash (WTPSA), yields several environmental advantages. In this study, the pozzolanic activity of WTPSA was evaluated by determining the strength activity index (SAI) and using the modified Chapelle method. Statistical analyses were used to define the best conditions for WTPSA calcination and grinding. Response Surface Method (RSM) was used to find the Portland cement substitution content by WTPSA and limestone that result in higher concrete compressive strength values. The results of the evaluation of pozzolan activity of WTPSA showed that this material has the potential of being used as pozzolan. The joint analysis of the results confirms that calcination at 700 °C, residence time of 1 h, and grinding time of 1 h were the best conditions for treating WTP sludge. The optimal WTPSA and limestone content found by the Response Surface Method (RSM) were validated experimentally. Ternary mixtures containing WTPSA and limestone resulted in higher compressive strength than binary mixtures and plain cement, which shows the synergistic effect between the two materials. For compressive strength levels between 45 and 60 MPa, the ternary mixture composed of 15% WTPSA +7.5% ground limestone reduced Portland cement consumption from 34.7 to 38.4%. Highlights: Water treatment sludge calcined replaces partially the portland cement. Statistical analysis defined the optimal percentages of substitution of Portland cement. Mixtures of calcined sludge and limestone provide greater economy of cement. Reduced consumption of Portland cement in concrete ranges from 26 to 38%.