Processed wastewater sludge for improvement of mechanical properties of concretes

• Published in: Journal of hazardous materials Vol. 192; no. 1; pp. 108 - 115
• Main Authors: Barrera-Díaz, Carlos, Martínez-Barrera, Gonzalo, Gencel, Osman, Bernal-Martínez, Lina A., Brostow, Witold
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 15.08.2011; Elsevier
• Subjects: aluminum sulfate; Applied sciences; cement; coagulants; Compression properties; Compressive properties; Compressive strength; Concrete; Concretes; Construction Materials; Electrochemistry; Electrocoagulation; Exact sciences and technology; ferrous sulfate; General purification processes; long term effects; Materials Testing; mechanical properties; modulus of elasticity; Pollution; Sand; scanning electron microscopy; Sewage; silica; Sludge; Strain; Waste water; wastewater; Wastewater treatment; Wastewaters; Water Pollutants; Water treatment and pollution; Yield point; Concrete; Electrocoagulation; Compression properties; Wastewater treatment; Construction materials; Scanning electron microscopy; Compression; Electrochemical treatment; Iron II; Mechanical properties; Compressive strength; Sulfates; Long term; Waste water; Flocculation reagent; Flocculation; Cement; pH; Physicochemical purification; Aggregate; Waste water purification
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2011.04.103

► Electrochemical methods produce less amount of residual sludge as compared with chemical procedures. ► Wastewater sludge contains a large amount of water. ► The residual sludge is used to prepare cylinder specimen concrete. ► There are improvements in the elastic modulus of the concrete when is prepared with residual sludge. Two problems are addressed simultaneously. One is the utilisation of sludge from the treatment of wastewater. The other is the modification of the mechanical properties of concrete. The sludge was subjected to two series of treatments. In one series, coagulants were used, including ferrous sulphate, aluminium sulphate or aluminium polyhydroxychloride. In the other series, an electrochemical treatment was applied with several starting values of pH. Then, concretes consisting of a cement matrix, silica sand, marble and one of the sludges were developed. Specimens without sludge were prepared for comparison. Curing times and aggregate concentrations were varied. The compressive strength, compressive strain at yield point, and static and dynamic elastic moduli were determined. Diagrams of the compressive strength and compressive strain at the yield point as a function of time passed through the minima as a function of time for concretes containing sludge; therefore, the presence of sludge has beneficial effects on the long term properties. Some morphological changes caused by the presence of sludge are seen in scanning electron microscopy. A way of utilising sludge is thus provided together with a way to improve the compressive strain at yield point of concrete.