Study of the Effects of the Addition of Fly Ash from Carwash Sludge in Lime and Cement Pastes

María C Rodríguez-Fernández,Juan D Alonso,Juan F Saldarriaga,Carolina Montero

doi:10.3390/su12166451

María C Rodríguez-Fernández, Juan D Alonso + Show 2 more

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https://doi.org/10.3390/su12166451

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Abstract

Sludge from carwash wastewater treatment plants has been evaluated as substitute for lime paste, as well as its behavior in cement mortars. Dry sludge waste was used with (CSlud) and without (USlud) pretreatment and have been characterized. The pastes were prepared with weight replacement of 5, 10, 15, and 20% of sludge. The formation of calcium silicate hydrate was determined by TGA, both in lime and cement pastes. The compressive strength properties were evaluated in mortars. It was found the mixtures which present the best results were those of 5 and 10% for USlud, and 10 and 20% for CSlud.

Highlights

The carwash industry requires high amount of fresh water to effectively remove pollutants
This paper presents a study of the use of carwash sludge as a replacement in lime pastes, through reactivity at different curing ages
Its properties and viability have been identified as cement substitutes in at least 5% with not calcined sludge and at least 10% with calcined sludge, giving them a specific use as an additive in the manufacture of low-performance inputs in construction and complying with the technical standards required for it

Summary

Introduction

The carwash industry requires high amount of fresh water to effectively remove pollutants. It is estimated that an average of 150–600 l of wastewater are generated for each washing process, depending on the car washing facilities and the size of the car [1,2]. The most common treatment for this type of waste is incineration, which is used due to the high content of pollutant present in the wastewater sludge. The main product of the combustion process is fly ash, which is estimated to be 80% of the total ash produced. The properties of fly ash can vary and differ greatly on combustion method, raw material origin, type of emission control systems, particle size, and storage methods, among others [11,12,13,14]. Its fine texture and its high chemical reactivity favors reactions with other compounds that may be present in the medium and some authors have shown that these can contaminate the soils and groundwater by leachates produced by their inadequate disposal [15,16,17]

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