Temperature Influence on Ordinary Concrete Modified with Fly Ashes from Thermally Conversed Municipal Sewage Sludge Strength Parameters

Abstract

Concrete is the most commonly used structural material, without which modern construction could not function. It is a material with a high potential to adapt to specific operating conditions. The use of this potential is made by its material modification. The aim of the performed investigations was the assessment of rational application possibilities of fly ashes from thermally conversed municipal sewage sludge as an alternative concrete admixture. A concrete mix was designed, based on the Portland cement CEM I 42.5R and containing various quantity of ash, amounting to 0–25% of cement mass. The samples were conditioned and heated in a furnace at the temperature of 300 °C, 500 °C, and 700 °C. Physical and chemical properties of the ashes as well as utility properties of the concrete, i.e., density, compressive strength after 28, 56, and 90 days of maturation, frost resistance, and compressive strength in high temperature were determined. The tests were performed at cubic samples with 10 cm edge. The replacement of a determined cement quantity by the fly ashes enables obtaining a concrete composite having good strength parameters. The concrete modified by the fly ashes constituting 20% of the cement mass achieved its average compressive strength after 28 days of maturation equal to 50.12 MPa, after 56 days 50.61 MPa and after 90 days 50.80 MPa. The temperature growth weakens the composite structure. The obtained results confirm the possibility of waste recycling in the form of fly ashes as a cement substitute in concrete manufacturing.

Fly Ash from Thermal Conversion of Sludge as a Cement Substitute in Concrete Manufacturing

“…It is quite confusing that the density of the concrete mixes with the additive is higher than that of the reference concrete, despite the higher air content of the mixes with the additive. This result is confirmed in another publication [52] describing investigations conducted by the authors and concerning application of the fly ashes from thermal conversion of sewage sludge. However, this phenomenon requires further investigations in an aim to explain its nature and reasons.…”

“…The fly ash from thermal conversion of sewage sludge used as a substitute for cement in quantities of up to 20% results in an increase in strength if compared to the reference concrete without the addition, see Figure 6. The investigations conducted by the authors [29,30,52,53] and concerning the impact of the fly ash from thermal conversion of sewage sludge on strength compression in different maturation periods confirms the positive effect of this type of ash [29,30,52,53]. When assessing the chemical composition of the used ash [30], it was observed that for the ash obtained from the "Czajka" sewage treatment plant in Warsaw, the values of compressive strength were lower than for the concrete with the ash from the sewage treatment plant in Cracow.…”

The Use of Modal Analysis in Addition Percentage Differentiation, and Mechanical Properties of Ordinary Concretes with the Addition of Fly Ash from Sewage Sludge

“…In addition, it was observed that the reference concrete showed a lower compressive strength than the FA20% samples by a value equal to 18.8% after one year of maturation. Our own experimental research conducted on the influence of fly ash from the thermal transformation of sewage sludge on the compressive strength in different maturation periods confirms the positive influence of this type of ash [ 25 , 26 , 27 ].…”

“…X’Pert Highscore software (Panalytical, Eindhoven, Netherlands) was used for processing the diffraction data. The identification of the mineral phases was based on the PDF-2 release 2010 database formalized by JCPDS-ICDD [ 7 , 27 , 49 ].…”

“…The research on fly ash from the thermal treatment of sewage sludge presented in the literature proves that the introduction of a certain amount of SSA into the concrete mix does not adversely affect the strength parameters and frost resistance of mortars and concretes. Fly ash is treated as a partial binder replacement or as a mineral additive [ 24 , 25 , 26 , 27 ]. In studies conducted by Monzo et al [ 28 ], it was shown that mortars containing up to 30% SSA and that were cured in water at a temperature of 40 °C do not show a reduction in compressive strength compared to with the addition of ash.…”