Reuse of Waste Material “Waste Sludge Water” from a Concrete Plant in Cement Composites: A Case Study

Abstract

Featured Application: The results of the research indicate the possible useing of waste sludge water directly in the concrete plant where they are produced. It will reduce waste generation and reduction of payments for their liquidation.Abstract: This paper presents the results of research dealing with the use of recycled waste sludge water from a concrete plant (CP) as partial or complete replacement of mixing water in cement mixtures. The need to recycle waste sludge water generated as a by-product (waste sludge water) during the production of fresh concrete in the concrete plant results from the environmental and economic problems associated with the operation of the concrete plant. Mixing water was replaced with recycled waste sludge water in the amount of 25%, 50%, 75%, and 100%. In order to determine the effect of partial or complete replacement of mixing water with waste sludge water from the concrete plant in the production of cement composites, laboratory tests of waste sludge water were carried out to determine whether the waste sludge water complies with the requirements for mixing water defined in CSN EN 1008. The tests also determined the properties of fresh cement mortar and hardened cement composites. These were tests of the beginning and end of cement mortar setting, and the strength characteristics (flexural strength, compressive strength). The results of these tests show that it is possible to replace the mixing water by waste sludge water from the concrete plant in the amount of up to 25% without significantly affecting the tested properties, in comparison with the formula containing pure mixing water.Appl. Sci. 2019, 9, 4519 2 of 12 water-cement ratio for proper hydration, as shown by the studies [5][6][7][8]. Knowing the interactions of the individual components of cement composites, the desired properties of the resulting composites can be achieved. The knowledge of interactions does not only apply to waste mixing water, but can also be applied to other waste products, as suggested by the studies [9][10][11]. In fact, it is estimated that a truck with the volume of 9 m 3 carries approximately 300 kg of returned concrete a day. This remaining concrete is generally discharged into large containers and, after hardening, the concrete can be crushed and used as recycled aggregate for further construction. After emptying the rest of fresh concrete, the agitation truck is washed with large amount of water, 700-1300 litres per truck, and the scattered mass settles in large sedimentation tanks [12,13]. Due to the large amount of suspended substances and high alkaline conditions, untreated sludge water cannot be legally discharged into municipal sewer systems [1]. Water is an important component of concrete. It participates in the hydration of cement, but also contributes to the workability of fresh concrete. The quality of mixing water is therefore crucial for the properties of fresh concrete, including the strength and durability. Most standards specify that water used as mixing water must be clean ...

A proposed method and monitoring system for evaluating workability of Portland cement concrete during mixing

“…Because the stirring power is related to the relative movement speed of the material, the yield shear stress, cohesive force and other factors [ 28 ], and the hydration reaction occurs during the mixing process, changes in the mechanical properties of concrete can affect the workability of fresh concrete [ 29 ]. Therefore, the stirring power consumed during mixing is an important indicator of workability, and the mixing process can be divided into four stages as following:…”

Treatment of Mixer Truck Wash Water of a Ready-mix Concrete Batching Plant Using a Low Cost Modified Sand Filter

“…When using water with TDS 15,000 ppm produce compressive strength lower than control but still meet the requirement by ASTM C191-18a. This may be due to pore filling properties of TDS (Aldossary et al, 2020, Zervaki et al, 2013, Vaičiukynienė et al, 2021, which produced higher compressive strength at 3 and 7 days, but about 92% of control (de Matos et al, 2020), higher than control before three months old and similar to control thereafter (Gupta et al, 2020, Klus et al, 2019. Other properties such as workability, initial setting time were reduced but still within the acceptable limit, which may be due to the presence of Cl ion in TDS (Aldossary et al, 2020, Zervaki et al, 2013, Bouaich et al, 2021.…”