Usage of ready-mixed concrete plant wastewater in concrete with superplasticizer: Effect on physico-mechanical properties

Abstract

• As the WW content increased, the temperature of the concrete mixtures increased. • The workability of the mixtures is improved at the maximum usage dosage of SP (at 2%). • The air content of fresh concrete is between 2.1% and 2.5%. • The 28-day compressive strength of concrete mixes varies between 37.1 and 41.3 MPa. • The use of washing water on all test days decreased the compressive strength. The rapid growth of population and industrialization increases the demand for concrete day by day. In concrete production, a high amount of waste washing water is released. This waste washing water that is released causes soil and water pollution. This study investigated the fresh and physico-mechanical properties of the concretes prepared with the washing water released in the ready-mixed concrete plants. Wastewater (WW) was used at the rate of 25, 50, 75 and 100 % instead of potable water (PW). In addition, the mixtures used a naphthalene-sulfonate-based superplasticizer (1, 1.5 and 2 %). The effectiveness of SP in concrete produced with WW was also investigated. WW workability was relatively improved in mixtures without SP. However, to increase the workability in mixtures using 100 % WW, the SP dosage should be 2 %. The unit weight of fresh concrete is more than 2300 kg/m 3 . WW ratio and SP dosage did not greatly affect the unit weight of fresh concretes. Increasing the SP dosage decreased the air content of the fresh concrete, while the air content increased as the WW ratio increased. In mixtures with WW, the air content decreased by 20 % when the SP dosage was 2 %. The 28-day compressive strength of concrete varies between 36.9 and 49.00 MPa. It has been determined that C30/37 class concrete can be produced with 100 % WW mixtures. The 28-day compressive strength of the mixtures using 100 % WW decreased by 10 % compared to the reference mixture. As a result, the demand for water or SP increases in concretes using WW. Therefore, approximately 40 MPa compressive strength was obtained in WW concrete produced using SP. By producing concrete using WW, environmental pollution will be greatly reduced.