Page 63 - New Trends in Green Construction

USAGE OF RECYCLED WATER IN A VENEZUELAN PREMIXED CONCRETE PLANT. TOWARDS THE CIRCULAR ECONOMY
Henry A. Blanco, Aura Navas.
Keywords: Ready-mix concrete, Recycled water, Compressive strength, Curing time, Sustainable development
1. Introduction
Nowadays the concept of Circular Economy, defined as a production and consumption model which implies sharing, renting, reuse and recycle the existent materials and products whenever possible, in order to create an added value; it backs and consolidates the movement that some companies have begun to the sustained development. The production of premixed concrete has promoted actions aimed to generate changes that allow framing among those objectives that lead to be compatible with the environment.
2. Materials and methods
Since 2016, a premixed concrete plant located in one of the main cities of Venezuela decided to set actions in its productive process that allows them to lead on the road of sustained development and with that assume the circular economy in the midterm. It began with one of its main raw material: the water used for mixing, by installing an infrastructure that allows reusing residual water originated in the washing of trucks, diminishing thus the usage of potable water, making it available to the neighbors who need this resource. Therefore, it also contributes to social responsibility. The use of potable and residual water were among the fist actions. In order to make later tests in fresh and hardened concrete, guaranteeing its quality and verifying the fulfillment, not only of the local standard quality rule, COVENIN 2385:2000, but also with the international requirements ASTM C 1602 and the BS EN 1008; in order to finally generate the associated procedures to this activity.
3. Results and conclusions
The characterization of recycled water, after filtration by cut stone and sedimentation, yields a density of 0,993 g/l, total solids of 2818 mg/l, chlorides 290 mg/l, sulfates 580 mg/l and alkalis of 272 mg/l NaO. The content of oil, fat and the presence of organic matter, in DQO, was relatively low, 22 mg/l and 15 mg/l respectively. All these values fulfill the requirements of water quality imposed by local and international regulations. The requirements of the forging and compression resistance were also satisfied. Using 100% of recycled water (most unfavorable case), the time of forging concrete was 5 h 33 minutes, and with potable water 5 h con 21 minutes, barely 12 minutes difference. On the other side, the resistance to compression was lower than 10%, the established
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requirement in the different regulations, being 352 kg/cm and 403 kg/cm , for a time of 7 y 28
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days of concrete with recycled water, comparing it with the 356 and 414 kg/cm , obtained by
concrete with potable water.
In order to employ recycled water in the production process, the concrete quality was verified. The process procedures used guarantee the zero download of residual water. The concrete plant achieved the goal and in doing so, obtained results in the circular economy model, on one of the
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New Trends in Green Construction