Implementation of waste management in ready mixed concrete plants
The methods that find application in ready-mixed concrete plants related to waste management and that are popularly mentioned are as follows:
Sedimentation Pool: In this method, the remaining concrete in the drum of the truck mixers and the boilers of the pumps is washed in such a way that it empties into the settling pools, and the washing water containing solid material is collected in the pools. The solids in the polluted water collected in the pools precipitate over time and the water purified from the waste materials remaining in the pool can be taken to another pool and given to the sewer after the improvement (after the pH value is balanced) or used directly in production. The solid waste precipitated in the pools is collected in the waste drying area and after drying there, it is sent to the appropriate waste collection area by appropriate methods.
Cleaning with Aggregate: In this method, 2 tons of coarse aggregate and 0.2 m3 (200 lt) water are put into the drum to clean the concrete remaining on the blades of the truck mixer drum and the mixing process is started. After the mixing process is completed, the waste material is either discharged to the stock area or kept in the drum. The required amount of aggregate, cement and water is added to this stored aggregate for the next shipment, and the desired quality concrete is produced and shipped. It is the easiest and cheapest method in waste management. However, it cannot provide a suitable solution for the returned excess amount of concrete. In addition, it is necessary to carefully monitor each vehicle and keep a record of the material waiting in it. Otherwise, the amount of aggregate and water to be added cannot be determined exactly and concrete of the desired quality cannot be produced.
Washing with Chemicals: Additives are used for hydration control in this technique, which has been used more recently. This additive acts as an anti-reaction barrier around the cement in the vehicles to which it is added. Thus, a drum with added additives can be cleaned with only 300 liters of water at the end of the day. In addition, this water is included in the concrete production by reducing the water to be added to the vehicle in the first production the next day by the same amount. The downside of the system is that it is costly and cannot be used before a small amount of production. The positive aspects are that it reduces environmental problems and saves time due to cleaning by using less washing water. Although operating costs are high in this system, there is no initial investment cost as it does not require any infrastructure and equipment.
Recyclers: It is the system used for the recovery of the aggregate of fresh concrete. The operating logic of the system is very simple, it is based on the principle of washing the excess or excess concrete with water before it hardens (without setting it). In general, the recycling units used in practice work with the same logic. However, companies make design changes under different brands and different patents.
Recycling Water: Washing water can be collected in settling pools and released to nature as a result of pH balancing. However, this situation only reduces the damage to the nature of the water used, and does not mean that the limited natural resources are used efficiently. For this reason, using the water collected in the pools in production or in processes such as car washing reduces water waste. In addition, by ensuring that the floors of the facilities are concrete and the slope of the ground is towards the settling pools, snow and rain water that will fall on the field can be used in production or only for vehicle and field washing depending on its chemical structure.
