Key points of measures to prevent or mitigate adverse environmental impacts of polycarboxylate water-reducing agents

As the third high-performance water-reducing agent successfully developed and produced after naphthalene series, melamine series, aliphatic series and sulfamate series, polycarboxylic acid-based water-reducing agent has the characteristics of low dosage, high water-reducing rate, It has the characteristics of good slump retention performance, strong adaptability to cement, and small shrinkage of concrete.

(1) Waste gas: The non-methane total hydrocarbon organic waste gas volatilized by the reactor is absorbed by a liquid sealing tank (aqueous solution) and then passed through The activated carbon is adsorbed and then discharged through a 15m high exhaust pipe. In addition, workshop ventilation is strengthened to reduce the impact of unorganized organic waste gas emissions on the surrounding atmospheric environment.

(2) Wastewater: circulating cooling water, liquid seal box wastewater, equipment flushing water and other wastewater are reused in production; workshop floor flushing wastewater and domestic sewage are treated by wastewater treatment facilities and then discharged into the industrial park for sewage treatment It is treated in a factory and has little impact on the water environment.

(3) Noise: Each equipment is planned to be reduced by measures such as shock-absorbing installation and sound insulation, and the factory building will be able to meet the requirements of acoustic environment standards after sound insulation.

(4) Solid waste: Waste activated carbon, toxic and harmful raw materials, waste packaging and other hazardous waste generated during the production process are recycled and disposed by the manufacturer. The rest of the general industrial solid waste is sold outside, and domestic waste is stored at designated points in the factory. It will then be collected and disposed of by the environmental sanitation department. All types of solid waste from the project have been effectively treated and disposed of.

Slump control

Precast box beams have high requirements for appearance. Therefore, the stability of concrete quality, especially the stability and uniformity of slump, is important for reducing water content. Defects such as lines, cloud spots, color difference and even holes and excessive laitance play an important role.

　1. Reason analysis:

　(1) The dosage of polycarboxylic acid admixture is small, the water reduction rate is high, and the production is extremely sensitive to water consumption. When the water consumption fluctuates, increasing or decreasing by 3 to 5kg, the slump changes significantly, with slight bleeding or no expansion.

(2) There are errors in measurement, overmixing occurs, and the slump of concrete out of the machine is too large. After mixing and transportation, it is slightly segregated when it arrives at the construction site. When testing its basic performance, there is leakage. Water and hardening and other phenomena. As the concrete used for testing, it is difficult to vibrate during pouring and the upper part is seriously hardened. When removing the formwork, there was mold sticking. There were obvious water marks on the bottom of the test box beams, and there was honeycombing on the inner sides, and the appearance was poor.

2. Preventive measures:

(1) Increase the frequency of testing of aggregate moisture content to ensure accurate production water consumption. It is recommended that the sand moisture content be measured during each working shift or during continuous supply. Measure once every two hours and increase the frequency to ensure the accuracy of water consumption; for stones, it is best to dry screen directly. In the early stage of supply, in order to ensure the quality of the stones, we washed the stones 2 to 3 times with water and stored them for a week to dry. However, during the actual production process, the outside of the large pile of stones was dry but the inside was still wet, and the water content in different layers was uneven. The stability of slump has a greater impact. Later, it was changed to direct dry screening, and the effect was better;

(2) Machine operators were not given the authority to adjust the water consumption;

(3) The mixing time was extended to ensure the uniformity of mixing;

(4) Communicate and coordinate with the admixture manufacturers to increase the admixture dosage from the designed 1.2% to 2.0% to reduce the relative error and reduce the measurement sensitivity;

( 5) Upgrade the management software of the production control system and replace sensors to ensure measurement accuracy. </p