of Hengshui City on Further Strengthening the Maintenance of Cast-in-place Concrete at the Construction Site (Draft for Soliciting Opinions)
All county (city, district) housing and construction bureaus, all construction, construction and supervision units:
To standardize the maintenance of cast-in-place concrete, implement the responsibilities of the responsible subjects, ensure the quality and safety of the engineering structure, and prevent and reduce concrete cracks, the relevant matters are hereby notified as follows.
1. Improve the management system and strictly examine and approve
the preparation of maintenance plans (1) All relevant units should improve the management system of concrete maintenance. Strictly implement the requirements of General Code for Concrete Structures (GB55008-2021), Code for Construction of Concrete Structures (GB50666-2011) and other codes and standards, and the construction unit shall prepare the concrete curing plan according to the actual situation of the project. The scheme shall specify the specific curing method, curing time and curing measures for each part of the structure, and meet the requirements of the standard specification. For horizontal members such as beams and slabs, it is required that the concrete shall be covered with felt immediately after final setting and watered for curing; for vertical members such as walls and columns, it is required that each member shall be covered with felt immediately after formwork removal and watered for curing. The maintenance scheme shall be implemented after being approved by the supervisor.
(2) The supervision unit shall do a good job in the inspection of concrete maintenance, check the whole process of concrete maintenance in accordance with relevant regulations and standards, and ensure the implementation of maintenance time and measures.
2. Implement standards and specifications and implement technical safeguard measures
(1) For the poured concrete, the curing work shall be carried out in time after the initial setting and final setting of the concrete. The construction unit shall implement the concrete curing measures according to the curing scheme, and the curing water shall meet the requirements. The curing standard is that the felt is always wet during the curing period.
(2) Concrete mixed with Portland cement, ordinary Portland cement or Portland slag cement shall be watered and cured for not less than 7 days; Concrete mixed with retarding admixture or large amount of mineral admixture (the amount of fly ash or mineral powder accounts for not less than 30% of the total amount of cementitious materials, and the total amount of fly ash and mineral powder accounts for not less than 40% of the total amount of cementitious materials) shall not be less than 14 days.
(III) The curing time of concrete with formwork for columns and walls on the ground floor of basement and the first floor of superstructure shall not be less than 3 days. After the curing with formwork, the concrete shall be covered and watered until the curing time specified in the specification.
(IV) For concrete constructed in winter, when the average temperature of the day is lower than 5 ℃, the method of watering curing shall not be used, and the concrete shall be covered with felt for closed thermal insulation curing measures; When the outdoor minimum temperature is not lower than -15 ℃, the critical freezing strength of concrete constructed by comprehensive heat storage method and negative temperature curing method shall not be lower than 4.0 Mpa. When the outdoor temperature is not lower than -30 ℃, the critical freezing strength of concrete constructed by negative temperature curing method shall not be lower than 5.0 Mpa. After formwork removal, the concrete surface shall be covered with felt for thermal insulation immediately.
3. To strengthen the supervision
of concrete maintenance, the quality supervision departments should strengthen the supervision and inspection of concrete maintenance quality, and order the relevant units to rectify those who violate the relevant national and provincial engineering construction standards and cause the inadequate implementation of concrete maintenance measures. If the physical strength of structural components fails to meet the design requirements due to inadequate concrete curing and other factors, it shall be handled strictly in accordance with the relevant specifications and standards, and the relevant responsible persons shall be held accountable and notified. According to
the Implementation Plan of Carbon Peak in Building Materials Industry, the comprehensive energy consumption per unit product of cement clinker will be reduced by more than 3% during the 14th Five-Year Plan period, and key industries such as cement will be included in the national carbon emission trading market. It is urgent for cement enterprises to establish carbon emission management system and improve the ability of carbon asset management.
To this end, China Cement Network will hold the "2023 Cement'Double Carbon 'Conference and the 10th China Cement Energy Conservation and Environmental Protection Technology Exchange Conference" in Zhengzhou, Henan Province, to help the cement industry move towards a lower carbon, more energy-saving and greener high-quality development.
After the meeting, we will also organize a visit to Jiyuan Zhonglian Cement Co., Ltd. "The world's first production line of carbon sequestration auxiliary cementitious materials and low-carbon cement from flue gas CO2 of steel slag capture cement kiln".
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