Editor's note: my country's industry standard JGJ 104-2011 "Winter Construction Regulations for Construction Projects" stipulates that when the outdoor daily average temperature is stably below 5℃ for 5 consecutive days, winter construction conditions are met. . Under these conditions, if appropriate measures are not taken during the production and construction of concrete, quality problems such as expansion cracks and strength reduction will easily occur. So what should we pay attention to in winter concrete production and construction? Do all projects under winter construction need to prepare for winter construction? This special issue invites everyone to discuss common misunderstandings and key points about concrete production and construction in winter.
In winter concrete construction, Beijing has vigorously promoted and improved the comprehensive heat storage method, and the temperature in the three northern regions of the country (Northeast, North China, and Northwest China) is suitable It has been widely promoted and applied in many areas. One of the keys to this method is the use of antifreeze. The climate is cold in winter, and antifreeze and comprehensive heat storage methods are used to adapt to concrete construction under subzero temperature conditions. In the past, during on-site construction in winter, small slump was used to achieve early setting and early strength in order to keep the concrete from freezing damage under negative temperature conditions. However, with the advancement of construction technology and the extensive application of concrete antifreeze pumping agents, The demand for high-slump pumped technical concrete is growing rapidly. Due to the large water-to-cement ratio and large capillary voids, thick water films and porous migration zones will be formed at the bottom of the aggregate, which are the weak links for concrete to be damaged by freezing. The addition of antifreeze is mainly to improve the interface structure of negative temperature concrete, relieve the frost heave pressure in the transition zone, and promote the hydration of negative temperature cement and the formation of early structure. Due to cost pressure or restrictions on floor materials, commercial concrete companies have suffered from problems caused by failure to follow JGJ 104-2011 "Winter Construction Regulations for Construction Projects" during on-site construction in terms of the selection of concrete raw materials, mix ratio design and other factors. The emergence of freezing damage has led to engineering quality problems and hidden quality hazards, which have also been on the rise in recent years.
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