Problems to be prevented and noticed in mortar construction in winter

Shandong chuangyao Biotechnology Co., Ltd. reminds: the functional orientation of mortar in construction engineering determines its characteristics of large construction area and thin construction thickness. Mortar in buildings is not as large and concentrated as concrete. Therefore, it is difficult to effectively protect the thermal insulation of the mortar after construction in winter construction. The mortar after construction is easy to be frozen, resulting in a series of problems, such as pulverization, falling off, etc. How to make the mortar strength reach the design requirements after hardening under the condition of negative temperature, what kind of protection and anti freezing measures should be taken in the construction process? We must pay attention to the winter construction.

Sign of entering winter construction period

According to JGJ / T 104-2011 and code for acceptance of construction quality of masonry engineering gb50203-2015, when the temperature condition of construction site reaches the following conditions, it is deemed to enter the winter construction period:

1. When the outdoor daily average temperature is stable below 5 ° C for 5 consecutive days, masonry works shall be constructed in winter.

2. Beyond the winter construction period, if the minimum temperature of the day is lower than 0 ° C, winter construction shall also be adopted.

Antifreeze mortar

1. Frost resistance and antifreeze of mortar

Frost resistance of mortar refers to the ability of mortar to resist strength and quality loss after years of cold and hot alternation in winter and summer. In the laboratory, it can simulate the cold and hot changes of the actual use environment, freeze under the negative temperature, dissolve under the positive temperature, and test the strength and quality loss rate of mortar through multiple cycles of freeze-thaw, so as to judge the frost resistance of mortar. According to the standard requirements, different regions have different freeze-thaw cycles. Jinan is a hot summer and cold winter area, the frost resistance freeze-thaw cycle coefficient of mortar is 25 times, the strength loss rate is ≤ 25%, and the quality loss rate is ≤ 5%.

The frost resistance of mortar refers to the frost resistance of mortar mixture which can resist the influence of negative temperature and harden when it is constructed in winter. After being cured under positive temperature condition, the strength continues to increase to meet the design requirements. The frost resistance of mortar is limited and conditional. In Jinan and its surrounding areas, the lowest temperature in winter is generally - 5 ~ - 10 ° C, and the lowest temperature for most plastering and masonry construction is - 5 ° C. if it is cold again, the construction will not be carried out.

2. Formula design of antifreeze mortar:

In terms of relevant standards or regulations, there is no strict standard for antifreeze mortar, and the formulation design of antifreeze mortar is more based on the actual construction, to adjust the relevant performance of mortar, such as: adjust the setting time, before the temperature of mortar mixture drops to 4 ° C, the cement can start to hydrate; improve the strength of mortar used in winter, so that the strength of mortar hardening body will be negative Under the influence of temperature, the final strength can still meet the requirements of architectural design; add mortar antifreeze, so that the mortar can be hardened at negative temperature and meet the design strength requirements of mortar at subsequent positive temperature.

Before the popularization of premixed mortar, in winter construction, the most common method is to mix salt in the mortar field. In recent years, some manufacturers have compounded mortar antifreeze on the basis of concrete antifreeze.

3、 Anti freezing performance verification of anti freezing mortar:

As mentioned above, there is no strict standard for frost proof performance of mortar. The only standards we can refer to are "cement mortar antifreeze" and relevant strength ratio standards specified by the concrete industry. According to the test standard of cement mortar antifreeze, the antifreeze of mortar (minimum temperature is - 5 ° C) shall meet the following standards in strength: R-7 ≥ 10%; R28 ≥ 100%; R-7 + 28 ≥ 90%. In addition, the test block R600 ° under the same conditions at the same time on site. D is more than 75%.

Special note: although some measures such as adding antifreeze and optimizing mix proportion are adopted for antifreeze mortar, protective measures for winter construction are still needed during construction.

During winter construction of decoration works, the mortar used shall be provided with heat preservation and antifreeze measures. For example, when admixture is added, the dosage shall be determined by laboratory test. In the process of mortar transportation, attention shall be paid to heat preservation and mixing as needed to prevent mortar from freezing.

Before indoor plastering, the hole and window shall be sealed, the edge of the door and window and the scaffold or hole of the external wall shall also be sealed, the construction hole, material transporting hole and stairwell shall be sealed for heat preservation, and the indoor plastering environment temperature shall not be lower than 5 ° C; after the indoor plastering works are bound, the indoor temperature shall not be lower than 5 ° C within 7 days. Shandong chuangyao Biotechnology Co., Ltd Remind that the temperature and curing temperature of veneer (brick) works during winter construction shall not be lower than 5 ° C, and the curing time shall not be less than 7d.

Painting, mounting and glass works shall be constructed under heating conditions. When outdoor construction is required, the minimum ambient temperature shall not be lower than 5 ° C, and construction shall be stopped in case of strong wind, rain and snow.

The external wall insulation project shall not be constructed in rainy and snowy days, and covering measures shall be taken in case of rain and snow during the construction. The construction ambient temperature of polystyrene board shall not be lower than 5 ° C. Spray hard foam polyurethane, and the construction ambient temperature shall not be lower than 10 ° C.

When the indoor temperature is lower than 5 ° C, the furnace (with good smoke exhaust or smoke-free fuel) or iodine tungsten lamp can be added for proper heating, but a special person must be appointed to be on duty, with corresponding fire fighting equipment, and pay close attention to prevent gas poisoning and fire.

Protective measures and precautions for mortar construction in winter

1. The construction environment temperature shall be kept above 5 ℃, and doors and windows shall be closed for indoor construction.

2. Adopt heat storage method to ensure the temperature of mortar mixture: the mortar shall be mixed in the warm shed

It is carried out in the greenhouse, and the ambient temperature is above 5 ° C. The temperature of mortar shall be kept