In the construction of external thermal insulation, the mortar of protective surface layer often appears partially whitening, especially in wet coastal areas or the mortar of protective surface layer is dripped by rainwater soon after construction, whitening phenomenon often occurs. What is the cause of these whiteness? How can we prevent the occurrence of this phenomenon?

　　济南抹面砂浆厂家教你如何应对：

　　Jinan plastering mortar manufacturer teaches you how to deal with:

　　1、防护面层砂浆硬化后，即便比拟枯燥，但在运用过程中总会遭到雨水浸泡，当水分渗入其内部，将其内部可溶性物质（如NaOH、KOH、Na2SO4、Ca(OH)2等）带出来，碱与空气中的CO2和水分发作反响生成碳酸盐，与硫酸盐一同沉淀在外表，且象CaCO3、CaSO4等物质不易被雨水冲走，因此结实地附着在防护面层外表。

　　1. After hardening, the mortar of the protective surface layer will be soaked by rain water even if it is comparatively dull. When water infiltrates into its interior, it will bring out its soluble substances (such as NaOH, KOH, Na2SO4, Ca (OH) 2, etc.). Alkali reacts with CO2 and water in the air to form carbonate, which precipitates with sulfate. Appearance, and like CaCO3, CaSO4 and other substances are not easily washed away by rainwater, so firmly attached to the surface of the protective layer.

　　2、当有一定湿度时, 空气中的CO2与水分分离构成H2CO3,H2CO3与基材外表的Ca(OH)2发作反响, 生成CaCO3; H2CO3还会浸透到基材内部与Ca(OH)2化合成Ca(HCO3)2, Ca(HCO3)2也会随着外表水分蒸发被水分从基材内部带出来,直接结晶, 或者再与H2CO3反响生成CaCO3。

　　2. When there is a certain humidity, CO2 and water in the air separates to form H2CO3, which reacts with Ca(OH)2 on the surface of the substrate to form CaCO3; H2CO3 also soaks into the interior of the substrate and reacts with Ca(OH)2 to synthesize Ca(HCO_3)2, and Ca(HCO_3)2 crystallizes directly or reacts with H2CO_3 as water evaporates from the interior of the substrate. Generate CaCO3.

　　3、由于工业污染, 空气中普通含有一定量的SO2, SO2溶于雨水后构成酸雨, 这种酸雨渗入基材内部, 与基材中的碱性物质相分离并随着水分迁移到外表结晶,也会惹起泛白。 上述这些白色物质的析出结晶在一定水平上能够增加基材外表的密实性,但是由于雨水循环作用,会将堆积在外表的可溶性的结晶物冲走,而基材内部由于可溶性物质的溶出,增大了孔隙率, 降低了基材的抗渗性, 从而会使盐、碱的析出作用加剧。

　　3. Owing to industrial pollution, the air usually contains a certain amount of SO2, which dissolves in rainwater to form acid rain. This acid rain penetrates into the interior of the substrate, separates from the alkaline substances in the matrix and crystallizes with the water migrating to the surface, which also causes whitening. The precipitation and crystallization of these white substances can increase the surface compactness of the base material to a certain extent, but due to the circulation of rainwater, the soluble crystals accumulated on the surface will be washed away, while the dissolution of soluble substances in the base material increases the porosity and reduces the impermeability of the base material, which will lead to salt and alkali precipitation. The effect is aggravated.

　　预防泛白措施

　　Preventive measures against whitening

　　注重资料选择

　　Pay attention to data selection

　　1、在选用水泥时, 应尽量选用碱金属氧化物含量低的低碱水泥。

　　1. When selecting cement, low alkali cement with low alkali metal oxide content should be selected as far as possible.

　　2、配制防护面层砂浆时，对集料要有一定的选择性，应该严厉控制其可溶性盐含量。

　　2. When preparing protective surface mortar, the aggregate should be selective and the soluble salt content should be strictly controlled.

　　3、尽量不运用碱金属含量高的外加剂。在配制防护面层砂浆或砂浆时, 采用适合的外加剂, 如运用减水剂或减水剂, 能够降低拌和用水量, 从而减小防护面层砂浆或砂浆的孔隙率, 改善孔构造, 进步抗渗性能。能够说,只需是可以加强防护面层砂浆或砂浆密实性、减少开裂且含碱金属氧化物少的外加剂都可采用，如防水剂、收缩剂和早强剂等。

　　3. Try not to use additives with high alkali content. When preparing protective surface mortar or mortar, the use of suitable additives, such as water reducing agent or high-efficiency water reducing agent, can reduce the amount of water used, thereby reducing the porosity of protective surface mortar or mortar, improving pore structure and improving impermeability. It can be said that only additives such as waterproofing agent, shrinkage agent and early strength agent can be used to strengthen the compactness of mortar or mortar of protective surface layer, reduce cracking and contain less alkali metal oxides.

　　增强施工防备

　　Strengthening Construction Preparedness

　　当然，在施工时, 应采取积极的预防措施。首先，外保温施工中应时辰留意天气变化，防止低温及高湿天气条件下施工防护面层砂浆；另外，外保温防护面层砂浆施工完成之后不宜暴露时间过长，应及时停止外饰面施工并防止遭受雨淋。防护面层砂浆在初凝时, 渗出外表的水分越多, 呈现泛白的严重性就越大, 也就是说水灰比大的防护面层砂浆泛白较多, 为此, 在满足施工操作的前提下, 应尽量减少拌和用水量。当泛白现象发作后, 在不影响砂浆性能的状况下, 寻觅一些有效对策来处治, 抵消除泛白,是十分可取的。

　　Of course, active preventive measures should be taken during construction. Firstly, we should pay attention to the weather changes at all times in the construction of external thermal insulation to prevent the construction of protective surface mortar under low temperature and high humidity weather conditions; in addition, after the completion of the construction of external thermal insulation protective surface mortar, it is not appropriate to expose for too long, so we should stop the construction of external decorative surface in time and prevent rain. When the protective surface mortar first solidifies, the more water seeps out from the surface, the more serious the whitening is. That is to say, the whitening of the protective surface mortar with large water cement ratio is more. Therefore, under the premise of satisfying the construction operation, the amount of mixing water should be reduced as far as possible. When the whitening phenomenon occurs, it is very desirable to find some effective countermeasures to eliminate the whitening without affecting the performance of mortar.

　　以上是济南抹面砂浆泛白缘由及防备措施相关内容介绍，本文来源：//www.gochiism.comThe above is an introduction to the causes of whitening of Jinan plastering mortar and its preventive measures. The source of this paper is //www.gochiism.com.