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?

　　濟南抹面砂漿廠家教你如何應對：

　　Jinan plastering mortar manufacturer teaches you how to deal with:

　　1、防護面層砂漿硬化后，即便比擬枯燥，但在運用過程中總會遭到雨水浸泡，當水分滲入其內部，將其內部可溶性物質（如NaOH、KOH、Na2SO4、Ca(OH)2等）帶出來，堿與空氣中的CO2和水分發作反響生成碳酸鹽，與硫酸鹽一同沉淀在外表，且象CaCO3、CaSO4等物質不易被雨水沖走，因此結實地附著在防護面層外表。

　　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、當有一定濕度時, 空氣中的CO2與水分分離構成H2CO3,H2CO3與基材外表的Ca(OH)2發作反響, 生成CaCO3; H2CO3還會浸透到基材內部與Ca(OH)2化合成Ca(HCO3)2, Ca(HCO3)2也會隨著外表水分蒸發被水分從基材內部帶出來,直接結晶, 或者再與H2CO3反響生成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、由于工業污染, 空氣中普通含有一定量的SO2, SO2溶于雨水后構成酸雨, 這種酸雨滲入基材內部, 與基材中的堿性物質相分離并隨著水分遷移到外表結晶,也會惹起泛白。 上述這些白色物質的析出結晶在一定水平上能夠增加基材外表的密實性,但是由于雨水循環作用,會將堆積在外表的可溶性的結晶物沖走,而基材內部由于可溶性物質的溶出,增大了孔隙率, 降低了基材的抗滲性, 從而會使鹽、堿的析出作用加劇。

　　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.

　　預防泛白措施

　　Preventive measures against whitening

　　注重資料選擇

　　Pay attention to data selection

　　1、在選用水泥時, 應盡量選用堿金屬氧化物含量低的低堿水泥。

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

　　2、配制防護面層砂漿時，對集料要有一定的選擇性，應該嚴厲控制其可溶性鹽含量。

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

　　3、盡量不運用堿金屬含量高的外加劑。在配制防護面層砂漿或砂漿時, 采用適合的外加劑, 如運用減水劑或減水劑, 能夠降低拌和用水量, 從而減小防護面層砂漿或砂漿的孔隙率, 改善孔構造, 進步抗滲性能。能夠說,只需是可以加強防護面層砂漿或砂漿密實性、減少開裂且含堿金屬氧化物少的外加劑都可采用，如防水劑、收縮劑和早強劑等。

　　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.

　　增強施工防備

　　Strengthening Construction Preparedness

　　當然，在施工時, 應采取積極的預防措施。首先，外保溫施工中應時辰留意天氣變化，防止低溫及高濕天氣條件下施工防護面層砂漿；另外，外保溫防護面層砂漿施工完成之后不宜暴露時間過長，應及時停止外飾面施工并防止遭受雨淋。防護面層砂漿在初凝時, 滲出外表的水分越多, 呈現泛白的嚴重性就越大, 也就是說水灰比大的防護面層砂漿泛白較多, 為此, 在滿足施工操作的前提下, 應盡量減少拌和用水量。當泛白現象發作后, 在不影響砂漿性能的狀況下, 尋覓一些有效對策來處治, 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.

　　以上是濟南抹面砂漿泛白緣由及防備措施相關內容介紹，本文來源：http://www.sjzmx.cnThe above is an introduction to the causes of whitening of Jinan plastering mortar and its preventive measures. The source of this paper is http://www.sjzmx.cn.