环氧地坪漆出現返堿的原因及解決辦法

返堿問題常出現於：幹粉塗料、水泥基自流平、耐磨环氧地坪、填縫劑等幹粉砂漿。 返堿的機理：堿性離子通過水份帶出表面與鈉、鈣等離子在表面結晶和生成鹽分並結晶形成白色粉末。 引起返堿的因素： ①矽酸鹽水泥水化過程中，C3S和C2S水化生成C-S-H凝膠的同時，形成瞭大量的Ca(OH)2，Ca(OH)2除有一部分用以維持液相的堿度外，其它大多以晶體形態存在於水泥石中。Ca(OH)2是一種極易溶解的物質，在水泥基材料凝結硬化早期，其中的自由水會逐漸沿著內部毛細孔向外遷移，以補償表面被蒸發掉的水分，在這一過程中，必然會將溶於其中的Ca(OH)2帶出，當到達材料表面後，Ca(OH)2還會與空氣中的CO2和水分發生化學反應生成不溶於水的白色沉淀CaCO3，附著在材料表面，這就是常見的表面泛白現象。這是最基本的一個因素，其他很多因素的本質和該條基本相同．
Alkali return often occurs in dry powder coatings, cement-based self-leveling, wear-resistant epoxy floors, sealants and other dry powder mortars. The mechanism of alkaline return: alkaline ions take out of the surface through water, and sodium, calcium plasma crystallize on the surface and form salt and crystallize to form white powder. The factors leading to the return of alkali: (1) during the hydration of Portland cement, C3S and C2S hydrated to form C-S-H gel, and at the same time, a large amount of Ca (OH) 2 was formed, while Ca (OH) 2 was used to maintain the alkalinity of the liquid phase, most of which existed in cement paste in the form of crystal. Ca (OH) 2 is a very soluble substance. In the early stage of setting and hardening of cement-based materials, free water will gradually migrate outward along the inner pores to compensate for the evaporated water on the surface. In this process, the dissolved Ca (OH) 2 will inevitably be removed. When it reaches the surface of the materials, Ca (OH) 2 will also be in the air. The chemical reaction of CO2 and water distribution produces white precipitate CaCO3 which is insoluble in water and adheres to the surface of the material. This is a common phenomenon of surface whitening. This is the most basic factor. The essence of many other factors is basically the same as that one.
②趕工期(常見於冬春季)，使用Na2SO4、CaCl2或以它們為主的復合產品作為早強劑，增加瞭水泥基材料的可溶性物質。 ③材料自身內部存在一定量的堿是先決條件，產生的原因水泥基材料屬於多孔材料, 內部存在有大量尺寸不同的毛細孔, 成為可溶性物質在水的帶動下從內部遷移出表面的通道。 ④水泥基材料即使硬化後比較幹燥，但在使用過程中受到雨水浸泡，當水分滲入其內部，將其內部可溶性物質帶出來，在表面反應並沉淀。
(2) During the rush period (usually in winter and spring), the use of Na2SO4, CaCl2 or their composite products as early strength agents increased the solubility of cement-based materials. (3) The existence of 彩色沥清地坪a certain amount of alkali in the material itself is a prerequisite. The reason is that the cement-based material belongs to porous material. There are a large number of different sizes of pores in the cement-based material, which can be used as a channel for soluble substances to migrate from the interior to the surface under the drive of water. (4) Even though the cement-based materials are relatively dry after hardening, they are soaked in rainwater during use. When环氧地坪 the water infiltrates into the cement-based materials, the soluble substances in the cement-based materials are taken out and reacted on the surface and precipitated.
⑤濕度較大時，空氣中的CO2與水分結合形成H2CO3，滲透到基材內部與Ca(OH)2化合成Ca(HCO3)2 , Ca(HCO3)2隨著表面水分蒸發被帶出來，直接結晶或者再與H2CO3反應生成CaCO3。 ⑥酸雨滲入基材內部，與基材中的堿性物質相結合並隨著水分遷移到表面結晶，也會引起泛白。 返堿析出結晶在一定程度上可以增加基材表面的密實性，但是由於雨水循环作用，會將沉積在表面的可溶性的結晶物沖走，而基材內部由於可溶性物質的溶出，增大瞭孔隙率，降低瞭基材的抗滲性，從而會使鹽、堿的析出作用加劇。
_When humidity is high, CO2 in the air combines with water to form H2CO3, which penetrates into the substrate and reacts with Ca (OH) 2 to synthesize Ca (HCO3) 2. Ca (HCO3) 2 is taken out with the evaporation of surface water and crystallizes directly or reacts with H2CO3 to form CaCO3. _Acid rain infiltrates into the substrate, combines with the alkaline substances in the substrate and crystallizes on the surface with moisture migration, which also causes whitening. Re-alkali precipitation crystallization can increase the surface compactness of the substrate to a certain extent, but the soluble crystals deposited on the surface will be washed away by rainwater cycling, and the porosity of the substrate will be increased and the impermeability of the substrate will be reduced due to the dissolution of soluble substances in the substrate. Intensifying.
減輕环氧地坪漆返堿的措施： ①沒有根治的辦法，隻能盡可能降低其發生的幾率，控制幹粉砂漿攪拌過程的加水量。施工時环氧地坪材料不能泌水、完全幹燥前表面不能與水接觸；填縫劑施工過程務必在海綿擦拭後使表面水分盡快揮發，或使用不要太濕潤的海綿。 ②盡量使用低堿水泥和外加劑。 ③優化配合比，增加水泥基材料密實度，減小毛細孔。例如使用其它熟料、填料替代部分水泥。 ④使用返堿抑制劑。如ELOTEX ERA-100，但經過使用不能完全改變這個情況，隻能在某種程度上減輕返堿的情況，約100元/kg，摻量每噸約2.5kg，若摻量太高成本過高。 ⑤避免在幹燥、刮風、低溫环境條件下施工。 ⑥矽酸鹽水泥與高強硫鋁酸鹽水泥復合使用有一定效果。原理如下：
Measures to alleviate the alkali return of epoxy floor paint: 1. There is no radical cure, only to reduce the probability of occurrence as far as possible, and control the amount of water added in the mixing process of dry powder mortar. During the construction, the floor material can not bleed, and the surface can not contact with water before completely drying; during the construction of sealant, it is necessary to make the surface moisture evaporate as soon as possible after sponge wiping, or to use a sponge that is not too wet. 2. Use low alkali cement and additives as much as possible. Third, optimize the mix proportion, increase the density of cement based materials and reduce Mao Xikong. For example, use other clinker and filler to replace part of cement. (4) use of alkali repressor. For example, ELOTEX ERA-100, but after use can not completely change this situation, can only reduce the return of alkali to a certain extent, about 100 yuan / kg, the amount of about 2.5 kg per ton, if the dosage is too high cost. Avoid construction under dry, windy and low temperature conditions. The combination of Portland cement and high strength sulphoaluminate cement has certain effect. The principles are as follows:
Ⅰ、硫鋁酸鹽水泥的2CaO?SiO2水化後生成的Ca(0H)2會與其它水化產物發生二次反應，形成新的化合物。3Ca(OH) 2+Al2O3?3H2O+3(CaSO4?2 H2O)+20 H2O→3 CaO?Al2O3?3CaSO4?32H2O。因此硫鋁酸鹽水泥水化產物不存在Ca(OH)2析晶。
I. Ca(0H)2 produced by hydration of 2CaO?SiO2 in sulphoaluminate cement reacts with other hydration products to form new compounds. 3Ca (OH) 2+Al2O3? 3H2O+3 (CaSO4? 2 H2O) +20 H2O to 3 CaO? Al2O3? 3CaSO4? Therefore, there is no Ca (OH) 2 crystallization in the hydration products of sulphoaluminate cement.
Ⅱ、硫鋁酸鹽水泥與普通矽酸鹽水泥復合使用，水化過程中硫鋁酸鹽水泥會把普通矽酸鹽水泥產生的多餘的Ca(OH)2消耗掉，從根本上解決瞭返堿的問題。 重慶环氧地坪漆出現返堿後的處理方法： ①填縫劑出現嚴重返堿時，用低濃度的鹽酸、草酸如５％的稀鹽酸清洗，必要時用防水劑塗刷。 ②硫酸鈉起霜應采用物理法處理。
II. When sulphoaluminate cement is combined with ordinary Portland cement, the excess Ca (OH) 2 produced by ordinary Portland cement will be consumed in the hydration process, and the problem of returning to alkali will be solved fundamentally. The treatment methods of Chongqing floor paint after alkali return are as follows: 1. When serious alkali return occurs in the sealant, clean it with low concentration of hydrochloric acid and oxalic acid such as 5% dilute hydrochloric acid, and brush it with waterproof agent if necessary. 2. Sodium sulfate frosting should be treated by physical method.