EVA与硅烷乳液改善防水砂浆性能的微观机理

Microstructural Mechanism of EVA and Silane Emulsion Improving Waterproof Mortar

摘要:

通过四点弯曲强度、黏结强度、冻融循环及热重、压汞和扫描电镜等试验研究了乙烯-乙酸乙烯酯共聚乳液（EVA）和硅烷乳液对高韧性防水砂浆力学性能和抗冻性的影响规律及作用机理. 结果表明：EVA基本不影响砂浆后期弯曲性能，但显著提高其与基层的黏结强度；随EVA掺量增加，砂浆孔隙率先增大后减小，抗冻性先降低后提高；硅烷乳液的掺入显著降低了水化产物在聚乙烯醇（PVA）纤维表面的附着，导致砂浆弯曲性能下降；当硅烷乳液掺量较高时，PVA纤维与基体界面粗糙度明显增加，砂浆弯曲性能提高；内掺硅烷乳液增加了毛细孔含量，有助于缓解孔隙水结冰产生的膨胀应力，从而显著提高砂浆抗冻性.

Abstract:

Influence of ethylene-vinyl acetate copolymer（EVA） and silane emulsion on the mechanical properties and frost resistance of the high toughness waterproof mortar was investigated through four-point bending test， bonding test， freeze-thaw cycle test， thermogravimetric analysis， mercury intrusion test and scanning electron microscopy. The results show that EVA has little effect on the bending properties at late age， but significantly improves its bonding strength. With the increase of EVA content， the porosity of mortar initially increases and subsequently decreases， and the frost resistance decreases at first and then increases. The inclusion of silane emulsion significantly reduces the adhesion of hydration products on poly vinyl alcohol（PVA） fibers， resulting in the decreasing of bending properties of mortar. By contrast， at high dosages of silane emulsion， the interfacial roughness between fiber and matrix increases obviously， which is beneficial to increasing the bending properties. The incorporation of silane emulsion alleviates the expansion stress caused by water freezing due to the increasing capillary pores， which significately improves the frost resistance.