| Whitish deposits of calcium carbonate, Ca CO3, frequently develop on the surface of cement based decorative mortars. Efflorescence is aesthetically undesirable, which hindered it’s large-scale application. Nowadays, there is a lack of consensus in the characterization methods of the efflorescence degree of decorative mortar, studies on the factors which have impacts on efflorescence are not enough, pragmatic remedy for suppressing efflorescence is not found. In this paper the characterization methods of the efflorescence degree of decorative mortar was addressed, quantitative analysis on the factors which effect efflorescence was made, and a comparison of several corresponding inhibitory measures was studied. The results show that:① The effects of colors in different gray scales on mortar appearance can be distinguished by the image processing techniques, and colors in efflorescence region would obviously affect it when their gray scales were 15 higher than that of matrix color. Experimental results proved that the calculated value of the formula: = ∑ ×=255=+15 which was proposed in part Ⅲ can not only feature the efflorescence degree well but had a good conformance with the actual value② The efflorescence degree would heighten as the content of Ca(OH)2 increased, when the content of Ca(OH)2 below 3.24% the decorative mortar eliminates initial efflorescence, while it below 4.82% the decorative mortar abstains secondary efflorescence.The relations between the open porosity and initial and secondary efflorescence are as: = and Y=3.4432x-9.47778. Thus, the open porosity is one of the decisive factor which determines the extent of mortar efflorescence, increase the opening porosity would raise the risk of efflorescence. The wettability can impact the efflorescence degree in great extent, increase its contact angle can promote the mortar surface change to hydrophobic and raise its impermeability which can prevent external moisture from entering the interior of the mortar. The efflorescence degree of mortar coated with a water repellent lotion on 1d and 7d are only 16.0 and 5.4, means hydrophobic treatment can effectively inhibit the secondary efflorescence. Alter temperature / humidity/wind speed and other environmental factors would impress the efflorescence degree in varying extent. The change in humidity is the most sensitive factor of efflorescence degree, temperature change is followed by the change of wind speed.③ Redispersible powder and cellulose ethers can all reduce water absorption, and form complexes in mortar with alkali ions which hinders Ca2+/Na+ and K+ ions migrate to the surface, thus effectively mitigate efflorescence. Moreover, double mixing the two kinds of polymers can obtain better synergy. Defoamer evidently lightens efflorescence by enhancing the compactness of the decorative mortar and effectively reducing the channels which allow alkali ions migrate to the surface. Adding 0.05%-0.15% defoamer can reduce efflorescence degree to below 30.0 degrees. As the channel through which moisture penetrate to the surface cannot be completely blocked,the effect of adding defoamer to suppress efflorescence is not ideal. Metakaolin reacts Ca(OH)2 massively in a small content which improves efflorescence resistance of cement based decorative mortar while the addition of inert filler has no obvious influence in extenuating efflorescence.And inert filler even intensifies efflorescence when its content is more than 10%. Mixing powdered water repellent in mortar or treating the surface of mortar with waterproofing agent can facilitate the change of mortar surface to hydrophobic and increase its impermeability which makes it difficult for external moisture to enter the interior of mortar,reduce water absorption and improve the efflorescence resistance. Additionally, the coated waterproofing agent obtains better inhibitory effect. The latter has better effect in suppressing efflorescence than the former. |
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