Study On Polymer-Modified Waterproof Mortar With Low Environment Load

Polymer-modified waterproof mortar is a very important composite material withgood prospects. In this paper, a low environmental friendly polymer-modifiedwaterproofing mortar was developed from a new type of cementitious materials-eco-cement (Solid waste content is over70%), aggregates (40%iron tailings and60%sand) and suitable polymer.Based on the starting point for preparation of the low environmental loadpolymer-modified waterproofing mortar, the single factor experiments were done to studyeffects of polymer-cement ratio, water-cement ratio, silica fume, defoamer and curingmethods on mortar properties. The main factors and their varying ranges were defermined.The appropriate curing regime is to cure in wet environment for the first7days and in dryenvironment for the following21days. The Orthogonal experiment was designed todetermine the optimization formulation of polymer-modified mortar with lowenvironmental load. The obtained optimal process conditions are: cement-sand ratio,1:2.5(tailings:river sand=1:1.5); polymer-cement ratio,0.1; polymer ratio of EVA andpoly.vinyl,3:1; water-cement ratio,0.4; defoamer agent,0.2wt%(cement based); silicafume agent,10wt%(cement based). The influence order of factors on strength is:polymer-cement ratio>cement-sand ratio>water-cement ratio. For the prepared mortar, theratio of compressive strength to flexural strength is2.70and the impermeability strength is1.8Mpa. Other performances conform to JG/T984-2005(China professional standard,Polymer cement waterproof mortar standards for emulsion type).For overcoming the transport and storage problems of latex modified mortar, thedry-mixed waterproof mortar with low environment load was developed using latexpowder instead of emulsion. The orthogonal experiment and mixture uniform design wereused to determine the optimized formulation with the coincident results. The optimalprocess conditions are: the cement-sand ratio,1:2.39(tailings:river sand=1:1.5); thepolymer-cement ratio,11.6%; the admixture,0.85wt%(cement based). The ratio ofcompressive strength to flexural strength is2.89and the impermeability strength is1.8Mpa. Other performances conform to JG/T984-2005(China professional standard,Polymer cement waterproof mortar standards for powder type).The modification mechanism for polymer-modified mortar was analyzed using FT-IR,TGA, XRD and SEM. The rate of cement hydration is decreased because of the polymer addition. However, the flexural strength and impermeability strength improved. Thereason may be that the polymer can fill the pores in the mortar and make the interfacialtransition zone of cement-aggregate become more compact. The network membranousstructure formed by the polymer can also increase the paste’s toughness and flexuralstrength，thus improving waterproof property.In this study，a new eco-cement was used to the mortar insread of the P.O. cement,the iron tailings replace riversand, reducing the impact on environment. Through thisapproach, a new way to utilize iron tailings was found, solving，to same extent，theenvironment problems of traditional mortars.