Study On Polymer Modification Of Waterproof Mortar For Underground Engineering

In high waterproof demand projects such as underground engineering,water conservancy engineering,and submarine engineering,the mechanical properties and impermeability of ordinary waterproof mortar are difficult to meet relevant usage requirements.Practice has shown that polymer modification can make ordinary waterproof mortar have better impermeability,crack resistance,durability,and compactness,which is of great research significance.In this paper,the water cement ratio,consistency,compressive strength,flexural strength,impermeability strength,and water absorption of waterproof mortar were studied using single factor tests,multi factor orthogonal tests,and theoretical analysis methods.The influence of machine-made quartz sand with different mesh sizes and admixtures on the performance of waterproof mortar was analyzed.On this basis,the relationship between polymer,inorganic mineral,silicone material and waterproof mortar was further explored.The conclusions are as follows:(1)The mechanical properties of waterproof mortar decrease with the increase of quartz sand mesh number,and the optimal sand mesh number for this test is selected as60-80.In terms of modified admixtures,when silica fume with a content of 3%,calcium sulphoaluminate expansion agent with a content of 5%,and polycarboxylic acid water reducing agent with a content of 0.5% are mixed and used,the waterproof mortar can achieve optimal mechanical properties and water absorption.At this time,the compressive strength is increased by about 23%,and the water absorption is reduced by2.4 percentage points.(2)Vinyl acetate vinyl(VAE)redispersible emulsion powder will form a polymer film inside the waterproof mortar.The membrane structure formed by interconnection is distributed in mortar pores and cavities,which can fill water seepage channels,greatly improving impermeability while reducing compressive strength.The optimal amount of VAE emulsion powder,which accounts for 3% of the cement mass,is selected.At this time,the compressive strength of the waterproof mortar decreases by about 31%,and the impermeability strength increases by 70%.(3)Metakaolin can undergo a secondary reaction with calcium hydroxide generated by hydration of cement.When the content of such materials is too large,the active particles of metakaolin can only play a filling role and cannot generate relevant hydrates.Based on various properties,metakaolin,which accounts for 6% of the cement quality,is selected as the optimal amount.At this time,the compressive strength of the waterproof mortar is reduced by about 7% compared to that without adding additives,and the impermeability strength is increased by 50%.(4)Polysiloxane powder hydrophobic agent is an organosilicon type powder resin.Its active ingredients can generate hydrophobic groups inside the waterproof mortar,and form a smooth and dense polysiloxane film after curing.This can give the waterproof mortar excellent hydrophobicity,improve impermeability,and reduce water absorption.The optimal amount of silicone material,which accounts for 0.5% of the cement mass,is selected.At this time,the compressive strength of the waterproof mortar is reduced by about 4% compared to that without addition,and the impermeability strength is increased by about 16%.(5)The waterproof mortar after final modification through the above tests has a maximum compressive strength of 52.1MPa,a maximum flexural strength of 6.4MPa,a maximum impermeability strength of 2.3MPa,and a minimum water absorption of 5.2%.All properties meet the requirements of national specifications for polymer waterproof mortar.The research results can provide certain basis and reference for the efficient use of polymer waterproof mortar in underground engineering.