| Agriculture is the foundation of our country since ancient times.In recent years,China’s new rural construction scale expands rapidly,because of the traditional mortar strength is not ideal,life is limited,the structure is simple,often damage problems in practical use,and building materials,cement is a kind of multi-scale structure destruction throughout the entire process,it seriously affects the service life of the building materials,and has affected the safety of the people.And cement mortar modification mainly through mixing different types and sizes of fibers,so that the fibers reflect a better synergistic effect,and then play a mutual promotion effect.In this paper,by adding steel fiber and polyvinyl alcohol fiber,the length of fiber(steel fiber6 mm,12mm,20 mm,24mm,polyvinyl alcohol fiber 3mm,6mm,9mm,12mm),dosage(steel fiber1%,1.5%,2%,2.5%,The influence rule of polyvinyl alcohol fiber selection 0.1%,0.2%,0.4%,0.8%),method(single mixing,mixed mixing)and guarantee the mixing ratio of the same condition on mortar compressive strength,flexural strength,flexural ratio,water absorption and frost resistance.The results show that:1.Steel fiber can improve the mechanical properties and durability of mortar.The optimal length is 24 mm and the optimal dosage is 1.5%.Compared with standard mortar,the compressive strength of 7d and 28 d increases by 5.5% and 10.9% respectively.The 7d and 28 d flexural strength increased 40.3% and 35.7%,respectively,compared with the standard mortar of the same period.Compared with standard mortar in the same period,the bending pressure increased by 32.4% and21.4%.Compared with standard mortar in the same period,water absorption coefficient decreased by 3.7%.Under 20,40,60,80,100 freezing-thawing cycles,the strength loss rates of specimens are1.98%,4.29%,7.93%,11.08%,14.26%,and the mass loss rates of specimens are 0.23%,0.9%,2.9%,3.9%,4.5%.2.When mixing steel fibers of different lengths,the optimal scheme is mixing steel fibers of different lengths of 6mm,12 mm,20mm and 24 mm equally.The compressive strength of 7d and 28 d is increased by 0.57%,4.8%,1.8%,3%,2.3%,4.3%,2% and 1.1%,respectively,compared with the experimental results of single length steel fibers.The bending strength of 7d and 28 d increased by4%,2.2%,3.2%,2%,5.5%,3.6%,0.87%,0.2% compared with that of single length steel fiber.Compared with the single length steel fiber,the bending ratio of 7d and 28 d increased by 9.8% and10.3%.The water absorption coefficient is 7.5% lower than that of standard mortar.At 20,40,60,80,100 freezing-thawing cycles,the strength of the specimen is 1.76%,3.99%,7.56%,10.67%,13.58%,and the mass loss rate is 0.28%,0.9%,2.9%,3.7%,4.1%.3.Polyvinyl alcohol fiber can improve the mechanical properties and durability of mortar under a certain length and dosage.The optimal length is 9mm,and the optimal dosage is 0.2% and 0.8%.The maximum compressive strength of 7d and 28 d mortar is at 0.8%,which is 31.7% and 29%higher than that of standard mortar at the same period,respectively.The maximum bending strength of 7d and 28 d mortar is at 0.4%,which is 16.5% and 8.2% higher than that of standard mortar at the same period,respectively.The bending ratio of 7d and 28 d reached the maximum at 0.8%,which increased 35% and 29.9%,respectively,compared with the standard mortar of the same period.The water absorption coefficient at 48 h is the lowest at 0.4%,which is 7.2% lower than that of standard mortar in the same period.The strength loss rate was 0.49%,0.45%,0.99%,3.7% and 4.8%,and the mass loss rate was 2%,4.38%,8.14%,11.26% and 14.21% under 20,40,60,80 and 100freezing-thawing cycles.4.When polyvinyl alcohol fibers of different lengths are mixed,the optimal combination is that the optimal scheme of this experiment is 3mm,6mm,9mm and 18 mm polyvinyl alcohol fibers of different lengths are mixed with 0.2% or 0.8% of the total content,and the 7d and 28 d compressive strength is the best when the total content is 0.2%.Compared with the standard mortar in the same period,the mortar increased by 9.4% and 12.6%.The 7d and 28 d flexural strength is the best when the total content of mortar is 0.8%,which is 42.1% and 27% higher than that of standard mortar in the same period.The 7d and 28 d compression ratio of 0.8% is the best,which is 33.3% and 21%higher than the standard mortar test results in the same period.When the water absorption coefficient is 0.8%,the best,48 h compared with the standard mortar decreased by 8.6%;The strength loss rate was 1.92%,4.2%,7.51%,11.62% and 13.68%,and the mass loss rate was 0.48%,0.95%,2.36%,3.71% and 3.95% under 20,40,60,80 and 100 freezing-thawing cycles.5.The mechanical properties and durability of mortar are generally improved better than that of single mixing when steel and polyvinyl alcohol fiber are mixed,and the optimal scheme is that steel fiber of 6mm,12 mm,20mm and 24 mm is mixed equally with the total mixing amount of 1.5%,and polyvinyl alcohol fiber of 3mm,6mm,9mm and 18 mm is mixed equally with the total mixing amount of 0.8%.The 7d and 28 d compressive strength increased 19.2% and 16.2%,respectively,compared with the standard mortar of the same period.The flexural strength of 7d and 28 d is 42.6%and 41.3% higher than that of standard mortar at the same period.The 7d and 28 D bending ratio of standard mortar increased by 27% and 25% in the same period.The 48 h water absorption coefficient is 11% lower than that of standard mortar in the same period.Under 20,40,60,80,100 freeze-thaw cycles,the strength loss rates are 1.72%,3.96%,7.03%,10.28%,12.97%,and the mass loss rates are0.26%,0.86%,3.02%,3.82%,4.22%.6.Through the comprehensive analysis of fiber macroscopically and microscopically,it is determined that steel fiber and polyvinyl alcohol fiber in mortar can improve the mechanical properties and durability of matrix by inhibiting the expansion and extension of cracks.From the perspective of economy,it is concluded that the mixing mode with steel fiber as the main fiber and polyvinyl alcohol fiber as the auxiliary fiber is the most economical. |
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