| Printed circuit boards are the core components of electronic products,and the high frequency of electronic products and the proliferation of intelligent products have led to an increasing accumulation of wasteprinted circuit boards.At the same time,it has caused serious pollution to the environment.Therefore,the harmless treatment of wasteprinted circuit boards has become an urgent problem to be solved.Cement-based materials are still the most used building materials and are highly inclusive.Pre-treating wasteprinted circuit boards into powder and then mixing them with cement mortar can effectively solve their pollution problems.In this study,two wasteprinted circuit board powders of different particle sizes were added to cement mortar with 0%,1%,2.5%,4% and 5.5% of cement mass,respectively,and the effects of wasteprinted circuit board powders with different particle sizes and different dosages on the basicmacroscopic properties(including compressive strength,flexural strength,fluidity,consistency,capillary water absorption,porosity,water retention)and durability(including sulfate corrosion resistance and frost resistance)of cement mortar were studied.Scanning electron microscopy(SEM)and X-ray diffraction(XRD)and other tests carried out microscopic research on wasteprinted circuit board powder and modified mortar,and analyzed the modification mechanism of wasteprinted circuit board mortar through microscopic tests.The main research results are as follows:(1)The macroscopic properties of modified mortar were tested and studied,and the following conclusions were obtained: Two kinds of particle size waste printed circuit boards can improve the strength of cement mortar.The strength of modified mortar is the highest when the content of fibrous waste printed circuit board powder is 1 %,and the strength of modified mortar is the highest when the content of fine powderwaste printed circuit board powder is 2.5 %.Under the same content,the strength of granular waste printed circuit board powder modified mortar is higher than that of fine powderwaste printed circuit board powder modified mortar.The porosity and capillary water absorption of fiber powder modified mortar are the smallest when the content is 1 %,while the particle powder modified mortar is the smallest when the content is 2.5 %.This result is consistent with the mechanical property result;The addition of waste printed circuit board powder will reduce the fluidity and consistency of mortar,and the fluidity of modified mortar decreases with the increase of waste printed circuit board powder content.The incorporation of waste printed circuit board can improve the water retention of mortar.With the increase of content,the water retention performance is gradually enhanced.(2)The durability of two kinds of waste printed circuit board powder modified mortar was tested.The results show that the addition of appropriate amount of waste printed circuit board powder can improve the freeze-thaw resistance,sulfate corrosion resistance of cement mortar.Moreover,under the same dosage,the durability improvement effect of fine powder waste circuit board powder on cement mortar is better than that of fibrous waste circuit board powder.In the range of test content,after freeze-thaw cycle test and sulfate immersion test,the mass loss rate and strength loss rate of mortar showed a trend of first decreasing and then increasing with the increase of the content.When the content of fiber waste printed circuit board powder is 1 %,the mass loss rate and strength loss rate of modified mortar after freeze-thaw test and sulfate immersion are the lowest,and are lower than the blank group;when the content of fine powderwaste printed circuit board powder was 2.5 %,the mass loss rate and strength loss rate of modified mortar after freeze-thaw test and sulfate immersion were the lowest,which were also lower than those of the blank group.(3)The modification mechanism of waste printed circuit board powder mortar was studied by FTIR,XRD and SEM.The results show that waste printed circuit board powder can fill the internal pores of mortar,increase the internal density of mortar,and improve the strength and durability of mortar.At the same time,the filling effect of fine powder waste printed circuit board powder on the inside of cement mortar is better than that of fibrous powder under the same amount;FTIR and XRD analysis of waste printed circuit board powder found that amorphous silica exists in waste printed circuit board powder,which can promote the hydration reaction of cement,thereby further increasing the strength and durability of modified mortar.However,when the dosage is too high,the strength and durability of the modified mortar will be reduced due to agglomeration. |
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