| With the continuous and stable development of my country's construction industry,a large amount of construction waste has been continuously produced,which has greatly increased the pressure on my country's environmental protection.Only by establishing a good ecological industry for recycling construction waste can this pressure be effectively resolved.The poor quality of recycled aggregates is an urgent problem facing construction waste recycling.Based on the basic physical properties of recycled aggregates,this paper analyzes the influence of strengthening technology on recycled aggregates and recycled materials,and explores the direction of subsequent strengthening of recycled aggregates.First,this article uses a jaw crusher and an impact crusher to crush waste concrete into two types of recycled aggregates.The particle density,apparent density,bulk density,crushing value and water absorption of these two aggregates are measured.The circularity and fractal dimension of recycled aggregates are analyzed,and the open porosity and hardened mortar volume content of the two recycled aggregates are calculated through the relationship between particle density and apparent density.Secondly,according to the difference in particle density between recycled aggregate(RCA)and natural aggregate(NCA),the formula used in the design of the mix ratio of recycled materials was revised.Third,this article focuses on the difference between the open porosity of RCA and NCA aggregates.Sodium silicate(SN)solution is used to soak RCA and nano silica(NS)dispersion to fill the open porosity for strengthening.By combining basic physical property data,scanning electron microscope(SEM))Characterization results and X-ray diffraction(XRD)characterization test and other analysis test data,to discuss the influence of strengthening process on recycled aggregate.Finally,combined with the revised formula for mixing ratio,the reinforced aggregate is prepared into a recycled material,and its compressive strength is tested and compared,and the following conclusions are drawn:(1)Test the basic physical properties of counterattack crushed recycled aggregate(IRCA)and jaw crushed recycled aggregate(JRCA)based on the national standard"Pebbles and Crushed Stones for Construction"(GB/T14685-2011),and found the water absorption rate of IRCA,Crushing value,bulk density,apparent density and other basic physical properties are better than JRCA;IRCA aggregate has a higher degree of crushing,and JRCA has a higher conversion rate of coarse aggregate.Furthermore,the particle density,open porosity,hardened mortar adhesion rate and bulk porosity of IRCA and JRCA were tested and calculated,and it was found that the reason for the difference in physical properties of the two aggregates was the different adhesion content of the mortar with large open porosity.In addition,through the image acquisition and analysis of IRCA and JRCA,it is found that the circularity and fractal dimension performance of IRCA are better than JRCA.Finally,considering the large difference in particle density between RCA and NCA,this paper will modify the sand ratio in the mix design,and the modified formula is:sp=sp'·(?nk/?rk)(?nk-NCA particle density,?rk-RCA particle density).(2)The basic physical properties of NS-enhanced recycled aggregate show that NS-enhanced has little effect on the open porosity and filling of recycled aggregate.Through XRD and surface SEM characterization of NS reinforced recycled aggregate,it is found that NS reinforced can distribute a looser layer of NS agglomerated particles on the surface of the aggregate.Through the compression test of NS reinforced recycled materials,it is found that the recycled materials prepared by soaking recycled aggregates in 0.5wt%NS dispersion for 6 hours have the best compressive strength improvement effect for 7 days,increasing by 18.8%,and 1wt%NS dispersion soaking recycled bone The 28-day compressive strength of the recycled material prepared with the material 4h has the best improvement effect than that of the unstrengthened group,increasing by 12.8%.Through the effective action ratio test,it is found that when the effective action ratio is in the range of 0.165%-0.227%,the compressive strength in 7 days increases significantly;when the effective action ratio is in the range of 00.165%to 0.298%,the compressive strength in 28 days increases significantly.Combined with the SEM characterization results of recycled materials,it is shown that the reason for the increase in compressive strength of NS reinforced recycled materials is to make the interface gap between recycled aggregate and new mortar smaller.(3)The basic physical properties test of SN-enhanced recycled aggregate shows that SN-enhanced can improve the basic physical properties such as water absorption,particle density and crush value of recycled aggregate by filling the open porosity of recycled aggregate.SEM characterization of SN-strengthened recycled aggregates showed that SN-strengthened can reduce the surface roughness of recycled aggregates and make the surface of aggregates smoother.Tests on the compressive strength of SN recycled materials show that SN strengthening can greatly increase the strength of recycled materials for 7 days.The increase will increase first and then decrease with the increase of SN mass fraction.When the mass fraction of SN solution is 2wt%-4wt%At the same time,the 28-day compressive strength of recycled materials is also significantly improved.Combining the SEM characterization results of SN-strengthened recycled aggregate and recycled materials,when the smoothness of 5wt%SN-strengthened RCA is reached,the interface gap between RCA and newly hardened mortar becomes larger,resulting in a negative increase in 28-day compressive strength of recycled materials. |
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