Experimental Investigation On Preparation And Mechanical Properties Of Metal Hollow Sphere Cement Composites

Concrete is one of the most important civil engineering materials,with the development of society,people put forward new requirements for concrete,need concrete at the same time with more performance,such as light weight,high strength,heat insulation,good impact resistance and so on.At the same time,the metal hollow sphere composite is a research hotspot in the field of materials in recent years,which has excellent properties such as ultra-light,high specific strength,high specific stiffness,high toughness,high energy absorption and so on.Metal hollow ball composites make up for the shortcomings of concrete performance,and concrete as the matrix of metal hollow ball composites can reduce the manufacturing cost of metal hollow ball composites.Therefore,in this study,Metal Hollow Sphere Cement Composite（MHSCC）with two diameters（16mm and 19mm）was developed by Composite with concrete matrix.The static and dynamic mechanical properties of MHSCC were studied,and the influence of different diameter and dosage of hollow metal spheres on the mechanical properties of MHSCC was discussed.The effect of polypropylene fiber on the static and dynamic mechanical properties of MHSCC was investigated.On this basis,combined with the macroscopic failure mode of the sample,the failure mechanism of MHSCC was revealed.The main contents and conclusions of this project are as follows:（1）Based on the working performance of the concrete matrix and the delamination degree and compressive performance of the hollow metal spheres,the MHSCC matrix proportion optimization was carried out.The fluidity of the matrix was obtained from 130 mm to 140 mm,and the delamination degree was less than 10% after the hollow metal spheres were added.And the prepared MHSCC has better compressive strength of concrete matrix mix.（2）The statics performance of MHSCC under different diameter and dosage of hollow metal spheres was studied.A total of 13 groups of 39 cubic specimens with sizes of 100mm×100 mm×100 mm were tested for MHSCC statics performance.In order to investigate the influence of metal hollow spheres diameter（16mm and 19mm）,dosage（0%,10%,20%and 30%）on the static compression performance of MHSCC.The results show that the compressive strength,elastic modulus and compressive toughness of MHSCC decrease with the increase of the content of hollow metal spheres due to the weak zone of the interface,and the decrease range of 16 mm hollow metal spheres is lower than that of 19 mm hollow metal spheres.The peak strain and energy absorption rate of MHSCC increase with the increase of metal hollow sphere content.The results also show that the addition of certain fibers can effectively improve the brittleness of MHSCC,and improve the compressive strength,peak strain,elastic modulus and compressive toughness of MHSCC.（3）The impact resistance of MHSCC with different metal hollow ball diameters（16mm and 19mm）,different dosage（0%,10%,20% and 30%）and 0.5% polypropylene fiber was studied.A total of 39 groups of 117 MHSCC cylinder samples with dimensions of ф 100mm×50 mm（diameter × height）are subjected to dynamic compression tests under different impact loads（0.3 MPa,0.5 MPa and 0.7 MPa）,and the strain rate effect was analyzed.The results show that the Dynamic compressive strength,compressive impact toughness and Dynamic Increase Factor（DIF）of MHSCC samples show obvious strain rate effect.Under the same strain rate,the dynamic compressive strength of MHSCC mixed with 10% and20% hollow metal spheres is higher than that of the concrete matrix without hollow metal spheres.The dynamic compressive strength of MHSCC mixed with 10% hollow metal spheres is the largest increase,and the increase of the dynamic compressive strength of MHSCC mixed with 16 mm hollow metal spheres is greater than that of concrete mixed with19 mm hollow metal spheres.Under similar strain rates,the impact toughness and DIF of MHSCC are higher than those of concrete without metal hollow spheres.In addition,adding fiber can effectively improve the dynamic compressive strength,impact toughness and DIF value of the sample.（4）Through the macroscopic failure mode analysis of the sample,the change rule of the failure mode of MHSCC under different metal hollow sphere diameter and dosage conditions with or without fiber reinforcement was explored,and the failure mechanism of MHSCC under dynamic and static loading was revealed.The macroscopic failure mode analysis of the samples shows that the failure degree of the MHSCC sample increases with the increase of the content of hollow metal spheres in the static loading,which is caused by the increase of the weak zone at the interface.After the addition of fibers,it becomes ductile failure and the failure degree decreases,which is mainly attributed to the good bridge and inhibition effect of fibers on cracks.At the same time,only a small part of metal hollow spheres in the sample were damaged,and the damage degree and quantity of 19 mm diameter metal hollow spheres were larger than 16 mm metal hollow spheres.Under the impact load,the damage severity of the sample increases with the increase of the impact load.MHSCC damage will increase with the increase of dosage of metal hollow balls,and mixed with 10%and 20% of hollow metal ball in the same damage under the shock pressure is less than the concrete substrate damage,this is because the metal hollow balls in the MHSCC after receiving part to absorb energy when the shock load,thus protecting the integrity of the sample.In addition,the fiber incorporation can improve the deformation ability of MHSCC,effectively reduce the damage degree of the sample,and improve the impact resistance of MHSCC.