Dynamic Mechanical Properties Of Ultra High Toughness Cementitious Composites Under Compressive Experimental Study

As a new type of high performance building material,the ultra-high toughness cementitious composites(UHTCC)has attracted extensive attention because of the excellent properties that can overcome the poor toughness of the concrete and difficulties of controlling crack width.At present,the researches on the performance of UHTCC are mostly focused on quasi static,but the studies on dynamic mechanical performance are very little.Many engineering structures are under the condition of dynamic load,so the performance of UHTCC materials under dynamic load become the key that the application in these structures can reach the good expectation or not.In order to have a more comprehensive grasp of the performance of UHTCC and provide the scientific basis for engineering application,in this thesis,a series of researches on the dynamic axial compression performance of UHTCC are carried out:1.The thesis has studied the effects of fiber content,strain rate on dynamic compressive strength,strain under peak stress,elastic modulus and Poisson's ratio of UHTCC under low strain rate.The results show that UHTCC is a rate dependent material;the compressive strength of UHTCC increase as the strain rate increasing;the fiber content has a certain effect on the rate dependence of compressive strength of UHTCC,and the elastic modulus increases with the increase of strain rate;2.The thesis has researched the effects of humidity,fiber content and strain rate on the dynamic compressive properties of UHTCC.The results show that the humidity,strain rate and the fiber content can not only have effects on the dynamic compressive properties of UHTCC but have some relationships to each other.What's more,the humidity and matrix show a weakening effect on the dynamic compressive strength of UHTCC;the humidity has no effect on strain under peak stress and Poisson's ratio of UHTCC,but shows some effects on the elastic modulus;3.The thesis has studied the effects of fiber content,moisture content and strain rate on the mechanical properties of UHTCC under axial compression.The results show thatboth saturated humidity and dry UHTCC have rate dependence under the medium strain rate.Second,the compressive strength of saturated humidity and dry UHTCC increase as the increase of strain rate.Both saturated humidity and dry UHTCC have an optimal fiber content that can make the UHTCC reach maximum compressive strength.the humidity has enhancement effect on the strain under peak stress of UHTCC,and it often decreases with the strain rate increasing;Through the experiments,it can be concluded that the UHTCC is a rate dependent material.Strain rate,fiber content and humidity have influences on the dynamic compressive properties.The study of UHTCC are beneficial to promote the use of UHTCC to water conservancy facilities such as breakwaters,dams and provide references for the performance parameters of water conservancy facilities.Accordingly,the thesis can do some help promote the development of UHTCC applications.