Research On Bond Properties Between Light Weight Aggregate Concrete And Ordinary Concrete Interface

Lightweight aggregate concrete has been used in high-rise building and longspan bridge more frequently,and draw intensive attention in every country,due to its lightweight,high intensity and good durability.The faying face of these constructions is bond of lightweight aggregate concrete and ordinary concrete.However the research on bond behavior of lightweight aggregate concrete and ordinary concrete has been very rare.The bond behaviors of lightweight aggregate concrete and ordinary concrete were investigated by macro tests and micro tests in this paper.The influence of intensity grade,surfactant,surface roughness and steel fiber on bond behaviors of lightweight aggregate concrete and ordinary concrete has been conducted and analyzed by macro tests,such as splitting tensile strength and rupture strength and so on.The characteristics of interface between lightweight aggregate concrete and ordinary concrete have been studied by test methods of microscopical strength test,scanning electron microscopy,and so on.Furthermore,the bond mechanism of lightweight aggregate concrete and ordinary concrete has been acquired.The results show that: The influence of surfactant on bond behaviors is most remarkable,and the bond behaviors with surfactant are better than that without surfactant,what's more,the affect of sweller,flyash,cement paste and no-surfactant on bond behaviors reduces one by one.The influence of roughness on bond behaviors takes the second position.The results indicate that bond properties become better with greater roughness and higher intensity grade.When steel fiber is joined,the bond behaviors are improved significantly,and the bond strength increases about 32.2%.As the concrete age is over 28 days,time has slight effect on bond behaviors.There is transition region,which is located at interface between cement stone and aggregate in lightweight aggregate concrete,and transition region is the weakest area of concrete structure.Transition region also exists at interface between lightweight aggregate concrete and ordinary concrete,and it is made up of three parts,which are the osmotic layer,reaction layer and gradient layer.Transition region is the weakest area of concrete bond,and reactionlayer determines the bond behaviors.Bonding mechanism of lightweight aggregate concrete and ordinary concrete has been studied by macro tests and micro tests,and the results show that the main factor affecting the bonding is mechanical meshing force,the secondary factor is Van Edward force,and the least factor is chemical force.Engineering evaluation method has been proposed to assess the bond behaviors of lightweight aggregate concrete and ordinary concrete,and the measures of improving bond behaviors have been suggested such as increasing the roughness,suitable surfactant,higher intensity grade,joining steel fiber,bonding rebar and so on.