Research On The Effect Of Recycled Coarse Aggregate Pretreatment On The Recycled Concrete Slump Loss And Basic Mechanical Property

With the rapid development of industry in China, the quantity of buildingwaste keeps increasing sharply, which poses a threat to the environment. By using abandoned concrete as aggregates can not only save natural aggregates, but also contribute to solve problems caused by littering waste concrete around and environment problem. As a consequence, natural resources and environment can be protected. Fully consider the fact that theporosity and water absorption of recycled coarse aggregates are both higher, the experiment is conducted by taking different pretreat methods to improve the slump loss and basic mechanic performance of recycled concrete.1. The difference between recycled coarse aggregates and natural coarse aggregates is compared by investigating the morphology and basic performance of both of them. The results show that the surface of recycled coarse aggregates concrete is covered by much cement mortar, which results in lower apparent density, higher crush index and water absorption compared with natural coarse aggregates.2. The influence different pretreat methods have on the performance of recycled coarse aggregates is investigated by applying different pretreat methods to recycled coarse aggregates and comparing the result with that of untreated group. The results show that after the pretreat methods were taken, the apparent density increases, and crush index decreases.3. The impact different pretreat methods have on slump loss caused by time elapse is researched and compared with that of untreated recycled concrete. The results show that the methods used in the experiment can lower the slump loss of recycled concrete to some degree. Moreover, it is found that the method when polyvinyl alcohol solution was taken shows lowest slump loss.4. The effect different recycled coarse aggregates pretreat methods have on the basic mechanic performance of recycled concrete is investigated by conducting cube compressive strength, splitting tensile strength and axial compressive strength and modulus of elasticity testfor recycled concrete made by untreated and pretreated recycled coarse aggregates. The results show that the method cement with silicon power grout and PVA solution can improve the basic performance of recycled concrete more.5. The applicability for using conversion relations which are established for the relationship between different basic mechanic performance indexes of normal concrete to recycled concrete is studied. The results show that the interrelationships between the mechanical properties of recycled concrete are different from those of normal concrete. Moreover, new conversion relations suitable for recycled concrete are established bases on regression analysis of the experimental data.