Study On Mechanical Properties And Microstructure Of Alkali Activated Recycled Concrete And Its Mix Design

So many problems occurred by extensive using of the traditional Portland cement concrete such as construction waste pollution and too much CO2 emissions.Based on the current situation, the thesis proposed the idea that using recycled coarse aggregate instead of natural stone material to combined with alkaline activated cementing materials completely to create a new type of concrete which are called alkaline activated recycled concrete. The researches or applications of alkali activated concrete are mostly limited in natural aggregate concrete at home or abroad, then this paper studies the alkaline activated concrete which use recycled coarse aggregate completely in special. The exploration of the relationship between macro performance and influencing factors of this concrete is conducted by the way of transition based on cementing materials. Furthermore, we proposed the formulation about W/GPS(the ratio of the total mass of water to geopolymer solid) and compressive strength as well as a mix design method with reference to ordinary Portland cement concrete in order to fill the gaps in using coarse aggregate into alkaline activated concrete completely.This paper mainly completed the following works in realization of this concrete and researching on relative performance:Firstly,it proposes a new indicator A/B(the ratio of the total mass of Alkaline liquid to Binder) based on existing research and studied the relationship between performance and influencing factors by taking the two important indicates(W/GPS and A/B) as entry point. It proposed an appropriate range about proportion of alkaline activated cementing materials and then transition to cor-relational studies about concrete.Secondly,it explored the interface between the coarse aggregate and cementing materials by means of Micro-technology(X-CT,SEM-EDX and so on) and pay attention to the features of interface included close degree of combination, micro-structure, element composition, pore distribution and so on at the different value of A/B or different composition of mineral substance.Then we have get some information about the reaction mechanism about alkaline activated cementing materials and made a foundation of controlling the performance of this concrete in essence.Thirdly, it proposed the formulation about W/GPS and compressive strength by using the experimental data and then established a mix design method which regard compressive strength as a target with reference to ordinary Portland cement. Additionally, we have examined the accuracy of this method by experiment.At last, emphasis is placed on transition zone and its contribution to concrete and the failure mechanism of this concrete. The thesis compared main concrete performances in different types of aggregate(natural and recycled)and different mineral composition respectively when we keep a constant mix proportion. Otherwise,we got the optimal value of A/B based on compressive strength, and proposed the appropriate range of some indicators included sand ratio and the ratio of the mass of binder to aggregates.