Experimental Research On Autogenous Shrinkage Performance Of High-Performance Recycled Concrete Based On Pretreatment Of Recycled Coarse Aggregate

The development of construction industry has made the research and application of recycled concrete become a crucial development direction of civil engineering. At present, although the research about recycled concrete is comparatively sufficient domestically, not enough researches on high-performance recycled concrete were investigated; especially the autogenous shrinkage performance of high-performance recycled concrete was rarely researched and reported. Due to the characteristics of recycled coarse aggregate, the autogenous shrinkage performance of recycled concrete is different from that of ordinary concrete. Therefore, an experiment about the autogenous shrinkage performance of high-performance recycled concrete was performed to improve the autogenous shrinkage performance of high-performance recycled concrete.The results from the experimental work are summarized as follows:1. Recycled coarse aggregate was produced by waste concrete, whose average intensity was C30. Referred to the high-performance way of ordinary concrete, the C40 grade high-performance recycled concrete was configured. The slump of the high-performance recycled concrete is about 200mm, meeting the needs of modern commercial concrete pumping requirements. The basic mechanical properties of high-performance recycled concrete were investigated by the experiment. The results showed that with the increase of replacement rate, the compressive strength and elasticity modulus of recycled concrete showed different degrees of decrease. The compressive strength and elasticity modulus of recycled concrete were improved to different levels when pre-wet), paste wrapped stone secondary mixing or mixing the silica fume paste wrapped stone secondary mixing method were used.2. The autogenous shrinkage of high-performance recycled concrete was measured by the non-contact measurement. The setting of machine integration and non-contact measurement method improved the accuracy and reliability of the test results. Expansion phenomenon of autogenous shrinkage specimen emerged in the early period, and after reaching its peak of the expansion, autogenous shrinkage deformation arose in the concrete. Therefore, the peak point of expansion was selected as the starting point of autogenous shrinkage of concrete, in order to provide better guidance for the engineering practice.3. The influence of different recycled coarse aggregate replacement rates and different pretreatment methods have on the autogenous shrinkage of high-performance recycled concrete was investigated by the experiment.The results showed that with the increase of recycled aggregate replacement rates, autogenous shrinkage of recycled concrete increased. Under the same condition, the autogenous shrinkage of recycled concrete was greater than that of ordinary concrete, particularly early autogenous shrinkage of concrete. Autogenous shrinkage performance was greatly improved when pre-wet methods were taken, and paste wrapped stone secondary mixing method also improved autogenous shrinkage performance with a relatively smaller degree. While autogenous shrinkage increased when mixing the silica fume paste wrapped stone secondary mixing method was used.4. The advantages and disadvantages of autogenous shrinkage prediction models for ordinary high-performance concrete were analyzed and the difference between those models and the paper was compared and analyzed. Based on Eurocode BS EN prediction model, a suitable autogenous shrinkage prediction model for high-performance recycled concrete was established by parameter correction.