Mechanical and microscopic properties of dredged sand mortar at different thermostatic time

In order to investigate the characteristics of mortars with different dredged sand admixtures and different thermostatic time, the thermostatic time(4, 8, 12, 16 h)and the dredged sand admixtures(0%, 15%, 50%)were selected as test variables. 15 sets of specimens were prepared for testing using dredged sand instead of mechanism sand from Yangtze River, and the mechanism of the effect of different thermostatic time on the compressive properties and microstructure of mortar with different dredged sand admixtures was analyzed based on the test results. The results show that when the dredged sand admixture is 0% and 50%, the later compressive strength first increases and then decreases with the increase of thermostatic time, and the maximum is at the thermostatic time of 8 h. When the dredged sand admixture is 15%, its compressive strength gradually decreases with the increase of thermostatic time, and the maximum is at the thermostatic time of 4 h. The longer the thermostatic time, the greater the distillation damage, which is unfavorable to the later strength development, and the different change laws under different dredged sand admixtures. With the increase of dredged sand admixture, the later compressive strength first increases and then decreases, and the maximum is at 15% of dredged sand admixture. Dredged sand has a certain optimization effect on the compressive strength of mortar, and dredged sand particles with very small particle size can effectively fill the pore defects in mortar, especially after the distillation damage of mortar. The optimization effect of dredged sand is amplified under the steaming condition, and the compressive strength of dredged sand mortar is further enhanced, and the enhancement of compressive strength of steam curing mortar by dredged sand is much greater than that of standard curing mortar, and the longer the thermostatic time is, the more obvious the enhancement of compressive strength is. When the thermostatic time is 4-8 h and the dredged sand admixture is 15%, the steam-raised dredged sand mortar with the performance not lower than that of pure machine-made sand mortar can be prepared.