Concrete slump detection
1. Standard slump cylinders, bullet-type rams, shovels, rulers, trowels, scales, etc. made of metal materials for experimental tools.
2. Experimental procedure
(1) Wet the slump cylinder and other utensils, and place the cylinder on a rigid horizontal plate that does not absorb water, and step on the foot pedal with your feet to keep the slump cylinder in a fixed position when loading. (2) Load the concrete sample into the cylinder in three layers, so that the height of each layer after tamping is 1/3 of the height of the cylinder.
Each layer is tamped 25 times with a vibrating rod, vibrating and tamping is carried out spirally from the outward center, evenly distributed. The bottom layer should be vibrated to the end, and the other two layers should be inserted into the surface of the lower layer. The concrete on the top layer should be higher than the mouth of the cylinder. If the concrete is lower than the mouth of the cylinder during vibration, it should be added at any time. After the top layer is tamped, scrape the excess concrete and smooth it with a spatula.
(3) After removing the concrete on the bottom plate of the cylinder, lift the slump cylinder vertically and steadily. The lift-off process is completed in 5-10 seconds. It should be carried out continuously from loading to the lifting drum, and completed within 150 seconds.
(4) After lifting the slump cylinder, the difference between the height of the cylinder and the height of the concrete specimen after the slump is measured is the slump value of the concrete mixture. After the slump tube is lifted off, if the concrete collapses or shears on one side, it should be re-sampled and measured separately. If the above phenomenon still occurs in the second test, it means that the concrete is not easy to handle and should be recorded for future reference. . (5) Observe the cohesiveness and water retention of concrete: