Concrete Knowledge 100 Questions (6)

31, concrete mix main test which several performance?

A: It mainly tests the workability, slump and gas content of the mixture. Workability is represented by cohesiveness, water retention, fluidity and comprehensive expression.

(1) cohesiveness - by eye observation, when the slump is done, the test body slumps to the surrounding area for good cohesiveness, the test body collapses to one side or part of the stone leaks outside, and the non-cohesive mortar on the surface for poor cohesiveness.

(2) Water retention - After the concrete mix is loaded into the slump cylinder and rammed, the bottom of the cylinder has a little dilute slurry or no good water retention. If the concrete mix is poured on the iron plate, there is water or cement slurry precipitation on the surface, indicating poor water retention (that is, segregation phenomenon).

(3) Liquidity -- good liquidity is good when the mixture is piled up and flowing around immediately, and bad liquidity is bad.

32. What is concrete slump?

Answer: The slump cylinder is placed on the iron plate, loaded into the concrete mix and compactness, and then vertically lift the slump cylinder, the concrete test body slumps down, measuring the distance between the top of the cylinder and the test body is the slump. The slump of ordinary concrete is 30 ~ 90mm. The slump of pumping concrete is between 100 and 230 mm. The higher the pumping height is, the greater the slump is, and the smaller the slump is.

33. What is the expansion degree of concrete?

Answer: When the slump of concrete is greater than 220mm, the steel ruler is used to measure the considerable diameter and considerable small diameter of the expanded concrete mix, and the average value is the expansion degree. The larger the expansion, the better the flow. Self-leveling concrete should measure its expansion degree.

34. What does the segregation of concrete mix look like?

A: If it is found that there is cement slurry flowing from the edge of the concrete mix. After a few minutes, the sand and stone sink, forming the phenomenon of bottom grabbing is the segregation of the concrete mix. Segregation is a poor performance of concrete workability, easy to block pipe when pumping, and will reduce the strength of concrete. Segregation phenomenon is often caused by excessive mixing of pumping agent, which can be reduced by 0.2%.

35, sometimes concrete mix will appear part of the stone non-stick mortar, or like bean curd slag non-stick what is the reason?

Answer: Some of the stone non-stick mortar is due to the pumping agent mixed with less viscosifying components caused by. The state of bean curd slag is the result of the incompatibility between the pumping agent and a certain component of the cement.

36. What is a standard test block?

A: The test block with a side length of 150mm×150mm×150mm is a standard test block. The test block with a side length of 100mm×100mm×100mm is a non-standard test block, and the result after compression should be multiplied by 0.95 conversion factor to convert the strength of the standard test block.