25. Which kinds of concrete mixing water should be used?
Fresh water, tap water, groundwater, drinking water, recycled water, mixing station car washing water (part of mixing). Industrial waste water, domestic waste water and seawater shall not be used.
26. What is the meaning of the word concrete? How do you pronounce it?
The meaning is man-made stone, representing concrete. Lexicographically pronounced tong, you can also pronounce hun ning tu.
27, what is the role of expansion agent?
A: The expansion agent into the cement and cement hydration chemical reaction to produce ettringite and other substances, increase the concrete compactness, at the same time the volume of micro expansion, reduce the shrinkage of concrete, play the role of crack and seepage resistance.
28, according to the strength of concrete divided into several grades? How is it divided?
A: There are 13 grades in total according to the strength of concrete: C10, C15, C20, C25, C30, C35, C40, C45, C50, C55, C60, C70 and C80. Its grade is based on the strength of standard curing 28d of concrete standard test block, at intervals of 5MPa or 10MPa. C is a capital letter of the English word for concrete, which stands for concrete, and the numbers in the corner indicate the strength level.
29, according to the performance of concrete into which?
A: Divided into ordinary concrete, high strength concrete (greater than C50), impervious concrete, pumped concrete, anti-freeze concrete, anti-freeze concrete, mass concrete, non-vibrating concrete (self-leveling concrete), dry hard concrete, high performance concrete.
30. What unit does MPa mean and how to convert it?
A: MPa is the unit of strength: 1MPa=106Pa,1Pa=1N/m2, and 1MPa=1N/mm2. 1MPa≈10kg/cm2.