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The density of pebble material is 2.65, the apparent density is 2.61, and the bulk density is 1680?
Porosity: 1-2.61 / 2.65 = 1.5% (closed porosity); porosity: 1-1680 / 2610 = 35.6%
A problem of measuring the density of pebbles
A tray balance, a beaker, thin line, small stones to be measured, water
Use the above items to measure the density of pebbles to be tested (no additional equipment is allowed)
F = density of water * g * V (formula 1)
1. Direct pebble mass of balance: M = pebble density * V (formula 2)
2. Use a balance to weigh the mass m of the beaker with proper amount of water, use a thin line to tie the pebbles, immerse them in the beaker (hold the thin line by hand, do not let the pebbles touch the beaker), and weigh the total mass M. then f floating = M-M (formula 3)
According to Formula 1, 2 and 3, the density of pebbles is calculated
Calculation of water cement ratio with the density of slump, sand and stone
It is known that the design strength is C20, the material used is 425 slag cement, medium sand (density is 2.62g / cubic centimeter), the maximum particle size of crushed stone is 40mm (density is 2.65g / cubic centimeter), mechanical mixing, vibrator vibration, slump selected 30-50mm, and the water cement ratio of design concrete is determined?
After calculation, the water cement ratio is 0.742
FCU, o = FCU, K + 1.645 * variance
fcu,o=20+1.645*5=28.225
Water cement ratio = 0.46 * 42.5 * 1.13 / (28.225 + 0.46 * 0.07 * 42.5 * 1.13) = 22.0915/29.771405 = 0.742
The regression coefficient is 0.46 and 0.07, and the surplus coefficient is 1.13, which can be determined according to the actual statistical data
You can query jgj55 for the above parameters. I just give an example
There is a cuboid wood with a volume of 720 cubic decimeters. If after cutting off a section, what's left is a cube with an edge length of 6 decimeters. What's the surface area of the original cuboid wood?
6 × 6 = 36 (square decimeter), 720 △ 36 = 20 (decimeter), 6 × 4 × 20 + 6 × 6 × 2, = 480 + 72, = 552 (square decimeter); answer: the original surface area of cuboid wood is 552 square decimeter
A cuboid wood, saw a volume is 75 cubic decimeters of small cuboid, the remaining edge length of 5 decimeters cube, the original cuboid surface area
Formula, thought
The cross-sectional area of the cuboid is 5 * 5, and its length is 75 / (5 * 5) = 3 decimeters;
The original cuboid is 3 + 5 = 8 decimeters long, 5 decimeters wide and 5 decimeters high,
Its surface area is 4 * 8 * 5 + 2 * 5 * 5 = 210 square decimeters
After cutting a cuboid with a volume of 8 cubic decimeters from one end of a cuboid, a cuboid with an edge length of 10 cm is left, which is the surface area of the original cuboid
How much is it!
8 cubic decimeter = 8000 cubic centimeter
It turns out that the bottom area of the cuboid is
10 × 10 = 100 (square centimeter)
The lower part of the cuboid is truncated
8000 △ 100 = 80 (CM)
What is the length of the cuboid
80 + 10 = 90 (CM)
It turns out that the surface area of the cuboid is
(90 × 10 + 90 × 10 + 10 × 10) × 2 = 3800 (cm2)
A cuboid wood (as shown in the figure), after cutting off a small cuboid with a volume of 72 cubic decimeters, the remaining part is just a cube with an edge length of 3 decimeters. Calculate the surface area of the original cuboid
Original length: 72 (3 × 3) + 3 = 8 + 3 = 11 (decimeter), surface area: 11 × 3 × 4 + 3 × 3 × 2 = 132 + 18 = 150 (square decimeter); answer: the surface area of the original cuboid is 150 square decimeter
A cuboid wood, cut off a volume of 72 cubic decimeters of small cuboid, the remaining part is just a cube with an edge length of 6 decimeters
What's the surface area of the cuboid?
6x6x8x4 + 6x6x2 = 1224 square decimeters = 122400 square centimeters
A cuboid wood (as shown in the figure), after cutting off a small cuboid with a volume of 72 cubic decimeters, the remaining part is just a cube with an edge length of 3 decimeters. Calculate the surface area of the original cuboid
Original length: 72 (3 × 3) + 3 = 8 + 3 = 11 (decimeter), surface area: 11 × 3 × 4 + 3 × 3 × 2 = 132 + 18 = 150 (square decimeter); answer: the surface area of the original cuboid is 150 square decimeter
A cuboid of wood, cut a volume of 48 cubic decimeters cuboid, get a cube, the cube edge length is 2 mm
The ball is the original volume of the wood
2×2×2＋48
=8＋48
=56 cubic decimeter
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