Civil and Environmental Engineering Answers

find the centroid of the area bounded by the curves y^2=x and x=4

Design the concrete mix according to the following conditions:

Design Environment

Building frame

Required design strength = 27.6 MPa

Minimum dimension = 150 mm

Minimum space between rebar = 40 mm

Minimum cover over rebar = 40 mm

Maximum slump is required

Statistical data indicate a standard deviation of compressive strength of 2.1 MPa is

expected (more than 30 samples).

Only air entrainer is allowed.

Available Materials

Air entrainer: Manufacture specification 6.3 ml/1% air/100 kg cement. (Use maximum

or +2% air content)

Coarse aggregate: 19 mm nominal maximum size, river gravel (rounded)

Bulk oven-dry specific gravity = 2.55, Absorption = 0.3%

Oven-dry rodded density = 1761 kg/m³

Moisture content = 2%

Fine aggregate: Natural Sand

Bulk oven-dry specific gravity = 2.6

The design of a concrete mix requires 1173 kg/m3

of gravel in dry condition, 582 kg/m³ of sand in dry condition, and 157 kg/m³of free water. The gravel available at the job site has a moisture content of 0.8% and absorption of 1.5%, and the available sand has a moisture content of 1.1% and absorption of 1.3%. What are the masses of gravel, sand, and water per cubic meter that should be used at the job site?

What is your recommendation for the maximum size of coarse aggregate for the following situation? A continuously reinforced concrete pavement cross section contains a layer of No.6 reinforcing bars at 6-inch centers, such that the steel is just above mid-depth of a 10-inch￾thick slab. Cover over the top of the steel is therefore about 4 inches.

A project specifies a concrete strength of at least 3000 psi. Materials engineers will design

the mix for a strength higher than that. Calculate the required average compressive strength of

the mix design if the standard deviation is s = 350 psi. Estimate the modulus of elasticity of the

concrete at the required average compressive strength.

A project specifies a concrete strength of at least 3000 psi. Materials engineers will design

the mix for a strength higher than that. Calculate the required average compressive strength of

the mix design if the standard deviation is s = 350 psi. Estimate the modulus of elasticity of the

concrete at the required average compressive strength.

The design engineer specifies a concrete strength of 5500 psi. Determine the required

average compressive strength for:

a. A new plant where s is unknows

b. A plant where s = 500 psi for 22 test results

c. A plant with extensive history of producing concrete with s = 400 psi

d. A plant with extensive history of producing concrete with s = 600 psi

A rectangular box with a square base and no top is to have a volume of 108 cubic inches. Find the dimensions for the box that require the least amount of material.

What vector type ( point, line, or polygon) best represents the following features; state boundaries,cities,stream networks,mountain peaks,soil types, flight tracks. Which of the above features may be represented by multiple vector type ? And what conditions may lead you to choose one vector over the other