The characteristic compressive strength of concrete required in a project is 25 MPa and the standard deviation in the observed compressive strength expected at site is 4 MPa. The average compressive strength of cubes tested at different water-cement (w/c) ratios using the same material as is used for the project is given in the table. w/c(%) Average compressive strength of cubes (MPa) 45 35 50 25 55 60 20 15 The water-cement ratio (in percent, roundoff to the lower integer) to be used in the mix is

The characteristic compressive strength of concrete required in a project is 25 MPa and the standard deviation in the observed compressive strength expected at site is 4 MPa. The average compressive strength of cubes tested at different water-cement (w/c) ratios using the same material as is used for the project is given in the table. w/c(%) Average compressive strength of cubes (MPa) 45 35 50 25 55 60 20 15 The water-cement ratio (in percent, roundoff to the lower integer) to be used in the mix is

Structural Analysis

6th Edition

ISBN:9781337630931

Author:KASSIMALI, Aslam.

Publisher:KASSIMALI, Aslam.

Chapter2: Loads On Structures

Section: Chapter Questions

Problem 1P

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What is the effect of water–cement ratio on the permeability of hardened concrete? How does permeability affect the durability of the concrete structure?Using Figure 7.33, what is the approximate percent increase in the coefficientof permeability if the water–cement ratio increases from 0.5 to 0.6? Using thesame figure, what is the approximate percent increase in the coefficient ofpermeability if the water–cement ratio increases from 0.5 to 0.7?
2. In a ready-mix concrete plant, cylindrical samples are prepared and tested periodically to detect any mix problem and to ensure that the compressive strength is higher than the lower specification limit. The minimum target value was set at 5,000 psi. The following compressive strength data were collected. Sample No. 1 2 3 4 5 6 7 8 9 10 Compressive strength (psi) 5595 5139 6359 5192 5188 5241 5964 5875 6155 5115 Sample No. 11 12 13 14 15 16 17 18 19 20 Compressive strength (psi) 6695 5449 5278 6697 5195 6021 5320 5657 6595 5235 a. Calculate the mean, standard deviation, and the coefficient of variation of the data b. Using a spreadsheet program, create a control chart for these data showing the target value and the lower specification limit. Is the plant production meeting the specification requirement? If not, comment on possible reasons. Comment on the data scatter.
A concrete mix includes the following ingredients per cubic meter: Cement%3D400 kg Water=184 kg No admixture Table below shows possible alternatives mix ingredients. Indicate in the appropriate boxes in the table what will happen in each case for the workability and the ultimate compressive strength as increase, decrease or approximately the same. What will happen? Cement Water Admixture (kg) (kg) Ultimate compressive Workability strength 400 225 None 449 184 None Water 400 184 Reducer Water 400 128 Reducer 400 184 Super Plasticizer 400 184 Air Entrainer 400 184 Accelerator DFocus
The results of a laboratory experiment to evaluate the effects of a plasticizer are shown.a. Calculate the water/cement in each of the three cases. b. Choose an appropriate case that - by using water reducer, how can we increase the compressive strength of concrete without changing workability? (Refer to the appropriate case in the table) c. Choose an appropriate case that - by using a water reducer, how can we improve workability without changingthe compressive strength? (Refer to the appropriate case in the table)d. Choose an appropriate case that - by using water reducer, how can we reduce cost without changing workability or strength? (Refer to the appropriate case in the table)
Three 100*200 mm cylindrical concrete specimens were tested for 28 days compressive strength and show 30.5 MPa, 29.6 MPa and 32.8 MPa compressive strength. a) What is the average compressive strength of this concrete? b) What is the approximate tensile strength of this concrete? c) What is the approximate modulus of elasticity of this concrete? For the toolbar, press ALT+F10 (PC) or ALT+FN+F10 (Mac). BIU Paragraph Arial 10pt A v x² X, +, 田用国田用因 Ť } !!
Correctly define which of the stress versus strain graphs represent the comparison of 8 ksi and 4 ksi concrete for the chart below (say left or right). Qualitatively compare the w/c ratio, elastic modulus, and brittleness. 0.000 0.003 0.000 0.003 Sean, e Sane Feure 2 Strss vesus Srain curves Feure 2. Stress vasus rain curve
Q3: B: 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 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. Coarse aggregate: 19 mm nominal maximum size, river gravel (rounded) Bulk oven-dry specific gravity = 2.55, absorption = 3.6, Oven-dry rodded density = 1761 kg/m3 %3D Moisture content = 2.5, Fine aggregate: Natural sand Bulk oven-dry specific gravity 2.659, absorption=0.5, Moisture content = 2, Fineness modulus = 2.47
12. A normal-weight concrete has an average compressive strength of 20 MPa. What is the estimated flexure strength? What is the estimated tensile strength?
! Three 150 mm x 300 mm concrete cylinders with randomly oriented steel fiber contents of 0, 2, and 3% by weight, respectively. After curing for 28 days, the specimens were subjected to increments of compressive loads until fail- ure. The load versus deformation results were as shown in Table P11.14. TABLE P11.14 Specimen No. Fiber Content (%) 1 2 3 2 Deformation (mm) Load (kN) 0.31 565 565 565 0.61 716 (failure) 756 792 0.91 641 756 1.22 440 690 1.52 378 641 1.83 351 (failure) 605 (failure) Assuming that the gauge length is the whole specimen height, determine the following: a. The compressive stresses and strains for each specimen at each load increment. b. Plot stresses versus strains for all specimens on one graph. c. The modulus of elasticity for each specimen. d. The ultimate strength for each specimen. e. The strain at failure for each specimen. f. Toughness. Curves may be approximated with a series of straight lines. g. Comment on the effects of increasing the fiber content on…
The characteristic compressive strength of concrete required is a project is 25 MPa and standard deviation in the observed compressive strength expected at site is 4 MPa. The average compressive strength of cubes tested at different water-cement (w/c) ratios using the same material as is used for the project is given in the table. Water content (%) 45 50 55 60 Average compressive strength of cubes (MPa) 35 25 20 15 20 15 The water-cement ratio (in percent, round off to the lower integer) to be used in the mix is
Three 150 mm * 300 mm concrete cylinders with water to cement ratios of 0.4, 0.6, and 0.8, respectively. After curing for 28 days, the specimens were subjected to increments of compressive loads until failure. The load versus deformation results were as shown in Table .Assuming that the gauge length is the whole specimen height, it is required to do the following:a. The compressive stresses and strains for each specimen at each load increment.b. Plot stresses versus strains for all specimens on one graph.c. The ultimate strength for each specimen.d. The modulus of elasticity as the secant modulus at 40% of the ultimate stress for each specimen. e. The strain at failure for each specimen.f. The toughness for each specimen. g. Comment on the effect of increasing the water–cement ratio on the following:i. Ultimate strengthii. Modulus of elasticityiii. Ductilityiv. Toughness. Curves may be approximated with a series of straight lines.
.The characteristic compressive strength of concrete required in a project is 25 MPa and standard deviation in the observed compressive strength expected at site is 4 MPa. The average compressive strength of cubes tested at different water-cement (w/c) ratios using the same material as is used for the project is given in the table. w/c (%) Average compressive strength of cubes (MPa) 45 50 55 60 35 25 20 15 The water-cement ratio (in percent, round off to the lower integer) to be used in the mix