Answer only 6.38 6.38 What is the source of fly ash? Why is fly ash sometimes added to concrete?What are the different classes of fly ash?6.39A materials engineer is working in a research project to evaluate the effect ofone type of admixture on the compressive strength of concrete. She tested 10mortar cubes made without admixture and 10 others with admixture after 28days of curing. The compressive strengths of cubes without admixture were25.1, 24.4, 25.8, 25.2, 23.9, 24.7, 24.3, 26.0, 23.8, and 24.6 MPa. The compres-sive strengths of cubes with admixture were 25.3, 26.8, 26.5, 24.5, 27.2, 24.8,24.1, 25.9, 25.3, and 25.0 MPa. Using the statistical t-test, does this admixtureshow an increase in the compressive strength of the cement mortar at a levelof significance of 0.05?

Given : fly ash To determine : 1)source of fly ash 2)Why added in concrete 3)Different class of…

Answered: 6.38 What is the source of fly ash? Why…

6.38 What is the source of fly ash? Why is fly ash sometimes added to concrete? What are the different classes of fly ash?

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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A1-What is the bond strength between steel and conerete and how it can be calculated? 2-What is the segregation of fresh concrete? Give its reason and how to control it? V3- What are the advantages of concrete? 3- Discuss the effect of age and curing on the compressive strength of concrete. 5-What are the main purposes of using plasticizer admixtures? 6-What are the main techniques that should be used to reduce heat of hydration in mass Coti fullowing:
A1-What is the bond strength between steel and concrete and how it can be calculated? 2-What is the segregation of fresh concrete? Give its reason and how to control it? V3- What are the advantages of concrete? 3- Discuss the effect of age and curing on the compressive strength of concrete. 5-What are the main purposes of using plasticizer admixtures? 6-What are the main techniques that should be used to reduce heat of hydration in mass
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
Chapter 13 Question: What is the elasticity of concrete for a normal weight mix (unit weight equal to 150 pcf) with a compressive strength of 5,000 psi? O 3.644 ksi O 4.074 ksi 4,287 ksi O 3.976 ksi O 3,834 ksi
A normal-weight concrete has an average compressive strength of 4500 psi. What is the estimated modulus of elasticity? What is the estimated tensile strength of this concrete?
! 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 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)
A materials engineer is working in a research project to evaluate the effect of one type of admixture on the compressive strength of concrete. He tested eight mortar cubes made with admixture and eight others without admixture after 28 days of curing. The compressive strengths of cubes in psi with and without admixture are shown in Table P6.40.Using the statistical t-test, is there a significant difference between the meansof the compressive strengths of the two cement mortars at a level of signifi-cance of 0.10?
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Mixing and handling can significantly alter the air content of fresh concrete. Thus, field tests are used to ensure that the concrete has the proper air content prior to placing. Air content can be measured with the pressure, volumetric, gravimetric, or Chace air indicator methods. The pressure method (ASTM C231) is widely used, since it takes less time that the volumetric method. The pressure method is based on Boyle's law, which relates Figure 7.13 Consolidating concrete with an internal vibrator. pressure to volume. A calibrated cylinder (Figure 7.14) is filled with fresh concrete. The vessel is capped and air pressure is applied. The applied pressure compresses the air in the voids of the concrete. The volume of air voids is determined by measuring the amount of volume reduced by the pressure applied. This method is not valid for concrete made with lightweight aggregates, since air in the aggregate voids is also compressed, confounding the measurement of the air content of the…
Compressive strength of normal-weight concrete is on average 31 MPa.What is the elasticity modulus expected to be?
6. Discuss the different types of volume change in concrete at early and long-term ages.