Q.1 Chemical admixtures have been used in the production of concrete to improveits performance in both fresh and hardened states. Discuss the choice ofadmixtures available to impart the specific properties mentioned below. For eachcase, comment on the mode of action, including effects on chemical action,hydration process and properties of the concrete:(a)Construction of heavily reinforced beams,(b) Concreting in cold weathers. Q.4 (a) A new concrete bridge is to be constructed near the sea and its design hasto incorporate features protecting it from exposure to marine environments.Among these, a new coating system is being proposed for concrete. You havebeen awarded a six-month contract to evaluate this system and materialsinvolved. Describe the major parts of your programme, assuming that you alsohave access to a structure on which the coating has recently been used.(b) Aggregate is one of the main materials used in the production of concrete andits physical properties as well as the size distribution can affect the properties offresh and hardened concrete. Discuss the influence of absorption and surfacemoisture conditions of mineral aggregate on fresh and hardened concreteproperties.

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Q.1 Chemical admixtures have been used in the production of concrete to improve its performance in both fresh and hardened states. Discuss the choice of admixtures available to impart the specific properties mentioned below. For each case, comment on the mode of action, including effects on chemical action, hydration process and properties of the concrete: (a) Construction of heavily reinforced beams, (b) Concreting in cold weathers.

Q.1 Chemical admixtures have been used in the production of concrete to improve its performance in both fresh and hardened states. Discuss the choice of admixtures available to impart the specific properties mentioned below. For each case, comment on the mode of action, including effects on chemical action, hydration process and properties of the concrete: (a) Construction of heavily reinforced beams, (b) Concreting in cold weathers.

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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A concrete mix includes the following ingredients per cubic meter: a. Cement = 400 kg b. Water = 176 kg c. No admixture Table P6.30 shows possible changes that can be made to the mix ingredi- ents. 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.
Concrete is strongest when subjected to: O A) Tension O B) Bending O9 Torsion O D) Compression If a peak load of 250 kN was exerted on a 100 mm x 200 mm test cylinder, the compressive strength of the concrete is: OA) 28.6 MPa O B) 35.2 MPa O9 31.8 MPa O D) 32.4 MPa The approximate volume percentages of the principal components of a concrete mixture are: 6%, 11%, 41%, 26%, 16%. Which of the following lists matches the correct order of these main components? Start with the one at 6% and end with the one at 16%. O Air, Water, Coarse Aggregate, Fine Aggregate, Cement O Water, Coarse Aggregate, Fine Aggregate, Cement, Air O Air, Coarse Aggregate, Fine Aggregate, Water, Cement O Air, Cement, Coarse Aggregate, Fine Aggregate, Water Under ideal conditions, concrete should be batched and placed within after mixing, when retarding admixtures are not used. OA 90 minutes O B) 1/2 hour OC 4 hours O D) 120 minutes
Which one of the following sentences is not correct? a.For many years, tensile strength has been measured in terms of the compressive strength. b.The modulus of rupture where the normal-weight concrete has an fc of 4000 psi is 474 psi. c.For lightweight concretes tensile strength depends largely on the porous aggregate. d.For normal weight concrete, the tensile strength depends primarily on the strength of bond between hardened cement paste and aggregate.
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
Concrete is required for a column that will be moderately exposed to freezing and thawing. The cross section of the column is 300 × 300 mm. The smallest spacing between reinforcing steel is 30 mm. The specified compressive strength of concrete at 28 days is 40 MPa with a slump of 80 to 100 mm. The properties of materials are as follows: ❖ Cement used is type I Portland cement with a specific gravity of 3.15. ◆ The available coarse aggregate has a maximum size of 23 mm, a dry-rodded unit weight of 1800 kg/m3, a bulk specific gravity (SSD) of 2.7, absorption capacity of 0.55%, and moisture content (SSD) of 0.25%. The fine aggregate has a bulk specific gravity (SSD) of 2.75, absorption capacity of 1.4%, a moisture content (SSD) of 2.5%, and a fineness modulus of 2.70. The aggregates conform to the ASTM C33-84 requirements for grading.
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Concrete is required for a column that will be Severe exposed to freezing and thawing. The cross section of the column is 300 × 300 mm. The smallest spacing between reinforcing steel is 30 mm. The Required Average Compressive Strength of concrete at 28 days is 35 MPa with a slump of 80 to 100 mm. The properties of materials are as follows: ❖ Cement used is type I Portland cement with a specific gravity of 3.15. ◆ The available coarse aggregate has a maximum size of 23 mm, a dry-rodded unit weight of 1800 kg/m3, a bulk specific gravity (SSD) of 2.7, absorption capacity of 0.55%, and moisture content (SSD) of 0.25%. The fine aggregate has a bulk specific gravity (SSD) of 2.75, absorption capacity of 1.4%, a moisture content (SSD) of 2.5%, and a fineness modulus of 2.70. The aggregates conform to the ASTM C33-84 requirements for grading.
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 calculated strength, not the given strength).
Q.1 Chemical admixtures have been used in the production of concrete to improve its performance in both fresh and hardened states. Discuss the choice of admixtures available to impart the specific properties mentioned below. For each case, comment on the mode of action, including effects on chemical action,hydration process and properties of the concrete:(a) Construction of heavily reinforced beams,(b) Concreting in cold weathers.
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4b. Deformation occurs on freshly lay concrete when it finally set or harden.discuss the various causes for dimensional changes in the hardened concrete.
Concrete is required for walls of a building that will be Mild Exposed to freezing and thawing. The cross section of a wall is 300 x 1500 mm. The smallest spacing between reinforcing steel is 50 mm. The specified compressive strength of Compressive strength of concrete at 28 days is 35 MPa and a slump of 55 mm. Portland cement type I is used with specific gravity of 3.12, maximum size of aggregate 27 mm and fineness modulus of fine aggregate is 2.4, absorption capacity and moisture content of fine aggregate are of 0.92%, and 1.95% respectively. The dry-rodded unit weight of coarse aggregate is 1820 kg/m³, absorption capacity and moisture content of coarse aggregate are of 0.75%, and 1.85% respectively. Both aggregates have a bulk specific gravity (SSD) of (2.45). The aggregates conform to the ASTM C33-84 requirements for grading. Estimate the quantity of (cement, fine aggregate, coarse aggregate and water) for 1m³ concrete.