rcd terms Real Exam Questions And Correct Detailed Answers.

is a mixture of water, cement, sand, gravel, crushed rock, or other aggregates. - correct answer concrete Has a high compressive strength and very low tensile strength. - correct answer concrete As a structural member, concrete can be made to carry tensile stress. In this regard, it is necessary to provide steel bars to provide the tensile strength lacking in concrete. The composite member is called ___________. - correct answer reinforced concrete. Aggregates used in concrete may be fine aggregates and coarse aggregates. Fine aggregates are those that pass through No. 4 sieve (about 6 mm in size). Materials retained are coarse aggregates. - correct answer Aggregates According to ________, water used in mixing concrete shall be clean and free from injurious amounts of oils, acids, alkalis, salts, organic materials, or other substances that may be deleterious to concrete or reinforcement. - correct answer Section 403.5 are used to improve the tensile strength of the concrete, since concrete is very weak in tension, but is strong in compression. - correct answer Steel reinforcement bars or rebars is only used as rebar because elongation of steel due to high temperatures nearly equals to that of concrete. - correct answer Steel ADVANTAGES ● Considerable compressive strength ● Great resistance to fire and water ● Very rigid ● Low-maintenance material ● Very long service life ● Economical material available ● Inexpensive local material ● Lower grade of skilled labor is required for erection - correct answer DISADVANTAGES ● Concrete has very low tensile strength, requiring the use of tensile reinforcing. ● Forms are required to hold the concrete in place until it hardens sufficiently. ● The low strength per unit of weight of concrete leads to heavy members. ● Properties of concrete vary widely because of variations in its proportioning and mixing. Deformed and plain billet steel bars : 40,000 psi (280 Mpa); 60,000 psi (420 Mpa), 75,000 psi (520 Mpa); and 80,00 psi (550 Mpa) - load bearing capacity - correct answer ASTM A615 Low-alloy deformed and plain bars; 60,000 psi (420 Mpa) and 80,00 psi (550 Mpa) - ductibility/weldability - correct answer ASTM A706 Deformed rail steel or axle steel bars - railway tracks/industrial structures - correct answer ASTM A996 ends of rebars to provide proper anchorage and bonding - correct answer standard hook _____ degree bend plus 4db extension but not less than 60 mm at free end of bar. - correct answer 180 _____ degree bend plus 12db extension at free end of bar. - correct answer 90 For stirrups and tie hooks: a. _____ diameter bar and smaller, 90 degree bend plus 6db extension at free end of bar, or b. ____ and ____ diameter bar, 90-degree bend, plus 12db extension at free end of bar, or c. ______ diameter bar and smaller, 135-degree bend plus 6db extension at free end of bar - correct answer 16mm 20 and 25 mm 25 mm types of standard hook - correct answer 90- degree hook 135- degree hook 180- degree hook CORROSIVE ENVIRONMENTS - correct answer Deicing Salts - rock salts Seawater Chemical with substance chloride The most important and most critical task of an engineer is the determination of the loads that can be applied to a structure during its life, and the worst possible combination of these loads that might occur simultaneously. Loads on a structure may be classified as ____ or ____ - correct answer dead loads or live loads. ____ are loads of constant magnitude that remain in one position. This consists mainly of the weight of the structure and other permanent attachments to the frame ex. walls, floor, roof - correct answer dead loads _______ are loads that may change in magnitude and position. Live loads that move under their own power are called moving loads. Other live lo