1. The full form of ACI method for mix design proportion is __________
a) American committee institute
b) American council institute
c) American concrete institute
d) American cement institute
Explanation: American concrete institute’s mix design procedure for no slump is one of the methods used for high strength concrete mix design and the American concrete institute in a non profit technical society and standards developing organization, ACI was founded in January 1905.
2. In which method, high strength concrete mixes are designed by relating compressive strength to reference number?
a) Erntroy and Shack locks
b) American concrete institute method
c) British DOE method
d) Indian standard code method
Explanation: In Erntroy and Shack lock’s empirical method high strength concrete mixes are designed by using empirical graphs relating the compressive strength to reference number for concrete made with crushed Granite, coarse aggregates and irregular gravel and the range of the degrees of workability varying from externally low to high corresponds to the compacting factor values of 0.65 and 0.95.
3. The water cement ratio used for British DOE method is ___________
a) 0.7
b) 0.5
c) 0.9
d) 0.7
Explanation: In British DOE method based on the type of cement and coarse aggregate provided evaluate the compressive strength of concrete mix made with water cement ratio of 0.5 and the durability requirements of mix design. Doe is design of experiments is a methodology that can be effective for general problem solving as well as for improving or optimizing product design and manufacturing and production process.
4. The degree of workability of Indian standard method is ___________
a) 0.80
b) 0.50
c) 0.60
d) 0.20
Explanation: The degree of workability relating to compaction factor value is 0.80 for Indian standard method design for high strength concrete mix, the steps involved in Indian standard method is target mean strength, water cement ratio, maximum size of aggregates, degree of workability, considering all the factors the cement content is obtained
5. The ultimate strength of high tensile steel is ___________
a) 1100
b) 2100
c) 1500
d) 1250
Explanation: High tensile steel are commonly used in prestressed concrete members and ultimate strength of high tensile steel is equal to 2100n/mm2, therefore the losses of prestress due to shrinkage and creep with a stress of 200n/mm2 are restricted.
6. The high tensile steel is obtained by increasing content of ___________
a) Carbon content in steel
b) Aluminium content in steel
c) Manganese content in steel
d) Sulphur content in steel
Explanation: High tensile steel is required in prestressed concrete member and it is obtained by increasing the carbon content in steel and the percentage of carbon is 0.6-0.85%, 0.7-1% of manganese, 0.05% of sulphur and phosphorus is present in high tensile steel.
7. The properties of cold-drawing through wires can be improved by heating at ___________
a) 100-320 degrees
b) 130-400 degrees
c) 150-480 degrees
d) 120-380 degrees
Explanation: As per IS:1785-1983, the nominal size of cold drawn stress are 2.5, 3, 4, 5, 7 and 8mm diameter and to improve the properties of wire, they have to be tempered by heating the wires at 150 to 480 degrees, which enhances tensile strength
8. Hard-drawn steel wires used in high tensile steel are considered as ___________
a) Crimped elements
b) Twisted elements
c) Durable elements
d) Tempered elements
Explanation: As per IS: 6003-1983, the diameter of wires are mostly used in strands of two, three or seven wires and they are considered as indented or crimped pretensioned element, due to their superior bond character and two and three ply strands, 2-3mm diameter wires are used whereas in 7 ply stand a diameter of 2-5mm wires are adopted and the nominal diameter of 7 ply stand varies in between 6.3 to 15.2mm.
9. The atomic hydrogen is liberated as a result of the action of ___________
a) Sulphur
b) Manganese
c) Acids
d) Stresses
Explanation: Atomic hydrogen is liberated as a result of the action of acids on high-tensile steel and they penetrate into the steel surface making it brittle and fracture prone on being subjected to tensile stress and even small amounts of hydrogen can cause considerable damage to the tensile strength of high steel wires.
10. The prevention of hydrogen embrittlement can be done by protecting the wires from ___________
a) Rain water and humidity
b) Reactions and shocks
c) Heat
d) Deflection
Explanation: In order to prevent hydrogen embrittlement, it is essential that the steel is properly protected from the action of acids and the wires should be protected from rain water and excessive humidity by storing them in dry conditions.