CIVIL ENGINEERING OBJECTIVE TYPE QUESTIONS

1. The percent voids in mineral aggregate (VMA) and percent air voids (Vv) in a compacted cylindrical bituminous mix specimen are 15 and 4.5respectively. The percent voids filled with bitumen (VFB) for this specimen is:
(A) 24
(B) 30
(C) 54
(D) 70

2. The foundation slab is subjected to vertical downward stresses equal to net safe bearing capacity derived in the above question. Using influence factor If = 2.0, and neglecting embedment depth and rigidity corrections, the immediate settlement of the dense sand layer will be:
(A) 58 mm
(B) 111 mm
(C) 126 mm
(D) 179 mm

3. Which of the following options is the closest in meaning to the word given below: Primeval
(A) Modern
(B) Historic
(C) Primitive

Why Sometimes the side of concrete bridges is observed to turn black in colour

Sometimes the side of concrete bridges is observed to turn black in colour. What is the reason for this phenomenon?

In some cases, it may be due to the accumulation of dust and dirt. However, for the majority of such phenomenon, it is due to fungus or algae growth on concrete bridges. After rainfall, the bridge surface absorbs water and retains it for a certain period of time. Hence, this provides a good habitat for fungus or algae to grow. Moreover, atmospheric pollution and proximity of plants provide nutrients for their growth. Improvement in drainage details and application of painting and coating to bridges help to solve this problem. Reference is made to Sandberg Consulting Engineers Report 18380/X/01.

What is the difference between epoxy grout, cement grout and cement mortar?

What is the difference between epoxy grout, cement grout and cement mortar?

Epoxy grout consists of epoxy resin, epoxy hardener and sand/aggregates. In fact, there are various types of resin used in construction industry like epoxy, polyester, polyurethane etc. Though epoxy grout appears to imply the presence of cement material by its name, it does not contain any cement at all. On the other hand, epoxy hardener serves to initiate the hardening process of epoxy grout. It is commonly used for repairing hairline cracks and cavities in concrete structures and can be adopted as primer or bonding agent.

Cement grout is formed by mixing cement powder with water in which the ratio of cement of water is more or less similar to that of concrete. Setting and hardening are the important processes which affect the performance of cement grout. Moreover, the presence of excessive voids would also affect the strength, stiffness and permeability of grout. It is versatile in application of filling voids and gaps in structures.

Cement mortar is normally a mixture of cement, water and sand. They are used as bedding for concrete kerbs in roadwork. 

Why is sulphate-resisting cement not used in marine concrete?

Why is sulphate-resisting cement not used in marine concrete?

The main components of Portland cement are tricalcium silicate, dicalcium silicate, tricalcium aluminate and tetracalcium aluminoferrite. In sulphate-resisting cement, it contains a low amount of tricalcium aluminate in order to avoid sulphate attack. Otherwise, tricalcium aluminate would react with sulphates to form calcium sulphoaluminate and gypsum that cause expansion and crack the concrete structure.

However, for marine concrete sulphate-resisting cement should not be used because tricalcium aluminate has high affinity for chloride ions. This is based on the possible reaction of chloride ions and tricalcium aluminate to form calcium chloroaluminate hydrate as suggested by P. Kumar Mehta (1991) and the reduction of which may increase the rate of chloride attack to the concrete marine structure and result in faster corrosion of steel reinforcement in marine structures. 

What is the function of a separation membrane between concrete pavement slab and sub-base?

What is the function of a separation membrane between concrete pavement slab and sub-base?

The separation membrane between concrete pavement slab and sub-base has the following functions:

(i) It aids in reducing the frictional forces between concrete slab and sub-base and helps to movement of concrete slab with respect to sub-base owing to changes in temperature and moisture.
(ii) It prevents the loss of cement and water in immature concrete which significantly affects the strength and durability of hardened concrete.
(iii)It avoids the mixing up of sub-base materials and freshly placed concrete.

Polythene sheeting, which is a waterproof material, is commonly used as separation membrane.  

What is the difference between fasteners, bolts and screws?

What is the difference between fasteners, bolts and screws?

Fastener is a general term to describe something which is used as a restraint for holding things together or attaching to other things.

The main physical distinction between screws and bolts is that screws are entirely full of threads while bolts contain shanks without threads. However, a better interpretation of the differences between the two is that bolts are always fitted with nuts. On the contrary, screws are normally used with tapped holes.  

Should design life be the same as return period for design conditions?

Should design life be the same as return period for design conditions?

Design life means the minimum duration a structure is expected to last. The longer is the design life; the higher is the cost of a project. Therefore, in choosing the design life for a structure, engineers should consider the design life which generates a economical project without sacrificing the required function.

In selection of return period of certain design conditions, winds, waves, etc., one should consider the consequences of exceedance. In fact, there are normally no extreme maximum values of these design conditions and its selection is based on the probability of exceedance which is related to return period.

Therefore, design life may not be equal to return period of design conditions because their selections are based on different considerations.