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Civil Engineering Interview Questions
Blended cement is obtained by mixing OPC (Ordinary Portland cement) with mineral admixtures or additives like fly ash, slag or silica fumes. These mineral admixtures make the blended cement superior as compared to the conventional OPC category of cement.
 
The advantages of using blended cement can be categorized into two types:
 
* Technical advantages
* Environmental advantages

Technical Advantages of using Blended Cement :
 
* Blended cement is smoother than Ordinary Portland Cement (OPC). It provides a finer texture than OPC when mixed.

* It provides more strength than OPC because fly ash and slag cement are significantly stronger than OPC after full setting (more than 28 days) in compressive and flexural stress. It depends on the proportion and quality of the admixture. Silica fume cement sets in even less time, usually 3 to 28 days.

* The permeability is lower in blended cement. It extends its useful life and hardness by reducing the penetration of aggressive water run-off compounds such as sulfates and chlorides, which have increased impact as ordinary cement ages. Silica fume cement allows only 20 percent of the permeability of OPC.

* When we use OPC, if the temperature differences between the concrete surface and its interior are high, it may get weaker, and cracking can occur. So, OPC is not a good choice for the areas where temperatures fall below 40 degrees. Blended cement can reduce peak temperatures and reduce the risk of thermal stress.

Environmental Advantages of using Blended Cement : 
 
* Blended cement requires less water in construction.

* Blended cement saves energy because it uses admixtures such as slag, fly ash, which is produced as a byproduct of other industrial processes.

* Blended cement is a good example of the conservation of resources. It uses waste products of steel plants and coal power plants, among others. Using this waste in cement lowers the demand for other components like limestone, silica, and clay, helping to preserve these natural resources.
Absorption, adsorption, and sorption are similar terms that describe the process of a substance being taken up and retained by another substance. However, there are subtle differences between them:
 
Absorption : Absorption is a process in which a fluid is taken up by a solid or a liquid and diffuses into its inner structure. The fluid is completely incorporated into the material, causing a volume change. An example of absorption is a sponge soaking up water.
 
Adsorption : Adsorption is a process in which a solid or a liquid collects molecules or particles of a substance on its surface. The substance forms a thin film on the surface rather than diffusing into the material. An example of adsorption is a solid such as activated carbon collecting impurities from a fluid.
 
Sorption : Sorption is a general term used to describe the uptake of a substance by a solid or a liquid, whether through absorption or adsorption. Sorption can also refer to the combined processes of absorption and adsorption.
 
In summary, absorption is characterized by diffusion into the material, while adsorption is characterized by the accumulation of a substance on the surface. Sorption encompasses both of these processes.
Theodolite and Total Station are land surveying instruments used to get information about the plot under consideration for construction (buildings, bridges, roads, highways, dams, etc.)
 
A theodolite is basically a telescope with both a vertical and horizontal axis. The angle of each axis can be measured with fairly accurate precision as long as the operator knows how to use the theodolite and knows basic trigonometry. A theodolite needs two people to measure and align the angles.
 
A Theodolite specialises in angle measurements ( horizontal and vertical ) to the precision of degree ( new ones can precisely measure angles in seconds, 1/3600th of a degree ). Usually, it consists of a telescope mounted on two rotating disks or dials ( marked with degrees from 0 to 360 ). The telescope can be rotated horizontally as well as vertically for angle measurements.
 
 
Total station on the other hand, is a multipurpose surveying instrument based on electronic distance measurement (EDM). They can measure distance, angles, elevations with a high level of precision. The data collected by a total station can be transferred through a USB port into the computer where it can be viewed and analysed easily.
 
* Theodolites can only measure angles, have a minimum range of about less than a kilometer and are less precise when compared to Total station, also less expensive than total station. Nowadays we have electronic theodolites which are an upgrade over the normal theodolite.
 
* Total station on the other hand can measure different data rather than just angles. They have a minimum range of about 1 km and are very precise. They are hence obviously expensive when compared to theodolites.
 
* A total station incorporates a theodolites functions into it’s programming, measuring angles and using an electronic distance meter. Total stations are usually superior to theodolites given their digital integration and more consistent precision.
 
* They also can be purchased with a robotic ability, that reduces the number of operators needed, to one. Total stations (both robotic and non-robotic) are more expensive than theodolites, usually much more so, as well as requiring more training to use. These are the difference between theodolite and total station.
Example : "The grade-wise concrete proportion is :
 
Concrete Grade Mix Ratio Compressive Strength
MPa (N/mm2) psi
Normal Grade of Concrete
M5 1 : 5 : 10 5 MPa 725 psi
M7.5 1 : 4 : 8 7.5 MPa 1087 psi
M10 1 : 3 : 6 10 MPa 1450 psi
M15 1 : 2 : 4 15 MPa 2175 psi
M20 1 : 1.5 : 3 20 MPa 2900 psi
Standard Grade of Concrete
M25 1 : 1 : 2 25 MPa 3625 psi
M30 Design Mix 30 MPa 4350 psi
M35 Design Mix 35 MPa 5075 psi
M40 Design Mix 40 MPa 5800 psi
M45 Design Mix 45 MPa 6525 psi
High Strength Concrete Grades
M50 Design Mix 50 MPa 7250 psi
M55 Design Mix 55 MPa 7975 psi
M60 Design Mix 60 MPa 8700 psi
M65 Design Mix 65 MPa 9425 psi
M70 Design Mix 70 MPa 10150 psi
 
There are three types of slumps in a slump test, which is a measure of the consistency or workability of fresh concrete :
 
True Slump : This is when the concrete mixture retains its original shape after being molded into a cone shape and then removed.
 
Shear Slump : This is when the concrete mixture loses its shape and flattens out, indicating a lack of cohesiveness and excessive water in the mix.
 
Collapse Slump : This is when the concrete mixture loses its shape and collapses into a pile, indicating that the mixture is too wet and has poor cohesiveness and structure.
 
The type of slump can help determine the suitability of the concrete mixture for the intended use, and adjustments to the mix design can be made based on the slump test results.
Soil analysis is the study and evaluation of soil properties and characteristics to determine its suitability for a specific purpose, such as construction. Soil analysis provides information on the composition, structure, and engineering properties of the soil, which helps in understanding the behavior of the soil in response to loading, drainage, and other environmental factors.
 
Soil analysis is required for construction because the strength and stability of a building or structure depend on the soil conditions at the site. The soil must be able to support the weight of the structure and resist settling, slipping, and other forms of instability. Understanding the soil conditions at a construction site is crucial for determining the type and size of foundation required, the necessary thickness of the base course or foundation layer, and other design aspects of the construction project.
 
Soil analysis typically involves a combination of field and laboratory tests, including soil sampling, grain size analysis, moisture content determination, compaction testing, and other tests to determine the engineering properties of the soil. The results of the soil analysis can be used to make informed decisions about the construction design and to ensure that the foundation and structure are safe and stable.
The curves on roads are used to change the direction of the road and to provide a smooth transition between straight sections. They are important for road safety as they help drivers to maintain control of their vehicles, especially at high speeds.
 
1. Horizontal Curves
* Simple circular curve 
* Compound Road Curves
* Reverse Curve
* Track transition curve
* Spiral curves
2. Vertical Curves
* Summit Curves
* Valley/ Sag Curve
 
Simple circular curve  : It is a curve consisting of a single arc with a constant radius connecting the two tangents.  It is a type of horizontal curve used most in common.  A simple arc provided in the road or railway track to impose a curve between the two straight lines is the simple circular curve. The smaller is the degree of curve, the flatter is the curve and vice versa. The sharpness of a simple curve is also determined by radius R. Large radius are flat whereas small radius are sharp. A simple curve is normally represented by the length of its radius or by the degree of curve
 
Compound Road Curves : It is a curve made up of two or more circular arcs of successively shorter or longer radii, joined tangentially without reversal of curvature, and used on some railroad tracks and highways as an easement curve to provide a less abrupt transition from tangent to full curve or vice versa. Since their tangent lengths vary, compound curves fit the topography much better than simple curves.
 
Reverse Curve : A reverse curve is composed of two or more simple curves turning in opposite directions. Their points of intersection lie on opposite ends of a common tangent, and the PT of the first curve is coincident with the PC of the second. This point is called the point of reverse curvature (PRC). A reverse curve is composed of two arcs of equal or different radii bending or curving in opposite directions with common tangent at their junction, their centers being on opposite sides of the curve.
 
Track transition curve : A track transition curve, or spiral easement, is a mathematically-calculated curve on a section of highway, in which a straight section changes into a curve. It is designed to prevent sudden changes in lateral In plane (viewed from above), the start of the transition of the horizontal curve is at infinite radius, and at the end of the transition, it has the same radius as the curve itself and so forms a very broad spiral.
 
Spiral curves : Spiral curves are generally used to provide a gradual change in curvature from a straight section of road to a curved section. They assist the driver by providing a natural path to follow. Spiral curves also improve the appearance of circular curves by reducing the break in alignment perceived by drivers. The use of a spiral is about making the road or track follow the same form that the vehicle naturally takes. In a car, you don’t go directly from going straight to fully turning. There is a transition area where you slowly turn the steering wheel. On highways, the lanes are wide enough that you can drive a spiral just by moving from one side of the lane to the other.
 
 
Summit Curves : Summit curves are vertical curves with gradient upwards. Sight distance requirements for the safety is most important on summit curves. The stopping sight distance or absolute minimum sight distance should be provided on these curves and where overtaking is not prohibited, overtaking sight distance or intermediate sight distance should be provided as far as possible. When a fast moving vehicle travels along a summit curve, there is less discomfort to the passengers.
 
Valley/ Sag Curve : Valley curves or sag curves are vertical curves with convexity downwards. In valley curves, the centrifugal force will be acting downwards along with the weight of the vehicle, and hence impact to the vehicle will be more. This will result in jerking of the vehicle and cause discomfort to the passengers. Thus the most important design factors considered in valley curves are- impact-free movement of vehicles at design speed and availability of stopping sight distance under headlight of vehicles for night driving. The valley curve is made fully transitional by providing two similar transition curves of equal length.
 
The Typology of Permits : Property development can be complicated. And if you are new to the world of city regulation and permits, it may be difficult to predict exactly what you need in order to successfully, and legally, complete a project.
 
The typology of permits is generally broken down into two categories :

* Zoning
* Building 

This is because city regulations are also separated by these terms and codes.

The Zoning Code : The Zoning Code is the set of regulations that dictate how property can be used or developed. The first layer of this code is the actual zoning typology, which you may be familiar with- residential multi-family, commercial mixed-use, single-family attached (RM-1, CMX-2, SFA). The zoning classification is given by the city and applied to whole areas of land. So if your property is CMX-2.5, it’s likely that your whole block or several surrounding blocks are also zoned this way.
 
The zoning classification of a property dictates which set of rules in the code applies to the property. For example. If your property is RM-1 there is a different formula to calculate the permitted density than there is for a CMX-2 or CMX-2.5 property.
 
As you have probably guessed, these technicalities can get quite complicated. But the important thing to keep in mind if you are a property owner is that you are not bound by these rules. 
 
The Building Code : Unlike the Zoning Code which applies different rules to different types of properties, the Building Code is applied to all properties equally. Generally, the building code is applied to dimensional standards and best practices for the construction phase of a project.
 
Another time you may need to reference this body of information is during the application process to become familiar with the criteria against which your plans will be evaluated.
 
The Process :  Typically, for any kind of new construction or major renovation project, you will need both of these permits. The Zoning Permit will always come first as the use of the property must be approved before the plans for that use can be evaluated and approved. However, if your proposed project is a “by-right” project and does not require a zoning variance, you can apply for your zoning permit and your building permit at the same time!
Reinforced concrete, concrete in which steel is embedded in such a manner that the two materials act together in resisting forces. The reinforcing steel—rods, bars, or mesh—absorbs the tensile, shear, and sometimes the compressive stresses in a concrete structure.

Plain concrete does not easily withstand tensile and shear stresses caused by wind, earthquakes, vibrations, and other forces and is therefore unsuitable in most structural applications.

In reinforced concrete, the tensile strength of steel and the compressive strength of concrete work together to allow the member to sustain these stresses over considerable spans. The invention of reinforced concrete in the 19th century revolutionized the construction industry, and concrete became one of the world’s most common building materials.
Unit weight of concrete : The unit weight of concrete is typically expressed in pounds per cubic foot (pcf) or kilograms per cubic meter (kg/m³). The average unit weight of concrete is around 145 pcf (2,300 kg/m³) when it is freshly placed, but it can vary depending on the density of the aggregate and the water-cement ratio of the mixture.
 
Unit weight of steel : The unit weight of steel is typically expressed in pounds per cubic foot (pcf) or kilograms per cubic meter (kg/m³). The average unit weight of steel is around 490 pcf (7850 kg/m³). However, the exact unit weight of steel can vary depending on the type of steel and its specific gravity.
 
It is important to note that the unit weight of both concrete and steel will change over time as they age and are subjected to loads and environmental factors. The unit weight of both materials is also an important factor in determining the weight of structures and the loads they can support.