Concrete PavementsReporter: Zandra J. Heramis

Portland CementPortland cement (often referred to

as OPC, from Ordinary Portland Cement) is the most common type of cement in general use around the world, used as a basic ingredient of concrete, mortar, stucco, and most non-specialty grout. 

What makes up Portland Cement?

Cement CCN Mass %

Calcium oxide, CaO C 61–67%

Silicon dioxide, SiO2 S 19–23%

Aluminum oxide, Al2O3

A 2.5–6%

Ferric oxide, Fe2O3 F 0–6%

Sulfate 1.5–4.5%

•Portland cement is primarily made of lime and silica, which account for about 85 percent of its weight. •The rest of the cement is made up of iron, aluminum, calcium and silicon, as well as trace amounts of other ingredients. •Gypsum is added as well to control the amount of time it takes to set.

limestone

silica

Types of Portland Cement:

There are five basic types of portland cement.

•Type I is a general-purpose blend used when there are no issues requiring specific concretes. •Type II is used in high-sulfate conditions. Sulfates can damage concrete, and Type II portland cement resists this damage.• Type III offers a higher degree of strength early in the setting process. •Type IV is formulated to have the setting properties required for building massive structures.•Type V is for high sulfate resistance.

•The behavior of concrete pavement which is subject to loading and environmental effect entirely depends upon the quality of the concrete and underlying sub-grade and base course.

•Concrete, like other materials also expand when wetted and contracts when dried. It shrinks after pouring as the mortar hardens when the cement hydrates.

CONCRETE PAVEMENT CHARACTERISTICSAND BEHAVIOR

hot cold

CONCRETE PAVEMENT DESIGN ASSUMES THE FOLLOWING CONSIDERATIONS

1. That, the pavement slab is designed as beams of plain concrete.

2. That, transverse cracking of concrete slab cannot be avoided. The designer presumed that cracks could be controlled by providing reinforcement to slab joints with the following assumptions:

a. With reinforcement, cracks on the slab will be confined to a weakened plain joints spaced at 4.50m to 6.00m distance.b. Vertical offsetting across the narrow cracks will be prevented by aggregate interlock, or by the dowel bars.c. with simply reinforced slab, cracks will only appear at weakened plane joints spaced at 12 to 20m intervals. Hair cracks to be held tightly by the steel between joints.d. With continuous reinforcement, transverse joints are omitted, hair cracks are checked by the steel and developed at close intervals.e. Faulting is counteracted by aggregate interlock and steel bars.

3. Longitudinal cracking of slabs more than one lane wide is also inevitable.

Deterioration of Concrete Pavement- is due to stresses brought about by load, moisture and temperature.

Distress of Concrete- it is generally grouped into the following categories:

• Distortion- is a vertical displacement of concrete slab at the joints or cracks, this is due to failure or weakness of concrete joints.

• Cracking- can take many forms in concrete pavements which could be a result of either: from applied load or from temperature or moisture changes.

• Disintegration- appears in the form of durability cracking, scaling or spalling as result of mix design or construction related problems.

ASPHALT CONCRETE

If you require paving services, you probably already know that you have two choices: concrete or asphalt.  So which of the two is the best choice? 

Physical Differences Between Concrete and Asphalt

•Hot mix asphalt is made of aggregates (stone, sand, gravel) and liquid asphalt, the oil-based glue which is the glue that holds everything together.

•Concrete is made from American materials such as limestone, rock and water. Concrete is also the most-used manmade material in the world.

Safety Differences Between Paving with Concrete or Asphalt

•Areas paved with asphalt require more maintenance than those paved with concrete. As a result, there is more need for repair crews to handle maintenance of asphalt streets and parking lots. This means more congestion and disruption to work areas, and more danger to road crews and drivers alike. .

•Rigid concrete is also more durable than asphalt. This means that streets paved with concrete are less likely to have potholes. The surface of concrete is also better at preventing automobile skidding, keeping drivers and their families safe.

Cost Differences of Building & Maintenance of Paving Materials

Concrete pavement's life can range anywhere from 20-40 years. But when you factor in annual maintenance, asphalt pavement can cost four to seven times as much money to maintain. This saves you long-term on repair and maintenance.

Noise reductionUse of asphalt road surfaces can significantly reduce noise both inside and outside the car, helping to prevent accidents by alleviating a source of stress that contributes to driver fatigue.

Environmental Factor

•Concrete is 100% recyclable, and the most recycled construction material in the world. So rather than ending up in your state's landfills, it can be broken down and used in new pavement, or for other construction purposes.

•Asphalt is 100% recyclable and is routinely milled and re-laid along with fresh materials, saving money and preserving non-renewable natural resources. Recycling also reduces the use of virgin quality gravel, preserves landfill and saves transport.

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