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Maintenance Monday – How Portland Cement is Made

Cement Plant For Calvac Pavings Blog

Portland cement is the basic ingredient of concrete. Concrete is formed when portland cement creates a paste with water that binds with sand and rock to harden.

Cement is manufactured through a closely controlled chemical combination of calcium, silicon, aluminum, iron and other ingredients. Common materials used to manufacture cement include limestone, shells, and chalk or marl combined with shale, clay, slate, blast furnace slag, silica sand, and iron ore. These ingredients, when heated at high temperatures form a rock-like substance that is ground into the fine powder that we commonly think of as cement.

The most common way to manufacture portland cement is through a dry method. The first step is to quarry the principal raw materials, mainly limestone, clay, and other materials. After quarrying the rock is crushed. This involves several stages. The first crushing reduces the rock to a maximum size of about 6 inches. The rock then goes to secondary crushers or hammer mills for reduction to about 3 inches or smaller.

The crushed rock is combined with other ingredients such as iron ore or fly ash and ground, mixed, and fed to a cement kiln. The cement kiln heats all the ingredients to about 2,700 degrees Fahrenheit in huge cylindrical steel rotary kilns lined with special firebrick. Kilns are frequently as much as 12 feet in diameter—large enough to accommodate an automobile and longer in many instances than the height of a 40-story building. The large kilns are mounted with the axis inclined slightly from the horizontal.

Old cement dispenser company

The finely ground raw material or the slurry is fed into the higher end. At the lower end is a roaring blast of flame, produced by precisely controlled burning of powdered coal, oil, alternative fuels, or gas under forced draft.

As the material moves through the kiln, certain elements are driven off in the form of gases. The remaining elements unite to form a new substance called clinker. Clinker comes out of the kiln as grey balls, about the size of marbles.

Clinker is discharged red-hot from the lower end of the kiln and generally is brought down to handling temperature in various types of coolers. The heated air from the coolers is returned to the kilns, a process that saves fuel and increases burning efficiency.

After the clinker is cooled, cement plants grind it and mix it with small amounts of gypsum and limestone. Cement is so fine that 1 pound of cement contains 150 billion grains.  The cement is now ready for transport to ready-mix concrete companies to be used in a variety of construction projects.

Although the dry process is the most modern and popular way to manufacture cement, some kilns in the United States use a wet process. The two processes are essentially alike except in the wet process, the raw materials are ground with water before being fed into the kiln.

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Calvac Paving Bay Area Asphalt & Concrete

New Asphalt Parking Lot

Since 1974, Calvac Paving has taken great pride in serving Bay Area construction needs.

Consistently ensuring the highest possible quality and best results for clients means keeping pace with the latest innovations in paving technology and techniques. Calvac Paving’s dedicated and knowledgeable paving professionals have amassed considerable experience in everything from new construction to refurbishment and repair of old, worn paving such as sidewalks, parking lots, roadways and more. While many paving companies focus solely on one kind of paving, Calvac can boast extensive experience with asphalt, concrete and earthwork, from initial  grading to final striping. Among the services Calvac Paving offers to the public are:

  • new construction
  • grading
  • concrete placement
  • asphalt placement and compaction
  • striping
  • ASPHALT seal coating
  • pulverizing in place
  • ADA upgrades to existing structures
  • crack sealing and repair
  • petromat overlays
  • and more.


In addition to these services, Calvac Paving takes its obligations to the environment we all share very seriously. We use the latest green and eco-friendly policies and practices at every stage of construction from the project’s start to the final cleanup and disposal of waste products at the end.

“Green” Paving?

While this phrase may sound oxymoronic, asphalt pavement has consistently been reported as the most frequently recycled material in the nation since 1993. Continuous improvements in recycling technology and paving practices and techniques that permit for more adaptive uses of existing paving materials have fueled this recycling boom with regards to asphalt and, to a lesser degree, concrete. Purely virgin asphalt, also known as “hot-mix,” is relatively rare today because of the numerous advantages of recycling asphalt in place. However, many old-school pavers often still refer to “warm-mix,” discussed below, as “hot-mix” regardless of this designation’s true accuracy.

Most asphalt you see on the road today consists of rocks, also called aggregates, sand, binder material and additives such as shredded rubber tires, pig manure and metal slag, to name a few. These additives are re-purposed and treated in such a way as to make them a cohesive part of the overall mix and increase the mix’s performance. This transforms relatively useless or even outright hazardous materials into reasonably safe and effective filler materials for asphalt mixes. However, the most common fillers are recycled asphalt paving and asphalt shingles. Using these materials in “warm-mix” asphalt paving sharply decreases the amount of virgin oil binder needed to create a safe driving surface with proper internal cohesion and compactive properties.

According to the National Asphalt Paving Association, in the 2013 construction season alone nearly 68 million tons of recycled asphalt and almost 2 million tons of asphalt shingles were used as recyclables, at a savings to taxpayers of around $2 billion. The use of recyclables has increased 21% since 2009 and represents over 99% of all in situ, or existing, asphalt paving being recycled and re-purposed instead of ending up in landfills.

Calvac Paving is proud to be part of an industry that is able to recycle and reuse apparent waste materials so efficiently and effectively. Calvac Paving takes a deep interest in ongoing advances in procedures and techniques that allow for new ways to re-purpose existing pavement, whether it is asphalt, concrete or something else.

Looking To The Future

The interest in new advances is not limited to asphalt, because Calvac Paving is dedicated to finding more efficient and ecologically sound ways of achieving the same overall goals. One development that Calvac Paving is watching with great interest is so-called “bio-concrete.” In this type of concrete a regular concrete mix is impregnated with tiny plastic capsules containing a type of bacillus bacterium which feeds on calcium lactate and excretes limestone. The capsules dissolve when exposed to water, activating and freeing the dormant bacteria within to begin the healing process. This landmark technology could result in admixtures for other types of paving, increasing the strength, performance and longevity of all kinds of paving and reducing necessary time-of-life repairs dramatically.

As paving technology and techniques evolve, Calvac Paving intends to retain our leadership position in adopting new practices, prioritizing greater safety, security, durability and environmental awareness in every task we undertake. From new builds to maintenance and repair of existing paving projects, Calvac Paving wants to ensure that its products and services stand the test of time, just as we have since 1974. For your next paving project, whether you’re starting from scratch or trying to determine the most efficient and effective way to repair or replace worn, cracked or improperly placed paving materials, Calvac Paving’s experienced personnel can become stakeholders in your properties. We welcome the opportunity to show you why Calvac Paving has been building the Bay Area for over forty years, giving real results that stand the test of time!

 


Petromat Overlays

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Condition
Intermittent linear cracking and/or a worn and ravelled asphalt surface. Aged and oxidized asphalt, rough and rocky with a light gray appearance. Minor alligatored areas (interconnecting cracks) with little or no subsidence of the asphalt surface. These failures are typically wide spread throughout the property but not severe and any locations and often caused by the advanced age and oxidization of the asphalt surface.

Cause
A less than satisfactory base on top of moisture sensitive subgrade causes swell and shrinkage in that subgrade, which reflects through the base material and then up through asphalt until the cracks become visible on the surface. The infiltration of moisture through these cracks and oxidized (dried out) asphalt accelerates the damage.

It is also possible that the existing aggregate base and pavement section is too thin to withstand the type of traffic that it encounters.

Correction
A Petromat Overlay is the application of a liquid asphalt binder and paving of a 1 1/2″- 3″ layer of asphalt over the entire asphalt surface. The addition of “Petromat” paving fabric impregnated with liquid asphalt creates a barrier between the layers of asphalt that retards reflective cracking and water intrusion. This fabric is a nonwoven fabric that helps to dissipate the stresses on your existing asphalt surface and bridge existing weaker areas.

Calvac Paving will excavate or grind the existing asphalt surface at all necessary transitions to allow for full depth asphalt placement in these vital areas. We will then clean the entire surface of the proposed overlay to ensure a complete bond. Apply liquid asphalt binder at a rate of .25-.30 gallons per square yard immediately followed by installation of the “Petromat” pavement reinforcing fabric. The fabric will be installed according to manufacturer’s specifications; which includes an overlap of 3″-6″ at each joint and removal of all necessary wrinkles in the fabric.

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Striping

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Condition
Intermittent linear cracking and/or a worn and ravelled asphalt surface. Aged and oxidized asphalt, rough and rocky with a light gray appearance. Minor alligatored areas (interconnecting cracks) with little or no subsidence of the asphalt surface. These failures are typically wide spread throughout the property but not severe and any locations and often caused by the advanced age and oxidization of the asphalt surface.

Cause
A less than satisfactory base on top of moisture sensitive subgrade causes swell and shrinkage in that subgrade, which reflects through the base material and then up through asphalt until the cracks become visible on the surface. The infiltration of moisture through these cracks and oxidized (dried out) asphalt accelerates the damage.

It is also possible that the existing aggregate base and pavement section is too thin to withstand the type of traffic that it encounters.

Correction
A Petromat Overlay is the application of a liquid asphalt binder and paving of a 1 1/2″- 3″ layer of asphalt over the entire asphalt surface. The addition of “Petromat” paving fabric impregnated with liquid asphalt creates a barrier between the layers of asphalt that retards reflective cracking and water intrusion. This fabric is a nonwoven fabric that helps to dissipate the stresses on your existing asphalt surface and bridge existing weaker areas.

Calvac Paving will excavate or grind the existing asphalt surface at all necessary transitions to allow for full depth asphalt placement in these vital areas. We will then clean the entire surface of the proposed overlay to ensure a complete bond. Apply liquid asphalt binder at a rate of .25-.30 gallons per square yard immediately followed by installation of the “Petromat” pavement reinforcing fabric. The fabric will be installed according to manufacturer’s specifications; which includes an overlap of 3″-6″ at each joint and removal of all necessary wrinkles in the fabric.

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A.D.A. Upgrades

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Condition
Intermittent linear cracking and/or a worn and ravelled asphalt surface. Aged and oxidized asphalt, rough and rocky with a light gray appearance. Minor alligatored areas (interconnecting cracks) with little or no subsidence of the asphalt surface. These failures are typically wide spread throughout the property but not severe and any locations and often caused by the advanced age and oxidization of the asphalt surface.

Cause
A less than satisfactory base on top of moisture sensitive subgrade causes swell and shrinkage in that subgrade, which reflects through the base material and then up through asphalt until the cracks become visible on the surface. The infiltration of moisture through these cracks and oxidized (dried out) asphalt accelerates the damage.

It is also possible that the existing aggregate base and pavement section is too thin to withstand the type of traffic that it encounters.

Correction
A Petromat Overlay is the application of a liquid asphalt binder and paving of a 1 1/2″- 3″ layer of asphalt over the entire asphalt surface. The addition of “Petromat” paving fabric impregnated with liquid asphalt creates a barrier between the layers of asphalt that retards reflective cracking and water intrusion. This fabric is a nonwoven fabric that helps to dissipate the stresses on your existing asphalt surface and bridge existing weaker areas.

Calvac Paving will excavate or grind the existing asphalt surface at all necessary transitions to allow for full depth asphalt placement in these vital areas. We will then clean the entire surface of the proposed overlay to ensure a complete bond. Apply liquid asphalt binder at a rate of .25-.30 gallons per square yard immediately followed by installation of the “Petromat” pavement reinforcing fabric. The fabric will be installed according to manufacturer’s specifications; which includes an overlap of 3″-6″ at each joint and removal of all necessary wrinkles in the fabric.

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Seal Coating

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Condition
Intermittent linear cracking and/or a worn and ravelled asphalt surface. Aged and oxidized asphalt, rough and rocky with a light gray appearance. Minor alligatored areas (interconnecting cracks) with little or no subsidence of the asphalt surface. These failures are typically wide spread throughout the property but not severe and any locations and often caused by the advanced age and oxidization of the asphalt surface.

Cause
A less than satisfactory base on top of moisture sensitive subgrade causes swell and shrinkage in that subgrade, which reflects through the base material and then up through asphalt until the cracks become visible on the surface. The infiltration of moisture through these cracks and oxidized (dried out) asphalt accelerates the damage.

It is also possible that the existing aggregate base and pavement section is too thin to withstand the type of traffic that it encounters.

Correction
A Petromat Overlay is the application of a liquid asphalt binder and paving of a 1 1/2″- 3″ layer of asphalt over the entire asphalt surface. The addition of “Petromat” paving fabric impregnated with liquid asphalt creates a barrier between the layers of asphalt that retards reflective cracking and water intrusion. This fabric is a nonwoven fabric that helps to dissipate the stresses on your existing asphalt surface and bridge existing weaker areas.

Calvac Paving will excavate or grind the existing asphalt surface at all necessary transitions to allow for full depth asphalt placement in these vital areas. We will then clean the entire surface of the proposed overlay to ensure a complete bond. Apply liquid asphalt binder at a rate of .25-.30 gallons per square yard immediately followed by installation of the “Petromat” pavement reinforcing fabric. The fabric will be installed according to manufacturer’s specifications; which includes an overlap of 3″-6″ at each joint and removal of all necessary wrinkles in the fabric.

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Concrete

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Condition
Intermittent linear cracking and/or a worn and ravelled asphalt surface. Aged and oxidized asphalt, rough and rocky with a light gray appearance. Minor alligatored areas (interconnecting cracks) with little or no subsidence of the asphalt surface. These failures are typically wide spread throughout the property but not severe and any locations and often caused by the advanced age and oxidization of the asphalt surface.

Cause
A less than satisfactory base on top of moisture sensitive subgrade causes swell and shrinkage in that subgrade, which reflects through the base material and then up through asphalt until the cracks become visible on the surface. The infiltration of moisture through these cracks and oxidized (dried out) asphalt accelerates the damage.

It is also possible that the existing aggregate base and pavement section is too thin to withstand the type of traffic that it encounters.

Correction
A Petromat Overlay is the application of a liquid asphalt binder and paving of a 1 1/2″- 3″ layer of asphalt over the entire asphalt surface. The addition of “Petromat” paving fabric impregnated with liquid asphalt creates a barrier between the layers of asphalt that retards reflective cracking and water intrusion. This fabric is a nonwoven fabric that helps to dissipate the stresses on your existing asphalt surface and bridge existing weaker areas.

Calvac Paving will excavate or grind the existing asphalt surface at all necessary transitions to allow for full depth asphalt placement in these vital areas. We will then clean the entire surface of the proposed overlay to ensure a complete bond. Apply liquid asphalt binder at a rate of .25-.30 gallons per square yard immediately followed by installation of the “Petromat” pavement reinforcing fabric. The fabric will be installed according to manufacturer’s specifications; which includes an overlap of 3″-6″ at each joint and removal of all necessary wrinkles in the fabric.

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ASPHALT

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Condition
Intermittent linear cracking and/or a worn and ravelled asphalt surface. Aged and oxidized asphalt, rough and rocky with a light gray appearance. Minor alligatored areas (interconnecting cracks) with little or no subsidence of the asphalt surface. These failures are typically wide spread throughout the property but not severe and any locations and often caused by the advanced age and oxidization of the asphalt surface.

Cause
A less than satisfactory base on top of moisture sensitive subgrade causes swell and shrinkage in that subgrade, which reflects through the base material and then up through asphalt until the cracks become visible on the surface. The infiltration of moisture through these cracks and oxidized (dried out) asphalt accelerates the damage.

It is also possible that the existing aggregate base and pavement section is too thin to withstand the type of traffic that it encounters.

Correction
A Petromat Overlay is the application of a liquid asphalt binder and paving of a 1 1/2″- 3″ layer of asphalt over the entire asphalt surface. The addition of “Petromat” paving fabric impregnated with liquid asphalt creates a barrier between the layers of asphalt that retards reflective cracking and water intrusion. This fabric is a nonwoven fabric that helps to dissipate the stresses on your existing asphalt surface and bridge existing weaker areas.

Calvac Paving will excavate or grind the existing asphalt surface at all necessary transitions to allow for full depth asphalt placement in these vital areas. We will then clean the entire surface of the proposed overlay to ensure a complete bond. Apply liquid asphalt binder at a rate of .25-.30 gallons per square yard immediately followed by installation of the “Petromat” pavement reinforcing fabric. The fabric will be installed according to manufacturer’s specifications; which includes an overlap of 3″-6″ at each joint and removal of all necessary wrinkles in the fabric.

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