About Seal Coating
Asphalt Sealing, or seal coating, is simply laying a thin protective layer over asphalt-based pavement to give it a protective layer of protection against the elements: oil, water, and U.V. The positive effects of asphalt sealing have long been debated. Some claim that asphalt sealing increases the lifespan of the pavement, but again, there’s no evidence that backs up those claims. Asphalt sealing can damage the pavement by creating cracks. The excessive water and oil that can be soaked into the asphalt also weaken its structural integrity. And the chemical fumes emitted during asphalt sealing can also be harmful to humans.
With all of that in mind, it’s not surprising that many business owners, when they set out to perform asphalt sealing, opt to go the non-per square foot route. The costs are much lower, often no more than a few cents per square foot. And the benefits of lower cost and improved performance are well-known. After all, if you want to save money, you want to reduce your operation costs.
But that brings us to our next question: Are asphalt sealing pads a good solution for parking lots, blacktop driveways, or other paved surfaces? As with any typical maintenance procedure, regular maintenance is the best way to reduce the cost of asphalt sealing. Sealing at least annually will help keep dust, pollen, and other pollutants from making their way onto your paved surfaces. It will also help protect your driveway from water damage, as well as mold and algae growth, both of which cause a lot of problems to homeowners.
Now let’s look at how often you should reseal your asphalt surfaces, especially if you’re going to go the non-per square foot route. The key, again, is regular maintenance. And as it turns out, the best time to perform asphalt sealing and resealing are during the cold winter months. There’s even been some recent evidence suggesting that the best time for asphalt sealing and resealing is during the fall when temperatures are quite low.
Why is that? Fall is when most asphalt-based park finishes and protective coatings need to be applied. Asphalt-based park finishes are very weather-resistant, but that doesn’t mean that they’re impervious to the elements. The rainy spring weather can still cause problems, as can heavy snow, ice, and even dew. So, by applying the protective coatings only during the wet winter months, you’ll be doing your park and business no favors, and in the end, your asphalt sealing and resealing efforts will be wasted.
Here’s why: Asphalt seal coats are extremely dense. Think about asphalt sealing and resealing – it’s the same product, just in a different form. And that means that you have to apply a lot less of it to achieve the same degree of protection. That’s why a lot of asphalt maintenance and repair companies (which specialize in asphalt sealing and resealing) will advise you to apply a minimum of three or four gallons of asphalt-based protectant per square foot of paved area. In other words, if you have a parking lot of ten thousand square feet, you’d want to apply three gallons per every twenty-five feet of the paved area.
If you were to apply that kind of service to your asphalt driveway, you could expect to pay anywhere from three to five dollars per square foot. Now consider that the average cost of asphalt sealing and resealing is only about two or three dollars per square foot. Multiply those two by the number of feet of asphalt you’re going to need to cover (per your parking lot, for example), and you quickly come to understand how much asphalt sealing and resealing would cost you. Applying the service yourself would cost you at least a thousand dollars or more. Not very appealing, I’d say.
But, don’t give up just yet – there are other ways to protect your asphalt driveway seal coating and resealing investment, and they won’t cost you nearly as much, so don’t rule them out just yet. One of those ways is called flashings, which are like raised bumps along the edge of your driveway that will serve as an additional traction aid when you drive over it. The average cost of installing these would be about two hundred dollars, with the total installed cost running into the thousands. Another less expensive alternative is a thin film of asphalt seal coating that has a plastic protective layer between it and the ground, as opposed to flashing. It’s about as thick as standard asphalt, which would then have to be applied to your asphalt driveway seal coating and resurfacing project in much the same way.
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About Cadence, ID
In Western musical theory, a cadence (Latin cadentia, "a falling") is the end of a phrase in which the melody or harmony creates a sense of full or partial resolution, especially in music of the 16th century onwards. A harmonic cadence is a progression of two or more chords that concludes a phrase, section, or piece of music. A rhythmic cadence is a characteristic rhythmic pattern that indicates the end of a phrase. A cadence can be labeled "weak" or "strong" depending on the impression of finality it gives. While cadences are usually classified by specific chord or melodic progressions, the use of such progressions does not necessarily constitute a cadence—there must be a sense of closure, as at the end of a phrase. Harmonic rhythm plays an important part in determining where a cadence occurs.
Cadences are strong indicators of the tonic or central pitch of a passage or piece. The musicologist Edward Lowinsky proposed that the cadence was the "cradle of tonality".
Cadence names may differ between US usage and British usage. This article follows US usage.
Cadences are divided into four main types, according to their harmonic progression: authentic (typically perfect authentic or imperfect authentic), half, plagal, and deceptive. Typically, phrases end on authentic or half cadences, and the terms plagal and deceptive refer to motion that avoids or follows a phrase-ending cadence. Each cadence can be described using the Roman numeral system of naming chords.
An authentic cadence is a cadence from the dominant chord (V) to the root chord (I). A seventh above the root may be added to create a dominant seventh chord (V), and the dominant chord may be preceded by a cadential 6
4 chord. The Harvard Concise Dictionary of Music and Musicians says, "This cadence is a microcosm of the tonal system, and is the most direct means of establishing a pitch as tonic. It is virtually obligatory as the final structural cadence of a tonal work." Authentic cadences are generally classified as either perfect or imperfect. The phrase perfect cadence is sometimes used as a synonym for authentic cadence but can also have a more precise meaning depending on the chord voicing.
In a perfect authentic cadence (PAC), the chords are in root position – that is, the roots of both chords are in the bass – and the tonic is in the highest voice of the final chord. This is generally considered the strongest type of cadence and often found at structurally defining moments. Music theorist William Caplin writes that the perfect authentic cadence "achieves complete harmonic and melodic closure."
There are three types of imperfect authentic cadences (IAC):
An evaded cadence moves from a dominant seventh third inversion chord (V
2) to a first inversion tonic chord (I6
). Because the seventh must fall stepwise, it forces the cadence to resolve to the less stable first inversion chord. To achieve this, a root position V usually changes to a V4
2 right before resolution, thereby "evading" the cadence. (See also inverted cadence below.)
A half cadence (also called an imperfect cadence or semicadence) is any cadence ending on V, whether preceded by II (V of V), ii, vi, IV, or I—or any other chord. Because it sounds incomplete or suspended, the half cadence is considered a weak cadence that calls for continuation.
Several types of half cadences are described below.
A Phrygian half cadence is a half cadence iv–V in minor, so named because the semitonal motion in the bass (sixth degree to fifth degree) resembles the half-step heard in the ii–I of the 15th-century cadence in the Phrygian mode. Due to its being a survival from modal Renaissance harmony this cadence gives an archaic sound, especially when preceded by v (v–iv6–V). A characteristic gesture in Baroque music, the Phrygian cadence often concluded a slow movement immediately followed by a faster one. With the addition of motion in the upper part to the sixth degree, it becomes the Landini cadence.
A Lydian cadence is similar to the Phrygian half cadence, involving iv–V in the minor. The difference is that in the Lydian cadence, the whole iv6 is raised by a half step. In other words, the Phrygian half cadence begins with the first chord built on scale degree , while the Lydian half cadence is built on the scale degree ♯.
Burgundian cadences became popular in Burgundian music. Note the parallel fourths between the upper voices.
The rare plagal half cadence involves a I–IV progression. Like an authentic cadence (V–I), the plagal half cadence involves an ascending fourth (or, by inversion, a descending fifth). The plagal half cadence is a weak cadence, ordinarily at the ending of an antecedent phrase, after which a consequent phrase commences. One example of this use is in "Auld Lang Syne". But in one very unusual occurrence – the end of the exposition of the first movement of Brahms' Clarinet Trio, Op. 114—it is used to complete not just a musical phrase but an entire section of a movement.
A plagal cadence is a cadence from IV to I. It is also known as the Amen cadence because of its frequent setting to the text "Amen" in hymns.
A minor plagal cadence, also known as a perfect plagal cadence, uses the minor iv instead of a major IV. With a very similar voice leading to a perfect cadence, the minor plagal cadence is a strong resolution to the tonic.
The Moravian cadence, which can be found in the works of Leoš Janáček and Bohuslav Martinů amongst others, is a form of plagal cadence in which the outer notes of the first chord each move inwards by a tone to the second. (IV → I6). An early suggestion of the Moravian cadence in classical music occurs in Antonín Dvořák’s New World Symphony.
"A cadence is called 'interrupted', 'deceptive' or 'false' where the penultimate, dominant chord is not followed by the expected tonic, but by another one, often the submediant." This is the most important irregular resolution, most commonly V–vi (or V7–♭VI) in major or V–VI in minor. This is considered a weak cadence because of the "hanging" (suspended) feeling it invokes.
At the beginning of the final movement of Gustav Mahler's 9th Symphony, the listener hears a string of many deceptive cadences progressing from V to IV.
One of the most striking uses of this cadence is in the A-minor section at the end of the exposition in the first movement of Brahms' Third Symphony. The music progresses to an implied E minor dominant (B) with a rapid chromatic scale upwards but suddenly sidesteps to C major. The same device is used again in the recapitulation; this time the sidestep is—as one would expect—to F major, the tonic key of the whole Symphony.
The interrupted cadence is also frequently used in popular music. For example, the Pink Floyd song "Bring the Boys Back Home" ends with such a cadence (at approximately 0:45–50).
An inverted cadence (also called a medial cadence) inverts the last chord. It may be restricted only to the perfect and imperfect cadence, or only to the perfect cadence, or it may apply to cadences of all types. To distinguish them from this form, the other, more common forms of cadences listed above are known as radical cadences.
Cadences can also be classified by their rhythmic position:
Metrically accented cadences are considered stronger and are generally of greater structural significance. In the past, the terms masculine and feminine were sometimes used to describe rhythmically "strong" or "weak" cadences, but this terminology is no longer acceptable to some. Susan McClary has written extensively on the gendered terminology of music and music theory in her book Feminine Endings.
The example below shows a metrically unaccented cadence (IV–V–I). The final chord is postponed to fall on a weak beat.
A Picardy third (or Picardy cadence) is a harmonic device that originated in Western music in the Renaissance era. It refers to the use of a major chord of the tonic at the end of a musical section that is either modal or in a minor key. The example below shows a picardy third in the final chord, from J.S. Bach's Jesu, meine Freude (Jesus, My Joy), mm. 12–13.
The example below shows a cadence featuring an upper leading-tone from a well-known 16th-century lamentation, the debate over which was documented in Rome c. 1540. The final three written notes in the upper voice are B–C–D, in which case a trill on C produces D. However, convention implied a C♯, and a cadential trill of a whole tone on the second to last note produces D♯/E♭, the upper leading-tone of D♮. Presumably, the debate was over whether to use C♯–D♯ or C♯–D for the trill.
Medieval and Renaissance cadences are based upon dyads rather than chords. The first theoretical mention of cadences comes from Guido of Arezzo's description of the occursus in his Micrologus, where he uses the term to mean where the two lines of a two-part polyphonic phrase end in a unison.
A clausula or clausula vera ("true close") is a dyadic or intervallic, rather than chordal or harmonic, cadence. In a clausula vera, two voices approach an octave or unison through stepwise motion in contrary motion.
In three voices, the third voice often adds a falling fifth creating a cadence similar to the authentic cadence in tonal music.
According to Carl Dahlhaus, "as late as the 13th century the half step was experienced as a problematic interval not easily understood, as the remainder between the perfect fourth and the ditone:
In a melodic half step, listeners of the time perceived no tendency of the lower tone toward the upper, or the upper toward the lower. The second tone was not the 'goal' of the first. Instead, musicians avoided the half step in clausulas because, to their ears, it lacked clarity as an interval. Beginning in the 13th century, cadences begin to require motion in one voice by half step and the other a whole step in contrary motion.
A plagal cadence was found occasionally as an interior cadence, with the lower voice in two-part writing moving up a perfect fifth or down a perfect fourth.
A pause in one voice may also be used as a weak interior cadence. The example below, Lassus's Qui vult venire post me, mm. 3–5, shows a pause in the third measure.
In counterpoint, an evaded cadence is one where one of the voices in a suspension does not resolve as expected, and the voices together resolved to a consonance other than an octave or unison (a perfect fifth, a sixth, or a third).
The Corelli cadence, or Corelli clash, named for its association with the violin music of the Corelli school, is a cadence characterized by a major and/or minor second clash between the tonic and the leading-tone or the tonic and supertonic. An example is shown below.
Another "clash cadence", the English cadence, is a contrapuntal pattern particular to the authentic or perfect cadence. It features the blue seventh against the dominant chord, which in the key of C would be B♭ and G–B♮–D. Popular with English composers of the High Renaissance and Restoration periods in the 16th and 17th centuries, the English cadence is described as sounding archaic or old-fashioned. It was first given its name in the 20th century.
The hallmark of this device is the dissonant augmented octave (compound augmented unison) produced by a false relation between the split seventh scale degree, as shown below in an excerpt from O sacrum convivium by Thomas Tallis. The courtesy accidental on the tenor's G♮ is editorial.
A Landini cadence (also known as a Landini sixth, Landini sixth cadence, or under-third cadence) is a cadence that was used extensively in the 14th and early 15th century. It is named after Francesco Landini, a composer who used them profusely. Similar to a clausula vera, it includes an escape tone in the upper voice, which briefly narrows the interval to a perfect fifth before the octave.
The classical and romantic periods of musical history provide many examples of the way the different cadences are used in context.
Mozart’s Romanze from his Piano Concerto No. 20 follows a familiar pattern of a pair of phrases, one ending with a half (imperfect) cadence and the other with an authentic cadence:
The presto movement from Beethoven’s String Quartet Op 130 follows the same pattern, but in a minor key:
The Hallelujah Chorus from Handel’s Messiah culminates powerfully with an iterated plagal cadence:
Debussy’s prelude ‘La Fille aux Cheveux de Lin’ contains a plagal cadence in its 2nd and 3rd bars :
One of the most famous endings in all music is found in the concluding bars of Wagner’s opera Tristan und Isolde, where the dissonant chord in the opening phrase of the opera is finally resolved "three enormous acts and five hours later" in the form of a minor plagal cadence:
In Bach's harmonization of the chorale ‘Wachet auf’, a phrase ending in a deceptive cadence repeats with the cadence changed to an authentic one:
The exposition of the first movement of Beethoven’s Piano Sonata No. 21 (The Waldstein Sonata), Op. 53 features a minor key passage where an authentic (perfect) cadence precedes a deceptive (interrupted) one:
Dvořák’s Slavonic Dance, Op. 72, No. 2 features deceptive (interrupted), half (imperfect) and authentic (perfect) cadences within its first sixteen bars:
Debussy's Prelude “La fille aux cheveux de lin” (see also above) concludes with a passage featuring a deceptive (interrupted) cadence that progresses, not from V–VI, but from V–IV:
Some varieties of deceptive cadence that go beyond the usual V–VI pattern lead to some startling effects. For example, a particularly dramatic and abrupt deceptive cadence occurs in the second Presto movement of Beethoven’s Piano Sonata No. 30, Op. 109, bars 97–112, "a striking passage that used to pre-occupy theorists". The music at this point is in B minor, and carries the expectation is that the chord of F sharp (Chord V) will be followed by the tonic chord of B. However, "Dynamics become softer and softer; dominant and tonic chords of B minor appear isolated on the first beat of a bar, separated by silences: until in sudden fortissimo ... the recapitulation bursts on us in the tonic E minor, the B minor dominants left unresolved."
An equally startling example occurs in J.S. Bach's Toccata and Fugue in F major, BWV 540:
According to Richard Taruskin, in this Toccata, "the already much-delayed resolution is thwarted (m204) by what was the most spectacular 'deceptive cadence' anyone had composed as of the second decade of the eighteenth century ... producing an especially pungent effect." Hermann Keller describes the effect of this cadence as follows: "the splendour of the end with the famous third inversion of the seventh chord, who would not be enthralled by that?"
Chopin's Fantaisie, Op. 49, composed over a century later in 1841, features a similar harmonic jolt:
A deceptive cadence is a useful means for extending a musical narrative. In the closing passage of Bach’s Prelude in F minor from Book II of the Well-Tempered Clavier, the opening theme returns and seems headed towards a possible final resolution on an authentic (perfect) cadence. What the listener may expect is:
Instead, at bar 60, Bach inserts a deceptive cadence (V–VI in F minor), leading to a lengthy digression of some dozen bars before reaching resolution on the final (V–I) cadence.
A similar passage occurs at the conclusion of Mozart's Fantasia in D minor, K397:
In jazz, a cadence is often referred to as a turnaround, chord progressions that lead back and resolve to the tonic (for example, the ii–V–I turnaround). Turnarounds may be used at any point and not solely before the tonic.
Half-step cadences are common in jazz if not cliché. For example, the ascending diminished seventh chord half-step cadence, which—using a secondary diminished seventh chord—creates momentum between two chords a major second apart (with the diminished seventh in between).
The descending diminished seventh chord half-step cadence is assisted by two common tones.
Rhythmic cadencesoften feature a final note longer than the prevailing note values and this often follows a characteristic rhythmic pattern repeated at the end of the phrase. The example below shows a characteristic rhythmic cadence at the end of the first phrase of J.S. Bach's Brandenburg Concerto No. 3 in G major, BMV 1048, mvmt. I, mm. 1–2: