Misplaced Pages

#591408

46-501: The riot began during the evening of August 20, 1960 as an organized protest over the closing of Hourglass Field , an unused United States Navy airfield, to drag racing . The drag racing had been organized by the San Diego Timing Association, a local group of hot rod clubs, but was unauthorized. The Navy and the police looked the other way because Hourglass Field was the only off-street venue available for drag racing at

92-402: A binder. The abbreviation, AC , is sometimes used for asphalt concrete but can also denote asphalt content or asphalt cement , referring to the liquid asphalt portion of the composite material. Mixing of asphalt and aggregate is accomplished in one of several ways: In addition to the asphalt and aggregate, additives, such as polymers , and antistripping agents may be added to improve

138-454: Is a maintenance measure that helps keep water and petroleum products out of the pavement. Maintaining and cleaning ditches and storm drains will extend the life of the road at low cost. Sealing small cracks with bituminous crack sealer prevents water from enlarging cracks through frost weathering, or percolating down to the subbase and softening it. For somewhat more distressed roads, a chip seal or similar surface treatment may be applied. As

184-772: Is a research program by the FHWA , which is specifically focusing on long-term pavement behaviour. Asphalt deterioration can include crocodile cracking , potholes , upheaval, raveling , bleeding , rutting , shoving, stripping , and grade depressions. In cold climates, frost heaves can crack asphalt even in one winter. Filling the cracks with bitumen is a temporary fix, but only proper compaction and drainage can slow this process. Factors that cause asphalt concrete to deteriorate over time mostly fall into one of three categories: construction quality, environmental considerations, and traffic loads. Often, damage results from combinations of factors in all three categories. Construction quality

230-415: Is critical to pavement performance. This includes the construction of utility trenches and appurtenances that are placed in the pavement after construction. Lack of compaction in the surface of the asphalt, especially on the longitudinal joint, can reduce the life of a pavement by 30 to 40%. Service trenches in pavements after construction have been said to reduce the life of the pavement by 50%, mainly due to

276-473: Is found on interstate highways where maintenance is highly crucial. Asphalt concrete generates less roadway noise than a Portland cement concrete surface, and is typically less noisy than chip seal surfaces. Because tire noise is generated through the conversion of kinetic energy to sound waves , more noise is produced as the speed of a vehicle increases. The notion that highway design might take into account acoustical engineering considerations, including

322-420: Is why some agencies place the priority on preventive maintenance of roads in good condition, rather than reconstructing roads in poor condition. Poor roads are upgraded as resources and budget allow. In terms of lifetime cost and long term pavement conditions, this will result in better system performance. Agencies that concentrate on restoring their bad roads often find that by the time they have repaired them all,

368-527: The El Cajon Boulevard Riot . A community college now occupies the site. Its athletics complex and a community park adjacent to the college are named after the airfield. Hourglass field was located just west of U.S. Route 395 (now Interstate 15 ), about three miles north of what is now MCAS Miramar . It was formerly known as Linda Vista Mesa Field and, later, Navy Outlying Field (NOLF) Miramar or Miramar Field / #01715 (OLF). From late 1931 to 1941 it

414-627: The National Hot Rod Association also pledged his support to getting local enthusiasts a place to race. Eventually, all of these pressures came together and two new Drag racing strips were opened. The San Diego Raceway opened in Ramona in 1963 and the Carlsbad Raceway opened in 1964. San Diego closed down after 1968 and Carlsbad after 2004. There was an attempt at running in the parking lot of Jack Murphy Stadium in an organized event in

460-406: The subsoil to see how much load it can withstand. The pavement and subbase thicknesses are designed to withstand the wheel loads. Sometimes, geogrids are used to reinforce the subbase and further strengthen the roads. Drainage, including ditches , storm drains and underdrains are used to remove water from the roadbed, preventing it from weakening the subbase and subsoil. Sealcoating asphalt

506-561: The 1970's, but currently drag strips in the Barona Reservation serve the purpose. Hourglass Field Hourglass Field was the popular name for an auxiliary landing field operated by the United States Navy before and during World War II in the northern part of San Diego, California . It is remembered as a racetrack in the regional road racing circuit and because a crackdown on unauthorized drag racing there triggered

SECTION 10

#1733271238592

552-586: The Department of Transportation to incorporate crumb rubber into asphalt paving materials. Other recycled materials that are actively included in asphalt concrete mixes across the United States include steel slag, blast furnace slag, and cellulose fibers. Further research has been conducted to discover new forms of waste that may be recycled into asphalt mixes. A 2020 study conducted in Melbourne, Australia presented

598-675: The Navy used the surrounding area as a bombing range. The Army also used the area as a test area. In 1956 the Navy made the airfield available to the San Diego Junior Chamber of Commerce and the San Diego Region Sports Car Club of America (SCCA) for automobile racing. In 1957 a 1.8 mile track was laid out and the California Sport Car Club and San Diego Region SCCA staged races there for three years as part of

644-547: The United Kingdom and the Republic of Ireland) is a composite material commonly used to surface roads , parking lots , airports , and the core of embankment dams . Asphalt mixtures have been used in pavement construction since the beginning of the twentieth century. It consists of mineral aggregate bound together with bitumen (a substance also independently known as asphalt), laid in layers, and compacted. The process

690-496: The United States contained, on average, 21.1% RAP and 0.2% RAS. Recycled asphalt components may be reclaimed and transported to an asphalt plant for processing and use in new pavements, or the entire recycling process may be conducted in-place. While in-place recycling typically occurs on roadways and is specific to RAP, recycling in asphalt plants may utilize RAP, RAS, or both. In 2019, an estimated 97.0 million tons of RAP and 1.1 million tons of RAS were accepted by asphalt plants in

736-534: The United States. RAP is typically received by plants after being milled on-site, but pavements may also be ripped out in larger sections and crushed in the plant. RAP millings are typically stockpiled at plants before being incorporated into new asphalt mixes. Prior to mixing, stockpiled millings may be dried and any that have agglomerated in storage may have to be crushed. RAS may be received by asphalt plants as post-manufacturer waste directly from shingle factories, or they may be received as post-consumer waste at

782-416: The United States. Many roofing shingles also contain asphalt, and asphalt concrete mixes may contain reclaimed asphalt shingles (RAS). Research has demonstrated that RAP and RAS can replace the need for up to 100% of the virgin aggregate and asphalt binder in a mix, but this percentage is typically lower due to regulatory requirements and performance concerns. In 2019, new asphalt pavement mixtures produced in

828-441: The asphalt to oxidize, becoming stiffer and less resilient, leading to crack formation. Cold temperatures can cause cracks as the asphalt contracts. Cold asphalt is also less resilient and more vulnerable to cracking. Water trapped under the pavement softens the subbase and subgrade, making the road more vulnerable to traffic loads. Water under the road freezes and expands in cold weather, causing and enlarging cracks. In spring thaw,

874-461: The edge of runway 3/21, east of the indent of the "hourglass", separated by approximately 40 feet. The remaining surface of this part of runway 3/21 was used as a parking lot for the baseball/softball fields. As of 2012 only a small triangle of the original asphalt remains, from runway 13/31, as part of an open field adjacent to Black Mountain Road. Hourglass Field Athletics Complex now sits on the east end of

920-508: The end of their service life. Processing of RAS includes grinding the shingles and sieving the grinds to remove oversized particles. The grinds may also be screened with a magnetic sieve to remove nails and other metal debris. The ground RAS is then dried, and the asphalt cement binder can be extracted. For further information on RAS processing, performance, and associated health and safety concerns, see Asphalt Shingles . In-place recycling methods allow roadways to be rehabilitated by reclaiming

966-691: The existing pavement, remixing, and repaving on-site. In-place recycling techniques include rubblizing , hot in-place recycling, cold in-place recycling, and full-depth reclamation . For further information on in-place methods, see Road Surface . During its service life, the asphalt cement binder, which makes up about 5–6% of a typical asphalt concrete mix, naturally hardens and becomes stiffer. This aging process primarily occurs due to oxidation, evaporation, exudation, and physical hardening. For this reason, asphalt mixes containing RAP and RAS are prone to exhibiting lower workability and increased susceptibility to fatigue cracking. These issues are avoidable if

SECTION 20

#1733271238592

1012-534: The first major youth riots of the 1960s. Some time after the riot the Navy cut trenches across the Runways at Hourglass Field. The field was no longer useful for any kind of racing but became a popular spot for radio-controlled model aircraft, especially thermal soaring gliders flown by members of the Torrey Pines Gulls R/C Soaring Society, through the 1980s. In 1969 Miramar College opened on

1058-593: The fliers that were used to organize the protest. He was released two days later without charges due to the fact that the police did not have enough evidence. This led to an organized mass protest the night of August 20 and 21 at the intersection of El Cajon Boulevard and Cherokee Street in San Diego . The crowd of about 3,000 teenagers and adults blocked three blocks of El Cajon Boulevard (one of San Diego's major east-west thoroughfares) and began holding impromptu drag races with just enough room for cars to race two-abreast down

1104-414: The friction course. In general, the viscosity of asphalt allows it to conveniently form a convex surface, and a central apex to streets and roads to drain water to the edges. This is not, however, in itself an advantage over concrete, which has various grades of viscosity and can be formed into a convex road surface. Rather, it is the economy of asphalt concrete that renders it more frequently used. Concrete

1150-400: The ground thaws from the top down, so water is trapped between the pavement above and the still-frozen soil underneath. This layer of saturated soil provides little support for the road above, leading to the formation of potholes. This is more of a problem for silty or clay soils than sandy or gravelly soils. Some jurisdictions pass frost laws to reduce the allowable weight of trucks during

1196-416: The lack of compaction in the trench, and also because of water intrusion through improperly sealed joints. Environmental factors include heat and cold, the presence of water in the subbase or subgrade soil underlying the pavement, and frost heaves. High temperatures soften the asphalt binder, allowing heavy tire loads to deform the pavement into ruts. Paradoxically, high heat and strong sunlight also cause

1242-498: The mix's rutting resistance while maintaining adequate fatigue cracking resistance. In mixes with higher recycled content, the addition of virgin binder becomes less effective, and rejuvenators may be used. Rejuvenators are additives that restore the physical and chemical properties of the aged binder. When conventional mixing methods are used in asphalt plants, the upper limit for RAP content before rejuvenators become necessary has been estimated at 50%. Research has demonstrated that

1288-409: The number, width and length of cracks increases, more intensive repairs are needed. In order of generally increasing expense, these include thin asphalt overlays, multicourse overlays, grinding off the top course and overlaying, in-place recycling, or full-depth reconstruction of the roadway. It is far less expensive to keep a road in good condition than it is to repair it once it has deteriorated. This

1334-404: The pavement for controlling storm water. Different types of asphalt concrete have different performance characteristics in roads in terms of surface durability, tire wear, braking efficiency and roadway noise . In principle, the determination of appropriate asphalt performance characteristics must take into account the volume of traffic in each vehicle category, and the performance requirements of

1380-401: The performance aspects of RAP and RAS is to combine the recycled components with virgin aggregate and virgin asphalt binder. This approach can be effective when the recycled content in the mix is relatively low, and has a tendency to work more effectively with soft virgin binders. A 2020 study found that the addition of 5% RAS to a mix with a soft, low-grade virgin binder significantly increased

1426-468: The properties of the final product. Areas paved with asphalt concrete—especially airport aprons —have been called "the tarmac" at times, despite not being constructed using the tarmacadam process. A variety of specialty asphalt concrete mixtures have been developed to meet specific needs, such as stone-matrix asphalt , which is designed to ensure a strong wearing surface, or porous asphalt pavements, which are permeable and allow water to drain through

El Cajon Boulevard riot - Misplaced Pages Continue

1472-422: The recycled components are apportioned correctly in the mix. Practicing proper storage and handling, such as by keeping RAP stockpiles out of damp areas or direct sunlight, is also important in avoiding quality issues. The binder aging process may also produce some beneficial attributes, such as by contributing to higher levels of rutting resistance in asphalts containing RAP and RAS. One approach to balancing

1518-518: The regional road racing circuit. The field was also used for motorcycle racing and unauthorized drag racing . In early August 1960, after three bystanders were injured during a drag race, the Navy shut down the airfield to racing. This led to an organized mass protest and a riot the night of August 20 and 21 in San Diego that the San Diego Union dubbed the drag strip riot and socialists call one of

1564-458: The riot 80 adult demonstrators and 36 juveniles were arrested for the riot. The next night several drag racers drove around town taunting the police. This led to a further 100 people being arrested, including over 30 juveniles who were charged with curfew violations. After the riot, the City of San Diego promised to form a committee to look into the problem of a lack of drag racing sites. The president of

1610-446: The road over a longer period of time, increasing ruts, cracking, and corrugations in the asphalt pavement. Other causes of damage include heat damage from vehicle fires, or solvent action from chemical spills. The life of a road can be prolonged through good design, construction and maintenance practices. During design, engineers measure the traffic on a road, paying special attention to the number and types of trucks. They also evaluate

1656-421: The roads that were in good condition have deteriorated. Some agencies use a pavement management system to help prioritize maintenance and repairs. Asphalt concrete is a recyclable material that can be reclaimed and reused both on-site and in asphalt plants . The most common recycled component in asphalt concrete is reclaimed asphalt pavement (RAP). RAP is recycled at a greater rate than any other material in

1702-743: The runway 3/21 location. Its grass plaza has narrow cobblestone features that outline an "X" and a bar reminiscent the runway layout. The alignment of Black Mountain Road is adjacent to the former eastern edge of runway 18/36, the north/south runway (that was not part of the hourglass shape). Hourglass Field Community Park is near the former eastern edge of the southern one-third or so of the runway 18/36. 32°54′30″N 117°7′21″W  /  32.90833°N 117.12250°W  / 32.90833; -117.12250 Asphalt concrete Asphalt concrete (commonly called asphalt , blacktop , or pavement in North America, and tarmac or bitumen macadam in

1748-398: The selection of the type of surface paving, arose in the early 1970s. With regard to structural performance, the asphalt behaviour depends on a variety of factors including the material, loading and environmental condition. Furthermore, the performance of pavement varies over time. Therefore, the long-term behaviour of asphalt pavement is different from its short-term performance. The LTPP

1794-417: The site of Hourglass Field as a training facility for San Diego law enforcement and firefighting personnel. The site is now a small part of the large San Diego community of Mira Mesa . Most of Hourglass Field is now gone. As of 2006 the northern edge of the hourglass still existed adjacent to the north side of the police/firefighter driving course. The southern edge of some baseball/softball fields paralleled

1840-404: The spring thaw season and protect their roads. The damage a vehicle causes is roughly proportional to the axle load raised to the fourth power, so doubling the weight an axle carries actually causes 16 times as much damage. Wheels cause the road to flex slightly, resulting in fatigue cracking, which often leads to crocodile cracking. Vehicle speed also plays a role. Slowly moving vehicles stress

1886-401: The street. Around 2 A.M. more than 65 police officers began quelling the riot first by ordering them to disperse and then moving in with tear gas and riot sticks. Some protestors tried to fight back by throwing coke bottles and rocks at the police and trying to overturn police cars. It took 3 hours to control the mob and two police officers were hurt during the course of the night. At the scene of

El Cajon Boulevard riot - Misplaced Pages Continue

1932-521: The time. On August 8, 1960, three (possibly four) bystanders were injured during a drag race. The Navy had been under some pressure to crack down on the drag racing and shut down the airfield to drag racing after the incident. Car clubs lobbied the city for an official drag racing site but were denied as the San Diego Police Chief A.E. Jensen said "Drag strips actually stimulate highway recklessness among those viewing such contests". The Protest

1978-527: The use of rejuvenators at optimal doses can allow for mixes with 100% recycled components to meet the performance requirements of conventional asphalt concrete. Beyond RAP and RAS, a range of waste materials can be re-used in place of virgin aggregate, or as rejuvenators. Crumb rubber, generated from recycled tires, has been demonstrated to improve the fatigue resistance and flexural strength of asphalt mixes that contain RAP. In California, legislative mandates require

2024-417: Was just a square clearing with an east-west runway. The popular name comes from the layout of the airport's runway system, which was a single piece of asphalt mostly in the shape of an hourglass (3 overlapping runways) which started construction in late 1941 and completed February 1, 1942. The hourglass field was primarily used for carrier landing practice during World War 2. Around the time of World War II

2070-468: Was organized by thousands of fliers that were spread around town at coffee shops, car clubs, movie theaters and other places where people would gather. These fliers stated that there would be a "mass protest meeting" on El Cajon Boulevard on Sunday August 12. The news was also spread by the a DJ named Dick Boynton on the local radio station. Two days later the police arrested a printer by the name of Herbert Sturdyvin, 20, on suspicion of conspiracy of printing

2116-671: Was refined and enhanced by Belgian-American inventor Edward De Smedt . Edgar Purnell Hooley further enhanced the process in the UK where the term tar macadam, shortened to tarmac was coined, after the name of his company Tar Macadam (Purnell Hooley's Patent) Syndicate Limited derived from the combination of tar and Macadam gravel composite mixtures. The terms asphalt (or asphaltic ) concrete , bituminous asphalt concrete , and bituminous mixture are typically used only in engineering and construction documents, which define concrete as any composite material composed of mineral aggregate adhered with

#591408