Blog Archives

The Alexandrian heritage

Posted by on 18/ 11/ 15

Carthage is defeated in 202 BC, at the end of the Punic wars. This leaves Rome with­out a rival in the western Mediterranean, so she immediately begins her expansion toward Greece and the Orient. This evolution is inexorable, despite some temporary set­backs due to resistance such as that of the king of the Pontus, Mithridate Eupator (in whose land the remains of one of the first water mills has been found, as noted in the preceding chapter). The annexation of Egypt by Augustus in 31 BC effectively ends the Roman expansion toward Asia. After the occupation of the coast of North Africa at the end of the 1st century AD, the Mediterranean becomes the mare nostrum, a sea that is entirely bordered by Roman lands.

One can clearly see the appearance of the Alexandrian heritage in Roman techniqu...

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CLOSING IN

Posted by on 18/ 11/ 15

Windows, Doors, Siding, and Exterior Trim

Each phase of a homebuilding project offers a new set of challenges and rewards, but the work that we do in this chapter is especially exciting. The big, stick-framed box we’ve built is about to receive a beautiful skin, with windows and doors added to make it weatherproof. By the time we’ve fin­ished the tasks in this chapter, the house will show off its finished exterior appearance. And with the inside protected from the elements, we are free to take on all the interior work ahead.

As I mentioned in Chapter 4, it’s common practice in some parts of the country to sheathe wood-framed walls before they are raised rather than after...

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Other Remarks

Posted by on 18/ 11/ 15

It is worth remembering the following when mechanically spreading a layer of SMA mixture:

• Manually scattering mixture over the mechanically placed mixture is not permitted.

• Allowing any vehicles other than rollers on the hot mixture, before it is finally compacted and its temperature drops below the expected level, is not permitted.

• The end of a working lot (the transverse joint) should be finished by cutting; suitable joint bonding ought to be secured prior to laying the next lot—for example, by applying a PMB tape or a special compound (Figures 10.8 and 10.9).

• When executing the SMA layer in separate lanes (i. e., each traffic lane separately), the edge of the first layer should not be cut vertically but with a falling gradient, e. g., of 3:1 (height: width).

• Longitud...

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Rehabilitation of Rigid Structures

Posted by on 18/ 11/ 15

Rigid culverts with invert wear may be rehabilitated by paving the lower quadrant of the culvert. Where there is no reduction in the structural capacity of the culvert, the invert may be protected from further erosion by placing portland cement concrete or by using shotcrete. Welded wire mesh may be used to strengthen the culvert where it is necessary to do so. For an unreinforced concrete pipe, this will be the case where there is either significant invert wear or longitudinal cracking. Strengthening of a rein­forced concrete pipe may be deemed necessary where there is significant longitudinal cracking, invert wear, or spalling. Dowels should be drilled into the member to be repaired, to provide anchorage for the welded wire fabric.

Cracks and spalls caused by flexural distress may be re...

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REHABILITATION

Posted by on 18/ 11/ 15

The appropriate method to be used for culvert rehabilitation depends upon the type and size of the culvert, its condition, and hydraulic and economic considerations.

Hydraulic and economic considerations bear on the issue of repair versus replace­ment. If the hydraulic capacity of the culvert is in question, or if a rehabilitation method that would reduce its capacity—either by reducing the waterway or by increas­ing its roughness—is under consideration, a hydraulic analysis is required. In addition, if there will be additional highway construction in the area or if there are plans to widen the roadway in the future, these considerations should be included in the deci­sion of rehabilitation versus replacement.

Pipe replacement is the only method applicable to all pipe types regardle...

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FIXTURES, AND SWITCHES

Posted by on 18/ 11/ 15

Although all UL-rated fixtures, switches, and receptacles will satisfy electrical codes, better – quality devices will last longer. Heavy-duty recep­tacles, for example, have nylon faces rather than plastic and metal support yokes that reinforce the back of the receptacle.

Receptacles. Most household receptacles are rated for 15-amp circuits and wired with 14AWG or 12AWG wire. The NEC specifies 20-amp protection for kitchen appliance, garage, and workshop circuits.

 

The NEC specifies GFCI protection for many locations, including bathroom, outdoor, and kitchen counter receptacles, so there are also 15-amp and 20-amp GFCI receptacles...

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CIRCUIT WIRING

Posted by on 18/ 11/ 15

Copper is the preferred conductor for residential circuit wiring. Aluminum cable is frequently used at service entrances, but it is not recommended in branch circuits.

Individual wires within a cable or conduit are color coded. White or light gray wires are neutral conductors. Black or red wires denote hot, or load­carrying, conductors. Green or bare (uninsulated) wires are ground wires, which must be connected continuously throughout an electrical system.

Because most of the wiring in a residence is 120-volt service, most cables will have three wires: two insulated wires (one black and one white) plus a ground wire, usually uninsulated. Other colors are employed when a hookup calls for more than two wires; for example, 240-volt circuits and three – or four-way switches.

BOXES

There is a ...

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Inspection of Rigid Structures

Posted by on 18/ 11/ 15

Inspection of reinforced concrete pipe should focus on problems with alignment, joints, and the wall.

The alignment of the culvert may be inspected visually. Misalignment may be caused either by poor installation practices or by subsequent settling of the pipe or the backfill. In any case, the pipe should be periodically monitored to ensure that the con­dition does not worsen. Close inspection of the joints may reveal conditions that will lead to an increase in the misalignment of the structure.

Joints should be inspected for cracks, separation, exfiltration, and infiltration. Cracks and separation of joints are detrimental to the culvert only insofar as they increase the possibility of infiltration and exfiltration...

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Laboratory Measurements

Posted by on 18/ 11/ 15

Contaminants may be held both in pore water and on/in the solids fraction of soil samples. Often it is desirable to know how much contaminant could be released from the sample. Simple separation of the pore water (e. g. by a centrifuge method) will not enable us to know how much contaminant might be released from the solids by desorption and leaching. To find this information, extraction tests of some kind need to be performed in which the contaminant is encouraged to move from the solids into the liquid phase by the arrangement of the tests. This is the subject of the first part of this section. Once the liquid phase has been extracted, chemical tests can be performed on the contaminated water – this is described in the second part of this section.

7.6.1 Extraction Methods

7.6.1...

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Paver

Posted by on 18/ 11/ 15

The appropriate passage of material through the paver plays a key role in the proper spreading of a mixture. After starting in the hopper, the mixture is moved by slat con­veyors (with flow gates in older equipment) to augers and then under a screed. During each of these stages the following significant parameters affect the final result:

• The hopper should be fitted with independently lifting wings, and its shape should eliminate places from which the mixture does not slide to the slat conveyor. Such “dead areas” or “cool corners” create accumulations of cool mixture and cause other problems (see Chapter 11). For the same reasons, the insulation of wings is desirable.

• Care should be taken so that the mixture does not adhere to the walls of the hopper where it cools off fairl...

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