Blog Archives

TESTING THE FINISHED LAYER

Posted by on 19/ 11/ 15

A series of acceptance tests are carried out after finishing the placement of a mix­ture. They usually comprise measuring the content of air voids and the compaction factor, conducted on specimens of cores taken from the finished pavement. In many countries, nuclear density gauges are used for testing the homogeneity of compac­tion. When this is the case, cores are only required for calibration and comparisons with the nuclear gauge. Other properties checked on finishing the layer are skid resistance and the macrotexture depth. The methods used for these tests depend on national specifications.

10.6.1 Air Voids in a Compacted SMA Layer

The content of voids in the compacted SMA layer is the most commonly found parameter checked at the acceptance of a finished layer and is always mentioned...

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Determinations of availability and unavailability

Posted by on 19/ 11/ 15

Determination of the availability or unavailability of a system requires a full accounting ofthe failure and repair processes. The basic elements that describe such processes are the failure density function ft (t) and the repair density func­tion gt (t). In this section computation of the availability of a single component or system is described under the condition of an ideal supportability. That is, the availability, strictly speaking, is the inherent availability. Discussions of the subject matter for a complex system are given in Chap. 7.

Consider a specified time interval (0, t], and assume that the system is ini­tially in an operating condition at time zero...

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Other aqueducts in the Roman Empire

Posted by on 19/ 11/ 15

The panorama of Gallo-Roman aqueducts that we have just described represents the diversity of situations and solutions adopted throughout the Roman Empire. Table 6.1 gives an incomplete list of the numerous Roman aqueducts that have been discovered and studied. It would be impossible to describe all of them. To the best of our knowl­edge, the longest one is at Apamea-on-Orontes in Syria, built in 116 or 117 AD as part of the broad reconstruction after the earthquake of 115 AD.[246] But another aqueduct also merits our attention. It is the aqueduct of Carthage, one of the marvels of Roman archi­tecture in Africa, and among the longest of all the Roman aqueducts in the western world (Figure 6.18).[247]

Carthage is destroyed by the Romans at the end of the Punic wars, then rebuilt in 29 BC ...

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Final Remarks

Posted by on 19/ 11/ 15

The layer edge should be rolled with a machine fitted with a side-roll; this will enable suitable compaction of the area close to the edge. The drums of a roller should be moistened with water, which should protect them against mastic adhesion and drag­ging particles out.

10.5 pLAcEMENT of sMA IN KOMPAKTASPHALT TEcHNIQuE

The Kompaktasphalt method consists of placing two layers of a pavement in one pass of a specially designed paver (Figure 10.12). Typically the paver places both an SMA and asphalt concrete in one pass. The first attempt at such a laydown occurred

image104

FIGURE 10.12 Special paver for the placement of two layers in one pass with an SMA wearing course (A2 highway in Poland), an example of Kompaktaspha. lt technology. (Photo courtesy of Konrad Jablohski.)

in 1995 Germany an...

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Organic Mastics

Posted by on 19/ 11/ 15

Organic mastics are either water – or petro­leum-based adhesives that consist of a bonding agent and a liquid vehicle. For petroleum – based mastics, the vehicle is a solvent, usually toluene. These formulations are highly toxic and flammable and are not recommended for use in a healthy home.

Organic mastics enjoy widespread popu­larity because they are inexpensive, stickier than thinsets, and allow the quickest installa­tions. However, they do not have the strength, flexibility, or water resistance of thinset or thickset applications. Because they are applied in a very thin layer, they do not have leveling capabilities and are suitable only for applica­tion over flat surfaces such as plywood or dry – wall...

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Execution

Posted by on 19/ 11/ 15

So far, this chapter has described the sensibility, the principles, and the tools inherent to successful architecture. This next section explains the actual pro­cess of subtractive design and relevant considerations. Compared to what is involved in producing large houses, planning a little home is relatively challenging. As stated earlier, a smart, little dwelling is just like an oversized house with the unnecessary parts removed. Editing a structure down to its essence takes patience, but so long as one has this and abides by these instructions as well as necessity, the effort will not go unrewarded.

Get the right tools. There are as many techniques for putting architec­tural ideas down on paper (or screen) as there are people putting them down there. The best way I have found is with a...

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Time Available for Compaction

Posted by on 19/ 11/ 15

The time available for compacting the layer depends mainly on the following condi­tions during placement:

• The mixture temperature behind the paver

• The air and surface temperatures and wind velocity

• The layer thickness

The matters of temperature are elaborated on in Section 10.3.2.

In extremely adverse weather conditions, the time for compacting is counted in minutes and is often less than 5 minutes. After that time, the mixture temperature falls to a level at which the high viscosity of binder makes the movements of the mix­ture particles impossible. If the SMA layer has to be placed in difficult conditions, the following organizational issues should be remembered:

• Using the best possible insulation during SMA mixture delivery

• Closely coordinating the mixture deliveries...

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Adding Outlets to Existing Circuits

Posted by on 19/ 11/ 15

Adding an outlet may be relatively simple if you can access an existing outlet and run a length of cable to a new outlet in the same wall cavity. But even the simplest setup needs a bit of planning— and some exploration—beforehand.

IMPORTANT PREP STEPS

Here are some tasks to do before working in an existing circuit:

► Check local electrical codes, which may not allow extensions of ungrounded circuits. The NEC forbids tying into specialized kitchen, bathroom, or dedicated-appliance circuits.

The circuit you tie into must be a 15-amp or

20- amp general-use or lighting circuit.

► Using a circuit map like that shown on

p. 234 will help you calculate how much power the new circuit will draw...

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Alternatives to Gypsum Board

Posted by on 19/ 11/ 15

Alternatives to paper-backed gypsum board are now available. The following products may be used to replace it and are especially use­ful in applications where moisture conditions may promote mold growth:

• Dens Armor Plus is an alternative to regu­lar cardboard-backed panels. It is paper­less, faced on two sides with a glass mat, and highly mold resistant.

• Magnesium oxide boards: Currently these products are being manufactured in China. They can be used to replace gypsum board, plywood, cement boards, and oriented strand board (OSB). They resist moisture, bugs, fungus, mold, and fire. Products are available in North America under the prod­uct names Dragonboard, MagBoard, and Strong-Enviro Board.

Tile

Tile is generally an inert and healthful floor, wall, and counter surfacing mate...

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Water Influence on Bearing Capacity

Posted by on 19/ 11/ 15

8.2.1 Different Types of Road Structures Versus Sensitivity to Water

Road pavements are multilayer structures (see Fig. 1.5) generally comprising a sur­face course and one or more asphaltic or granular base layers, resting on a pavement foundation. Chapter 1 introduced the major pavement layers – the foundation, the sub-base, the pavement base and a surfacing (see Section 1.4.2).

Water permeability should normally increase from the top of the pavement (the asphalt or concrete layers) downward until about 0.7 m depth (see Chapter 5). Oth­erwise water would accumulate onto the low permeability layer and keep the upper layer wet; freezing of the accumulated water might then unbind the upper layer. This would decrease it’s bearing capacity and service life...

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