Aims and Objectives

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The main aim of this book is to increase the knowledge about water in the sub­surface road environment so as to improve highway performance and minimise the leaching of contaminants from roads. Improvement of pavement performance will lead to less road closures, better use of the road network, longer service life and more effective transportation of goods and people.

This aim can be further divided into the following four secondary objectives:

• to describe the most up-to-date understanding of water movements and moisture conditions in unbound pavement layers and subgrades for different types of road constructions in various climatic conditions,

• to explain the relationship between the mechanical behaviour of materials/soils and their permeability[2] and moisture condition,

• to report on advanced modelling of water movement and condition in the sub­surface pavement environment developed from laboratory analysis and field studies,

• to inform about the identification, investigation and control of contaminants leaching from soils, natural aggregates and by-products in the sub-surface layers.

It is important to add that this book is NOT about road surface drainage. There are many books that address this topic, e. g. Ksaibati & Kolkman (2006), whereas this book aims to concentrate on sub-surface water. Inevitably, there is some overlap be­tween the two aspects but, in this book, the information on runoff is only that neces­sary to complete a coverage of the sub-surface condition. Regarding contamination, traffic is, of course, a significant source too (see Chapter 6, especially Fig. 6.1) but the reduction in contaminants from that source is beyond the scope of this book. Rather, the aim is to understand what happens, or should happen, to contaminants in the highway environment.

How Much More Will It Cost to Build a Healthy Home?

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Assume for a moment that you are house hunt­ing. Your real estate agent contacts you and is very excited about a real bargain, a house go­ing for 20 percent less than market value. Upon further inquiry, you learn that the house con­tains lead paint and asbestos insulation and sits on a bed of radon-emitting granite. It is lo­cated in a flood plain, has poor drainage, and smells a little moldy. The previous owners have died of cancer. With this new information, the home now seems to be less than a bargain.

Our health is priceless and when buying, renovating, or building a new home its ability to nurture health should be our top priority. Unfortunately we are faced with a building/ real estate industry that does not make health a top priority. Builders often include many amenities such as three-car garages, whirlpool baths, extra rooms, and fancy fixtures, fau­cets, and appliances while ignoring even sim­ple health safeguards such as nontoxic paints, floor drains, and carbon monoxide moni­tors. Appraisers focus primarily on size rather than quality, and real estate agents often pro­mote the visual cosmetics of the home. How­ever, much of what makes a home healthy is not visible to the naked eye. This book is about how to avoid substances and building prac­tices that are as harmful to your health as lead, asbestos, mold, or radon but are commonly used in construction today. It is for the home­owner, builder, and home designer who wish to make health a priority in creating homes that are responsive and nurturing for all who live in them.

How much more will it cost to build a healthy home? This is frequently the first question posed to Paula by her clients. The an­swer usually lies somewhere between zero and 25 percent more than standard construction. In some cases, little or no extra money is re­quired to build and maintain a healthy home. A few examples are listed below:

• Additive-free concrete costs no more than concrete with toxic admixtures, provided that climatic conditions are appropriate for the project.

• Zero-VOC paints are now readily avail­able through most paint manufacturers.

• Shortening wiring runs with careful plan­ning not only will reduce exposure to electromagnetic fields but also will save money.

• Unscented and nonchlorinated cleaning products cost no more and can be just as effective as compounds containing harsh chemicals.

In other cases, healthier alternatives are more expensive initially but more economical in the long run. For example:

• The most inexpensive types of roofing to install are comprised of tar and gravel or asphalt shingles, but the useful life of these products is much shorter than that of many of the less toxic roofing systems discussed in Division 7.

• Although forced-air heating is less expen­sive to install, a properly designed gas-fired, hydronic radiant floor heating system is not only more comfortable and healthier but also virtually maintenance-free. Higher initial installation costs will be outweighed over time by lower heating bills and more comfort.

In some areas your decision to “go healthy” will cost more, and you will be faced with some difficult choices. We will try to offer you facts and a range of alternatives so that your choices can be well informed. In many instances there is no right answer. Sometimes your decision will come down to a trade-off between luxury and health. But then, what is luxury without health? You could ultimately spend a for­tune on medical bills and lose your quality of life, as have the people who have shared their stories with us in the case studies throughout the book.

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Furthermore, as responsible citizens of the world we must weigh our building choices from an environmental perspective. The cost to the environment of many current building practices is astronomical. Our children and grandchildren will ultimately pay for our ex­cesses and waste. To weigh the environmen­tal cost of our choices, we must consider their lifecycle impacts:

• We can choose products that are locally produced from renewable resources.

• We can choose to build less by building with well-designed and efficient plans.

• We can build-in energy efficiency and lon­gevity.

• We can make solar heating, solar electric­

ity, water catchment, and ecological waste management our budgeting priorities.

Some History

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In Europe road construction may date back as far as 3,500 years ago. These early roads were probably largely for ceremonial purposes, over short distances, and may have carried little, if any, wheeled traffic. It was not until the growth of the Ro­man Empire that a large network of engineered pavements was first constructed (Fig. 1.1). Such was the desire to secure the Empire against enemies and to enhance trade that, at the peak time, about 0.5 km was being built daily. Although foot and hoof traffic probably predominated, those roads were certainly used for wheeled vehicles too.

The engineers responsible for these pavements understood some important truths about pavement drainage – truths which, in practice, sometimes are still not recog­nised today. Figure 1.2 shows a cross section of a high quality Roman road. It illustrates that its designer:

A. R. Dawson

University of Nottingham, Nottingham, UK e-mail: andrew. dawson@nottingham. ac. uk

A. R. Dawson (ed.), Water in Road Structures, DOI 10.1007/978-1-4020-8562-8_1, © Springer Science+Business Media B. V. 2009

Summa crusta – grouted polygonal flagstones on best roads or rough cobbling ongood roads, absent elsewhere

Nucleus – compacted sand/gravel mix I++1 ®tatumen – larger stones sometimes

sometimes set in a pozzolanic mortar set in a mortar. Usually absent

Rudus – stabilised rubble and [—— 1 Agger – stone and soil earthworks to

stones < 50mm in size • * • lift road above surrounding ground

Some History

Fig. 1.1 Roman principal road network (Lay, 1992). Reproduced by permission of M. G. Lay

 

• provided cross-fall to help shed surface water to the margins rather than to soak in,

• raised the pavement well above the groundwater level of the surrounding ground so as to keep the amount of water in the embankment low and the effective stress (and, hence, soil strength) high,

• provided lateral ditches to prevent water table rise in wet periods and to convey draining water away from the construction.

 

Polygonal flagstones / rough cobbling

Edge stone sometimes cemented

in place as restraint

 

Typical

Dimensions

 

>2000

 

Vierteagus-

Longitudinal

drain

 

Natural formation

 

□

□

 

7500

 

Fig. 1.2 Cross-section of a high quality Roman pavement (dimensions in mm)

 

Some HistorySome History

Only a small proportion of pavements were built as illustrated, more generally a two layer pavement, comprising nucleus and rudus as explained in the notes to the Figure, was constructed on an embankment (agger – see Fig. 1.2). Despite the econ­omizing on materials, the aim of keeping the construction well-drained remained unaltered.

It was not until the late 1700s and early 1800s that a similar understanding was once again developed. Figure 1.3 shows a cross-section of a main coach pavement as designed by Thomas Telford, the Scottish engineer who worked in the UK and other European countries between about 1800 and 1830. In this design an effort has been made to provide a relatively impermeable surface to prevent water infiltration and a drainable foundation, but the route to lateral drains from these is not well developed.

Despite these early evidences of the understanding that drainage is needed for a well-functioning road, the lesson hasn’t always been fully appreciated. Arthur Cedergren, the American engineer, famously said that “there are three things that a road requires – drainage, drainage and more drainage” (Cedergren, 1974, 1994). He said this many years ago yet, despite many advances in the subject and a huge rise in environmental concerns since he was active, little further has been published in the area. This book is our attempt to redress that omission.

Some History

Fig. 1.3 Facsimile ofTelford’s design for a road from Warsaw to Brzsec1 (Telford, 1838)

1 The text at the top of the figure reads “POLISH ROAD / Transverse Section of the Road between the City of Warsaw and the Town of Brzesc in Lithuania. / This Road (100 English Miles) was constructed by command of the Emperor Alexander I. and finished in May 1825.” Nowadays, Brzesc is known as Brest, and forms the border crossing town between Poland and present day Belarus. It lies about 215 km East of Warsaw (Warszawa) not “100 English miles” ^ 160 km as indicated in the figure.

In the following sections the modern manifestation of the same objectives – to keep pavements dry by limiting ingress and assisting drainage – are introduced. Alongside this updating of the age-old principle of drainage, the modern pavement engineer or geo-environmentalist has to consider the quality of the draining water. What chemical components does the water contain? Is that a problem? Where will they go? The following sections seek to introduce this modern concern as well.

FORMATION OF A COARSE AGGREGATE SKELETON

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What is the reason for developing mixes with stronger mineral skeletons? Surely it is because of heavier and heavier traffic. Not only have axle loads and traffic volumes grown steadily, but the structures of vehicle tires have also changed. The increased popularity of super single tires, for example, has changed the level of stresses applied to pavements. Obviously all those factors magnify the requirements for asphalt mixtures.

A well-known example can be used to present the SMA mineral skeleton struc­ture. If we put some coarse grains in a pot (Figure 2.3), compact and then load them, we shall obtain a structure with high compressive strength, depending on the aggre­gate’s fragmentation (crushing) resistance. A distinctive feature of such a compacted collection of coarse grains is the full and uninterrupted contact between them. This type of skeleton might be desirable for an asphalt surface mixture to provide a strong structure.

Now let us look at Figure 2.4, which presents a schematic showing how a load is carried by a mineral skeleton (of a surface course), assuming full grain contact. The transfer of load by adjacent grains through contact points between the coarse particles may be seen. If these contact points between coarse aggregate particles are not present, the finer particles will have to help carry the load, which results in the

image11

FIGURE 2.3 Vertically loaded grains with side support (as in a crushing resistance test of coarse aggregates).

Подпись:

image13

(b)

development of a discontinuous load transfer by coarse, active grains and potentially weakens the whole structure.

Looking at Figures 2.3 and 2.4, we may notice one of the SMA’s characteristic features. During the compaction process on a construction site, the aggregate grains in the SMA skeleton are forced into direct contact. The coarse grains are brought into contact with each other, making the desired skeleton. Once that contact occurs, further compaction may be harmful. Why? Because it will crush grains. Let us look once again at Figure 2.3. Since the skeleton has already come into existence, further compacting will only lead to crushing grains. In other words, an SMA mixture has
to be skillfully compacted in such a way that the coarse grains are properly placed, securing stone-to-stone contact. This principle applies to compacting energy on a construction site, as well as in a laboratory.

To conclude our examination of the formation of an SMA skeleton, it is worth noting an idea put forth by Van de Ven et al. (2003), who said that there is probably no real, 100% stone-to-stone contact in a newly compacted SMA and that the coarse grains are separated from each other by the finest grains of filler, sand, and thin binder film. This means that there is an enlarging effect[3] of the volume of voids in the stone skeleton. The final arrangement of grains comes after some time under the influence of traffic and temperature of the layer. Small grains (sand and filler) can be crushed or moved, and the void content in SMA decreases.

Let us also bear in mind that the more stable a mineral skeleton is, the less sus­ceptible it will be to deformation. Even when the binder softens due to the increased temperature of the pavement, the layer will not necessarily be deformed if there is an adequate blend of aggregates. The weaker the skeleton and the higher the tempera­ture, the greater is the role of the mastic’s shear strength, and the more reason for reinforcing the mastic with polymers or special fibers.

FEDERAL REQUIREMENTS GOVERNING TRANSPORTATION PLANNING AND THE ENVIRONMENT

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The following discussion is intended to provide an overview of the principal federal requirements affecting the development and maintenance of highways. These include federal laws, regulations, executive orders, agency advisories, policy memoranda, and guidance documents. Federal laws are enacted legislation that establish a set of rules or principles codified in the United States Code (USC). Federal regulations implement federal laws and are codified in the Code of Federal Regulations (CFR). DOT and Council on Environmental Quality (CEQ) regulations implementing NEPA are codified in 23 CFR Part 771 ( United States Department of Transportation Environmental Impact and Related Procedures), and 40 CFR Parts 1500-1508 (Council on Environmental Quality Regulations Implementing NEPA). Environmental regulations have been promulgated by each federal agency. These include regulations promulgated by DOT, the U. S. Environmental Protection Agency (EPA), the U. S. Department of the Interior (USDOI), the U. S. Army Corps of Engineers (USACOE), and the U. S. Coast Guard (USCG), and can be found in the CFRs of the specific agency having jurisdiction over the environmental issue of concern.

In addition to NEPA and the resource-specific legislation summarized in Art. 1.3 of this chapter, there are a number of DOT requirements that affect the planning and envi­ronmental review of highway projects. These include

• Section 4(f) of the Department of Transportation Act of 1966 (23 USC §303)

• The Intermodal Surface Transportation Act of 1991 (Public Law 102-240)

• The Transportation Equity Act for the 21st Century (Public Law 105-178)

• The Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (Public Law 109-59, “SAFETEA-LU”)

• The National Highway Designation Act of 1995 (Section 29 of USC Title 23)

Provided below are brief descriptions of each of these statutes.

Section 4(f) of the Department of Transportation Act of 1966 (23 USC §303, “Section 4(f)”)- Section 4(f) prohibits the administrator of the Federal Highway Administration (FHWA) from approving the use of land from a significant publicly owned park, recre­ation area, or wildlife and waterfowl refuge, or any significant historic site for transporta­tion purposes unless a determination is made that

• There is no feasible and prudent alternative to the use of land from the property.

• The action includes all possible planning to minimize harm to the property resulting from such use.

In addition, supporting information must demonstrate that there are unique problems or unusual factors involved in the use of alternatives that avoid these properties (“Avoidance Alternatives”) or that the cost, social, economic, and environmental impacts, or community disruption resulting from such alternatives reach extraordinary magnitudes.

Section 6009(a) of SAFETEA-LU made the first substantive revision to Section 4(f) since its enactment in 1966. This section of SAFETEA-LU attempts to simplify the Section 4(f) process for projects that have only de minimis impacts on resources protected by Section 4(f). Under the new provisions, once DOT determines that a transportation use of a Section 4(f) resource results in a de minimis impact, analysis of avoidance alternatives is waived and the Section 4(f) process is deemed complete. Guidance for determining de minimis impacts to Section 4(f) resources was issued by FHWA and DOT on December 13, 2005. Section 6009(c) of SAFETEA-LU requires DOT to conduct a study and issue a report on the implementation of these new Section 4(f) provisions. The initial study and report is to address the first 3 years of its implementation.

Intermodal Surface Transportation Efficiency Act of 1991 (Public Law 102-240, “ISTEA”). ISTEA was almost revolutionary in the breadth of how it looked at surface transportation, and the substantive role it played in regard to metropolitan planning orga­nizations, localities, and states. Covering the period 1992 through 1997, it restructured the Federal Aid Highway Program, and placed the emphasis on maintenance rather than whole­sale expansion of the highway network. In creating the Surface Transportation Program, ISTEA brought a new level of flexibility to the planning and implementation of highway and transit projects.

The Transportation Equity Act for the 21st Century (Public Law 105-178, “TEA-21”).

Enacted on June 9, 1998, TEA-21 authorized the Federal Surface Transportation Program for highways, highway safety, and transit for the 6-year period, 1998-2003, and increased the authorized funding level to $218 billion from $155 million under ISTEA. TEA-21 built upon ISTEA, allowing new initiatives, strengthening safety, and encour­aging flexibility in how to maximize performance of the transportation system.

The Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users of 2005 (Public Law 109-59, “SAFETEA-LU”). SAFETEA-LU built upon both ISTEA and TEA-21 included expanded programs in the areas of safety, equity, innovative financing, congestion relief, mobility and productivity, efficiency, and environmental stewardship. Of particular relevance to the consideration of environmental concerns affect­ing the development and implementation of highway projects, it included a number of changes aimed at streamlining the environmental review process. A new category of “participating agencies” was added to provide state, local, and tribal agencies with a formal role in the environmental review process, required that a schedule be defined for the partici­pation of agencies in the project review process, established a 180-day statute of limitations for lawsuits challenging federal agency approvals, allowed for broader state assumption of responsibilities for categorical exclusions from environmental review, exempted the Interstate System from Section 4(f) and National Historic Preservation Act requirements (although individual segments may receive protection), modified the requirements for determining whether the conformity of local and statewide transportation plans conform to the Federal Clean Air Act, and, as previously discussed, included tightly circumscribed exemptions from “Section 4(f)” requirements.

National Highway System Designation Act of 1995 (Public Law 104-59, Section 109 of Title 23, USC). Following the substantial completion of the Interstate System, the trans­portation focus for many states shifted to congestion management and system preservation

projects that involve existing facilities. Working with community stakeholders to preserve and enhance the human and natural environment is a significant component of these pro­jects. To address the challenges resulting from this new emphasis, many state transporta­tion agencies and professional organizations have implemented a “context-sensitive design” (CSD) approach to project development.

The National Highway System Designation Act (Section 109 of Title 23, USC) was enacted in November 1995. The act indicated that design for new construction, reconstruction, resurfacing, restoration, or rehabilitation of highways on the National Highway System (other than a highway also on the Interstate System) may take into account

• The constructed and natural environment of the area

• The environmental, scenic, aesthetic, historic, community, and preservation impacts of the activity

• Access for other modes of transportation

Five pilot states (Connecticut, Kentucky, Maryland, Minnesota, and Utah) were selected to implement the CSD approach to highway design. Principles for CSD can be found on the FHWA website at www. fhwa. got. gov/csd/principles.

SITING A HOUSE

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Often, especially in the city, houses are just plopped down square on the lot with a 15-ft. setback from the street and a 5-ft. side yard to meet building-code requirements. Such a building is a stranger to its land. Sometimes we can do better than that. Ideally, a house should be of the land, not merely on the land. Pay attention to the natural lay of the land, the path the sun takes overhead, the direc­tion from which the prevailing wind blows, the good views that long to be seen, and the bad views that really should be hidden. Try to position the house so that you bring some of the outdoors in, but take into account the landscape’s features. In high-wind areas, the gable end of a house should be turned so it isn’t exposed to the prevailing winds. A great way to get information and inspiration for a new home design is to camp out on your building site. You’ll learn about the path of the sun, prevailing breezes, and nice views.

But building is more than just a physical and intellectual feat. Open your heart, and let it tell you what feels good. Trust your intu­ition. You’ll wind up with a much better house.

Small is beautiful. With some thoughtful design, a small house can have a warm, cozy feel while still offering plenty of conve­nience and privacy.

[Photo by Charles Miller, courtesy Fine Homebuilding magazine,

SITING A HOUSE© The Taunton Press, Inc.]

chair accessibility. And keep in mind that the direction in which a door swings can affect how well a room works and where you can place the furniture.

Other cost-saving strategies have more to do with materials and energy use. Keep the kitchen and the bath on the same side of the house to minimize rough plumbing expenses. In cold regions of the country, run plumbing lines in in­terior walls and enclose the porch as a mudroom to minimize heat loss when coming and going.

To find out which house designs work well in your area, seek advice from local builders, build­ing inspectors, designers, or architects. You’ll find it’s not too difficult to modify basic plans to suit your needs and meet building-code requirements in your region (see Resources on p. 279).

Check with your building department to see whether your house is required to have a garage. Habitat for Humanity’s policy is to “build for people, not cars,” but some municipalities require garages. Sometimes, however, you can
get a variance to build off-street parking rather than a garage.

Design for the future

Consider building a wheelchair ramp leading to an entry or at least providing room for a ramp to be built in the future. An accessible ramp has a 1-in-12 rise (1 ft. of rise for every 12 ft. of length). When designing a house, it’s smart to look beyond what your needs are today. Try to think about and allow for expansion in the future. An addition to the family—whether a new child or an elderly parent—often requires adding a bedroom. If you plan ahead, you’ll have room to expand when you need to. This can save a lot of work and money down the line.

IN THE ATTIC

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Review the notations you made about the roof, chimney, and eaves. Now look for outdoor-indoor relationships such as missing flashing and stains on the underside of roof sheathing.

Подпись: PROTIP In the attic, walk on the ceiling joists or use plank walkways across them. It's unsafe to step anywhere else. Wear a hard hat so roofing nails above don't stab your head—another a good reason for that tetanus shot. You'll likely get dirty crawling around, so you'll be glad you've dressed the part. 1111 Structural condition is the first thing to consider. Are the rafters and ridge sagging? If so, you should hire a structural engineer to see how seri­ous the damage is. This damage likely resulted from too many layers of roofing. Deformed framing may need replacing or additional sup­port, as shown in "Reinforcing a Roof,” on p. 12.

And excessive layers of roofing may need to be stripped off to lighten the load. Caution: Truss – type floor or rafter systems will be weakened if cut into.

If the roof sheathing is bellying (sagging) between the rafters, it’s probably too thin and should be replaced with thicker plywood when you replace the roofing.

Water damage is one of the most common prob­lems. Dark brown stains around the chimney that smell of creosote are probably caused by cracked flue tile, which allowed caustic creosote compounds to work their way through mortar joints. Such a chimney is unsafe to use and must be either relined or replaced.

Cracks in the chimney’s mortar joints may be caused by an undersize or shifting chimney footing—another major cause of flue failure.

Water stains around plumbing vents, dormers, and chimneys are more likely caused by failed or absent flashing. If the wood is damp after a rain, the leaks are active.

Ventilation and insulation are crucially impor­tant but often misunderstood. Attics that lack adequate ventilation are excessively hot in the summer. In winter in cold climates, unventilated attics allow rising water vapor from the living area to collect as frost on the underside of roof sheathing. The frost eventually melts, soaks the sheathing, drips onto the attic floor, and perhaps
soaks through top-floor ceilings. Also in winter, unventilated attics trap warm air from below, which warms the roof, causing snow to melt and run into unwarmed overhangs where it refreezes, resulting in ice dams that can damage roofing and leak behind the siding. Adding soffit, gable, and ridge vents sometimes alleviates these types of problems.

Discolored rafters along the roof-wall joint and delaminated roof sheathing, coupled with stains at the top of interior walls below, are caused by warm, moist air from living spaces. To mitigate the problem, add insulation to the attic floor, improve ventilation, and/or add bath and kitchen vent fans.

Types of attic insulation and standards for their installation are addressed in Chapter 14.

Attic floors and attic insulation may also show roof leaks clearly. And if moisture is migrating up from the living spaces, the insula­tion’s underside may be moldy. Pull up affected sections and see if water has collected there and caused damage.

WALLS

Most home buyers repaint or repaper walls to suit their tastes anyway. So instead of concerning yourself with paint colors or wallpaper patterns themselves, focus on surfaces that suggest under­lying problems that may require remedies. Also, after consulting the notes you recorded outside, study wall-ceiling joints, which also can tell stories.

Water stains on interior outside walls, espe­cially above windows, may have multiple causes: missing outside flashing, gaps between siding and exterior trim, and leaks in the gutters or roof.

Подпись: SafetyПодпись: NEAR WATERПодпись: Kitchen receptacles within 4 ft. of a sink and all bathroom receptacles must be ground-fault circuit interrupters (GFCIs), or whatever your local building code prescribes. They're essential protection against electrical shock.Crumbling drywall or plaster and extensive mold at the top of walls may be caused by exterior leaks or, just as likely, by excessive moisture in the living areas. If the problems are severe, rot- inducing mold may be growing on framing inside the walls. After correcting the sources of mois­ture, you may need to tear out drywall or plaster and replace studs and plates.

Large diagonal cracks in drywall or plaster at the corners of doors and windows may correspond with cracks on the house exterior. Such cracks suggest structural shifting and foundation distress.

Door and window trim that tilts toward a common low point suggests failure in the sub­structure (girder, post, or pad) or in the founda­tion itself.

STEP 3 DESIGN THE HOUSE

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The bumper-sticker slogan, “Live Simply That Others May Simply Live,” speaks to the design aspects of an affordable house. To increase the cost of a house, all you need to do is complicate its design. Affordable housing is, by nature, small and simple. The same formula that makes for a safe house in earthquake country—small, low, and light—makes for an affordable house anywhere in the country.

Money-saving design ideas

The houses featured throughout this book are some of the most cost-efficient designs you can build (see the photo on the facing page). This single-story structure has a simple gable roof

Подпись: Habitat houses are affordable and easy to build. Like most Habitat houses, this one (in Charlotte, N.C.) is designed to make economical use of basic building materials. Подпись: that extends over a small porch, where the main entry is located. On a small lot, where setbacks seriously limit the footprint of the house, you may need to consider a small, two-story design. Habitat for Humanity has a good selection of basic house plans that fit the needs of most families (see Resources on p. 279). Admittedly, the bedrooms are not discotheque size, but you can do your dancing in the living and dining room. In a house, quantity of space doesn’t necessarily translate into quality of life. When my children were young, I enclosed our front porch and made two 5-ft. by 9-ft. rooms. They were cozy, sun-filled spaces; one was used for study, one for music. To my surprise, those two tiny rooms became the most popular parts of the house. A well-sited, well-designed house elicits that kind of reaction (see the sidebar at right). Another way to conserve space and save money is to choose a floor plan that reduces or eliminates hallways. As you look over a house design, remember that doorways need to be at least 32 in. wide—36 in. for easy wheel- Practice building with a scale model. By as­sembling a scale model of your house, you can troubleshoot the building process, solving prob­lems before you begin full-scale construction. You can buy balsa wood in different dimensions and other model-making supplies from a well – stocked hobby shop or craft supply store.

Skeleton of Coarse Aggregates

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In this part of the book we shall deal with the grains within the mix structure that are active in forming a coarse aggregate skeleton. The following significant questions will be answered, too:

• How is a stone matrix asphalt (SMA) mix skeleton formed?

• What does a gap gradation mean?

2.1 DEFINITION OF AN SMA AGGREGATE SKELETON

The notion of an aggregate skeleton of a mixture has a pretty broad meaning. Figure 2.1 shows various types of mineral mixes with different interactions of grains. These range from a sand mix, through mixes where the coarse aggregate particles occupy a more and more substantial share of the volume, and up to a mix consisting entirely of coarse aggregates. The types of aggregates that make up a continuous matrix and form a load-carrying component determine the specific group ranking.

While mixes consisting mainly of an aggregate with sizes up to 2 mm (or 2.36 mm in the United States) (e. g., sand asphalt) are rarely applied, sand-coarse aggregate mixes are within a continuum from mastic asphalt to asphalt concrete. SMA belongs in a coarse aggregates-sand group with porous asphalt, which is the type closest to the straight coarse aggregate type. Mineral mixes with exclusively coarse aggregates make so-called coated macadams, which are seldom used at present.

Now we deal with the first component of an SMA—the skeleton formed of coarse aggregates. Then in Chapter 3 we shall discuss the mastic made of a filler, sand, and binder.

First let us define the term coarse aggregate skeleton. A coarse aggregate skeleton is a structure of grains of suitable size that rest against each other and are mutually interlocked. In Europe, the coarse aggregates are generally taken to be those larger than 2 mm. Following the U. S. option, let us adopt an assumption that a fixed size of 2 mm (2.36 mm in the United States) is not necessarily the lower limit of the coarse aggregate fraction. Why? Well, to meet the structural requirements of a particular grain arrangement (layout), the mechanical resistance of the aggregate blend must be high enough to withstand loads. And this is related to the size of grains, among other factors. So let us agree that a skeleton is made up of adequate size grains but their lower limit is not necessarily equal to 2 mm (2.36 mm). Since the skeleton consists of various coarse aggregate grains, we often use the more universal term coarse aggregate skeleton.

Подпись: Stone skeleton Stone-sand skeleton Подпись: Sand-stone skeleton Подпись: Sand skeleton

Stone skeleton

FIGURE 2.1 Division of mineral mixes into types depending on interactions between sand grains and coarse aggregates. (From van de Ven, M. F.C., Voskuilen, J. L.M., and Tolman, F., The spatial approach of hot mix asphalt. Proceedings of the 6th RILEM Symposium PTEBM’03. Zurich, 2003. With permission.)

image10

Mastic

(binder + filler + sand and fine aggregate + stabilizer)

FIGURE 2.2 Division of SMA into basic components: coarse aggregate (skeleton) and mastic.

To classify all grains of the mineral mix, they may be divided as follows (Figure 2.2):

• Those forming a skeleton (skeleton makers) and carrying loads

• Those filling in the voids in a skeleton and not carrying loads

That division also coincides with the following frequently used terms:

• Active grains (i. e., those forming a skeleton)

• Passive grains (i. e., those filling in voids)

The selection of a sieve to determine a skeleton maker is of great importance for the properties of a newly designed mix. That matter will be treated in detail in Chapter 6.

CUTTING TOOLS

Posted by on 11/ 11/ 15

Cutting material to size, whether wood, drywall, or even metal, is a big part of what a carpenter does. Today, most big cutting jobs are done with power tools. But there are times when a few simple hand tools are more appropriate. That’s why it’s important to keep a few saws, tin snips, and knives on the job site.

Подпись: Japanese handsaws cut on the pull stroke rather than on the push stroke. For best cutting, keep the saw at a 10° angle.

Saws

The saws I keep on the job site are wood-cutting handsaws, a drywall saw, a coping saw, and a hacksaw. I seldom use a handsaw these days, but when I have only a cut or two to make, a hand­saw is faster than plugging in my power saw. My two handsaws are both cross­cut saws. One is for cutting rough wood, like 2×4 studs, and has 8 teeth per inch. My finish saw has 12 teeth per inch and cuts a piece of molding with­out a lot of tearout.

I prefer Japanese handsaws (Japan Woodworker; see Sources on p. 198) over our standard American handsaws. Japanese handsaws are razor sharp and easy to use. Unlike standard handsaws, these saws cut on the pull stroke rather than on the push stoke. This makes them safer, because they won’t buckle and bounce out of the kerf (or saw cut).

Some models even have teeth for cross­cutting on one side of the blade and teeth for ripping on the other. When cutting with a Japanese handsaw, cut at a lower angle than you would using a standard handsaw—about 10° (see the photo above).

I keep a drywall saw in my toolbucket because it’s handy for cutting relatively soft materials like drywall and foam insulation board. A drywall saw tapers to a point, making it ideal for piercing and cutting in the middle of the material rather than from the edge, and its coarse teeth make quick (though ragged) cuts (see the photo on the facing page).

The coping saw is invaluable for trim work. It has a very thin blade with fine teeth and can be rotated to any angle to make intricate or curved cuts.

Occasionally, a carpenter will need to cut through metal. For nails or pipes, you’ll need a hacksaw. It has a hardened blade designed to cut through all kinds of metal, and it’s great for cutting through plastic PVC pipe.

Saw maintenance While drywall saws are cheap and easily replaced, my hand­saws aren’t, so I take good care of them.

I keep them sharp (while it’s possible to do this yourself, I find it easier to send them out to be sharpened) and store them in a cardboard sheath to preserve their sharpness. To keep the blades free from rust or corrosion, clean them with a rag or steel wool and paint thinner, then coat them with three-in-one oil or a silicone spray lubricant. Be mindful when using paint thinner, because it’s toxic. Wear protective gloves, use a mini­mum amount, and don’t dump the excess on the ground.