Blog Archives

Summary of Part II on the Gradation of the Coarse Aggregate Fraction

Posted by on 14/ 11/ 15

A fixed coarse aggregate content was assumed in Part II of the design example. We explored the subdividing of the coarse aggregate fraction and its subsequent conse­quences. We saw that the shape of the gradation curve in the area larger than 2 mm has great significance on the properties of an SMA mixture. Thus, by increasing the predominance of very coarse grains, we increase the following:

• Resistance to permanent deformation (in general, but not in all cases)

• The content of VMA

• The binder quantity

• The permeability of a course

A final remark: setting up the skeleton using only the coarsest particles—namely, creating a single-sized mixture—will bring about possible problems with the inter­locking of the skeleton grains; contrary to expectations, such a course will be of po...

read more

Jointed Rigid Pavement

Posted by on 14/ 11/ 15

Jointed rigid pavements tend to crack at 13 to 25 ft (4 to 8 m) lengths because of (1) initial shrinkage after placement as excess water evaporates, (2) temperature-induced expansion and contraction resisted by friction with the subgrade, (3) curling and warping caused by temperature and moisture differences between the top and bottom of the slab, and (4) load – induced stresses.

As slabs contract as a result of seasonal temperature changes, cracks form and widen, or formed joints widen, allowing incompressible materials into the cracks or joints. Subsequently, expansion is hindered and pressure is built up in the pavement. This pressure can result in pressure spalling or even blowups...

read more

GOING UP

Posted by on 14/ 11/ 15

Walls Create Space

The wall-framing phase of a homebuilding project is an exciting one. Piles of lumber scattered around a flat platform are soon assembled into a complex skeleton that defines the shape and size of a home’s interior spaces. For the first time, it’s possible to experience the look and feel of a new house. We’re still a long way from move-in, but the completed frame is a dramatic step forward.

Framing walls requires an abundance of energy, good teamwork, and real presence of mind. As you’ll see on the following pages, it takes quite a few steps to get the walls up and ready for roof trusses...

read more

Magnesium-Based Cements

Posted by on 14/ 11/ 15

Before the widespread use of Portland cement, magnesium oxide-based cements were among the world’s most popular cement products. By the late 19th century, the use of Portland cement had spread around the world. Although Portland cement has now essentially cornered the market, it has some inherent drawbacks when compared to the magnesium oxide-based cements used by our ancestors. Portland cement manufacturers are currently allocating enormous R&D funding to overcoming deficiencies that impact the envi­ronment, human health, and the strength, dura­bility, and usability of Portland cement. Billions of dollars are being spent in an effort to make Port­land cement do what magnesium phosphate – and magnesium oxychloride-based cements do natu­rally.

No one ever purposely set out to make a pr...

read more

Thermal Conductivity Sensors

Posted by on 14/ 11/ 15

Thermal conductivity sensors (TCS) are used to indirectly relate matric suction to the thermal conductivity of a porous medium embedded in a mass of unsaturated soil. Any change in the soil suction results in a corresponding change in the water content of the porous medium (governed by its characteristic curve). The thermal conductivity of a rigid porous medium is a direct function of the water content. Therefore, if the thermal conductivity of the porous medium is measured, the matric suction of the soil may be indirectly determined by correlation with a predetermined calibration curve. Figure 3.14 shows the main components of a modern commercial TCS.

Thermal Conductivity Sensors

Fig. 3.14 Picture and schema of a thermal conductivity matric suction sensor (TCS)...

read more

COMPOSITE FLOOR TRUSSES

Posted by on 14/ 11/ 15

COMPOSITE FLOOR TRUSSES

Girder systems may be designed with either dimen­sion or laminated lumber. They are most common in the Northwest, where dimension timber is plentiful. Girder floor systems are similar to joist floor systems except that girders, which are wider than joists, can carry a greater load for a given span and therefore can be spaced at wider intervals than joists. Girders are typically placed on 48-in. centers, so long-spanning subfloor materials such as 2-in. T&G decking or lVs-in. combination subfloor-underlayment are required (see 48).

When used over crawl spaces, girders may be sup­ported directly on posts. Over a basement, a girder system may be supported on posts or may bear on a wall or a beam like a joist system...

read more

Ace

Posted by on 14/ 11/ 15

WHETHER YOU’RE AN EXPERIENCED BUILDER, A HABITAT VOLUNTEER, ora novice carpenter, the wall-framing phase of a homebuilding project is especially exciting. Piles of lumber scattered around a flat platform are soon assembled into a complex skeleton that defines the shape and si/.e of a homes interior spaces. For the first time, it’s possible to experience the look and feel of a new house, identifying where bed­rooms and bathrooms will be and enjoying the view through rough window open­ings. We’re still a long way from move-in condition, but the completed frame is a dramatic step forward.

Although quite gratifying, framing walls is also hard, intense work. It requires an abundance of energy, good teamwork, and real presence of mind...

read more

RIGID PAVEMENT

Posted by on 14/ 11/ 15

Rigid pavement can be constructed with contraction joints, expansion joints, dowelled joints, no joints, temperature steel, continuous reinforcing steel, or no steel. Most generally, the construction requirements concerning these options are carefully chosen by the owner or the public entity that will be responsible for future maintenance of the pave­ment. The types of joints and the amount of steel used are chosen in concert as a strategy to control cracking in the concrete pavement. Often, the owner specifies the construction requirements but requires the designer to take care of other details such as intersection jointing details and the like. It is imperative that a designer understand all of these design options and the role each of these plays in concrete pavement performance.

The c...

read more

Grading of the Coarse Aggregate Fraction versus the Distribution of Air Voids

Posted by on 14/ 11/ 15

Investigations carried out in the Netherlands (Voskuilen, 2000) have proved that the gradation within the coarse aggregate fraction exerts an impact on the distri­bution of voids in a mix. Briefly, the conclusions drawn in the Netherlands are as follows: [25]

6.3.2.2.3 Determining the Size of Active Particles

After exercises in changing ratios within the coarse aggregate fraction, it is time to explore the question of the influence of the size of active particles on the mix. As we remember from Chapter 2, active grains are those making an aggregate structure that carries loads. The problem of actively setting up the SMA skel­eton by particles of a certain fraction—say, 2/4 (or 2/5.6) mm—was discussed there...

read more

. Exterior Wall

Posted by on 14/ 11/ 15

To square a wall, secure the bottom plate as shown, then move the top of the wall until the diagonal dimensions are equal. Once the wall is square, secure it with two nails through the double plate into the floor.

. Exterior WallNail on the inside of the bottom plate so the nails will hold the wall in position while it is being stood. The bottom plate should be nailed so that it’s in line with the wall chalk line. Then, when the wall is raised, it will be in the right position.

. Exterior WallПодпись: Sheathing: place, cut openings, and nail.Подпись: Wall sheathing. Exterior Wall. Exterior WallCover the entire wall with sheathing, then rout window and door openings with a panel pilot router bit (see illustration). Save the leftover pieces of sheathing for small areas and filling in between floors.

If the first floor exterior walls can be reached from the ground, then the sheathing is not installed until after the walls ...

read more