Concrete precast

In many precast concrete components the conventional reinforcement is non-, or semi-structural, and is intended mainly for crack control. The cracking in question 

Traditionally, steel fibres have been used for this purpose, for example Magnetti etal. [86], In recent years, polymeric fibres have also been applied, and this was 

Another type of application in the precast industry is the use of thin sheets of fibre reinforced cements as permanent formwork (known also as lost formwork and stay-in-place forms) for reinforced concrete components [87,88], In this case the composite provides also finishing and protection to the reinforced concrete member, in particular with respect to corrosion of steel in concrete. The composite can also be taken into account as a tensile reinforcement, and thus lead to savings in steel. 

A variety of special precast components, such as utility poles [90], ducts, pipes have been produced from glass fibre reinforced cements, using technologies such as spray and filament winding. 

---

N. Dobbs and co-workers, "Design of Steel, Masonry and Precast Concrete Stmctures to Resist the Effects of HE Explosions" in 17th Annual Dept, of Defense Explosive Safety Seminar,NT S, Springfield, Va., 1976. 

Type I (Normal). This is the general purpose Pordand cement used for all appHcations where special properties are not needed. Common appHcations include concretes for paving, building doors, roof decks, reinforced concrete buildings, pipes, tanks, bridges, and other precast concrete products. In 1989 Type I and Type II accounted for over 92% of the Pordand cement produced in U.S. plants. Exact data are not available that separate Type I and Type II Pordand cement, but it can be assumed that Type I production was much greater than Type II. 

This type of construction uses a steel or concrete frame and precast concrete wall panels. Many details have been developed for precast concrete walls. Details for precast walls should be in accordance with the seismic requirements of ACI 318, Chapter 21. 

FIGURE 10.7 Precast Concrete Panels Connection Details... 

This type of construction uses precast concrete walls with steel or concrete frames (Figure 4.2). The frame resists all vertical loads and precast shear walls resist lateral loads. Ductile connections for precast panels are an important consideration. Precast panels are made with embedded steel connection devices attached to the building frame by bolting or welding. The roof is usually a concrete slab on metal deck. The metal deck is attached to steel framing by studs or puddle welds. Tins type of construction can be economically designed to withstand blast loading on the order of 7 to 10 psi (48 to 69 kPa) side-on overpressure. 

Cast-in-place concrete construction (Figures 4.3 and 4.4) is used to resist relatively high blast overpressures where precast concrete is not economical or practical. Horizontal loads are resisted by shear walls. The structure depends on a structural steel or concrete frame to support vertical loads. Thickness of the concrete... 

Precast concrete piles will be used with an allowable compression force of 80 kips (356 kN) and an allowable tension force of 50 kips (222 kN), both with a safely factor of 3 against ultimate capacity. Because battered piles will resist all lateral forces without the need for passive soil pressure, a safety factor of 1.2 may be used. Permissible blast capacities will be adjusted accordingly. 

Composite grid to replace steel reinforcement of precast concrete panels. 

Concrete masonry is simply the name given to the cement building blocks employed in the construction of many homes, and it is simply a precast block of cement, usually with lots of voids. Precast concrete is concrete that is cast and hardened before it is taken to the site of construction. Concrete sewer pipe, wall panels, beams, grinders, and spillways are all examples of precast cements. 

The use of WRAs (normal, mid-range and high-range) in ready-mixed and precast concrete to reduce water content and increase workability is described in the following pages. 

The process of precast concrete manufacture provides conditions which are more amenable to the monitoring of cost benefits afforded by the use of admixtures. The following benefits have been found ... 

Superplasticizers have been used successfully to achieve savings in concrete consolidation in heavily reinforced precast concrete sections, e.g. the high-quality finish required for the precast tube elements (carrying the mechanical and electrical services) used in the construction of the Montreal Olympic Stadium was achieved through the use of a superplasticizer. Fig. 7.41 shows the high density of steel reinforcement used in these structures. 

In this section, information on the operational aspects pertaining to the use of admixtures in the field is presented. In addition to details concerned directly with the physical aspects of batching and dispensing equipment and their operation, considerable attention is directed to the material-related problems that arise in the use of admixtures both in mainstream and special applications. It also offers guidance in the selection, use and control of uniformity of the product. Most of the issues discussed here apply equally to the three major fields of concrete construction, namely, site-batched and -placed concrete, ready-mixed concrete, and precast concrete. 

Impregnated wood, glass-reinforced polyester or precast concrete are acceptable materials for water basin. 

Fan and water distribution decks are to be of precast concrete and designed for a live load of 60 lb/ft2 plus any concentrated or distributed dead loads, such as fans, motors and maintenance equipment. 

---