BULLDOZERS PARTS AND DETAILS BASICS AND TUTORIALS

BULLDOZERS PARTS AND DETAILS BASIC INFORMATION
What Are The Parts Of The Bulldozers?

Bulldozers are great help in civil and structural engineering constructions. It is one of the most visible and most prominent machines in the construction site.

Bulldozers are these machines consist of a track or wheel mounted power unit with a mould blade at the front which is controlled by hydraulic rams. Many bulldozers have the capacity to adjust the mould blade to form an angledozer and the capacity to tilt the mould blade about a central swivel point.

Some bulldozers can also be fitted with rear attachments such as rollers and scarifiers.

The main functions of a bulldozer are:-

1 . Shallow excavations up to 300 m deep either on level ground or sidehill cutting.

2. Clearance of shrubs and small trees.

3. Clearance of trees by using raised mould blade as a pusher arm.

4. Acting as a towing tractor.

5. Acting as a pusher to scraper machines


Bulldozers (‘dozers’) are used for cutting and grading work, for pushing scrapers to assist in their loading, stripping borrowpits, and for spreading and compacting fill. The larger sizes are powerful but are costly to run and maintain, so it is not economic for the contractor to keep one on site for the occasional job.

Its principal full-time use is for cutting, or for spreading fill for earthworks in the specified layer thickness and compacting and bonding it to the previously compacted layer. It is the weight and vibration of the dozer that achieves compaction, so that a Caterpillar ‘D8’ 115 h.p. weighing about 15 t, or its equivalent, is the machine required; not a ‘D6’ weighing 7.5 t which is not half as effective in compaction. The dozer cannot shift material very far, it can only spread it locally.

A dozer with gripped tracks can climb a 1 in 2 slope, and may also climb a slope as steep as 1 in 1.5 provided the material of the slope gives adequate grip and is not composed of loose rounded cobbles. On such slopes of 1 in 1.5 or 1 in 2 the dozer must not turn, but must go straight up or down the slope, turning
on flatter ground at the top and bottom.

It is dangerous to work a dozer (and any kind of tractor) on sidelong ground, particularly if the ground is soft. Dozers cannot traverse metalled roads because of the damage this would cause, and they should not be permitted on finished formation surfaces. Sometimes a flat tracked dozer (i.e. with no grips to the tracks) can be used on a formation if the ground is suitable.


A Typical Bulldozer and Its parts is presented below:

This article is part of civilengineeringdegrees.net power equipment basic information series.

CEMENT HYDRATION AND CONCRETE CURING BASICS AND TUTORIALS

CEMENT HYDRATION AND CONCRETE CURING BASIC INFORMATION
Cement Hydration And Concrete Curing Information

Concrete curing is not simply a matter of the concrete hardening as it dries out. In fact, it is just the opposite. Portland cement is a hydraulic material. That is, it requires water for curing and can, in fact, fully cure to a hardened state even if it is completely submerged in water.


Portland cement is anhydrous—it contains no water or moisture at all. The moment it comes in contact with water, a chemical reaction takes place in which new compounds are formed. This reaction is called cement hydration.

The rate of hydration varies with the composition of the cement, the fineness of the cement particles, the amount of water present, the air temperature, and the presence of admixtures. If the mixing water dries out too rapidly before the cement has fully hydrated, the curing process will stop and the concrete will not harden to its intended strength.

Curing will resume if more water is introduced, but at a slower rate. Hydration occurs more rapidly at higher air temperatures. Cement hydration itself generates heat, too. This heat of hydration can be helpful during cold-weather construction, and potentially harmful during hot-weather construction.

The chemical reaction between water and cement first forms a paste which must completely coat each aggregate particle during mixing. After a time, the paste begins to stiffen or set, and after a few hours has lost is plasticity entirely.

The rate of this setting, however, is not the same as the rate of hardening. A Type-III high-early-strength cement may set in about the same time as a Type-I general-purpose cement, but the Type III hardens and develops compressive strength more rapidly after it has set.

Concrete normally cures to its full design strength in 28 days. Curing is slower in cold weather, and at temperatures below 40°F, the concrete can be easily and permanently damaged if it is not properly protected.

Concrete must be kept moist for several days after it is placed to allow the portland cement in the mix to cure and harden properly. Concrete that is not kept moist reaches only about 50% of its design strength. Figure 2-19 shows the differences in concrete strength for various periods of moist curing.

If it is kept moist for at least three days, it will reach about 80% of its design strength, and for seven days, 100% of its design strength. If the concrete is kept moist for the full 28- day curing period, it will reach more than 125% of its design strength.