CONSTRUCTION EQUIPMENTS

The selection of the appropriate type and size of construction equipment often affects the required amount of time and effort and thus the job-site productivity of a project. It is therefore important for site managers and construction planners to be familiar with the characteristics of the major types of equipment most commonly used in construction.

Construction tools and other equipment

Air compressors and pumps are widely used as the power sources for construction tools and equipment. Common pneumatic construction tools include drills, hammers, grinders, saws, wrenches, staple guns, sandblasting guns, and concrete vibrators. Pumps are used to supply water or to dewater at construction sites and to provide water jets for some types of construction.

Automation of equipment

The introduction of new mechanized equipment in construction has had a profound effect on the cost and productivity of construction as well as the methods used for construction itself. An exciting example of innovation in this regard is the introduction of computer microprocessors on tools and equipment. As a result, the performance and activity of equipment can be continually monitored and adjusted for improvement. In many cases, automation of at least part of the construction process is possible and desirable. For example, wrenches that automatically monitor the elongation of bolts and the applied torque can be programmed to achieve the best bolt tightness. On grading projects, laser controlled scrapers can produce desired cuts faster and more precisely than wholly manual methods

Choice of equipment

• Size of the job: Larger volumes of excavation will require larger excavators, or smaller excavators in greater number. 
• Activity time constraints: Shortage of time for excavation may force contractors to increase the size or numbers of equipment for activities related to excavation. 
• Availability of equipment: Productivity of excavation activities will diminish if the equipment used to perform them is available but not the most adequate. 
• Cost of transportation of equipment: This cost depends on the size of the job, the distance of transportation, and the means of transportation. 
• Type of excavation: Principal types of excavation in building projects are cut and/or fill, excavation massive, and excavation for the elements of foundation. The most adequate equipment to perform one of these activities is not the most adequate to perform the others. 
• Soil characteristics: The type and condition of the soil is important when choosing the most adequate equipment since each piece of equipment has different outputs for different soils. Moreover, one excavation pit could have different soils at different stratums. 
• Geometric characteristics of elements to be excavated: A functional characteristic of different types of equipment makes such considerations necessary. 8. Space constraints: The performance of equipment is influenced by the spatial limitations for the movement of excavators. 
• Characteristics of haul units: The size of an excavator will depend on the haul units if there is a constraint on the size and/or number of these units. 
• Location of dumping areas: The distance between the construction site and dumping areas could be relevant not only for selecting the type and number of haulers, but also the type of excavators. 
• Weather and temperature: Rain, snow and severe temperature conditions affect the job-site productivity of labour and equipment.

ASHLAR MASONRY

The stone masonry in which finely dressed stones are laid in cement or lime mortar is known as ashlars masonry. In this masonry are the courses are of uniform height, all the joints are regular, thin and have uniform thickness. This type of masonry is much costly as it requires dressing of stones.

Ashlars masonry is further sub divided into the following types:

• Ashlars fine or coarse ashlar masonry 
• Random coarse ashlars masonry 
• Rough tooled ashlar masonry 
• Rock or quarry faced ashlars masonry 
• Chamfered ashlars masonry 
• Block in coarse masonry 

Ashlar fine or coursed ashlar masonry

In this type of stone masonry stone blocks of same height in each course are used. Every stone is fine tooled on all sides. Thickness of mortar is uniform throughout. It is an expensive type of stone masonry as it requires heavy labour and wastage of material while dressing. Satisfactory bond can be obtained in this type of stone masonry.

Random coursed ashlar masonry

This type of ashlar masonry consists of fine or coursed ashlar but the courses are of varying thicknesses, depending upon the character of the building. 

Rough tooled ashlar masonry

This type of ashlar masonry the sides of the stones are rough tooled and dressed with chisels. Thickness of joints is uniform, which does not exceed 6mm.

Rock or quarry faced ashlar masonry

This type of ashlar masonry is similar to rough tooled type except that there is chisel-drafted margin left rough on the face which is known as quarry faced

Chamfered ashlar masonry

It is similar to quarry faced except that the edges are bevelled or chamfered to 450 for depth of 2.5 cm or more.

Block-in coarse masonry

It is the name given to a class of ashlar masonry which occupies an intermediate place between rubble and ashlars. The stones are all squared and properly dressed. It resembles to coursed rubble masonry or rough tooled ashlar masonry.

Ashlar facing

Ashlar facing is the best type of ashlars masonry. Since this is type of masonry is very expensive, it is not commonly used throughout the whole thickness of the wall, except in works of great importance and strength. For economy the facing are built in ashlars and the rest in rubble.

3D CONCRETE PRINTING

A free form construction process using a layered manufacturing technology has been developed recently with the aim of fabricating building components and structures directly from Computer-Aided-Design (CAD) data sources. In a free form construction process, components are built up without form work unlike conventional concrete construction methods. Building materials are extruded through a nozzle as self-compacting filaments which form horizontal layers, and these layers when laid down sequentially can create large 3D building components. The free form construction process allows the following possibilities. (a) Reduce materials usage and site work; (b) produce novel internal and external finishes; (c) reduce costly remedial works; and (d) give greater design freedom. Possible applications include acoustic structures, structural insulated walls, and multifunctional cladding panels.

A high-performance printing concrete has been developed for an innovative free form construction process that utilizes digital fabrication methods for building large components. The concrete has a maximum particle size of 2 mm and contains up to 1.2 kg/m3 of polypropylene fiber The fresh concrete was successfully printed through a 9 mm diameter nozzle to build free form concrete components by layers. The fresh state of concrete had an open time of 1.5 hours to let it be printed smoothly. The average compressive strength of the cast and in-situ printed specimens were in the range of 100~110 MPa and 80~88 MPa, respectively whilst the flexural strengths were not significantly different and in the range of 12~13 MPa.