Jagvir Goyal takes a look at some enabling equipment that could make the work easier and better in housing projects.
Over the centuries, construction has seen the same old tools in the hands of masons, blacksmiths, carpenters and plumbers. There are hardly any improvements or changes in these tools, except the addition of a drill or two. The construction industry, otherwise, has seen great mechanisation and amazingly vast and efficient machines now dot construction sites. However, housing has somehow been the exception. The science of building has travelled down more through experience than education. It has been a ‘from father-to son’ affair, so far. Only the concreting work has seen a change, from hand-mixed concrete to a machine-mixed one and from manual compaction to vibrator compaction. Yet, efforts have been on to invent some enabling equipment that could make the work easier and better. Below are more details on such equipment:
Bar bending machines
Mostly, cutting and bending of reinforcement bars has been a manual affair at all construction sites. A temporary arrangement is made at the site by the blacksmiths, by fixing wooden sleepers over vertical posts and fixing anchors over them. Bars are cut and cranked to shape, and the job is quite tedious and time- consuming. Development of bar-cutting and bending machines has resulted in making this job much easier. Different models of these machines have been developed by the manufacturers for different ranges of diameters of steel bars. Cutting machines are normally capable of cutting plain bars up to 42 mm diameter and (Thermo Mechanically Treated (TMT) bars up to 36 mm diameter. Bar-bending machines are designed for diameters up to 16 mm, 36 mm and 42 mm in case of plain bars, and 12 mm, 32 mm and 36 mm in the case of TMT bars.
Esquire, Spartan, Sana, Walia, Jayem, Bellstone and Cosmos are some Indian companies manufacturing and selling these simple but useful machines. Icaro machines from Italy can cut and bend steel bars up to 70 mm diameter and are being marketed in India by Ispat Sales, Mumbai. Icaro is also producing a combined machine that can do the cutting as well as bending of steel bars. Equipped with 3-5 HP three phase motors, these machines are hydraulically operated with easily replaceable blades in cutting machines and multiple dies in bending machines. Icaro machines can be fitted with a computerised automatic angle selector which can select five bending programs and bend the bars accordingly. The Sana bar-bending machine bends the bars of 8-32 mm diameter and has an output six times that of the manual output. Its low operating height and multi-edge cutting blades ease the work to a large extent. Sana bar-cutting machines are self propelled and light weight with a good output.
Stirrup bending machines
More difficult than cutting and bending of re-bars is the bending of steel stirrups. Spartan has devised a machine for the bending of steel stirrups. The machine can bend to shape steel bars up to 12 mm diameter. Normally, stirrups of 8 mm, 10 mm or 12 mm diameter are only used. The higher diameter stirrups are required only for heavy beams or structures. A stirrup bending machine can produce 900 stirrups in 10 hours if a single steel coil is used and 1,800 stirrups if a double coil is used. Weight-wise, six to eight tonnes of steel can be converted to stirrups in a 10 hour shift. These electrically operated machines make the reinforcement work in buildings quite fatigue free. Icaro stirrup bending machines produces multiple shapes of stirrups including square, rectangular, trapezoidal, L-shaped or polygonal ones. The minimum size of the stirrup has to be 80 mm, the maximum side size can be as large as 1,500 mm. These machines also allow simultaneous bending of many coils if the diameter of bar is small. Two bars of 12 mm diameter can be bent together and the number of bars goes up to seven if the diameter of the bar is 6 mm. As the awareness of these machines grows amongst builders, equipment manufacturers are encashing on the popularity of stirrup- bending machines and producing them locally.
Application of cement mortar on the inner and outer faces of walls in buildings is essential to provide a smooth and proper base to the painting and finishing work. When the walls are in brick or cement blocks, this plastering of walls is vital. Plastering work can be avoided in concrete walls as good formwork can itself result in smooth surfaces of walls. However, in practice, joints of forms allow the concrete mortar to seep through and the surface needs to be treated with plaster, possibly of lesser thickness. For one-brick-thick walls with a nine inch thickness, only one face can be kept smooth and the other face of the wall will require thicker plaster to be done in two coats. The most common practice is to use 12 mm thick plaster on a smooth surface and 20 mm thick plaster on a rough face. Plaster with a thickness more than 12 mm is always recommended to be done in two coats as otherwise it comes off after some time. The first coat is of 12 mm and is applied by throwing mortar from a distance, keeping its surface rough to allow for the next coat. The second coat is of 6-8 mm thickness and finished with a trowel. All this work requires a lot of skill, labour and time. A piece of equipment invented to make building work easier is the mortar sprayer. It helps in avoiding manual work, achieving faster progress of work and is a major labour-saving equipment.
Features of mortar sprayers
Mortar sprayers spray the mortar on the surfaces to be plastered under pressure through spray guns attached to the pumps operated by diesel or electrical engines. In all cases, the sprayers are attached to air compressors which help in the delivery of mortar. Air pressure has to be adjusted at site as per requirement, depending upon the diameter and length of the hose pipe. From the back of the spray guns, an air line goes to the compressor.
Mixer for mortar sprayer
Mortar sprayers can be fed by site mixers or can have inbuilt mixers. Turbosol Produzione, Italy, produces mortar sprayers with inbuilt mixers which are specially suitable for heavy-duty purposes. The guns can deliver mortar up to a height of 60 m which is quite a significant height. Built and supported over pneumatic wheels, the equipment can be stationed at suitable locations. An automatic safety device auto-cuts the sprayer when extra pressure gets created. Rubber hoses and air hoses of required length, spray guns and nozzles form part of the equipment. Single or three phase motors can be added to Turbosol sprayers and the piston can pump out mortar at a rate of a 1,400 litres per hour. These sprayers are likely to see an increased use once the cost of equipment, which is now hovering at around Rs 25 lakh, comes down. Aquarius Technologies is now marketing Turbosol mortar sprayers in India.
In addition to spray gun sprayers, there are hopper sprayers that have different types of hopper attachments as per requirements. Wall hopper sprayers and ceiling hopper sprayers are designed to suit vertical and overhead sprays respectively by changing the position of air jets and delivery holes. The hoppers can be filled with mortar by a worker manually or the hopper can be dipped in a wheel barrow filled with cement mortar. A hopper can contain about 4-5 litres of mortar. Delivery holes are provided at the base of the hoppers. Tirolessa mortar hopper sprayers attached to a 5 HP or more, capacity air compressors are quite cost-competitive and popular in countries like the US. Whenever hopper sprayers are used, it is advisable to lubricate the hopper well before filling the mortar in it. The hopper should be cleaned with water from time to time to avoid deposit of cement on its walls or closure of holes through which the mortar travels. Cleaning tools provided with the sprayers as accessories should be frequently used.
In most buildings, the walls are first erected in bricks or concrete, and the work of laying water supply lines begins thereafter. To do this, a chisel and hammer are used to cut a chase in the walls. Generally, this results in uneven cutting of walls. Sometimes, a harder stroke drives a brick out and a permanent source of dampness gets created in the wall. All efforts to plug the hole thus created go waste. In addition, the vertical lines of the chase cut in the walls are totally uneven. After the laying of pipes, when the repair is applied, it can always be noticed later on, even after providing any number of paint coats. As a result, the wall looks ugly and it spoils the beauty of the room.
One can reconcile to this if the problem is limited to one room. Today, the design of houses is such that the water supply lines are running all over the house. We wish to provide wash bowls in the lobby and dining room, we attach a bathroom or toilet to each bedroom and we want the kitchen to be big and well-equipped. We also look for water supply points in the balconies and on the terrace. A terrace swimming pool or terrace garden is fast becoming a common feature. Needless to say that availability of water is required in all corners of the house. Under such circumstances, lines are to be laid all over, to be hidden well in the walls and are desired to function properly.
Chase cutting machines do exceptionally neat, clean and fast work. Electrically run, these machines can work on the brick walls, concrete as well as cement blocks. Whereas a worker may take two hours to cut a chase in a wall 10 feet high, these machines can cut a chase that is 10 ft in height in just two minutes! The size of the chase cut in the wall is exactly as per requirement and perfectly rectangular in shape. The machine weighs around eight kg and can be handled easily. It has the ability to accommodate different cutters to do chase cutting of different sizes. To cut out a big size chase, two small chase cuttings can be done in close proximity to each other and then the central material can be struck off.
In general, water supply pipes laid inside the houses are of 15-20 mm in diameter. In large multi-storeyed buildings, 25 mm diameter pipes also are used. To accommodate these pipes, grooves of 25x25 mm, 30x30 mm and 35x35 mm are sufficient. Milling cutters to provide these sizes of cuts can be used on the same machine. The manufacturers sometimes make modifications in cutters as per the requirements of the user.
Chase cutting machines use single phase electric motors of about 2.5 HP. Mostly made of cast aluminium, these are sturdy, weigh around eight kg and have a good life. Cutters run at about 1,000 rpm and the power consumption is about two units per hour. As the cutting speed of the machines is fast, overall power consumption is negligible. Another main advantage of the machines is that they take out the bricks and concrete in small fragments, which helps avoid raising too much dust all around.
To make the best use of cutters, they need to be sharpened after every 30 hours of use. One milling cutter can cut a chase over 15,000-20,000 m length before its replacement. This is a fairly good output for a single cutter. However, to achieve this, the cutters need to be used after their full sharpening. A cutter costs around Rs 2,500-3500, depending upon the size of the chase to be cut. Thus, the cost of cutter per metre of chase-cutting works out to be in the fraction of a rupee!
Chase cutting machines can cut a chase for embedding water supply lines, electrical conduits, cables or any other similar pipes or conduits in the walls. Obviously, their speed of functioning is highest in a hollow block wall followed by brick walls, solid cement block walls and concrete walls. Dust produced by the chase-cutting machines is much lesser than that produced by diamond disc cutters. In comparison to conventional methods, there is a saving of 70 per cent labour. Unlike manual chase cutting, no physical fatigue is caused. The machine can be run vertically, horizontally, along a circle or in any direction. While running, it can be left on the vertical wall and will not fall down. Only, during its running, the operator needs to push it along the direction of the chase.
Chase-cutting machines are available in Spain and are being imported to India by certain representatives. Priced at around Rs 50,000, these are fast coming under use by builders and real estate developers. The price is likely to come down in the near future as the machine is simple in production but great to use.