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There are a number of tools used in concrete and masonry projects. Concrete tools include screeds, floats, trowels, edgers, and groovers. Masonry tools include trowels, jointers, chisels, and line blocks. When you consider which of these tools to use, keep in mind the specific purpose of each one. In this chapter, you will learn about different types of concrete and masonry tools and their uses. You will also learn how to select the right concrete and masonry tool for the job, use various types of concrete and masonry tools, and provide the proper care of the concrete and masonry tools to keep them in good working condition.
When you have completed this lesson, you will be able to do the following:
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The concrete vibrator is used to consolidate concrete after it has been poured. Concrete vibration is important in removing air pockets in the mix. It is performed before the surface is finished.
The wood screed board is used to cut off excess wet concrete to bring the top surface of a slab to the proper grade.
The wood screed board is a straight 2- by 4-inch board about a foot longer than the width of the area being worked on. The concrete should be screeded as soon as it has been poured and vibrated. The screed board should rest on the concrete form and a sawing motion used while the screed board is pulled toward the end of the poured area. Fresh concrete should be poured into lower areas and the screeding process repeated.
The power screed is used to cut off excess concrete from the top surface of a concrete slab. It is useful for screeding large concrete slabs that would be difficult to screed using a wood screed board.
A bull float smoothes the surface of freshly laid concrete by applying pressure to the concrete�s surface. This pressure levels ridges and fills voids left by the screeding process by pushing the aggregate down and allowing the liquid to rise and dry, leaving behind a smooth surface. The bull float is used to float large areas of concrete. A bull float is generally 42 or 48 inches long and 8 inches wide. It has handle sections that come in 5- or 6- foot lengths that can be joined together so they will reach 15 to 20 feet over a slab.
The darby float is used to level concrete on smaller areas, with a surface that is generally less wavy than that created with a bull float. It is usually made of magnesium or aluminum.
The magnesium float is another option for smoothing smaller areas. It ranges in length from 12 to 16 inches, with widths from 3 1/8 to 3 1/2 inches.
A trowel produces a hard, smooth, dense surface on concrete and is used immediately after floating. The steel trowel is used to increase the wear resistance of the concrete. Troweling multiple times allows the worker to apply increasingly greater pressure to make the concrete denser. Each successive troweling should be done with a smaller trowel tipped at a greater angle than the last troweling.
A finish trowel, also known as a pool trowel, is similar to the steel trowel, except the ends are rounded to prevent digging into the concrete during the finish troweling.
The concrete whirlybird is a walk-behind power trowel. It is useful for troweling large concrete surfaces.
The edger is used to round the edge of the slab after the bleed water disappears from the concrete surface. Edging is done mostly on patios, curbs, sidewalks, and driveways to give a tight, clean-looking edge that resists chipping.
The groover is used to cut joints in concrete to control the location of cracks that might form as the slab contracts. The groove sizes range from 1/4 to 1/2 inch wide and are usually 1/2 inch deep.
The concrete saw is used much like the groover; to cut joints in concrete to control the location of cracks. It is used for large concrete projects.
The following steps describe how to use concrete tools to finish concrete properly:
Figure 1 � Screeding operation
Figure 2 � Hand float in use.
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| Note Avoid overworking the concrete during finishing operations. Hairline cracks are created by a concentration of water and extremely fine aggregates at the surface. |
Use the following guidelines when working with concrete tools:
The pointing trowel is used by bricklayers for pointing up their work, as well as for patch work and for cleaning other tools. The length of pointing trowels ranges from 4 1/2 to 7 inches.
The mortar trowel is similar to the steel trowel used in concrete work. The mortar trowel is used for spreading mortar on a surface before laying brick or block.
The convex jointer is used to strike joints in brick and block walls, giving the joints a neat, finished appearance. Each end of the jointer is a different size, with popular sizes of 1/2, 5/8, 3/4, and 7/8 inches.
The V-jointer is similar to the convex jointer. It has one turned up end for easy use.
The slicker is another type of jointer for finishing mortar. It has a ridge that leaves an even depression in the mortar.
The rake out jointer is used to remove old mortar when repointing masonry. It is offset to throw mortar out as the joint is raked. The tab at the end helps rake the corners.
The line block is used to hold a mason�s line to keep masonry construction level.
The following paragraphs describe how to use a pointing trowel properly.
The secret of mortar joint construction and pointing is in how the trowel is held for spreading mortar. Figure 5 shows the correct way to hold a trowel. It should be held firmly in the grip shown, with the thumb resting on the top of the handle, not encircling it.
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Right-handed users should pick up mortar from the outside of the mortar board pile with the left edge of the trowel as shown in Figure 6. A pickup for one brick forms only a small pile along the left edge of the trowel. Enough can be picked up to spread one to five bricks, depending on the wall space and user�s skill. A pickup for five bricks is a full load for a large trowel, as shown in Figure 7.
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Right-handed users work from left to right along the wall. Holding the left edge of the trowel directly over the center line of the previous course, the trowel should be slightly tilted and moved to the right as shown in Figure 8. An equal amount of mortar should be spread on each brick until either the course is completed or the trowel is empty. Any mortar left over should be returned to the mortar board.
The mortar for a bed joint should not be spread too far ahead of laying; four or five brick lengths is best. Mortar spread out too far ahead dries out before the bricks become bedded and causes a poor bond, as shown in Figure 9.
Figure 9 � A poorly bonded brick.
The mortar must be soft and plastic so that the brick will bed in it easily. The mortar should be spread about 1-inch thick and then a shallow furrow made in it as shown in Figure 10. A furrow that is too deep leaves a gap between the mortar and the bedded brick. This reduces the resistance of the wall to water penetration. A smooth, even stroke should be used to cut off any mortar projecting beyond the wall line with the edge of the trowel as shown in Figure 11. Enough mortar should be retained on the trowel to butter the left end of the first brick to be laid in the fresh mortar. The rest back should be thrown on the mortar board.
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The first brick to be laid should be picked up with the thumb on one side of the brick and the fingers on the other, as shown in Figure 12. As much mortar as will stick to the end of the brick should be applied and then pushed into place.
The excess mortar at the head joint and at the sides should be squeezed out as shown in Figure 13. It is important to be sure the mortar completely fills the head joint. After bedding the brick, the excess mortar should be cut off and used to start the next end joint. Any surplus mortar should be thrown back on the mortar board where it can be restored to workability.
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Use the following guidelines when working with masonry tools:
1. What concrete tool consolidates concrete after is has been poured?
2. What concrete tool cuts off excess wet concrete to bring the top surface to the proper grade?
3. The bull float performs what action to freshly laid concrete by applying pressure to the concrete�s surface?
4. What concrete tool produces a hard, smooth, and dense surface on the concrete?
5. The concrete whirlybird is used to trowel what type of concrete surfaces?
6. The groover is used to create what effect in concrete to control the location of cracks that might form as the slab contracts?
7. When working with concrete tools, the operator should wear a hard hat, eye protection, gloves, and which of the following personal protective equipment?
8. To avoid concrete build-up, at which of the following intervals should you clean concrete tools?
9. What masonry tool can be used to clean other tools?
10.What masonry tool spreads mortar on the surface before laying brick or block?
11.The convex jointer is used to strike joints in brick and block walls giving the joints what type of appearance?
12.What masonry tool is a jointer for finishing mortar?
13.The rake out jointer is used to remove what type of mortar when repointing masonry?
14.What masonry tool aids in keeping the masonry construction level?
15. In what condition should the edges of masonry tools be kept?
16.To avoid mortar build-up, at which of the following intervals should you clean masonry tools?
Copyright � David L.
Heiserman
All Rights Reserved
