- - AGRICULTURE CORE CURRICULUM - - (CLF2000) Advanced Core Cluster: AGRICULTURE MECHANICS (CLF2500) Unit Title: CONCRETE/MASONRY ___________________________________________________________________________ (CLF2506) Topic: LAYING MASONRY UNITS Time Year(s) 2 Hours 1/2/3/4 __________________________________________________________________________ Topic Objectives: Upon completion of this lesson, the student will be able to: Learning Outcome #: (K-6) - Describe and use basic masonry techniques and tools. Special Materials and Equipment: Brick trowel, wheelbarrow, water hose, shovels, level, builder's line, jointer, mortar board, mortar ingredients, portable mixer: also possibly rebars, anchor bolts, sill lumber, and assorted examples of masonry References: Burke, Stanley R., & Wakeman, T. J. (1990). MODERN AGRICULTURAL MECHANICS (2nd ed.). Danville, IL: Interstate Publishers. Cooper, Elmer L. (1987). AGRICULTURAL MECHANICS: FUNDAMENTALS AND APPLICATIONS. Albany, NY: Delmar Publishers. Phipps, Lloyd J., & Reynolds, Carl L. (1990). MECHANICS IN AGRICULTURE (4th ed.). Danville, IL: Interstate Publishers. Editors of Reader's Digest. (1973). COMPLETE DO-IT- YOURSELF MANUAL (7th ed.). Pleasantville, NY: Reader's Digest Association. U.S. Dept. of the Army. CONCRETE, MASONRY, AND BRICKWORK: A PRACTICAL HANDBOOK FOR THE HOMEOWNER AND SMALL BUILDER. New York: Dover Publications. Resources: Midwest Plan Service. (1980). STRUCTURES AND ENVIRONMENT HANDBOOK. (10th ed.). Available from: Midewest Plan Service, 122 Davidson Hall, Iowa State University, Ames, Iowa 50011 Evaluation: Teacher observation of student work and quiz by instructor. TOPIC PRESENTATION: Laying Masonry Units A. Masonry is anything constructed of stone, brick, tile, or concrete blocks, usually with the use of mortar or cement as a bonding agent. 1. Terminology a. Masonry Units - Brick, stone, tile, or concrete block which are laid in courses with mortar joints. b. Brick - Solid, rectangular-shaped units which are created by kiln- baking various clay and shale mixtures; they can vary in colors and hardnesses but are of uniform size. In the U.S., bricks measure 2 1/4" by 3 3/4" by 8." c. Tile - Hollow rectangular units made from burning clay and shale. The shape is created by forcing the pliable clay mixture through a molding die. The widths and thickness differ depending on the style of tile; however, the length is always a standard 12." d. Stone - There are six kinds of natural stone construction: granite, marble, slate, limestone, sandstone, and bluestone. Stone can be purchased in three finishes: dressed, semi-dressed, and undressed. The shapes and dimensions vary according to the stone and finish used. e. Concrete Block - Ready-made, pre-cast units made from portland cement and fine aggregates such as sand, pebbles, crushed rock, or cinders. The concrete mixture is then forced into a mold of the desired shape. f. Mortar - A mixture consisting of portland cement, hydrated lime, sand, and water. This is what holds the units together g. Laying Block - The process of mixing mortar, applying it to block, and placing the block to create walls. h. Courses - the layers of the masonry units i. Mortar Bed - A layer of mortar on which the masonry units are laid. 2. Tools a. Brick Trowel - used by the mason in laying units and when working with mortar. It is pointed and measures 4 3/4" by 11." b. Mortar Board - wooden board used to hold mortar near the work site. c. Jointing Tool - used to tool mortar joints; compresses mortar, and makes joint watertight. It comes in different shapes. d. Carpenter's Level - a device used to ensure that courses are plumb and level e. Builder's Line - used to ensure that courses are straight f. Mason's Hammer - a specialized hammer used to cut masonry units to desired sizes g. Star Drill - a specialized hand drill used to drive holes in masonry and concrete. The drill point is temper hardened and looks somewhat like a four-point star; the shank is made of high- grade carbon steel. It is operated by striking with a hammer. h. Carbide-Tipped Masonry Drill - a specialized power drill used for drilling holes in masonry and concrete. The tip is treated with tungsten-carbide to resist heat and wear. NOTE: All of the following information refers only to the installation of concrete blocks; however, the installation of brick, tile, and stone is very similar. B. Types of Blocks 1. Standard Dimensions: a. Length - 15 5/8 inches b. Height - 7 5/8 inches or 3 5/8 inches c. Width - 7 7/8, 3 5/8, 5 5/8, 9 5/8, or 11 5/8 inches d. When laid with a 3/8-inch mortar joint, the block's overall dimensions are 8" by 8" by 16" (7 5/8 X 7 5/8 X 15 5/8). 2. Block Style a. Hollow or Solid - Hollow spaces are called cores; a solid unit has a core area of 25% or less of the total cross-sectional area. b. Heavyweight or Lightweight - Heavyweight units weigh approximately 40-50 lbs. while the lightweight units weigh approximately 25-35 lbs. The difference in weight is due to the different types of aggregates used in manufacture. 3. Block Shapes a. Stretcher - This is the most commonly used block for straight wall runs; it has slight extensions called ears on each end which form a core when laid end to end. (2 or 3 core) b. Corner - same as a stretcher except that one end is smooth; it is used at the end or corner of a wall. c. Half Block - both ends are smooth; it is used for openings and ends of walls. d. Sash or Jamb - have special grooves for the installation of windows or doors. e. Miscellaneous - solid top, partition, bull nose, half-height, lintel; each has a special application. C. Job Estimation 1. How many blocks? a. To estimate the number of blocks (8 X 8 X 16) needed for a wall, use this formula: 1) Height of Wall X 1 1/2 = Number of Courses (A) a) One foot (12 inches) is 12/8 or 3/2 or 1 1/2 of the height of a block. b) The height can then be multiplied by 1 1/2 to determine the number of courses needed. 2) Length of Wall X 3/4 = Number of Blocks per Course (B) a) One foot is 3/4 the length of one block. b) Therefore, the length of the wall in feet can be multiplied by 3/4 which gives the number of blocks needed for one row. 3) A X B = Total Number of Blocks b. When planning a project, it is important that the dimensions between corners and all openings utilize full- or half-length block; this will save time and money and improve the overall appearance of the project. 2. How much mortar? a. Purchase approximately 2 1/2 bags of masonry cement and 667 lbs. of mortar sand for each 100 blocks. ____________________________________________________________ ACTIVITY: 1. Have students complete homework assignment which entails writing down all the uses of masonry construction around their home. 2. Take students on a short field trip around the school and have them identify the masonry construction used. 3. Plan out a site where some masonry construction is needed around the department or school. ____________________________________________________________ D. Footing Construction 1. Footing or Footer a. This is a continuous slab of concrete which provides a solid, level foundation for block or brick. 1) It should be at least as deep as the wall is wide (i.e., 8" wide wall should rest on a footer that is at least 8" deep). 2) The footer width should be at least twice that of the wall (i.e., an 8" wall should rest on a footer 16" wide). 3) Where temperatures drop below 32 degrees F., footers should be placed below the frost line to prevent damage. a) The frost line is the maximum depth that the soil freezes. b. A trench is dug by backhoe or shovel with the width and depth corresponding to the footing size. c. Concrete is poured into the trench and leveled to the desired height of the footing. d. Use a regular 5:1 concrete mix for the footing. e. Make sure to install a horizontal reinforcement bar to strengthen the footing from the weight created by the block wall. f. Vertical reinforcement should be used if the wall is to be higher than three feet. It should be placed so it will pass through one core of every two to three blocks; this, however, depends on wall length. E. Mortar Preparation 1. Ingredients a. Masonry cement (mortar mix) 1) When purchased, the correct proportions of lime have already been added to portland cement. 2) Sacks come in 1 cubic foot amount with the correct amount of sand to be added printed on the sack. b. Mortar Sand 1) This is special-sized sand for the specific purpose of use in mortar mix. 2) Regular sand can be used but it must be screened to remove the larger particles. 3) For general work, about three parts of sand are added to one part of mortar mix. c. Water - Add just enough water to make the mix workable i.e., pliable enough to support the units on a 3/8" mortar joint until it has set. 1) If mortar is too stiff (not enough water) it will not bond tightly to the block. 2) If it is too thin, it will be squeezed out of the joint by the weight of the block. If this happens, the joint will be less than 3/8." 2. Mixing a. Small Batches 1) Mix the mortar in a mortar pan, wheelbarrow, or a leakproof pan. 2) Stir or mix with a mortar hoe or regular garden hoe. 3) Mix dry materials to a uniform color before adding water. 4) After adding water, mix mortar thoroughly until it is pliable and workable. b. Large Batches-(more than two wheelbarrows full) 1) Use a motor or engine-driven mixer to ensure more thorough and efficient mixing. 2) Some of the water should be added first, then the dry materials, and, finally, the amount of water needed to obtain the right consistency. F. Laying Block 1. Methods a. Use a corner pole to ensure that the block are laid straight and plumb at each end of the wall. 1) A corner pole is a straight piece of wood or metal held plumb by diagonal supports. a) It is used to support the builder's line to which the wall is built. b) The pole also has lines marked on it which represent the correct height of each course. b. A carpenter's level can also be used as a guide to lay block corners. 1) The level can be used to both level and plumb the block. 2) The corners are built first and then the areas between them are filled with courses of stretcher block. A line is used to keep the courses straight. NOTE: The following procedure uses the corner pole method where the builder's line is repositioned after each course is laid. The height of each course is constantly checked to be a full 8 inches by using the marks on the corner poles.) 2. Procedures a. Start from a corner with a corner-shaped block. b. Spread a full layer of mortar (mortar bed) on the footing. 1) The webs of the block as well as the face shells or outer edges are bedded in mortar. 2) Place about 1/2" of mortar on the footing so when the block is pushed into it firmly the bed measures 3/8 of an inch. c. Lay the first corner block carefully. 1) Position it so the outside corner is exactly where the outside corner of the wall should be. 2) Place it so the thinner part of the web is down. 3) Level the block, first crosswise and then lengthwise. 4) Use the trowel handle to tap the block into position and level it. d. Lay the second (stretcher) block. 1) Stand a block on end and butter (apply mortar to) the two projecting ends (ears) with a downward wiping or swiping stroke with the trowel. 2) Put the block firmly in place and level it. e. Lay several stretcher block by working away from the end or corner. 1) Check the first course for: a) Levelness crosswise and lengthwise b) Outside edges for plumb c) That the block forms an even straight line. 2) Use the end of the trowel handle until each block is plumb, level, and the course is straight. f. In preparation for the second course, apply a mortar bed to the top of the first course. 1) Above the first course, it is necessary to apply mortar only to the face shells or outer edges. 2) Some local codes require full bedding for all courses so check local codes before starting a job. g. If extra strength is needed, install reinforcement wire in the mortar bed. h. Trim off excess mortar with the edge of the trowel as the block laying progresses. i. To reposition the builder's line after each course is laid the line is positioned to be level along the top of the block. j. Check the height to be sure each course is an additional 8 inches high. k. If a block must be cut to a certain size: 1) Use a mason's hammer and make multiple strikes along the line to be cut. 2) Then make one sharp rap on the edge of the web. 3) Try to keep cutting of blocks to a minimum since it hurts the appearance of the project and drastically increases the labor required to finish a job. l. As work progresses and the mortar begins to dry and stiffen, the joints can be tooled. 1) Joints should be compacted and finished. a) This produces a tight, water-resistant joint. b) It also emphasizes the joint lines and gives the job a neat appearance. 2) Tools are available to create a variety of joints such as concave, V-shaped, or raked. a) A flush joint can be obtained by rubbing it with a broken piece of block. If the wall is to be plastered or stuccoed, leave the joint flush. m. Pouring the grout for reinforcement 1) All block cores holding vertical steel reinforcement rods must be filled solid with grout. a) Grout mix contains 5 parts sand to 1 part cement; it is mixed very wet. b) If desired, gravel can also be used. 2) A tamping rod should be used to ensure that the grout goes down to the footing. 3) A solid, reinforced concrete pier will be formed in the wall. n. For a wall supporting a roof frame where wooden plates need to be fastened: 1) Embed 1/2-inch anchor bolts 18 inches long in grout in the cores of the top two courses. 2) Space the bolts no more than 4 feet apart. 3) Metal lath (wire mesh) is placed two courses down to support the bolts. o. The final step in building with block is the finishing of the top. 1) The top of the wall may be finished with any of the following methods: a) A solid masonry course using solid-top block or solid 2-inch-thick cap block. This course must be laid with as much care as the first course. b) A course of decorative, design blocks. c) A crown of regular mortar mix round and trowel smooth supported by metal lath in the course below. d) A flush top of block with cores filled with mortar mix supported by metal lath in the course below. ____________________________________________________________ ACTIVITY: 1. Have students complete the project planned in the beginning of this lesson. (If you are not an expert mason do not worry, contact a local concrete or mason contractor for some advice. Don't be surprised if they are willing to come out and donate their time.) 2. Take students to a job site where masonry construction is being done. ____________________________________________________________ SAFETY IN MASONRY WORK* Observe the following general safety practices in doing all masonry work. 1. Wear proper safety equipment. When doing masonry work, wear safety glasses, safety shoes, and a hard hat. 2. Wear gloves. Masonry units and concrete are abrasive. Wear gloves to protect your hands when you handle these products. 3. Wear a respirator. When working in masonry dust, wear a filter- type respirator. 4. Check equipment before you use it. Be sure that hoists, scaffolds, and ladders are properly assembled and secured before you use them. 5. Stack masonry materials carefully. Masonry materials such as concrete blocks and dry cement are bulky and heavy; if improperly stacked, they can easily fall, causing injury. 6. Operate concrete and mortar mixers cautiously. Be certain all guards are in place and if a mixer is electric, that it is properly grounded. 7. Use chemicals with extreme care. Many chemicals needed for masonry work, such as muriatic acid and trisodium phosphate, are harmful to the skin and clothing and must be used carefully. When using masonry chemicals, wear rubber gloves to avoid damaging your skin. 8. Check all concrete forms. Poorly constructed forms endanger lives. Check them for strength and safety before you use them. 9. Place tools in a convenient location. Place tools for working convenience but never where you or others would be endangered. _____________________ * Reprinted by permission of Interstate Publishers, Inc., from MODERN AGRICULTURAL MECHANICS, 2nd ed., by Stanley R. Burke and T. J. Wakeman. Copyright 1992 by Interstate Publishers, Inc. 7/23/91 JPD/sg #%&C