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Materials for Civil and Construction Engineers

CHAPTER 8Masonry

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One of the oldest & most durable construction materials:Pyramids of EgyptGreat Wall of ChinaGreek & Roman ruinsNorth American Adobe ruins

Introduction

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Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Third Edition. Copyright 2011 Pearson Education, Inc.

CMU = concrete masonry units solid or hollowClay bricks solidStructural clay tiles hollowGlass blocks solidStone solid

8.1 Types of Masonry Units

CMU Clay Bricks Structural Clay Tiles

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Concrete Masonry units Clay bricks Structural clay tiles

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Glass blocks Stone

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Solidconcrete bricksnet cross sectional area >75% of gross area

Hollowconcrete blocks, hollow blocks, cinder blocksnet cross sectional area

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Water Absorption

Absorption % Ws WdWd 100 Absorption kg/m3 Ws WdWs Wi 1000

Moisture content as a percent of total absorptionWr Wd

Ws Wd100

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Concrete building bricks (ASTM C55)manufactured for general use in non-facing, utilitarian applications

Concrete facing bricks (ASTM C1634)used where faces are intended to be exposedhave stricter requirements maximum allowable water absorption is less minimum net area compressive strength is higher

Exposure Properties

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Nominal dimensions include half of mortar jointSpecified or modular dimensions are design sizes of unitActual size includes some slight shrinkage from firing

Nominal and Specified Dimensions

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Strength Requirements of Concrete Bricks

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Clay BricksSmaller, solid, rectangular blocks made of fired clayUsed for different purposes:

Building Facing and aestheticsFloor making Paving

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1. Clays are composed mainly of silica (grains of sand), alumina, lime, iron, manganese, sulfur, and phosphates, with different proportions.

2. Bricks are manufactured by grinding or crushing the clay in mills and mixing it with water to make it plastic. The plastic clay is then molded, textured, dried, and finally fired.

3. Bricks are manufactured in different colors, depending on the firing temperature of the clay during manufacturing.

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Clay bricks Properties

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Absorption determines the durability of bricksHighly absorptive bricks can cause efflorescence and other problems in the masonry

Absorption by 24-hour submersion % Ws24 Wd Wd 100 (8.5)

Absorption by 5-hour boiling %

Wb5 Wd

Wd 100 (8.6)

Saturation coefficient Ws24 Wd

Wb5 Wd (8.7)

Absorption of Clay Bricks

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mixture of cementitious material, aggregate, and waterMortar can be classified as cement-lime mortar, cement mortar, or masonry cement mortar

Used for the following functions:bonding masonry units together, either non-reinforced or reinforcedserving as a seating material for the unitsleveling and seating the unitsproviding aesthetic quality of the structure

8.2 Mortar

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High-slump concrete consisting of PC, sand, fine gravel, water, and sometimes lime

Used to fill the cores or voids in hollow masonry units for the purpose of:1. bonding the masonry units2. bonding the reinforcing steel to the masonry3. increasing the bearing area4. increasing fire resistance5. Improving overturning resistance by increasing weight

The minimum compressive strength of grout is 14 MPa(2000 psi) at 28 days

8.3 Grout

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fluid mixture of PC, lime, sand, and waterUsed for finishing either masonry walls or framed (wood) walls

Used for either exterior or interior wallsStucco is plaster used to cover exterior wallsAverage compressive strength of plaster is about 13.8 MPa (2000 psi) at 28 days

8.4 Plaster

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Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Third Edition. Copyright 2011 Pearson Education, Inc.

Masonry is one of the oldest building technologies.Modern masonry units are produced to high standards inthe manufacturing process. While the strength of themasonry units is important for quality control, the strengthof masonry construction is generally limited by the abilityto bond the units together with mortar.

The ability of masonry units to resist environmentaldegradation is an important quality consideration. Thisability is closely related to the absorption of the masonryunits.

Summary

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