CM 313: Masonry Ch. 8-10

Stone Masonry Patterns

laid in mortar - rubble (unsquare pieces) - ashlar (square pieces) - coursed or random - orientation

Mortar Cement

• A proprietary premixed product, like masonry cement • produced to a standard that assures higher bond strength comparable to cement-lime mortar

Spanning Systems for Masonry Bearing Wall or Veneer Construction

Arch, Steel Lintel (over door or window openings, combined with flashings) Mill Construction • Heavy timber interior structure, with noncombustible masonry exterior walls • Mill construction is considered more fire-resistant than ordinary construction because the heavy timbers are slower burning than the thinner framing members of ordinary construction. Steel and Concrete Decks with Masonry Bearing Walls • Open-web steel joists, corrugated steel decking, and concrete floor slabs with masonry bearing walls • OWSJs are well suited to masonry loadbearing construction because of their relatively close spacing which imposes a more uniform load on the masonry wall. • With structural steel framing at greater spacings, extra reinforcing or enlarged masonry piers may be required to carry the greater concentrated loads at bearing points. • Precast concrete hollow core slabs with cast-in-place concrete topping • The wall in this example is single-wythe, fully grouted, reinforced CMU bearing wall.

Reinforcing & Anchorage

Joint Reinforcing: ladder, truss

Milling operations

bandsawing, circular sawing, hand carving, planing

Quarrying (limestone)

• A long-bladed diamond saw, traveling on rails, makes deep, long cuts into the solid rock. • Closely-spaced horizontal holes are drilled into the vertical face of the rock to create a plane of weakness near the bottom of the saw cuts. • Rubber bladders are inserted into the saw kerfs and inflated, causing the large slabs to fall away from the solid rock.

Flashing Locations

• A through-wall (internal) flashing installed underneath the top-of-wall coping units intercepts water that passes between joints of those units. (red) • An external flashing, in this case a counterflashing, is installed on the back of the parapet to prevent water from passing behind and under the roof membrane termination. (green) • Through-wall flashings should be installed at all interruptions in the cavity. • A flashing above a wall opening intercepts water in the cavity and prevents it from spilling into the opening. • A flashing below a wall opening intercepts water that enters around the opening and keeps it out of the wall.

Spanning Openings

• Lintels (steel angle, stone, precast concrete, reinforced) • Arches • Corbelling

Slate Group

• Metamorphic rock • Derived from shales (mineral clays) • Dense, hard, nonabsorbent • Closely spaced planes of cleavage • Variety of colors

Mortar

• Provides Bearing uniform joints • Seals joints minimizing the flow of air and water • Adheres units resistance to lateral forces from wind & earthquakes

Concrete Masonry Reinforcing

• Reinforcing increases compressive strength, resistance to cracking, and resist to lateral forces. • Horizontal joint reinforcing and vertical steel reinforcing bars • Joint reinforcing is made from wires that are small enough in diameter to fit within the mortar joint.

Other Groups

• Travertine: - Partially-crystallized, patterned calcite - Chemically similar to limestone - Similar to marble in its physical properties • Alabaster • Greenstone • Schist • Serpentine • Soapstone

Types of Stone

- fieldstone - rubble stone - dimension stone

Hollow Concrete Block

- most ommon CMU - sizes - placement cost - reinforcing - uses and finishes - moisture penetration

Portland Cement-Lime Mortar

- portland cement - lime - water

Blended hydraulic cement

- portland cement mixed with other cementitious materials - replaces cement in cement-lime mortar mix

Brick Grade

Defines durability • Grade NW: Interior brick, concealed building brick, and other brick not exposed to the weather • Grade MW: Above grade brick only, in regions of negligible weathering • Grade SW: Any weathering region, above or below grade

Brick Forming

Extruded or Stiff Mud Process • Moderately moist clay is extruded through dies and then sliced into individual units. • Generally least expensive molding method • Accounts for approximately 90% of US made bricks • The extrusion process naturally produces brick units with a smooth face and high dimensional uniformity. • Various post-extrusion distressing steps can be used to create bricks with greater variation in shape and surface texture

Cold and Hot Weather Construction

Mortar must not freeze while it is curing: • Keep materials dry. • Preheat materials. • Protect construction from weather and wind. • Use cement types that cure rapidly & generate more heat while curing. • Provide temporary space heating. In especially hot weather, mortar should be protected from water loss: • Keep mortar in shade to prevent rapid water evaporation. • Pre-wet masonry units to prevent excessive water absorption.

Membrane Flashings

Self-adhering bituminous membranes - Polymer-modified bitumens laminated to plastic backings - Self-sticking to substrate - Less expensive and easier to install than metal flashings - Have some capacity to self-seal around penetrations - Cannot span cavities or other significant gaps without backup metal support • EPDM - Synthetic rubber - Long-lasting - Easy to install • Other plastics - May be vulnerable to tearing or other deterioration • Membrane flashings cannot be permanently exposed to sunlight. They are often combined with metal where flashings must project from the wall.

Joint Reinforcing System Properties

Sizes: 10 ft lengths; width should be 2" less than wall Shapes: ladder & truss Configurations: many variations Materials: steel with various finishes and gauges

Reinforced Brick Masonry (RBM)

Steel reinforcing and grouting are added to the masonry wall, to increase its strength, especially in bending and shear.

Brick Bonds

Structural Bonds Cavity (Veneer) Walls - running bond - stacked bond • Headers or rowlocks in a multi-wythe wall serve an important functional purpose, tying together the two wythes. • In a single-wythe wall, different brick bonds may be chosen purely for the visual patterns they create in the exposed face of the wall. • Running Bond: All stretchers • Common Bond: Stretcher courses, with a header row usually every 5 or 6 or 7 courses • English Bond: Alternating stretcher and header courses • Flemish Bond: Alternating stretchers and headers in each course

Shear

sear stress arises from forces parallel to the cross section

Decorative or Architectural Concrete Masonry Units

split-faced block ribbed split-face block ground-face block glazed block, structural glazed facing tiles terra cotta glass block

Brick Firing

• After forming, bricks are dried and then packed into a firing kiln, where they pass through various stages of drying and chemical transformation. • Tunnel kiln: Brick loads pass continuously from one end of the kiln to the other. [Mutual Materials] • Periodic kiln: Batches of bricks are loaded, fired, cooled, and removed. • Firing takes 10 to 40 hours. • Brick placement and firing conditions affect finished brick color, uniformity of shape, hardness, and other physical properties.

Brick Sizes

• Bricks are available in many sizes and standard sizes vary regionally. • Some bricks are sized so that the dimension of one brick plus one mortar joint equals a convenient nominal dimension. • Example: A modular brick combined with a mortar joint occupies 4 inches in width (3 5/8" + 3/8") and 8 inches in length (7 5/8" + 3/8"). • Three courses occupy 8 inches in height( 3 x [2 1/4" + 3/8"] ). • Other bricks do not necessarily conform to convenient dimensions. • Standard: Three courses occupy 8 in. in height =CMU course ( 3 x [2 1/4" + 3/8"] ).

Masonry Loadbearing Walls

• Carry gravity loads from other parts of the building structure (adjacent floors and roof) • In modern construction, almost always reinforced - Greater strength - Much improved resistance to seismic forces • May be composite or cavity wall construction - In loadbearing cavity walls, the inner wythe is usually the loadbearing wythe and the outer wythe or veneer is nonstructural.

Moisture Resistance of Masonry

• Cavity wall construction limits water passage through masonry walls. • Various water repellent coatings, either clear or opaque, can be applied to the wall surface. But coatings should be breathable to allow moisture that does infiltrate the wall to escape. • Mortar and concrete for CMUs can be mixed with additives that increase their water repellency.

Mortar Mix

• Cement is the glue that binds the sand particles together. • Sand [Aggregate] There is almost one cubic foot of sand in a cubic foot or mortar. Sand provides the basic structural capacity of the hardened mortar. • Lime improves the workability of mortar in its plastic state. • Water A minimum amount is necessary for chemical hydration of the cement; additional water is added to produce a working consistency to the wet mortar.

Joint Tooling

• Compacts joint surface to make it more durable and water-resistant • Neatens joint appearance • The concave joint and vee joint shed water most effectively and are the most resistant to freeze-thaw.

Composite Flashings

• Copper or other metals laminated with heavy paper, plastic film, or other materials • Material costs are less than all-metal flashings because the thinner metal sheets are used. • The laminating layers provide added strength, compensating for the thinner sheet metal.

Laying Bricks

• Corner leads are constructed ahead of the rest of the wall. • Levels and string lines are used to keep the wall straight and true.

Brickwork Terminology

• Course: One horizontal row of bricks • Bed Joint: Horizontal joint between courses • Head Joint: Vertical joint between bricks in same course • Wythe: One vertical stack of bricks • Collar Joint: Vertical joint between wythes • Rowlock: Brick laid on its face, with end visible • Stretcher: Brick laid flat, with face visible • Header: Brick laid flat, with end visible • Soldier: Brick laid on its end, with its face visible • Sailor: Like a soldier, but with its broader side visible

Geologic Stone Types

• Igneous: Rock developed in a molten state • Sedimentary: Rock formed from particles deposited by wind and water • Metamorphic: Formerly igneous or sedimentary rock transformed by heat and pressure

Brick Classifications

• Facing brick: Brick with appearance characteristics graded for exposed applications • Building brick: Brick intended for concealed locations where appearance is not a concern • Solid brick: Not less than 75% solid (in any section cut perpendicular to bearing). • Solid bricks are frequently not 100% solid, to reduce weight and the costs of firing. • Hollow brick: Up to 60% void • With hollow brick, larger sized units can be kept lighter in weight • Because of their lighter weight, hollow bricks require less energy to fire. • The larger voids in hollow brick readily accommodate steel reinforcing in reinforced brick masonry.

Flashings and Drainage

• Flashings are built into masonry walls to intercept water that penetrates the wall and direct the water back to the exterior. • Common materials include various metals, synthetic rubber or bituminous membranes, and plastics. • Materials should be chosen with longevity in mind—internal flashings must last as long as the wall.

Masonry Cavity Walls

• Greater resistance to water penetration than solid or composite walls • Multiwythe • A continuous air space between wythes acts as an internal drainage plane. • Water that penetrates the outer wythe runs down the cavity and then is drained back to the exterior. • Wall Ties-Veneer Ties allow water to drip • Wall ties or veneer ties, made of corrosion resistant metal, span the cavity and allow the inner wythe to provide lateral support to the, usually thinner, outer wythe. - Stainless steel: longest lasting - Galvanized (zinc-coated) steel: less expensive • Wall ties come in a great variety of configurations. • Flashings: Continuous waterproof membranes that intercept water in the cavity and redirect it to the exterior • Weep holes: Allow water to drain out from wall • Dampproofing: Waterrepellent coatings applied to the face of the inner wythe to provide additional resistance to water penetration • The mastic air barrier also serves as the water-repellent coating. • The minimum recommended cavity depth is 2 inches, to allow space for masons to keep the cavity clear of mortar droppings during construction. • Water-resistant rigid insulation boards can be inserted into the cavity. But a minimum of 1 inch of clear airspace should be preserved. • Cavity drainage materials: Materials inserted into the cavity to catch mortar droppings and prevent obstruction of weep holes • Mortar droppings should always be minimized, as they form bridges across the cavity that can allow water to bridge the cavity as well.

Mortar Types

• Higher-strength - higher proportion of cement higher compressive strength. • Higher strength mortars are more expensive and have poorer workability characteristics in comparison to lower-strength mortars. • In general, the lowest strength mortar suitable for a particular job is the optimal choice. • Type S and Type N mortars are the most commonly specified.

Granite Group

• Igneous rock • Mixture of mineral crystals; principally feldspar, quartz • Nonporous, strong, durable • Suitable for exposure to severe weathering, ground contact • Many colors • Can accept many finishes, including polished

CMU Weight Classifications

• Lighter weight blocks - Less expensive to transport and lay - Lower thermal conductivity: higher fire-resistance rating • Heavier weight blocks - More durable, Higher compressive strength - Better acoustical isolation between adjacent spaces

Concrete Masonry Dimensions

• Like brick masonry walls, concrete block wall dimensions should conform to the dimensional module of the block, in this case 8 inches. This minimizes the need to cut block or work with small pieces. • Depending on the type of measurement, the number of joint widths in the dimension may be one more, the same, or one less, than the number of blocks.

Expansion & Contraction

• Masonry construction expands and contracts due to changes in temperature, moisture content, and structural loading. • Joints must be provided to allow movement to occur without causing unsightly or detrimental cracking: - Where changes in geometry create stress concentrations - Close to corners - At intervals no greater than 125' in straight walls - At changes in support conditions • Joints are sealed at the surface of the wall, for appearance considerations and to prevent the uncontrolled passage of air and water. • Some joint designs restrict out-of-plane movement between adjacent wall sections while permitting expansion and contraction in the plane of the wall. • Vertical expansion joints in brick veneer on either side of stacked window openings • A flexible sealant material that can expand and contract with movement is applied to the joint. • Sealant color can be chosen to match that of the mortar and sand can be cast into the surface of the sealant before it cures, to imitate the appearance of a mortar joint. • Brick expands slightly over time as it absorbs moisture from the atmosphere. • Many structural systems, especially those of concrete, shrink slightly over time due to long term effects of structural loads. • On multistory buildings, horizontal expansion joints must be provided in brick veneer to allow gradual expansion of the brick. • If these joints are omitted, the veneer will gradually become compressed, bow outward, and eventually fail.

Marble Group

• Metamorphic rock • Recrystallized limestone • Varies greatly in its physical properties and appearance • Many colors, frequently with extensive veining • Easily polished • This group also includes other stone types that can take a high polish but are not true geologic marbles: limestone marble, onyx marble, serpentine marble, etc.

Laying CMU

• Mortar is identical to that used for brick masonry. • Corner leads are laid first. • String lines and levels are used to keep walls straight, plumb, and level. • Joints are tooled and the face of the blocks cleaned as work progresses.

Mortar Type Specification: Proportion Specification

• Mortar types are defined by the proportion of ingredients. • Proportion specification is the simpler and more common method of defining mortar requirements. • Note the higher lime content of lower-strength mortar types. • Note that no lime is added to mortar cement or masonry cement mixes. • Mortar types are defined by minimum strength and other properties demonstrated through laboratory testing for the proposed mix. • This specification method is most suitable to large projects, where the added cost and complexity of laboratory testing can be offset by more flexibility in selecting ingredients and proportions in the mortar mix.

Metal Flashings

• Most expensive and most durable • Stainless steel - Long-lasting - Non-staining - Stiffer and harder to form than copper • Copper - Long-lasting - Runoff from flashing can cause staining by copper oxides - Softer and more easily formed than stainless steel • Galvanized (zinc-coated) steel - Less expensive - Less durable - Not recommended for permanent internal flashings - OK for external, replaceable flashings • Aluminum - Not recommended for masonry walls because this metal reacts chemically with the highly alkaline mortar

Composite Masonry Walls

• Multiwythe - Outer wythe of stone, face brick, or other durable masonry material - Inner wythes of less expensive CMU or clay units which do not require the same level of durability or finish appearance • Solid--no internal cavity - Space between wythes is filled with mortar • Wythes are bonded with: - Header units (in traditional construction) - Metal ties or reinforcing • Most commonly associated with traditional or historic masonry wall construction

Brick Raw Materials Preparation

• Natural clays are excavated from the earth. • These raw materials are ground up and screened to control particle size. • Water is added to achieve a plastic consistency ready for molding into bricks.

Lime Mortar

• No hydraulic cement • Cures by a chemical reaction called carbonation, where atmospheric CO2, combines with the hydroxides in the lime to create carbonates • Has some ability to self-heal hairline cracks that may develop over time; as water and air enter the joint, carbonation can occur and repair the joint • Used primarily for the restoration of historic masonry structures

Ways to select stone

• Past history can be a good predictor of future performance in similar applications and environments. • Petrographic analysis: Microscopic analysis of mineral content and structure • Laboratory Testing: Water absorption, density, compressive strength, dimensional stability, freeze-thaw resistance, chemical resistance, flexural strength, etc.

Mortar Admixtures

• Pigments, colored aggregate • Bond enhancers: Improve flexural strength, freeze-thaw resistance • Set accelerators and retarders: Adjust setting time in cold or hot weather • Water repellents: Improve water resistance (for concrete masonry units only) • Workability enhancers: Ease placement of wet mortar

Masonry Cement

• Proprietary mortar mix of cementitious materials, lime, plasticizers, and other ingredients • No added lime • Convenience and consistent quality of premixed ingredients • Good workability, and improvements in some properties of hardened mortar such as reduced drying shrinkage • Lower bond strength than cement-lime mortars

Stone Masonry

• Rubble: Unsquared stone blocks • Random: Laid without continuous horizontal joints • Coursed: Laid with continuous horizontal joints • Ashlar: Squared blocks • Stones carry their own weight. • Most commonly set in mortar, like brick or CMU • May also be dry set, stacked without mortar (below), or set on shims with sealant-filled joints • Stone blocks carry gravity loads. CMU wall with anchors provides lateral support.

Limestone Group

• Sedimentary rock • Calcium carbonates (oolitic limestone) and magnesium carbonates (dolomitic limestone) • Strength and porosity vary with density • Colors from white, to gray, to red • Normally has a textured finish; only a few types can be polished

Quartz-Based Stone Group

• Sedimentary rock • Sandstone: from quartz deposits • Brownstone, and some varieties of bluestone are varieties of sandstone • Varies in density and porosity • Color is often light, but may vary significantly with types of materials that bind the quartz particles • Cannot be polished

Brick Forming: Molded Bricks

• Soft mud process: Relatively moist clay is pressed into individual molds - Water-struck: Molds are pre-wetted - Sand-struck: Molds are pre-dusted with sand - May be hand- or machine-pressed • Dry-press process: Low-plasticity clays are kept relatively dry and stiff, and machine-pressed into steel molds at high pressure. • Molded bricks frequently are associated with more natural variation in texture and dimensional uniformity than extruded bricks. • Molded brick costs vary with the molding process, but are frequently more expensive than extruded brick.

Special Shapes and Sizes

• Special or custom-shaped bricks can be used to form arches, water tables, and many other surfaces and features.

Concrete Masonry Units (CMUs)

• Stiff concrete mix pressed into metal molds • Steam curing in autoclaves accelerates curing • Standard nominal size: 8" x 8" x 16" • Actual size is 3/8-inch less in each dimension. • Other common sizes: • 8" in length • 4", 6", 10", and 12" width

Stone Cladding, Stone Curtain Wall

• Stone panels mechanically attached to building frame • Attachment system carries the weight of the panels

Brick Masonry Dimensions

• To the greatest extent possible, brick masonry wall dimensions should be conform to the brick module, minimizing the need to cut bricks or work with very small pieces. • Depending on the type measurement, the number of joint widths in the dimension may be one more, the same, or one less, than the number of bricks.

Mortar Joint Deterioration

• Water and freeze/thaw action deteriorate mortar joints over time. • Repointing: Deteriorated mortar is cut out and the joints are refinished with fresh mortar.` • Care must be exercised that the new mortar is not harder or more brittle than the mortar in the remainder of the joint, or early mortar failure or damage to the bricks themselves can result. • "Tuck-Point" restoration

Joining and Sealing Flashings

• Where flashing sections meet, the joints must be made watertight. • Metals are most permanently joined and sealed by soldering or welding. Sealing with mastics is less expensive, but also less permanent. • Membrane and composite flashings are sealed with mastics or adhesive sealants. • Self-adhering flashings are lapped and self adhered to form a watertight seal.

Efflorescence

• White crystalline deposits occur on the surface of masonry when moisture within carries salts from the mortar or masonry units to the surface and then evaporates, leaving the salts behind. • Efflorescence is most common with new masonry and usually decreases over time. • It can be minimized by avoiding contaminants in the masonry ingredients, and by keeping water out of the wall both during and after construction.