Name: protecting mortar during weather changes
Uploaded: 2024-09-12T16:16:29.000Z
Duration: 1 min 21 s
Channel: JoVE

Durante la stagione fredda, il cemento a rapido indurimento viene utilizzato nella preparazione della malta. Ad esso viene aggiunta acqua calda, mantenendo la temperatura della malta tra 40 gradi e 120 gradi Fahrenheit, fino a quando non viene posizionata.
Per temperature inferiori a 32 gradi Fahrenheit, le unità in muratura e i sacchi di cemento vengono conservati su una piattaforma rialzata, coperti con fogli resistenti all'acqua e riscaldati con stufe.
Il congelamento della sabbia viene impedito riscaldandola con una coperta elettrica o tubi di calore.
Inoltre, i frangivento sono previsti in cantiere se la velocità del vento è superiore a 15 miglia all'ora.
Al termine dei lavori, la parete in muratura viene ricoperta con coperte isolanti per 24 ore per evitare il congelamento.
Durante la stagione calda, le unità in muratura, la sabbia, i sacchi di cemento e le attrezzature per la malta sono protetti dalla luce solare diretta.
Per la muratura con stagione calda vengono praticati il lavaggio dell'attrezzatura per malta con acqua, l'aggiunta di acqua fredda alla miscela di malta e la prebagnatura delle unità in muratura prima della posa.
Al termine dei lavori, viene applicato un nebulizzatore sulla muratura e ricoperta con membrane resistenti agli agenti atmosferici per proteggerla dal sole.

muratura in condizioni climatiche fredde e calde

Nel clima freddo, la costruzione in muratura richiede precauzioni specifiche per garantire che la malta non geli prima di indurirsi, poiché ciò può indebolirne notevolmente la resistenza e l'impermeabilità. La temperatura della malta deve essere mantenuta tra 15,56 °C e 26,67 °C per supportare una corretta idratazione e indurimento. Al di sotto di 4,44 °C, l'acqua della malta deve essere riscaldata, ma non deve superare i 48,89 °C poiché le alte temperature possono ridurre la resistenza alla compressione e all'adesione della malta.

Altre pratiche chiave includono mantenere le unità di muratura e la sabbia asciutte e protette dalle temperature di congelamento, utilizzare sabbia riscaldata per mantenere la malta a una temperatura ottimale e utilizzare cemento di tipo III per un più rapido indurimento. La malta deve essere mescolata in piccoli lotti per evitare il raffreddamento e le postazioni di lavoro dei muratori devono essere protette dal vento e riscaldate se necessario. La muratura appena posata ha bisogno di protezione dal gelo per almeno un giorno e le superfici devono essere coperte per proteggerle da pioggia e neve.

Nel clima caldo, la sfida è impedire che la malta si asciughi troppo rapidamente. Le unità di muratura potrebbero aver bisogno di essere inumidite prima dell'uso per evitare un eccessivo assorbimento di acqua dalla malta. Mantenere le unità di muratura, gli ingredienti della malta e le postazioni di lavoro in ombra aiuta a gestire questo problema. Spesso, la muratura viene trattata con uno spray nebulizzatore e poi coperta con membrane resistenti alle intemperie per proteggerla dalla luce solare alla fine della giornata.

Durante la stagione fredda, il cemento a rapido indurimento viene utilizzato nella preparazione della malta. Ad esso viene aggiunta acqua calda, mantenendo la temperatura della malta tra i 40 gradi e ...

masonry-in-cold-and-hot-weather-conditions

Education

Didattica

JoVE Core

Civil Engineering

Ingegneria Civile

Unit 1

Unità 1

Masonry

Muratura

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

Masonry in Cold and Hot Weather Conditions

protecting mortar during weather changes

Masonry work changes in cold and hot weather because mortar must stay at the right temperature and moisture level. If mortar freezes before it cures, its strength and watertightness can drop. For proper hydration and curing, mortar should stay between 60°F and 80°F.

When the weather is below 40°F, the water used for mortar must be heated. The water should not exceed 120°F, because very hot water can reduce compressive strength and bond strength. Masonry units and sand should also stay dry and protected from freezing. Heated sand can help keep the mortar near the best temperature.

Cold-weather work also calls for Type III cement, which cures faster. Masons should mix mortar in small batches so it does not cool too much before use. Workstations should be shielded from wind and heated when needed. Newly laid masonry must be protected from freezing for at least one day. Surfaces should also be covered to block rain and snow.

Hot weather creates the opposite problem, because mortar can dry too fast. Masonry units may need to be dampened before use so they do not pull too much water from the mortar. Keeping the units, mortar ingredients, and work area in the shade also helps. At the end of the day, masonry is often given a fog spray and then covered with weather-resistant membranes to protect it from sunlight.

Protecting Mortar During Weather Changes

composite masonry walls

Bonding and Materials in Composite Masonry

Composite masonry walls use two or more wythes, or vertical layers, of masonry to form one unified wall. The wythes may use the same material or different masonry materials. They are joined to work together as a single structure. These wythes can be bonded in several ways. Builders may use mortar-filled collar joints, grouted spaces, or rigid metal ties with reinforcement. Masonry header units can also connect the layers, but this method is rare. Metal ties are often preferred because they...

masonry cavity walls

Masonry Cavity Walls and Moisture Control

Masonry cavity walls use two wythes, or layers, with a hollow space between them. The outer and inner wythes are linked only by corrosion-resistant metal ties. This design helps manage water and improve wall performance. When rainwater passes through the outer wythe, it moves down through the cavity. Flashing catches the water and directs it toward weep holes, where it can leave the wall. The inner wythe often has damp-proofing on the cavity side. This layer also works as an air barrier. The...

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How Masonry Walls Support Buildings

Masonry load-bearing walls support floors and roofs and carry those loads down to the foundation. They are built from brick, stone, or concrete masonry units. These walls rely on compressive strength, which means they can resist pushes from above very well. Masonry walls may be reinforced or unreinforced, depending on the building needs. They carry dead loads and live loads while using working stresses that stay below the materials' ultimate strength. That safety margin helps the structure...

masonry curtain walls

Masonry Curtain Walls and Support Systems

Masonry curtain walls use brick or stone veneer as an exterior cladding system. The veneer is supported by the building structure, so the wall can be both attractive and functional. Two main construction methods are used for these walls. One method builds the masonry units in place through traditional layering. The other uses prefabricated panels that are assembled on the ground and then lifted into position. In traditional construction, steel shelf angles attached to the spandrel beam carry...

posttensioned masonry walls

How Masonry Walls Gain Extra Strength

Post-tensioned masonry walls gain extra strength from high-strength steel rods or flexible tendons. These tensioning elements are anchored to the foundation and run vertically through the wall. In some walls, they sit inside the cores of the masonry units. In others, they are placed between the masonry wythes, or layers. The wall is built first with the tensioning elements already in place. After the mortar cures fully, the wall is tightened. Steel rods are tensioned by turning nuts against...

cavity drainage and flashings in masonry walls

cavity-drainage-and-flashings-in-masonry-walls

Moisture Control in Masonry Cavity Walls

Masonry cavity walls use a gap between two wythes, or wall layers, to help control moisture. The cavity is usually at least 2 inches wide, and it may contain insulation. Even with insulation, a clear space of at least 1 inch is kept so water can drain away. Some walls also use a continuous drainage mat to reduce the needed space while still moving moisture out. Weep holes are another key part of cavity drainage. These openings sit at the base of the cavity and let collected water escape. They...

thermal insulation in masonry walls

Masonry Wall Insulation Options

Masonry wall insulation can be placed on the outside, inside the wall, or on the interior surface. The best choice depends on the climate, the building design, and whether the wall is being built new or retrofitted. In hot, dry climates, masonry can help smooth indoor temperatures by absorbing heat during the day and releasing it at night. In many other climates, extra insulation is needed to improve thermal resistance. One common exterior method is an Exterior Insulation and Finish System, or...

expansion and contraction in masonry walls

expansion-and-contraction-in-masonry-walls

Masonry Wall Joints for Temperature and Moisture

Masonry walls change size slightly as temperature and moisture change. Builders account for this movement so the wall does not crack or shift out of place. Thermal movement is usually easy to measure and plan for. Moisture movement is harder to predict. New clay masonry units often absorb water and expand over time in normal outdoor conditions. New concrete masonry units behave differently. They usually shrink as they lose extra moisture gained during production. These opposite changes make...

movement joints in buildings

How Buildings Handle Structural Movement

Buildings are designed to handle movement from temperature changes, moisture changes, and structural deflection. If these changes are ignored, they can cause visible damage or even unsafe conditions. Movement joints give building materials room to move without creating distress. Working joints are the simplest type. They are placed during construction and help materials cope with change as the building goes up. Shingled roofs and wood bevel siding are common examples because they can move with...

types of building separation joints

Building Joints for Movement and Stability

Building separation joints help large or complex buildings move in a controlled way. They split a structure into smaller, separate units. This reduces stress when the building shifts under different forces. The joints are grouped into three main types: volume-change joints, settlement joints, and seismic separation joints. Volume-change joints handle expansion and contraction caused by temperature changes and moisture changes. They are placed where the building mass has discontinuities,...

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Stopping White Salt Crystals on Masonry

Efflorescence is the white, fluffy crystal layer that can form on masonry walls. It happens when water-soluble salts in brick, stone, concrete, or mortar are dissolved by water and carried to the surface. When the water evaporates, the salts are left behind as a powdery deposit. New efflorescence is often seen soon after construction. In many cases, it can be cleaned with water and a brush. It may also fade over time as rain leaches salts out of the masonry surface. If efflorescence appears...

mortar joint deterioration in masonry

Repairing Damaged Mortar Joints in Masonry

Mortar joints in masonry can break down when water collects in them and freezes. The repeated freezing and thawing makes the water expand and shrink. That process creates cracks in the joints and can spread damage over time. As the mortar worsens, pieces may spall, or break off from the joint surface. Loose masonry units can follow, and the wall becomes weaker. Damaged joints also let moisture move into the wall, which adds to the problem. Good construction helps protect mortar joints. Using...

masonry in cold and hot weather conditions

Masonry work changes in cold and hot weather because mortar must stay at the right temperature and moisture level. If mortar freezes before it cures, its strength and watertightness can drop. For proper hydration and curing, mortar should stay between 60°F and 80°F. When the weather is below 40°F, the water used for mortar must be heated. The water should not exceed 120°F, because very hot water can reduce compressive strength and bond strength. Masonry units and sand should also stay dry and...

masonry paving

Masonry Paving Materials and Base Layers

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key terms and concepts

Learn how cold and hot weather affect masonry mortar, from heating materials and using Type III cement to shading, dampening, and fog spraying.

Protecting Mortar During Weather Changes | JoVE K12

JoVE Core Civil Engineering provides a foundational exploration of essential construction materials in civil engineering, focusing on bricks, stones, steel, wood, and concrete through easy-to-understand animated videos. This collection covers the properties, manufacturing processes, and practical applications of these materials. Additionally, the accompanied science-in-action videos demonstrate the research experiments performed in laboratories.

civil engineering

Protecting Mortar During Weather Changes

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