Construction Materials: Conglomerants and Aglomerants

Materials Conglomerants

• Materials unite fragments of one or more substances and provide cohesion

Materials Aglomerants

• These materials can unite fragments and provide cohesion through physical changes
• Examples include bitumen, mud, and glue

Materials Conglomerants

• These materials are able to unite fragments or particles and provide cohesion
• The cohesion occurs due to chemical transformations in the mass, creating new compounds
• Examples are gypsum, lime, and cement

Classifications

• Materials are classified by origin, nature, and behavior in water
• Origin based: natural, artificial, or synthetic
• Nature based: inorganic (lime, gypsum, cement), organic (bitumen, tar)
• Water behavior: aerial (gypsum, aerial limes), hydraulic (hydraulic limes, cements)

Behavior

• Conglomerates mix with aggregates, water, and additives to form new products
• The initial mix is fluid, transforming to solid during adormiment (dormancy)
• The period in which plasticity and molding capacity reduce, is called the dormancy time
• The start and end of this period are termed "principi d'adormiment" and "final d'adormiment"
• Plasticity: Ability to adopt any form due to water
• Emotlament: generating forms from a mold or formwork.
• The mixture hardens at a variable rate depending on environmental conditions and conglomerate characteristics
• Mechanical resistances are acquired during enduriment (hardening)
• Most used conglomerates in construction: gypsum, lime, and cement

Applications

• Arena + Natural Conglomerate becomes Arenosa Stones
• Arena + Artificial Conglomerate makes Mortars
• Arena + Gravel + Natural Conglomerate make Bretxes and Pudingues Conglomerates
• Arena + gravel + Artificial Conglomerate creates Formigons

Gypsum (Guix) and Plaster Introduction

• Gypsum can be natural or construction gypsum

Natural Gypsum

• Sedimentary rock of chemical, saline origin
• Transparent
• It consists of calcium sulfate dihydrate, also known as bihydrate: SO₄Ca 2H2O.

Anhydrite (SO₄Ca)

• Crystallized mineral (rhombic system), white or colorless and colorless when pure, or with color if impure.
• Crystals are formed in fibrous, granular, or compact masses
• Has a hardness of 3 on the Mohs scale.
• Very unstable and eager for water.
• When absorbing water turning to SO₄Ca 2H₂O, resulting in an increase in volume.

Pedra D'Algeps (SO₄Ca 2H₂O)

• Abundant mineral, crystallized (monoclinic system), colorless or white when pure
• With impurities, it gets yellowish, reddish or bluish tones
• Has a hardness of 2 on the Mohs scale.
• Partially soluble in water
• Other gypsum minerals: fibrous gypsum, selenite, gypsum in arrow, alabaster.

Construction Gypsum

• Artificial material, manufactured from natural raw materials such as gypsum stone
• Aerial artificial conglomerate, obtained from partial or total dehydration of gypsum stone
• Its composition: calcium sulfate semihydrate: SO₄Ca ½H2O.
• Additives include set regulators and water retainers

Natural vs Construction Gypsum

• Natural Gypsum has Calcium sulfate dihydrate (SO₄Ca 2H₂O)
• Construction Gypsum has Calcium sulfate semihydrate (SO₄Ca ½H2O)

Qualities of Construction Gypsum

• Mineral soluble.
• Aerial conglomerate
• Material can combine with water to form a stable and resistant crystalline network
• Versatile with many construction applications because of its high comfort, fire resistance, thermal and acoustic insulation
• Considered environmentally friendly and sustainable.
• Industrially exploitable as deposits have high proportions of purity with profitable extraction
• The industrial transformation process is known.
• Easily workable because it remains in a plastic state for enough time allowing molding, flattening, and including reinforcements

Resistance and adaptability

• Due to being an aerial conglomerate, it provides adaptability and resistance
• Its workability allows application where perfect finishes, complex shapes, and designs are required

Energy Saving and Thermal Insulation:

• The molecule composition of the gypsum allows it to fulfill CTE requirements in the basic Estalvi d'Energia document (Basic Energy Saving Document)

Hygrothermal Regulator

• Used for comfort in building interiors
• Its porous microstructure that can store water vapor molecules when there is excess humidity, preventing surface condensation and dampness
• It can release vapor into the environment when it is dry.
• Effects of Heat on Gypsum Stone

Effects of Heat on Gypsum Stone

Raw Material

• Gypsum stone which is calcium sulfate dihydrate (SO₄Ca 2H2O)
• When gypsum stone is subjected to heat, chemical reactions occur, transitioning from calcium sulfate dihydrate to anhydrite
• Between 130 °C and 180 °C: Water is weakly combined at this temperature in a process called dehydration

Gypsum Natural

• (SO4Ca 2H2O) experiences adormiment (dormancy) in the process of converting to
• Gypsum Cooked/Construction (SO₄Ca ½H2O + 3/2H₂O)

Between 180 ºC and 600 ºC

• Further dehydration occurs, releasing the crystal-lized water (½ H₂O) and converting
• Gypsum Cooked/Construction (SO₄Ca ½H2O) to SO₄Ca

Anhydrite can be

• Soluble (180-300 ºC) or Insoluble (300-600 ºC), also called Dead Gypsum.

Between 900 ºC and 1000 ºC

• Calcinatio happens when the SO₄Ca + heat dissociates into SO₂↑ + O₂↑ + CaO CaO + anhydrite combine for hydraulic gypsum

Temperatures and products include:

• Ambient Temp with SO4Ca 2H2O being Calcium Sulfate Dihydrate
• 125-180 °C with SO4Ca ½H2O forming Calcium Sulfate Semi-hydrate
• 180-300 °C forms Anhydrite III soluble
• 300-600 °C forms Anhydrite II insoluble
• 900-1000 ºC forms Anhydrite I, used for hydraulic gypsum
• 1450 °C causes the fusion of gypsum

Fabrication Process for Gypsum

Artisanal process

• Quarry exploitation.
• Spread out to contact weather agents.
• Furnace construction.
• Dehydration stage
• Millstone step
• Expedition stage

Algeps D'Albarracín

• Gypsum (SO₄Ca 2H₂O) contains a variable percentage of clays, silica and a ferrous oxide content
• It is a red stone
• It is the only gypsum to be used outdoors because the clay gives elasticity to withstand temperature changes
• Gives impermeability, while silica gives higher hardness

Industrial Process

Exploitation of the quarry (or extraction). Preparation of the mineral (hacking, transport and crushing). Dehydration is a stage. Grinding and storage step. Additive treatment: Packaging is required. Expedition process

Industrial Quarry Exploitation Process

• Has a mining grid
• Also prospection and selection, followed by exploitation
• Controlled explosion systems, firing in a delayed series occurs and material is grouped

Industrial Mineral Preparation Stage

• Consists of Tapping
• Primary crushers used are 0-200mm
• Secondary 0-8 mm
• Screening to remove sterile components occurs

Industrial dehydration

• Involves the loss of water by the dissociation of the molecule

Gypsum is present as

• Gypsum Natural where Calcium sulfate dihydrate is used.
• It then dehydrates to produce Cooked Gypsum/ Gypsum Construction material when Calcium sulfate semihydrate is discharged during Adormiment
• Gypsum Natural (SO₄Ca 2H₂O) + heat then dehydrates to SO₄Ca + 2H2O with Anhydrite Soluble/Insoluble released

Industrial Dehydration

• Involves furnaces
• Direct fire furnaces, in continuous cycle using two or three tubes in a rotatory fashion
• Indirect fire furnaces use a discontinuous cycle in a rotatory way

Industrial Temperature

• Up to 180 ºC for semi-hydrate or lasting from 180 to 600 ºC for anhydrite stage
• Dimensions of particles (ball mill)
• Has low reactivity
• A low time has a high reactivity

Industrial Milling and Storage

• Milling is done for refining via Granulometry
• Intermediate Storage stabilizes the product and must be moisture-free which impacts its quality
• There is an exchange of water molecules to have a homogeneous product.

Intermediate Storage takes

• 3 months
• It obtains homogeneousness as it obtains a base product, but it also obtains finish product

Industrial additive treatments

• Improves open time (dormancy time)
• Involves adding color
• Can be adding Organics or inorganics

Influence Of Water/Gypsum Ratio On Setting Time

• A/Y ratio should be 0.187
• Hydration reaction is exothermic, needs more water to allow for evaporation
• A/Y habitual weight ratio is 0.5 - 0.6 - 0.7.
• The type of open time depends on whether it is gypsum or plaster
• Setting and hardening due to the loss of remaining water, greater water left increases the pour network, which creates porosity when the water evaporates and causes less resistance.

Equations exist for Influences of Mixing Water/Gypsum on Setting Time

• An equation exits for the Principles setting linear equation shown by setting time = ( a/y - 0.2) / (0.6 / tos)

There is an equation for a linear final setting equation

T= ((A/Y) / (0.8) * T0,8

Storage Of Majority And Minority Products occurs

• Siting for majority products are usually gypsum based and store plaster
• Minority products intervene in low proportions

Dosing

• Dosing can be individual weight or accumulated weight

The designation for Gypsum follows the UNE 13279-1:2009 table for special and building gypsum

Ex: Gypsum for Building Construction in 13279-1 should be B1/50/2 indicating the types of gypsum, European Standards of EN13279-1, a symbol (UNE EN 13279-1), Dormancy > 50 mins, and compressive strength > 2M/mm2

Uses in Construction show gypsum added for:

• Acoustic benefit
• Thermal benefit
• Controls humidity
• Adds fire resistance

Uses Of Gypsum In Architecture

• A1 type Gypsum is used in construction and manufacturing of plaster.
• A3 types: Used in prefabricated structures
• B1 types used as gripping mortars for structures

Effects of Caloric Heat on Gypsum:

• Initial stage from about 130-180 degrees Celsius the crystalized water is weakened until the gypsum converts when heated.
• From then on it could convert into anhydrite to be re-heated.
• From 900 degrees it then desegregates from calcium molecule.

Methods to Prepare Application:

• Preparation of work involves determining the roughness, adherence, and cleanliness of the surface to be treated.
• Grandiose surfaces often mean it is best to use an application with an open time.

Application

• Plaster applications can be "a bon vista", with use of straight projection, or using the more accurate approach.

A Bona Vista Approach

• A straight or projected plane is used and the plaster is applied, the surface is flattened, and the operator's experience dictates the result.
• A coat is applied with a smaller, second coat adding quality and improving the smooth feel.

Mestrejat

• Mestrejat consists of leveling the surface through the use of guides ensuring a better flatness.
• Metallic rules are wedged at a distance from the parament equal to the grossness of the trim.

Next process involves

1. Rules are supported via plaster or clay.
2. The rule plane is constructed as vertical.
3. The parament is filled with plaster up to the rules

• A plan is checked and the space between is regulated further for the Mestrejat.
• To finish apply paint at the master areas to escatar the application and produce the fine results.