Calcareous Binders Calcined and Non-Hydraulic Calcined and Hydraulic Clinkered and Hydraulic • Fat lime (high CaO) • Natural hydraulic lime • Grappier • Lean lime (moderate impurity) • Selenitic lime (e.g. Scott’s cement) • Calcium aluminate (e.g., ciment fondu) • Intermediate lime (moderate MgO) • “Roman” cement (e.g. Parker’s Roman) • Expansive cements • Dolomitic lime (high MgO) • Natural cement (e.g. Rosendale) • (Types I - V in the U.S.) • Type S or Type N (special or normal) • White portland cement • Forms include lump lime, lime putty, dry lime hydrate

Gypsum-Based Binders Pozzolans • Plaster of Paris Natural Artificial • Cement plaster • Volcanic ash or trass • Brick or ceramics • Keene’s cement • Volcanic earth • Calcined clay (e.g. ) • Diatomaceous earth • Rice husk ash • Smelting slag • Ground granulated blast furnace slag (may also be hydraulic) Blended Cements • (some classes may also be weakly hydraulic) • Portland cement - hydrated lime • or microsilica • Masonry cement • Mortar cement • Plastic cement • Lime-pozzolan • Slag cement Earthen Binders • Selenitic lime • Adobe • Hydraulic lime (Europe) • Bousillage • Etc. (e.g. wide variety of grouts and specialty materials) Organic Binders (Natural or Prepared) Chemical Cements • Bitumen (asphaltic binders) • Sorel cement (Mg or Zn-based) • Sizing (e.g., animal glues) • Starches (e.g. stale beer) • Proteins (e.g. casein) • Resins A Brief Timeline of Construction Binders

Pre-1800 Earthen binders, gypsum, common lime, lime-pozzolan 1750’s Hydraulic lime (Europe) 1796 Parker’s Roman Cement (English natural cement) 1818 American natural cement (Syracuse, NY) 1824 Portland cement patented in England 1828 (widespread American natural cement) 1840’s True portland cement in Europe 1867 Sorel cement (chemical cement used primarily for cast stone) 1870 Scott’s Cement (selenitic lime) 1878 American portland cement (Saylor’s Coplay plant) Late 19th C. Slag cements with lime 1890’s White cements (Lafarge grappiers first, true white portlands later) 1890’s Significant production of calcined gypsum for wall plaster in the U.S. ~1900 Introduction of the rotary kiln in portland cement manufacture Early 20th C. Slag cements with portland cement ~1910 Ciment fondu (calcium aluminate cement) 1910’s Dry lime hydrate (prepackaged) 1920’s Masonry cement

Paris Basin

Ukraine Satin spar from China

India Gypsum Processing and Hydration

• Burn gypsum at low temperature to produce hemihydrate (i.e. bassanite, i.e. raw gypsum plaster)

CaSO4·2H2O + Heat → CaSO4·0.5H2O • Burn at higher temperature to produce anhydrite (either soluble anhydrite or dead burnt anhydrite)

CaSO4·0.5H2O + Heat → CaSO4 • Add water to rehydrate (technically dissolution and recrystallization of fine gypsum needles in interconnected network)

CaSO4·0.5H2O (bassanite) + Water→ CaSO4·2H2O (gypsum)

CaSO4 (sol. anhydrite) + Water→ CaSO4·2H2O (gypsum) Gypsum Hydration

Plaster of Paris

Keene’s Cement Types of Gypsum-Based Binders

• Plaster of Paris Relatively pure. Burned at low temperature to produce hemihydrate. • Cement plaster More impurities than PoP. Similarly burned at low temperature to produce hemihydrate. • Keene’s cement (et. al.) Burned at high temperature to produce anhydrite. Soaked or intermixed with alum or other salt. Refired and ground. Qualities of Gypsum-Based Binders

• Fine-textured, preserves details when cast. Capable of being worked or honed • Hardens rapidly • Volume stable and potentially somewhat expansive • Lightweight • Variable in hardness (PoP relatively soft, Keene’s cement relatively hard) • Moderate in strength • Brittle • Permeable • Fire-resistant • Low acoustical transmission • Relatively water-soluble • Can release sulfate into solution if leached

Gypsum

Gypsum Mortar Calcareous Binders Calcareous Binders Calcined and Non-Hydraulic Calcined and Hydraulic Clinkered and Hydraulic • Fat lime (high CaO) • Natural hydraulic lime • Grappier cement • Lean lime (moderate impurity) • Selenitic lime (e.g. Scott’s cement) • Calcium aluminate cements (e.g., ciment fondu) • Intermediate lime (moderate MgO) • “Roman” cement (e.g. Parker’s Roman) • Expansive cements • Dolomitic lime (high MgO) • Natural cement (e.g. Rosendale) • Portland cement (Types I - V in the U.S.) • Type S or Type N (special or normal) • White portland cement • Forms include lump lime, lime putty, dry lime hydrate

Source rocks • CaO from limestone, marble, shells, etc. • MgO from limestone or marble

• SiO2 from quartz and clay

• Al2O3 from clay or bauxite ore

• Small amounts of Fe2O3 from just about everywhere. Note that industrial waste materials such as slag may also be used as substitutes for some of the natural raw materials.

The Lime Cycle

• Calcination (firing limestone to produce free lime)

CaCO3 + Heat → CaO • Slaking (adding water to produce hydrated lime)

CaO + Water→ Ca(OH)2 + Heat • Drying (not yet curing but becoming rigid through loss of water)

Ca(OH)2(aq) - Water→ Ca(OH)2(s) • Curing (gaining strength through conversion to calcium carbonate)

CO2 + H2O → H2CO3

H2CO3 + Ca(OH)2 → CaCO3 + 2H2O Actual reactions

CO2 + Ca(OH)2 → CaCO3 + H2O Simplified reaction

Dolomitic lime engages in similar reactions but more sluggishly and there is still some uncertainty in the exact chemical reactions. As a rough guide, replace every “Ca” with “0.5CaMg” Lime Types Compositional types • High calcium lime (e.g. fat lime) • Lean lime (moderate impurity but not hydraulic) • Intermediate lime (moderate MgO content) • Dolomitic lime (high MgO)

Physical types • Lump lime (free lime) • Crushed or powdered free lime • Lime putty • Dry lime hydrate (by sprinkling on site or plant-hydrated)

Quality types • Fat lime vs. lean lime • Type N vs. Type S High Calcium Lean Lime Magnesium Lime CaO Intermediate Lime Grappier cement American natural cement European natural cements Portland cement 0.25 0.75

0.50 0.50

0.75 0.25

MgO 0.25 0.50 0.75 SiO2

Qualities of Lime Binders

• High plasticity • Loses volume on drying and curing (shrinkage) • Hardens very slowly and curing is inhibited if too wet or too dry • Moderately low in density • Not highly water-soluble once cured • Low in hardness and in strength • Low elastic modulus (i.e. flexible) • Highly permeable Pozzolans Pozzolans Basic Principles of Pozzolans (aka: Supplementary Cementitious Materials

Pozzolans Natural Artificial • Volcanic ash or trass • Brick or ceramics • Volcanic earth • Calcined clay (e.g. metakaolin) • Diatomaceous earth • Rice husk ash • Smelting slag • Ground granulated blast furnace slag (may also be hydraulic) • Fly ash (some classes may also be weakly hydraulic) • Silica fume or microsilica

• Pozzolans contain glassy or amorphous silica

(± CaO and Al2O3) • Calcareous binders have pore water that is

saturated with Ca(OH)2, a strong base • All types of silica are soluble in basic solution and this is enhanced when the silica is poorly crystalline. • The freed silica along with the calcium in the pore water combine to form CSH. In some cases, CAH is formed as an additional reaction • These hydrates are the active ingredients in hydraulic binders. Qualities of Pozzolan-Modified Binders

• Allows curing under water when mixed with nonhydraulic binder • Tends to slow set time and strength gain when mixed with portland cement • Decreased permeability • Increased ultimate strength • Increased elastic modulus • All of the above can be modest or dramatic depending on chemistry • Reaction rates often slow. Changes in hardened properties may continue for many years. • Much of the CSH or CAH is created after the mixture is hardened • Consumes CH. Reduces susceptibility to chemical reactions that depend on hydroxide concentration (e.g. sulfate attack, alkali-silica reaction) Hydraulic binders • Undergo chemical reactions with water to form stable hydrates • Capable of setting under water • Remain hardened when left under water indefinitely Hydraulic Reactions • Calcium silicate + water → CSH + CH + Heat • Similar reactions with calcium aluminate to produce CAH • Also ± AFm, AFt, hydrogarnet, etc.

What is important is that the CSH and the CAH are the primary binding materials. Other phases are typically coarser and provide less direct benefit. To some extent, they control reaction rates at early stages. They may also affect durability. Role of Mix Water All else being equal, increasing mix water content... • Increases plasticity or flowability in fresh mixes • Reduces the heat generated by exothermic reactions and may reduce reaction rate • Increases degree of hydration in hydraulic phases • Increases potential for bleed and segregation • Increases capillary porosity • Increases content of calcium hydroxide and other weak phases • Increases thickness of transition zone adjacent to aggregate • Decreases strength

Terminology

• Water to binder ratio (w/b). Used mostly in mortars when the binder is lime or when two binders are present. • Water to cement ratio (w/c). Used mostly when talking about older concrete or cast stone construction. • Water to cementitious materials ratio (w/cm). Introduced when SCMs became popular. Now used widely even when SCMs are absent. Mineralogy of Calcareous Binders Calcareous Binders Calcareous Binders Calcined and Non-Hydraulic Calcined and Hydraulic Clinkered and Hydraulic • Fat lime (high CaO) • Natural hydraulic lime • Grappier cement • Lean lime (moderate impurity) • Selenitic lime (e.g. Scott’s cement) • Calcium aluminate cements (e.g., ciment fondu) • Intermediate lime (moderate MgO) • “Roman” cement (e.g. Parker’s Roman) • Expansive cements • Dolomitic lime (high MgO) • Natural cement (e.g. Rosendale) • Portland cement (Types I - V in the U.S.) • Type S or Type N (special or normal) • White portland cement • Forms include lump lime, lime putty, dry lime hydrate

Source rocks • CaO from limestone, marble, shells, etc. • MgO from limestone or marble

• SiO2 from quartz and clay

• Al2O3 from clay or bauxite ore

• Small amounts of Fe2O3 from just about everywhere. Note that industrial waste materials such as slag may also be used as substitutes for some of the natural raw materials.

Combination (during calcination)

• Calcium carbonate calcines to create free lime • Clays dehydroxylate to produce amorphous aluminates and silicates • Quartz converts first to high temperature silica phases and eventually fuses • At various temperatures, calcium oxide combines

with SiO2 and Al2O3 to produce calcium silicates, calcium aluminates, and calcium aluminosilicates Nonhydraulic lime rock

Hydraulic lime rock

Hydraulic Lime Classification

• Natural hydraulic lime is classified under EN459-1 • Categories include NHL2, NHL3.5, and NHL5. • The numbers refer to the minimum compressive strength (in MPa) at 28-days when prepared in a standardized way • 1 MPa = 145 psi Courtesy of Kurt Burmeister American Natural Cement

Natural Cement Provenance Rosendale (NY) Syracuse (NY)

Howard (GA) Parker’s Roman High Calcium Lean Lime Magnesium Lime CaO Intermediate Lime Grappier cement American natural cement European natural cements Portland cement 0.25 0.75

0.50 0.50

0.75 0.25

MgO 0.25 0.50 0.75 SiO2 Hydraulic Lime / Natural Cement Comparison

Property Natural hydraulic lime American natural cement

Chemistry High calcium, variable SiO2, Al2O3 Dolomitic, mostly high SiO2,Al2O3 Color White, light gray, very pale yellow Brown, ochre Plasticity Often high Often harsh Favors moderate aggregate contents Favors low aggregate contents with Aggregate with broad gradations narrow gradations Set time Slow Fast Shrinkage Minor to moderate Virtually none to slightly expansive Curing Hydration and carbonation Mostly hydration Also variable but slightly higher Strength Variable but moderate on average than NHL on average Also variable but somewhat lower Permeability Variable but relatively high than NHL on average Modulus of elasticity Moderately high Moderately high Durability Moderate High

Portland Cement

• Raw feed carefully selected and blended to meet specific composition • Clinkered at high temperature to cause raw feed to fully recrystallize • Contains the following before further processing

– C3S or tricalcium silicate or alite

– C2S or dicalcium silicate or belite

– C3A or tricalcium aluminate

– C4AF or tetracalcium aluminoferrite or just ferrite • Typical additives at the plant – Gypsum for set control – Crushed limestone for reduced greenhouse emissions

General Qualities of Portland Cement Binder • Not especially plastic but reasonably workable • Heat of hydration moderately high • Moderate set time (i.e. hours) • Fully hydraulic • Rapid strength gain with ~95% ultimate strength within a month or so • Low permeability, water-resistant • High strength relative to other binders • High elastic modulus relative to other binders (stiff and brittle) • Slow to carbonate and high pH protects embedded steel • Sensitive to reactions requiring CH as a reactant (e.g. sulfate attack)

Trends since 1878 • More consistent composition due to introduction of rotary kiln ca. 1900 • Finer grinding with today’s cements mostly passing a No. 200 sieve • Increase in the alite composition for higher early strength gain American Portland Cement Types

• Type I General duty • Type II General duty with moderate sulfate resistance. May find as Type I/II • Type II(MH) Same as Type II with moderate heat of hydration. • Type III High early strength • Type IV Low heat of hydration • Type V High sulfate resistance • Type VI Does not exist. Proposed as a crack-resistant cement. • Types IA - VA All same as above with the inclusion of an air-entraining admixture. • White portland cement Usually only available as Type I/II. Reduced iron content to minimize if not eliminate ferrite. Specialty Binders Slag-lime Grappier Cement

Selenitic Lime Ciment Fondu Other Binders • Earthen binders. Used for adobe brick or as wall insulators. Sometimes mixed with lime and used for economical masonry work. • Non-staining cements. Products for use with light-colored limestone or marble masonry. There seems to be geographic patterns with slag-lime blends near steel-producing centers (i.e. South and Midwest). Grappier cement in the Northeast including possibly eastern Canada. Ultimately replaced by white portland. • Calcium aluminate cements (including Ciment Fondu). Fast set times and high early strength. Popular in Canada for masonry late 19th C. Popular in parts of Europe for early 20th C concrete. Stability issues and now used almost exclusively for small scale specialty applications (e.g. GFRC castings, anchor grouts, etc.) • Selenitic limes. Popular for plaster work especially in 19th C Europe. Also as a general alternative to hydraulic lime. • Expansive cements. Usually based on sulfate and aluminate chemistry (e.g. crystallization of ettringite). Used for grouts and some carefully controlled flatwork. • Prepackaged masonry products. Masonry cements, mortar cements, and portland-lime cements for masonry. Plastic cements for stucco. • Organic binders. Suspected by Walsh to have been an important part of Romanesque Revival aesthetic mortar mixtures. More to come??? • Etc….