Construction materials European Master Dr. M BOUTOUIL Ecole Supérieure des Travaux de la Construction Caen- FRANCE
Preamble ESITC : Higher School in Civil Engineering engineers for construction management, engineering department…
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Objective To understand construction materials structures and compositions, To know their properties and the influence of microstructures on these properties, Better, appropriate and successful use Better understanding and prediction of service life materials
Laser Mégajoule, Gironde Dr. BOUTOUIL. ESITC
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PLAN I. Different categories of construction materials : concretes, ceramics, metallic materials:
Compositions and structures: specifications for basic concrete constituents
Physical and mechanical properties Standards
II. Characterization techniques in materials science:
Mechanical tests Microstructure analyses
III. Innovative materials and new developments: Dr. BOUTOUIL. ESITC
New concretes Reuse of soils and sediments in construction Life Cycle Analysis : LCA 4
I. Different categories of constructions materials: concrete
Concrete Definitions : Composite material that consists of a binding medium within which are embedded particles or fragments of aggregates. In hydraulic-cement concrete, the binder is formed of a mixture of hydraulic cement and water. Raw material for construction : complex, living, durable, expressive material. Must be designed, formulated and worked carefully provide the required properties, achieve high technical structures. Two main properties : Resistant and low life-cycle cost Workable material : can be molded and cast
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I. Different categories of constructions materials: concrete
Concrete Understanding concrete properties and performances : based on knowledge of its constituents and their physical and chemical interactions in different environments. Aggregates
Cement Admixtures
Water
Contents / Mix
Concrete
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I. Different categories of constructions materials: concrete
Concrete and standards A durable concrete is one that performs satisfactorily in the working environment during its anticipated service life Concrete performances are conditioned in particular by respecting some specifications on concrete. EN 206-1 (NF, BS…) : “specification, performances, production and conformity” of concrete (for structures) Approved by CEN on May 2000 after 20 years work by the TC 104 Came into effect in the EU countries on ≠ dates : 1st January in France, 15th February in England. Has National Annex to allow variations taking into account to the climate and technical specificities.
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I. Different categories of constructions materials: concrete
Concrete and standards EN 206-1 (NF, BS…) : “specification, performances, production and conformity” of concrete (for structures) Is a real progress : enhance and harmonize quality and durability of concrete in EU Take into account new advances in concrete science Take into account the working environment Defines responsibilities of specifier, producer and user of concrete , More rigorous conformity criteria and checking Obligation to mention chloride content in concrete
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I. Different categories of constructions materials: concrete
Concrete and standards EN 206-1 (NF, BS…) : “specification, performances, production and conformity” of concrete (for structures) Is fully compatible with the design code for all concrete structures in Europe : Eurocode 2. Includes and in links with: Standard for tests on fresh concrete EN 12350 Standard for test on hard concrete EN 12390 Standards for constituent materials: EN 197 - Cement EN 12620 - Aggregates for Concrete EN 13055 - Lightweight Aggregates EN 450 - Fly ash for concrete. Definitions, requirements and conformity criteria EN 934 -Admixtures for concrete, mortar and grout EN 1008 : Mixing water for concrete Dr. BOUTOUIL. ESITC
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I. Different categories of constructions materials: concrete
Concrete Understanding concrete properties and performances : based on knowledge of its constituents and their physical and chemical interactions in different environments. Aggregates
Cement Admixtures
Water
Contents / Mix
Concrete
Dr. BOUTOUIL. ESITC
influence hardness, abrasion resistance,elastic modulus 10
I. Concrete - Aggregate
Aggregates: sand and gravel EN 12620 - Aggregates for Concrete : specifies sand and gravel characteristics ( (bulk density) > 2000 kg/m3) to be acceptable for concrete specifications and requirements
aggregate (kg/m3)
concrete (kg/m3)
Normal weight aggregate
> 2000
2200 to 2400
Lightweight aggregate
< 2000
< 1800
> 3000
< 3200
Aggregate type
perlite - thermal insulators expanded shales – structural concrete
Heavyweight aggregate
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I. Concrete - Aggregate
Aggregates: sand and gravel specifications and requirements Consists of physical and chemical properties with an important role towards fresh and hard concrete Intrinsic characteristics : depends on the mineralogy of the rock and the quality of the quarry Chemical characteristics, bulk density, crushing strength, abrasion resistance, porosity and water absorption, soundness, frost resistance (freezing and thawing)
Making characteristics : depends on the process of making the aggregates Particles characteristics (size, shape and texture) Sand property Dr. BOUTOUIL. ESITC
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I. Concrete - Aggregate
Aggregate characteristics that affect concrete properties
specifications and requirements
After P.K. Mehta and P.J.M. Monteiro Dr. BOUTOUIL. ESITC
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I. Concrete - Aggregate
Aggregates: sand and gravel Source of aggregates: Natural aggregates: result from weathering, natural abrasion and deposition of particles and from crushed stone (quarry). Loose rocks: cost effective - near the surface, smooth particles Massive rocks: Igneous Rocks, crushed particles Mineral particles ranging from 0 to 125 mm in size First criteria/characteristic : mineralogy granite, diorite Sandstone, limestone Gneiss, mica-schist Dr. BOUTOUIL. ESITC
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Siliceous Calcareous Siliceous-Calcareous
I. Concrete - Aggregate
Aggregates: sand and gravel Source of aggregates: Artificial aggregates: Mineral particles resulting from thermal and mechanical process : blast furnace slag, by-product of metallurgic industries. Not a high quality aggregate :
Dr. BOUTOUIL. ESITC
Some impurities
Not used for prestressed concrete
Used for blocks
Much more value as a cementing material
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I. Concrete - Aggregate
Aggregates: sand and gravel Source of aggregates: Recycled aggregates: obtained from inorganic matter used in construction: concrete from building demolition (recycled concrete)
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I. Concrete - Aggregate
Aggregates: sand and gravel Source of aggregates: Recycled aggregates: Aggregate is surrounded by cement paste coating, gypsum, etc. Silt, clay increase water requirement (wash them out) Cost of crushing, grinding, dust control, and separation of undesirable constituents
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I. Concrete - Aggregate
Aggregates: sand and gravel Grain size distribution: Dimensional distribution of particles:
Fillers
d/D
d=0 and D< 2 mm
Sand (fine, medium and coarse)
d/D
d=0 and D 4 mm
Gravel (fine, medium and coarse)
d/D
d 2 mm and D 63 mm
Affects the following concrete properties: water demand, cement content and workability. Dr. BOUTOUIL. ESITC
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I. Concrete - Aggregate
Aggregates: sand and gravel Fineness modulus: is the sum of the total percentages retained on each of the specified sieve divided by 100. The specified sieves are 0,16 0,315 – 0,63 – 1,25 – 2,5 and 5 mm. Indicates how sand is fine: 2,2 < FM < 2,8
Shape: Round, angular, elongated, flaky Rough-textured and elongated particles require more cement paste to produce workable concrete mixtures, this increases the cost.
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I. Concrete - Aggregate
Aggregates: sand and gravel Sand property: absence of undesirable impurities Fine elements content: “Equivalent Sand” test “Methylene blue value”: Clay fraction and activity
Affects fresh and hard concrete properties:
Increases water demand: W/C Decreases concrete resistance Chemical reactions with cement: expansive crystals (sulphates) and inhibition of hydration reactions (organic matter) Loss of adhesion between aggregates and cement paste Dr. BOUTOUIL. ESITC
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I. Concrete - Aggregate
Aggregates: sand and gravel Physical and mechanical characteristics: Bulk density: 1400 to 1600 kg/m3. Solid density : 2500 to 2600 kg/m3. Crushing strength: Micro-Deval test : Friable particles and soft pieces are easily broken down into smaller particles or create additional fines. Damages and deterioration of concrete : lowering concrete strength and durability.
Abrasion resistance: Los Angeles test : aggregates are rolled in a steel drum together with 11 steel balls. The rolling continues for 500 revolutions, after which the percentage of the test portion that passes a 1.60 mm sieve is determined by washing then sieving. This percentage is the Los Angeles coefficient (LA < 40 or 30).
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I. Concrete - Aggregate
Aggregates: sand and gravel Physical and mechanical characteristics: Porosity and Water absorption: A high porosity is harmful to concrete quality. It makes easier the penetration of water into concrete:
Deleterious substances (chlorides, sulphates)
Deterioration due to frost.
Coefficient of absorption : Ab = (Wet mass – Dry mass) / Dry mass < 5 or 2,5 % (severe conditions)
Frost resistance: Aggregate is considered unsound when volume changes in the aggregate induced by weather such as alternate cycles of wetting and drying or freezing and thawing result in concrete deterioration.
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I. Concrete - Aggregate
Aggregates: sand and gravel Chemical characteristics: responsible of major deterioration of concrete Chloride ions content: Chlorides are know to modify the kinetic of cement hydration and to cause corrosion in reinforced concrete Chlorides ions content must be limited to 0,1 %
Sulphur and sulphate contents: If present in sufficient (high) content, sulphates react with hydrated cement and results in concrete swelling. Sulphur : S < 0,4%. Sulphates : SO3 < 0,2%.
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I. Concrete - Aggregate
Aggregates: sand and gravel Chemical characteristics: responsible of major deterioration of concrete Alkali-silica reactivity (ASR) : occurs either in mortar or concrete. A
deleterious chemical reaction between hydroxyl (OH–) ions associated with alkalis (sodium and potassium) present in cement or other sources and certain reactive siliceous components that may be present in coarse or fine aggregates, produces a gel. When this alkali-silica gel absorbs moisture, it expands, and eventually produces cracks in aggregate particles as well as in the cement paste in concrete. Three conditions must be satisfied for expansive ASR to occur. 1. A reactive form of silica or silicate must be present in the aggregate. 2. Sufficient alkali, sodium (Na) and/or potassium (K), mainly from cement, must be available. 3. Sufficient moisture, i.e., not less than 85% relative humidity (RH) in the pore structure of the concrete or mortar, is required.
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I. Concrete - Aggregate
Aggregates: sand and gravel Chemical characteristics: responsible of major deterioration of concrete ASR damages in a parking apron at Naval Air Station. California (After P.K. Mehta and P.J.M. Monteiro)
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