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CONCRETE. RAW MATERIALS L. Dvorkin and O.Dvorkin Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com CHAPTER 1 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com 1.1. Concrete. General Concrete can be classified as composite material and that is a combination of different components which improve their performance properties. In general case binder component which can be in hard crystalline or amorphous state is considered as the matrix of composite material. In concrete matrix phase the grains of aggregates (dispersed phase) are uniformly distributed. 22 Classification Types of concret e indication Types of binders Density Types of aggregat es Size of aggregates Workability of concrete mixtures Porosit y of concret e Typical properties Cement, Gypsum, Lime, Slag-alkaline, Polymer, Polymercement Normal-weight , High-weight , Light-weight Normal-weight , Heavy-weight, Light -weight , Inorganic, Organic Coarse, Fine Stiff and Plast ic consistency High-density, Low-density, Cellular High-strength, Resist ance t o action of acids or alkalis, Sulfate resist ance, Rapid hardening, Decorat iveness Structural concrete, Concret e for road and hydrotechnical Exploitat ion purpose construct ion, Concret e for t hermal isolat ion, Radiat ionprot ective concrete, White and Coloured concrete 23 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Concrete classification Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com 1.2. Binders. Classification. Nature of binding properties Concrete can be produced on the basis of all types of glues which have adhesion to the aggregates and ability for hardening and strength development. Organic glues Solutions, pastes Organic – mineral glues Pastes Inorganic glues Solutions, bond Pastes Molten materials, solders Binding and production of composite materials Fig.1.1. Types of adhesives 24 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Periodicity of chemical compounds binding properties Oxide of chemical Oxide Al2O3 SiO2 Fe2O3 Cr2O3 Mn2O3 GeO2 SnO2 BeO -- -- - - - - - MgO -- -- -- - - - - CaO ++ ++ ++ ++ ++ ++ ++ ZnO -- -- -- -- - - - SrO ++ ++ ++ + + + + CdO -- -- - - - - - BaO ++ ++ ++ ++ ++ ++ ++ element Note: fixed (++) and predicted (+) existence of binding properties; fixed (--) and foreseen (-) absence of binding properties. 25 Chemical composition of portland cement clinker is as a rule within following range, %: СаО- 63...66 MgO- 0.5...5 SiO2- 22...24 SO3- 0.3...1 Al2O3- 4...8 Na2O+K2O- 0.4...1 Fe2O 3- 2...4 TiO 2+Cr2O3- 0.2...0.5 Fig. 1.2. Crystals of alite Fig. 1.3. Crystals of belite 26 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com 1.3. Portland cement and its types Compressive strength, МPа Compressive strength, МPа Fig. 1.4. Rate of cement paste hardening under using cements with different grain sizes: 1– <3 µm; 2 – 3…9 µm; 3 – 9…25 µm; 4 – 25…50 µm 3 days Amount of alite, % Fig. 1.5. Relationship between amount of alite and compressive strength of cement 27 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Age of hardening, days 28 days Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com 1.4. Hydraulic non portland cement binders Lime binders Hydraulic lime binders contain materials produced by grinding or blending of lime with active mineral admixtures (pozzolans) — natural materials and industrial byproducts. At mixing of active mineral admixtures in pulverized form with hydrated lime and water, a paste which hardened can be obtained. Typical hydraulic lime binders are lime-ash binders. Slag binders Slag binders are products of fine grinding blast-furnace slag which contains activation hardening admixtures. Activation admixtures must be blended with slag at their grinding (sulfate – slag and lime – slag binders) or mixing with water solutions (slag - alkaline binders). Activation admixtures are alkaline compounds or sulfates which contain ions Са2+, (ОН)- and (SO4)2-. 28 Strength, percent of 28 day strength Age, days Fig. 1.6. Typical curves of cement strength increase: 1 - calcium - aluminate cement; 2 – high-early strength portland cement; 3 – ordinary portland cement 29 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Calcium - aluminate (high-alumina) cements Calcium - aluminate (high-alumina) cements are quickly hardening hydraulic binders. They are produced by pulverizing clinker consisting essentially of calcium aluminates. Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com 1.5. Concrete aggregates Classification of aggregates for concrete Classification indication Grain size Particle shape Bulk density (ρ0) Porosity (P) Kind of aggregates Characteristics of classification indication Fine aggregates ≤5 mm Coarse aggregates >5 mm Gravel Smooth particles Crushed stone Angular particles Heavy ρ0>1100 kg/m3 Light ρ0≤1100 kg/m3 Normal and high - density P≤10% Low - density P>10% Normal, high and low – Exploitation purpose density concrete, Properties of aggregates Concrete for must conform to the hydrotechnical, road and concrete properties other kinds of construction 30