Concrete Properties, Operations and Types PDF

Department of Urban & Infrastructure Technology Course on Engineering Materials (UE-104) NED University of Engineering &Technology, Karachi Course Instructor: Narm...

Department of Urban & Infrastructure Technology Course on Engineering Materials (UE-104) NED University of Engineering &Technology, Karachi Course Instructor: Narmeen Tanweer (Digital lecture) Email: [email protected], ([email protected]) Department of Urban & Infrastructure Technology Lecture - 17 on Engineering Materials (UE-104) NED University of Engineering &Technology, Karachi Department of Urban & Infrastructure Technology  Concrete Contents Properties of Concrete Operations for Concrete Types of Concrete Fresh State Storage of material Regular concrete o Workability Proportioning and batching High-strength concrete o Bleeding Mixing High-performance concrete Transporting Self-consolidating concrete o Segregation Placing Vacuum concretes o Harshness Compacting Shot-Crete Hardened State Finishing Pervious concrete o Strength Curing Stamped concrete o Durability Air-entrained concrete o Impermeability o Volume Change  Properties of Concrete Fresh Concrete Fresh concrete or plastic concrete is a concrete at the mixing stage. In fresh state, concrete can be transported, placed, compacted and finished without segregation. A proper mix should maintain its uniformity inside the forms and should not bleed excessively. It should set within a reasonable amount of time and hydrate in a manner that ensures adequate strength when the structure is put to service. Some of the properties of concrete discussed below are: i. Workability ii. Segregation iii. Bleeding iv. Harshness  Properties of Fresh Concrete (cont’d) Workability The ease with which a fresh concrete mix can be handled from the mixer to the final structure. Workability is expressed through three mutually independent characteristics: o Consistency: The consistency of the mix should be such that it concrete can be transported, placed and finished sufficiently easily and without segregation. o Mobility: A concrete which has a high consistency and which is more mobile. o Compactibility: It is essential to compact concrete fully to drive away all entrapped air to obtain the optimum density. Every job requires a particular workability. The workability assumes full significance of the type of work, thickness of section, extent of reinforcement and mode of compaction. Workability is a parameter, a mix designer is required to specify in the mix design process, with full understanding of the type of work, distance of transport, loss of slump, method of placing etc.  Properties of Fresh Concrete Measurement of Workability- Slump Test It represents the ability of concrete to be mixed, transported, placed, compacted and finished with a minimum loss of homogeneity. It provides the following information; o Consistency between batches https://www.youtube.com/watch?v=yzpWGrh9j6Y o Checks if correct amount of water is added to the mix o Used to ensure uniformity of different batches of similar concrete under field conditions o To ascertain the effects of plasticizers on their introduction Properties of Fresh Concrete  Properties of Fresh Concrete Measurement of Workability- Slump Test When the cone is removed the slump may take one of these forms; i. True slump: In a true slump, the concrete simply subsides keeping more or less to shape. It gives correct information. ii. Shear slump: In a shear slump, the top portion of the concrete shears off and slips sideways. Test should be repeated and if shear slump persists then it is a harsh mix with lack of cohesion in the mix. iii. Collapse slump: In a collapse slump, the concrete collapses completely. iv. Zero slump: Mixes of stiff consistence have a zero slump  Properties of Fresh Concrete Factors Affecting Workability Water content o Higher the water/cement ratio, higher will be the water content per volume of concrete and concrete will be more workable. o Generally, a water cement ratio of 0.45 to 0.6 is used for good workable concrete without the use of any admixture. o Generally designed concrete uses low water/cement ratio so that desired strength and durability of concrete can be achieved. Cement Content o More the quantity of cement, the more paste will be available to fill the voids. o Thus reduce the friction between aggregates and smooth movement of aggregates while performing the operations of concrete. o The cement with increase in fineness will require more water for same workability than the comparatively less fine cement.  Properties of Fresh Concrete Factors Affecting Workability Mix proportion o Mix proportion of concrete states the ratio of fine aggregates and coarse aggregates w.r.t. cement quantity. o This can also be called as the aggregate cement ratio of concrete. o The more cement is used, concrete becomes richer and aggregates will have proper lubrications for easy mobility or flow of aggregates. o The low quantity of cement w.r.t. aggregates will make the less paste available for aggregates and mobility of aggregates is restrained. Size of Aggregates o Surface area of aggregates depends on the size of aggregates. o Workability decreases with increase in the surface area of aggregates. o As the maximum size of coarse aggregate is increased, the surface area is decreased and the workability is improved. Shape of Aggregates o As the particles become round, the surface area is decreased and the workability is improved.  Properties of Fresh Concrete Factors Affecting Workability Surface Texture of Aggregates o With rough texture of aggregates, the surface area is more than the aggregates of same volume with smooth texture. o Thus concrete with smooth surfaces are more workable than with rough textured aggregates. Grading of Aggregates o As the fineness modulus of fine aggregates is increased, the amount of coarse aggregate should be decreased to maintain the workability level. o Increase in the proportion of coarse aggregate generally benefits workability. Use of admixtures o Some admixtures − such as water-reducing admixtures or superplasticizers, and air- entraining admixtures − improves workability. o They increases the workability of concrete even with low water/cement ratio.  Properties of Fresh Concrete (cont’d) Segregation Segregation of concrete is the separation of cement paste and aggregates of concrete from each other during handling and placement. Segregation also occurs due to over-vibration or compaction of concrete, in which cement paste comes to the top and aggregates settles at the bottom. There are two forms of segregation. i. Too Dry: The coarser particles tend to separate out since they tend to travel further along a slope or to settle more than finer particles. ii. Too Wet: Segregation, occurring particularly in wet mixes, is manifested by the separation of grout (cement plus water) from the mix. Some other factors causing segregation in concrete:- i. Transporting concrete mixes for long distances. ii. Poorly proportioned mix, where sufficient matrix is not there to bind the aggregates. iii. Dropping concrete from more than 1m. iv. Vibrating concrete for a long time.  Properties of Fresh Concrete (cont’d) Segregation How to minimize segregation in concrete:- i. Segregation can be controlled by maintaining proper proportioning the mix. ii. By peculiar handling, placing, transporting, compacting and finishing of concrete. iii. Adding air entraining agents, admixtures and pozzolanic materials in the mix segregation controlled to some extent.  Properties of Fresh Concrete (cont’d) Honeycombimg Segregation results in honey-combing , decrease in density and ultimate loss of strength. Honeycomb is a term used to describe a void on the exterior of a concrete face. When concrete is poured into the foundation forms it does not just flow in like water and fill up the forms to the top. If it is not vibrated properly it may leave voids called “honeycombing.” The exposed aggregate leaves a honeycomb look and hence the name.  Properties of Fresh Concrete (cont’d) Honeycombing Honeycombing is always an aesthetical problem. It reduce both the durability performance and the structural strength of the member. The heavier aggregate is left exposed with very little cement, sand and smaller aggregate that would normally surround the larger aggregate if it had been properly “settled.” This condition is more an indication of poor workmanship than it is a serious structural defect. What causes honey-combing ? o When compaction is not adequate to cause mortar to fill the voids between the coarse aggregates, or by holes and gaps in the formwork allowing some of the mortar to drain out of the concrete.  Properties of Fresh Concrete (cont’d) Bleeding Bleeding in concrete is sometimes referred as water gain. The Prime factor for bleeding in concrete is the high dosage of Water cement ratio. Higher water-cement ratio weakens concrete and leads to excessive bleeding. The bleeding in concrete is not harmful if the rate of evaporation of water is equal to the rate of bleeding. Normal bleeding is quite good, and it enhances the workability of concrete. However, excessive bleeding is a concern. How bleeding effects concrete stability:- o It increases the finishing time and produces laitance (soft slurry of cement paste) on top of concrete surface. o Thus, affects the quality of concrete, which is reduced strength, poor bonding between two successive layers, reduced wear strength. o The top surface may become too wet and if the water is trapped by superimposed concrete, thus resulting in porous, weak and non-durable concrete. o Concrete becomes permeable and loses its homogeneity.  Properties of Fresh Concrete (cont’d) Bleeding How the bleeding in concrete is controlled:- o Controlling the quantity of water o Providing finer grading of Fine Aggregate (FA) o Using finely ground cement o Performing suitable optimum compaction  Properties of Fresh Concrete (cont’d) Harshness Harshness is defined as the resistance offered by the freshly laid concrete to surface finishing. Harshness in concrete may be due to o Insufficient quantity of water o Lesser quantity of fines o Use of poorly graded aggregates o Lesser quantity of cement Harshness would result in porous concrete and poor surface finish.  Properties of Hardened Concrete (cont’d) Hardened Concrete Properties of hardened concrete include; i. Strength ii. Durability iii. Impermeability iv. Dimensional changes. v. Creep vi. Shrinkage  Properties of Hardened Concrete (cont’d) Strength After concrete has hardened, its resistance to bear loads is called its strength. Strength of concrete depends upon; o Grades of concrete o Water/cement ratio o Method of compaction o Time period elapsed Various measures of strength are; i. Compressive strength ii. Tensile strength iii. Flexure strength  Properties of Hardened Concrete (cont’d) Compressive Strength Compressive strength of concrete is the Strength of hardened concrete measured by the compression test. It is measured as the concrete's ability to resist loads which tend to compress it. This strength of concrete is determined by crushing cylindrical concrete specimens in compression testing machine (ASTM C39). o Sample diameter > 3 times maximum particle diameter o Sample height > 2 times diameter (correction is available in ASTM C39 if Height is < 2 times diameter ) o Bigger specimens have lower strength due to greater probability of weak element for failure to start.  Interface of aggregate and paste is weakest link. The compressive strength of concrete goes on increasing, even after 28 days of casting, though at a slower rate. The quantum of increase depends on the; o Grade and type of cement. o curing and environmental conditions.  Properties of Hardened Concrete (cont’d) Compressive Strength To comply with the strength requirements of a job specification, the following acceptance criteria apply: o The average of three consecutive tests ≥ the specified strength fc'. o No single strength test should fall below fc' by more than 500 psi (3.45MPa) or by more than 0.10fc' when fc' is more than 5000 psi (35 MPa). When strength test results indicates the failure of concrete may also be due to the testing procedure. o This is especially true if the fabrication, handling, curing and testing of the cylinders are not conducted in accordance with standard procedures.  Properties of Hardened Concrete (cont’d) Tensile Strength The Split-cylinder Test (ASTM C496) determines the load at which the concrete members may crack. : o The cylinder is placed on its side and tested in direct bearing. The tensile strength of concrete greatly affect the extent and size of cracking in structures. As the concrete is very weak in tension due to its brittle nature. o Hence. it is not expected to resist the direct tension. o Developing cracks when tensile forces exceed its tensile strength. Calculate the splitting tensile strength of the specimen as follows: o 𝑇 = 2𝑃/ 𝜋 𝐿𝐷  Properties of Hardened Concrete (cont’d) Tensile Strength  Properties of Hardened Concrete (cont’d) Flexure Strength Also known as modulus of rupture, bend strength or fracture strength. The Modulus of Rupture Test (ASTM C78); o 6”x6”x20” unreinforced concrete specimen. Identifies the amount of stress the structure can withstand to resists any bending failures. Expressed as the modulus of rupture (MR) in psi (MPa).  Properties of Hardened Concrete (cont’d) Flexure Strength After hundreds of tests, ACI developed an empirical expression for the modulus of rupture of concrete. 𝑓𝑟 = 7.5λ 𝑓𝑐 ′ λ = 1.0 for normal weight concrete. λ = 0.85 for sand light weight concrete. λ = 0.75 for all light weight concrete.  Properties of Hardened Concrete (cont’d) Stress-Strain Relationship Stress strain curve of concrete is a graphical representation of concrete behavior under load. The performance of concrete is controlled by the stress strain curve relationship and the type of stress to which the concrete is subjected in the structure. Note that the compressive strength, fc’, is taken as the highest compressive stress achieved on the curve. The elastic range of concrete stress strain curve continues up to 0.45fc’ (maximum concrete compressive strength). As water cement ratio increases compressive strength decreases. As water cement ratio increases compressive stiffness decreases. As compressive strength increases, the ductility decreases For normal weight concrete, o The maximum stress is realized at compressive strain ranges from 0.002 to 0.003. o The ACI Code specified that, a strain of 0.003 is maximum strain that concrete can reach  Properties of Hardened Concrete (cont’d) Modulus of Elasticity ACI 318 defines an empirical expression for calculating the modulus of elasticity of concrete (at small strains stress-strain is almost linear): 1.5 𝐸𝑐 = 33𝑤𝑐 𝑓𝑐 ′ (any concrete) 𝐸𝑐 = 57000 𝑓𝑐 ′ (normal weight concrete) A note on units: o 𝑤𝑐 = unit weigh of concrete 𝑙𝑏 𝑓𝑡 3 o 𝑓𝑐 ′= compressive strength (psi) o 𝐸𝑐 = modulus of elasticity (psi) Poisson’s Ratio Range: 0.11-0.21  Properties of Hardened Concrete (cont’d) Water Tightness (Impermeability) Impermeability is the resistance of the concrete to the flow of water through the pores. If there is excess water during concreting, the evaporation of surface water will leave a large no of continuous holes, making concrete relatively permeable. High permeability : o Caused by poor consolidation of fresh concrete. o Excess water (not utilized for hydration). o Allows water and chemical penetration. o Reduces durability. o Reduced alkali reactivity resistance. o Reduces freeze-thaw resistance. o Increases corrosion of bar.  Properties of Hardened Concrete (cont’d) Water Tightness (Impermeability) As water cement ratio increases from 0.4 to 0.7, the coefficient of permeability increases by a factor of 1000. w/c ratios < 0.44 is required for “ water tight” concrete; o such as tanks and dams. Concrete may be made impermeable by; o Using low water/cement ratio o Proper compaction o Use of dense and well graded aggregates o Continuous curing at low temperature conditions Finer cement particles faster rate of hydration faster the development of impermeable concrete  Properties of Hardened Concrete (cont’d) Durability Durability is the measure of resistance of concrete under the forces of environment such as weathering, chemical attack, fire and corrosion. Disintegration and decay in concrete may be due to the following reasons; o Use of unsound cement, which due to some delayed chemical reactions undergoes volume change after the concrete, has hardened. o Use of less durable aggregate, which may either react with cement, or may be reacted upon by atmospheric gases. o Entry of harmful gases and salts through excessive pores and voids present in unsound concrete, causing its disintegration. o Freezing and thawing of water sucked through the cracks and crevices (gaps), by capillary action causing its disintegration o Expansion and contraction, resulting from temperature changes or alternate wetting and drying.  Properties of Hardened Concrete (cont’d) Durability Concrete will remain durable if: o The cement paste structure is dense and of low permeability o Under extreme condition, it has entrained air to resist freeze-thaw cycle. o It is made with graded aggregate that are strong and inert o The ingredients in the mix contain minimum impurities such as alkalis, Chlorides, sulfates and silt. Durability of Concrete depends upon the following factors Cement content o Mix must be designed to ensure cohesion and prevent segregation and bleeding. If cement is reduced, then at fixed w/c ratio the workability will be reduced leading to inadequate compaction. However, if water is added to improve workability, water / cement ratio increases and resulting in highly permeable material. Compaction o The concrete as a whole contain voids can be caused by inadequate compaction. Usually it is being governed by the compaction equipments used, type of formworks, and density of the steelwork  Properties of Hardened Concrete (cont’d) Durability Curing o It is very important to permit proper strength development aid moisture retention and to ensure hydration process occur completely Cover o Thickness of concrete cover must follow the limits set in codes Permeability o It is considered the most important factor for durability. It can be noticed that higher permeability is usually caused by higher porosity. o Therefore, a proper curing, sufficient cement, proper compaction and suitable concrete cover could provide a low permeability concrete  Properties of Hardened Concrete (cont’d) Dimensional Changes Dimensional changes in concrete are caused due to 1. Shrinkage 2. Thermal changes, 3. Creep  Department of Urban & Infrastructure Technology Course on Engineering Materials (UE-104) NED University of Engineering &Technology, Karachi Course Instructor: Narmeen Tanweer (Digital lecture) Email: [email protected], ([email protected]) Department of Urban & Infrastructure Technology Lecture - 18 on Engineering Materials (UE-104) NED University of Engineering &Technology, Karachi Department of Urban & Infrastructure Technology  Properties of Hardened Concrete (cont’d) Dimensional Changes Shrinkage It is the contraction of a hardened concrete mixture due to the loss of capillary water. This shrinkage causes an increase in tensile stress, which may lead to cracking, internal warping, and external deflection, before the concrete is subjected to any kind of loading. The total shrinkage of concrete depends on the; o Constituents of concrete o Size of member o Environmental conditions For a given humidity and temperature, the total shrinkage of concrete is most influenced by; o The total amount of water present in concrete at the time of mixing o Cement content  Properties of Hardened Concrete (cont’d) Dimensional Changes Thermal Changes Hardened concrete expands and contracts by temperature changes. The coefficient of thermal expansion of concrete varies between 7x 10-6 to 12 x 10-6 per degree Celsius. The coefficient of thermal expansion of concrete depends upon; oNature of cement oNature of aggregates oCement content oRelative humidity oSize of sections To avoid thermal cracks, expansion and contraction joints are provided.  Properties of Hardened Concrete (cont’d) Dimensional Changes Creep The permanent dimensional changes that take place gradually due to sustained loading over many years is termed as creep. The creep of concrete depends upon; oConstituents of concrete oSize of the member oEnvironmental conditions oStress in concrete oAge of concrete at loading oDuration of loading  Operations of Concrete CONCRETING OPERATIONS To obtain good quality concrete, not only materials and their proportions are important. The concreting operations play an important role in over all strength performance of concrete. Concreting operations include; o Storage of material o Proportioning and batching o Mixing o Transporting o Placing o Compacting o Finishing o Curing  Operations of Concrete (cont’d) Storage of Material The storage of cement should ensure complete dry conditions and protection from moisture because cement is a finely ground material. It is easily affected by water and also atmospheric humidity. Aggregates should be stacked in such a way that its size and grading is not disturbed and it does not get mixed deleterious (harmful and injurious) material.  Operations of Concrete (cont’d) Batching and Proportioning Material should be measured properly by volume or by mass to satisfy the required mix proportions of the desired concrete grade. For volumetric measurements standard boxes in various sizes of 25, 50 liters are available. For mass measurements platform weighing or swing weigh batchers can be used. Each batch is prepared as per convenience of handling. While using volumetric batching care should be taken to compensate for bulking of sand. For important and large size jobs weigh batching should be used for better control on quality of concrete  Operations of Concrete (cont’d) Batching and Proportioning  Operations of Concrete (cont’d) Mixing of Concrete Thorough mixing of materials is essential for the production of uniform concrete. The mixing should ensure that the mass becomes homogeneous, uniform in color and consistency. There are two methods adopted for concrete: o Hand mixing o Machine mixing  Operations of Concrete (cont’d) Hand Mixing Hand mixing is adopted for small scale unimportant works. It is advisable to add 10% more cement. It should be done over an impervious (water tight) concrete. Spread out the measured quantity of aggregates in alternate layers. Pour dry cement on top of it and mix them with shovel until uniformity of color is achieved. This uniform mixture is spread and small depression is made with one forth addition of water. This operation is continued till such time a good uniform, homogeneous concrete is obtained. Remaining water is added at the end to get the required consistency. https://www.youtube.com/watch?v=l2D2V2MID18  Operations of Concrete (cont’d) Machine Mixing Machine mixing is efficient & also economical, for large quantity production. Usually batch mixers (single batch at a time), but sometimes continuous (conveyors automatically feed components into mixer). Spread out the measured quantity of aggregates in alternate layers. Usually start with 10% of the water in the mixer, then solids with 80% of the water, and then remaining water.  Operations of Concrete (cont’d) Transporting The mixed material should be transported to the place of deposit without wasting time i.e. before initial set of cement and without causing segregation and bleeding. Concrete can be transported manually by pans, wheelbarrows, chutes (descend), belt conveyors, lorries, truck mixers, buckets, cranes and concrete pumps according to quantity, site conditions and requirements. Maximum number of rotations and maximum time limit is set by ASTM C94.  Operations of Concrete (cont’d) Transporting  Operations of Concrete (cont’d) Placing Concrete can be deposited in; o Formwork o Natural subgrade (soil) o Hardened concrete base Before depositing concrete mix, a check of dimensions, shape, detail of reinforcement, cover to reinforcement, etc. should be thoroughly made. While depositing concrete mix on the hardened concrete base, it should be trimmed to the required shape and size, roughened, cleaned and moistened suitably. A coat of thick cement grout (water+ cement) should be scrubbed to the surface of the prepared base before depositing fresh concrete on it.  Operations of Concrete (cont’d) Placing In general, concrete is laid in horizontal layers of uniform thickness of about 150 to 500 mm. a. The concrete should be discharged as close as possible to its final position, preferably straight into the formwork; b. A substantial free-fall distance will encourage segregation and should be avoided; c. With deep pours, ensure that the layer of concrete below that being placed should not have set; to ensure full continuity between layers, and avoid cold joints and planes of weakness in the hardened concrete  Operations of Concrete (cont’d) Compacting Concrete is compacted for achieving maximum density. The compaction of concrete eliminates entrapped air resulting in denser concrete. The compaction of concrete completed before initial set. This method is used for small works. Sometimes is used where large reinforcement is used. Hand Compaction In hand compaction, the consistency of mix is maintained at higher-level. The thickness of concrete layer is maintained between 15-20 cm. Compaction is carried out manually in three ways; a. By rodding b. By tamping c. By ramming Operations of Concrete (cont’d)  Operations of Concrete (cont’d) Compacting Vibrators More effective as can be used for stiffer mixes with low W/C ratios. More economical as can be used with low Water/cement ratios. Leads to quicker compaction with lesser labor than hand compaction. It is advantageous for compaction o In congestion of reinforcement o Inaccessibility of the concrete in form wok. o Poor shape and texture aggregates are used. Increases the strength & durability of structures. Vibration should be used o To mould the concrete around embedment e.g. reinforcement. o To eliminate pockets of entrapped air. o It should not be used to move the concrete into place. o High-workability mixes should not be over vibrated – this may cause segregation.  Operations of Concrete (cont’d) Compacting Vibrators Depending upon the nature, size and quantity of reinforcement in the concrete member, a suitable type of vibrator can be used. Vibrators can be; a. Internal vibrator compacts concrete by direct contact. b. Form vibrator is attached to the formwork transfers vibrations to concrete through the formwork. c. Surface vibrator is placed on the top of the concrete and is suitable for thin layers of concrete.  Operations of Concrete (cont’d) Finishing Compacting or hand tamping of concrete may leave an uneven and rough surface. The surface of concrete is finished smooth or as per desired pattern using floats, trowel and screed. Where a smooth, hard, dense surface is desired, floating should be followed by steel troweling. Finishing the concrete surface; oEmbeds aggregate particles just beneath the surface. oRemoves slight imperfections, humps, and voids. oCompacts the mortar at the surface in preparation for additional finishing operations.  Operations of Concrete (cont’d) Finishing A slip-resistant surface can be produced by brooming before the concrete has thoroughly hardened. But it should be sufficiently hard to retain the scoring impression.  Operations of Concrete (cont’d) Curing Maintain moisture and temperature in the concrete to promote continued hydration and strength gain. Concrete should be cured in a suitable environment. o During the early stages of hardening. Drying in air generally reduces the strength. Curing keeps concrete saturated or as nearly saturated as possible. Curing prevents the loss of water from the water filled capillaries.  Note: The hydration can only take place only when the vapor pressure in the capillaries is sufficiently high.  Operations of Concrete (cont’d) Curing  Curing Methods Generally, the approach to curing is as follows: i. Maintain the presence of water in concrete. ii. Seal the surface so mix water can not escape. iii. Apply heat and additional moisture. Which method should you use? o Take into consideration: a. Size and shape of structure. b. Economic and speed of application. c. Weather conditions.  Operations of Concrete (cont’d) Curing  Curing Methods Following are the methods as follows; Plastic sheeting- Plastic sheets, or other similar material, form an effective barrier against water loss.  Operations of Concrete (cont’d) Curing  Curing Methods Ponding-Flat or near-flat surfaces such as floors, pavements, flat roofs and the like may be cured by ponding.  Operations of Concrete (cont’d) Curing  Curing Methods Wet coverings - Fabrics such as hessian, or materials such as sand, can be used like a ‘mulch’ to maintain water on the surface of the concrete.  Operations of Concrete (cont’d) Curing  Curing Methods Sprinkling or fog curing -Using a fine spray or fog of water can be an efficient method of supplying additional moisture for curing and, during hot weather, helps to reduce the temperature of the concrete.  Operations of Concrete (cont’d) Curing  Curing Methods Sprinkling or fog curing -Using a fine spray or fog of water can be an efficient method of supplying additional moisture for curing and, during hot weather, helps to reduce the temperature of the concrete.  Types of Concrete Concrete types include; o Regular concrete o High-strength concrete o High-performance concrete o Self-consolidating concretes o Shot-Crete o Pervious concrete o Stamped concrete o Air-entrained concrete  Types of Concrete (cont’d) Self-Consolidating Concrete No mechanical consolidation required. Fast placement Highly flow-able Flows to hard to reach locations Fills detailed surface (architectural details) Consolidates around reinforcement Easily pumped Achieved by; o Adding high range water reducer. o Increasing fines (either fine aggregates or cement) Measured by slump flow test.  Types of Concrete (cont’d) Shotcrete Relatively dry mix consolidated by impact force. Easily placed on vertical or overhead surfaces. Nozzle is held 1.5 – 5.0 feet away from surface. Steel or propylene fibers added for strength, ductility and toughness. Also called: o Sprayed concrete o Gunite  Types of Concrete (cont’d) High Strength Concrete Any concrete with an 𝑓𝑐′ ≥ 6000 𝑝𝑠𝑖 considered high strength. o Mixes with 𝑓𝑐′ up to 20,000 𝑝𝑠𝑖 are possible. Requires low water cement ratio. Requires super-plasticizers.  Types of Concrete (cont’d) Pervious Concrete A high porosity for concrete flatwork applications. Allows water from precipitation and other sources to pass Reducing the runoff and allowing groundwater recharge. Has little or no fine aggregate. Has enough cementitious paste to coat the coarse aggregates Preserving the interconnectivity of the voids. Pervious concrete is traditionally used in o Parking areas, o Areas with light traffic, o Residential streets, o Pedestrian walkways. Important application for sustainable construction.  Types of Concrete (cont’d) High Performance Concrete A concrete made with selected mix design; properly mixed, transported, placed, consolidated and cured. Gives excellent performance in the structure in Which it is placed, The environment to which it is exposed and The loads to which it will be subject for its design life. Used in structures requiring long service lives such as o Oil drilling platform, o Long span bridges and o Parking structures. Requires good construction practice. Requires good curing to deliver high performance.  Types of Concrete (cont’d) High Performance Concrete  Characteristics of high performance concrete: o High early strength o High strength o High modulus of elasticity o High abrasion resistance o High durability and long life in severe environments o Low permeability and diffusion o Resistance to chemical attack o High resistance to frost and deicer scaling damage o Toughness and impact resistance o Volume stability o Ease of placement o Compaction without segregation o Inhibition of bacterial and mold growth  Types of Concrete (cont’d) Stamped Concrete Stamped concrete is patterned and/or textured or Embossed to resemble brick, slate, flagstone, stone, tile, wood, and various other patterns and textures. Commonly used for o patios, o sidewalks, o driveways, o pool decks, and o interior flooring. Less expensive alternative to other authentic materials such as stone, slate or brick. Three procedures used in stamped concrete; o The addition of a base colour, o The addition of an accent colour, and o Stamping a pattern into the concrete. These procedures provide stamped concrete with a colour and shape similar to the natural building material. Longer lasting than paved stone, and still resembles the look.