Concrete Construction Methods & Equipment PDF

11/30/2022 CB 523 Methods and Equipment for Construction I CHAPTER CONCRETE CONSTRUCTION Dr. Mohamed Salem Nashwan Arab Academy for Science, Technology and Maritime Transport (AASTMT), Heliopolis, Cairo, Egypt [email protected]...

11/30/2022 CB 523 Methods and Equipment for Construction I CHAPTER CONCRETE CONSTRUCTION Dr. Mohamed Salem Nashwan Arab Academy for Science, Technology and Maritime Transport (AASTMT), Heliopolis, Cairo, Egypt [email protected] 1 1 Concrete Construction  Concrete Production  Introduction  Types of Concrete  Concrete Components  Batching and Mixing Concrete  Batching & mixing concrete on site  Batching & mixing concrete on batch plants  Estimating Mixer Production  Transporting & Pumping Concrete  Methods and Plant: Horizontal movement  Methods and Plant: Vertical movement  Pumping Concrete 2 2 1  11/30/2022 Concrete Construction  Placing and Compacting Concrete  Placing and compacting concrete  Vibration mechanism  Finishing and Curing  Finishing and curing  Hot weather Concreting  Cold Weather Concreting  Precast and prestressed Concrete 3 3 Concrete Production 4 4 2  11/30/2022 Introduction  Concrete is one of the most versatile, economical, and universally used construction material.  Hardened concrete must meet:  Design strength requirements, be uniform, watertight, durable, and wear-resistant.  Desirable properties of plastic concrete include:  workability and cohesiveness 5 5 Introduction Operations Performed in Constructing a Concrete Project: 1. Designing the concrete mix 2. Obtaining the raw materials 3. Storing and batching these ingredients 4. Mixing-central, transit, or local 5. Transporting of concrete 6. Forming in the structural design desired 7. Placing and compacting concrete 8. Finishing the surface 9. Curing concrete 10. Stripping or removing the forms 6 6 3  11/30/2022 Types of Concrete Concrete is classified into several categories according to its application and density: 1- Normal-weight concrete It has a unit weight from 140 to 160 lb/ft3 (2243–2563 kg/m3), depending on the mix design and type of aggregate used. Typical 28-day compressive strength ranges from 2000 to 4000 psi (13,790 – 27,580 kPa). 2- Structural lightweight concrete has a unit weight less than 120 lb/ft3 (1922 kg/m3), by using lightweight aggregates such as expanded shale, clay, slate, and slag. Typical 28-day compressive strength greater than 2500 psi (17,237 kPa). 7 7 Types of Concrete 3- Lightweight insulating concrete It has a unit weight from 15 to 90 lb/ft3 (240– 1442 kg/m3), by using perlite and vermiculite. Typical 28-day compressive strength from about 100 to 1000 psi (690–6895 kPa). As the name implies, such concrete is primarily utilized for its thermal insulating properties. In some cases, air voids introduced into the concrete mix or foam replace some or all the aggregate particles. 8 8 4  11/30/2022 Types of Concrete 4- Mass concrete  Its unit weight is usually similar to that of regular concrete.  It is used in a structure such as a dam in which the weight of the concrete provides most of the strength of the structure.  Thus, little or no reinforcing steel is used. 5- Heavy weight concrete  Has a unit weights from 180 to about 400 lb/ft3 (2884–6408 kg/m3).  It is made from heavy aggregates such as barite, magnetite, and steel punching;  It is used primarily for nuclear radiation shielding. 9 9 Types of Concrete 6- No-slump concrete  It has a slump of 1 in. (2.5 cm) or less.  Slump is a measure of concrete consistency obtained by placing concrete into a test cone following a standard test procedure (ASTM C143) and measuring the decrease in height (slump) of the sample when the cone is removed.  Applications of no-slump concrete include bedding for pipelines, concrete placed on inclined surfaces and runways (helipads) 10 10 5  11/30/2022 Types of Concrete 7- Refractory concrete It is suitable for high- temperature applications such as boilers and furnaces. The maximum allowable temperature for refractory concrete depends on the type of refractory aggregate used. 8- Precast concrete It has been cast into the desired shape prior to placement in a structure. 11 11 Types of Concrete 9- Architectural concrete  It is exposed to view and therefore utilizes special shapes, designs, or surface finishes to achieve the desired architectural effect.  White or colored cement may be used in these applications.  Surface textures may include exposed aggregates, raised patterns etc.  Architectural concrete panels are often precast and used for curtain walls and screens. 12 12 6  11/30/2022 Types of Concrete 10- Self Compacting Concrete Self-compacting concrete (SCC) is a special type of concrete which can be placed and consolidated under its own weight without any vibration effort due to its excellent deformability, and which at the same time is cohesive enough to be handled without segregation or bleeding. Test methods to determine workability of Self Compacting Concrete are: Slump flow test. V Funnel Test. L Box Test. U Box Test. Fill Box Test. 13 13 Types of Concrete 11- 3D Printing Concrete 3D printed concrete is a special mix of concrete, specifically prepared to flow with ease through the nozzle of the printing equipment. The performance requirements of 3DPC, includes the printability, fresh and hardened mechanical properties, and durability. It has higher requirements for rheology, hydration, and green strength than normal concrete. no coarse aggregate 14 14 7  11/30/2022 Concrete Components: Cement There are five principal types of Portland cement, classified by the American Society for Testing and Materials (ASTM) as Types I – V, used in construction. Type I (normal) Portland cement is a general-purpose cement suitable for all normal applications. Type II (modified) Portland cement provides better resistance to alkali attack and produces less heat of hydration than does Type I cement. It is suitable for use in structures such as large piers and drainage systems, where groundwater contains a moderate level of sulfate. Type III (high early strength) cement provides 190% of Type I strength after 1 day of curing. It also produces about 150% of the heat of hydration of normal cement during the first 7 days. It is used to permit early removal of forms and in cold-weather concreting. 15 15 Concrete Components: Cement Type IV (low heat) cement produces only 40–60% of the heat produced by Type I cement during the first 7 days. However, its strength is only 55% of that of normal cement after 7 days. It is produced for use in massive structures such as dams. Type V (sulfate-resistant) cement provides maximum resistance to alkali attack. However, its 7-day strength is only 75% of normal cement. It should be used where the concrete will be in contact with soil or water that contains a high sulfate concentration. ( Aggressieve Soil ) 16 16 8  11/30/2022 Concrete Components: Aggregates Aggregate is used in concrete to reduce the cost of the mix and to reduce shrinkage. Because aggregates make up 60–80% of concrete volume, their properties strongly influence the properties of the finished concrete. To produce quality concrete, each aggregate particle must be completely coated with cement paste and paste must fill all void spaces between aggregate particles. The quantity of cement paste required is reduced if the aggregate particle sizes are well distributed and the aggregate particles are rounded or cubical. Aggregates must be strong, resistant to freezing and thawing, chemically stable, and free of fine material that would affect the bonding of the cement paste to the aggregate. 17 17 Concrete Components: Water Water is required in the concrete mix for several purposes. Principal among these is to provide the moisture required for hydration of the cement to take place. Hydration is the chemical reaction between cement and water which produces hardened cement. The heat that is produced by this reaction is referred to as heat of hydration. The amount of water in a mix also affects the plasticity or workability of the plastic concrete. It has been found that the strength, water tightness, durability, and wear resistance of concrete are related to the water/cement ratio of the concrete mix. Water/cement ratios normally used range from about 0.40 to 0.70 by weight. In terms of water quality, almost any water suitable for drinking will be satisfactory as mix water. 18 18 9  11/30/2022 Concrete Components: Water Organic material in mix water tends to prevent the cement paste from bonding properly to aggregate surfaces. Alkalies or acids in mix water may react with the cement and interfere with hydration. Sea-water may be used for mixing concrete, but its use will usually result in concrete compressive strengths 10–20% lower than normal. The use of a lower water/cement ratio can compensate for this strength reduction. However, seawater should not be used for reinforced concrete where the steel will be in contact with the concrete. When water quality is in doubt, it is recommended that trial mixes be tested for setting time and 28-day strength. 19 19 Concrete Components: Additives A number of types of additives or admixtures are used in concrete. Some of the principal types of additives used are: air-entraining agents, water-reducing agents, retarders, accelerators, pozzolans, and workability agents. Air-entrained agents: It has significantly increased resistance to freezing and thawing as well as to scaling caused by the use of deicing chemicals. It also increases the workability of plastic concrete and the water tightness of hardened concrete. For these reasons, air-entrained concrete is widely used for pavements and other structures exposed to freezing and thawing. 20 20 10  11/30/2022 Concrete Components: Additives Water-reducing agents: It increases the slump or workability of a concrete mix. Thus, with a water-reducing agent the amount of water in the mix may be reduced without changing the concrete’s consistency. However, note that some water-reducing agents also act as retarders. Retarders slow the rate of hardening of concrete. Retarders: They are often used to offset the effect of high temperatures on setting time. They are also used to delay the setting of concrete when pumping concrete over long distances. Accelerators: They act in the opposite manner to retarders. That is, they decrease setting time and increase the early strength of concrete. Since the most common accelerator, calcium chloride, is corrosive to metal, it should not be used in concrete with embedded steel, aluminum, or galvanized steel. 21 21 Concrete Components: Additives Pozzolans: They are finely divided materials, such as fly ash, volcanic ash, and calcined shale, which are used to replace some of the cement in a concrete mix. Pozzolans are used to reduce the heat of hydration, increase the workability, and reduce the segregation of a mix. Workability agents or plasticizers: It increases the workability of a mix. However, air-entraining agents, water- reducing agents, pozzolans, and retarders will also increase the workability of a mix. 22 22 11  11/30/2022 Production of concrete  The construction operations involved in the production of concrete include: 1. Batching, 2. Mixing, 3. Transporting, 4. Placing, 5. Finishing, 6. Consolidating, and Curing. 23 23 Batching and Mixing Concrete 24 24 12  11/30/2022 Introduction  Batching (mix proportioning) is the process of measuring concrete mix ingredients and introducing them into the mixer. To produce concrete of uniform quality, the ingredients must be measured accurately for each batch.  The proportions of each material in the mixture affects the properties of the final hardened concrete. These proportions are best measured by weight. Measurement by volume is not as accurate but is suitable for minor projects.  Specifications generally require that materials be measured for individual batches within the following percentages of accuracy:  cementitious material ±1%,  aggregates ± 2%,  water ±1%, and  admixtures ± 3%. 25 25 Batching and Mixing Concrete on Site Control panel Hopper and Engine. Drum Wheel-mounted units Trailer-mounted units 26 26 13  11/30/2022 Batching and Mixing Concrete on Site Self Loading units 27 27 Batching and Mixing Concrete on Site The small construction mixer is often used on small construction projects where ready-mixed concrete is not available. Min required team consist of: (1) Supervisor (1) Operator (4) Materials loading 28 28 14  11/30/2022 Batching and Mixing Concrete on Site Loading the hopper  Batching for small construction mixers is accomplished by loading the required quantity of cement and aggregate directly into the hopper of the mixer (often by volume).  The hopper turns upside down into mixer, then, the material batched first is last out. Consequently, it is better to load the coarse aggregate first to push out other ingredients.  It is better to add the cement as a sandwich between The correct order of adding fine and coarse aggregates to prevent it to be blown the materials in the hopper away. is: Coarse aggregate,  Water is added by the mixer operator, and Cement for cement, such mixers is usually measured by the sack (50 kg). then fine aggregate. 29 29 Batching and Mixing Concrete on Site 30 30 15  11/30/2022 Batching and Mixing Concrete on Site  If bagged cement is used, the weights of sand and coarse aggregates should be adjusted to suit a whole of bags of cement per batch.  The batch quantities are determined based on the no. of bags added into the mixer as shown in the following example. 31 31 Batching and Mixing Concrete on Site  It is better to add ingredients by weight to assure consistency of batches for higher concrete quality.  For small jobs, ingredients are added by volume rather than weight. A box built on- site or a wheelbarrow is used to load the hopper. Wheelbarrows having the 2-3 cubic foot capacities are also available in the engineering units. 32 32 16  11/30/2022 Batching and Mixing Concrete on Site Water  The main job of the mixer driver is to add the right amount of water to each batch.  The aim is to control the concrete consistency.  To have good and consistent concrete, the mixer will be equipped with a water tank of dial gauge to measure the water.  The dial gauge is continuously calibrated to see whether it is right.  Recalibrate the water gauge at least once a week. 33 33 Batching and Mixing Concrete on Site Mixing and Discharging:  First make sure that the materials are properly fed into the mixer. The First Batch  With a clean mixer, some cement and sand from the first batch will stick to the sides and blades, and then the first batch will come out harsh and stony (short of sand and cement).  To account for this issue, the coarse aggregate weight is reduced to the half for the first batch only.  The weight of added water is adjusted in turn based on the weight of the added ingredients. 34 34 17  11/30/2022 Batching and Mixing Concrete on Site Mixing and Discharging:  Add part of the water few seconds before adding the other ingredients into the mixer. The rest of water is added gradually after adding the solid materials.  The mixing time will be as prescribed depending on the mixer capacity, e.g., a mixer of 1 m3 needs a mixing time of 1.5-2 min.  Concrete is mixed well when the appearance is uniform both in color and consistency. 35 35 Looking After the Weight Batcher & Mixer  Make sure that the mixer is level, check every few days. Otherwise, the concrete will not properly mixed.  Always check the fuel, oil, and water level before starting up the mixer.  Clean the drum out thoroughly after finishing concreting for the day. This is achieved by operating the drum for a mix of coarse aggregate and water for about 10 min.  Once a week check that the speed of the mixer drum complies with the manufacturers’ recommendations. This is done by counting for the number of times a marker of chalk on the drum passes a given point per minute. 36 36 18  11/30/2022 Batching and Mixing Concrete 37 37 Batching and Mixing Concrete For the previous example, 1 m3 = 7 bags ? = 3 bags 38 38 19  11/30/2022 Batching and Mixing Concrete in batch plants  Central batching plants that consist of separate aggregate and cement batching units are often used for servicing truck mixers and for feeding central mixing plants.  In such batching plants cement is usually handled in bulk.  The addition of water to the mix may be controlled by the batching plant or it may be accomplished by the mixer operator. Large central mix plants are used to supply concrete for mega projects such as dams, which require large quantities of concrete. The product they deliver is referred to as ready-mixed concrete. The usual procedure is to charge the mixer with aggregate, additives, and cement at a central batch plant, then add water to the mix when ready to begin mixing. 39 39 Batching and Mixing Concrete in batch plants  Central batching plants Portable plants, Stationary plants 40 40 20  11/30/2022 Main Equipment in Concrete Batch Plant 41 41 Ready Mix concrete process 42 42 21  11/30/2022 Batching and Mixing Equipment  Concrete mixer  Aggregate stockpiles  Aggregate bins and weight hopper  Belt conveyor  Cement silos  Water tanks  Admixture tanks  Control room  Ready mix trucks 43 43 Aggregate Stockpiles Aggregate bins and Weight hopper 44 44 22  11/30/2022 Aggregate stockpile, bins, weight hopper, and belt conveyor system Concrete mixer 45 45 Pipes system to transmit cement from cement weight hopper into the mixer Cement silos Control Room Ready Mix Truck 46 46 23  11/30/2022 Advantages of Ready Mixed Concrete  Quality of concrete  Speed of construction  Elimination of Material Procurement Requirements and Storage Hassles  Saving in labor requirement  Reduction in wastage.  Improved life cycle cost  RMC is eco-friendly 47 47 Truck mixers or transit mix trucks Truck mixers or transit mix trucks are truck-mounted concrete mixers capable of mixing and transporting concrete. Truck mixers are also capable of operating as agitator trucks for transporting plastic concrete from a central mix plant. Standard Truck Mixers capacity ranges from 6 cu yd (4.6 m3) to over 15 cu yd (11.5 m3). Concrete in Truck Mixers should be discharged within 1.5h after the start of mixing. 48 48 24  11/30/2022 Estimating Mixer Production After a concrete mix design has been established, the volume of plastic concrete produced by the mix may be calculated by the absolute-volume method. In this method the volume of one batch is calculated by summing up the absolute volume of all mix components.  The absolute volume of each component may be found as follows: 49 49 Estimating Mixer Production When calculating the absolute volume of aggregate using Equation 7–1, aggregate weight must be based on the saturated, surface-dry (SSD) condition. Such aggregate will neither add nor subtract water from the mix. If aggregate contains free water, a correction must be made in the quantity of water to be added to the mix. Saturated surface dry (SSD) condition is defined as the condition of an aggregate in which the surfaces of the particles are "dry" (i.e., surface adsorption would no longer take place), but the inter-particle voids are saturated with water. In this condition aggregates will not affect the free water content of a composite material. 50 50 25  11/30/2022 Example (a) Calculate the volume of plastic concrete that will be produced by the mix design given in the table. (b) Determine the actual weight of each component to be added if the sand contains 5% excess moisture and the gravel contains 2% excess moisture. (c) Determine the weight of each component required to make a three-bag mix (each 94 lb) and the mix volume. 51 51 Example 52 52 26  11/30/2022 Example 53 53 Example Thank You ! 54 54 27