CARING FOR CONCRETE slideshow
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This document discusses caring for concrete in cold and hot weather conditions. In cold weather, concrete must be protected from freezing for the first 24 hours to prevent damage. Methods like insulating blankets and polyethylene sheeting can retain heat and moisture. In hot weather, cooling aggregates and water and protecting poured surfaces is important. A higher water-cement ratio may be needed to prevent cracking from rapid setting and moisture loss. Proper curing and protecting concrete from temperature extremes is key to ensuring strength and quality.
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2) The departments within CDGI including laboratories, pollution control, product development and training.
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4) Key aspects of melting, forming, and annealing glass as well as testing procedures to ensure quality.
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ADVANCED TECHNIQUES IN CASTING DEFECTS AND REJECTION ANALYSIS: A STUDY IN AN ...
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Hot weather concreting refers to concrete placement when ambient temperatures exceed 40°C. High temperatures can accelerate cement hydration, increase water demand, and cause cracking due to rapid evaporation. Proper precautions include controlling ingredient temperatures, using minimum cement and water, and continuous curing. Placement should be scheduled for evenings and concrete covered immediately to reduce temperature rise and evaporation. Hot weather concreting requires careful control and curing to produce durable concrete.
Concrete in hot weather
This document discusses mix design considerations for concrete placed in hot weather. Key factors that affect concrete quality in hot weather include high ambient temperature, concrete temperature, low relative humidity, and solar radiation. These conditions can increase water demand, accelerate setting and slump loss, and increase cracking risks. The document recommends ways to control these risks, including cooling concrete ingredients, using admixtures to reduce water demand and extend workability, limiting cement content, and promptly placing and curing concrete. Trial batches should be used to establish suitable mix designs for local hot weather conditions.
Heat of Hydration in Mass Concrete
This document discusses mass concrete and factors that affect heat of hydration (HOH) generation and temperature rise during curing. Mass concrete is defined as any concrete placement thick enough to require measures to control cracking from HOH. Factors like cement content, placement temperature, and insulation affect the maximum temperature (Tmax) and temperature differential (ΔT). Using additives like fly ash or slag cement can reduce Tmax and cracking risks by lowering HOH. The document provides guidelines for mix designs and construction practices to control Tmax and ΔT for different aggregate types used in Saudi Arabia.
12p.pdf
Hot weather is defined as any period with high temperatures that require special precautions for concrete. High temperatures can cause rapid drying of concrete and accelerated setting, potentially leading to cracking. It is important to account for hot weather conditions when planning concrete projects, as high heat can increase water demand and accelerate setting. To successfully place concrete during hot weather, the key is recognizing affecting factors and minimizing their impacts, such as modifying mix designs, reducing cement content, limiting water addition, starting finishing quickly, and adequately curing the concrete.
concrete curing.ppt
The document discusses various methods for curing concrete, including maintaining moisture through ponding, immersion, fogging, or wet coverings. It also discusses methods that reduce moisture loss such as using impervious paper, plastic sheets, or curing compounds. Accelerated curing methods that provide additional heat and moisture like steam curing are also described. Proper curing is important for ensuring hydration of cement and allowing concrete to reach its desired strength and durability properties. Inadequate curing can result in reduced strength and durability in the surface layers of concrete.
Mass Foundations Concreting
This Presentation Covers and creates the awareness on understanding the mass concreting and its temperature effects during Concreting. Data compiled from varous papers and presentations.
curing.ppt
Curing concrete involves maintaining moisture and temperature conditions to allow hydration of cement to occur. It prevents premature drying out which could limit strength development and durability. Effective curing methods include ponding, fogging, wet coverings, impervious sheets, membrane compounds and steam curing. Curing should continue until the concrete reaches adequate strength, typically a minimum of 7 days, and longer periods improve concrete properties. Temperature, cement type, element size and exposure conditions influence curing needs. Inadequate curing can limit strength and durability within 30-50mm of the surface.
Hot weather concreting.pptx
Hot weather concreting refers to placing concrete when atmospheric temperatures exceed 40°C. Problems that can occur include rapid cement hydration, quick setting, early stiffening, rapid evaporation of mixing water, greater plastic shrinkage, less time for finishing, reduced relative humidity, absorption of water from the concrete by the sub grade and formwork, and difficulty providing continuous curing. Special methods are required for making, placing, and compacting concrete during hot weather to address these issues.
Curing & prefabrication of concrete structures@hemadurgarao-IIIT Nuzvid
Curing concrete is an important process to ensure proper hydration of cement and development of strength. There are various curing methods like immersion, ponding, spraying, wet covering, and membrane curing. Membrane curing uses plastic sheeting or compounds to seal in moisture. Steam curing at higher temperatures accelerates strength gain but can cause retrogression of strength with fast hydration. Prefabricated construction involves dividing construction into standardized parts that are mass produced in a plant and assembled on site. This allows for parallel production, reduced time, and standardization.
Information soil bricks/Best Brick Production Methods
Manufacture of bricks is generally a good business. a successful brick manufacturing business has three main items:1. the correct type of clay soil should be available in quantities required .2. a good production factory consisting of good quality robust machinery and an energy efficient drying and firing process. 3- a good market for the products. besides the above sound technical and managerial ability to manage the production process is essential. after sales support for the machinery is another asset .*QUALITY IS A TRADITION AT HAMGAM SANAT*.
Dayton Superior and Cold Weather Chemicals
Cold weather is defined as temperatures below 40°F during the curing period. Concrete must reach minimum compressive strengths of 500 psi to resist freeze/thaw when fresh or 3500 psi for repeated cycles. Concrete repair can be done in cold weather by using enclosures, heating methods, and preconditioning materials. Heaters used include direct-fired, indirect-fired, and hydronic. Chemicals and admixtures are available from Dayton Superior to aid in cold weather concreting, curing, repairs, and other applications. These products allow concrete work down to temperatures of -15°F and maintain workability at lower temperatures.
Similar to CARING FOR CONCRETE slideshow (20)
Mike Murray Concrete Solutions Inc cold weather mark mead
Mike Murray Concrete Solutions Inc cold weather mark mead
Curing & prefabrication of concrete structures@hemadurgarao-IIIT Nuzvid
Curing & prefabrication of concrete structures@hemadurgarao-IIIT Nuzvid
Information soil bricks/Best Brick Production Methods
Information soil bricks/Best Brick Production Methods
CARING FOR CONCRETE slideshow
- 1. CARING FOR CONCRETE COLD AND HOT WEATHER CONDITIONS Code Precast Products, Inc.
- 2. Talking Points Before pour actions Segregation in concrete After pour actions Cold weather caring Hot weather caring Curing process after pour
- 3. Before the Pour Cleanliness. Not only the area around the pour, but the forms themselves. Buildup of excess oil, concrete, and dirt not only makes it harder to strip, but leaves the finished product looking bad. Make sure form oil is applied. All inserts, anchors, knockouts, cups, or any other extra product are properly secured and in the correct spot. Rebar is in the form. Vibrator is working. Make sure someone who knows how to finish is finishing the product.
- 5. Segregation in Concrete Segregation occurs when aggregates separate themselves from the rest of the concrete. Usually occurs when too much water is added, causing coarse aggregates to sink and separate. After pouring, water and admixtures will leak from the form, greatly reducing strength in the finished product. Water may also rise to the top, causing a weaker finished product (higher w/c ratio). If segregation occurs, stop the truck and mix. If there is still segregation, have the truck go back and add aggregates to even out the mix. If there is still segregation, contact myself or Ed about dumping the mix.
- 6. Segregation in Concrete Segregation can greatly reduce the strength in our finished product. It also leads to honeycomb and sand lines, causing extra labor to fix the finished product. Segregation can also be caused by over vibrating. If the mix is good and flows well, a dead blow hammer will suffice in a vibrating method. Should a vibrator be needed, make sure the person vibrating knows what they are doing.
- 7. After Pour Actions After the pour, regardless of temperature, cover the product. Clean all tools and materials used for the pour. Should steel trough finish or stamping be needed, set a reminder. Keep product covered until time to strip, regardless of temperature. Sometimes, loosening forms while the product is still covered is acceptable in certain temperatures.
- 8. Cold Weather Caring According to ACI 306, “A period when for more than three successive days the average daily air temperature drops below 40 degrees and stays below 50 degrees for more than one half of any 24 hour period.” During cold weather, it may be necessary to heat the water or aggregates. Using hot cement is not an effective method. Colder temperatures will extend the time needed to reach initial set. To combat, more cement or accelerator can be used. Supplementary heat, enclosures, or curing blankets may be used as well.
- 9. Cold Weather Caring When temperatures drop to less than 40 degrees, freshly poured concrete is susceptible to becoming compromised. All concrete must be protected from freezing until it has reached a minimum strength of 500 pounds per square inch (psi), which typically happens within the first 24 hours. If concrete freezes while it is still fresh or before it has developed sufficient strength to resist the expansive forces associated with the freezing water, ice formation results in the disruption of the cement paste matrix causing an irreparable loss in strength.
- 10. Cold Weather Caring Concrete should not be allowed to freeze during the first 24 hours after it has been poured. Cement hydration is an exothermic reaction, meaning it releases energy by light or heat. Concrete mixture produces some heat, so protecting that heat from escaping is key. The use of polyethylene sheeting or insulating blankets are necessary to keeping that heat and retaining moisture.
- 11. Hot Weather Care When the temperature of freshly mixed concrete reaches near 77 degrees, adverse site conditions can impact its quality. Ambient temperatures above 90 degrees and the lack of a protected environment (a building) can relate to difficult in producing quality concrete. Cooling aggregates and water added to the mixture is vital. Protecting the surfaces of which concrete is being poured. A higher water to cement ratio is necessary for flow ability and faster set time.
- 12. Hot Weather Care 20 degrees in temperature will reduce the setting time of a mixture by as much as 50%. As the concrete temperature increases the setting time is further reduced. Increased rate of cement hydration at elevated temperatures are the main causes of problems associated with the hot weather. Cracking, even with a good w/c ratio, can happen in extreme hot weather. Drying Cracking occurs when water is added to a mix design without adjusting the amount of cement. Thermal Cracking occurs when temperatures drop and increase day to day.
- 13. Hot Weather Care – Preventing Moisture Loss Moisture loss is the leading cause of decreased strength is concrete. High temperatures in concrete and outside, low humidity, solar radiation, and wind can all cause moisture loss. The leaves less water in the w/c ratio that called for, therefore not allowing the proper amount to hydrate the cement.