Concretebroker

Blog

article title image

Published on 2/6/2019

Published by marketing@concretebroker.com.au

Lets talk about admixtures

What are the seven most used admixtures?


 

Seven Must-Use Concrete Admixtures (Additives) 

A List of Common Used Concrete Admixtures (Additives) 
 

BY JUAN RODRIGUEZ

Source : thebalancesmb.com

 

Admixtures are added to concrete batch immediately before or during mixing concrete. Concrete admixtures can improve concrete quality, manageability, acceleration, or retardation of setting time, among other properties that could be altered to get specific results. Many, not to say all, concrete mixes today contain one or more concrete admixtures that will help your pouring process driving down cost while increasing productivity, The cost of these admixtures will vary depending on the quantity and type of admixture being used. All of this will be added to the cubic yard/meter cost of concrete.
 

1. Concrete Admixtures: Set-Retarding

 

 

Concrete admixtures

Hisham Ibrahim / Getty Images

 

Set retarding concrete admixtures are used to delay the chemical reaction that takes place when the concrete starts the setting process. These types of concrete admixtures are commonly used to reduce the effect of high temperatures that could produce a faster initial setting of concrete. Set retarding admixtures are used in concrete pavement construction, allowing more time for finishing ​concrete pavements, reducing additional costs to place a new concrete batch plant on the job site and helps eliminate cold joints in concrete. Retarders can also be used to resist cracking due to form deflection that can occur when horizontal slabs are placed in sections. Most retarders also function as water reducers and may entrain some air in concrete.

 

2. Concrete Admixtures: Air-Entrainment

Air entrained concrete can increase the freeze-thaw durability of concrete. This type of admixture produces a more workable concrete than non-entrained concrete while reducing bleeding and segregation of fresh concrete. Improved resistance of concrete to severe frost action or freeze/thaw cycles. Other benefits from this admixture are:

  • High resistance to cycles of wetting and drying
  • High degree of workability
  • High degree of durability

The entrained air bubbles act as a physical buffer against the cracking caused by the stresses due to water volume augmentation in freezing temperatures. Air entrainers admixtures are compatible with almost all the concrete admixtures. Typically for every one percent of entrained air, compressive strength will be reduced by about five percent.

 

3. Water-Reducing Concrete Admixtures


Water-reducing admixtures are chemical products that when added to concrete can create a desired slump at a lower water-cement ratio than what it is normally designed. Water-reducing admixtures are used to obtain specific concrete strength using lower cement content. ​Lower cement contents result in lower CO2 emissions and energy usage per volume of concrete produced. With this type of admixture, concrete properties are improved and help place concrete under difficult conditions. Water reducers have been used primarily in bridge decks, low-slump concrete overlays, and patching concrete. Recent advancements in admixture technology have led to the development of mid-range water reducers.

 

4. Concrete Admixtures: Accelerating

 

Accelerating concrete admixtures are used to increase the rate of concrete strength development or to reduce concrete setting time. Calcium chloride could be named as the most common accelerator component; however, it could promote corrosion activity of steel reinforcement. Nonetheless, concrete best practices, such as proper consolidation, adequate cover and proper concrete mix design could prevent these corrosion issues. Accelerating admixtures are especially useful for modifying the properties of concrete in cold weather.

 

Concrete needs admixture

Getty Images/ Dorling Kindersley

 

 

5. Concrete Admixtures: Shrinkage Reducing

Shrinkage-reducing concrete admixtures are added to concrete during initial mixing. This type of admixture could reduce early and long-term drying shrinkage. Shrinkage reducing admixtures can be used in situations where shrinkage cracking could lead to durability problems or where large numbers of shrinkage joints are undesirable for economic or technical reasons. Shrinkage reducing admixtures can, in some cases, reduce strength development both at early and later ages.

 

6. Concrete Admixtures: Superplasticizers

The main purpose of using superplasticizers is to produce flowing concrete with a high slump in the range of seven to nine inches to be used in heavily reinforced structures and in placements where adequate consolidation by vibration cannot be readily achieved. The other major application is the production of ​high-strength concrete at w/c's ranging from 0.3 to 0.4. It has been found that for most types of cement, superplasticizer improves the workability of concrete. One problem associated with using a high range water reducer in concrete is slump loss. High workability concrete containing superplasticizer can be made with a high freeze-thaw resistance, but air content must be increased relative to concrete without superplasticizer.

 

7. Concrete Admixtures: Corrosion-Inhibiting

Corrosion-inhibiting admixtures fall into the specialty admixture category and are used to slow corrosion of reinforcing steel in concrete. Corrosion inhibitors can significantly reduce maintenance costs of reinforced concrete structures throughout a typical service life of 30 – 40 years. Other specialty admixtures include shrinkage-reducing admixtures and alkali-silica reactivity inhibitors. Corrosion-inhibiting admixtures have little effect on strength at later ages but may accelerate early strength development. Calcium nitrite based corrosion inhibitors do accelerate the setting times of concretes over a range of curing temperatures unless they are formulated with a set retarder to offset the accelerating effect.

 

Photo by : dmitry-ratushny

The weather plays a big part in which admixtures we use when pouring concrete

 

You might also like :

 

 

 

 

Article Image

WHAT ARE CHEMICAL ADMIXTURES?

Chemical admixtures are added to a concrete mix design during the batching process

Member Logo

TECHNOCRETE (1992) LTD

Technocrete

Technocrete (1992) Ltd. has been active in the building industry since 1992 and is engaged in a wide range of applications in the field of floors - concrete casting and polymeric materials, polished concrete, restoration and reinforcement of concrete, various coatings, concrete admixtures etc. The company's activities have adapted its experience and capabilities to various applications Industrial, decorative, constructional, etc. The company uses unique and well-known methods of work and provides advanced technological solutions in the fields in which it operates.The quality of materials, strict adherence to the use of standard materials only, the high level of employees, service, reliability and rich experience are those That switches Technocrete (1992) Ltd. as a leader in its field. Technocrete (1992) Ltd. is a pioneer in its certification by the Israeli Standards Institute in accordance with the requirements of the Israeli standard ISO 9002. Technocrete is successfully managing and executing large or small projects, complex as they may be, in all its fields of activity.

Member Logo

ECO BUILDING SYSTEMS CORP.

ThePerfectBlock

Eco Building Systems Corp (EBS) is the manufacturing company of The Perfect Block? (I.C.C.F. blocks) and Mobile I.C.C.F. manufacturing turn key plants for purchase. What is I.C.C.F blocks? I.C.C.F stands for "Insulated Composite Concrete Forms" It's a building block or form made from 100% recycled expanded polystyrene (EPS), EPS intercepted before it reaches the landfill. The EPS is what gives the ICCF block its outstanding insulating properties. The recycled EPS is ground into an aggregate and mixed with Portland cement, our propriety formula admixtures and water. The mix is molded into a hollow core form that you fill with concrete and steel (rebar) after the walls are up to create a structure that is 700% stronger than traditional wood frame and metal frame construction, fireproof (4-hour fire rating, ASTM tested at 2000*F), hurricane and tornado safe (ASTM tested at a design wind speed of 250mph), can be engineered up to a seismic 8.0 earthquake, mold and pest proof and when completed can exceed an R-45. The cured structure provides a permanent framework for a monolithic ?screen-grid? of reinforced concrete at 12? on center, vertically and horizontally, to form highly insulated stem walls, load-bearing walls, shear walls, non-load bearing walls, sound attenuation walls, lintels, perimeter walls, retaining walls, and many other components of a building. Added features of The Perfect Block? is its cost, which is highly competitive with all wall building materials and costing less than 2x6 wood framing and its sound attenuation capability provides a quiet living environment. All this in a ?green building? block that is fireproof and saves energy. For Green Builders & Developers: - LIGHTWEIGHT - Block as light as 30 Lbs. - LOW WASTE - As little as 2% waste reduces costs to the builder, and waste tonnage to the landfill, and potential damage to the environment - PRECISE DIMENSIONS - Clean & Even edges, ICCF block, that has perfect dimensions, is easier to build with and eliminates compounded errors by slight variations in block. The Perfect Block? Benefits for Builders: Engineered to be highly consistent with standard residential construction dimensions @ 4? lengths. Forms are monolithic and precision molded and require minimal shimming for plumb and level walls. Forms are stout and rigid and create strong straight walls requiring minimal pre-grout bracing. Forms are large enough to build walls rapidly but small enough for single person handling. Forms are easily cut with common carpentry tools, forms are easily cut for special angles and shapes. Forms? 12? on center cores allow for any 12? or greater cut block to be used in general construction minimizing leftover building waste. The Perfect Block? offers 4 types of building forms, ranging from a 6? thick block for small projects or interior walls to 10? 6? x 6? core forms for special interest applications in government, security, transportation, and disaster rebuilding. For all of us at Eco Building Systems, it?s not only about creating a disaster resistant building material that can help save lives or helping to reduce our clients? energy bills by 50% or more, but also about a committed belief in doing what we can to make this world a better place to live with fresher air and a lasting ecosystem. As the price of commodities continues to increase, it is a financial benefit to make our homes and buildings more energy efficient. Additionally, with the understanding that nearly two-thirds of our earth?s original forest cover is gone, it is evident that wood is not the sustainable choice for the future of our planet. We challenge all manufacturers in the U.S. and around the world to compare the short-term benefits of their current manufacturing materials and processes with the long-term environmental impact. We hope that other manufacturers will adopt a more sensible use of manufacturing materials and processes. Every day at EBS, we make every effort to develop new environmentally-friendly and alternative solutions.

 

 

 


Tags: accelerator admixture air entrainment low shrinkage retarder water reducer


This article was written by marketing@concretebroker.com.au all rights reserved. The views and opinions expressed in this article are those of the author(s) and do not necessarily reflect those of concretebroker.com