Water reducing admixtures (WRA) – Properties and Benefits

Usage of water reducing admixture is classified as Type A in ASTM C 494. WRA reduces the water usage by 5% to 12% but still maintains the consistency of concrete at the required levels. So it affects the fresh properties of concrete and consistency as measured by the slump. The use of WRA may accelerate or retard the initial setting time of concrete. If it retards the setting time it is classified as “retarding effect WRA”.

Two common chemicals used as WRA are lignosulfonates and hydrocarboxylic (HC) acids. Lignosulfonates have a little edge as they require less water compared to HC acids. Also the problem of rapid bleeding is an issues faced while using hydrocarboxylic acids as water reducing admixture in concrete.

Depending on the type of WRA used the slump in concrete varies. Typical dosage rate is based upon the cementitious material content (mm/quintal). Refer to the graph below to determine the influence of HRA dosage on slump. below illustrates the influence of dosage of Lignosulfonates and HC acid on slump. Apparently HC acids generate more slump compared to lignosulfonates when dosage is constant.


Benefits of water reducing admixtures in Concrete.

  • Primarily used in hot weather to enable better concrete pumping, placing and tremie.
  • Higher initial concrete compressive strength
  • Makes concrete less permeable
  • Increases durability



Just before or during the process of mixing concrete add mixtures are often added. Admixtures are added as means to improve quality, acceleration, manageability, or retardation. Most of concrete mixes currently have one or more concrete admixtures. Concrete admixtures serve different purposes which may include the following;

Concrete admixtures used to set-retarding- the set retarding concrete admixtures are often used to inhibit the chemical reaction which occurs when the concrete starts the setting process. The main use of these this type of concrete admixture is often to bring down the effects of high temperatures which may bring about a speedier setting of concrete. This type of admixtures is most commonly used in making pavements. They are used in pavement construction to give more time to finish concrete pavements. This reduces anymore costs that would have been incurred to put up a new concrete batch plant on the construction site; it also eliminates cold joints in concrete.

Retarders also can be used to help resist cracking caused by form deflection which occurs when horizontal slaps are put in sections. Retarders can also be used as water reducers; they also help to entrain some air in the concrete.

Concrete admixtures for air entrainment- the fresh-thaw durability of concrete can be increased by air entrained concrete. Air entrained admixture often produces an easy to use concrete compared to concrete that has no air entrained admixture added to.  Air-entrained admixture also helps to reduce bleeding and segregation of fresh concrete. Another advantage of using air-entrained admixture on concrete is the fact that it helps improves the resistance of concrete on severe frost action or freeze thaw cycles. Air-entrained admixture also brings about high resistance to cycles of wetting and drying, high degree of workability, and high degree of durability.

Concrete admixtures for water reducing purposes-water reducing admixtures are often used to serve the purpose of lowering the water content in a cement ration. They are often used to bring about desired concrete strength by use of lower cement content. This type of admixture helps improve concrete properties by enhancing the placement of concrete under difficult conditions. Some of the places where water reducing admixtures have been used is in the construction of bridge decks, low –slump concrete overlays, and in patching concrete.

Accelerating concrete admixtures- they are used to serve the purpose of speeding the rate of concrete strength development. They also serve the purpose of reducing concrete setting time. Calcium chloride is one notable ingredient of this admixture although it could also increase the corrosion of steel reinforcement. This can be avoided by doing proper consolidation, using enough cover, and also practicing proper concrete mix design. Accelerating admixtures often come in handy when modifying the properties of concrete in cold weather.

Shrink reducing concrete admixturesthey are often added to concrete during the early stages of concrete mixing. The main purpose of this admixture is to reduce early and long term drying shrinkage. These admixtures serve the purpose of alleviating problems that often result from shrinkage cracking thus ensuring the durability of structures. Shrinkage reducing admixtures could also reduce strength development.

Super plasticizers concrete admixtures-these admixtures are majorly used for the production of flowing concrete with very high slump. They are often used in heavily reinforced structures and also in placement s where enough consolidation cannot be gotten easily by vibration. They are also used in the production of high strength concrete at W/C’S that ranges from .03 to 0.4. Super plasticizer when used with most types of cements improves the workability of concretes.

Corrosion inhibiting concrete admixtures-they are classified into the specialty admixture ( Corrosion Inhabiting ) category. They are used to slow the corrosion of reinforcing steel in concrete. Using them in construction always helps to reduce the maintenance costs of reinforced concrete structures.



How To Prevent Flood Water From Damaging Your Building

water-damage-imageFlash flooding often causes extensive damage to property and many people also lose their lives as a result of flooding. An example of such floods is the worst one that occurred in India on June 2013 in the state of Uttarakhand that caused landslides killing many people [Ref]. The Uttarakhand government provided figures that showed more than 5,700 people had died from the flooding. The floods caused extensive damage to buildings, bridges and roads trapping about 1000 pilgrims that had visited the Hindu Chota Char Dam pilgrimage sites. Floods are natural disasters that can occur anywhere and therefore it is advisable as an individual to take precautionary measures that will help prevent your building from being damaged by flooding.

It is wise for all homeowners to check all the key areas to the exterior of their buildings on a regular basis after flooding has occurred. This way one may be able to see the structural damage that the flood could have caused to the building such as widened cracks which if left unrepaired could bring the whole building down. Flood water often enters buildings through cracks on the walls thereby damaging such buildings. Buildings with cracks on the walls pose a risk of structural damage and even collapse during flooding.  It is for this reason that it is important that regular checks be conducted on buildings and if cracks are seen then they should be repaired at once. These in one way or another will limit potential damage to such buildings in times of flooding.

Recommended : Waterproofing Treatment Products

In order to prevent damage to buildings caused flooding there are steps that can be followed which include the following;

  • Conducting good exterior maintenance will help limit the amount of water that can seep through masonry walls in times of flooding. Regular checking of changes in the line or appearance of a roof ridge done from a distance may help you notice any abnormality.
  • Buckled walls identified by appearance of horizontal cracking or areas appearing to have moved out of vertical alignment should be repaired before flooding to minimize their total collapse in the event that flooding occurs.
  • Vertical to diagonal cracks on walls should also be repaired in time before it is too late. These if left unattended often make the wall weak and also allow flood water to easily get into the building.
  • If you notice deep scouring that lead to exposed foundations it wise to repair them to make the building strong.
  • Cracks bigger than 2 mm should also be repaired to avoid any further cracking.

If you notice any of the above changes on the building then it is time for you to contact building experts to come and do repairs on the building.


This video showcases Dura Build Care’s use of poly-grout technology to seal cracks and pores in concrete structures to effectively waterproof them. First of all, DURAGEL which is a water reactive poly-grout is taken in a testing container,   and then water is added to test the efficiency of DURAGEL.

As you can see the reaction starts and it start swelling up, in real life application this can be used to seal pores & cracks which are present inside the concrete.

As the reaction starts the contents begin to swell. Generally its swells to around 8 to 10 times of the amount of Duragel liquid that has been taken.

We let the reaction complete at its own pace, which is very quick as you can see it. As it settles it becomes more rubberized. When  pressed, it is no longer compressible. It has now solidified, which means that the cracks in pores are sealed now.

Other methods  used to seal contrete cracks include:

Integral water proofing is a method that keeps water out of the concrete due to capillary action or hydrostatic head, forming a crystal which blocks the pores.

Polymer modified bituminous coating is a method that makes use of bitumen, which moves with the concrete and doesn’t allow the water to concentrate inside the structure.

Silicone water proofing is rain coating applied on the outer walls of the concrete, making it water repelling.

Crystalline water proof system is a system that uses advanced ranges of crystalline water proofs to reduce the pore size by forming non-soluble crystals within the concrete microstructure.

Cementitious Polymer Coating is coating used to treat the mother concrete substrate making sure that the use of any foreign materials is avoided due to its cement related properties.

Latest Waterproofing Products And Techniques For Concrete Buildings

It is a proven fact that water can cause immense harm to a concrete building. Buildings may decay and their strength may deteriorate due to water. The materials, especially concrete, used for constructing buildings may lose their strength and have shorter lifespan because moisture gets absorbed by concrete through capillary action. Further, there may be hydrostatic pressure on the concrete mass. When this pressure is on one side of the concrete structure, moisture may travel through the mass and connect both the sides. So, it has become imperative that appropriate waterproofing technologies have to be adopted for preventing these damages.

Though highly accurate water-cement ratio may make concrete impermeable, builders find it practically impossible to maintain this ratio. That is why manufacturers operating in the building materials industry do a lot of research to find alternate products for surmounting this problem. But, you should not consider the price factor alone while choosing these products. By doing so, you may compromise on the quality of these waterproofing products. You should therefore know the materials that are available in the market, how construction chemical manufacturer can fulfill your requirements.

Latest waterproofing techniques or products can be classified as permeability reducers, hydrophobic or water repellents, etc. As the name suggests, permeability reducers fill the pores and you have a few types in them. They are very fine particulate matters, air entraining and workability admixtures and accelerators.

Some of the admixtures in powdered form that are available in the market are Ground Sand, powdered limestone, bentonite, pumice, fluoro silicates etc. If you choose those admixtures that have a pozzolanic character also, the cement gel you use for construction may get densified also.

In the case of plasticizers and workability agents, they are capable of avoiding large voids. They do not require use of high water also. They give better dispersion to cement and reduce water’s surface tension. Workability can be improved even by using air-entraining agents.

Experts do not consider accelerators as waterproofers in the strictest sense.

So, you must opt for those products that have permeability reducing capabilities and some pozzolanic quality also. You can opt for plasticizers also but, most of them contain sulphate ions that can be harmful. So, when you intend to buy them, you should inquire with the manufacturers and know the right amount of these ions present in the products. Only if you are sure that they are within tolerable limits, you should use them.

Water-repellents can also be used in waterproofing techniques. These products can impart electrostatic charges into the walls and so, they do not allow water to get into the concrete mass. Soaps, Stearate emulsion, a few petroleum products, Butyl, etc. belong to this category.

A lot of research has been happening in this area and many advancements are taking place as well. There are a number of new and eco-friendly products that not only provide the right solutions to the problem but, can also protect the environment. Manufacturers are coming out with products that are free from Volatile Organic Compounds that are harmful for the environment and also the human health.