Tag Archives: admixtures

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


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.