How Can Air-Entrained Concrete Improve Workability?
How Can Air-Entrained Concrete Improve Workability?
One significant drawback of concrete is its vulnerability to damage from one or several freeze-thaw cycles when saturated or near-saturated. Concrete could not be utilized in pavements, dams, foundations, or other large uses without some admixture. Concrete, on the other hand, may be made frost-resistant by adding air-entraining admixtures.
The workability of new concrete is improved by air entrainment. The cement’s small bubbles operate as fine aggregates, reducing interactions between solid aggregates.
The improved workability necessitates the use of air entrainment admixtures even when freeze-thaw is not an issue. In general, air entrainment results in uniformly compressed concrete.
In general, air-entrained concrete is 10 to 20% weaker than non-air-entrained mixes. Excessive air reduces strength and freeze-thaw resistance.
How Can The Workability Of Concrete Be Reduced?
Supplementary cementitious materials are those that, in addition to cement, are employed to affect the characteristics of fresh concrete. As supplemental cementitious ingredients, fly ash, fibers, silica fume, and slag cement are employed.
Adding fly ash to concrete enhances its workability by lowering the amount of water required to achieve the same workability or slump value.
The use of steel or synthetic fibers in concrete affects its workability by making aggregate movement more difficult by diminishing the lubricating action of cement paste.
The workability of concrete is affected by the amount of silica fume present. When used at low replacement rates, silica fume increases workability, but, when used at greater replacement rates, it reduces workability.
When employed at a concentration of 2 to 3% by mass of cement, silica fume is utilized as a pumping aid for concrete.
How Does The Fineness Modulus Of Aggregate Affect The Strength And Workability Of Concrete?
The fineness modulus (FM) is important in establishing the proportions of fine and coarse particles when building concrete mixtures.
When it comes to concrete, the fineness modulus (FM) is one key factor to consider. The higher the FM, the coarser the aggregate. Generally, a lower FM results in more paste, making the concrete easier to finish.
However, FM does not define the grading curve, and different gradings could have similar FMs. This is why it is important to specify the FM when designing a concrete mix.
There are several reasons why specifying the FM is important. For one, a lower FM results in harder concrete that can last longer.
Additionally, a higher FM results in finer concrete that is easier to mix and finish. However, a too-fine aggregate can lead to weaker concrete more prone to cracking.
