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The main factor that controls abrasion resistance of concrete is the concrete's compressive strength. The higher the concrete surface strength the better the resistance of concrete against abrasion.
Apart from concrete strength, there are several factors such as the use of w/cm less than 0.45, the use of dry shakes and toppings, finishing techniques, and adequate curing that influence abrasion resistance of concrete and hence they need to be considered.
It should be known that proper inspection and use of power trowel finish during construction would help to increase surface resistance. Abrasion resistance is defined as the ability of the concrete surface to resist wearing forces due to rolling steel wheels, scratching by pallet and stillage legs, forklift truck tines, or even impact from falling objects.
7 Factors Affecting Abrasion Resistance of Concrete Surface
1. Factors Impacting Concrete Strength
Factors that directly affect concrete strength would influence concrete abrasion resistance as well. For example, low water to cement ratio, low slump value, well-graded aggregate, and air content.
1.1 W/C Ratio
Low to moderately w/c ratio ensure the decrease of free water in concrete. This improves concrete compactness and reduces permeability which consequently improves concrete strength and hence abrasion resistance.
W/C ratio can be decreased by using water-reducing admixtures, mixture proportions to reduce bleeding, the timing of finishing operations that avoid the addition of water during troweling, and vacuum dewatering.
1.2 Well-Graded Aggregate
The use of well-graded fine and coarse aggregate can optimize workability and minimize water content. This would improve concrete strength considerably.
1.3 Air Content
Not only does air content leads to the reduction of concrete strength but also contributes to concrete surface delamination and blistering especially when finishing works are times improperly.
So, air content should not be considered for concrete when abrasion resistance is required unless special considerations are followed. For instance, hard troweling of the surface should not be done on concrete having a total air content greater than 3 percent.
2. Proper Curing Procedure
Proper curing procedure is a major element in the construction of floor surfaces with satisfactory abrasion resistance. This is because it contributes to increased concrete strength and toughness.
These characteristics are the most important factors for ensuring resistance to surface abrasion. Keeping concrete continuously wet is a desired curing regime for the majority of concrete floors, as per American concrete institute.
3. Use of Supplementary Cementitious Materials
It is demonstrated that, if properly and adequately cured, polymer concrete, polymer-impregnated concrete, epoxy concrete, calcium aluminate cement, and calcium sulfoaluminate cement provide exceptional abrasion resistance.
4. Two-course Floors
The use of two-course floors using high strength topping in excess of 40MPa would provide excellent abrasion resistance. Nonetheless, this type of floor is more expensive compared with other conventional floors. It should be known that the two-course floor is used when abrasion and impact resistance is needed.
5. Special Concrete Aggregates
Type of aggregate is among factors that affect abrasion resistance of concrete. The use of hard and tough aggregates can increase the life span of floors, such as warehouse floors, that subjected to severe abrasion by steel or hard rubber-wheeled traffic.
Abrasion-resistant aggregates are commonly applied as dry shakes or in high-strength, bonded toppings. Dry shakes are a mixture of aggregates with cement which is applied dry to the concrete surface during finishing operations.
When abrasion resistance is a fundamental concern, then high-quality quartz, traprock, emery aggregate is recommended to be used because such aggregate improves the strength of concrete surface. The abrasion resistance of concrete surface can be further increased by using metallic aggregates with cement.
Finally, it is not recommended to use light-weight aggregate for high abrasion resistance purposes. And the abrasion resistance of concrete surface containing recycled aggregate is dependent on the compressive strength and type of the aggregate.
6. Proper Finishing Procedures
The use of proper finishing time and procedure is another factor that influences abrasion resistance of concrete. Floating and troweling operations begin when the surface sheen of concrete is lost.
So, finishing works should be delayed until concrete surface reach this point. The delay period is based on temperature, humidity, air movement, and supplementary cementitious materials used.
Finally, standing water should never be worked into concrete surfaces because it reduces the compressive strength of the surface paste.
7. Vacuum Dewatering
Vacuum dewatering reduces w/cm ratio which leads to increase concrete strength and abrasion resistance, but one should be aware that the quality of the finished surface is still highly dependent on the timing of finishing.