Why We measure concrete in m³ and asphalt in metric tons ?
- Thread starter Gowtham Kayala
- Start date
mohammad.amtiaz
Newbie
HockeyPuck
Active Member
This is a great question.
A concrete-based element is designed to be a specific shape, such as a retaining wall footing - It is Length x Width x Height. Concrete does not have appreciable material variability or voids. In it's final shape, it can be readily measured, and for all practical purposes is 100% dense.
You could argue that, for an asphalt driveway let's say, you specify it to be 50mm thick x Length x Width, so it could be quantified similarly, right? There are 2 primary reason why we measure asphalt pavement by weight:
1. The variability of the in-place material. Compaction is required to achieve the final shape, and depending on the level of compactive effort applied, will change the amount of material required. If you under-compact one driveway to only, say, 89% of specified density but compact another driveway to, say, the specified density of 93%, it will take different amounts of mix to achieve either end product.
2. The variation in thickness. The final shape is not readily measurable: You can't readily measure the thickness of the driveway without taking cores: How many cores would you need to take to determine the thickness for the entire driveway? What if you were 50mm thick where you took your core but everywhere else it was 40mm thick? Because the pavement is not readily measurable, we need a way to confirm that the installation meets our dimensional requirements. This is why we do a yield check at the end of an asphalt installation, comparing the actual delivered weight of material to a theoretical calculation of how much material should have been delivered. (If you need help in learning how to run this calculation, feel free to reach out to me).
In summary, we want to measure & pay for the material AND be able to confirm that we received the adequate quantity of material for the installation, and the only way to do that is by paying by weight, not by shape. I hope this helps!
A concrete-based element is designed to be a specific shape, such as a retaining wall footing - It is Length x Width x Height. Concrete does not have appreciable material variability or voids. In it's final shape, it can be readily measured, and for all practical purposes is 100% dense.
You could argue that, for an asphalt driveway let's say, you specify it to be 50mm thick x Length x Width, so it could be quantified similarly, right? There are 2 primary reason why we measure asphalt pavement by weight:
1. The variability of the in-place material. Compaction is required to achieve the final shape, and depending on the level of compactive effort applied, will change the amount of material required. If you under-compact one driveway to only, say, 89% of specified density but compact another driveway to, say, the specified density of 93%, it will take different amounts of mix to achieve either end product.
2. The variation in thickness. The final shape is not readily measurable: You can't readily measure the thickness of the driveway without taking cores: How many cores would you need to take to determine the thickness for the entire driveway? What if you were 50mm thick where you took your core but everywhere else it was 40mm thick? Because the pavement is not readily measurable, we need a way to confirm that the installation meets our dimensional requirements. This is why we do a yield check at the end of an asphalt installation, comparing the actual delivered weight of material to a theoretical calculation of how much material should have been delivered. (If you need help in learning how to run this calculation, feel free to reach out to me).
In summary, we want to measure & pay for the material AND be able to confirm that we received the adequate quantity of material for the installation, and the only way to do that is by paying by weight, not by shape. I hope this helps!
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