Solving Percentages in Mix Design for Asphalt Plants | Help with Math Problems

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Hi, I am new to forums in general, but here goes. i have found myself stumped over a basic math problem with a new operating system on an asphalt plant I operate. I am sure there is a simple formula to solve this.

the mix design or "recipe" calls for percentages of stone and sand totaling 100 percent. so the design reads #8 gravel 20%, #8 limestone 18%, sand 5%, #12 limestone 18%, fines at 2%, recycled asphalt at 35% and recycled shingles at 2%.

i used to just type in the percentages on the mix computer and run the mix but on the new system my recycled products must equal 100 percent. so how do i express 37% of the recycle to equal 100%. so in my ignorance I used 95% recycled asphalt and 5% recycled shingles. (i came to this by multiplying 2.7 x 35 = 94.5 round up for a whole number 95%) this came about with trial. 2.5 no, 2.6 hmm not quite...

i hope this makes sense. try not to tear me apart because of my ignorance, lol. I have many skills but math seems to have slipped away as i grow older. its amazing what you lose if you become complacent. thanks
 

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dspicher said:
Hi, I am new to forums in general, but here goes. i have found myself stumped over a basic math problem with a new operating system on an asphalt plant I operate. I am sure there is a simple formula to solve this.

the mix design or "recipe" calls for percentages of stone and sand totaling 100 percent. so the design reads #8 gravel 20%, #8 limestone 18%, sand 5%, #12 limestone 18%, fines at 2%, recycled asphalt at 35% and recycled shingles at 2%.

i used to just type in the percentages on the mix computer and run the mix but on the new system my recycled products must equal 100 percent. so how do i express 37% of the recycle to equal 100%. so in my ignorance I used 95% recycled asphalt and 5% recycled shingles. (i came to this by multiplying 2.7 x 35 = 94.5 round up for a whole number 95%) this came about with trial. 2.5 no, 2.6 hmm not quite...

i hope this makes sense. try not to tear me apart because of my ignorance, lol. I have many skills but math seems to have slipped away as i grow older. its amazing what you lose if you become complacent. thanks

Hi dspicher, welcome to MHB.

I understand that you have certain ingredients for your mix, which total up to 100%. That's fine.

But then I'm not sure what it is you are asking. Are you saying you have to change your mix so that all of your ingredients are now recycled?
 
The mix design will remain the same but it will be broken into 2 parts. Recycled material and virgin material. the new computer program needs it entered as 100% recycled and 100% virgin material totals.

So just for example 37% of the total mix is recycle but i have to enter this to total 100%

2% becomes 5% and 35% becomes 95% to make up 100 percent of my recycle feeders.

Then I do the same with the 63% virgin material. The program needs to see 100% total. So i do the same crude "expansion" .

I think this will help explain.
 
dspicher said:
The mix design will remain the same but it will be broken into 2 parts. Recycled material and virgin material. the new computer program needs it entered as 100% recycled and 100% virgin material totals.

So just for example 37% of the total mix is recycle but i have to enter this to total 100%

2% becomes 5% and 35% becomes 95% to make up 100 percent of my recycle feeders.

Then I do the same with the 63% virgin material. The program needs to see 100% total. So i do the same crude "expansion" .

I think this will help explain.

To scale the numbers up, divide by the portion of the total. For example:

$$\frac{2\%}{.37}=\frac{200}{37}\%\approx5.405405405405405\%$$

$$\frac{35\%}{.37}=\frac{3500}{37}\%\approx94.5945945945946\%$$
 
Eureka. Thats what i wanted to learn. Thank you very much. I hope I can repay the favor some day.