SEALCOATING MIX DESIGN CALCULATIONS
excerpt courtesy of Neal Manufacturing Asphalt Maintenance Handbook
You can download the handbook free at www.nealequip.com
NOTE: This excerpt uses Coal Tar as its base material to calculate the mix design. The mix design for asphalt emulsions can vary slightly depending on the material. It is always a good idea to consult your material provider. For an accurate mix design using coal tar or asphalt emulsions use the Paveman Pro mix design calculator on this web site.
Obtaining the proper mix design is very important. The quality of your final mix depends heavily on the quality of your materials, and the reliability of your supplier. We recommend that you only use coal tar that meets or exceeds the federal specification ASTMD- 5727. Your supplier should have an on site laboratory for testing to insure that he is within the specification at all times. Should you doubt that your supplier is meeting ASTMD- 5727, obtain a sample of coal tar emulsion and contact Neal Mfg. We can direct you to a lab that will test the material. The proportions of each element in your mix depends on the mix design you choose to use. Some may choose not to use sand, while some may see the need for liability purposes. Sealer with no sand can be slippery when wet. Without sand you may encounter people slipping, on the parking lot and cars sliding. A good, quality sealer will suspend sand (up to 5 lbs per gallon) without the assistance of latex additive. To insure that the higher sand loads (5-6 lbs) is suspended properly, a latex is needed.
The following proportions serve as a guideline in determining your mix design.
Coal Tar Emulsion = 100
Water = 30 (gallons)
Sand = 300 lbs or 15 gal
Latex = 2 gal
Other variations of mix designs are included in this section. The recommended mix design is sealer with sand and latex.
MIXING
You will start with undiluted coal tar ASTMD- 5727 in your mixing tank. Whenever mixing, it is imperative that the agitation system is turning at all times. However, DO NOT open the inner lid on your system without shutting the system completely down. The sequence and rate of entry are as follows:
1. Coal Tar Emulsion
2. Water – Allow to mix 5 to 10 min.
3. Additive (if needed) – Allow to mix thoroughly – Dilute 1:1 with water from 2, then add slowly, taking about 1 min. per 5 gal. pail
4. Sand – Add slowly (100 lbs. per min.) Allow to mix thoroughly.
After all the ingredients have been added, let them agitate for 5 to 10 minutes before application. During application, the agitator should continue to turn.
The guideline displayed earlier for mix designs is somewhat vague. Amounts of water, sand, and latex must be more precise for application. Consider the following sample job. We have a job that is 10,000 square yards. Our coverage rate for the job will be 5 square yards per gallon of mixed coal tar. This coverage includes two coats of coal tar. Our mix design consists of coal tar, water, 3 lbs. of sand per gallon of coal tar, and 2% latex additive. We will first set up the mix design like an equation. We always base our mix designs on the gallons of coal tar.
The total process in figuring our mix design is a three step process.
I. Set up an equation as follows: Our objective is to determine how many total gallons we will have after we mix our material.
a. 100 gallons of coal tar ASTMD 5727
b. 30 gallons of water
c. (15 liquid gallons of sand) 3 lbs of sand per gallon of coal tar (3 x 100=300) Therefore we will be using three 100 lb bags of sand. 20 lbs of sand will displace liquid gallon. We always take our total pounds of sand and divide it by 20. 300 divided by 20 = 15. We will refer to the 15 as “liquid gallonsâ€.
d. 2 gallons of undiluted additive or 2%.
e. Add a, b, c, d. This equals 147. After you mix all of the above, you will have a total of 147 gallons of mixed
material in your tank.
2. Our next objective is to determine our coal tar factor. You started your mix with 100 gallons of coal tar, then after you mixed you ended up with 147 gallons. Take 100 and divide it by 147. 100 divided by 147 = .680. This is your coal tar factor. This says that 68.0% of 179 gallons is coal tar. If you alter your mix design you will have a different coal tar factor.
3. The next objective is to determine the amount of material needed for our job. We have already determined our mix design and coal tar factor. We know we have 10,000 square yards to cover with two coats. Our coverage rate is 5 square yards per gallons of mixed coal tar. (convert square yards into square feet by multiplying by 9 and square feet to square yards by dividing by 9)
a. 10,000 (yards to be covered) divided by 5 yds per gallon (coverage rate) = 2,000 Gallons (total gallons needed of mixed material.)
b. This is where we use the coal tar factor. The coal tar factor for this mix design is .680. (see step 2) Remember this tells us how much of the total mix is undiluted coal tar.
c. 2,000 (total mix) x .680 (coal tar factor) = 1,360 Gallons (amount of undiluted coal tar needed)
d. Now lets refer to step I again. Set up the same equation, based on 1,360 of undiluted coal tar.
e. 1. 1,360 gallons of coal tar
2. 408 gallons of water (30% dilution)
3. 204 (liquid gallons of sand) 3 lbs per gallon x 1,360 gallons =4,080 lbs or 40.8 bags.
4,080 divided by 20 = 204 liquid gallons of sand.
4. 28 gallons of additive. 1,360 x .02 = 27.20 rounded off to 28
5. 2,000 total gallons. Remember, this is what step 3a told us we needed to do the job. Now we know the exact proportions of each ingredient. A several gallon variation (5-10) would be insignificant.
MIX COST ASSUMPTIONS
Coal Tar = $1.90 per gallon x 2,000 gallons = $3,800.00
Water = $0 (No cost normally)
Sand = $6.00 per 100 lb bag (5.70 Per bag X 41 Bags= $233.70)
Additive = $15.00 per gallon ($15.00 X 28 = $420.)
Total Cost For Job:
CT $3,800.00
Sand $233.70
Latex $420.00
TOTAL $4,453.70
Again, this is strictly your material cost. Your labor costs are affected by the amount of cleaning, the amount of trim work required, the time of the season, and the experience of your crew. ESTIMATED TIME ON A JOB THIS SIZE WOULD BE 3 TO 5 HOURS MAXIMUM.
PLEASE NOTE: IT IS IMPOSSIBLE FOR US TO APPLY AN OVERHEAD RATE TO THESE FIGURES. Many of our contractors operate out of their home, while some have large offices with vast amounts of construction equipment. Each contractor has a different amount of overhead. . Please figure your overhead to these numbers to determine your net profit. As a group most of our contractors report their net profit ranges between 40% and 60%.
VERY IMPORTANT: Please remember that the mix ratios we use are only guidelines. Different types of additives and sealers require different ratios of coal tar, sand and additive. Consult your material manufacturer for exact mix ratio.
