DESIGNING FLOWABLE MORTAR
The laboratory design of flowable mortar involves determining the proper proportions to obtain the required flow characteristics. A mix design submitted for approval may also be assessed for flow with plant produced flowable mortar.
Obtain representative samples of the following materials from the producing ready mix plant:
Sand 75 lb.
Portland Cement 15 lb.
Fly Ash 15 lb
1. Flow cone and equipment specified in IM 375
2. Mixer 4 qt. or larger
3. 1,000 mL cylinder
5. Equipment specified in IM 302
6. 1 mL pipette
B. Test Samples
1. Obtain samples for the sieve analysis and the trial mixes by one of the quartering methods listed in IM 302.
2. Two samples of at least 4,600 grams should be obtained for the trial mixes. Do not attempt to select a sample of an exact predetermined mass.
C. Preparation of Samples
1. Oven dry the samples to a constant mass and allow to cool. Screen the sample over a No. 4 (3/16 in.) sieve to remove over-sized material.
2. Weigh the dry sand samples to the nearest gram and calculate the cement and fly ash batch weight as follows:
Air entraining agent at 1 oz./cu. yd.
D. Mix Procedure
1. Add the air-entraining agent to the mixing water. Add the sand and part of the needed mixing water to the bowl. Start the mixer and add the cement, fly ash, and water. Add water until the mix appears fluid. Mix for three minutes after adding all materials.
When too much water is added, the water and solids will separate after mixing. If too much water is added on the initial trial, the mix should be discarded. A good starting point for the water is 70 gallons per cubic yard. The batch volume of water would be:
2. Record the amount of water added. Run the flow test as per IM 375 to obtain the efflux time.
3. If the time of efflux is too long, increase the amount of water, air-entraining agent, or fly ash to improve the flow on the second trial. If additional water causes separation of the water and solids, fly ash should be added in 100-lb. increments up to a total of 400 pounds per cubic yard. Some sands will not produce satisfactory mix and will need to be rejected.
E. Calculations and Reporting
1. Determine the final mix design weights as follows:
Portland Cement = 100 lb. Sand = 2,600 lb.
Air-Entraining Agent # oz./cu. yd.
2. Report the time of efflux to the nearest 1 second. The test report should be issued like the report in the Appendix.