Norlite Corporation 628 S. Saratoga Street Cohoes, NY 12047 Phone (518) 235-0030 Fax (518) 235-0233 E-mail: farchambault@norliteagg.com
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Pumping Norlite Structural Lightweight Concrete

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• Aggregate Saturation
• Greater Plastic Density
• Trial Pump
• Pump and the Pumping System
• Mix Designs
• Water-Cement Ratio
• Suggested Pumping Mix for Norlite Structural Lightweight Concrete

  O     1762 kg/m³ -- 9.5mm to 2.36mm	(110 p.c.f. -- 3/8 " Aggregate)
  O     1842 kg/m³ -- 19.0mm to 4.75mm	(115 p.c.f. -- 3/4 " Aggregate)
  O     1842 kg/m³ -- 9.5mm to 2.36mm	(115 p.c.f. -- 3/8 " Aggregate)

• Norlite's Pumping Suggestions

Norlite lightweight structural concrete has been successfully placed by the pumping method on construction sites all over the Northeast.

Aggregate Saturation

An important consideration in pumping lightweight is the void structure of the Norlite aggregate. Excessive line pressure may force water into these voids. This often results in a severe reduction of the flowability of the mix causing stoppage.

To make Norlite concrete more pumpable, it is important to attain the maximum saturation level of the aggregate by presoaking. Norlite may contain more than 20% by weight in surface and absorbed moisture. Presoaking is often accomplished by using an ordinary spray system. A minimum of 24 hours should be allowed with 72 hours or more preferred. This presaturation process aides in preventing the aggregate from absorbing water during the pumping process. It therefore minimizes slump loss as well as increasing the pumpability of the concrete.

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Greater Plastic Density

On the job site, the field technician will find as a result of the aggregate presaturation that the plastic density will be greater than the plastic density for nonsaturated lightweight aggregate concrete for the same air dry unit weight. But this increase in unit weight will eventually be lost thru atmospheric drying. The additional internal moisture also aides the internal curing of the concrete.

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Trial Pump

A pre-job field trial is recommended. The actual job site pumping equipment and mix design should be used. The participants should include representatives of the contractor, architect, structural engineer, pumper, testing laboratory and Norlite. Construction site conditions concerning height and distance the concrete is to be pumped should be simulated as closely as possible. The approximations commonly used to simulate conditions are; one foot to the vertical is comparable to four feet on the horizontal, one foot of rubber line is comparable to two feet of steel line and one 90 degree angle is comparable to three feet of steel line. Samples should be taken at discharge end of pump line.

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Pump and the Pumping System

Certain considerations should be made for the pumping equipment. Care should be taken to avoid rapid reduction in line size from the pump to the lines. It is preferrable to use the largest size line available with a minimum being a 5 inch inside diameter. An attempt should be made to reduce the operating pressure within the lines. This may be accomplished by maximizing the amount of steel line and minimizing the rubber line. The relationship of the piston head radius to the line size is also important. For example, a 6 inch piston head and a 5 inch line is a good combination. However, an 8" or 10" piston head within a 5" line may create pumping problems.

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Mix Designs

When structural lightweight concrete is pumped, certain adjustments may be necessary. The architect, engineer, contractor and pumper should be familiar with any adjustments required before the decision is made as to the method of placement. The ready-mix producer and the Norlite representative should be consulted so that the best possible pump mix can be determined. It is at this time the architect and engineer may decide if any specification changes would be necessary to accomodate pumping. The practical limits, on a unit weight basis, of pumping Norlite concrete vary according to the size of coarse aggregate. Norlite concrete using 3/4" lightweight aggregate with natural sand producing a plastic unit weight less than 117 pounds per cubic foot resulting in a 28 day air dry unit weight of less than 112 pounds per cubic foot may encounter some difficulties. However, 28 day air dry densities of 107 to 112 pcf may be attained with a mix design using 3/8" Norlite coarse aggregate with natural sand.

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Water-Cement Ratio

The mix designs on the following pages are based upon an estimated total water demand comprised of absorbed water and active water. That portion absorbed by the aggregate is not considered for determining yield since it has no volumetric effect. Due to the absorbed condition this water is not available to affect the cement paste. Therefore, as noted in ASTM C125 (Concrete and Concrete Aggregates), absorbed water is not considered when calculating the water-cement ratio.

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SUGGESTED PUMPING MIX FOR NORLITE STRUCTURAL LIGHTWEIGHT CONCRETE

Water-Cement Ratio

The mix designs on the following pages are based upon an estimated active water demand. That portion absorbed by the aggregate is not considered for determining yield since it has no volumetric effect.

Due to the absorbed condition this water is not available to affect the cement paste. Therefore, as noted in ASTM C 125 (Concrete and Concrete Aggregates), absorbed water is not considered when calculating the water-cement ratio.

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NOTE: These concrete mix proportions are based on the use of an airentraining admixture conforming with the requirements of Standard Specification for Air-Entraining Admixtures for Concrete, ASTM Designation: C 260, and a water reducing admixture conforming with the requirements of Standard Specifications for Chemical Admixtures for Concrete, ASTM Desgination: C 494. The following specific gravities were used to compile mix proportions. Cement 3.15, 19.0mm Norlite 1.25, 9.5mm Norlite 1.30, Sand 2.63 Water 1.0.

Trial mixes must be carried on to establish air and slump at the pump for required strength and weight in place.

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Norlite's Pumping Suggestions

DESIGN ENGINEER

1. Be realistic on air dry weights. Know capabilities of the market area.
2. Specify max. size aggregate.
3. Allow 7" slump into pump.
4. Have testing lab run design curves based on 7" slump.
5. Specify pre-pump meeting with the following present: Design Engineer, General Contractor, Ready Mix Supplier, Lightweight Aggregate Supplier, Testing Agency, and Pumping Contractor.
6. Same people should be present at the first concrete pump placement.
7. Specify exactly where concrete should be tested. (Preferably at end of discharge line).
8. Define free water and absorbed water for w/c ratio and wet unit weights.

GENERAL CONTRACTOR

1. Keep everyone communicating (team effort).
2. Check history of pumping contractor.
3. Make arrangements for two r/m trucks to unload at one time.
4. Designate a laborer to help testing lab inspector move concrete test specimens.
5. Provide washout area of r/m trucks.
6. Make use of r/m truck radio when placement delay occurs.
7. Specify to r/m supplier how many yards per hour you want.

PUMPING CONTRACTOR

1. Know what unit weight you are pumping.
2. Order concrete for the time you will be ready to start pumping.
3. Stagger coffee breaks.
4. Operator should know max. slump he can use.
5. 5" minimum steel lines; minimum rubber at end of line.
6. Low pressure pumps will have the least slump loss.

READY MIX PRODUCERS

1. Soak the aggregate.
2. Moisture content should be checked every time bins are filled.
3. Make drivers aware that pump aid and/or fly ash being used.
4. Minimum slump of 4" for high range water reducers.

TESTING LABS

1. Monitor moisture properly.
2. Field inspector should have roll-a-meter, scale, strike off plate.
3. Suggest same inspector on critical job.
4. Inspector should know min. and max. wet weights.
5. Test cylinders should not pre-set on floor concrete is being placed on.
6. Plastic density will vary depending on the moisture absorbed in the aggregate.

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