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Structural Lightweight Concrete

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• Introduction
• Stockpiling
• Production
• Finishing
• Mix Proportions
  • Suggested Mix Proportions for Norlite Structural Lightweight Concrete

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

  • Suggested Mix Proportions of all Norlite Insulating and Roof Fill Mixes

    »     90 p.c.f. -- 3/4" Aggregate	(1442 kg/m³ -- 19.0mm to 4.75mm and 2.36 to 100um)
    »     90 p.c.f. -- 3/8" Aggregate	(1442 kg/m³ -- 9.5mm to 2.36mm and 2.36 to 100um)
    »     80 p.c.f. -- 3/4" Aggregate	(1282 kg/m³ -- 19.0mm to 4.75mmand 2.36 to 100um)
    »     84 p.c.f. -- 3/8" Aggregate	(1346 kg/m³ -- 9.5mm to 2.36mm and 2.36 to 100um)

• Mix Design Worksheet

Introduction

The ACI Committee Report 213, Guide for Structural Lightweight Aggregate Concrete, defines structural lightweight concrete as having a 28 day air dry unit weight not exceeding 115 pounds per cubic foot.

For purposes of weight savings, fire rating (see Fire Rating Index) and thermal insulation the usual specification for Norlite Concrete is one having a 28 day air dry unit weight of 110 ± 2 pounds per cubic foot.

Because Norlite is a Rotary Kiln expanded shale the manufacturing process creates an insulating material. Within each aggregate there are millions of minute separated air cells which greatly enhance the thermal resistance (R) of the concrete. This provides an energy cost saving throughout the life of the building. Also, its higher thermal resistance contributes to a greater fire endurance than normal weight concrete resulting in lower insurance costs.

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Stockpiling

It is recommended that our Norlite customers follow a few handling and-stockpiling procedures in order to maintain the proper gradations. Cone stockpiling should always be avoided to prevent segregation. Stockpiles should be arranged so that stocking and removal operations may be conducted without having machinery rolling onto or over the inventoried aggregate.

The method of removing material from a stockpile is also of importance. Handling equipment should be worked straight into the stockpile as far as practically possible. The adjacent areas may then be worked in the same manner. Stockpiles should never be worked around the edges one load at a time.

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Production

Norlite involves no great difficulties in the batching and mixing operations. This lightweight aggregate has a higher moisture absorption capability than sand and gravel stone. Because the moisture content varies more sharply with atmospheric conditions than the natural aggregates, the moisture content of the Norlite should be known at the time of mixing. This will allow the proper calculation for free water and yield. Experience has shown that Norlite in a dry condition will absorb 5% to 8% moisture within the first two or three minutes of mixing the water and lightweight aggregate as recommended below. After this initial water demand has been met, there is no appreciable absorption. For this reason saturation of the lightweight aggregate to its maximum absorption is not necessary (with the exception of pumping). The following mixing procedures are recommended.

1. Charge the mixer with approximately 2/3 of the total mixing water and all of the lightweight aggregate. Allow high speed mixing for a period of 2 to 3 minutes.
2. If natural sand is used it may then be added along with any air entraining agent.
3. The cement and remaining water are then introduced along with any water reducing agent.

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Finishing

On deck work a high frequency vibrating screed is effective. Aluminum or magnesium finishing tools are preferred and a minimum amount of floating and troweling is recommended.

In order to avoid segregation, the measured slump of the concrete at point of placement should be approximately 3 to 4 inches. This will allow the concrete to retain sufficient consistency in order to prevent the lightweight aggregate from migrating to the surface.

Mix Proportions

The following are suggested mix proportions only and actual batch quantities should be established based upon laboratory prepared trial mixtures using materials intended for use on a specific project. These concrete mix proportions are based on the use of an air-entraining admixture conforming with the requirements of Standard Specification for AirEntraining Admixtures for Concrete, ASTM Designation: C 260, and a water reducing admixture conforming with the requirements of Standard Specification for Chemical Admixtures for Concrete, ASTM Designation: C 494.

These concrete mix proportions are based on sand in a saturated surface dry condition (SSD) and Norlite coarse and fine aggregate in an oven dry condition. Adjustments in aggregate and water quantities must be made based on the actual moisture content of the aggregates at the time of batching. Since Norlite normally contains from 4 to 8 percent moisture as shipped, batched weights per cubic yard of concrete will vary according to the moisture content, which may be as high as 25%.

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Suggested Mix Proportions 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 air entraining 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 Designation: C 494. The following specific gravities were used to compile mix proportions. Cement 3.15, 3/4" Norlite 1.25, 3/8" 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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Currently viewing US Standard      (Click here to view  Metric)

Suggested Mix Proportions for all Norlite Insulating and Roof Fill Mixes

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Currently viewing US Standard      (Click here to view  Metric)

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Currently viewing US Standard      (Click here to view  Metric)

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Currently viewing US Standard      (Click here to view  Metric)

NOTE: These concrete mix proportions are based on the use of an air entraining admixture conforming with the requirements of Standard Specifications for Air-Entraining Admixtures for Concrete, ASTM Designation: C 260, and a water reducing admixture conforming with the requirements of Standard Specification for Chemical Admixtures for Concrete, ASTM Designation: C 494.

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Currently viewing US Standard      (Click here to view  Metric)

Mix Design Worksheet

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