STRUCTURAL LIGHTWEIGHT CONCRETE
This Guide Specification has been prepared to supplement the Architect-Engineer's standard concrete specifications where structural lightweight concrete is to be used.
Part I - General | Part II - Products | Part III - Control | Appendix | Comments
PART I - GENERAL
1.1 REFERENCE STANDARDS
1.1.1 AMERICAN SOCIETY FOR TESTING AND MATERIALS (ASTM)
1. ASTM C 31, Standard Practice for Making and Curing Concrete Test Specimens in the Field
2. ASTM C 33, Standard Specifications for Concrete Aggregates
3. ASTM C 39, Standard Test Method for Compressive Strength of Cylindrical Specimens
4. ASTM C 94, Standard Specifications for Ready-Mixed Concrete
5. ASTM C 127, Standard Test Method for Density, Relative Density (Specific Gravity) and Absorption of Coarse Aggregate
6. ASTM C 138, Standard Test Method for Density (Unit Weight), Yield, and Air Content (Gravimetric) of Concrete
7. ASTM C 143, Standard Test Method for Slump of Hydraulic Cement Concrete
8. ASTM C 150, Standard Specifications for Portland Cement
9. ASTM C 172, Standard Practice for Sampling Freshly Mixed Concrete
10. ASTM C 173, Standard Test Method for Air Content of Freshly Mixed Concrete by the Volumetric Method
11. ASTM C 205, Standard Specifications for Portland Blast Furnace Slag Cement
12. ASTM C 260, Standard Specifications for Air Entraining Admixtures for Concrete
13. ASTM C 330, Standard Specifications for Lightweight Aggregates for Structural Concrete
14. ASTM C 331, Standard Specification for Lightweight Aggregates for Concrete Masonry Units
15. ASTM C 340, Standard Specifications for Portland-Pozzolan Cement
16. ASTM C 494, Standard Specifications for Chemical Admixtures for Concrete
17. ASTM C 567, Standard Test Method for Determining Density of Structural Lightweight Concrete
18. ASTM C 595, Standard Specifications for Blended Hydraulic Cements
19. ASTM C 618, Standard Specifications for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use in Concrete
20. ASTM C 845, Standard Specifications for Expansive Hydraulic Cement
21. ASTM C 989, Standard Specifications for Ground Granulated Blast-Furnace Slag for Use in Concrete and Mortars
22. ASTM C 1017, Standard Specifications for Chemical Admixtures for Use in Producing Flowing Concrete
23. ASTM C 1157, Standard Performance Specifications for Hydraulic Cement
24. ASTM C 1240, Standard Specifications for Silica Fume Used in Cementitious Mixtures
1.1.2 AMERICAN CONCRETE INSTITUTE (ACI)
1. ACI Manual of Concrete Inspection
2. ACI 211.2, Standard Practice for Selecting Proportions for Structural Lightweight Concrete
3. ACI 213, Guide for Structural Lightweight Aggregate Concrete
4. ACI 301 Specifications for Structural Concrete for Buildings
5. ACI 304.2 Placing Concrete by Pumping Methods
6. ACI 304.5R, Batching, Mixing, and Job Control of Lightweight Concrete
7. ACI 305R, Hot Weather Concreting
8. ACI 306R, Cold Weather Concreting
9. ACI 318 Building Code Requirements for Reinforced Concrete
1.2.1 Except as modified or exceeded by these specifications all cast in place structural lightweight concrete work shall conform to ACI 301.
1.3 STORAGE OF MATERIALS
1.3.1 Cement: Store in weather tight enclosures and protect against dampness, contamination and warehouse set in accordance with ACI 318.
1.3.2 Aggregates: Each gradation of lightweight aggregate as supplied, shall be stockpiled in separate bins or piles. Storage shall minimize segregation and prevent contamination.
2.1.1 CEMENT: ASTM C150 or C595. Air-entraining cement will not be permitted.
184.108.40.206 FLY ASH: Shall meet ASTM C618.
2.1.2 AGGREGATE: Expanded shale, clay or slate produced by the rotary kiln method and shall conform to ASTM C330. Natural sand shall conform to ASTM C33.
2.1.3 MIXING WATER: Clean and free from injurious amounts of oils, acids, alkalis, organic materials or other deleterious substances, in accordance with ACI 318.
220.127.116.11 AIR-ENTRAINING AGENTS: ASTM C260.
2.1.1 The effect and comparability of various combinations of cement, fly ash and/or admixtures is generally the same in expanded shale lightweight concrete as in normal weight concrete.
18.104.22.168 WATER REDUCING ADMIXTURES: ASTM C494.
Admixtures may be used, provided they have a proven satisfactory performance record with structural concrete and are approved by the Architect-Engineer. Admixtures shall be used in accordance with the manufacturer's recommendations.
22.214.171.124 Consistent with comment 2.1.1, high range water reducing admixtures have demonstrated satisfactory performance with
expanded shale lightweight concretes. You should consult the lightweight aggregate producer in your area for specific information
concerning the performance of his aggregate with high range water reducing admixtures.
126.96.36.199 ACCELERATING ADMIXTURE: ASTM C494. Admixtures may be used only with the approval of the Architect-Engineer.
188.8.131.52 RETARDING ADMIXTURE: ASTM C494. Admixtures may be used only with the approval of the Architect-Engineer.
2.2 CONCRETE PROPERTIES
2.2.1 Materials shall be proportioned to produce concrete with a minimum compressive strength of____ psi (____ Mpa) at 28 days.
2.2.2 Materials shall be proportioned to produce concrete with a maximum equilibrium density of _pcf (_kg/m3) at ___days age, as determined by ASTM C567.
2.2.3 Concrete shall be delivered at the minimum slump necessary for efficient mixing, placing and finishing. The maximum
slump shall be ___in. (___mm) with a tolerance of ± 1 in. (±25 mm).
2.2.4 The air content shall be percent by volume with a tolerance of ± 2 percent.
2.2.5 The Contractor shall furnish the mix design for the strength and density of concrete specified. The mix design shall be prepared
by a qualified testing laboratory and may be based upon the recommendations of the aggregate producer. The mix design
shall be subject to the approval of the Architect-Engineer.
2.2.6 The Concrete shall be batched and mixed in accordance with ASTM C94.
PART 3 - CONTROL
3.1 FIELD CONTROL
3.1.1 The control of the concrete shall be under the supervision of the Architect-Engineer.
3.1.2 Samples of concrete shall be obtained in accordance with ASTM C172, and shall be transported to a place on the site where tests can be made and cylinders stored without being disturbed for the first 24 hours. In addition, if the concrete is placed by pumping, samples shall be obtained from the end of the pump discharge line.
3.1.3 Compressive strength specimens shall be made in accordance with ASTM C31, with the exception that the curing requirement for the test specimens shall be 7 days of moist curing followed by 21 days of air drying. as detailed in ASTM C330. Section 8.1.1 for each of the following conditions:
184.108.40.206 Each day's placing;
220.127.116.11 Each type of concrete;
18.104.22.168 Each change of supplier or source;
22.214.171.124 Each 150 cu. yd. (115m3) of concrete and fraction thereof.
3.1.4 Compressive strength specimens shall be tested in accordance with ASTM C39.
3.1.5 Density. slump and air content of fresh concrete shall be determined from each batch of concrete sampled for compressive strength tests. Fresh density, slump and air content shall be determined by ASTM C138, C143, and C173 respectively. The fresh density of the concrete shall not exceed the design weight plus the weight loss factor determined from project trial mixes by ASTM C567.
The following is a list of ACI publications that will be of assistance to the Architect-Engineer when preparing specifications for the use of structural lightweight aggregate concrete.
. ACI 211.2 Recommended Practice for Selecting Proportions for Structural Lightweight Concrete.
. ACI 212.2R Guide for Use of Admixtures in Concrete.
. ACI 213R Guide for Structural Lightweight Concrete.
. ACI 301 Specifications for Structural Concrete for Buildings.
. ACI 302 Recommended Practice for Measuring, Mixing Transporting and Placing Concrete.
. ACI 305R Hot Weather Concreting.
. ACI 306R Cold Weather Concreting.
. ACI 318 Building Code Requirements for Reinforced Concrete.
. ACI 347 Recommended Practice for Concrete Formwork.
. ACI 311.5R Manual of Concrete Plant Inspection and Testing of Ready-Mixed Concrete
These Guide Specifications have
been prepared following the 16
Division Format of the
Institute, Section 03313 Concrete.
These comments are intended to
help the Architect-Engineer set
down limits in his specifications
and to so write them that he can
obtain the quality of structural
lightweight concrete required by
the design in an economical
The Standards that are listed
under Reference Standards are
the ones quoted in the specification.
In the Appendix there is a list
of ACl publications that will be of
assistance to the Architect-
Engineer when preparing his
2.2 CONCRETE PROPERTIES
The requirements of this paragraph
as well as those of 2.2.5 should be
repeated in the specifications if
more than one type of concrete is
required by the design.
2.2.1 Expanded shale aggregate
has been used in lightweight concrete
for practically every type of
structural application. It has been
furnished at all compressive
strength levels common to construction
practice today, including high
strength of 5000 and 6000 psi
(34.4 - 41.4 MPa) or more when
2.2.2 The weight of this concrete
will range from 70 to 120 pcf (1120
to /1920 kg/m3) depending upon
the strength, air content, aggregate
density and mix proportions. The
equilibrium density is normally from
5 to 10 pcf less than the fresh
density of the concrete as placed.
The amount of weight loss in curing
is primarily affected by the moisture
content of the lightweight aggregate
when it is batched. Also, expanded
shale lightweight concrete will gain
strength and lose weight even after
the classical 28 day requirement.
This is due to the absorbed moisture,
and is especially significant in
pumped lightweight concrete. The
concrete may gain 500-1000 psi
(3.4-7 MPa) and may lose 2% or
more in density, in a period
between 28 and 98 days, at which
time it approaches density equilibrium.
If the design conditions will
allow extending the time for
strength and/or density requirements,
it will allow a more economical
mix to be used. Consult the
lightweight aggregate producer in
your area for specific information
relating to his aggregate.
2.2.3 The Architect-Engineer should
require that the mix be designed for
the specified compressive strength
and density with a slump which will
enable the concrete to be placed
and finished efficiently and economically.
This slump should be specified.
If the concrete is to be placed
by pumping, certain considerations
such as presaturation of lightweight
aggregates, use of admixtures and
minimum cement content may be
necessary. The Aggregate Producer
can supply the Architect-Engineer
recommended mixes for special
placing conditions. The workability
of structural lightweight concrete is
comparable with that of normal
weight concrete having 1 to 2 in.
(25 to 50 mm) greater slump.
Shape and dimensions of forms,
placement of reinforcement and
other specified job conditions vary.
However, the following are generally
satisfactory; for slabs and beams 3
to 5 in. (80 to 130 mm). For
columns and walls 2 to 4 in. (50 to
2.2.4 Air-entrainment in structural
lightweight concrete, as in normal
weight concrete, improves durability,
workability and reduces bleeding.
Generally the aggregate producer
recommends air entrainment to
achieve workability with minimum
slump. For durability, 5 to 8 percent
air is required; for workability, 4 to 6
percent is generally satisfactory. The
Architect-Engineer should specify
the amount of air content required
for the most economical mix and for
the specific application.
2.2.5 In establishing batch proportions,
trial mixes should produce
concrete with an average compressive
strength higher than
specified in 2.2.1. The aggregate
producer generally follows one of
the procedures that are outlined
in ACI 211.2, Recommended
Practice for Selecting Proportions
for Structural Lightweight
Concrete. The degree of over
design required depends on variability
of test results. See AC1318,
Building Code Requirements for
Reinforced Concrete, Section 4.4.
It is recommended that the
Architect-Engineer obtain from the
aggregate producer a recommended
economical cement content,
slump, air content and density for
the strength of concrete required
by the structural design and for
the finishing qualities desired.
2.2.6 In designing structural lightweight
concrete mixtures, the
question is often raised regarding
the effect of aggregate absorption.
Prewetting requirements in specifications
to provide for this characteristic
of the aggregate often lead
to difficulty in control.
Consequently, these specifications
do not contain prewetting requirements.
The mix and the control of
the mix proportions should be
established and maintained by
the producer's quality control personnel
or a qualified laboratory
based upon the recommendations
of the aggregate producer. With
this approach, the variations that
exist in batching arrangements,
ready-mixed plant layouts, weather,
as well as in aggregate properties,
can be taken into account to
produce the most efficient and
3.1.3 The modified curing cycle
for lightweight concrete is reasonable
due to the large amount of
absorbed water in lightweight
aggregate concretes as compared
to normal weight concretes. This
curing cycle is standard practice
for the expanded shale industry,
and is recognized in ASTM C330.
3.1.5 The density, slump and air
content determinations at intervals
specified enable the
Architect-Engineer to maintain uniformity
in the concrete mixture. As
long as there is no appreciable
change in the density, i.e., not
more than 2 pcf (32 kg/m3) variation
from the established fresh
density, there is reasonable certainty
that the correct proportions
are being batched. Variations
greater than 2 pcf (32 kg/m3)
indicate that some change has
taken place in air content, weight
of aggregate or batch weights,
thereby resulting in a variation of
yield. When this occurs, proper
adjustments in the mix should be
made at once to bring concrete
quality back to that specified.