27-03-2012, 12:11 PM
Laboratory Investigation of Lightweight Concrete Properties
11-r17.pdf (Size: 260.54 KB / Downloads: 151)
Abstract:
Lightweight concrete (LWC), with its reduced weight and improved durability, enables longer spans, fewer piers, and
longevity for bridge structures. The current emphasis on upgrading structures makes LWC highly desirable as a construction
material since superstructures with wider shoulders or more lanes can be upgraded without major work on the substructure.
The purpose of this study was to evaluate the density (unit weight), splitting tensile strength, and elastic modulus of
LWC mixtures under different curing conditions to achieve a better understanding of the LWC properties that are essential for
long-lasting and cost-effective structures. Further, the study examined the correlation between the results of the rapid chloride
permeability test and the surface resistance test using the Wenner probe to investigate whether the latter could be used to predict
the permeability of LWC mixtures, as it is faster and more convenient. The scope of the study was limited to LWC mixtures
having different lightweight aggregates prepared and tested in the laboratory.
The results indicated that measured densities are different than those calculated from batch weights; curing conditions
affect the splitting tensile strength and elastic modulus values; and the correlation between the results of the rapid chloride
permeability test and the surface resistivity test for a given lightweight aggregate was good.
ABSTRACT
Lightweight concrete (LWC), with its reduced weight and improved durability, enables
longer spans, fewer piers, and longevity for bridge structures. The current emphasis on
upgrading structures makes LWC highly desirable as a construction material since
superstructures with wider shoulders or more lanes can be upgraded without major work on the
substructure.
INTRODUCTION
Lightweight concrete (LWC) has been used for more than 2,000 years (ACI 213R)
(American Concrete Institute [ACI], 2003). Early notable LWC structures include the Port of
Cosa, the Pantheon Dome, and the Coliseum. In modern times, structural LWC structures are
widely used but to a much lesser extent than normal weight concrete. With the current emphasis
on upgrading structures, LWC will be very beneficial since it provides improvements in the
superstructure such as wider shoulders and more lanes without the necessity of any major
improvements to the substructure. LWC can also provide longer life with low maintenance.
There are many examples of the successful use of LWC in and outside the United States
(Fidjestol, 2003; Ramirez et al., 2000).
PURPOSE AND SCOPE
The purpose of this study was to evaluate the density (unit weight), splitting tensile
strength, and elastic modulus of LWC mixtures under different curing conditions to achieve a
better understanding of the LWC properties that are essential for long-lasting and cost-effective
structures. Further, the study examined the correlation between rapid chloride permeability and
surface resistance to investigate whether the latter could be used to predict the permeability of
LWC mixtures, as the SR test is faster and more convenient.
Fresh Concrete Properties
For the 14 batches, the fresh concrete properties given in Table 4 indicate workable
concretes with air contents ranging from 3.5% to 8%. Fresh concrete densities ranged from
116.8 to 123.6 lb/ft3 as shown in Table 4. The measured oven-dry densities (Om) ranged from
105.5 to 120.7 lb/ft3, and the measured equilibrium densities (Em) ranged from 111.9 to 126.4
lb/ft3, as shown in Table 5.
Hardened Concrete Properties
Strength and Elastic Modulus
The compressive strengths are given in Table 7, the elastic moduli in Table 8, and the
splitting tensile strengths in Table 9. The relationships between strength and elastic modulus for
different curing conditions were analyzed statistically using the paired t-test and are presented in
Table 10. The highest 28-day compressive strengths were achieved by specimens that were
moist cured followed by those subjected to steam plus air; the differences in averages were not
found to be significant. However, the differences in the average compressive strength between
the specimens with the lowest average, i.e., steam plus moist-cured specimens, and the other two,
i.e., exposed to moist environment or steam plus air, were significant.