A new kind of mix
Concrete design innovations
seek to reduce job costs
A reduction in job costs - often achieved through reductions
in placement times or materials - is the ultimate goal of
most new innovations in the concrete industry.
In the building market, two of the latest attempts toward
this financial objective include self-consolidating concrete
and pervious mix designs.
Craig Duos, executive director of the Concrete and Aggregates
Association of Louisiana, said self-consolidating mix is gaining
a lot of attention because it offers a much faster concrete
"Self consolidating concrete is a mix that flows more
easily around the reinforcing steel and through the form,"
Mike Seal, a sales representative with Lafarge Corp. of
New Orleans, said the greatest benefits of the self-consolidating
mix are its flowability and uniform distribution of aggregates.
The mix has fairly small pea gravel as its aggregate and
has the properties of a fluid during placement, Seal added.
It can achieve an outward flow of up to 550 to 650 mm.
His company's self-consolidating mix, called Agilia, has
architectural and vertical applications.
The architectural form of the product is typically used for
heavily reinforced or highly congested applications, seismic
zone construction, walls, columns, spans, precast and applications
with an architectural finish requirement.
Agilia's vertical application is used for spans, precast,
walls, columns, heavily reinforced or highly congested applications,
and applications with a high quality surface requirement.
"The product is most useful for surfaces that require
an excellent finish, heavily reinforced structures or members,
and structures or members with complex forming," Lafarge
sales representative Steve Salzer said. It also provides the
architectural and engineering communities with a product that
allows for enhanced design creativity, such as for exposed
walls and columns in large-scale commercial or residential
Duos said pervious concrete is also gaining in popularity
because it allows water to seep through the mix. This makes
it attractive to owners and contractors who wish to control
"It was originally developed for underdrain systems
and for areas that cannot permit any additional runoff into
the system," Duos said. "It allows moisture to percolate
through the concrete into the soil below."
Reducing the "fines" in the mix and using more
intermediate or larger stones as aggregate help create the
"Now it's starting to see the light of day as a system
for use in parking areas and places that have to comply with
stormwater retention regulations," Duos said. "In
some cases they'll say you can put a building in a certain
location but you can't increase stormwater runoff."
Highway applications. A
section of Interstate 10 in east Baton Rouge will soon provide
the testing grounds for a new method of determining flexural
strength in pavement concrete.
James Construction Group is building the $40 million I-10/Picardy
Avenue Interchange and should begin paving this fall.
John Eggers, an engineer with the Louisiana Transportation
Research Center, said Department of Transportation and Development
designs often specify flexural strength even though there
has never been an accurate way to measure it.
"In the past, quality control testing has been based
upon compressive, not flexural, strength," Eggers added.
"But if the concrete pavement is designed using a flexural
strength it needs to be measured that way."
At the I-10 site, a flexural test will measure the concrete's
"Samples of the concrete mix will be used to create
a rectangular test beam and we'll use a flexural testing machine
with a three-point loading system to determine its strength,"
Eggers said. The testing will occur throughout the project
for quality assurance.
He added that a flexural strength of 750 psi is specified
on the I-10 project, while most jobs have a typical strength
of 600 psi.
"A higher flexural strength will allow us to decrease
the thickness of the pavement, which will in turn save us
money," Eggers added. Varying the gradation of components
in the mix by adding more crushed stone or cement can help
achieve the higher flexural strength.
"It's ultimately up to the contractor and the concrete
supplier to determine how they're going to achieve it,"
Duos said increasing the flexural strength will allow DOTD
to decrease the amount of concrete necessary for a project
and therefore make the material less costly and more attractive
for road construction.
Mark Morvant, LTRC's pavement & geotechnical research
administrator, said his office is researching the use of cement
as soil stabilization for road subgrades.
Traditional lime treatment has been ineffective in soils
with a high concentration of silt.
"We've basically switched from lime to cement under
certain conditions," Morvant said. "Lime requires
more cohesive soils to have a reaction for stabilization.
So with silty soils, there's no long-term performance."
Most of the silty soils have been found in west and northeast
portions of the state. Most recently, a four-laning project
on LA 15 near Sicily Island specified a cement-stabilized
Morvant said tests this summer at DOTD's Accelerated Load
Facility in Port Allen will enable state engineers to determine
if other cost-saving changes can be gained by using cement.
"Until now, we haven't given it any value in our design
process," he added. "With the ALF section, we're
trying to find out if we can reduce the depth of the pavement
layers when using the cement as stabilization."
F. G. Sullivan Jr. Contractor LLC of Baton Rouge will build
the test section at the ALF facility this summer in conjunction
with an existing overlay project on LA 1.
For more information and updates about LTRC research, go