November 4, 2024 • 21 mins
Advances in materials science and rapidly developing technologies are leading to new approaches to engineering concretes and building infrastructure. Reza Moini, assistant professor of civil and environmental engineering at Princeton University, discusses his work with concrete, 3D-printing techniques and how his lab takes inspiration from nature as it works to reimagine the future of building materials.
Mark as Played
Transcript
Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
(00:03):
This is the Discovery Files podcast
from the US National Science Foundation.
Concrete is all around us.
It's in the buildings we live in.
The sidewalks we travel on
and the infrastructurethat allows us to have fresh water.
Concrete is a tough material,but over time and given
the right conditions,it can crack and crumble and fail.
Advances in material scienceand processing can
(00:25):
enhance concrete's resilience.
Recyclability and long term
durability, enabling significanteconomic and societal benefits.
We're joined by Reza Moini, assistantprofessor in the Department of Civil
and Environmental Engineering
and an affiliated facultyat the Andlinger Center for Energy
and the Environmentat Princeton University,
where his lab is developingresilient materials and structures
(00:45):
with bio inspired designsfor architected civil engineering projects
enabled by automated manufacturingrobotic systems.
Professor Moini,thank you for joining me today.
Thank you for having me.
I'd like to startwith just a bit of your history.
How did you become interested in concrete?
Right.
So my interest in concretestarted from my undergraduate studies
when I first took concretematerial science and technology.
(01:08):
It really fascinated me how complexthe organic chemistry of the most
commonly human made material was,and how the chemistry controlled
the material microstructure or thethe fabric of the material, if you wish.
That then governed in coursesthat I later learned the conservative
mechanical properties and the resultingperformance of these materials.
(01:30):
For the next few questions,
I want to ask you about a few conceptsthat are at play in your work.
Strength and toughness.
What are strength and toughnessin concrete?
Yeah.
Strength and toughnessare two fundamental properties
that play a significant role in the designand the longevity of materials
in this case of concrete that is usedin urban and infrastructure sector.
(01:51):
In that context, the strength is alsoone of the key mechanical properties
that we need to design rules
and structures, for example,for certain load bearing capacities.
Fracture toughness, on the other hand,is the energy required
to propagate an existing crack.
In other words, fracturesoffense is the critical resistance
(02:11):
above which the material will fracture.
This property is relevant to civilinfrastructure design,
given the degradationand the progressive damage
due to the mechanicaland environmental loading conditions
in various parts of the countryand various parts of the world.
And we're talking about traffic and carsand weather impacting materials here.
Absolutely.
For the next concept,I want to ask you about rheology.
(02:34):
How does rheology impact concretes? Right.
So rheology essentially is a field betweensolid mechanics and fluid mechanics
where in which people study solidsand liquids in rheology, people will study
deformable materials such as gelsand suspensions and colloidal systems
across various lengthscales and time scales.
(02:55):
There are materialsthat are neither perfect solids
or ideal liquids,and have some properties of both.
The questionpeople often ask in the field of rheology
consists of applying stress and measuringstrain, or vice versa, and asking
what does the materialor positive relationships
points to the properties are,and how do we understand them?
(03:18):
When it comes to cement and concrete,cement is a hydraulic powder,
meaning that it gains strengthover time by chemically reacting with one
that is mixed in in the processof concrete production.
Concretethen becomes a deformable material.
What it is in its fresh state.
During the production,it needs to be fresh
so it can be transported,it can be poured, and after a few hours,
(03:41):
concrete solidifies and gains the strengthdue to this hydraulic reaction.
So in studying the realogy of concrete,people study the deformation of concrete
by trying to quantify, for example,its viscosity, how it begins to flow,
how it seizes to flowthroughout the hydration over time.
So how does understanding the fluid statesin rheology help inform concretes
(04:03):
and how their use as they pore and dry?
So in the production of concrete,it is important to know how long
it would take for it to solidifyand how much working time you have.
The other challenges that you haveis in pouring and placing concrete.
It becomes important
when you design the pumping systems,when you design the extrusion systems.
(04:25):
When you design the process by whichthe concrete is produced in place,
because there is a limited working timeand the amount of energy
that you have to put in the system
to keep the concrete flowing,and even in the seal for placement.
Because the material solidifiesquickly over time,
it becomes important to understand thisas part of understanding
(04:46):
the concrete hydration,but also as part of understanding.
It's the form, ability, and the amountof energy you require to keep it in motion
and the fluid like beforeit becomes a solid like matter.
So that transition needs to be understoodin order for us
to have a production processthat is conducive to this material.
(05:07):
Okay.
The last concept
I want to ask you about what is additivemanufacturing in the world of concrete?
Of course, I o so additive manufacturingor colloquially as people may understand
it is 3D printing is a layerby layer and lamellar,
but is a process to fabricatematerials and structures
depending on the processing techniquesand material.
(05:29):
It involves flow.
It involves extrusion.
It involves deposition and solidification.
Therefore, it lends itself as aninteresting subject for logical studies.
Additive manufacturing also insome ways is a slightly more advanced
fabrication toolthan conventional processing ones,
in that it enables engineersand researchers to somehow control
(05:51):
the types of properties of the materialsand the interfaces locally,
thereby controlling the bulk propertiesand performance of the material.
You mentioned 3D printing concretes.
Does working in that form requirespecial treatment or special additives
in the cement mixture in thewhat becomes a concrete?
That's a great question.
To answer that, I need to contextualizethings a little more.
(06:14):
I think for most of the modern era,the construction techniques
that we've been usinghave remained limited.
Mostly due to the constraintsin the material properties itself.
The lack of progress.
I should add that in developingmore advanced tools and techniques
has demoted inventing new arrangementsof materials and structures.
(06:35):
We are at a time in materials scienceand construction technology
that the advance of new techniquescan be utilized to develop
new types of concrete, for examplethrough additive manufacturing.
These abilities to extendand customize the manufacturing process
allows us to go beyond, what currentlyis even possible to road to manufacturing.
(06:59):
And so there would be special aids,if you wish, right, in
how we formulated a matter of usinghow we design the fabrication,
methods and the tools that would then
synergistically contributeto the rethinking of the material itself.
So my wife worked in real estatefor a number of years,
and I'm sort of familiar with 3Dprinting concrete homes where they're
kind of following along the wall.
(07:20):
When you're working with that extrusionmethod, does
the concrete needtraditional reinforcements like rebar?
Right.
So this has been a common questionabout whether we should use additive
manufacturingto reimagine what concrete is
as a composite material, as a materialthat has different constituents.
(07:41):
Or we should adapted to whatwe currently consider what concrete is
or what reinforced concrete is, which isa composite of concrete and steel.
Rebars.
My take on thisis that we have the opportunity
to reimagine concreteas a new types of composite.
The ability to design materialsarrangement
lends itself to multi materialityand rethink what composite is.
(08:05):
Reinforced concrete.
Those only one type of compositethat we came up with
that we could envision to, for example,make high rise buildings.
Right.
We can now engineerspecific types of properties using
specific arrangements of a single materialor multiple materials.
And what we refer to as in my labas materials architecture.
These are materialswith purposeful arrangements
(08:27):
that have propertiesbetter than their constituents.
Thereby are materialsthat can be exploited
to rethink their constitutive properties.
That leads well into asking youabout architected techniques and design.
What are some of the ways
you are approaching reimagininghow you're using concrete?
So in our work,we often look into biological materials
(08:49):
with distinct design motifs that elicitunique one or more mechanical properties
or otherwise mutually exclusivecombinations of material properties.
For example. That's right. And toughness.
Nature is a great starting point to lookfor underlying mechanisms around which
relevant hypotheses for engineeringcounterparts can be postulated and probed.
(09:11):
But we still need the abilityto fabricate these materials.
So we advance our fabrication methodsthrough using additive
manufacturing techniques, throughadvancing robotic manufacturing processes
that enable these designs,so that we can formalize
and extend questions aroundhow does design controls the properties?
How can we learn from cleverand purposeful internal arrangements
(09:33):
of materials, spatial arrangementsof materials and space
in natural systems, and addresssome of the drawbacks
in mechanical properties of concreteor its lack of resistance to fracture.
How is the marine lab taking inspirationfrom these natural forms?
There are several architected
designs of inner arrangements of materialsthat we explore in our lab,
(09:55):
some of which are inspiredby the studies of biological materials.
I can give you 1 or 2 examples.
Here.
One is a nature like concrete
that was inspired by the innerarrangements of shells.
The shell consists of a brick and mortartype of architecture.
For the sake of visualization,
where the brick is a brittle material andthey seem to have 95% of the structure,
(10:19):
and the mortar is a biopolymermaking up the remaining 5%.
The toughness of this natural biologicalmaterial, the shell, the mother of pearl,
is several orders of magnitude largerthan its brittle aragonite.
Consider what we did was engineeringtough, nacre
like tabulated cementitiouspolymeric composites,
(10:40):
inspired by the brick and mortararrangement of mollusk shell,
we can use laser processingto engrave and build intentional defects
as a way to make the material stronger,or to entirely separate
the sheets of sand and paste into discretehexagonal topless.
You could use this process to createessentially those bricks
(11:01):
in a relatively fast rate.
We then used a lamination processto layer by layer.
For the composite, one can envisionan automated or additive process to do so.
The goal here was to developnot just the bi inspired geometry,
but to engineer the underlying tablet
sliding mechanism that we have learnedfrom nature and extending it
(11:21):
to the composite materials,which then led to enhancement
of the fracture toughness and ductilityby 17 and 19 folding respectively.
Compared to the monolithic cast materials.
That seems to be a pretty good returnon investment there with that statistic.
I believe so.
So one of the other pieces
I saw in your labwork is kind of this bone tube structure.
(11:42):
How is that structure beneficial?
To give you more context,human cortical bone, the denser outer
shell of human femurs providesthe strength and resistance to fracture.
Cortical bone is composed of tubelike Austrians embedded
in the organic matrix,surrounded by a weak interface.
The weak interfacessurrounding the Austrians provide them
(12:03):
mechanically for a facial crack passthat is a dissipative process,
meaning that you have to spend energy
to deflect the cracks to get the cracksto interact with the Austrians
instead of having one catastrophicbrittle failure.
Inspired by this toughening mechanismand facilitated by a hybrid 3D printing
and casting process, our study was aimedto engineer and architect
(12:27):
the tubular cement based materialswith a stepwise toughening mechanism.
However, that is not a trivial task
because it involves using a brittlematerial, a material that fractures
abruptly and engineering into it,and non brittle non catastrophic failure.
So one of the challenges ingeneral engineering brittle
construction materials,
(12:48):
which is a lot of construction materials,is that the failure is catastrophic.
And the key to the improvement lies
in the purposeful designof the internal architecture.
In this case by balancing the stresses
at the crack frontwith the overall mechanical properties
using the experimentaland theoretical approaches to fracture,
(13:10):
we demonstrated the competitionthat exists between the tube size
and the shape, as it affectsthe stress intensity at the correct it.
How does the stress intensifydue to the presence of these tubes
in front of the crack?
And by understanding this competitionand the balance between the tube size
and the shape, it appears
(13:30):
that we could engineer a stepwise crackingthat emerges from that.
And then this led to having aboutfive fold increase in fracture toughness
in these systems.
Again, compared to brittle materials.
So kind of thinking about next steps
and bringing these technologiesand techniques into the public sector.
What are the challenges scaling thesethings and their buildings and roads.
(13:51):
So there are many companiesand corporations
that are already workingon scaling up these additive technologies,
from laboratory small scaleto benchtop to a larger and larger scales.
At the same time,discoveries are being made
throughall the great work of our colleagues
in many academic institutionsaround the world and the United States.
In the lab in these areas,this has created really
(14:14):
an accelerated surge of discoveriesand rapid developments
in the area of sort of concreteand additive manufacturing and design.
That, to me is somewhat unprecedented.
Not always.
The discoveries in the labmay translate to the field
or the practitioner,or the market may not necessarily pick up
on every discoverythat is made around the world.
(14:35):
The market decidesthat this is not the case here.
When it comes to designand fabrication of new materials.
To give you more context, since 2010,the advancements
have continuedboth on the fundamental aspects
and in the fieldby scaling up the manufacturing techniques
from materials to componentsand from components to building envelope,
(14:57):
and even more recently, to even marinestructures at tens of meters in scale.
However, all that said, scaling up is notnecessarily the bottleneck in my opinion.
In many cases,there are several technical challenges
that has to be addressedand has to be invested.
Research grants or proposalshave to be made, many resources
and efforts and time has to be spenton addressing that.
(15:20):
But from a technology utility perspective,from a more abstract perspective,
I think we have the opportunity,if not the obligation, to reinvent
and redefinewhat materials and structures mean to us
and what are they going to look like
in the next decades,something we often underestimate,
I think, as a community,is that the role of scientific discovery,
(15:42):
whether it is through formalor exploratory approaches,
we may not need to build in the same waywe built today, in the next few decades.
And in order to sort of grapple
with that concept, or if we grapplewith that concept long enough,
I think we will realize that technologyhas a lot more to offer that allows us
to reinvent and re-envision the materialas we scale up to technologies.
(16:06):
And this is something that is oftentalked about in
developing the technology, not for today,but for a sustained period of time.
So thinking aboutsome of those fundamental advancements
that you've made,I want to ask you about your career award.
How has NSF supportimpacted your career to date?
Of course,I think NSF has a very crucial role
for academic institutionsand for discovery.
(16:29):
But I wanted to talk also a little bitabout the other types of roles
that NSF has.
I think demystifying what science isand what it is
not in an era when we witnessedsuch a rapid growth of new technologies,
I think it provides a baselinefor the society to adapt to that.
The evolution of everyday toolsand techniques that comes our way
(16:52):
in public way of processing informationand processing,
how to even change our day to dayhuman life.
So it even goes furtherbeyond what science is
and what is its impact on engineeringand on the society.
How does it affect our thinkingof our perception of the outside world?
Going back to NSF, I think the NationalScience Foundation plays a crucial role
(17:14):
promoting science and scientific discoveryby supporting researchers and engineers,
being able to pursue their questions,propose their questions, and pursued
answers for them, which in many casesleads to giant leaps in our understanding
of the physical worldand inventions that benefit their society.
This process allows for the trainingof the next generation of young thinkers
(17:37):
that work on a specific problemsand programs supported by the foundation.
We cannot answer the fundamental questionswe postulate every day
without the support of entitiessuch as National Science Foundation
that support research grants, that allowsfor such type of training and mentorship
for the young minds to take placethat would then carry the torch forward.
(17:57):
Thanks specifically,
would like to use this opportunityto thank the Engineering Civil
Infrastructure Program, which has alwaysbeen supportive in proposing new concepts
and ideas surrounding civilinfrastructure, materials and structures.
Advanced manufacturing programthat has really stepped in to allow
for transformationsin the manufacturing domain
(18:17):
to translateinto the infrastructure domain,
and specifically the Career award programthat I've received and has supported me
and the research of meand my group in the past three years.
It goes without saying that these effortshave had not only an impact on my career,
but the I hope that has had impact on the scientific community
(18:39):
and making very small step discoveries,but more importantly on the people,
on the students and postdocswho work on these types of projects
that can foster their creativityand sense of adventure.
So the last thing I want to ask you abouttoday is thinking about
the future of your research, and reallythe future of concrete in general.
Where do you see these thingsgoing over the next few years?
(19:01):
Well, thank you for asking the question.
I think materials and structuresthat we will design in the next ten,
20, 30 years won't bethe same as the ones we designed today.
I think I alluded to that earlier.
And so the meaning of concrete,the meaning of materials in general
may change in almost every aspectwe know today.
Whether you think of it as a material,whether you think of its mechanics
(19:24):
and fundamental aspects,where you think of it as a structure,
given the advancedmanufacturing techniques,
but also that as computational designcapabilities that are only going to grow.
So I think we're only scratchingthe surface also with not just
manufacturing and design computation,but also with robotics
in the world of concrete or construction
(19:44):
materials or more broadlyspeaking, in the world of engineering,
we may very wellbe at the cusp of the paradigm shift,
in my opinion, in the next several years,due to the growth
and the ability to move from automationto autonomy in robotics,
in construction,many of us have already been kicked off.
(20:04):
And so I think this is just the beginningof some new times in the field
as our tools of design, computationand autonomous robotics
fabrication advances,I think we might be able to redefine
these materialsand be able to engineer and infuse
and embed specific propertiesor properties
that were difficult to achieve beforeinto the materials of the future.
(20:29):
The properties that might be strange todayor to think of, but I think we will
be able to if we push our limits,we will be able to reinvent this material.
As for the research of my group,one particular aspect
that I try to incorporate in the thinkingof the group is the element of surprise,
and the elements of the counterintuitiveaspect of scientific discovery
(20:51):
that can hopefully surprise us every dayor every time, every year.
I think in sciencewe often pursue the known unknown.
It is the gateway to the unknown.
Unknown that we wish to stumble uponand to access, and doing
so by allowing the exploratory pathwaysoutside the formalized research process
(21:13):
that we has to incorporate, as a research group as well.
Special thanks to Reza Moini.
For The Discovery Files, I'm Nate Pottker.
You can watch video versions
of these conversations on our YouTubechannel by searching @NSFscience.
Please subscribe wherever you get podcastsand if you like our program,
share with a friendand consider leaving a review.
Discover how the U.S.
(21:33):
National Science Foundationis advancing research at NSF.gov
This is the Discovery Files podcast
from the US National Science Foundation.
Concrete is all around us.
It's in the buildings we live in.
The sidewalks we travel on
and the infrastructurethat allows us to have fresh water.
Concrete is a tough material,but over time and given
the right conditions,it can crack and crumble and fail.
Advances in material scienceand processing can
(00:25):
enhance concrete's resilience.
Recyclability and long term
durability, enabling significanteconomic and societal benefits.
We're joined by Reza Moini, assistantprofessor in the Department of Civil
and Environmental Engineering
and an affiliated facultyat the Andlinger Center for Energy
and the Environmentat Princeton University,
where his lab is developingresilient materials and structures
(00:45):
with bio inspired designsfor architected civil engineering projects
enabled by automated manufacturingrobotic systems.
Professor Moini,thank you for joining me today.
Thank you for having me.
I'd like to startwith just a bit of your history.
How did you become interested in concrete?
Right.
So my interest in concretestarted from my undergraduate studies
when I first took concretematerial science and technology.
(01:08):
It really fascinated me how complexthe organic chemistry of the most
commonly human made material was,and how the chemistry controlled
the material microstructure or thethe fabric of the material, if you wish.
That then governed in coursesthat I later learned the conservative
mechanical properties and the resultingperformance of these materials.
(01:30):
For the next few questions,
I want to ask you about a few conceptsthat are at play in your work.
Strength and toughness.
What are strength and toughnessin concrete?
Yeah.
Strength and toughnessare two fundamental properties
that play a significant role in the designand the longevity of materials
in this case of concrete that is usedin urban and infrastructure sector.
(01:51):
In that context, the strength is alsoone of the key mechanical properties
that we need to design rules
and structures, for example,for certain load bearing capacities.
Fracture toughness, on the other hand,is the energy required
to propagate an existing crack.
In other words, fracturesoffense is the critical resistance
(02:11):
above which the material will fracture.
This property is relevant to civilinfrastructure design,
given the degradationand the progressive damage
due to the mechanicaland environmental loading conditions
in various parts of the countryand various parts of the world.
And we're talking about traffic and carsand weather impacting materials here.
Absolutely.
For the next concept,I want to ask you about rheology.
(02:34):
How does rheology impact concretes? Right.
So rheology essentially is a field betweensolid mechanics and fluid mechanics
where in which people study solidsand liquids in rheology, people will study
deformable materials such as gelsand suspensions and colloidal systems
across various lengthscales and time scales.
(02:55):
There are materialsthat are neither perfect solids
or ideal liquids,and have some properties of both.
The questionpeople often ask in the field of rheology
consists of applying stress and measuringstrain, or vice versa, and asking
what does the materialor positive relationships
points to the properties are,and how do we understand them?
(03:18):
When it comes to cement and concrete,cement is a hydraulic powder,
meaning that it gains strengthover time by chemically reacting with one
that is mixed in in the processof concrete production.
Concretethen becomes a deformable material.
What it is in its fresh state.
During the production,it needs to be fresh
so it can be transported,it can be poured, and after a few hours,
(03:41):
concrete solidifies and gains the strengthdue to this hydraulic reaction.
So in studying the realogy of concrete,people study the deformation of concrete
by trying to quantify, for example,its viscosity, how it begins to flow,
how it seizes to flowthroughout the hydration over time.
So how does understanding the fluid statesin rheology help inform concretes
(04:03):
and how their use as they pore and dry?
So in the production of concrete,it is important to know how long
it would take for it to solidifyand how much working time you have.
The other challenges that you haveis in pouring and placing concrete.
It becomes important
when you design the pumping systems,when you design the extrusion systems.
(04:25):
When you design the process by whichthe concrete is produced in place,
because there is a limited working timeand the amount of energy
that you have to put in the system
to keep the concrete flowing,and even in the seal for placement.
Because the material solidifiesquickly over time,
it becomes important to understand thisas part of understanding
(04:46):
the concrete hydration,but also as part of understanding.
It's the form, ability, and the amountof energy you require to keep it in motion
and the fluid like beforeit becomes a solid like matter.
So that transition needs to be understoodin order for us
to have a production processthat is conducive to this material.
(05:07):
Okay.
The last concept
I want to ask you about what is additivemanufacturing in the world of concrete?
Of course, I o so additive manufacturingor colloquially as people may understand
it is 3D printing is a layerby layer and lamellar,
but is a process to fabricatematerials and structures
depending on the processing techniquesand material.
(05:29):
It involves flow.
It involves extrusion.
It involves deposition and solidification.
Therefore, it lends itself as aninteresting subject for logical studies.
Additive manufacturing also insome ways is a slightly more advanced
fabrication toolthan conventional processing ones,
in that it enables engineersand researchers to somehow control
(05:51):
the types of properties of the materialsand the interfaces locally,
thereby controlling the bulk propertiesand performance of the material.
You mentioned 3D printing concretes.
Does working in that form requirespecial treatment or special additives
in the cement mixture in thewhat becomes a concrete?
That's a great question.
To answer that, I need to contextualizethings a little more.
(06:14):
I think for most of the modern era,the construction techniques
that we've been usinghave remained limited.
Mostly due to the constraintsin the material properties itself.
The lack of progress.
I should add that in developingmore advanced tools and techniques
has demoted inventing new arrangementsof materials and structures.
(06:35):
We are at a time in materials scienceand construction technology
that the advance of new techniquescan be utilized to develop
new types of concrete, for examplethrough additive manufacturing.
These abilities to extendand customize the manufacturing process
allows us to go beyond, what currentlyis even possible to road to manufacturing.
(06:59):
And so there would be special aids,if you wish, right, in
how we formulated a matter of usinghow we design the fabrication,
methods and the tools that would then
synergistically contributeto the rethinking of the material itself.
So my wife worked in real estatefor a number of years,
and I'm sort of familiar with 3Dprinting concrete homes where they're
kind of following along the wall.
(07:20):
When you're working with that extrusionmethod, does
the concrete needtraditional reinforcements like rebar?
Right.
So this has been a common questionabout whether we should use additive
manufacturingto reimagine what concrete is
as a composite material, as a materialthat has different constituents.
(07:41):
Or we should adapted to whatwe currently consider what concrete is
or what reinforced concrete is, which isa composite of concrete and steel.
Rebars.
My take on thisis that we have the opportunity
to reimagine concreteas a new types of composite.
The ability to design materialsarrangement
lends itself to multi materialityand rethink what composite is.
(08:05):
Reinforced concrete.
Those only one type of compositethat we came up with
that we could envision to, for example,make high rise buildings.
Right.
We can now engineerspecific types of properties using
specific arrangements of a single materialor multiple materials.
And what we refer to as in my labas materials architecture.
These are materialswith purposeful arrangements
(08:27):
that have propertiesbetter than their constituents.
Thereby are materialsthat can be exploited
to rethink their constitutive properties.
That leads well into asking youabout architected techniques and design.
What are some of the ways
you are approaching reimagininghow you're using concrete?
So in our work,we often look into biological materials
(08:49):
with distinct design motifs that elicitunique one or more mechanical properties
or otherwise mutually exclusivecombinations of material properties.
For example. That's right. And toughness.
Nature is a great starting point to lookfor underlying mechanisms around which
relevant hypotheses for engineeringcounterparts can be postulated and probed.
(09:11):
But we still need the abilityto fabricate these materials.
So we advance our fabrication methodsthrough using additive
manufacturing techniques, throughadvancing robotic manufacturing processes
that enable these designs,so that we can formalize
and extend questions aroundhow does design controls the properties?
How can we learn from cleverand purposeful internal arrangements
(09:33):
of materials, spatial arrangementsof materials and space
in natural systems, and addresssome of the drawbacks
in mechanical properties of concreteor its lack of resistance to fracture.
How is the marine lab taking inspirationfrom these natural forms?
There are several architected
designs of inner arrangements of materialsthat we explore in our lab,
(09:55):
some of which are inspiredby the studies of biological materials.
I can give you 1 or 2 examples.
Here.
One is a nature like concrete
that was inspired by the innerarrangements of shells.
The shell consists of a brick and mortartype of architecture.
For the sake of visualization,
where the brick is a brittle material andthey seem to have 95% of the structure,
(10:19):
and the mortar is a biopolymermaking up the remaining 5%.
The toughness of this natural biologicalmaterial, the shell, the mother of pearl,
is several orders of magnitude largerthan its brittle aragonite.
Consider what we did was engineeringtough, nacre
like tabulated cementitiouspolymeric composites,
(10:40):
inspired by the brick and mortararrangement of mollusk shell,
we can use laser processingto engrave and build intentional defects
as a way to make the material stronger,or to entirely separate
the sheets of sand and paste into discretehexagonal topless.
You could use this process to createessentially those bricks
(11:01):
in a relatively fast rate.
We then used a lamination processto layer by layer.
For the composite, one can envisionan automated or additive process to do so.
The goal here was to developnot just the bi inspired geometry,
but to engineer the underlying tablet
sliding mechanism that we have learnedfrom nature and extending it
(11:21):
to the composite materials,which then led to enhancement
of the fracture toughness and ductilityby 17 and 19 folding respectively.
Compared to the monolithic cast materials.
That seems to be a pretty good returnon investment there with that statistic.
I believe so.
So one of the other pieces
I saw in your labwork is kind of this bone tube structure.
(11:42):
How is that structure beneficial?
To give you more context,human cortical bone, the denser outer
shell of human femurs providesthe strength and resistance to fracture.
Cortical bone is composed of tubelike Austrians embedded
in the organic matrix,surrounded by a weak interface.
The weak interfacessurrounding the Austrians provide them
(12:03):
mechanically for a facial crack passthat is a dissipative process,
meaning that you have to spend energy
to deflect the cracks to get the cracksto interact with the Austrians
instead of having one catastrophicbrittle failure.
Inspired by this toughening mechanismand facilitated by a hybrid 3D printing
and casting process, our study was aimedto engineer and architect
(12:27):
the tubular cement based materialswith a stepwise toughening mechanism.
However, that is not a trivial task
because it involves using a brittlematerial, a material that fractures
abruptly and engineering into it,and non brittle non catastrophic failure.
So one of the challenges ingeneral engineering brittle
construction materials,
(12:48):
which is a lot of construction materials,is that the failure is catastrophic.
And the key to the improvement lies
in the purposeful designof the internal architecture.
In this case by balancing the stresses
at the crack frontwith the overall mechanical properties
using the experimentaland theoretical approaches to fracture,
(13:10):
we demonstrated the competitionthat exists between the tube size
and the shape, as it affectsthe stress intensity at the correct it.
How does the stress intensifydue to the presence of these tubes
in front of the crack?
And by understanding this competitionand the balance between the tube size
and the shape, it appears
(13:30):
that we could engineer a stepwise crackingthat emerges from that.
And then this led to having aboutfive fold increase in fracture toughness
in these systems.
Again, compared to brittle materials.
So kind of thinking about next steps
and bringing these technologiesand techniques into the public sector.
What are the challenges scaling thesethings and their buildings and roads.
(13:51):
So there are many companiesand corporations
that are already workingon scaling up these additive technologies,
from laboratory small scaleto benchtop to a larger and larger scales.
At the same time,discoveries are being made
throughall the great work of our colleagues
in many academic institutionsaround the world and the United States.
In the lab in these areas,this has created really
(14:14):
an accelerated surge of discoveriesand rapid developments
in the area of sort of concreteand additive manufacturing and design.
That, to me is somewhat unprecedented.
Not always.
The discoveries in the labmay translate to the field
or the practitioner,or the market may not necessarily pick up
on every discoverythat is made around the world.
(14:35):
The market decidesthat this is not the case here.
When it comes to designand fabrication of new materials.
To give you more context, since 2010,the advancements
have continuedboth on the fundamental aspects
and in the fieldby scaling up the manufacturing techniques
from materials to componentsand from components to building envelope,
(14:57):
and even more recently, to even marinestructures at tens of meters in scale.
However, all that said, scaling up is notnecessarily the bottleneck in my opinion.
In many cases,there are several technical challenges
that has to be addressedand has to be invested.
Research grants or proposalshave to be made, many resources
and efforts and time has to be spenton addressing that.
(15:20):
But from a technology utility perspective,from a more abstract perspective,
I think we have the opportunity,if not the obligation, to reinvent
and redefinewhat materials and structures mean to us
and what are they going to look like
in the next decades,something we often underestimate,
I think, as a community,is that the role of scientific discovery,
(15:42):
whether it is through formalor exploratory approaches,
we may not need to build in the same waywe built today, in the next few decades.
And in order to sort of grapple
with that concept, or if we grapplewith that concept long enough,
I think we will realize that technologyhas a lot more to offer that allows us
to reinvent and re-envision the materialas we scale up to technologies.
(16:06):
And this is something that is oftentalked about in
developing the technology, not for today,but for a sustained period of time.
So thinking aboutsome of those fundamental advancements
that you've made,I want to ask you about your career award.
How has NSF supportimpacted your career to date?
Of course,I think NSF has a very crucial role
for academic institutionsand for discovery.
(16:29):
But I wanted to talk also a little bitabout the other types of roles
that NSF has.
I think demystifying what science isand what it is
not in an era when we witnessedsuch a rapid growth of new technologies,
I think it provides a baselinefor the society to adapt to that.
The evolution of everyday toolsand techniques that comes our way
(16:52):
in public way of processing informationand processing,
how to even change our day to dayhuman life.
So it even goes furtherbeyond what science is
and what is its impact on engineeringand on the society.
How does it affect our thinkingof our perception of the outside world?
Going back to NSF, I think the NationalScience Foundation plays a crucial role
(17:14):
promoting science and scientific discoveryby supporting researchers and engineers,
being able to pursue their questions,propose their questions, and pursued
answers for them, which in many casesleads to giant leaps in our understanding
of the physical worldand inventions that benefit their society.
This process allows for the trainingof the next generation of young thinkers
(17:37):
that work on a specific problemsand programs supported by the foundation.
We cannot answer the fundamental questionswe postulate every day
without the support of entitiessuch as National Science Foundation
that support research grants, that allowsfor such type of training and mentorship
for the young minds to take placethat would then carry the torch forward.
(17:57):
Thanks specifically,
would like to use this opportunityto thank the Engineering Civil
Infrastructure Program, which has alwaysbeen supportive in proposing new concepts
and ideas surrounding civilinfrastructure, materials and structures.
Advanced manufacturing programthat has really stepped in to allow
for transformationsin the manufacturing domain
(18:17):
to translateinto the infrastructure domain,
and specifically the Career award programthat I've received and has supported me
and the research of meand my group in the past three years.
It goes without saying that these effortshave had not only an impact on my career,
but the I hope that has had impact on the scientific community
(18:39):
and making very small step discoveries,but more importantly on the people,
on the students and postdocswho work on these types of projects
that can foster their creativityand sense of adventure.
So the last thing I want to ask you abouttoday is thinking about
the future of your research, and reallythe future of concrete in general.
Where do you see these thingsgoing over the next few years?
(19:01):
Well, thank you for asking the question.
I think materials and structuresthat we will design in the next ten,
20, 30 years won't bethe same as the ones we designed today.
I think I alluded to that earlier.
And so the meaning of concrete,the meaning of materials in general
may change in almost every aspectwe know today.
Whether you think of it as a material,whether you think of its mechanics
(19:24):
and fundamental aspects,where you think of it as a structure,
given the advancedmanufacturing techniques,
but also that as computational designcapabilities that are only going to grow.
So I think we're only scratchingthe surface also with not just
manufacturing and design computation,but also with robotics
in the world of concrete or construction
(19:44):
materials or more broadlyspeaking, in the world of engineering,
we may very wellbe at the cusp of the paradigm shift,
in my opinion, in the next several years,due to the growth
and the ability to move from automationto autonomy in robotics,
in construction,many of us have already been kicked off.
(20:04):
And so I think this is just the beginningof some new times in the field
as our tools of design, computationand autonomous robotics
fabrication advances,I think we might be able to redefine
these materialsand be able to engineer and infuse
and embed specific propertiesor properties
that were difficult to achieve beforeinto the materials of the future.
(20:29):
The properties that might be strange todayor to think of, but I think we will
be able to if we push our limits,we will be able to reinvent this material.
As for the research of my group,one particular aspect
that I try to incorporate in the thinkingof the group is the element of surprise,
and the elements of the counterintuitiveaspect of scientific discovery
(20:51):
that can hopefully surprise us every dayor every time, every year.
I think in sciencewe often pursue the known unknown.
It is the gateway to the unknown.
Unknown that we wish to stumble uponand to access, and doing
so by allowing the exploratory pathwaysoutside the formalized research process
(21:13):
that we has to incorporate, as a research group as well.
Special thanks to Reza Moini.
For The Discovery Files, I'm Nate Pottker.
You can watch video versions
of these conversations on our YouTubechannel by searching @NSFscience.
Please subscribe wherever you get podcastsand if you like our program,
share with a friendand consider leaving a review.
Discover how the U.S.
(21:33):
National Science Foundationis advancing research at NSF.gov
Popular Podcasts
Dateline NBC
Current and classic episodes, featuring compelling true-crime mysteries, powerful documentaries and in-depth investigations. Follow now to get the latest episodes of Dateline NBC completely free, or subscribe to Dateline Premium for ad-free listening and exclusive bonus content: DatelinePremium.com
24/7 News: The Latest
The latest news in 4 minutes updated every hour, every day.
Therapy Gecko
An unlicensed lizard psychologist travels the universe talking to strangers about absolutely nothing. TO CALL THE GECKO: follow me on https://www.twitch.tv/lyleforever to get a notification for when I am taking calls. I am usually live Mondays, Wednesdays, and Fridays but lately a lot of other times too. I am a gecko.