April 11, 2026 • 22 mins
Concrete is one of the most widely used and oldest building materials.
From Ancient Romans to your average tradie, everyone has used it in some capacity.
Ralf Kessel from Concrete NZ joins Pete to discuss the intricacies of this iconic building material, and how innovations in concrete are making it sturdier, cheaper and more eco-friendly.
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Speaker 1 (00:06):
You're listening to the Resident Builder podcast with Peter Wolfcamp
from News Talks.
Speaker 2 (00:11):
At Bay right this morning. On the program, I mentioned
earlier a couple of weeks months ago Ralph Kessel from
Concrete New Zealand joined us and it was a great
interview then, and it's a fairly big topic, so I thought,
well let's get Ralph back and it despite great pleasure
to welcome back to the program. Ralph Kessel. Good morning
to you.
Speaker 3 (00:31):
Yeah, good morning, Pete. Thanks for having me again.
Speaker 2 (00:33):
It's a pleasure. Hey, look just quickly, Concrete en z
what is it? What does that body represent?
Speaker 3 (00:43):
So we are the organ speaking for concrete, so we
ensure that concrete is used as the best possibilities for
on revealing this. So we also look after the education
in parts of education for ter free education, institute, universities,
(01:04):
but also building or fishers, the building force on the ground,
so we have a lot of courses for construction workers,
for technicians, et cetera. So basically we are the organ
representing concrete all over all over the place is if.
Speaker 2 (01:23):
You want so, right, So it's sort of like the
manufacturers as well as the users and ensuring that the
standards are maintained as well, so that's why you're in
the training space.
Speaker 3 (01:33):
Yes, absolutely standards as well. We have sector groups Amazonry Block,
sector groups of Cement Group. We have also a Learned
Society where we combine the knowledge of practicing engineers and architects.
So we are definitely an all around tool for concrete
if you want so.
Speaker 2 (01:55):
Right, excellent Now, one of the things that I was
quite keen to talk about, and we've we've I've invited
people to send some Texan so we might do some
general Q and A with a whole random selection of
texts if we have time this morning. But one of
the things that I guess has been a debate for
a number of years is as we move as a sector,
(02:18):
the construction sector in general wants to move to a
lower carbon future, right, And one of the criticisms and
sometimes you talk to people who are really really passionate
about sustainability and protecting the environment and they look at
concrete and they go, it's just got too much embodied
(02:39):
carbon because of its manufacturer. And I'm not going to
use concrete because I want a sustainable building. That's probably
you've probably been bailed up at conferences and so on
where people want to challenge concrete. The other part of
that is that the way in which concrete is manufactured
today with the various components, there are some changes there.
(03:04):
So when you see an ad that said is this
is a low carbon concrete, what are they talking about.
Speaker 3 (03:11):
Well, what I have mentioned in the last interview that
we must look at replacing cement because cement is the culbrat.
Cement about eighty five percent emissions of the total of concrete.
And here we replace cement with substitutes such as fly
ash and volcanic ash which is a natural product, but
(03:37):
also slack, which is a reminder from steel production. So
the byproducts from industry would other guys otherwise go to
land field, but we chuck it in the concrete and
reduce the emissions significantly. But what we also see there
has been further progress in reducing the emissions to the
benefit of all listeners. Structural concrete is always reinforced, usually
(04:01):
with steel bars. Why is it. Concrete performs well under
compression but poorly intentioned. So steel, on the other hand,
performs very well intension. So we combine those two materials
and so a structural concrete building always has steel reinforcement,
and until recently, the carbon footprint of steel was significant,
(04:23):
about four ton of carbon dioxide per ton of steel,
when concrete comes with just eighty two hundred kilogram of
carbon dioxide pertons. But New Zealand Steel has now built
a new electric arc furnace. Not sure if you're thurden
through the media, yeah, and that enables the production of
(04:44):
low carbon steel and as a result, the carbon footprint
of the rebar four concrete can be reduced from around
four toon to five hundred kilogram.
Speaker 2 (04:55):
So because numbers like that, you know, sometimes they tend
to we hear them in the it's in one ear
and out the other. But what you're saying there is
four tons, so four thousand kilo to five hundred.
Speaker 3 (05:09):
Yeah, yeah, But I think it's important to put this
into perspective. So in a typical concrete slab on grade,
steel accounts for only about let's say five percent of
the volume and concrete is ninety five to ninety six.
But nevertheless, under previous production methods with the old FORG
(05:30):
for ton, approximately two thirds of the embodied emissions of
reinforced concrete came from the steel and only one third
from the concrete itself, but by reducing steel emissions by
about eighty seven percent, the overall emissions of reinforced concrete
can be reduced by fifty to sixty percent. So looking
(05:53):
at a thirty the MPa concrete, that will reduce the
emissions per cubic meter from around five hundred and fifty
kilogram to two hundred and fifty kilogram, and these values
are comparable to the emissions of timber the cub meter.
If biogenic carbon is excluded right now should possibly explain
what biogenic carbon is. The biogenic carbon refers to carbon
(06:16):
temporarily stored in materials like timber. So there's a chemical
process that the carbon dioxide is taken up by the timber,
by the cells, and it says, but this storage is
short term. Once the material decays or is burned, the
carbon is released back into the atmosphere. So we're talking
about the end of life of the building. Maybe after
(06:39):
twenty maybe after fifty or after sixty years, that carbon
will be released back into the atmosphere. And concrete, by contrast,
is recognized by the Intergovernmental Panel on Climate Change in
twenty twenty one, can store carbon permanently through carbonations so
the carbon dioxide reacts with calcium and oxygen to form
(07:06):
club to carbonate, which is limestone, so which locks the
carbon into the material for the long term. This is
not that much, but it's better than nothing. And with
this combination of cement replacement, low carbon steel and natural carbonation,
we are definitely certain we get to carbon netcover zero
(07:27):
by twenty fifty with So that's our vision. And also
coming back to your earlier question, what is concrete New Zealand,
we also have brought together all our concrete manufacturers to
assign up to this vision. And maybe one important thing
I've forgot asked what's concrete the Zealand And we have
(07:51):
also the Concrete New Zealand Planted Audit Scheme. So what
many people may not know is that the majority of
concrete New Zealand is independently checked through this plant Audit scheme.
So through us concrete reduced by our members is regular
tested under the scheme, which gives the engineers the certainty
(08:13):
that the concrete is as specified. So otherwise you would
be exposed to a costly and time consuming audit for
concrete quality to each thing a project. So in simple terms,
the scheme gives you confidence that the concrete supplied will
perform as specified. At the moment, there are two hundred
plans nationwide signed up to the scheme. And yes, this
(08:37):
is also a very important part we do as cong
New Zealand. We check our members, We check the quality.
Speaker 2 (08:44):
Which I think is actually you know, because often we
find that that companies with greatest respect will make claims right,
you know, this product performs this way, or it's of
the standard, or it has this environmental you know, qualification
to it, and then you go so prove it and
(09:05):
sometimes it's like, actually, we can't really prove it. And
what you're saying is in terms of you know, because
in the end concrete we often use. This is just
from a practical point of view. You know that it's
often the foundation of many buildings, right, so if as
a carpenter, I might take care of all of the
timber work above it, but I need to know and
(09:26):
my clients need to know that the concrete that went
into the foundations and the slab is going to be
is going to perform as we expect it to in
terms of strength and durability and so on.
Speaker 3 (09:37):
Yeah, you're absolutely right, So that relates to the quality.
But that also relates to the claims we we spread
in regards to carbon emissions. Sure, so the carbon emission claims,
they are supported by EPDs, so called environmental product declarations,
(09:58):
which are a third party, independent, third party checked statements data.
So epeds not only cover carbon dioxide, but they cover
all kinds of gases because we have to consider we
have to see the environment holistically, so we have to
(10:20):
think of biodiversity. There are other gases which are maybe
not bad or not contributing to climate change, but they
would be bad for our respiratory ragons, you know. So,
and most of the gases are covered in EPDs. There
are several countries companies in the country who are able
(10:43):
to conduct these right, and it's also verified, And you're
absolutely right, it has to be scientifically proven that our
claims are true and hold up to scrutinity.
Speaker 2 (10:59):
Absolutely, We're going to take a break in a moment,
but before we do, the thought that's in my mind
is also, you know, a big part of of sustainability
is around controlling waste, and so I've got two quick
questions on that. One is, you know, let's say you've
ordered some concrete, you've done the drive and then you
realize that you didn't quite need as much as you needed,
(11:21):
and so there's half a cubic meter or so still
left in the truck. What happens to that when it
goes back to the plant, Like, is any of that
able to be not reused because obviously it's going to
go off, but the aggregate that's in there and that
sort of thing, what happens there is that just waste
or is it able to be reused in some way?
Speaker 3 (11:41):
Well, in the past it has been waste. But since
the last six to seven years, and we have measures
to take the left of a concrete yes, and they
are basically cast into forms, and the result is we
have large, maybe oversized blocks.
Speaker 1 (12:01):
Yep.
Speaker 3 (12:01):
It's going to be reduced for coastal production, but also
for organizing a young out on the farm where I
just want to have your you know, storage sorted that
has been done. And because the architect or engineer or
build our contract or whatever need enough concrete on site,
(12:22):
they always order a little bit more, yep, a little
bit of surplus to not run out of concrete suddenly.
So there's always a leftover and our plans have take
the necessary steps and yeah, all the leftovers maybe cards
into forms back on the plant.
Speaker 1 (12:40):
Right.
Speaker 2 (12:41):
Well that's and actually it's a bigger question than we've
got time for right now, So take a short break.
I want to look at sort of end of life,
what we might be able to do with concrete end
of life. So Ralph Kessel from Concrete, New Zealand is
my guest this morning. It is eight point twenty with
news Talk set B so joining me this morning, Genus
with his time this morning, Ralph Kessel from Concrete, New Zealand.
(13:02):
Thanks again for joining us. Now I'll try and hit
a couple of texts in a minute. But the other
thing that I think has been an interesting change is
in a sense the recycling reuse of left either demolition,
concrete or ensan. So are we seeing more providers being
able to accept demolition material. You know, I've cut up
(13:27):
part of a driveway and I need to dispose of that.
Whereas it used to go just hard fill to landfill,
it's now being repurposed.
Speaker 3 (13:37):
Yes, there are definitely schemes in place and being Auckland
Green Gorilla for example, it's one or larger. They take
conc they get to take construction waste, and amongst that
there's concrete waste, and as I mentioned in my last
interview that the bulk of it will be used for hardfire,
for drainable backfill around properties, et cetera. But were just
(14:03):
ending with ways management before the break and so the
use of repurposed demolition waste and also less over cars
into blocks, it doesn't end there. So we have to
(14:23):
look at the production of concrete as well, where we
have a lot of heat to generate for the kill.
That's actually where the emissions come from, from the kiln,
from the process where we manufacture the cement. So the
one part of the emissions comes from a chemical process
within the kill when we separate the line from the
(14:44):
limestone to gain the cement, and the other part is
the fossil fuel coal which we use to heat the
kilns up to fourteen hundred degrees. And here we use
now waste materials as well for heating the kilden. The
first one is waste timber and the second one is
actually old car tires. And I recall that I think
(15:08):
you may have heard about that the bulk of old
characterires in New Zealand is used by the cement industry
where they replace the coal as a fuel. This scheme
has also reduced illegal tire dumpig buy around fifty percent.
And I should mention that our cemental industry has gas
cleaning filter systems in place to manage all emissions responsibly.
(15:31):
So there's a lot going on in achieving also not
just CARBN zero by twenty fifty, but also to achieve
a fully operating circular economy within the concrete industry.
Speaker 2 (15:44):
Because sometimes people will ask, well, if I you know
there used to be a quarry near me that would
take you know, liftover concrete or waste concrete. You cut
up a driveway, put it on the trailer, dump it
there they'd seen it through the crusher and turn it
into hard filt, which was great because there is a
challenge with the idea of crushing used concrete and reusing
(16:08):
the aggregate and new concrete, isn't there.
Speaker 3 (16:11):
Yes, that can be done as well, but you have
to be careful once if you don't know the original
location or source of that aggregaty, it may be more
difficult to understand the final quality and maybe even the
compressive strength, which we have to test anyway. But so
it's important that you know the source of the aggregot,
(16:33):
and it's also time consuming and energy consuming to get
just really the pebbles and the aggregots away from some
smontitious parts. So that's not ideals. So what we see
more and more is that the concrete demolition wave is
crushed and then used for for backfield under rolling and
(16:57):
around also for coastal protection partly. So there are lots
of things happening.
Speaker 2 (17:04):
And I guess what that does is substitutes, let's say,
virgin material, you know, from a quarry going directly from
a quarry to just being the base course that my
driveway sits on. I'm better off using crush concrete recycled
for that type of purpose.
Speaker 3 (17:21):
Yeah, absolutely, I mean the recycled material that's all very
professionally done. It will will be run through sieves so
we get our gap sizes, whatever pebble sizes they need
for that project. So you can choose really from the
shelves that various gap sizes for your projects from recycled material.
(17:44):
That's definitely happening. But the other thing which you may
find interesting, that we see new construction ways and a
true if you heard about three D printing.
Speaker 2 (17:54):
Yep, the factory. I've seen one of them.
Speaker 3 (17:57):
Absolutely, yes, so, and that's three DE concrete printing is
definitely becoming more mainstream, at least in the US.
Speaker 2 (18:05):
Sure.
Speaker 3 (18:05):
Well, what we see there is that three D printed
homes are now cost neutral already or even cheaper than
timber framed houses. They're also popular because theyre withstand weather events,
which is becoming increasingly important. As a reminder, you may
just look outside of your window. They are wind and
(18:27):
noise resistant too, which you really notice on lust three days.
And then as climate change brings more fire risks, these
concrete houses are naturally fire resistant. We are for comparison,
one hundred millimeters concrete world gives you around sixty minutes
of fire resistant. Typically, structure wards are even thicker one
(18:49):
hundred and fifty millimeter, which gives you almost two hours.
So that gives people a good shelter and peace of
mind and also combating climate change. We shall use local materials,
so concrete is a local material. We don't have packaging.
There are no large shipping distances.
Speaker 2 (19:07):
Right yeah.
Speaker 3 (19:09):
So, and the other thing which I find, at least
in the US, that some people like to have a
distinctive home, and a three DEEP printed home is definitely
a very distinctive home. So this is another reason why
three D printed houses pick up in the US. So
in New Zealand at the moment there are so far
(19:29):
only four projects, including two in Auckland, two in Hamilton,
and one of them as a daycare center, so it
takes a better while until we get to that stage.
So the mix is always a little bit different, small viscous,
it has less, smaller aggregat to be fed into the
(19:52):
three D printer, et cetera. But I see that definitely coming.
And three D printing means less people on the ground,
but it also means less injuries, less health and safety
ri so just clean a building side. We will see
this in the future. It's not quite there where we
(20:13):
have it in the US and maybe other European countries.
It's definitely coming, and.
Speaker 2 (20:20):
I've been lucky enough to visit the Auckland one and
one of the ones in Hamilton, so it is really
it's just that you know, we've got the space to go. Hey,
is there space for innovation and is there more than
just one way to do everything? You know? And I
think that's where it is really really exciting. Excuse me,
just before we go, I've got this text from Darren. Hey,
(20:43):
We've just purchased thirty of those leftover blocks, nine hundred
by nine hundred and nine hundred. They've got a lifting
hoc on them. We utilize them on the Farmer's Flood
Protection and bank Stabilization said. We paid ten bucks each
for them, which makes them very cost effective even after
the freight. So there you go. That's a classic example
of what you're saying. You know, trucks returning with some
surplus concrete gets poured into forms that then and it
(21:07):
goes out to farms and yards and storage facilities and
all sorts. So it is really I think it's I
think it's really exciting when an industry responds to the challenges.
And you know, in this sense, we all know for
very good reasons. We've got a concern around carbon and
the carbon used in construction and it's a huge part
(21:29):
of the amount of carbon that we use in New Zealand. Right,
so every part of the construction sector needs to address
it's the way in which it deals with that, and
obviously concrete New Zealand as part of that as well. Ralph,
I think we're going to get you back and have
a bit more of a chat in a couple of
weeks or a few months or so as well. But
(21:49):
my thanks to you for giving up mer time on
a Sunday morning. Really appreciate it this morning.
Speaker 3 (21:54):
Thank you very much, Being lovely Journey.
Speaker 1 (21:56):
For more from The Residence Builder with Peter Wolfcamp, listen
live to news talks that'd be on Sunday mornings from Sex,
or follow the podcast on iHeartRadio.
You're listening to the Resident Builder podcast with Peter Wolfcamp
from News Talks.
Speaker 2 (00:11):
At Bay right this morning. On the program, I mentioned
earlier a couple of weeks months ago Ralph Kessel from
Concrete New Zealand joined us and it was a great
interview then, and it's a fairly big topic, so I thought,
well let's get Ralph back and it despite great pleasure
to welcome back to the program. Ralph Kessel. Good morning
to you.
Speaker 3 (00:31):
Yeah, good morning, Pete. Thanks for having me again.
Speaker 2 (00:33):
It's a pleasure. Hey, look just quickly, Concrete en z
what is it? What does that body represent?
Speaker 3 (00:43):
So we are the organ speaking for concrete, so we
ensure that concrete is used as the best possibilities for
on revealing this. So we also look after the education
in parts of education for ter free education, institute, universities,
(01:04):
but also building or fishers, the building force on the ground,
so we have a lot of courses for construction workers,
for technicians, et cetera. So basically we are the organ
representing concrete all over all over the place is if.
Speaker 2 (01:23):
You want so, right, So it's sort of like the
manufacturers as well as the users and ensuring that the
standards are maintained as well, so that's why you're in
the training space.
Speaker 3 (01:33):
Yes, absolutely standards as well. We have sector groups Amazonry Block,
sector groups of Cement Group. We have also a Learned
Society where we combine the knowledge of practicing engineers and architects.
So we are definitely an all around tool for concrete
if you want so.
Speaker 2 (01:55):
Right, excellent Now, one of the things that I was
quite keen to talk about, and we've we've I've invited
people to send some Texan so we might do some
general Q and A with a whole random selection of
texts if we have time this morning. But one of
the things that I guess has been a debate for
a number of years is as we move as a sector,
(02:18):
the construction sector in general wants to move to a
lower carbon future, right, And one of the criticisms and
sometimes you talk to people who are really really passionate
about sustainability and protecting the environment and they look at
concrete and they go, it's just got too much embodied
(02:39):
carbon because of its manufacturer. And I'm not going to
use concrete because I want a sustainable building. That's probably
you've probably been bailed up at conferences and so on
where people want to challenge concrete. The other part of
that is that the way in which concrete is manufactured
today with the various components, there are some changes there.
(03:04):
So when you see an ad that said is this
is a low carbon concrete, what are they talking about.
Speaker 3 (03:11):
Well, what I have mentioned in the last interview that
we must look at replacing cement because cement is the culbrat.
Cement about eighty five percent emissions of the total of concrete.
And here we replace cement with substitutes such as fly
ash and volcanic ash which is a natural product, but
(03:37):
also slack, which is a reminder from steel production. So
the byproducts from industry would other guys otherwise go to
land field, but we chuck it in the concrete and
reduce the emissions significantly. But what we also see there
has been further progress in reducing the emissions to the
benefit of all listeners. Structural concrete is always reinforced, usually
(04:01):
with steel bars. Why is it. Concrete performs well under
compression but poorly intentioned. So steel, on the other hand,
performs very well intension. So we combine those two materials
and so a structural concrete building always has steel reinforcement,
and until recently, the carbon footprint of steel was significant,
(04:23):
about four ton of carbon dioxide per ton of steel,
when concrete comes with just eighty two hundred kilogram of
carbon dioxide pertons. But New Zealand Steel has now built
a new electric arc furnace. Not sure if you're thurden
through the media, yeah, and that enables the production of
(04:44):
low carbon steel and as a result, the carbon footprint
of the rebar four concrete can be reduced from around
four toon to five hundred kilogram.
Speaker 2 (04:55):
So because numbers like that, you know, sometimes they tend
to we hear them in the it's in one ear
and out the other. But what you're saying there is
four tons, so four thousand kilo to five hundred.
Speaker 3 (05:09):
Yeah, yeah, But I think it's important to put this
into perspective. So in a typical concrete slab on grade,
steel accounts for only about let's say five percent of
the volume and concrete is ninety five to ninety six.
But nevertheless, under previous production methods with the old FORG
(05:30):
for ton, approximately two thirds of the embodied emissions of
reinforced concrete came from the steel and only one third
from the concrete itself, but by reducing steel emissions by
about eighty seven percent, the overall emissions of reinforced concrete
can be reduced by fifty to sixty percent. So looking
(05:53):
at a thirty the MPa concrete, that will reduce the
emissions per cubic meter from around five hundred and fifty
kilogram to two hundred and fifty kilogram, and these values
are comparable to the emissions of timber the cub meter.
If biogenic carbon is excluded right now should possibly explain
what biogenic carbon is. The biogenic carbon refers to carbon
(06:16):
temporarily stored in materials like timber. So there's a chemical
process that the carbon dioxide is taken up by the timber,
by the cells, and it says, but this storage is
short term. Once the material decays or is burned, the
carbon is released back into the atmosphere. So we're talking
about the end of life of the building. Maybe after
(06:39):
twenty maybe after fifty or after sixty years, that carbon
will be released back into the atmosphere. And concrete, by contrast,
is recognized by the Intergovernmental Panel on Climate Change in
twenty twenty one, can store carbon permanently through carbonations so
the carbon dioxide reacts with calcium and oxygen to form
(07:06):
club to carbonate, which is limestone, so which locks the
carbon into the material for the long term. This is
not that much, but it's better than nothing. And with
this combination of cement replacement, low carbon steel and natural carbonation,
we are definitely certain we get to carbon netcover zero
(07:27):
by twenty fifty with So that's our vision. And also
coming back to your earlier question, what is concrete New Zealand,
we also have brought together all our concrete manufacturers to
assign up to this vision. And maybe one important thing
I've forgot asked what's concrete the Zealand And we have
(07:51):
also the Concrete New Zealand Planted Audit Scheme. So what
many people may not know is that the majority of
concrete New Zealand is independently checked through this plant Audit scheme.
So through us concrete reduced by our members is regular
tested under the scheme, which gives the engineers the certainty
(08:13):
that the concrete is as specified. So otherwise you would
be exposed to a costly and time consuming audit for
concrete quality to each thing a project. So in simple terms,
the scheme gives you confidence that the concrete supplied will
perform as specified. At the moment, there are two hundred
plans nationwide signed up to the scheme. And yes, this
(08:37):
is also a very important part we do as cong
New Zealand. We check our members, We check the quality.
Speaker 2 (08:44):
Which I think is actually you know, because often we
find that that companies with greatest respect will make claims right,
you know, this product performs this way, or it's of
the standard, or it has this environmental you know, qualification
to it, and then you go so prove it and
(09:05):
sometimes it's like, actually, we can't really prove it. And
what you're saying is in terms of you know, because
in the end concrete we often use. This is just
from a practical point of view. You know that it's
often the foundation of many buildings, right, so if as
a carpenter, I might take care of all of the
timber work above it, but I need to know and
(09:26):
my clients need to know that the concrete that went
into the foundations and the slab is going to be
is going to perform as we expect it to in
terms of strength and durability and so on.
Speaker 3 (09:37):
Yeah, you're absolutely right, So that relates to the quality.
But that also relates to the claims we we spread
in regards to carbon emissions. Sure, so the carbon emission claims,
they are supported by EPDs, so called environmental product declarations,
(09:58):
which are a third party, independent, third party checked statements data.
So epeds not only cover carbon dioxide, but they cover
all kinds of gases because we have to consider we
have to see the environment holistically, so we have to
(10:20):
think of biodiversity. There are other gases which are maybe
not bad or not contributing to climate change, but they
would be bad for our respiratory ragons, you know. So,
and most of the gases are covered in EPDs. There
are several countries companies in the country who are able
(10:43):
to conduct these right, and it's also verified, And you're
absolutely right, it has to be scientifically proven that our
claims are true and hold up to scrutinity.
Speaker 2 (10:59):
Absolutely, We're going to take a break in a moment,
but before we do, the thought that's in my mind
is also, you know, a big part of of sustainability
is around controlling waste, and so I've got two quick
questions on that. One is, you know, let's say you've
ordered some concrete, you've done the drive and then you
realize that you didn't quite need as much as you needed,
(11:21):
and so there's half a cubic meter or so still
left in the truck. What happens to that when it
goes back to the plant, Like, is any of that
able to be not reused because obviously it's going to
go off, but the aggregate that's in there and that
sort of thing, what happens there is that just waste
or is it able to be reused in some way?
Speaker 3 (11:41):
Well, in the past it has been waste. But since
the last six to seven years, and we have measures
to take the left of a concrete yes, and they
are basically cast into forms, and the result is we
have large, maybe oversized blocks.
Speaker 1 (12:01):
Yep.
Speaker 3 (12:01):
It's going to be reduced for coastal production, but also
for organizing a young out on the farm where I
just want to have your you know, storage sorted that
has been done. And because the architect or engineer or
build our contract or whatever need enough concrete on site,
(12:22):
they always order a little bit more, yep, a little
bit of surplus to not run out of concrete suddenly.
So there's always a leftover and our plans have take
the necessary steps and yeah, all the leftovers maybe cards
into forms back on the plant.
Speaker 1 (12:40):
Right.
Speaker 2 (12:41):
Well that's and actually it's a bigger question than we've
got time for right now, So take a short break.
I want to look at sort of end of life,
what we might be able to do with concrete end
of life. So Ralph Kessel from Concrete, New Zealand is
my guest this morning. It is eight point twenty with
news Talk set B so joining me this morning, Genus
with his time this morning, Ralph Kessel from Concrete, New Zealand.
(13:02):
Thanks again for joining us. Now I'll try and hit
a couple of texts in a minute. But the other
thing that I think has been an interesting change is
in a sense the recycling reuse of left either demolition,
concrete or ensan. So are we seeing more providers being
able to accept demolition material. You know, I've cut up
(13:27):
part of a driveway and I need to dispose of that.
Whereas it used to go just hard fill to landfill,
it's now being repurposed.
Speaker 3 (13:37):
Yes, there are definitely schemes in place and being Auckland
Green Gorilla for example, it's one or larger. They take
conc they get to take construction waste, and amongst that
there's concrete waste, and as I mentioned in my last
interview that the bulk of it will be used for hardfire,
for drainable backfill around properties, et cetera. But were just
(14:03):
ending with ways management before the break and so the
use of repurposed demolition waste and also less over cars
into blocks, it doesn't end there. So we have to
(14:23):
look at the production of concrete as well, where we
have a lot of heat to generate for the kill.
That's actually where the emissions come from, from the kiln,
from the process where we manufacture the cement. So the
one part of the emissions comes from a chemical process
within the kill when we separate the line from the
(14:44):
limestone to gain the cement, and the other part is
the fossil fuel coal which we use to heat the
kilns up to fourteen hundred degrees. And here we use
now waste materials as well for heating the kilden. The
first one is waste timber and the second one is
actually old car tires. And I recall that I think
(15:08):
you may have heard about that the bulk of old
characterires in New Zealand is used by the cement industry
where they replace the coal as a fuel. This scheme
has also reduced illegal tire dumpig buy around fifty percent.
And I should mention that our cemental industry has gas
cleaning filter systems in place to manage all emissions responsibly.
(15:31):
So there's a lot going on in achieving also not
just CARBN zero by twenty fifty, but also to achieve
a fully operating circular economy within the concrete industry.
Speaker 2 (15:44):
Because sometimes people will ask, well, if I you know
there used to be a quarry near me that would
take you know, liftover concrete or waste concrete. You cut
up a driveway, put it on the trailer, dump it
there they'd seen it through the crusher and turn it
into hard filt, which was great because there is a
challenge with the idea of crushing used concrete and reusing
(16:08):
the aggregate and new concrete, isn't there.
Speaker 3 (16:11):
Yes, that can be done as well, but you have
to be careful once if you don't know the original
location or source of that aggregaty, it may be more
difficult to understand the final quality and maybe even the
compressive strength, which we have to test anyway. But so
it's important that you know the source of the aggregot,
(16:33):
and it's also time consuming and energy consuming to get
just really the pebbles and the aggregots away from some
smontitious parts. So that's not ideals. So what we see
more and more is that the concrete demolition wave is
crushed and then used for for backfield under rolling and
(16:57):
around also for coastal protection partly. So there are lots
of things happening.
Speaker 2 (17:04):
And I guess what that does is substitutes, let's say,
virgin material, you know, from a quarry going directly from
a quarry to just being the base course that my
driveway sits on. I'm better off using crush concrete recycled
for that type of purpose.
Speaker 3 (17:21):
Yeah, absolutely, I mean the recycled material that's all very
professionally done. It will will be run through sieves so
we get our gap sizes, whatever pebble sizes they need
for that project. So you can choose really from the
shelves that various gap sizes for your projects from recycled material.
(17:44):
That's definitely happening. But the other thing which you may
find interesting, that we see new construction ways and a
true if you heard about three D printing.
Speaker 2 (17:54):
Yep, the factory. I've seen one of them.
Speaker 3 (17:57):
Absolutely, yes, so, and that's three DE concrete printing is
definitely becoming more mainstream, at least in the US.
Speaker 2 (18:05):
Sure.
Speaker 3 (18:05):
Well, what we see there is that three D printed
homes are now cost neutral already or even cheaper than
timber framed houses. They're also popular because theyre withstand weather events,
which is becoming increasingly important. As a reminder, you may
just look outside of your window. They are wind and
(18:27):
noise resistant too, which you really notice on lust three days.
And then as climate change brings more fire risks, these
concrete houses are naturally fire resistant. We are for comparison,
one hundred millimeters concrete world gives you around sixty minutes
of fire resistant. Typically, structure wards are even thicker one
(18:49):
hundred and fifty millimeter, which gives you almost two hours.
So that gives people a good shelter and peace of
mind and also combating climate change. We shall use local materials,
so concrete is a local material. We don't have packaging.
There are no large shipping distances.
Speaker 2 (19:07):
Right yeah.
Speaker 3 (19:09):
So, and the other thing which I find, at least
in the US, that some people like to have a
distinctive home, and a three DEEP printed home is definitely
a very distinctive home. So this is another reason why
three D printed houses pick up in the US. So
in New Zealand at the moment there are so far
(19:29):
only four projects, including two in Auckland, two in Hamilton,
and one of them as a daycare center, so it
takes a better while until we get to that stage.
So the mix is always a little bit different, small viscous,
it has less, smaller aggregat to be fed into the
(19:52):
three D printer, et cetera. But I see that definitely coming.
And three D printing means less people on the ground,
but it also means less injuries, less health and safety
ri so just clean a building side. We will see
this in the future. It's not quite there where we
(20:13):
have it in the US and maybe other European countries.
It's definitely coming, and.
Speaker 2 (20:20):
I've been lucky enough to visit the Auckland one and
one of the ones in Hamilton, so it is really
it's just that you know, we've got the space to go. Hey,
is there space for innovation and is there more than
just one way to do everything? You know? And I
think that's where it is really really exciting. Excuse me,
just before we go, I've got this text from Darren. Hey,
(20:43):
We've just purchased thirty of those leftover blocks, nine hundred
by nine hundred and nine hundred. They've got a lifting
hoc on them. We utilize them on the Farmer's Flood
Protection and bank Stabilization said. We paid ten bucks each
for them, which makes them very cost effective even after
the freight. So there you go. That's a classic example
of what you're saying. You know, trucks returning with some
surplus concrete gets poured into forms that then and it
(21:07):
goes out to farms and yards and storage facilities and
all sorts. So it is really I think it's I
think it's really exciting when an industry responds to the challenges.
And you know, in this sense, we all know for
very good reasons. We've got a concern around carbon and
the carbon used in construction and it's a huge part
(21:29):
of the amount of carbon that we use in New Zealand. Right,
so every part of the construction sector needs to address
it's the way in which it deals with that, and
obviously concrete New Zealand as part of that as well. Ralph,
I think we're going to get you back and have
a bit more of a chat in a couple of
weeks or a few months or so as well. But
(21:49):
my thanks to you for giving up mer time on
a Sunday morning. Really appreciate it this morning.
Speaker 3 (21:54):
Thank you very much, Being lovely Journey.
Speaker 1 (21:56):
For more from The Residence Builder with Peter Wolfcamp, listen
live to news talks that'd be on Sunday mornings from Sex,
or follow the podcast on iHeartRadio.
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