The Broad Dimension - 2022 Spring/Summer

the newsletter of tbd consultants - Spring/Summer 2022

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In this Edition
What’s Next?
Robots in Construction
The Greening of Concrete

Construction Management Specialists

111 Pine Street, Suite 1315
San Francisco, CA 94111
(415) 981-9430 (San Francisco office)

93 Moraga Way, Suite 206
Orinda, CA 94563
(415) 981-9430 (Orinda office)

6518 Lonetree Blvd., Suite 164
Rocklin, CA 95765
(916) 742-1770 (Sacramento office)

4655 Cass Street, Suite 214
San Diego, CA 92109
(858) 886-7373 (San Diego office)

8538 173rd Avenue NE
Redmond, WA 98052
(206) 571-0128 (Seattle office)

2063 Grant Road
Los Altos, CA 94024
(650) 386-1728 (South Bay office)

WeWork: Pacific Design Center – Red Building
750 N San Vicente Blvd., Ste 800 West
Los Angeles, CA 90069
(424) 343-2652 (Los Angeles, CA office)

1a Zoe House, Church Road, Greystones
Wicklow, A63 WK40, Ireland
+353 86-600-1352 (Europe office)

www.TBDconsultants.com

What’s Next?

As Covid declines but war ravages Ukraine and further disrupts supply chains, we try to get some idea of what this means for the construction market.

Robots in Construction

In this article we look at what robots can do for the construction industry, and how that will help the staff shortages that contractors are experiencing.

The Greening of Concrete

Some form of concrete has been used as a construction material for about 8,000 years, and it has enjoyed that longevity because it is strong (in compression anyway), adaptable to multiple situations and designs, and it’s quite easy to work with. The problem that we now need to address is that concrete is responsible for somewhere between 6% and 10% (5% - 7% for the cement content alone) of the world’s annual emissions of carbon dioxide (CO2), so there is a need to find ways to improve concrete’s effects on the climate. It is estimated that producing one ton of Portland cement adds one ton of CO2 to the environment. A large part of the impact of cement comes from the fact that it goes through a process requiring high temperatures. The other ingredients of concrete, namely aggregate and water, can usually be sourced locally and so require minimal transportation, and they do not need much in the way of processing and therefore contribute little to the carbon impact.

Probably the most interesting way to make concrete green is the use of carbon cured concrete. Concrete has to be kept moist to enable it to cure and reach its design strength and, in the traditional curing process, the CO2 comes from the air. Such weathering carbonation is slow, taking days and can continue for months or years.

However, there are other ways of adding carbon to the concrete. Aramco and the Korea Advanced Institute of Science and Technology achieves 20% CO2 uptake in the concrete by combining it with steam used to keep the setting concrete moist. CO2 can also be infused under controlled pressure and temperature. Another method injects recycled liquid CO2 into the wet mix stage of the process. Some methods of introducing the captured CO2 might be more appropriate for the controlled environment involved when precasting, rather than for insitu concrete. The main chemical reactions from directly introducing CO2 to the mix occur in the first few minutes of hydration, and design strength is achieved in about 3 days as opposed to something like 28 days with traditional methods.

Such carbon cured concrete helps the environment by utilizing post-industrial CO2 captured from industrial and manufacturing processes and embedding it securely. It can also reduce the cement content by around 3% and still achieve an equivalent strength, although local building codes may dictate cement content. These methods do affect the design strengths, but they are largely equivalent and often improve the strength in comparison with traditional methods. Carbonation curing is said to protect better against freeze-thaw damage because the carbonation process leads to a denser product.

There are other ways to improve the carbon footprint of concrete as well. The use of certain admixtures to the concrete can absorb additional CO2 during the curing process and also reduce water usage. The face of exposed concrete panels, etc., can incorporate embedded dye-sensitized solar cells, which have an efficiency around 10%, and be a green energy source. And of course, we can recycle old concrete for use as aggregate in new concrete or as gravel for the sub-base of paving etc. When using recycled concrete or other construction waste as aggregate, special care has to be taken in assessing its quality, especially for structural uses.

Since the vast bulk of the carbon impact of concrete comes from the production of cement, the obvious way to improve its impact is to reduce the amount of cement used in the concrete, and happily there have been ways of doing that for quite a long time.

One method that has been known since the 1930s is the use of fly ash or other supplementary cementitious materials such as blast-furnace slag. Slag cement is often mentioned with regard to the greening of concrete, but there it is often not in relation to the environment but in connection with the blue-green color that the concrete can develop for a while. Fly ash has little, if any, cementitious properties in itself but it can develop them in reactions with calcium hydroxide. As such, it can be used to replace some of the cement (maybe 20% and up to 80% although somewhere in the middle of that range might be a good target). It has little effect on the strength of the concrete, although it can prolong setting times in cold conditions.

Fly ash can make pumping easier and make the cured concrete less permeable to water, etc., and less susceptible to shrinking and cracking. It is those cracks that allow moisture and pollutants in and leads to deterioration of the reinforcing steel, so fly ash helps make concrete construction more durable. The use of fly ash will also normally reduce the volume of water needed for concrete production, and water is a resource that needs conserving. Another use for fly ash is as a lightweight aggregate, and it has the advantage that it is a byproduct of other activities, so it produces no CO2 in and of itself. Of course, the primary source of fly ash is from coal-burning power stations, which have their own serious drawbacks in relation to the carbon cycle.

Probably the best way to reduce concrete’s impact is to use a sustainable substitute material, such as timber. But, while major advances in timber construction have occurred in recent years, it still doesn’t meet all needs. Consequently, we have to examine all the options for making concrete itself more “green” and, along with that, make sure that local construction codes safely permit the adoption of advances in concrete construction.

Design consultant: Katie Levine of Vallance, Inc.



the newsletter of tbd consultants - Spring/Summer 2022


		Printable PDF version Subscribe to our newsletter In this Edition What’s Next? Robots in Construction The Greening of Concrete
	Construction Management Specialists 111 Pine Street, Suite 1315 San Francisco, CA 94111 (415) 981-9430 (San Francisco office) 93 Moraga Way, Suite 206 Orinda, CA 94563 (415) 981-9430 (Orinda office) 6518 Lonetree Blvd., Suite 164 Rocklin, CA 95765 (916) 742-1770 (Sacramento office) 4655 Cass Street, Suite 214 San Diego, CA 92109 (858) 886-7373 (San Diego office) 8538 173rd Avenue NE Redmond, WA 98052 (206) 571-0128 (Seattle office) 2063 Grant Road Los Altos, CA 94024 (650) 386-1728 (South Bay office) WeWork: Pacific Design Center – Red Building 750 N San Vicente Blvd., Ste 800 West Los Angeles, CA 90069 (424) 343-2652 (Los Angeles, CA office) 1a Zoe House, Church Road, Greystones Wicklow, A63 WK40, Ireland +353 86-600-1352 (Europe office) www.TBDconsultants.com


	What’s Next? As Covid declines but war ravages Ukraine and further disrupts supply chains, we try to get some idea of what this means for the construction market.




	Robots in Construction In this article we look at what robots can do for the construction industry, and how that will help the staff shortages that contractors are experiencing.




	The Greening of Concrete Some form of concrete has been used as a construction material for about 8,000 years, and it has enjoyed that longevity because it is strong (in compression anyway), adaptable to multiple situations and designs, and it’s quite easy to work with. The problem that we now need to address is that concrete is responsible for somewhere between 6% and 10% (5% - 7% for the cement content alone) of the world’s annual emissions of carbon dioxide (CO2), so there is a need to find ways to improve concrete’s effects on the climate. It is estimated that producing one ton of Portland cement adds one ton of CO2 to the environment. A large part of the impact of cement comes from the fact that it goes through a process requiring high temperatures. The other ingredients of concrete, namely aggregate and water, can usually be sourced locally and so require minimal transportation, and they do not need much in the way of processing and therefore contribute little to the carbon impact. Probably the most interesting way to make concrete green is the use of carbon cured concrete. Concrete has to be kept moist to enable it to cure and reach its design strength and, in the traditional curing process, the CO2 comes from the air. Such weathering carbonation is slow, taking days and can continue for months or years. However, there are other ways of adding carbon to the concrete. Aramco and the Korea Advanced Institute of Science and Technology achieves 20% CO2 uptake in the concrete by combining it with steam used to keep the setting concrete moist. CO2 can also be infused under controlled pressure and temperature. Another method injects recycled liquid CO2 into the wet mix stage of the process. Some methods of introducing the captured CO2 might be more appropriate for the controlled environment involved when precasting, rather than for insitu concrete. The main chemical reactions from directly introducing CO2 to the mix occur in the first few minutes of hydration, and design strength is achieved in about 3 days as opposed to something like 28 days with traditional methods. Such carbon cured concrete helps the environment by utilizing post-industrial CO2 captured from industrial and manufacturing processes and embedding it securely. It can also reduce the cement content by around 3% and still achieve an equivalent strength, although local building codes may dictate cement content. These methods do affect the design strengths, but they are largely equivalent and often improve the strength in comparison with traditional methods. Carbonation curing is said to protect better against freeze-thaw damage because the carbonation process leads to a denser product. There are other ways to improve the carbon footprint of concrete as well. The use of certain admixtures to the concrete can absorb additional CO2 during the curing process and also reduce water usage. The face of exposed concrete panels, etc., can incorporate embedded dye-sensitized solar cells, which have an efficiency around 10%, and be a green energy source. And of course, we can recycle old concrete for use as aggregate in new concrete or as gravel for the sub-base of paving etc. When using recycled concrete or other construction waste as aggregate, special care has to be taken in assessing its quality, especially for structural uses. Since the vast bulk of the carbon impact of concrete comes from the production of cement, the obvious way to improve its impact is to reduce the amount of cement used in the concrete, and happily there have been ways of doing that for quite a long time. One method that has been known since the 1930s is the use of fly ash or other supplementary cementitious materials such as blast-furnace slag. Slag cement is often mentioned with regard to the greening of concrete, but there it is often not in relation to the environment but in connection with the blue-green color that the concrete can develop for a while. Fly ash has little, if any, cementitious properties in itself but it can develop them in reactions with calcium hydroxide. As such, it can be used to replace some of the cement (maybe 20% and up to 80% although somewhere in the middle of that range might be a good target). It has little effect on the strength of the concrete, although it can prolong setting times in cold conditions. Fly ash can make pumping easier and make the cured concrete less permeable to water, etc., and less susceptible to shrinking and cracking. It is those cracks that allow moisture and pollutants in and leads to deterioration of the reinforcing steel, so fly ash helps make concrete construction more durable. The use of fly ash will also normally reduce the volume of water needed for concrete production, and water is a resource that needs conserving. Another use for fly ash is as a lightweight aggregate, and it has the advantage that it is a byproduct of other activities, so it produces no CO2 in and of itself. Of course, the primary source of fly ash is from coal-burning power stations, which have their own serious drawbacks in relation to the carbon cycle. Probably the best way to reduce concrete’s impact is to use a sustainable substitute material, such as timber. But, while major advances in timber construction have occurred in recent years, it still doesn’t meet all needs. Consequently, we have to examine all the options for making concrete itself more “green” and, along with that, make sure that local construction codes safely permit the adoption of advances in concrete construction.




	Design consultant: Katie Levine of Vallance, Inc.