StableConcrete - Revision history

Eric: Added a Category to the Page

2022-01-09T01:37:39Z

Added a Category to the Page

← Older revision		Revision as of 01:37, 9 January 2022
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	*{{Lathe}}		*{{Lathe}}
	* {{Steam Engine}}		* {{Steam Engine}}

			[[Category: Concrete]]

ChuckH: Last several edits were fixing broken links

2021-07-26T00:13:47Z

Last several edits were fixing broken links

ChuckH: /* Steel reinforcement */

2021-07-25T22:21:57Z

Steel reinforcement

← Older revision		Revision as of 22:21, 25 July 2021
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	PCC is strong in compression but much weaker in tension. The loads on a machine frame will typically put some parts of the frame in tension, and these parts must be reinforced. The simplest support is to cast reinforcing bar (rebar) into the concrete mass. While rebar makes the section strong, it also, ironically, is almost certain to make it filled with small cracks. This is because the concrete sets and locks to the rebar long before it finishes shrinking[https://wiki.opensourceecology.org/images/8/8c/ACI_224R-01_Control_of_Cracking_in_Concrete_Structures_f224R%2801%29Chap3.pdf]:<br>[[File:Cracking.png \|border]]<br>'''Figure: Crack development during curing of concrete with embedded steel reinforcement bar'''		PCC is strong in compression but much weaker in tension. The loads on a machine frame will typically put some parts of the frame in tension, and these parts must be reinforced. The simplest support is to cast reinforcing bar (rebar) into the concrete mass. While rebar makes the section strong, it also, ironically, is almost certain to make it filled with small cracks. This is because the concrete sets and locks to the rebar long before it finishes shrinking[https://wiki.opensourceecology.org/images/8/8c/ACI_224R-01_Control_of_Cracking_in_Concrete_Structures_f224R%2801%29Chap3.pdf]:<br>[[File:Cracking.png \|border]]<br>'''Figure: Crack development during curing of concrete with embedded steel reinforcement bar'''

	To avoid this, the concrete should use ''post-tensioned'' steel reinforcement. By maintaining the concrete always in compression, and never above 30% of the ultimate compressive stress limit, the concrete microstructure will remain quite stable[http://www.cv.titech.ac.jp/~courses/atce1/dim_stab.pdf],[~~http~~://~~people~~.ce.~~gatech.edu~~/~~~kk92~~/~~grad/dim~~.pdf].		To avoid this, the concrete should use ''post-tensioned'' steel reinforcement. By maintaining the concrete always in compression, and never above 30% of the ultimate compressive stress limit, the concrete microstructure will remain quite stable[http://www.cv.titech.ac.jp/~courses/atce1/dim_stab.pdf],[https://wiki.opensourceecology.org/wiki/File:Dim.pdf].

	== Recommendations ==		== Recommendations ==

ChuckH: /* Stable Concrete for Machine Frames */

2021-07-25T22:16:01Z

Stable Concrete for Machine Frames

← Older revision		Revision as of 22:16, 25 July 2021
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	Machine tool frames made of PCC date at least as far back as the [https://www.engineeringforchange.org/news/2011/07/31/the_concrete_lathe_world_war_i_technology_meets_21st_century_design.html Yeoman lathe], (see also [http://www.google.com/patents/US3800636 Zagar]) but have never been widely adopted.		Machine tool frames made of PCC date at least as far back as the [https://www.engineeringforchange.org/news/2011/07/31/the_concrete_lathe_world_war_i_technology_meets_21st_century_design.html Yeoman lathe], (see also [http://www.google.com/patents/US3800636 Zagar]) but have never been widely adopted.
	In contrast, since the 1980s, polymer concrete has become quite popular in construction of precision machine tools, first in Europe and now worldwide [~~http~~://www.americanmachinist.com/~~304~~/~~Issue~~/~~Article~~/~~False~~/~~80845/Issue~~]. The first commercially important concrete for this purpose was the epoxy-granite composite [http://www.adgrind.com/Studer/Granitan/granitan.htm Granitan], made by the Swiss grinding-machine manufacturer Studer.		In contrast, since the 1980s, polymer concrete has become quite popular in construction of precision machine tools, first in Europe and now worldwide [https://www.americanmachinist.com/archive/features/article/21892630/rocksolid-machine-bases]. The first commercially important concrete for this purpose was the epoxy-granite composite [http://www.adgrind.com/Studer/Granitan/granitan.htm Granitan], made by the Swiss grinding-machine manufacturer Studer.

	Polymer concretes have much better dimensional stability than PCC. [http://books.google.com/books?id=uG7aqgal65YC&pg=PA317#v=onepage&q&f=false Slocum] declares PCC unsatisfactory for precision machinery due to:		Polymer concretes have much better dimensional stability than PCC. [http://books.google.com/books?id=uG7aqgal65YC&pg=PA317#v=onepage&q&f=false Slocum] declares PCC unsatisfactory for precision machinery due to:

ChuckH: /* Recommendations */

2021-07-25T22:07:50Z

Recommendations

← Older revision		Revision as of 22:07, 25 July 2021
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	** There is a huge variety of concrete sealing products being sold but little hard information on what works best as a vapor barrier (and whether it works any better than asphaltic mastic or a standard wall paint).		** There is a huge variety of concrete sealing products being sold but little hard information on what works best as a vapor barrier (and whether it works any better than asphaltic mastic or a standard wall paint).

	<div id="HolographyTable"></div>These folks wanted stability (world's largest laser holography table[http://smartec.ch/HTMLFiles/Concrete_holography_table_IMM.htm]) and got this:<br>[[File:Shrinkage.png \|border]]<br>		<div id="HolographyTable"></div>These folks wanted stability (world's largest laser holography table[http://smartec.ch/HTMLFiles/Concrete_holography_table_IMM.htm],[https://spie.org/Publications/Proceedings/Paper/10.1117/12.155030]) and got this:<br>[[File:Shrinkage.png \|border]]<br>
	The stability reached after 120 days (~ +/-0.2mm over 20m, ~1e-5) is very promising for a machine tool application. The authors ascribe the residual dimensional changes to seasonal temperature variation.		The stability reached after 120 days (~ +/-0.2mm over 20m, ~1e-5) is very promising for a machine tool application. The authors ascribe the residual dimensional changes to seasonal temperature variation.

ChuckH at 22:03, 25 July 2021

2021-07-25T22:03:16Z

← Older revision		Revision as of 22:03, 25 July 2021
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	After the curing process is essentially finished, the concrete remains humidity-sensitive, a bit like wood -- expanding in high humidity and contracting when air is dryer. Concrete also responds to temperature: it has a thermal expansion coefficient close to that of steel. Sealing the surface with paint or similar coating can greatly reduce humidity effects. (This should also reduce carbon dioxide absorption, which causes an additional shrinkage chemical reaction: carbonation.)		After the curing process is essentially finished, the concrete remains humidity-sensitive, a bit like wood -- expanding in high humidity and contracting when air is dryer. Concrete also responds to temperature: it has a thermal expansion coefficient close to that of steel. Sealing the surface with paint or similar coating can greatly reduce humidity effects. (This should also reduce carbon dioxide absorption, which causes an additional shrinkage chemical reaction: carbonation.)

	In "latex concrete", which is PCC with a substantial addition of acrylic or SBR polymer emulsion, most of the pores are filled with polymer; this tends to reduce shrinkage, make the concrete more stable against moisture-related effects, and make it less brittle. Using acrylic latex concrete for thin-shell roofs is described [http://ceae.colorado.edu/mc-edc/pdf/Acrylic%20Concrete%20Roofs.pdf here]. [~~http~~://~~www~~.~~basf-cc~~.ae/en/~~products~~/~~Mortar~~/~~Rheomix141/Pages/default~~.~~aspx~~ Rheomix 141], a styrene-butadiene copolymer, has also been recommended for that application. It seems likely that one of these admixtures would considerably improve the stability of a cast-concrete machine base.		In "latex concrete", which is PCC with a substantial addition of acrylic or SBR polymer emulsion, most of the pores are filled with polymer; this tends to reduce shrinkage, make the concrete more stable against moisture-related effects, and make it less brittle. Using acrylic latex concrete for thin-shell roofs is described [http://ceae.colorado.edu/mc-edc/pdf/Acrylic%20Concrete%20Roofs.pdf here]. [https://wiki.opensourceecology.org/images/e/ef/Mastercast-141-tds.pdf Rheomix 141], a styrene-butadiene copolymer, has also been recommended for that application. It seems likely that one of these admixtures would considerably improve the stability of a cast-concrete machine base.

	== Steel reinforcement ==		== Steel reinforcement ==

ChuckH at 21:53, 25 July 2021

2021-07-25T21:53:13Z

← Older revision		Revision as of 21:53, 25 July 2021
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	== Steel reinforcement ==		== Steel reinforcement ==

	PCC is strong in compression but much weaker in tension. The loads on a machine frame will typically put some parts of the frame in tension, and these parts must be reinforced. The simplest support is to cast reinforcing bar (rebar) into the concrete mass. While rebar makes the section strong, it also, ironically, is almost certain to make it filled with small cracks. This is because the concrete sets and locks to the rebar long before it finishes shrinking[~~http~~://~~www~~.~~concrete~~.org/~~General~~/~~f224R(01)Chap3~~.pdf]:<br>[[File:Cracking.png \|border]]<br>'''Figure: Crack development during curing of concrete with embedded steel reinforcement bar'''		PCC is strong in compression but much weaker in tension. The loads on a machine frame will typically put some parts of the frame in tension, and these parts must be reinforced. The simplest support is to cast reinforcing bar (rebar) into the concrete mass. While rebar makes the section strong, it also, ironically, is almost certain to make it filled with small cracks. This is because the concrete sets and locks to the rebar long before it finishes shrinking[https://wiki.opensourceecology.org/images/8/8c/ACI_224R-01_Control_of_Cracking_in_Concrete_Structures_f224R%2801%29Chap3.pdf]:<br>[[File:Cracking.png \|border]]<br>'''Figure: Crack development during curing of concrete with embedded steel reinforcement bar'''

	To avoid this, the concrete should use ''post-tensioned'' steel reinforcement. By maintaining the concrete always in compression, and never above 30% of the ultimate compressive stress limit, the concrete microstructure will remain quite stable[http://www.cv.titech.ac.jp/~courses/atce1/dim_stab.pdf],[http://people.ce.gatech.edu/~kk92/grad/dim.pdf].		To avoid this, the concrete should use ''post-tensioned'' steel reinforcement. By maintaining the concrete always in compression, and never above 30% of the ultimate compressive stress limit, the concrete microstructure will remain quite stable[http://www.cv.titech.ac.jp/~courses/atce1/dim_stab.pdf],[http://people.ce.gatech.edu/~kk92/grad/dim.pdf].

ChuckH: /* Steel reinforcement */

2013-01-16T01:11:15Z

Steel reinforcement

← Older revision		Revision as of 01:11, 16 January 2013
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	PCC is strong in compression but much weaker in tension. The loads on a machine frame will typically put some parts of the frame in tension, and these parts must be reinforced. The simplest support is to cast reinforcing bar (rebar) into the concrete mass. While rebar makes the section strong, it also, ironically, is almost certain to make it filled with small cracks. This is because the concrete sets and locks to the rebar long before it finishes shrinking[http://www.concrete.org/General/f224R(01)Chap3.pdf]:<br>[[File:Cracking.png \|border]]<br>'''Figure: Crack development during curing of concrete with embedded steel reinforcement bar'''		PCC is strong in compression but much weaker in tension. The loads on a machine frame will typically put some parts of the frame in tension, and these parts must be reinforced. The simplest support is to cast reinforcing bar (rebar) into the concrete mass. While rebar makes the section strong, it also, ironically, is almost certain to make it filled with small cracks. This is because the concrete sets and locks to the rebar long before it finishes shrinking[http://www.concrete.org/General/f224R(01)Chap3.pdf]:<br>[[File:Cracking.png \|border]]<br>'''Figure: Crack development during curing of concrete with embedded steel reinforcement bar'''

	To avoid this, the concrete should use ''post-tensioned'' steel reinforcement. By maintaining the concrete always in compression, and never above 30% of the ultimate compressive stress limit, the concrete microstructure will remain quite stable[www.cv.titech.ac.jp/~courses/atce1/dim_stab.pdf],[http://people.ce.gatech.edu/~kk92/grad/dim.pdf].		To avoid this, the concrete should use ''post-tensioned'' steel reinforcement. By maintaining the concrete always in compression, and never above 30% of the ultimate compressive stress limit, the concrete microstructure will remain quite stable[http://www.cv.titech.ac.jp/~courses/atce1/dim_stab.pdf],[http://people.ce.gatech.edu/~kk92/grad/dim.pdf].

	== Recommendations ==		== Recommendations ==

ChuckH: /* Steel reinforcement */

2013-01-16T01:10:54Z

Steel reinforcement

← Older revision		Revision as of 01:10, 16 January 2013
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	PCC is strong in compression but much weaker in tension. The loads on a machine frame will typically put some parts of the frame in tension, and these parts must be reinforced. The simplest support is to cast reinforcing bar (rebar) into the concrete mass. While rebar makes the section strong, it also, ironically, is almost certain to make it filled with small cracks. This is because the concrete sets and locks to the rebar long before it finishes shrinking[http://www.concrete.org/General/f224R(01)Chap3.pdf]:<br>[[File:Cracking.png \|border]]<br>'''Figure: Crack development during curing of concrete with embedded steel reinforcement bar'''		PCC is strong in compression but much weaker in tension. The loads on a machine frame will typically put some parts of the frame in tension, and these parts must be reinforced. The simplest support is to cast reinforcing bar (rebar) into the concrete mass. While rebar makes the section strong, it also, ironically, is almost certain to make it filled with small cracks. This is because the concrete sets and locks to the rebar long before it finishes shrinking[http://www.concrete.org/General/f224R(01)Chap3.pdf]:<br>[[File:Cracking.png \|border]]<br>'''Figure: Crack development during curing of concrete with embedded steel reinforcement bar'''

	To avoid this, the concrete should use ''post-tensioned'' steel reinforcement. By maintaining the concrete always in compression, and never above 30% of the ultimate compressive stress limit, the concrete microstructure will remain quite stable[~~http:/~~/courses~~.washington.edu~~/~~cm425~~/dim_stab.pdf],[http://people.ce.gatech.edu/~kk92/grad/dim.pdf].		To avoid this, the concrete should use ''post-tensioned'' steel reinforcement. By maintaining the concrete always in compression, and never above 30% of the ultimate compressive stress limit, the concrete microstructure will remain quite stable[www.cv.titech.ac.jp/~courses/atce1/dim_stab.pdf],[http://people.ce.gatech.edu/~kk92/grad/dim.pdf].

	== Recommendations ==		== Recommendations ==

ChuckH: /* Steel reinforcement */

2012-03-05T07:27:10Z

Steel reinforcement

← Older revision		Revision as of 07:27, 5 March 2012
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	== Steel reinforcement ==		== Steel reinforcement ==

	PCC is strong in compression but much weaker in tension. The loads on a machine frame will typically put some parts of the frame in tension, and these parts must be reinforced. The simplest support is to cast reinforcing bar (rebar) into the concrete mass. While rebar makes the section strong, it also, ironically, is almost certain to make it filled with small cracks. This is because the concrete sets and locks to the rebar long before it finishes shrinking[http://www.concrete.org/General/f224R(01)Chap3.pdf]:<br>[[File:Cracking.png \|border]]<br>To avoid this, the concrete should use ''post-tensioned'' steel reinforcement. By maintaining the concrete always in compression, and never above 30% of the ultimate compressive stress limit, the concrete microstructure will remain quite stable[http://courses.washington.edu/cm425/dim_stab.pdf],[http://people.ce.gatech.edu/~kk92/grad/dim.pdf].		PCC is strong in compression but much weaker in tension. The loads on a machine frame will typically put some parts of the frame in tension, and these parts must be reinforced. The simplest support is to cast reinforcing bar (rebar) into the concrete mass. While rebar makes the section strong, it also, ironically, is almost certain to make it filled with small cracks. This is because the concrete sets and locks to the rebar long before it finishes shrinking[http://www.concrete.org/General/f224R(01)Chap3.pdf]:<br>[[File:Cracking.png \|border]]<br>'''Figure: Crack development during curing of concrete with embedded steel reinforcement bar'''

			To avoid this, the concrete should use ''post-tensioned'' steel reinforcement. By maintaining the concrete always in compression, and never above 30% of the ultimate compressive stress limit, the concrete microstructure will remain quite stable[http://courses.washington.edu/cm425/dim_stab.pdf],[http://people.ce.gatech.edu/~kk92/grad/dim.pdf].

	== Recommendations ==		== Recommendations ==

← Older revision		Revision as of 00:13, 26 July 2021
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	* it is moderately stiff (though much less stiff than cast metals)		* it is moderately stiff (though much less stiff than cast metals)
	* it absorbs vibration well		* it absorbs vibration well
	* it is very ~~east~~ to cast into arbitrary shapes		* it is very easy to cast into arbitrary shapes
	* it is low cost		* it is low cost

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	Polymer concretes have much better dimensional stability than PCC. [http://books.google.com/books?id=uG7aqgal65YC&pg=PA317#v=onepage&q&f=false Slocum] declares PCC unsatisfactory for precision machinery due to:		Polymer concretes have much better dimensional stability than PCC. [http://books.google.com/books?id=uG7aqgal65YC&pg=PA317#v=onepage&q&f=false Slocum] declares PCC unsatisfactory for precision machinery due to:
	* reaction shrinkage from cement hydration		* reaction shrinkage from cement hydration
	* shrinkage due loss of excess nonstoichiometric water, which leaves conduits for humidity-induced expansion or contraction, and		* shrinkage due to loss of excess nonstoichiometric water, which leaves conduits for humidity-induced expansion or contraction, and
	* non-elastic dimensional changes (e.g. creep and microcracking in the inherent brittle/porous structure).		* non-elastic dimensional changes (e.g. creep and microcracking in the inherent brittle/porous structure).
	A [http://dx.doi.org/10.1016/0141-6359(85)90041-8 scientific paper] comparing PCC and polymer concretes in machine tool applications was published by a Studer researcher in 1985. Another article [http://dx.doi.org/10.1016/S0007-8506(07)61657-6 here].		A [http://dx.doi.org/10.1016/0141-6359(85)90041-8 scientific paper] comparing PCC and polymer concretes in machine tool applications was published by a Studer researcher in 1985. Another article [http://dx.doi.org/10.1016/S0007-8506(07)61657-6 here].
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	To obtain a dimensionally stable frame, the following steps are recommended:		To obtain a dimensionally stable frame, the following steps are recommended:
	* Use ~~aggregrate~~ crushed from a dense, stable mineral, preferably granite, limestone, or quartz.		* Use aggregate crushed from a dense, stable mineral, preferably granite, limestone, or quartz.
	* Post-tension the assembly after ~4 weeks cure		* Post-tension the assembly after ~4 weeks cure
	* Paint all surfaces after ~90 days cure		* Paint all surfaces after ~90 days cure
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	** There is a huge variety of concrete sealing products being sold but little hard information on what works best as a vapor barrier (and whether it works any better than asphaltic mastic or a standard wall paint).		** There is a huge variety of concrete sealing products being sold but little hard information on what works best as a vapor barrier (and whether it works any better than asphaltic mastic or a standard wall paint).

	<div id="HolographyTable"></div>These folks wanted stability (world's largest laser holography table[http://smartec.ch/HTMLFiles/Concrete_holography_table_IMM.htm],[https://spie.org/Publications/Proceedings/Paper/10.1117/12.155030]) and got this:<br>[[File:Shrinkage.png \|border]]<br>		<div id="HolographyTable"></div>These folks wanted stability (world's largest laser holography table in 1993[http://smartec.ch/HTMLFiles/Concrete_holography_table_IMM.htm],[https://spie.org/Publications/Proceedings/Paper/10.1117/12.155030]) and got this:<br>[[File:Shrinkage.png \|border]]<br>
	The stability reached after 120 days (~ +/-0.2mm over 20m, ~1e-5) is very promising for a machine tool application. The authors ascribe the residual dimensional changes to seasonal temperature variation.		The stability reached after 120 days (~ +/-0.2mm over 20m, ~1e-5) is very promising for a machine tool application. The authors ascribe the residual dimensional changes to seasonal temperature variation.