Laitance - Revision history

Designing Buildings at 07:47, 27 May 2022

2022-05-27T07:47:40Z

← Older revision		Revision as of 07:47, 27 May 2022
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	* Acid etching: The acid attacks and breaks down the the top surface. This should only be used if other options have been ruled out.		* Acid etching: The acid attacks and breaks down the the top surface. This should only be used if other options have been ruled out.

−	= Related articles on Designing Buildings ~~Wiki~~ =	+	NB [https://www.historicenvironment.scot/archives-and-research/publications/publication/?publicationId=85ced9f0-474d-4ec6-8dd6-a59100fc306f Short Guide, Lime Mortars in Traditional Buildings], published on 1 March 2013 by Historic Scotland, defines laitance as: ‘The thin layer of fine lime particles that migrate to the surface of lime mortars. Laitance reduces the breathability of the mortar due to its very fine grained and less permeable texture. Laitance is made worse by overworking lime but can be removed by ‘beating back’ with a hard bristle brush, or gently rubbing with an abrasive pad.’
		+
		+	= Related articles on Designing Buildings =

	* Alkali-silica reaction (ASR).		* Alkali-silica reaction (ASR).
Line 26:		Line 28:
	* Efflorescence.		* Efflorescence.
	* Flooring defects.		* Flooring defects.
−	* ~~How to clean concrete~~.	+	* Lime.
	* Lime run-off.		* Lime run-off.
	* Mould growth in buildings.		* Mould growth in buildings.

Designing Buildings at 08:03, 17 November 2020

2020-11-17T08:03:52Z

← Older revision		Revision as of 08:03, 17 November 2020
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	* The properties of concrete.		* The properties of concrete.

−	[[Category:Construction_management]] [[Category:Property_development]]	+	[[Category:DCN_Definition]] [[Category:DCN_Guidance]] [[Category:Construction_management]] [[Category:Property_development]]

Editor at 19:05, 13 January 2020

2020-01-13T19:05:42Z

← Older revision		Revision as of 19:05, 13 January 2020
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	* Construction dust.		* Construction dust.
	* Construction tools.		* Construction tools.
		+	* Curing.
	* Efflorescence.		* Efflorescence.
	* Flooring defects.		* Flooring defects.

Editor at 14:57, 11 October 2018

2018-10-11T14:57:38Z

← Older revision		Revision as of 14:57, 11 October 2018
Line 15:		Line 15:
	* Acid etching: The acid attacks and breaks down the the top surface. This should only be used if other options have been ruled out.		* Acid etching: The acid attacks and breaks down the the top surface. This should only be used if other options have been ruled out.

−	~~= Find out more =~~	+	= Related articles on Designing Buildings Wiki =
−		+
−	=== Related articles on Designing Buildings Wiki ===	+

	* Alkali-silica reaction (ASR).		* Alkali-silica reaction (ASR).
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	* Mould growth in buildings.		* Mould growth in buildings.
	* Scabbling.		* Scabbling.
		+	* Stain.
	* Stratification of concrete.		* Stratification of concrete.
	* The properties of concrete.		* The properties of concrete.

	[[Category:Construction_management]] [[Category:Property_development]]		[[Category:Construction_management]] [[Category:Property_development]]

Editor at 14:49, 22 June 2018

2018-06-22T14:49:47Z

← Older revision		Revision as of 14:49, 22 June 2018
Line 19:		Line 19:
	=== Related articles on Designing Buildings Wiki ===		=== Related articles on Designing Buildings Wiki ===

		+	* Alkali-silica reaction (ASR).
	* Concrete.		* Concrete.
	* Concrete repair mortars.		* Concrete repair mortars.

Designing Buildings at 12:32, 6 May 2018

2018-05-06T12:32:03Z

← Older revision		Revision as of 12:32, 6 May 2018
Line 5:		Line 5:
	The thickness of laitance can be determined by scratching the surface with a screwdriver or other metallic edge until reaching the main aggregate. Thicknesses can vary but are seldom more than 5 or 6 mm. Since laitance has poor adhesion to the actual aggregate in the concrete mix, heavy traffic and impact will delaminate it or cause it to dust away under abrasion.		The thickness of laitance can be determined by scratching the surface with a screwdriver or other metallic edge until reaching the main aggregate. Thicknesses can vary but are seldom more than 5 or 6 mm. Since laitance has poor adhesion to the actual aggregate in the concrete mix, heavy traffic and impact will delaminate it or cause it to dust away under abrasion.

−	The removal of laitance is important in order that subsequent materials applied to the floor~~, i.e. smoothing underlays or surface treatments,~~ will properly adhere to ~~the concrete~~. ~~The different methods for removal include:~~	+	The removal of laitance is important in order that subsequent materials applied to the floor will properly adhere to it.

−	* Shot blasting: ~~Fast~~ and efficient method that involves firing abrasive elements to the area at high velocity.	+	Methods for removal include:
−	* Mechanical planning: Used for thicker laitance and ~~involves~~ a machine with rows of rotating tungsten-tipped cutters.	+
−	* Scabbling: A heavy-duty method that involves compressed air tools which ~~vibrates~~ and impact the concrete surface.	+	* Shot blasting: A fast and efficient method that involves firing abrasive elements on the area at high velocity.
−	* Grinding: Handheld tools are used for smaller areas and ~~edge detail~~.	+	* Mechanical planning: Used for thicker laitance and involving a machine with rows of rotating tungsten-tipped cutters.
−	* Acid etching: The acid attacks and breaks down the ~~cement content on~~ the top surface. ~~Should~~ only be used if other options have been ruled out.	+	* Scabbling: A heavy-duty method that involves compressed air tools which vibrate and impact the concrete surface.
		+	* Grinding: Handheld tools are used for smaller areas and edges.
		+	* Acid etching: The acid attacks and breaks down the the top surface. This should only be used if other options have been ruled out.

	= Find out more =		= Find out more =

Editor: Created page with "Laitance is a weak friable layer of fine particles that can form on the surface of concrete after it has cured and is a common cause of floor failure. It is comprised of hydrated..."

2018-05-02T14:48:28Z

Created page with "Laitance is a weak friable layer of fine particles that can form on the surface of concrete after it has cured and is a common cause of floor failure. It is comprised of hydrated..."

New page

Laitance is a weak friable layer of fine particles that can form on the surface of concrete after it has cured and is a common cause of floor failure. It is comprised of hydrated cement and fine aggregates which rise to the surface with the addition of too much water.

It is formed when an abundance of water in the mix creates an upward movement through the concrete. It can also be a result of rain damage during the placing process, or of over-trowelling and excessive tamping, or vibration of the concrete.

The thickness of laitance can be determined by scratching the surface with a screwdriver or other metallic edge until reaching the main aggregate. Thicknesses can vary but are seldom more than 5 or 6 mm. Since laitance has poor adhesion to the actual aggregate in the concrete mix, heavy traffic and impact will delaminate it or cause it to dust away under abrasion.

The removal of laitance is important in order that subsequent materials applied to the floor, i.e. smoothing underlays or surface treatments, will properly adhere to the concrete. The different methods for removal include:

* Shot blasting: Fast and efficient method that involves firing abrasive elements to the area at high velocity.
* Mechanical planning: Used for thicker laitance and involves a machine with rows of rotating tungsten-tipped cutters.
* Scabbling: A heavy-duty method that involves compressed air tools which vibrates and impact the concrete surface.
* Grinding: Handheld tools are used for smaller areas and edge detail.
* Acid etching: The acid attacks and breaks down the cement content on the top surface. Should only be used if other options have been ruled out.

= Find out more =

=== Related articles on Designing Buildings Wiki ===

* Concrete.
* Concrete repair mortars.
* Concreting plant.
* Construction dust.
* Construction tools.
* Efflorescence.
* Flooring defects.
* How to clean concrete.
* Lime run-off.
* Mould growth in buildings.
* Scabbling.
* Stratification of concrete.
* The properties of concrete.

[[Category:Construction_management]] [[Category:Property_development]]