Lightweight concrete solutions - Revision history

Designing Buildings at 05:47, 5 September 2023

2023-09-05T05:47:07Z

← Older revision		Revision as of 05:47, 5 September 2023
Line 61:		Line 61:
	== Contemporary issues with RAAC ==		== Contemporary issues with RAAC ==

−	Crumbling concrete describes failure where concrete parts fall off in chunks and the strength of the overall material is compromised. It can simply be the result of ageing but maybe worsened where the initial pour was not managed correctly, where reinforcement elements are beginning to corrode or where the material is exposed to harsh elements or mechanical damage. This type of failure has started to be associated more closely with RAAC, the reasons vary, with specific cases but some RAAC installations were built as early as the 1950's and so maybe seeing issues because the products have exceeded their expected lifespan. In many cases issues arise through the failure of ~~water proof~~ coverings, such as flat roofs, allowing the ~~exteral~~ surface of the RAAC to become wet, once damp over time, it can effectively soak up moisture, similar to a sponge, leading to corrosion of the reinforcement. Other ~~and~~ related issues with newer product installations may ~~indeed~~ be as a result of either poor design or fabrication / installation issues often relating to the location of the reinforcement to near the edges (relating again to moisture and corosion) and the concrete mix.	+	Crumbling concrete describes failure where concrete parts fall off in chunks and the strength of the overall material is compromised. It can simply be the result of ageing but maybe worsened where the initial pour was not managed correctly, where reinforcement elements are beginning to corrode or where the material is exposed to harsh elements or mechanical damage. This type of failure has started to be associated more closely with RAAC, the reasons vary, with specific cases but some RAAC installations were built as early as the 1950's and so maybe seeing issues because the products have exceeded their expected lifespan. In many cases issues arise through the failure of waterproof coverings, such as flat roofs, allowing the external surface of the RAAC to become wet, once damp, over time, it can effectively soak up moisture, similar to a sponge, leading to corrosion of the reinforcement. Other related issues with newer product installations may be as a result of either poor design or fabrication / installation issues often relating to the location of the reinforcement too near the edges, relating again to moisture and corosion, and the concrete mix.

−	In December 2022 the UK Government published 'Reinforced autoclaved aerated concrete (RAAC): estates guidance'. The guidance set out a 5-stage approach to the identification and management of RAAC in educational buildings, where these ~~maybe~~ present in floors, walls and roofs (pitched and flat) of buildings constructed or modified between the 1950s and mid-1990s. This guidance outlined initial steps that should be taken by those responsible for the management of educational buildings, how to procure building professional’s services when specialist advice is needed. It was designed for all parties involved in the identification and management of RAAC, including estates managers and those providing specialist advice~~, can use this guidance~~.	+	In December 2022 the UK Government published 'Reinforced autoclaved aerated concrete (RAAC): estates guidance'. The guidance set out a 5-stage approach for the identification and management of RAAC in educational buildings, where these may be present in floors, walls and roofs (pitched and flat) of buildings constructed or modified between the 1950s and mid-1990s. This guidance outlined initial steps that should be taken by those responsible for the management of educational buildings about how to procure building professional’s services when specialist advice is needed. It was designed for all parties involved in the identification and management of RAAC, including estates managers and those providing specialist advice.

−	In mid 2023 UK ministers Ministers launched a UK government-wide inquiry into the use of crumbling concrete, in particular occurring in reinforced autoclaved aerated concrete (RAAC). Initial indication is that many of the installations at risk are over 30 years old which may be beyond the expected lifespan of the product. Typically these are low-rise flat roofed structures built between mid-1960s and mid-1990s primarily of RAAC blocks. At the end of the school summer break in September 2023, the Department for Education (DfE) announced 156 schools in England were ~~effected~~ by RAAC, of those 104 required urgent action and 56 had already undergone repair work. [https://inews.co.uk/news/education/schools-closing-which-list-closed-raac-concrete-how-many-affected-2589742# An estimated and unconfirmed number of 24 schools in England were told to close entirely, and thus were not open for te new school year.]	+	In mid 2023 UK ministers Ministers launched a UK government-wide inquiry into the use of crumbling concrete, in particular occurring in reinforced autoclaved aerated concrete (RAAC). Initial indication is that many of the installations at risk are over 30 years old which may be beyond the expected lifespan of the product. Typically these are low-rise flat roofed structures built between the mid-1960s and mid-1990s primarily of RAAC blocks. At the end of the school summer break in September 2023, the Department for Education (DfE) announced 156 schools in England were affected by RAAC, of those 104 required urgent action and 56 had already undergone repair work. [https://inews.co.uk/news/education/schools-closing-which-list-closed-raac-concrete-how-many-affected-2589742# An estimated and unconfirmed number of 24 schools in England were told to close entirely, and thus were not open for te new school year.]

	= Aircrete =		= Aircrete =

−	Aircrete ~~is often used to describe~~ any concrete product that contains significant pockets of air~~, usually~~ it is prepared with water, cement, and a foaming agent, sometimes with sand but rarely with aggregates. The foaming agent in the case of aircrete, cellular concrete or foamed concrete as it is often called, ~~the foaming agent~~ is prepared into a foam which is then mixed into the slurry to introduce air bubbles into the finished product, making it lighter and having insulative properties. This is as opposed to other ~~method~~ which introduce air entraining foam agents, such as aluminium powder which are introduced earlier and create bubbles through a chemical reaction with the concrete.	+	Aircrete describes any concrete product that contains significant pockets of air. Usually it is prepared with water, cement, and a foaming agent, sometimes with sand but rarely with aggregates. The foaming agent in the case of aircrete, cellular concrete or foamed concrete as it is often called, is prepared into a foam which is then mixed into the slurry to introduce air bubbles into the finished product, making it lighter and having insulative properties. This is as opposed to other methods which introduce air entraining foam agents, such as aluminium powder which are introduced earlier and create bubbles through a chemical reaction with the concrete.

	This product might also be referred to as aerated concrete (AC), air entrained concrete (where bubbles are less than about 1mm in size), air entrapped concrete (where bubbles are larger than about 1mm in size), aerated cellular concrete (ACC), aerated lightweight concrete (ALC) or non-autoclaved aerated concrete, as well as aerated concrete blocks, insulation blocks, breeze blocks or lightweight blocks.		This product might also be referred to as aerated concrete (AC), air entrained concrete (where bubbles are less than about 1mm in size), air entrapped concrete (where bubbles are larger than about 1mm in size), aerated cellular concrete (ACC), aerated lightweight concrete (ALC) or non-autoclaved aerated concrete, as well as aerated concrete blocks, insulation blocks, breeze blocks or lightweight blocks.
Line 75:		Line 75:
	[[File:Aircrete_cat_banner_3.jpg\|link=File:Aircrete_cat_banner_3.jpg]]		[[File:Aircrete_cat_banner_3.jpg\|link=File:Aircrete_cat_banner_3.jpg]]

−	~~== A brief history of aircrete ==~~	+	As early as 1889 Czech Hoffman tested and patented a method of aerating concrete with the use of carbon dioxide, whilst in 1914 Aylsworth and Dyer used aluminium powder and calcium hydroxide to create and patent a porous cementitious mixture. Modern aircrete is created by adding a dense foam in to the concrete mix.
−		+
−	As early as 1889 Czech Hoffman tested and patented a method of aerating concrete with the use of carbon dioxide, whilst in 1914 Aylsworth and Dyer used aluminium powder and calcium hydroxide to create and patent a porous cementitious mixture. Modern aircrete is created ~~using~~ a dense foam in to the concrete mix.	+

	Aircrete, might generally be considered to be the same process used to produce AC but without the autoclaving, ie it is cured naturally, normally in a sealed plastic sheet. The term aircrete itself is said to have been coined by the organisation [https://domegaia.com DomeGaia] much later in 2014, and generally refers to air cured aerated, cellular, foamed, or lightweight concrete. The organisation was set up by the Hajjar Gibran a longtime engineer and design / build contractor, who with Steve Areen, constructed original domed structures in Thailand as housing units. The business is now run by his son and her partner and continues to build across the globe, whilst supporting enthusiasts with other bespoke products such as foam machines and designs.		Aircrete, might generally be considered to be the same process used to produce AC but without the autoclaving, ie it is cured naturally, normally in a sealed plastic sheet. The term aircrete itself is said to have been coined by the organisation [https://domegaia.com DomeGaia] much later in 2014, and generally refers to air cured aerated, cellular, foamed, or lightweight concrete. The organisation was set up by the Hajjar Gibran a longtime engineer and design / build contractor, who with Steve Areen, constructed original domed structures in Thailand as housing units. The business is now run by his son and her partner and continues to build across the globe, whilst supporting enthusiasts with other bespoke products such as foam machines and designs.

Designing Buildings at 05:21, 5 September 2023

2023-09-05T05:21:59Z

← Older revision		Revision as of 05:21, 5 September 2023
Line 51:		Line 51:
	= Reinforced Autoclaved Aerated Concrete RAAC =		= Reinforced Autoclaved Aerated Concrete RAAC =

−	Reinforced autoclaved aerated concrete (RAAC) is essentially ~~what it implies, it is~~ the same autoclaved aerated concrete(AAC) ~~product~~ but containing reinforcement elements which improve tensile strength and allow larger, thinner panels to be made from the same aerated product.	+	Reinforced autoclaved aerated concrete (RAAC) is essentially the same autoclaved aerated concrete(AAC) but containing reinforcement elements which improve tensile strength and allow larger, thinner panels to be made from the same aerated product.

	== [[File:RAAC_1000.jpg\|link=File:RAAC_1000.jpg]] ==		== [[File:RAAC_1000.jpg\|link=File:RAAC_1000.jpg]] ==
−
−	~~== A brief history of RAAC ==~~

	RAAC was first developed not long after the commercial development of autoclaved aerated concrete (AAC in the 1930's), the first reinforced AAC products were also developed in Sweden (where AAC was developed) not by the original manufacturer of AAC but by a competitor. The goal of developing reinforced elements was to be able to manufacture an entire building from AAC based systems, including panels and floor elements.		RAAC was first developed not long after the commercial development of autoclaved aerated concrete (AAC in the 1930's), the first reinforced AAC products were also developed in Sweden (where AAC was developed) not by the original manufacturer of AAC but by a competitor. The goal of developing reinforced elements was to be able to manufacture an entire building from AAC based systems, including panels and floor elements.

−	RAAC products were further improved by German firm and began establish themselves in the market by the 1940's. ~~After the war and effectively between~~ 1945 and 1975 mass building programs across Europe searched for modern methods to construct buildings quickly and cost effectively, and as such many innovative new products were developed during this period (known collectively as post-war building materials). AAC and RAAC or lightweight concrete systems became key elements in many of these building programmes, alongside other products developed during the same period such as insulation products, glazing and window frame systems, and a variety of prefabricated and precast systems including lightweight concrete.	+	RAAC products were further improved by a German firm and began establish themselves in the market by the 1940's. Between 1945 and 1975 mass building programs across Europe searched for modern methods to construct buildings quickly and cost effectively, and as such many innovative new products were developed during this period (known collectively as post-war building materials). AAC and RAAC or lightweight concrete systems became key elements in many of these building programmes, alongside other products developed during the same period such as insulation products, glazing and window frame systems, and a variety of prefabricated and precast systems including lightweight concrete.

	== Contemporary issues with RAAC ==		== Contemporary issues with RAAC ==

−	Crumbling concrete describes failure where concrete parts ~~are filling~~ off in chunks and the strength of the overall material is compromised. It can simply be the result of ageing but maybe worsened where the initial pour was not managed correctly, where reinforcement elements are beginning to corrode or where the material is exposed to harsh elements or mechanical damage. This type of failure has started to be associated more closely with RAAC, the reasons vary, with specific cases but some RAAC installations were built as early as the 1950's and so maybe seeing issues because the products have ~~surpassed~~ their expected ~~accepted~~ lifespan. In many cases issues arise through the failure of water proof coverings, such as flat roofs, allowing the exteral surface of the RAAC to become wet, once damp over time, it can effectively soak up moisture, similar to a sponge, leading to corrosion of the reinforcement. Other and related issues with newer product installations may indeed be as a result of either poor design or fabrication / installation issues often relating to the location of the reinforcement to near the edges (relating again to moisture and corosion) and the concrete mix.	+	Crumbling concrete describes failure where concrete parts fall off in chunks and the strength of the overall material is compromised. It can simply be the result of ageing but maybe worsened where the initial pour was not managed correctly, where reinforcement elements are beginning to corrode or where the material is exposed to harsh elements or mechanical damage. This type of failure has started to be associated more closely with RAAC, the reasons vary, with specific cases but some RAAC installations were built as early as the 1950's and so maybe seeing issues because the products have exceeded their expected lifespan. In many cases issues arise through the failure of water proof coverings, such as flat roofs, allowing the exteral surface of the RAAC to become wet, once damp over time, it can effectively soak up moisture, similar to a sponge, leading to corrosion of the reinforcement. Other and related issues with newer product installations may indeed be as a result of either poor design or fabrication / installation issues often relating to the location of the reinforcement to near the edges (relating again to moisture and corosion) and the concrete mix.

	In December 2022 the UK Government published 'Reinforced autoclaved aerated concrete (RAAC): estates guidance'. The guidance set out a 5-stage approach to the identification and management of RAAC in educational buildings, where these maybe present in floors, walls and roofs (pitched and flat) of buildings constructed or modified between the 1950s and mid-1990s. This guidance outlined initial steps that should be taken by those responsible for the management of educational buildings, how to procure building professional’s services when specialist advice is needed. It was designed for all parties involved in the identification and management of RAAC, including estates managers and those providing specialist advice, can use this guidance.		In December 2022 the UK Government published 'Reinforced autoclaved aerated concrete (RAAC): estates guidance'. The guidance set out a 5-stage approach to the identification and management of RAAC in educational buildings, where these maybe present in floors, walls and roofs (pitched and flat) of buildings constructed or modified between the 1950s and mid-1990s. This guidance outlined initial steps that should be taken by those responsible for the management of educational buildings, how to procure building professional’s services when specialist advice is needed. It was designed for all parties involved in the identification and management of RAAC, including estates managers and those providing specialist advice, can use this guidance.

Designing Buildings at 05:18, 5 September 2023

2023-09-05T05:18:51Z

Show changes

Editor at 05:15, 5 September 2023

2023-09-05T05:15:43Z

← Older revision		Revision as of 05:15, 5 September 2023
Line 59:		Line 59:
	Reinforced autoclaved aerated concrete (RAAC) is essentially what it implies, it is the same autoclaved aerated concrete (AAC) product but containing reinforcement elements which improve tensile strength and allow larger, thinner panels to be made from the same aerated product. Many post-war buildings from the 1950's to the 1970's made use of this technology.		Reinforced autoclaved aerated concrete (RAAC) is essentially what it implies, it is the same autoclaved aerated concrete (AAC) product but containing reinforcement elements which improve tensile strength and allow larger, thinner panels to be made from the same aerated product. Many post-war buildings from the 1950's to the 1970's made use of this technology.

−	== [[File:RAAC_1000.jpg\|link=File:RAAC_1000.jpg]] ==	+	[[File:RAAC_1000.jpg\|link=File:RAAC_1000.jpg]]

	== A brief history of RAAC ==		== A brief history of RAAC ==

Editor at 05:15, 5 September 2023

2023-09-05T05:15:04Z

Editor at 04:34, 5 September 2023

2023-09-05T04:34:00Z

Editor at 21:10, 4 September 2023

2023-09-04T21:10:42Z

← Older revision		Revision as of 21:10, 4 September 2023
Line 1:		Line 1:
−	[[File:~~Foamed Concrete AZ 1000~~.jpg]]	+	[[File:Foamed_Concrete_AZ_1000.jpg\|link=File:Foamed_Concrete_AZ_1000.jpg]]
		+
		+	= Introduction to light weight concrete solutions =

	Lightweight concrete, sometimes referred to as cellular concrete is a general term covering a variety of concrete solutions with reduced weights, these products vary but in general will include lightweight aggregate concrete, aerated concrete, autoclaved aerated concrete and what is known as aircrete. Many variations on these products exist, adjusting ingredients and processes to improve performance, as well as introducing other elements such as for example Reinforced Autoclaved Aerated Concrete or RAAC or significantly different approaches such as no-fines concrete.		Lightweight concrete, sometimes referred to as cellular concrete is a general term covering a variety of concrete solutions with reduced weights, these products vary but in general will include lightweight aggregate concrete, aerated concrete, autoclaved aerated concrete and what is known as aircrete. Many variations on these products exist, adjusting ingredients and processes to improve performance, as well as introducing other elements such as for example Reinforced Autoclaved Aerated Concrete or RAAC or significantly different approaches such as no-fines concrete.

−	[[File:~~LWAC Leca pellets 1000~~.jpg]]	+	[[File:LWAC_Leca_pellets_1000.jpg\|link=File:LWAC_Leca_pellets_1000.jpg]]

	= Lightweight Aggregate Concrete LWAC =		= Lightweight Aggregate Concrete LWAC =
Line 9:		Line 11:
	Lightweight concrete is a general term for various concrete solutions with reduced weight including air pockets, lightweight aggregate concrete is a specific solid concrete solution that makes use light weight aggregates with minimal air voids. It is usually made with a mixture of lightweight coarse aggregates such as expanded shale or slate (heated to over 1000 degrees C), lightweight expanded clay aggregate (LECA or Hydroton), pumice stone, ash, perlite and some other minerals.		Lightweight concrete is a general term for various concrete solutions with reduced weight including air pockets, lightweight aggregate concrete is a specific solid concrete solution that makes use light weight aggregates with minimal air voids. It is usually made with a mixture of lightweight coarse aggregates such as expanded shale or slate (heated to over 1000 degrees C), lightweight expanded clay aggregate (LECA or Hydroton), pumice stone, ash, perlite and some other minerals.

−	[[File:~~Lecablock 1000~~.jpg]]	+	[[File:Lecablock_1000.jpg\|link=File:Lecablock_1000.jpg]]

	== A brief history of LWAC ==		== A brief history of LWAC ==
Line 29:		Line 31:
	When the air content within concrete is about 1.5% - 3% and bubbles are relatively large in size, over around 1mm and randomly located throughout the mix it is referred to as entrapped air, mostly an unintended consequence of mixing concrete, with insufficient agitation. When the air is uniformly distributed in microscopic bubbles of less than 1mm it is referred to as air entrainment. When it makes up between 3%-8% by volume of the finished product it is often done so to improve the performance under freeze thaw conditions. Aerated concrete or cellular concrete however normally refers to concrete products that have a higher content around 25-25% of air bubbles, which may be higher is no structural performance is required.		When the air content within concrete is about 1.5% - 3% and bubbles are relatively large in size, over around 1mm and randomly located throughout the mix it is referred to as entrapped air, mostly an unintended consequence of mixing concrete, with insufficient agitation. When the air is uniformly distributed in microscopic bubbles of less than 1mm it is referred to as air entrainment. When it makes up between 3%-8% by volume of the finished product it is often done so to improve the performance under freeze thaw conditions. Aerated concrete or cellular concrete however normally refers to concrete products that have a higher content around 25-25% of air bubbles, which may be higher is no structural performance is required.

−	[[File:~~AAC tape~~- ~~detail~~.jpg]]	+	[[File:AAC_tape-_detail.jpg\|link=File:AAC_tape-_detail.jpg]]

	== A brief history of AC ==		== A brief history of AC ==
Line 39:		Line 41:
	Autoclaved Aerated Concrete (AAC) is essentially very similar to aerated concrete only tht it is cured under heat and pressure in an autoclave, to produce a lightweight fire and mould resistant product with insulative qualities as well as strength and durability. Composed of quartz sand, calcined gypsum, lime, Portland cement, water and aluminium powder it is used to form blocks, lintels, wall, floor and roof panels as well as cladding units.		Autoclaved Aerated Concrete (AAC) is essentially very similar to aerated concrete only tht it is cured under heat and pressure in an autoclave, to produce a lightweight fire and mould resistant product with insulative qualities as well as strength and durability. Composed of quartz sand, calcined gypsum, lime, Portland cement, water and aluminium powder it is used to form blocks, lintels, wall, floor and roof panels as well as cladding units.

−	[[File:~~AAC bubbles vol 1 copy~~.jpg]]	+	[[File:AAC_bubbles_vol_1_copy.jpg\|link=File:AAC_bubbles_vol_1_copy.jpg]]

	== A brief history of AAC ==		== A brief history of AAC ==
Line 57:		Line 59:
	Reinforced autoclaved aerated concrete (RAAC) is essentially what it implies, it is the same autoclaved aerated concrete(AAC) product but containing reinforcement elements which improve tensile strength and allow larger, thinner panels to be made from the same aerated product.		Reinforced autoclaved aerated concrete (RAAC) is essentially what it implies, it is the same autoclaved aerated concrete(AAC) product but containing reinforcement elements which improve tensile strength and allow larger, thinner panels to be made from the same aerated product.

−	== [[File:~~RAAC 1000~~.jpg]] ==	+	== [[File:RAAC_1000.jpg\|link=File:RAAC_1000.jpg]] ==

	== A brief history of RAAC ==		== A brief history of RAAC ==
Line 79:		Line 81:
	This product might also be referred to as aerated concrete (AC), air entrained concrete (where bubbles are less than about 1mm in size), air entrapped concrete (where bubbles are larger than about 1mm in size), aerated cellular concrete (ACC), aerated lightweight concrete (ALC) or non-autoclaved aerated concrete, as well as aerated concrete blocks, insulation blocks, breeze blocks or lightweight blocks.		This product might also be referred to as aerated concrete (AC), air entrained concrete (where bubbles are less than about 1mm in size), air entrapped concrete (where bubbles are larger than about 1mm in size), aerated cellular concrete (ACC), aerated lightweight concrete (ALC) or non-autoclaved aerated concrete, as well as aerated concrete blocks, insulation blocks, breeze blocks or lightweight blocks.

−	[[File:~~Aircrete cat banner 3~~.jpg]]	+	[[File:Aircrete_cat_banner_3.jpg\|link=File:Aircrete_cat_banner_3.jpg]]

	== A brief history of aircrete ==		== A brief history of aircrete ==

Editor at 21:09, 4 September 2023

2023-09-04T21:09:15Z

← Older revision		Revision as of 21:09, 4 September 2023
Line 1:		Line 1:
		+	[[File:Foamed Concrete AZ 1000.jpg]]
		+
	Lightweight concrete, sometimes referred to as cellular concrete is a general term covering a variety of concrete solutions with reduced weights, these products vary but in general will include lightweight aggregate concrete, aerated concrete, autoclaved aerated concrete and what is known as aircrete. Many variations on these products exist, adjusting ingredients and processes to improve performance, as well as introducing other elements such as for example Reinforced Autoclaved Aerated Concrete or RAAC or significantly different approaches such as no-fines concrete.		Lightweight concrete, sometimes referred to as cellular concrete is a general term covering a variety of concrete solutions with reduced weights, these products vary but in general will include lightweight aggregate concrete, aerated concrete, autoclaved aerated concrete and what is known as aircrete. Many variations on these products exist, adjusting ingredients and processes to improve performance, as well as introducing other elements such as for example Reinforced Autoclaved Aerated Concrete or RAAC or significantly different approaches such as no-fines concrete.

−	= Lightweight Aggregate Concrete ~~LAWC~~ =	+	[[File:LWAC Leca pellets 1000.jpg]]
		+
		+	= Lightweight Aggregate Concrete LWAC =

	Lightweight concrete is a general term for various concrete solutions with reduced weight including air pockets, lightweight aggregate concrete is a specific solid concrete solution that makes use light weight aggregates with minimal air voids. It is usually made with a mixture of lightweight coarse aggregates such as expanded shale or slate (heated to over 1000 degrees C), lightweight expanded clay aggregate (LECA or Hydroton), pumice stone, ash, perlite and some other minerals.		Lightweight concrete is a general term for various concrete solutions with reduced weight including air pockets, lightweight aggregate concrete is a specific solid concrete solution that makes use light weight aggregates with minimal air voids. It is usually made with a mixture of lightweight coarse aggregates such as expanded shale or slate (heated to over 1000 degrees C), lightweight expanded clay aggregate (LECA or Hydroton), pumice stone, ash, perlite and some other minerals.

−	== A brief history of ~~LAWC~~ ==	+	[[File:Lecablock 1000.jpg]]
		+
		+	== A brief history of LWAC ==

	Some of the earliest lightweight concretes, even before the Roman empire used pumice from Italy or Greece with burnt and hydrated lime. The Romans however by removing the impurities of lime such as silica, alumina and iron oxides started to produce stronger binders, known as grey lime, and stronger concrete, which today we refer to as Roman concrete. As part of this development, lightweight aggregates continued to be used but with the use grey lime producing stronger light weight concrete construction results.		Some of the earliest lightweight concretes, even before the Roman empire used pumice from Italy or Greece with burnt and hydrated lime. The Romans however by removing the impurities of lime such as silica, alumina and iron oxides started to produce stronger binders, known as grey lime, and stronger concrete, which today we refer to as Roman concrete. As part of this development, lightweight aggregates continued to be used but with the use grey lime producing stronger light weight concrete construction results.
Line 22:		Line 28:

	When the air content within concrete is about 1.5% - 3% and bubbles are relatively large in size, over around 1mm and randomly located throughout the mix it is referred to as entrapped air, mostly an unintended consequence of mixing concrete, with insufficient agitation. When the air is uniformly distributed in microscopic bubbles of less than 1mm it is referred to as air entrainment. When it makes up between 3%-8% by volume of the finished product it is often done so to improve the performance under freeze thaw conditions. Aerated concrete or cellular concrete however normally refers to concrete products that have a higher content around 25-25% of air bubbles, which may be higher is no structural performance is required.		When the air content within concrete is about 1.5% - 3% and bubbles are relatively large in size, over around 1mm and randomly located throughout the mix it is referred to as entrapped air, mostly an unintended consequence of mixing concrete, with insufficient agitation. When the air is uniformly distributed in microscopic bubbles of less than 1mm it is referred to as air entrainment. When it makes up between 3%-8% by volume of the finished product it is often done so to improve the performance under freeze thaw conditions. Aerated concrete or cellular concrete however normally refers to concrete products that have a higher content around 25-25% of air bubbles, which may be higher is no structural performance is required.
		+
		+	[[File:AAC tape- detail.jpg]]

	== A brief history of AC ==		== A brief history of AC ==
Line 30:		Line 38:

	Autoclaved Aerated Concrete (AAC) is essentially very similar to aerated concrete only tht it is cured under heat and pressure in an autoclave, to produce a lightweight fire and mould resistant product with insulative qualities as well as strength and durability. Composed of quartz sand, calcined gypsum, lime, Portland cement, water and aluminium powder it is used to form blocks, lintels, wall, floor and roof panels as well as cladding units.		Autoclaved Aerated Concrete (AAC) is essentially very similar to aerated concrete only tht it is cured under heat and pressure in an autoclave, to produce a lightweight fire and mould resistant product with insulative qualities as well as strength and durability. Composed of quartz sand, calcined gypsum, lime, Portland cement, water and aluminium powder it is used to form blocks, lintels, wall, floor and roof panels as well as cladding units.
		+
		+	[[File:AAC bubbles vol 1 copy.jpg]]

	== A brief history of AAC ==		== A brief history of AAC ==
Line 46:		Line 56:

	Reinforced autoclaved aerated concrete (RAAC) is essentially what it implies, it is the same autoclaved aerated concrete(AAC) product but containing reinforcement elements which improve tensile strength and allow larger, thinner panels to be made from the same aerated product.		Reinforced autoclaved aerated concrete (RAAC) is essentially what it implies, it is the same autoclaved aerated concrete(AAC) product but containing reinforcement elements which improve tensile strength and allow larger, thinner panels to be made from the same aerated product.
		+
		+	== [[File:RAAC 1000.jpg]] ==

	== A brief history of RAAC ==		== A brief history of RAAC ==
Line 66:		Line 78:

	This product might also be referred to as aerated concrete (AC), air entrained concrete (where bubbles are less than about 1mm in size), air entrapped concrete (where bubbles are larger than about 1mm in size), aerated cellular concrete (ACC), aerated lightweight concrete (ALC) or non-autoclaved aerated concrete, as well as aerated concrete blocks, insulation blocks, breeze blocks or lightweight blocks.		This product might also be referred to as aerated concrete (AC), air entrained concrete (where bubbles are less than about 1mm in size), air entrapped concrete (where bubbles are larger than about 1mm in size), aerated cellular concrete (ACC), aerated lightweight concrete (ALC) or non-autoclaved aerated concrete, as well as aerated concrete blocks, insulation blocks, breeze blocks or lightweight blocks.
		+
		+	[[File:Aircrete cat banner 3.jpg]]

	== A brief history of aircrete ==		== A brief history of aircrete ==
Line 104:		Line 118:
	* Types of concrete.		* Types of concrete.
	* Portland cement.		* Portland cement.
		+
		+	= External links =
		+
		+	[https://www.youtube.com/watch?v=t6MN6-VsGgM&t=1s https://www.youtube.com/watch?v=t6MN6-VsGgM&t=1s]

	[[Category:DCN_Commentary]] [[Category:DCN_Definition]] [[Category:DCN_Product_Knowledge]] [[Category:Definitions]] [[Category:History]] [[Category:Standards_/_measurements]] [[Category:Sustainability]] [[Category:Products_/_components]]		[[Category:DCN_Commentary]] [[Category:DCN_Definition]] [[Category:DCN_Product_Knowledge]] [[Category:Definitions]] [[Category:History]] [[Category:Standards_/_measurements]] [[Category:Sustainability]] [[Category:Products_/_components]]

Editor at 15:27, 3 September 2023

2023-09-03T15:27:44Z

← Older revision		Revision as of 15:27, 3 September 2023
Line 3:		Line 3:
	= Lightweight Aggregate Concrete LAWC =		= Lightweight Aggregate Concrete LAWC =

−	Lightweight concrete is a general term for various concrete solutions with reduced weight including air pockets, lightweight aggregate concrete is a specific solid concrete solution that makes use light weight aggregates with minimal air voids. It is usually made with a mixture of lightweight coarse aggregates such as expanded shale or slate (heated to over 1000 degrees C), lightweight expanded clay aggregate (LECA), pumice stone, ash, perlite and some other minerals.	+	Lightweight concrete is a general term for various concrete solutions with reduced weight including air pockets, lightweight aggregate concrete is a specific solid concrete solution that makes use light weight aggregates with minimal air voids. It is usually made with a mixture of lightweight coarse aggregates such as expanded shale or slate (heated to over 1000 degrees C), lightweight expanded clay aggregate (LECA or Hydroton), pumice stone, ash, perlite and some other minerals.

	== A brief history of LAWC ==		== A brief history of LAWC ==

Editor at 15:24, 3 September 2023

2023-09-03T15:24:36Z

← Older revision		Revision as of 15:24, 3 September 2023
Line 3:		Line 3:
	= Lightweight Aggregate Concrete LAWC =		= Lightweight Aggregate Concrete LAWC =

−	Lightweight concrete is a general term for various concrete solutions with reduced weight including air pockets, lightweight aggregate concrete is a specific solid concrete solution that makes use light weight aggregates with minimal air voids. It is usually made with a mixture of lightweight coarse aggregates such as expanded shale (~~shale~~ heated to over 1000 degrees C), ~~slate,~~ clay, pumice stone, ash, perlite and some other minerals.	+	Lightweight concrete is a general term for various concrete solutions with reduced weight including air pockets, lightweight aggregate concrete is a specific solid concrete solution that makes use light weight aggregates with minimal air voids. It is usually made with a mixture of lightweight coarse aggregates such as expanded shale or slate (heated to over 1000 degrees C), lightweight expanded clay aggregate (LECA), pumice stone, ash, perlite and some other minerals.

	== A brief history of LAWC ==		== A brief history of LAWC ==

← Older revision		Revision as of 04:34, 5 September 2023
Line 3:		Line 3:
	= Introduction to light weight concrete solutions =		= Introduction to light weight concrete solutions =

−	Lightweight concrete, sometimes referred to as cellular concrete is a general term covering a variety of concrete solutions with reduced weights, these products vary but in general will include lightweight aggregate concrete, aerated concrete, autoclaved aerated concrete and what is known as aircrete. Many variations on these products exist, adjusting ingredients and processes to improve performance, as well as introducing other elements such as for example Reinforced Autoclaved Aerated Concrete or RAAC or significantly different approaches such as no-fines concrete.	+	Lightweight concrete, sometimes referred to as cellular concrete is a general term covering a variety of concrete solutions with reduced weights, these products vary but in general will include lightweight aggregate concrete, aerated concrete, autoclaved aerated concrete and what is known as aircrete. Many variations on these products exist, adjusting ingredients and processes to improve performance, as well as introducing other elements such as for example Reinforced Autoclaved Aerated Concrete or RAAC, which has recently come under some notoriety or significantly different approaches such as no-fines concrete, simple with larger agregate and larger gaps between.

	[[File:LWAC_Leca_pellets_1000.jpg\|link=File:LWAC_Leca_pellets_1000.jpg]]		[[File:LWAC_Leca_pellets_1000.jpg\|link=File:LWAC_Leca_pellets_1000.jpg]]
Line 69:		Line 69:
	== Contemporary issues with RAAC ==		== Contemporary issues with RAAC ==

−	Crumbling concrete describes failure where concrete parts are filling off in chunks and the strength of the overall material is compromised. It can simply be the result of ageing but maybe worsened where the initial pour was not managed correctly, where reinforcement elements are beginning to corrode or where the material is exposed to harsh elements or mechanical damage. This type of failure has started to be associated more closely with RAAC, the reasons vary with specific cases but some RAAC installations were built as early as the 1950's and so maybe seeing issues because the products have surpassed their expected accepted lifespan. Other issues with newer product installations may indeed be as a result of either poor design or fabrication / installation issues often ~~related~~ to the location of the reinforcement and concrete mix.	+	Crumbling concrete describes failure where concrete parts are filling off in chunks and the strength of the overall material is compromised. It can simply be the result of ageing but maybe worsened where the initial pour was not managed correctly, where reinforcement elements are beginning to corrode or where the material is exposed to harsh elements or mechanical damage. This type of failure has started to be associated more closely with RAAC, the reasons vary, with specific cases but some RAAC installations were built as early as the 1950's and so maybe seeing issues because the products have surpassed their expected accepted lifespan. In many cases issues arise through the failure of water proof coverings, such as flat roofs, allowing the exteral surface of the RAAC to become wet, once damp over time, it can effectively soak up moisture, similar to a sponge, leading to corrosion of the reinforcement. Other and related issues with newer product installations may indeed be as a result of either poor design or fabrication / installation issues often relating to the location of the reinforcement to near the edges (relating again to moisture and corosion) and the concrete mix.

	In December 2022 the UK Government published 'Reinforced autoclaved aerated concrete (RAAC): estates guidance'. The guidance set out a 5-stage approach to the identification and management of RAAC in educational buildings, where these maybe present in floors, walls and roofs (pitched and flat) of buildings constructed or modified between the 1950s and mid-1990s. This guidance outlined initial steps that should be taken by those responsible for the management of educational buildings, how to procure building professional’s services when specialist advice is needed. It was designed for all parties involved in the identification and management of RAAC, including estates managers and those providing specialist advice, can use this guidance.		In December 2022 the UK Government published 'Reinforced autoclaved aerated concrete (RAAC): estates guidance'. The guidance set out a 5-stage approach to the identification and management of RAAC in educational buildings, where these maybe present in floors, walls and roofs (pitched and flat) of buildings constructed or modified between the 1950s and mid-1990s. This guidance outlined initial steps that should be taken by those responsible for the management of educational buildings, how to procure building professional’s services when specialist advice is needed. It was designed for all parties involved in the identification and management of RAAC, including estates managers and those providing specialist advice, can use this guidance.

−	In mid 2023 UK ministers Ministers launched a UK government-wide inquiry into the use of crumbling concrete, in particular occurring in reinforced autoclaved aerated concrete (RAAC). Initial indication is that many of the installations at risk are over 30 years old which may be beyond the expected lifespan of the product. Typically these are low-rise flat roofed structures built between mid-1960s and mid-1990s primarily of RAAC blocks.	+	In mid 2023 UK ministers Ministers launched a UK government-wide inquiry into the use of crumbling concrete, in particular occurring in reinforced autoclaved aerated concrete (RAAC). Initial indication is that many of the installations at risk are over 30 years old which may be beyond the expected lifespan of the product. Typically these are low-rise flat roofed structures built between mid-1960s and mid-1990s primarily of RAAC blocks. At the end of the school summer break in September 2023, the Department for Education (DfE) announced 156 schools in England were effected by RAAC, of those 104 required urgent action and 56 had already undergone repair work. [https://inews.co.uk/news/education/schools-closing-which-list-closed-raac-concrete-how-many-affected-2589742# An estimated and unconfirmed number of 24 schools in England were told to close entirely, and thus were not open for te new school year.]

	= Aircrete =		= Aircrete =
Line 87:		Line 87:
	As early as 1889 Czech Hoffman tested and patented a method of aerating concrete with the use of carbon dioxide, whilst in 1914 Aylsworth and Dyer used aluminium powder and calcium hydroxide to create and patent a porous cementitious mixture. Modern aircrete is created using a dense foam in to the concrete mix.		As early as 1889 Czech Hoffman tested and patented a method of aerating concrete with the use of carbon dioxide, whilst in 1914 Aylsworth and Dyer used aluminium powder and calcium hydroxide to create and patent a porous cementitious mixture. Modern aircrete is created using a dense foam in to the concrete mix.

−	Aircrete, might generally be considered to be the same process used to produce AC but without the autoclaving, ie it is cured naturally, normally in a sealed plastic sheet. The term aircrete itself is said to have been coined by the organisation DomeGaia much later in 2014, and generally refers to air cured aerated, cellular, foamed, or lightweight concrete. The organisation was set up by the Hajjar Gibran a longtime engineer and design / build contractor, who with Steve Areen, constructed original domed structures in Thailand as housing units. The business is now run by his son and her partner and continues to build across the globe, whilst supporting enthusiasts with other bespoke products such as foam machines and designs.	+	Aircrete, might generally be considered to be the same process used to produce AC but without the autoclaving, ie it is cured naturally, normally in a sealed plastic sheet. The term aircrete itself is said to have been coined by the organisation [https://domegaia.com DomeGaia] much later in 2014, and generally refers to air cured aerated, cellular, foamed, or lightweight concrete. The organisation was set up by the Hajjar Gibran a longtime engineer and design / build contractor, who with Steve Areen, constructed original domed structures in Thailand as housing units. The business is now run by his son and her partner and continues to build across the globe, whilst supporting enthusiasts with other bespoke products such as foam machines and designs.

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