Integrated Buildings & Structures

I'm doing a project on increasing strength in foam concrete. Currently i'm getting around 10 MPa which is not enough to convert it into a structural material. I need at least 15 MPa in order to use it in a live material in construction what admixtures I can impart in to increase the corresponding compressive and tensile strengths? I already tried PP fibers which does not help in gaining additional strength. I'm using cement and fly ash in the ratio 1:1 and protein based foaming agent. Thanks in advance. 

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Praveen Anand S.M.ASCE
Chennai TN
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Hi there,

You would be able to get higher strength by adding aggregate, but aggregate may settle in aerated concrete. I might also try using a superplasticizer with 1/4" agg. My two cents, let me know if you succeed.


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Elliot House P.E., S.M.ASCE
W.B. Clausen Structural Engineers
Emeryville CA
(415)444-4144
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To the point about aggregates we've used viscosity modifying agent (VMA's) along with additives in self-consolidating concrete (SCC) to keep aggregates in suspension in a thin mix.  To your basic point, however, we've also been actively investigating the use of earthen materials as structure. There has been a good deal of progress in understanding the basic mechanics of low-strength, low-carbon footprint materials of late (twenty years). 10-12 MPa is not unusual.  The Auroville Institute and some work also at Bangalore University there in India have been active in the area.

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C Michael Donoghue P.E., M.ASCE
Principal
Maritech Engr. ,Inc.
Austin TX
(512) 326-3232
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Flowability level of this foam concrete is already high, no need of compaction already and moreover adding VMA gives it more flowability than the previous version which reduces the strength in latter manner. 

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Praveen Anand S.M.ASCE
Chennai TN
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Original Message:
Sent: 01-20-2019 09:34
From: C Michael Donoghue
Subject: Foam concrete

To the point about aggregates we've used viscosity modifying agent (VMA's) along with additives in self-consolidating concrete (SCC) to keep aggregates in suspension in a thin mix.  To your basic point, however, we've also been actively investigating the use of earthen materials as structure. There has been a good deal of progress in understanding the basic mechanics of low-strength, low-carbon footprint materials of late (twenty years). 10-12 MPa is not unusual.  The Auroville Institute and some work also at Bangalore University there in India have been active in the area.

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C Michael Donoghue P.E., M.ASCE
Principal
Maritech Engr. ,Inc.
Austin TX
(512) 326-3232
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Generally, with foam concrete and cellular concrete your wet mix density will be directly proportional to strength.  Try reducing the foaming agent and water a bit to achieve a heavier wet material and see if that helps.  The polypropylene fibers, while they do add a bit to strength, are mostly for crack control and are unlikely to get you the strength gains you're looking for.  Keep your mix consistent in subsequent pours by trying to match the wet density at placement and it should help keep the material relatively uniform.

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Cliff Jones P.E., S.E., M.ASCE
Jensen Hughes
Portland OR
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Yeah got it thanks sir.

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Praveen Anand S.M.ASCE
Chennai TN
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Original Message:
Sent: 01-20-2019 11:46
From: Cliff Jones
Subject: Foam concrete

Generally, with foam concrete and cellular concrete your wet mix density will be directly proportional to strength.  Try reducing the foaming agent and water a bit to achieve a heavier wet material and see if that helps.  The polypropylene fibers, while they do add a bit to strength, are mostly for crack control and are unlikely to get you the strength gains you're looking for.  Keep your mix consistent in subsequent pours by trying to match the wet density at placement and it should help keep the material relatively uniform.

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Cliff Jones P.E., S.E., M.ASCE
Jensen Hughes
Portland OR
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Hi,

Tell me how much is your density?

Thank you!

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Ali Agakhanloo S.E., Aff.M.ASCE
Civil Enginner
Tabriz
(98)41347 5433
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Around 1500 kg per cubic metre. And also what can be done to increase the density, sir?

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Praveen Anand S.M.ASCE
Chennai TN
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Original Message:
Sent: 01-21-2019 00:40
From: Ali Agakhanloo
Subject: Foam concrete

Hi,

Tell me how much is your density?

Thank you!

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Ali Agakhanloo S.E., Aff.M.ASCE
Civil Enginner
Tabriz
(98)41347 5433
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FOAM CONCRETE CHARACTERISTIC PROPERTIES

Basic concrete constituents of aggregates and cement have cement paste as the binding material (which is cement and water).

The cement paste as the binder of aggregates provides the binding energy requires for an homogeneous mixture, the addition of a foaming agent accordingly will reduced the chemical reaction of the cement paste, and the binding energy requirements.

Therefore, to have a significant improvement in strength, the foaming agent proportion should be reduced significantly, and also adequate concrete mix design must be implemented, using the trial mix approach in order to determine the optima foam concentration.

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Olusegun Afolabi P.E., M.ASCE
University of Lagos
Lagos
234803 4248600
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Thanks sir! I Will try to implement this.

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Praveen Anand S.M.ASCE
Chennai TN
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Original Message:
Sent: 01-22-2019 01:04
From: Olusegun Afolabi
Subject: Foam concrete

FOAM CONCRETE CHARACTERISTIC PROPERTIES

Basic concrete constituents of aggregates and cement have cement paste as the binding material (which is cement and water).

The cement paste as the binder of aggregates provides the binding energy requires for an homogeneous mixture, the addition of a foaming agent accordingly will reduced the chemical reaction of the cement paste, and the binding energy requirements.

Therefore, to have a significant improvement in strength, the foaming agent proportion should be reduced significantly, and also adequate concrete mix design must be implemented, using the trial mix approach in order to determine the optima foam concentration.

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Olusegun Afolabi P.E., M.ASCE
University of Lagos
Lagos
234803 4248600
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