While the crystalline system is one of the best for U.G structures, there are some limitations. It doesnot have crack bridging ability due to low elongation properties. The concrete is known to develop cracks in future due to sub soil conditions, sulphate attacks, corrossion, different moments developed in the concrete structure. These future cracks / crevices pose challenge to crystalline system
By
P V Raman, Director - Engineering,
| 07 04 2010 13:03:24 +0000
Mr Arun Thanks for the link. Just for your info, I have used Tons of XYPEX bentonite strips on East link tunnel in Melbourne for lining joint waterproofing, but for main lining waterproofing I used Membrane. I am also using Xype on my current project but not for all the waterproofing applications. Xypex no doubt has some good products. The point I am trying to make is that this being an technical forum, advices given should be independent and not biased. While one has the right to promote their product but this should not be done at the cost of not promoting right technical application.
By
P.P.Boni , McConnell Dowell ( Tunnel & Underground),
| 06 11 2010 23:22:31 +0000
Mr.Arun, I have used tons of xypex bentonite strips here is Australia on my projects especially bentonite strips on east link tunnel for joint management but for lining it was still membrane because Xypex was ruled out due to various reason. What I am trying to conveyand you would agree that this is a technical forum and advice given here should be independent and not based on any personal interest that one might have in a particular product. By the way, I am still using Xypex ( an it is a good but product) on my current project for not for all the structures where it cannot replace membrane
By
P.P.Boni , McConnell Dowell ( Tunnel & Underground),
| 06 11 2010 23:05:35 +0000
Arun, You post seems to suggest that concrete additives ( will not specify the brands) is the only way to go. I totally disagree with you. May be you can provide us a list of the projects- Underground with a durability requirement of 100 years and high hydrostatic head and inflow of water where only additive has been used as main defence against waterproofing. List of projects completed in the last 5 yrs will be great. I have been using such additives before, but now only for limitied applications. I agree that membrane do need surface to be prepared but they provide one of the best solutions too ( again in specific application) and in no way impact on the breathing of the concrete. It is important to understand the need and not to rule out one or other solution.
By
P.P.Boni , McConnell Dowell ( Tunnel & Underground),
| 06 09 2010 22:31:24 +0000
For waterproofing underground structures, one has to understand what one is trying to achieve. Concrete, by it's nature, can never be made totally impervious by itself. However, water ingress can be limited by providing denser concrete. This can be achieved by proper mix design, use of correct admixtures and proper compaction after placing. If one misses out on any of these, water ingress reaches intolerable levels. Before using any chemicals for waterproofing, one must understand the mechanisms by which these stop water ingress. The name Crystaline would suggest a liquid chemical which crystalizes in the pores of concrete thus effectively blocking the pores. The danger with such chemicals is that if they are expansive types, using them in excess may actually weaken the concrete by inducing micro cracking of concrete when they solidify and expand inside pores. In my opinion, the foremost requirement in underground construction is providing sound, dense concrete. This is then to be supplemented with impervious membranes on the external surface, to avoid chlorides and sulphates coming in direct contact with concrete. Such membranes must be elastic and able to strech and contract with the concrete without cracking or losing adhesion to concrete surface. Latex or silicone based products are best suited for this purpose. These membranes are usually to be protected by a layer of plaster against abrasion during backfilling.
By
Basab Ghosh, General Manager (Operations), Saipem India Project Ltd.
| 06 08 2010 04:36:28 +0000
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While crystalline is based on OPC as raw materail, it rects with free lime in concrete to effectively function. But now a days PPC is widely used in construction, which has very minimal free lime. How does crystalline is effective there?
By
P V Raman, Director - Engineering,
| 08 22 2010 18:37:22 +0000
Now a days , mostly PPC is used for construction. Since crystalline reacts with free lime in cement, & there is very minimal free lime in PPC. How crystalline is effective in such cases?
By
P V Raman, Director - Engineering,
| 08 22 2010 18:32:53 +0000
True that crysttalline system is the best for U.G structures, but with some limitations. This system doesnot possess the crack bridging ability due to low elongation properties. As the concrete structures are known to develop some cracks in future due to subsoil conditions, sulphate actions & development of varied moments & differential movements in the structure.
By
P V Raman, Director - Engineering,
| 07 04 2010 12:57:01 +0000
Mr. Arun, while there is no doubt about crysttalline system being the best foe U.G structures, there is one limitation. this system doesnot not have the ability to bridge cracks developed at later stage, as concrete is highly likely to develop some cracks at later stages. p v raman, director- engineering, nucons infratech pvt td, kolkata
By
P V Raman, Director - Engineering,
| 07 04 2010 12:42:59 +0000
Mr. Boni, I totally agree with your view point. The solution can be provided as per the budget of the client. And no doubt HDPE and PVC are best membrane, and provide best services if precaution during application has been taken. As far as the project with crystalline are concern, its been used in many old structure as old as 70 years and has been used in new concrete as well. Shall forward you the list separately. You may visit www.xypex.com or www.xypex.com.au
By
Arun Rai, Head/VP/GM-Marketing, APAAR Infratech Pvt. Ltd.
| 06 10 2010 14:15:31 +0000
Arun, I understand we are discussing in-situ waterproofing solutions, so i wont discuss of waterproofing on precast segmental lined structures. There are range of waterproofing solutions for underground structures. Yes concrete additives like XYPEX do work in limited underground applications. As mentioned by Mr. Basab in his post, it depends on the type of the application. Durability of the structure ( life span) and hydrostatic head plays a part in the selection of the solution. Even with a good solution, a good dense concrete with low permeability is important. Generally following are used and found to be succesful for underground waterproofing: Bitumen membrane for depths of upto 3 meters below GL . Generally used to reduce ingress of moisture. Concrete additives, with provision for injection of resins, and waterstops/ hydrophilic strips at construction joints. Spray on Membrane . This membrane works but with limited applications on wet surfaces. PE & HDPE welded membranes placed behind concrete. This is one of the best solutions for deep underground waterproofing but precautions need to be taken when installed. Also when you plan waterproofing solution for an underground structure, dividing the structure in zones might be a good idea. So if you have failure in one zone, repair is limited to that zone. This is acheived by introducting external water stop compartments. At the end of the day, a good waterproofing solution depends on how much you are willing to spend. Hire a competent consultant, know what you want to achieve and avoid sale's pitch sales representatives.
By
P.P.Boni , McConnell Dowell ( Tunnel & Underground),
| 06 09 2010 22:17:43 +0000
Dear Mr. Ghosh, I appreciate your valuable feedback based on your very wide experience. But I would like to add that these crystalline product are not liquid based, its cement based material, when added in batch mix or applied as coating, it reacts with free lime, calcium chloride and un hydrated cement particles in presence of moisture to generate CSH gel, which eventually plugs the capillary tracts and pores of concrete. This dsent increase the volume of your concrete hence no cause of micro / macro cracking. This technology is 40 years old and widely used in most of the developed country. As far as the membranes are concern, they require dry surface for application, and its stops the breathing of the concrete which eventually determinates the life of structure. Pls share your email address, I will send few test reports and some case study for your reference.
By
Arun Rai, Head/VP/GM-Marketing, APAAR Infratech Pvt. Ltd.
| 06 08 2010 16:47:18 +0000
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