Thin concrete overlay

[AU66ENG]

I have a 3 foot flat bottom width trapezoidal concrete ditch section that has standing water in it due to very flat longitudinal grade and poor initial construction. I am considering a thin concrete overlay sloped to one side of the section to achieve a transverse slope in addition to the flat longitudinal slope. The overlay would be aproximately 1 1/2" thick on one side and 3/4" thick on the other side. My thoughts are to pressure wash the existing section, apply some type of bonding agent, and place a fiber reinforced mix consisting of either coarse sand as the only aggregate or either sand and an aggregate not exceeding 1/4".

I would appreciate some help on (1) my approach, (2) type of bonding agent to use, (3) suggested mix design.

 

[dicksewerrat]

Will this send the water away? If you still have water after this, I wouldn't bother. Does this area freeze?

 

[AU66ENG]

I believe it will send water away except for small section formed by the transverse slope rather than flat bottom. Is in Florida and freezing is not a problem.

 

[KRSServices]

Is the standing water causing a problem, other than a being a breeding area for mosquitoes? If you are not shedding the water properly due to insufficient grades now, and will not be able to do so after the work is completed, what is the point? Other than aestetics, and the perception that something is being done, I would concentrate on removal of the water first and then worry about the cost of a suitable ditch lining option.

KRS Services

http://www.krs-services.com

 

[KBadger]

Regarding the concrete aspect of your repair: 1. Pressure washing is a good idea. I would recommend a pressure of approximately 4000 psi as you want to open up the existing concrete and create a rough profile on the surface. 2. If the contractor does a good job on the pressure wash I would recommend not using a bonding agent. Bonding agents can be difficult to apply and if environmental conditions are not right or the manufacturer's instructions are not followed then the bonding agent can decrease the bond strength between the existing and fresh concrete. 3. The repair area is very thin and you may have trouble finding a concrete with 1/4" aggregate. Consider using a topping product such as Burke Feather Patch (

http://www.burkebyedoco.com).

I have used this product as a topping on floor slabs and been impressed with its performance. Good luck!

 

[jgillikin]

Concrete surface preparation is the key to good bond strength (waterblasting or sandblasting). Concrete coring contractors have waterblasting robots that will do the job quickly. Also, bonding agents are very good if installed correctly. You must decide on the type of material you will use to overlay. Cementitous materials do have bonding agents which are epoxy modified and cementitous. Epoxy systems (100% solids) have moisture-tolerant epoxy primers that work very well. The overlay thickness will play an important role in material selection. Some materials do quite well in thin applications and terribly in thicker applications, and others vice-versa. My company has been doing concrete restoration for over 40 years and we have found that the Sika material products have been some of the best for these types of jobs. Also, other good material suppliers are Blome Cements and Henkel. Sika will offer a more braod range of materials involving epoxies, epoxy modified materials, and cementitous materials.