Common 3 problems that affect concrete - Concrete technology

There are some problems affect fresh concrete mix, what they are ? How to repair them ?
In this article I'm going to talk about these common problems : discoloration, scaling, and shrinkage.

1- discoloration :

When concrete is placed on one continuous pour all the concrete should have the same color, unless if you've added a high quality color pigment. This color change ( it could be dark or light color ) may be caused by :

•   Finishing concrete too soon or too late
•   Excessive, high troweling
•   Variation in the concrete placing or finishing operations  

How to prevent discoloration ?

• If calcium chloride is used as an accelerator and to increase the strength, it's better to use liquid calcium chloride not flaked because it's difficult to dissolve which may cause dark spots
• taking care about concrete finishing  

2- Scaling :

As the surface of concrete begins to peel away and flake, scaling area expands. It can be caused by water seeping into porous so non-air entrained concrete exposed into freezing and thawing circles.

You can prevent scaling by :

• Delaying finishing operations until the water is evaporated
• choose the proper mix design for exterior work. It should be low slump and air entrained 

3- Plastic shrinkage :

when water evaporates form the surface of the concrete at a high rate the plastic shrinkage occurs. We can't control humidity or temperature at the location, but shrinkage can be prevented by :

• Dampening subgrade and forms 
• Erecting windbreaks to reduce wind velocity 
• Minimizing placing and finishing time 
• Curing as soon as possible after finishing 
• Using membrane curing compound, curing paper, wet burlap, sand or other acceptable