Driveway shade variation

We're buying a new home. The driveway was poured from two different trucks. Half of it has a grey tint, and the other half has a tan tint. The builder claims "normal shade variation," but ours is much worse than other homes in the neighborhood being built at the same time. How can I tell if the color variation is "normal"? Is there any other likely cause for the problem? Are there any potential fixes?

 

[emmgjld]

Fixing concrete coloring/shading is virtually impossible. Some of the shading differences may minimize after 2 to 4 years of exposure to sunlight and 'weathering' but, there is the possibility the shading may worsen, due to sunlight and 'weathering'. There are some methods of slightly 'bleaching' the slabs but the modified shading will probably change due to sunlight and 'weathering'. The final product may be worse than the original problem!

The cause of shading can range from changes in the concrete mix components and/or mix proportions or simply the time and method of finishing and curing. I have seen splotches or mottled shading due to plastic sheeting being placed on a newly finished surface due to the threat of rain.

Concrete placed during cold weather may develop various shades due to the method and amount of heat applied as part of the curing process. There are incorrect methods of heating which can result in surface distress (dusting, soft surface).

The best way to determine if the color shade variation is 'normal' is to visit around the neighborhoods and observe slabs which were placed during the same time frame and using the same concrete supplier as your slab.

I do not believe there is a good and simple answer to any of your questions. Sorry!

 

[dik]

Colour variation with different batches is common and not normally a concern, other than visual, as long as the material is within spec (strength, air, slump, etc.). If concerned about general quality, you can have someone use a 'Schmidt Hammer' or other impact tester to determine the 'strength' on the two parts to see if they are similar.

When architectual quality concrete is required for appearance, we often have samples cast and select a 'range' of colour, realizing that different 'colours' will occur.

 

[Ron]

My concern is that you mentioned one section has a "tan" color while the other has a "gray" color. The tan color concerns me. This is usually an indication of "oversanding" or too much sand in the mix (correspondingly, likely too little cement in the mix). This will lead to potentially poor durability for the long term.

As dik stated, you could have a Schmidt hammer test done for consistency, but be aware that ready mix suppliers routinely use the Schmidt hammer to their advantage. They will show that according to the hammer readings, the concrete has adequate strength for the application. The hammer readings can be very misleading and can lead to improper acceptance or rejection of the concrete. The definitive test, though destructive, is coring the concrete and having a proper compressive strength test run for those purposes.

Due to the poor control of residential concrete and the usual lack of specification clarity, it is likely that the contractor will only have to meet a minimal compressive strength requirement (by most US codes, 2500 psi). This makes the testing procedure important, since you likely did not contract for a specific color, finish, or result beyond the compressive strength.