Weeds through engineered pavement layers 1

[Mad Mike]

I have a bit of a novelty situation.

On one of my sites, pavement layers (crushed stone) were constructed for a new asphalt pour. The asphalt was delayed many months, and weeds have now cultivated on the upper crushed stone layer- see attached photograph.

Construction plant is no longer available on the site.

What is the best way of preparing my site for an asphalt pour? The only way I can think is to remove the weeds by hand, poison and then rip and re-compact the upper layer.

Any suggestions would be appreciated- I'm obviously looking for the most economic option and I don't think the weeds are dense enough to justify removing the upper layer.

Thanks in advance,
Mike

 

[EireChch]

I think what you propose is ok. Cant think of a better way. Although, do you need to rip and re-compact the upper layer. I doubt those weeds have big root systems and you probably pull 90% of the weed up by hand.

I would just roll the site again prior to asphalting

 

[Mad Mike]

EireChch,

Thanks for your input- that's exactly what I was hoping to hear, and agree, the rip and re-compact now seems excessive.

I'm wary as hell of trying to pull weeds from a dense pavement layer- I envisage almost all of the roots getting left behind, so I'm hoping to hear from someone who has actually tried this before (I can't be the only one???).

Maybe the weed roots have no effect on the final pavement performance (I don't know much about their root systems)- I don't want to be pedantic about it, but I also don't want an asphalt Contractor blaming my roots on his shoddy asphalt performance!

All the best,
Mike

 

[EireChch]

Personally I have not come across the issue, but we have compacted gravel as a backyard and I was always weeding it during the summer when I was a kid. But that just required pulling out of the big ones, the whole root system generally came up. I understand your concern though.

Maybe contact landscaper and get their opinion.

 

[Ron]

Check the root penetration depth. Probably only a couple of inches. Likely germinated from wind, not existing soil.
Then do as you proposed.

 

[Mad Mike]

Thanks very much EireChch / Ron- I was wary of posting this petty issue, until I suddenly realized I wasn't too sure about it.

Agree with the recommendations and will go ahead with it.

All the best,
Mike

 

[oldestguy]

Set a lawn mower for lowest setting, possibly even doing some change of wheel mounts or diameters, then with a leaf blower, blow the cuttings away. Then roto-til the top, roll and proceed with paving.

 

[Mad Mike]

Thanks OG- I will extend that practical tip to the Contractor...most of our guys have probably never even heard of a roto-tiller!

Mike

 

[MotorCity]

Remove the weeds by hand - seriously? Your client must have deep pockets. I would burn/torch the weeds so that they are reduced to ashes a day or two before the next phase of the project involving the upper layer. This has several advantages: does not disturb the top layer and no re-compacting (instead of roto tilling), is cost effective (instead of removing weeds by hand), does not contaminate the soil or lay down a chemical that adversely interact w/ whatever is placed on the upper layer (instead of weed killer)……………..or you could always bring in a herd of goats to eat the vegetation, not unheard of.

 

[Mad Mike]

MotorCity- thanks for your suggestion- torching them would never have occurred to me and sounds like a great idea...I'll have the guys bring out a flame-thrower!

I was far more worried about the roots that are left behind after cutting / torching- I doubt it would affect the asphalt performance, but I thought I'd better have at least the larger weeds hand-pulled to be sure of it (last thing I want is a mat of roots beneath the asphalt).

Lastly, I should have qualified that in South Africa, our daily labour rate is approximately $13, so it is still possible to do things by hand that might not be possible in first world countries...a herd of goats, now that sounds more like it!!!

All the best.
Mike

 

[msquared48]

They are probably GMO weeds that are compatible with the engineered pavement.

Mike McCann, PE, SE (WA, HI)

 

[geotechguy1]

Rabbits could work