Geocell instead Geogrid to enhance the subgrade

One day, I received an inquiry from a customer who wanted to use Geogrid or Geocell to enhance their road subgrade. More details, please check below:

#Information from customer:

We are looking in to a project where a construction company has to ensure good quality subgrade (material from neighborhood is not A2-4 class, it is an A3 or A4 ) for a road project. Using either geocell or geogrid (as you propose or provide pricing for both options) and later use another product to enhance the quality of asphalt pavement using geogrid between binder and wearing asphalt courses.

Can you please provide indicative price CFR xxx for ( 200,000 m2) square meters of geogrid,
tensile strength 40 kn/m2 in each direction to reinforce the soil.

Also provide packaging details and technical data sheet.

#My answer:

Thanks for your below inquiry.

We only supply Geocell, so we can’t provide you with the proposal and prices for both options(Geocell and Geogrid).

Do you have more information regarding your project, like subgrade strength, vehicle type, loading capacity, traffic patterns, and type of infill material? If you can give us this information, we can recommend the suitable Geocell type and quote the exact Geocell price accordingly.

#Information from customer:

Dear Claire
The reply to our request was as follows:

•Our subgrade is usually a  material  of  “A4” AASHTO  classification, at times it is A3 but it is generally weak,
•Our vehicle type is usually heavy load trucks that are capable of transporting 120 ton loads.
•After reinforcing subgrade we intend to use A2-4  material as a subbase material 20 cm thick and then another layer of base coarse material 45 cm thick layer and then comes asphalt (binder layer 8 cm and then wearing layer of 6 cm thickness )

#My answer:

Dear Theodoros,

Thanks very much for your valuable information.
Please check my answers as follows:

1, Based on all your project information, Geocell 200-356(height 200mm, welding distance 356mm) should be the most suitable type. But please let me recheck with our engineer tomorrow, after getting his confirmation, then I will quote the price to you accordingly.

2, Attached our Geocell selection guide for your reference.

3, “After reinforcing subgrade, we intend to use A2-4  material as a subbase material 20 cm thick.” – Regarding this, in my opinion, you can use 20cm Geocell and infill the A2-A4 material as the subgrade directly. Geocell is 3-dimensional network, one of the advantages is that can use lower quality/cost infill materials, at the same time can reach good strength. Below is the equivalent table for your reference. For more details, you can check the Geocell design and installation guideline in attachment.

I will also check this question with our engineer tomorrow, and I will let you know the suggestions from our engineer accordingly.

#After checking with our engineer, please check my answers:

I discussed all your project information with our engineer. Please check our answers as follows:

1, Due to your existing subgrade is too weak, our engineer said he is afraid that the Geogrid can’t affect, because the Geogrid is only a two-dimensional structure, and can’t restrict the infill material. Geocell is a three-dimensional structure that can restrict the infill material well.

2, We want to know if your design “After reinforcing subgrade we intend to use A2-4  material as a subbase material 20 cm thick and then another layer of base coarse material 45 cm thick layer and then comes asphalt (binder layer 8 cm and then wearing layer of 6 cm thickness )” is based on only install 1 layer Geogrid to enhance the subgrade?

If your above design based on only install 1 layer Geogrid to enhance the subgrade, after changeing to use 200-356mm Geocell, you can reduce the total height of 40cm(20cm+20cm), the first 20cm is(we intend to use A2-4  material as a subbase material 20 cm thick), and the second 20cm is (then another layer of base coarse material 45 cm thick layer).

3, All the above recommendations are based on our full experience in the Geocell field, it is better to be calculated by a professional engineer to avoid any potential problem.

I will quote our Geocell HF200-356 price in the next email separately.
Thanks in advance : )

Any further questions, let Claire know freely. I’m the Geocell expert to answer any of your questions.

Based on my 15 years of experience in the Geocell field.