On 16 August, work for the thorough renovation of the viaduct in Vilvoorde will begin. If you are coming from the direction of Ghent, you should expect long traffic jams.
The Vilvoorde viaduct, the busiest bridge in Belgium, opened for traffic in 1978. Now, around 150,000 vehicles cross the bridge every day. And that causes more wear and tear than the engineers at the time could have predicted.
After 45 years of increasingly intensive use, the bridge is in need of a large scale renovation.
Major disruption expected
A gigantic project that will take eight years in total and will cause major disruption on the Brussels Ring road. The work will be undertaken in stages. For each stage, one or more lanes will be closed to traffic.
Stage 1: August 2023 - end 2025
On 16 August, the first stage will begin on the inner ring. Specifically, the traffic heading towards Zaventem will have to make use of three narrowed lanes with a maximum speed limit of 50km/h. From February 2024, only 1 narrowed lane will be available during some weekend nights. 
You can find more information about the subsequent stages and the impact they will have here.
Consider using alternative transport
The works will cause major traffic jams in the direction of Zaventem. We would therefore strongly advise anyone coming from the direction of Ghent or from the region to the north of Brussels to leave the car at home and make use of public transport or the bicycle.
There are convenient train connections to Brussels Airport from Bruges, Ghent, Aalst and Denderleeuw. More info via https://www.belgiantrain.be/en.
For those coming from the region to the north of Brussels, the Ringtrambus (route 820) offers a very good alternative as well.
Or perhaps the bus could be a good option for you. Check it out with the De Lijn routeplanner.
And why not bike to the airport? Brussels Airport is easily accessible by bike thanks to cycle highways such as the F214 Vilvoorde-Brucargo. On fietssnelwegen.be you will find a handy route planner.