Brighton's i360 - designed by the team behind the London Eye - will be 162 metres tall, with an observation pod at 138 metres.
Two hundred lorry loads of concrete are being driven to Brighton seafront at regular intervals for the work on Saturday.
The concrete will arrive one truck at a time "to minimise disruption".
Eleanor Harris, i360 CEO, said the progress was "exciting".
A steady flow of trucks, arriving every five minutes since the early hours of the morning, will bring 2,640 tonnes of concrete to the site.
Ruth Chapman, from the firm, said the trucks waited at a holding area in Shoreham to minimise disruption along the King's Road promenade.
The tower will be situated on the axis of the city's Grade II listed Regency Square.
Developers hope it will attract at least 700,000 visitors per year, which would make it the city's most popular paid-for attraction.
Construction will be completed this summer before the tower officially opens in mid-2016, they said.
Construction workers have begun to lay the foundations for England's tallest observation tower outside of London.