civil & structural engineering - Institution of Engineers Singapore

PROJECT APPLICATION
The two locks are currently being built, one on the Atlantic Ocean side and the other on the Pacifi c Ocean side.
ADMIXTURES FOR CONCRETE
Mapei admixtures were selected for all the concrete for the
structures, including the mass concrete for the external sides
of the concrete locks and the marine concrete for the internal
sides of the locks.
The latest generation of admixture technology will be used to
produce 5,500,000 m 3 of concrete required for this grand structure.
The aim is to ensure, through special tests on the concrete,
that the structure will last 100 years. The fi rst tests, carried out
at the GUPC consortium site laboratory, started in Panama in
September 2010.
Cement paste samples were tested to verify the compatibility
and to fi nd the best plasticising capacity of various samples of
admixture in combination with the types of cement scheduled
to be used on the structure (CEMEX cement, type II ASTM and
Panama cement, type II ASTM).
In the fi rst phase of testing, to overcome problems which
arise when using complex raw materials (basaltic aggregates
and basaltic pozzolan), several admixtures were evaluated. The
results showed that DYNAMON XP2, from Mapei, is the most
suitable admixture, for use with the materials that had actually
been chosen and which will be used in future on both the
Atlantic Ocean side, where they are using Panama cement, and
on the Pacifi c Ocean side, where they are using CEMEX cement.
This led to Mapei’s winning the short-term supply contract.
In early 2011, after starting production of the concrete and
aggregates, several serious problems such as considerable loss
of mechanical strength and durability in the concrete were
solved, thanks to the contribution of Mapei. In this phase, Mapei’s
support was concentrated on various activities - a study and new
chemical and mineralogical characterisation of the raw materials
used (fi ne sand, pozzolan and cement); technical suggestions
and advice to help make a correct choice of the fl occulating
and coagulating materials used to treat the water required for
cleaning the aggregates; and chemical and petrographic analysis
and control of the pozzolanic activity of the fi ne basalt sand to
reduce or optimise its content of natural pozzolan.
Following a request from the client, Mapei then started to
develop a new product which could work well with the new mix
designs being verifi ed at the GUPC laboratory. Mapei technicians
designed a new, highly-evolved admixture called DYNAMON
XP2 EVOLUTION 1, with the name chosen to give a sense of
continuity to the enormous amount of work previously carried out
on the old admixture. This product featured better maintenance
of workability and application properties, even in small dosages.
Mapei also contributed to renovation and consolidation work
on the Gatún Lock, located approximately 30 m below ground
and considered to be one of the most imposing reinforced
concrete structure ever constructed. This project uses a special
type of concrete and Mapei has supplied admixtures to make
it - PLANITOP 15, an inorganic powder product added to
the concrete cast into formwork, and the liquid admixture
MAPECURE SRA, specially formulated to reduce the formation
of cracks caused by hygrometric shrinkage in normal and selfcompacting
concrete.
Mapei’s fi nal contract in the new Panama Canal project was
signed on 21 December 2011. The company’s success in
winning the contract is the fruit of teamwork, the ability to
provide constant technical assistance to solve both large and
small problems, and the decisive support of the Mapei Research
& Development laboratories in fi nding the most advanced
technological solutions to make the best products.
36 THE SINGAPORE ENGINEER February 2013