| Abstract | The longevity and durability of concrete remain a continuing
a rea of research activity a nd thought . The process of deterioration
of concrete is mediated largely by water . I n this research the
movement of water in the capi11ary pore s paces of concrete was
studied indifferent conditions .
In the present study key is the consideration of multi - phase
or Gas-Liquid movement, liquid phase movement is associated with
the gas phase.
Water plays a dual role in corrosion phenomenon. It acts as
the carrier medium for some elements of corrosion like Cl- in its
liquid phase , o n t he other ha nd it prevents the passage of other
elements like o2. For corrosion of steel lying just below t he cover
concrete , the alternate wetting a nd drying cycle is very dangerous
as he r e the ingress of elements of corrosion can take place . In
this study the movement of water in the wet tingcycle was
considered mainly in t he concrete of various mix proport ions. Here
water moves as a liquid in the capillary pore spaces of concrete,
driven by t he forces of surface tension, pressure gradient and is
resisted by t he friction between wat e r and concrete. The effect of
water/cement ratio , absorption pressure , length of specimen, curing
age , initial conditions , bleeding , and gravity on the water
movement was studied .
In the field structures, deterioration level s are different in
bridge deck like structures a nd column structures. I n this study,
for a l 1 the tests two boundary conditions A a nd B we reused,
simulating the field situation in above two types of structures.
Boundary conditions are related to the movement of the air phase.
In boundary condition A, since the top face is open so gas phase
movement is free, as water comes in t he capillary pore spaces air
escapes from t he top. In boundary condition B, since top face is
sea led so gas phase movement is stopped. As water movement occurs ,
space available to air reduces a nd a pressure 4 Pa is applied on t he
incoming water . Specimens with boundary condition A showed larger
moisture absorption than ones with boundary condition B. The effect
of boundary conditions is more prominent in longer specimens and in
specimens made with mortar concrete of larger W/C ratio .
General formulation for multi - phase water movement in concrete
is presented. A mode l is developed considering the equilibrium of
forces, for the liquid water movement drive n by surface tension and
pressure a nd resisted by the s hear friction be tween wat e r a nd
concrete . Results obtained from the mode l were compared with
experimental results a nd they s how very good agreement . |
