Concrete is probably the most widely used construction material in the world. In the
Arabian Gulf region, deterioration of concrete due to the aggressive environment is
recognized to be the main factor affecting their structural integrity. The durability of
concrete structures can be preserved by various protection methods; however, using
cement replacement materials is one of the most effective and economic methods of
maintaining their stability as well as extending their service life.
The aim of this project is to study four interrelated aspects, namely, (1) the effect
of hot environment on the properties of fresh concrete incorporating mineral
admixtures, (2), the influence of exposure environment on the engineering properties of
hardened concrete, under various curing conditions, without and with mineral
admixture, (3), the differences in porosity and pore structure of the same set of mixes,
and, (4) the effect of outdoor exposure on the durability-related properties of concrete.
To achieve the above aims, the experimental programme involved the study of five
different mixes of combinations of silica fume/slag and silica fume. The effects of real
exposure to the Arabian Gulf environment of these mixes subjected to four curing
regimes, namely, continuous water curing, no water curing after demolding, and air
drying after 3 and 7 days of initial water curing were investigated.
The properties investigated include (1) consistency and setting times of cement
pastes, workability and workability loss with time, (2) engineering properties such as
compressive strength, dynamic modulus of elasticity, pulse velocity, shrinkage,
expansion and thermal expansion, (3) microstructural properties such as porosity and
pore size distribution, (4) durability-related properties such as permeability, water
absorption and carbonation depth.
The results show that exposure to hot environment results in rapid setting times,
faster loss of slump, higher porosity, coarser pore structure and more permeable
concretes. It was found that part cement replacement by silica fume and slag improves the quality of concrete mixtures, refined the pore structure and produced concretes with
very low porosity and continuous pore diameter in both indoor and outdoor
environment. The properties of concrete containing mineral admixture appear to be
more sensitive to poor curing than the plain concrete, with the sensitivity increasing
with increasing amount of slag in the mixture.