| dc.description.abstract | A study of the effects of aggressive solutions
on mortar cubes made from Kenya~ cements and sands
has been conducted. The study is important because
failure of concrete structures exposed to rain water,
domestic and industrial effluents is increasing.
Ordinary portland cement; sulphate resisting
portland cement; and pozzolanic cement were used to
make 70.7 mm cubes with British Standard sand and
suitable sand samples from Kajiado and Machakos
districts. The cubes were imme~sed in: deionised
water; waste water from a facto~y; two concentration
solutions of fluoride, ch~oride and sulphate
prepared from the respective aci~s. The effect of
the soluLions on the cubes for a .eriod of six
months was monitored by measuring volume changes
and compressive strengths of t~e cubes; pH, anionic
and cationic concentrations of Lhe solutions. The
results for the cubes made with the standard sand
were use~ to assess the perfo~~ance of the cements.
The performance of the sands was assessed by holding
the different cements constant i~ the tests.
Ka-j iado sand has been fOI....d.:t.o be more coarse
and to contain more silt than ~~e ~achakos one.
Machakos sand, on the other hand, has been found to
be richer in mineral content. Quartz has been
found to form the bulk of the two sands. Machakos
sand has been found to form unworkable mixes with
cements when using a W/C ratio of 0.4, and to bulk
when using a W/C of 0.5. The waste water from the
factory has been found to contain the following
levels of anions: sJlphates 361.8-2566.5 ppm;
chloride 298.2-1498.8 ppm; fluoride 5.5-38.9 ppm;
and phosphate 0.306-1.224 ppm.
The solutions have been found to affect the
cubes differently. In environments rich in sulphate
ions but combined with other ions, like iGdustrial
effluents, sulphate resisting portland cement should
be used only after 2 careful study. The reactions
of the cubes with The fiuoride solutions have been
found to be less deleterious than with the other ions
investigated and in some cases fluoride ions were
beneficial. The c~~ent-sand combinaTions That ~ere
found to have TJerfY--med-...Jeilnl the d i f f er-e rrt
environments are: | en |
