الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Blended cement are made by the partial replacement of
ordinary Portland cement by siliceous materials such as silica
fume, blast furnace slag and CKD such blending materials
modify the strength, pore structure and permeability of the
hardened cement pastes. Sulphate attack on hardened cement
pastes causes a serious deterioration. The damage usually starts
at edges and followed by cracking of cubes. Magnesium
sulphate has a more damage effect than other sulphates because
it leads to the decomposition of the hydrated calcium silicate as
and hydrated calcium aluminates. Therefore, the aim of this
investigation is to study the physicochemical and mechanical
properties of some hardened blended cement pastes by
examining the hydration characteristics of various mixes as well
as magnesium sulphate attack. The effect of the additives such
as silica fume, blast furnace slag and CKD was examined.
Different mixes were prepared with various ratios of additives
and cured in water for various times (1-7-28-180-360 days) of
hydration. After 28 days half of the cubes are immersed in 5%
MgSO4 solution to investigate the physicochemical and
mechanical properties.
SUMMARY
401
The results obtained from the present investigation can be
summarized as following:-
- All the hardened cement pastes showed an increase in
chemically combined water content by increasing the
hydration age. This indicates that hydration reaction increase
with age of hydration.
- The hardened cement pastes blended with CKD, SF,
and slag showed an increase in compressive strength than the
net Portland cement (OPC) and it also depend on the ratio of
this additive.
-The increase in compressive strength is due to the
continues hydration reaction of anhydrated cement components
to form more hydration products in addition to the reaction of
SF, and slag with the liberated CH to form more CSH leading to
increase compressive strength.
- The X-ray diffraction patterns of some representative
hardened cement pastes cured in water and in magnesium
sulphate solution for various time intervals are studied.
SUMMARY
401
- The main hydration products formed by hydration of
cement paste (OPC) and blended cement pastes are calcium
silicate hydrates (CSH) and calcium hydroxide (CH) in addition
to the peaks characteristic of ettringite are seen in the hardened
cubes immersed in 5% MgSO4 solution.
The optimum amount of silica fume, slag and CKD that
give the improvement of hydration characteristics is 20 %
for SF, 25 % for slag, 5% CKD and 50 % OPC.
The highest compressive strength values are obtained with
mixes containing 30 % slag + 20 % silica fume + 40 %
OPC +10 % CKD and 25 % slag + 5 % CKD + 20 %
silica fume + 50 % OPC