الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 204 |  |  |
| | | from | 204 | | |
Abstract
Ultra-High Strength Self Compacting Concrete (UHSSCC) is in great demand for use in
construction mega projects around the globe, especially in high-rise buildings, marine
facilities, and long span bridges. Unless fillers are utilized in this concrete, its production
will come at an excessive environmental cost due to the high Carbon footprint of Portland
cement.
The present work aims to develop UHSSCC from locally available inert and active fine
powders (cement, silica fume (SF), Metakaolin (MK) and limestone (LS) and quartz
powder (QP). Mechanical properties (compressive, splitting and flexural strength) and
fresh characteristics such as flowability, passing ability and segregation resistance have
been verified using slump flow, L-box and V-funnel. Ultrasonic pulse velocity and
microstructure analysis were also investigated. In this study ternary and quaternary mortar
mixes were designed and produced, satisfying the European SCC Guidelines 2005, with
compressive strengths exceeding 115 MPa. SF and MK were used as a pozzolanic active
material with 22% replacement ratio, QP was used as a filler material by 26%
replacement from sand. In addition to two types of fiber were used (steel, polypropylene
and basalt fiber) by 160, 1.8 and 8.1 kg/m3
with ratio (2%, 0.2%, and 0.3%) respectively
as reinforcing materials.
The impact of elevated temperature on behavior of developed UHSSCC were
investigated. Concrete mixes contained SF, MK, and LS as partial Portland cement
replacement and QP as partial sand replacement. Basalt Fibers (BF) were added to
reinforce the matrix. Compressive and tensile strength of the mixes along with UPV,
sorptivity, absorption and SEM Micro-structure features were studied at ambient
temperature and after the samples were exposed to either 200 or 300 oC; since the
behaviour of UHSSC at elevated temperature is always a cause for concern.
Finally, the behavior of nine Reinforced Concrete (RC) columns made of UHSSCC of the
same geometry and reinforcement but with different BF contents (0.0%, 0.3% and 0.6%)
when subjected to different elevated temperatures (25 oC, 300 oC, and 600 oC) were
experimentally and numerically studied under axial compression. Based on degree of the elevated temperature, the columns have been categorized into three groups, each of them
has three columns, and each column contains UHSSCC with different BF content. The
columns were axially loaded up to failure after exposure to the specified temperature.
Theoretically, numerical models constructed using Finite Element (FE) software;
ANSYS, have been used to simulate the behavior of the tested columns. The results
indicated that: -
SCC mixes, with compressive strengths exceeding 115 MPa, were produced. Amongst
these mixes, two quaternary blends containing 15% SF, 5% MK, 20% LS as partial
Portland cement replacements, with or without partial replacement sand with QP,
achieved a compressive strength > 125 MPa, a level of strength not cited for quaternary
SCC in published literature. All fillers, both active and inert, co-operated to realize this
level of strength.
The inclusion of 20% LS improved both the fresh and mechanical properties of
UHSFRSCC at all temperature conditions. Generally, columns made of UHSSCC
containing basalt fibers had ultimate load carrying capacities higher than those of normal
reinforced UHSSCC without fibers.
For axially loaded columns, adding 0.3% basalt fiber was enough to obtain the highest
values of ultimate load, ultimate lateral deformation, energy absorption, and, in turn,
ductility.
The constructed numerical models showed responsible accuracy in predicting the
ultimate load carrying capacity and the ultimate lateral deformation of the tested columns.
This makes the followed modeling process leads to reliable results.
Keywords, ultra-high strength self-compacting concrete, Microstructure, Mass transport
properties, elevated temperature, axial compression, R.C column, Basalt fibers, steel
fibers and polypropylene fibers.