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|Title: ||Macro and microclimate effects on cover zone properties of field cured concrete|
|Authors: ||Al-Kindy, Adil|
|Issue Date: ||1998|
|Publisher: ||© Adil Al-Kindy|
|Abstract: ||Three sets of concrete blocks were cast to investigate the effects of natural
exposure conditions, at the macro and microclimate scale, and field curing on the
performance and durability of OPC and OPCjGGBS concretes. These are termed
the Loughborough winter series, the Loughborough summer series and the
Muscat summer series.
Three concrete mixes were investigated in the two Loughborough series (30 and
50 MPa OPC concrete mixes and a 30 MPa OPCjGGBS concrete mix) and two in
the Muscat weather series (the two 30 MPa concretes). A group of specimens
were cast with each mix consisting of 600 x 500 x 150mm concrete blocks plus
control cubes and prisms. The samples were cured in-situ and exposed to a range
of curing methods and microclimates.
Surface zone properties (up to 50mm depth) were evaluated by air permeability,
sorptivity, carbonation, thermogravimetry (TG) and mercury intrusion
porosimetry (MIP) tests, conducted after 3 and 12 months of site exposure.
The results revealed distinct variations due to macroclimate, microclimate,
curing, concrete type and age.
The air permeability, sorptivity and carbonation of the concrete exposed under
moderate and rainy conditions of a Loughborough summer season were lower
than identical concrete cast and cured during a very cold and dry Loughborough
winter season. Further, the sorptivity of concrete subjected to the hot and dry
climatic conditions of Muscat was significantly higher than companion samples
subjected to the temperate Loughborough climate.
Significant variations in properties were observed within the two sides of the
same concrete element, each subjected to a different microclimate.
The air permeability, sorptivity, carbonation and porosity were reduced with
increased hessian curing duration. However, premature drying of wet hessian
during curing had an adverse effect on concrete quality as this produced
concrete of higher permeability and carbonation than non-cured concrete. The
application of controlled permeability formwork was effective in improving the
concrete's sub-surface properties.
The curing affected zone (CAZ) extended to approximately 20mm below the
surface of the concrete that was exposed to the Loughborough winter and
summer climate, and 40-50mm for the concrete exposed to the Muscat climate,
with notable variation in properties due to climate and curing.
The TG and MlP results provided insights into the mechanisms associated with
the variations in the three concrete's properties due to natural field exposure.|
|Description: ||A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University|
|Appears in Collections:||PhD Theses (Architecture, Building and Civil Engineering)|
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