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Early-age concrete temperature and moisture relative to curing effectiveness and projected effects on selected aspects of slab behaviorYe, Dan 15 May 2009 (has links)
Concrete curing has long been realized to be important to produce durable concrete.
Curing compound is widely used to cure concrete in the field. The current curing
membrane evaluation method ASTM C 156, however, is incapable of distinguishing the
curing compound quality and guiding the curing practice in the field. A new laboratory
curing membrane evaluation protocol is developed in this study. It has the ability to rank
the quality of curing compound and guide curing practice in the field according to the
field ambient weather conditions and the type of curing compound. A series of field
tests were conducted to investigate the key factors that affect the curing effectiveness in
the field conditions.
A finite element program, temperature and moisture analysis for curing concrete
(TMAC2), is updated to solve the coupled and nonlinear heat transfer and moisture
transport problems in early-age concrete. Moisture capacity is induced into the TMAC2,
which makes it unique to characterize the self-desiccation. A full scale concrete
pavement test study was conducted at the FAA National Airport Pavement Test Facility
(NAPTF) near Atlantic City, New Jersey. In this study, the material properties, i.e.
thermal conductivity and moisture diffusivity, were backcalculated from field data.
Thereafter, backcalculated material properties were used to forward-calculate the
temperature and moisture histories of all other sections.
High order shear deformable theory is used to model the concrete slab curling
and warping behavior because of highly nonlinear temperature and moisture gradients.
The maximum shear strain is obtained a couple of inches below the concrete slab. This
might account for the occurrence of delamination.
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Distribution of stresses and displacements in skewed concrete slabsIsmail, Eman January 2017 (has links)
A 3D nonlinear finite element analysis was developed for simulating the behavior of skewed concrete slabs and to identify the response of the slab with different angles and element sizes. The purpose of this research is helping the engineering and construction industry to utilize the FEM study and results more in different structural applications.Simulations performed in ABAQUS for skewed slabs are also compared to straight and skewed slabs according to the analytical formulation by Timoshenko.The result showed that when the distance increases, the load capacity measured by reaction forces decreases for all different skew angles except angle 0° and 15° which show a stable reaction force along the entire path. .The study reveals that depending on the skew angle and the element size, the stress distribution and vertical displacements in the slab vary significantly from those in a straight slab. It is shown that the displacement decreases with the increase of the skew angle while the stresses increase with the decrease of the skew angle.There are small differences in the vertical displacements and stress distribution between the results obtained by this study and the results obtained by Timoshenko regarding the plates with skews of 0°, 30° and 45°.
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