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|Title: ||Wet-process sprayed mortar and concrete for repair|
|Authors: ||Goodier, Chris I.|
|Issue Date: ||2000|
|Publisher: ||© Christopher Ian Goodier|
|Abstract: ||The primary aim of this research was to improve the understanding of the influence of
the process and the mix constituents on the fresh and hardened properties of wetprocess
sprayed mortars and concretes. The main objectives were: to improve the wetmix
spraying process; to specify, measure and optimise in-situ properties; and to
disseminate the information obtained in appropriate form to practising engineers to
accelerate the use of wet-process sprayed mortar and concrete for repair.
The research focused on three types of repair mortars/concretes: pre-blended
proprietary mortars (<3 mm aggregate), designed laboratory/site batched mortars and
fine concretes (<8 mm aggregate). Thirty mixes were pumped and sprayed using
seven pumping/spraying systems. Nineteen types of test were conducted to measure
the fresh and hardened properties using three types of specimen production (cast
mould, sprayed mould and in-situ specimen). Ten repair scenarios generally
encountered in the UK were identified and classified in terms of their characteristics
and relevant mixes were identified to satisfy these differing requirements.
A rheological audit has been developed and a variety of tests were used to characterise
the pumpability and sprayability of each mix, including: rotational viscometers
(Tattersall two-point test and Viskomat), pressure-bleed, shear vane, slump, build,
fresh density, output, stream velocity (using high-speed video), reinforcement
encasement and core grading. A new approach that defines the build in terms of the
maximum shear and tensile bending stresses generated at failure was also developed.
Hardened properties measured include: compressive and flexural strength, tensile
bond strength, drying and restrained shrinkage, elastic modulus, air permeability,
sorptivity and hardened density. The hardened performance was generally higher
when sprayed with the wet process compared with hand application and lower when
compared with the dry process (which was expected), although the values obtained
were more than sufficient for normal repair work. All the pre-blended mortars could be pumped and sprayed with a small worm pump.
Twelve laboratory-designed mortars were pumped and sprayed in a dedicated spraying
chamber constructed at Loughborough and the best of these performed as well as, and
produced hardened properties that equalled or surpassed, the pre-blended materials.
For worm pumping the grading of a mortar was found to be important and a suitable
combined material grading zone has been determined.
Two pre-blended and a laboratory-designed mortar were sprayed with a piston pump
as were the nine designed concrete mixes, the former producing similar in-situ
properties to worm pumping. One pre-blended mix was sprayed successfully with five
different wet-process pumps (four worm plus one piston) and three pre-blended
mortars and one designed fine concrete were sprayed by the dry-process to benchmark
performance, along with data from three repair contracts. The hardened property
measurements obtained from spraying directly into steel moulds with a low-volume
worm pump were consistent enough to have applications for quality control.
The research demonstrated that low-volume wet spraying is a healthier, cleaner and
more controllable process (compared with the dry process) which can produce
consistently high quality mortars and fine concretes suitable for a range of
applications in the UK.|
|Description: ||A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.|
|Appears in Collections:||PhD Theses (Civil and Building Engineering)|
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