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Home > Publications > International Concrete Abstracts Portal
Showing 1-5 of 11 Abstracts search results
Document:
18-259
Date:
July 1, 2019
Author(s):
Kelly Costello, Sarah Mobley, Justin Bowen, and Gray Mullins
Publication:
Structural Journal
Volume:
116
Issue:
4
Abstract:
Drilling slurry made from a mixture of water and mineral or polymer powder is often used to stabilize deep excavations, in which cast-in-place reinforced concrete foundation elements such as drilled shafts are constructed. At the time of concreting, drilling slurry is displaced by heavier, highly fluid concrete tremie placed at the bottom of the excavation from within the reinforcement cage. Despite the fluidity of the concrete, it must build up within the reinforcing cage to a sufficient height before then radially pressing into the annular cover region. This flow pattern has been shown to trap slurry near the steel reinforcement and affect reinforcing bar bond. This paper presents the results of 227 reinforcing bar pullout tests performed over a 6-year period from 2012 to 2018. Shaft specimens were tremie placed in various slurry types and consistencies. This analysis concluded that present development length values should be increased by 1.8 for bentonite and 1.9 for polymer slurry; water casting environments showed no significant change relative to dry conditions.
DOI:
10.14359/51715570
109-M28
May 1, 2012
Habib Alehossein, Karsten Beckhaus, and Martin Larisch
Materials Journal
109
3
Tremie pipes are used to control concrete flow rate and minimize bleeding and dilution when placed into deep, submerged excavations. The L-box test is designed to measure workability and flowability of tremie pipe concrete as an indirect index measure of concrete viscosity and plastic yield. This test has been simulated by a mathematical model of the representative partial differential equation (PDE) derived for one-, two-, and three dimensional (1-D, 2-D, and 3-D) applications. The L-box model solves a dimensionless PDE in terms of the flow velocity along the L-box channel length as a function of time and distance, which is analogous to a nonhomogeneous heat conduction equation. An example problem for the 1-D application has been solved both numerically (by the finite difference method) and analytically (using Fourier analysis). The two methods and results are comparable and model the concrete flow behavior as observed in standard laboratory L-box tests.
10.14359/51683820
99-M50
September 1, 2002
M. Nehdi, Ashfaq Khan, and K. Y. Lo
99
5
With population growth and urban congestion, there is a growing need to use underground structures simply because available economical space is increasingly scarce at the surface. Underground structures and tunnels are employed in a growing range of applications encompassing transportation and storage facilities; military bases; hydroelectric, nuclear, and thermal generating stations; and processing and disposal facilities for radioactive and chemical waste. Many of these underground structures and tunnels, however, will have to be constructed in soft soil, rocks with time-dependent deformations, and other situations in which tunnel lining segments will be exposed to excessive deformations of the surrounding rock/soil that may lead to their failure. This study aims to develop a cost-effective grouting system that can serve as a deformable buffer layer between tunnel lining segments and the excavation line and therefore accommodate excessive rock/soil deformations. The effects of water-cement ratio (w/c), foam content, and sand addition on the mechanical properties of cellular grouts were studied using uniaxial and triaxial compression tests. Brittleness index and shear strength parameters of these grouts were also determined. The findings of this study suggest that low-density nonsanded cellular grouts have superior plastic behavior under triaxial states of stress and may be used to accommodate excessive deformations around tunnel linings, pipelines, and other buried infrastructure.
10.14359/12328
99-M14
March 1, 2002
Charles E. Pierce, Sarah L. Gassman, and Tracey M. Richards
2
Development of long-term compressive strength of controlled low-strength material (CLSM) was examined in a controlled experimental program. Strength development is important because minimal strengths must be met and maintained to provide adequate structural support, and maximum strengths must be limited to allow future excavation. Although strength gain with age is expected, strength loss has also been reported. This study evaluated the long-term strength development of CLSM subjected to the combined effects of prolonged mixing time and retempering, which are common concerns regarding field placement of ready-mixed CLSM. In addition, the impact of long-term exposure to a high moisture environment on strength development was investigated. The results of this study showed that limiting the mixing time of CLSM prior to placement and controlling the curing environment after placement appear to be the two most critical quality-control factors. Strength loss and softening were consistently observed for all CLSM specimens when measured after 600 days of immersion curing. It appears that long-term performance of CLSM is compromised when exposed to a saturated environment for long periods of time. Leaching of fly ash may contribute to this observation. Minimum required strengths of CLSM in high-moisture field conditions might not be maintained with time.
10.14359/11708
86-S12
January 1, 1989
ACI Committee 336
86
1
Covers requirements for drilled pier construction. It includes delivery, handling, and storage of the casing, excavation, soil testing, placing of concrete, and inspection.
10.14359/2697
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