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International Concrete Abstracts Portal

Showing 1-5 of 82 Abstracts search results

Document: 

19-324

Date: 

July 1, 2020

Author(s):

Dhanushika Gunatilake Mapa, Manjriker Gunaratne, Kyle A. Riding, and A. Zayed

Publication:

Materials Journal

Volume:

117

Issue:

4

Abstract:

Jointed plain concrete pavement (JPCP) repair slabs experience high incidences of early-age cracking due to high temperature rise and increased autogenous shrinkage of high-early-strength (HES) concrete mixtures. This paper presents an investigation to evaluate early-age cracking mitigation strategies of JPCP repair slabs. Finite element analyses were performed to understand the effects of physical phenomena leading to early-age cracking in JPCP repair slabs. While the analyses indicate the importance of concrete hydration kinetics and viscoelastic behavior on the early-age stress development in slabs, concrete moisture loss to the base was found to be the most significant phenomenon. Numerical modeling of concrete slabs was found to be useful in predicting the stress development in advance of costly field trials. Therefore, the proposed modeling approach can be applied to evaluate the performance of concrete mixtures prior to slab placement and thus improve and economize the current rigid pavement maintenance practices.

DOI:

10.14359/51725780


Document: 

17-462

Date: 

November 1, 2018

Author(s):

Daniel J. Pickel, Jeffrey S. West, and Abdulaziz Alaskar

Publication:

Materials Journal

Volume:

115

Issue:

6

Abstract:

An investigation was carried out on basalt fiber-reinforced concrete (BFRC) produced using various dosages of basalt fibers. The concrete mixture was designed with a target strength of 35 MPa (5075 psi), which is a typical strength for floor slabs and similar applications in which fiber reinforcement is often used. The concrete was tested for slump and air content in the fresh condition and for compressive strength, splitting tensile strength, flexural strength, and toughness in the hardened condition. Using these tests, the behavior of the BFRC was investigated and compared to fiber-reinforced concretes produced using similar dosages of polypropylene polyethylene synthetic fibers and crimped steel fibers. The basalt fibers were found to generally increase tensile and flexural strength (modulus of rupture), but were found to have very little effect on compressive strength and post-cracking behavior, and inspection found that the fibers had ruptured upon macrocracking.

DOI:

10.14359/51710958


Document: 

17-196

Date: 

September 1, 2018

Author(s):

D. G. Mapa, A. Markandeya, A. Sedaghat, N. Shanahan, H. DeFord, K. A. Riding, and A. Zayed

Publication:

Materials Journal

Volume:

115

Issue:

5

Abstract:

Jointed plain concrete pavement (JPCP) replacement slabs can experience early-age cracking from early-age volume change. These slabs are often made of high-early-strength (HES) concrete characterized by high cement content and low water-cement ratio (w/c), which can result in large temperature rise and high levels of autogenous shrinkage, and ultimately an elevated cracking potential. This study investigated the effects of reduced paste content and base restraint minimization on reducing concrete early-age cracking potential. The effect of each of these measures was evaluated in place by measuring the stress and temperature development in concrete test slabs instrumented with concrete stressmeters and thermocouples. Calorimetry studies and mechanical properties testing were used with modeling software to assess field trends. The findings indicated that it is possible to achieve higher strengths and lower stresses with low-paste mixtures. Changes in concrete stress during the first 24 hours after placement, due to moisture loss to the base, were seen in slabs with polyethylene sheet or geotextile fabric underneath the slab.

DOI:

10.14359/51702241


Document: 

17-232

Date: 

May 1, 2018

Author(s):

Shahab Samad, Attaullah Shah, and Mukesh C. Limbachiya

Publication:

Materials Journal

Volume:

115

Issue:

3

Abstract:

Limited research work exists on assessment of punching shear of reinforced concrete (RC) flat slabs made with blended cement incorporating ground-granulated blast-furnace slag (GGBS). This research is aimed at analyzing the punching shear strength of RC flat slabs cast from blended cement having GGBS in different proportions as partial replacement of cement. Four flat slabs supported on the ends were tested under column load such that one flat slab was cast from normal concrete with no GGBS and the remaining three flat slabs were cast with 30, 40, and 50% replacement of cement by GGBS. Experimental punching shear, midspan deflections, strain in the steel bars, and cracking pattern of the slabs were determined. The results of punching shear of flat slabs from the tests were compared with the nominal punching shear capacities proposed by BS 8110, BS EN1992-1-1/EC2, and ACI 318. The provisions of these building codes for the punching shear were observed as safe and conservative for the RC flat slab made from blended cement incorporating GGBS.

DOI:

10.14359/51702012


Document: 

15-280

Date: 

January 1, 2018

Author(s):

Hassan Parsian, Mohsen Tadayon, Davood Mostofinejad, and Farhad Avatefi

Publication:

Materials Journal

Volume:

115

Issue:

1

Abstract:

The current research goal is to develop appropriate relationships to predict results of resistivity measurements of the standard ASTM C1760 test method using test data from some other methods: impedance spectroscopy, and one-probe and four-probe methods. For this purpose, 49 concrete mixtures with a vast variety of resistivity were tested under similar conditions. The one-probe method test specimens were rectangular slabs with an edge of 300 mm (12 in.) and a height of 110 mm (4.5 in.), and the other test specimens were 100 mm (4 in.) diameter cylinders with a 200 mm (8 in.) height. The outcomes demonstrated little difference between the results of impedance spectroscopy, and one-probe and modified four-probe methods with ASTM C1760 methods. The cell constant of one-probe method, based on standard method results, has been included into the calculation in a special condition. Some relations were also derived to predict the standard method results using the other method’s results.

DOI:

10.14359/51701125


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