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International Concrete Abstracts Portal

Showing 1-5 of 302 Abstracts search results

Document: 

SP-340-06

Date: 

April 1, 2020

Author(s):

Maria Kaszynska and Adam Zielinski

Publication:

Symposium Papers

Volume:

340

Abstract:

The research paper presents an analysis of autogenous shrinkage development in self-consolidating concrete (SCC). The first stage of the study involved an evaluation of concrete susceptibility to cracking caused by shrinkage of SCC with natural and lightweight aggregate. The shrinkage was tested on concrete rings according to ASTM C 1581/C 1581M- 09a. The influence of aggregate composition, the water content in lightweight aggregate, and SRA admixture on the reduction of concrete susceptibility to cracking, due to the early-age shrinkage deformation was determined. In the second stage of the research, the innovative method measurement of autogenous shrinkage was developed and implemented. The tests were performed on concrete block samples, dimensions 35x150x1150 mm, that had the same concrete volume as ring specimen in the ASTM method. Linear deformation of the concrete samples was measured in constant periods of 500 s using dial gauges with digital data loggers. The investigation allowed evaluating of the influence of water/cement (w/c) ratio of 0.28, 0.34, 0.42, and of aggregate composition on the development of autogenous shrinkage in different stages of curing SCC. The results were compared to existing material models proposed by other researchers. The conducted study indicated a significant influence of the w/c ratio and composition of aggregate on the concrete susceptibility to crack caused by the autogenous shrinkage deformation.


Document: 

SP-336_01

Date: 

December 11, 2019

Author(s):

James Lafikes, Rouzbeh Khajehdehi, Muzai Feng, Matthew O’Reilly, David Darwin

Publication:

Symposium Papers

Volume:

336

Abstract:

Supplementary cementitious materials (SCMs) in conjunction with pre-wetted fine lightweight aggregate to provide internal curing are being increasingly used to produce high performance, low-shrinking concrete to mitigate bridge deck cracking, providing more sustainable projects with a longer service life. Additionally, the SCMs aid in concrete sustainability by reducing the amount of cement needed in these projects. This study examines the density of cracks in bridge decks in Indiana and Utah that incorporated internal curing with various combinations of portland cement and SCMs, specifically, slag cement, Class C and Class F fly ash, and silica fume, in concrete mixtures with water-cementitious material ratios ranging from 0.39 to 0.44. When compared with crack densities in low-cracking high-performance concrete (LC-HPC) and control bridge decks in Kansas, concrete mixtures with a paste content higher than 27% exhibited more cracking, regardless of the use of internal curing or SCMs. Bridge decks with paste contents below 26% that incorporate internal curing and SCMs exhibited low cracking at early ages, although additional surveys will be needed before conclusions on long term behavior can be made.


Document: 

SP-334-04

Date: 

September 30, 2019

Author(s):

Alessandro P. Fantilli and Bernardino Chiaia

Publication:

Symposium Papers

Volume:

334

Abstract:

A detailed investigation on the use of automotive shredder residues, the so-called fluff, as an alternative aggregate of structural lightweight concrete, is the subject of the present paper. Specifically, a new granulated fluff, obtained through a granulation process already used to treat returned concrete, substitutes the traditional gravel made with expanded clay. Slump values are measured with the slump cone test on fresh concrete, whereas the depth of penetration of water under pressure, and the uniaxial compressive tests as well, are performed on hardened concrete cylinders. As a result, a new parameter, herein called “inconsistency parameter”, is introduced and used to define both the mechanical properties (i.e., the strength and ductility) and the workability of the lightweight concretes made with virgin or plastic waste aggregates. According to the required structural performances in service, the optimal value of the inconsistency parameter can be defined as a function of both the water/cement ratio and the content of the granulated fluff.


Document: 

SP-334-05

Date: 

September 30, 2019

Author(s):

Fariborz M Tehrani, John Carreon, and Nathan Miller

Publication:

Symposium Papers

Volume:

334

Abstract:

Detailed experimental and analytical studies were carried to investigate the effect of recycled tire-derived aggregates (TDA) on ductility and toughness of lightweight aggregate (LWA) concrete specimens containing coarse expanded shale aggregates and fine mineral aggregates. Investigations covered six different concrete mix with various portions of LWA replaced by TDA. Mechanical properties of each mix, including compressive strength, splitting tensile strength, flexural strength, and modulus of elasticity were measured to obtain the optimum range of TDA to LWA ratio. Further, dynamic destructive tests were carried to highlight the performance of tire-derived lightweight aggregate concrete (TDLWAC) subjected to impact loads. Moreover, the post-peak behavior of these specimens was modeled using a linear elastic fracture mechanics relationship. The model successfully demonstrated the effect of TDA in the enhancement of cracking behavior of TDLWAC.


Document: 

SP331-02

Date: 

February 1, 2019

Author(s):

Ian Shaw, Hang Zhao and Bassem Andrawes

Publication:

Symposium Papers

Volume:

331

Abstract:

Fiber reinforced polymer (FRP) composites have emerged as a lightweight and efficient repair and retrofit material for many concrete infrastructure applications. FRP can be applied to concrete using many techniques, but primarily as either externally bonded laminates or near-surface mounted bars or plates. This paper presents the results of direct shear pull-out tests performed on aged concrete specimens reinforced with glass FRP (GFRP) and carbon FRP (CFRP) externally bonded laminates and near surface mounted (NSM) bars. An accelerated aging scheme consisting of freeze/thaw cycling in the presence of a deicing salt solution is implemented to determine the effect of long-term environmental exposure on the FRP/concrete interface in regions that experience aggressive winter environments. The results show that the NSM bar technique is superior to externally bonded laminates in terms of efficiency in the use of FRP material and the effects of accelerated aging. Generally, the performance of GFRP is affected less than CFRP after freeze/thaw cycling for both externally bonded laminates and NSM bars. For high strength NSM FRP bar applications, a spalled or cracked concrete surface caused by freeze/thaw cycling may drastically reduce the capacity of the FRP/concrete interface by inducing failure at the concrete/epoxy filler interface.


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