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International Concrete Abstracts Portal

Showing 1-5 of 445 Abstracts search results

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-334-08

Date: 

September 30, 2019

Author(s):

Yasser Khodair, Arif Iqbal, and Mohammed Hussaini

Publication:

Symposium Papers

Volume:

334

Abstract:

This study discusses the results of an experimental program conducted to study the fresh, hardened and unrestrained shrinkage characteristics of self-consolidating concrete (SCC) using fine recycled asphalt pavement (FRAP) and high volume of supplementary cementitious materials (SCMs) including class C fly-ash (FA) and slag (S). Sixteen mixtures were prepared with different percentages of FA, S, and FRAP. SCC mixtures were divided into four groups where each group had a different percentage of FRAP replacing fine aggregate (10%, 20%, 30%, 40%) and Portland cement being replaced by different percentages of SCMs. The water to cementitious material (w/cm) ratio of 0.4 was used for SCC mixtures with a target slump flow higher than 500 mm. The flowability, deformability, filling capacity and resistance to segregation were measured to determine the fresh properties of the mixtures. Moreover, the compressive strength at 14, 28, and 90 days and split tensile strength at 28 days were determined and durability characteristics including unrestrained shrinkage up to 90 days were tested. Analysis of experimental data showed that most of the mixtures satisfied the SCC fresh properties requirements. The addition of FRAP had an adverse effect on the compressive, tensile strength and unrestrained free shrinkage of SCC mixtures.


Document: 

SP-334-11

Date: 

September 30, 2019

Author(s):

Eslam Y. Gomaa, Ahmed A. Gheni, and Mohamed A. ElGawady

Publication:

Symposium Papers

Volume:

334

Abstract:

The durability of alkali activated concrete (AAC) synthesized using high calcium fly ashes (FAs) was studied. Surface resistivity, bulk electrical resistivity, rapid chloride ions penetration, and freeze-thaw resistance tests were carried out on AAC made with five different FAs. The specimens were either oven-or moist-cured. The effect of adding air entraining admixture (AEA) and recycled crumb rubber to the AAC specimens on the freeze-thaw resistance was investigated as well. It was found that the durability of AAC was higher than that of comparable ordinary Portland cement (OPC) concrete. Adding the AEA improved the freeze-thaw resistance but not enough to complete the 300 cycles, per ASTM C666-15. Adding the rubber to the AAC mixtures improved the freeze-thaw resistance significantly.


Document: 

SP-330-05

Date: 

September 26, 2018

Author(s):

Chengning Wu and Junqing Xin

Publication:

Symposium Papers

Volume:

330

Abstract:

In order to improve compressive strength and the durability of concrete, such as, alkali-aggregate reaction resistance, chloride ion permeation resistance, carbonation resistance, and freezing and thawing resistance, a new type of combined cementitious materials was used to make the concrete. One part of the cementitious materials was high early strength Portland cement (similar to ASTM type III Portland cement), which had more than 63 mass% C3S and hydrated quickly to generate calcium hydroxide to accelerate pozzolanic reaction. Another part of the cementitious materials was fine blast furnace slag powders which had more than 6000 cm2/g Blaine specific surface area to get faster hydration with the calcium hydroxide. And other part of the cementitious materials was fly ash which had high specific surface area and low ignition loss to get faster pozzolanic reaction. According to the results of tests in this research, it is clear that the compressive strength of the concrete made with the combined cementitious materials is near that of the concrete made with the high early strength Portland cement only. However, the alkali-aggregate reaction in the concrete made with the combined cementitious materials is much lower than that of the concrete made with the high early Portland cement, and/or mixed with the fine blast furnace slag powders or fly ash respectively. It is also confirmed that chloride ion permeation resistance, carbonation resistance, and freezing and thawing resistance of the concrete made with the combined cementitious materials are improved considerably.


Document: 

SP-330-11

Date: 

September 26, 2018

Author(s):

HU Hong-mei, LUO De-fu, WAN Hui-bao, FU Rong-xing, and Cheng Yao

Publication:

Symposium Papers

Volume:

330

Abstract:

Three proportions of municipal solid waste incineration(MSWI) bottom ash (abbreviated as slag) mixed with sand were used as fine aggregate to make concretes with strength grades of C20, C30, C40, and C50.Workability and strength development were evaluated. Experimental results show that appropriate proportions of slag mixed sand could be used as fine aggregate in medium and low-strength concrete. The proportion of 5:5 slag mixed sand can be used to prepare concrete from grades C20 to C50; the proportion of 6:4 slag mixed sand can be used to prepare concrete from grades C20 to C40; and grades C20 and C30 concrete can be prepared by using the proportion of the 7:3 slag mixed sand. In the range of C20 to C50, the cost of the raw materials for concrete that is made using slag mixed sand is lower equal to the cost for concrete made with river sand. Thus, the former has economic and environmental advantages. It is concluded that the 5:5 slag mixed sand is the optimum proportion.


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