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International Concrete Abstracts Portal

Showing 1-5 of 583 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: 

SP326-108

Date: 

August 10, 2018

Author(s):

Francesco Bencardino and Mattia Nisticò

Publication:

Symposium Papers

Volume:

326

Abstract:

Composite materials that employ modified cement-based mortars are usually named Fabric-Reinforced Cementitious Matrix (FRCM). The two main components are the cementitious matrix and the reinforcement fabric. The matrix can contain silica fume, blast furnace slag, fly ash and in some cases chemical property that can act as corrosion inhibitor. Some types of fabrics commonly used for the strengthening of existing Reinforced Concrete (RC) structures include nets with carbon or polyparaphenylene benzobisoxazole fibers disposed along one or two orthogonal directions, and unidirectional steel ropes (S-FRCM).

The S-FRCM system can be applied according to the traditional Externally Bonded (EB) or the innovative Inhibiting-Repairing-Strengthening (IRS) technique. The latter is a sustainable strengthening method and it is a useful solution for existing RC structures with deteriorated or damaged cover concrete.

Experimental tests show that for S-FRCM systems, applied with EB or IRS technique, the debonding occurs at fiber-matrix interface without significant damage at concrete substrate. Consequently, the debonding strain depends mainly by geometric and mechanical properties of external reinforcement and elastic/fracture properties of fiber-matrix interface. Considering experimental data available in literature, related to RC beams strengthened in flexure using S-FRCM systems, a predictive strain debonding relationship is defined and its reliability is evaluated through comparison between experimental and theoretical ultimate load.


Document: 

SP326-08

Date: 

August 10, 2018

Author(s):

Ojedokun Olalekan and P.S. Mangat

Publication:

Symposium Papers

Volume:

326

Abstract:

An Investigation on the mineralogical and chemical characterization, pore structure, chemical shrinkage and pozzolanic activity of commercially produced rice husk ashes (RHA 1 and 2) and a control silica fume (SF) are presented in this paper. RHA possesses high silica content like silica fume which is used as supplementary cementitious materials (SCM) in the production of concrete. There is a need for an alternative to silica fume in the production of concrete because of its high demand and relatively high cost.

The mineralogical composition of RHA 1 and 2 show high silica content of 77% and 84% respectively which is close to the silica content (˃80%) of class 2 silica fume. The oxides of Ca are 3.53% and 7.68% while Al is 1.19% and 1.29% for RHA 1 and 2 respectively which suggest that RHA is a low Ca+2 content binder. The results of chemical shrinkage of RHA 1, 2 and SF are 0.42 mL/g, 0.52 mL/g and 0.11 mL/g after 500 hrs of hydration. This indicates that RHA 2 has the highest reactivity (hydration) with water due to its highest Ca+2 content.


Document: 

SP-320_09

Date: 

August 1, 2017

Author(s):

Gabriel Medina, José María Medina, Isabel F. Sáez del Bosque, Moisés Frías, María Isabel Sánchez de Rojas, César Medina

Publication:

Symposium Papers

Volume:

320

Abstract:

This study assesses the pozzolanic activity of two types of waste, one from biomass power plants and the other from the ornamental granite industry. These materials were first characterised chemically, physically, morphologically and mineralogically. Pozzolan reaction kinetics in the waste/portlandite system were then researched by analysing the crystalline compounds with instrumental techniques such as TGA and XRD. The findings showed that bioenergy plant waste exhibited pozzolanic activity comparable to the values reported for other agri-forest additions and greater than recorded for fly ash. Activity in the granite industry waste, in turn, was greater than in fly ash and lower than in silica fume and New Additions for the Design of Eco-Efficient Cements. Analysis of Pozzolanic Reaction Kinetics 9.3 sanitaryware waste. In light of these results, both types of waste would potentially be apt for use as additions in eco-friendly cements.


Document: 

SP-320_18

Date: 

August 1, 2017

Author(s):

Andrew Fahim, Edward G. Moffatt and Michael D.A. Thomas

Publication:

Symposium Papers

Volume:

320

Abstract:

This paper presents results obtained from steel-reinforced concrete specimens retrieved after 25 to 27 years of exposure in a marine environment. The specimens included mixtures with various SCM blends (25% fly ash, 10% silica fume and 50% slag), as well as a mixture without any SCM, all at a W/CM of 0.50. Testing included chloride-ion depth determination, rapid chloride permeability test, bulk electrical resistivity test and electrochemical corrosion-monitoring. The chloride profiles revealed that SCM incorporation leads to a significant decrease in chloride-ion penetration, which was supported by rapid chloride permeability and bulk electrical resistivity tests. Electrochemical corrosionmonitoring showed passivity for all reinforcements at a cover depth of 70 mm or more for specimens incorporating SCMs, while for specimens not containing SCMs, all reinforcements, up to a cover depth of 140 mm, showed active corrosion. Finally, it was found that the reinforcement corrosion rate in SCM concrete was significantly lower than that for portland cement concrete.


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