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International Concrete Abstracts Portal

Showing 1-5 of 33 Abstracts search results

Document: 

19-232

Date: 

May 1, 2020

Author(s):

Mohamed M. Sadek, Mohamed K. Ismail, and Assem A. A. Hassan

Publication:

Materials Journal

Volume:

117

Issue:

3

Abstract:

This study aimed to optimize the use of fine and coarse expanded slate lightweight aggregates in developing successful semi-lightweight self-consolidating concrete (SLWSCC) mixtures with densities ranging from 1850 to 2000 kg/m3 (115.5 to 124.9 lb/ft3) and strength of at least 50 MPa (7.25 ksi). All SLWSCC mixtures were developed by replacing either the fine or coarse normal-weight aggregates with expanded slate aggregates. Two additional normal-weight self-consolidating concrete mixtures were developed for comparison. The results indicated that due to the challenge in achieving acceptable self-consolidation, a minimum binder content of at least 500 kg/m3 (31.2 lb/ft3) and a minimum water-binder ratio (w/b) of 0.4 were required to develop successful SLWSCC with expanded slate. The use of metakaolin and fly ash were also found to be necessary to develop successful mixtures with optimized strength, flowability, and stability. The results also showed that SLWSCC mixtures made with expanded slate fine aggregate required more high-range water-reducing admixture than mixtures made with expanded slate coarse aggregate. However, at a given density, mixtures developed with expanded slate fine aggregate generally exhibited better fresh properties in terms of flowability and passing ability, as well as higher strength compared to mixtures developed with expanded slate coarse aggregate.

DOI:

10.14359/51722407


Document: 

18-006

Date: 

January 1, 2019

Author(s):

Mohamed K. Ismail, Assem A. A. Hassan, and Mohamed Lachemi

Publication:

Materials Journal

Volume:

116

Issue:

1

Abstract:

This investigation aims to study the abrasion resistance of developed self-consolidating engineered cementitious composite (SCECC) mixtures using the rotating-cutter and sandblasting abrasion tests. The fresh and mechanical properties of the developed SCECC were also investigated in this study. Additional conventional self-consolidating concrete (SCC) (with 10 mm [0.39 in.] coarse aggregate) and vibrated engineered cementitious composite (VECC) mixtures were tested for comparison. The standard engineered cementitious composites (ECCs) are commonly developed using a high volume of fly ash (FA) and microsilica sand (SS). In this study, the FA was partially replaced by varied volumes of slag (SL), silica fume (SF), and metakaolin (MK), while the SS was replaced by crushed granite sand (CS) of different sizes. The results indicated that combining SL, SF, or MK with FA resulted in developing SCECCs with adequate deformability and higher abrasion resistance, compressive strength, and flexural strength. Using 20% of MK in the development of SCECC showed the best abrasion resistance improvement in both rotating-cutter and sandblasting tests. The results of rotating-cutter and sandblasting tests also indicated that SCECC mixtures appeared to have less abrasion resistance compared to their SCC counterpart mixtures with 10 mm (0.39 in.) coarse aggregate.

DOI:

10.14359/51712239


Document: 

16-100

Date: 

September 1, 2017

Author(s):

L. A. Sbia, A. Peyvandi, I. Harsini, J. Lu, S. Ul Abideen, R. R. Weerasiri, A. M. Balachandra, and P. Soroushian

Publication:

Materials Journal

Volume:

114

Issue:

5

Abstract:

A pilot-scale field investigation was conducted through which: 1) a refined ultra-high-performance concrete (UHPC) mixture was prepared in a ready mixed concrete plant; 2) a large reinforced UHPC block was constructed through placement, consolidation, and finishing of UHPC; and 3) a commonly available concrete curing (insulating) blanket was applied for field thermal curing of the UHPC block using the exothermic heat of hydration of the cementitious binder in UHPC. Monitoring of the reinforced UHPC block temperature over time confirmed the development of a reasonably uniform temperature and a viable temperature time history, which suited thermal curing of UHPC without any heat input. In-place nondestructive inspection of the reinforced UHPC structure pointed at timely setting and strength development, leading to achievement of ultra-high-performance status. Specimens were cored from the large reinforced concrete block and subjected to laboratory testing. The experimental results indicated that the field thermal curing was more effective than the laboratory thermal curing considered in the project, and that the pilot-scale production of the UHPC mixture produced compressive strengths approaching 170 MPa (24.7 ksi).

DOI:

10.14359/51689677


Document: 

16-276

Date: 

May 1, 2017

Author(s):

Wael A. Megid and Kamal H. Khayat

Publication:

Materials Journal

Volume:

114

Issue:

3

Abstract:

Multilayer casting of self-consolidating concrete (SCC) can be critical in situations involving casting of successive lifts. The increase in structural buildup at rest of freshly cast SCC material prior to the placement of a successive layer can result in lift lines and loss in interlayer bond strength. Delay in the casting of successive lifts without mechanical consolidation can further reduce bond. Eight SCC mixtures designed to develop different levels of structural buildup at rest were investigated. The structural buildup at rest was determined by multiplying the values of initial slump flow, T50, or J-ring flow by average rates of change in these properties with rest time. Bond between successive layers was determined using composite specimens cast with two lifts of SCC after rest periods of 17 to 52 minutes, which corresponds to 25 to 60 minutes of concrete age. Bond strength was determined using the slant shear and direct shear test setups. Compared to monolithically cast samples, composite specimens had residual bond strengths of 15 to 100%. The critical delay time to secure at least a 90% residual bond strength was found to vary between 5 and 55 minutes, depending on the structural buildup at rest of the concrete in the existing layer. Statistical models for predicting residual bond strength between successive lifts were established and account for the structural buildup at rest of the first lift and delay period between successive lifts. Based on the level of structural buildup at rest, three categories of SCC are proposed. Category III SCC with relatively low structural buildup at rest can develop high residual interlayer bond. Such concrete should have maximum slump flow filling ability index of 800 mm.mm/min (31.5 in.in./min), T50 viscosity index of 0.08 sec.sec/min, and J-ring passing ability index of 600 mm.mm/min (23.6 in.in./min).

DOI:

10.14359/51689597


Document: 

15-449

Date: 

January 1, 2017

Author(s):

Gail M. Moruza and H. Celik Ozyildirim

Publication:

Materials Journal

Volume:

114

Issue:

1

Abstract:

The Virginia Department of Transportation (VDOT) incorporates innovative materials into its concrete structures to ensure durable and cost-effective infrastructure. However, poor consolidation can reduce the durability of VDOT concrete structures because it leads to unacceptable amounts of voids in hardened concrete that increase its permeability and reduces its strength. Self-consolidating concrete (SCC) that has high flow rates and the ability to move through congested reinforcement is a new addition to VDOT concretes; it facilitates placement, minimizes consolidation problems, and improves structure longevity. This paper summarizes VDOT’s use of SCC in bridge structures both in precast and castin-place applications. In precast applications, beams were fabricated with normalweight and lightweight SCC. In cast-in-place applications, drilled shafts, pier caps, and substructure repairs were cast with normalweight SCC. Summaries of field applications by VDOT as well as lessons learned through implementation are included in the paper.

DOI:

10.14359/51689480


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