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International Concrete Abstracts Portal

Showing 1-5 of 12 Abstracts search results

Document: 

SP219-07

Date: 

March 1, 2004

Author(s):

T. R. Naik, R. N. Kraus, Y. Chun, and R. Siddique

Publication:

Symposium Papers

Volume:

219

Abstract:

Three series of flowable slurry mixtures were made, each series with three different sources of wood ash (W-1, W-2, and W-3). The series of mixtures were: low-strength (0.3 to 0.7 MPa), medium-strength (0.7 to 3.5 MPa), and high-strength (3.5 to 8 MPa) mixtures. Tests were performed for flow, air content, unit weight, bleeding, settlement, compressive strength, and water permeability. Wood ashes W-1 and W-3 caused expansive reactions in CLSM mixtures resulting in little or slight (average 1%) net shrinkage of CLSM. Wood ash W-2 caused either significant net swelling (15% for Mixture 2-L, and 21% for Mixture 2-M) or no shrinkage (Mixture 2-H) of CLSM. The 91-day compressive strength of low-strength, medium-strength, and high-strength slurry mixtures was in the ranges of 0.38 to 0.97 MPa, 1.59 to 5.28 MPa, and 4.00 to 8.62 MPa, respectively. Overall, the slurry mixtures showed an average increase in strength of 150% (range: 25% to 450%) between the ages of 28 days and 91 days. This was attributed to pozzolanic and cementitious reactions of wood ash. In general, water permeability of CLSM mixtures decreased with age.

DOI:

10.14359/13141


Document: 

SP219-09

Date: 

March 1, 2004

Author(s):

C. Shi, Y. Wu, and C. Riefler

Publication:

Symposium Papers

Volume:

219

Abstract:

Crushed limestone dust is a waste material from the production of concrete aggregate by crushing quarried limestone rocks. The dust is usually less tan 1% of the aggregate production. Although it is coarser than common cementing materials such as as Portland cement, coal fly ash and ground blast furnace slag, it is fine enough to cause many problems during materials handling and disposal. Laboratory results have indicated that crushed limestone dust can be used to produce self-consolidating concrete (SCC) with properties similar to those of SCC containing coal fly ash. . Due to the differences in morphologies and particle size distribution, the mix design has to be modified when crushed stone dust instead of fly ash or ground blast furnace slag is used. Fresh SCC mixtures containing limestone dust loses its flowability and sets faster than the mixtures containing fly ash due to the acceleration of the hydration of Portland cement by the limestone powder. SCC containing limestone dust exhibited strengths similar to that containing fly ash during the first seven days, but the former exhibited lower strength than the latter at 28 and 90 days due to the contributions from the pozzolanic reactions between coal fly ash and lime released from the hydration of Portland cement. The former also have lower autogenous and drying shrinkages than the latter.

DOI:

10.14359/13143


Document: 

SP219-05

Date: 

March 1, 2004

Author(s):

H. C. Scott IV and D. L. Gress

Publication:

Symposium Papers

Volume:

219

Abstract:

This study investigated the reactivity of concrete containing recycled concrete aggregates (RCA) that had shown distress due to alkali silica reaction (ASR). The investigation evaluated several mitigation techniques to control ASR in concrete containing potentially reactive RCA. Mitigation work was done with three different aggregate types; an igneous fine-grained quartzite aggregate locally called blue rock, a non-reactive limestone, and RCA containing blue rock aggregate. These aggregates were used to investigate various mitigation techniques to prevent ASR from occurring in concrete containing RCA. The mitigation strategies include the use of class F fly ash, ground granulated blast furnace slag (GGBFS), lithium nitrate, silica fume blended cement and low alkali cement. These materials were incorporated into concrete mixes by cement substitution and direct application. These mitigation strategies showed potential in controlling ASR distress in RCA concrete. Mortar bars and concrete prisms were used to investigate the mitigation strategies by following standard and modified versions of ASTM C 1260 and ASTM C 1293 specifications to evaluate expansion caused by ASR. The modified versions of ASTM C 1260 were found effective in evaluating potential ASR expansion using conventional aggregates.

DOI:

10.14359/13139


Document: 

SP219-03

Date: 

March 1, 2004

Author(s):

T. C. Hansen and E. K. Lauritzen

Publication:

Symposium Papers

Volume:

219

Abstract:

The reduction and utilization of waste and by-products is one of many challenges facing mankind in the modern world. This paper consists of an overview of the handling of the world's concrete waste and is concerned with unbound applications of blended construction and demolition (C&D) rubble for pavement bases and sub-bases in road construction. The problems of recycling mixed wastes are considered and global perspectives are presented on the use of C&D rubble. The paper proposes that studies should be carried out in order to research the technical properties of blended C&D rubble, which the authors believe would be economically and environmentally justifiable in promoting the widest possible range of recycled products for road construction.

DOI:

10.14359/13137


Document: 

SP219-04

Date: 

March 1, 2004

Author(s):

J. S. Melton

Publication:

Symposium Papers

Volume:

219

Abstract:

Recycled concrete aggregate (RCA), when used appropriately, is an excellent substitute for natural aggregates in highway construction. RCA has been used successfully in unbound applications such as base course and fill, and in bound applications as aggregate in new concrete. However, a significant amount of concrete debris is still disposed of in landfills. Barriers to concrete recycling include regulatory and policy issues, economic disincentives, environmental concerns and technical questions. This paper reviews current obstacles to concrete recycling and discusses recent developments and research that will help overcome these barriers.

DOI:

10.14359/13138


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