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Home > Publications > International Concrete Abstracts Portal
Showing 1-5 of 22 Abstracts search results
Document:
19-407
Date:
September 1, 2020
Author(s):
Adam M. Knaack and Yahya C. Kurama
Publication:
Structural Journal
Volume:
117
Issue:
5
Abstract:
This paper describes a numerical parametric investigation on the effects of coarse recycled concrete aggregates (RCAs) on the time-dependent sustained service-load deflections of reinforced concrete beams. The varied parameters are the volumetric replacement of coarse aggregate, concrete compressive strength, beam geometry (length, depth, width), rotational restraint at beam ends, top and bottom longitudinal steel areas, ultimate shrinkage strain, ultimate creep coefficient, and ambient relative humidity. In addition, RCA quality is quantified and varied through the water absorption and deleterious material content (for example, wood and asphalt). The beams were analyzed using a time-dependent concrete material model that can capture cracking, shrinkage, and creep behavior. The results show that the deflections of beams with good-quality RCA (with low water absorption and deleterious material content) are not much greater than those for beams with natural aggregate (NA). Importantly, RCA amount and quality have larger effects on the deflections of beams with less cracking (that is, shorter and/or deeper beams) and for beams with increased rotational restraint, for which allowable deflection limits would be less likely to govern design. There are significant differences between the ACI 318 time-dependent deflection factor and the numerical simulation results, with ACI 318 generally providing overly conservative estimates of the time-dependent factor, except for beams with minimal or no cracking. It is also found that RCA has a greater effect on the time-dependent deflections than on the initial deflection.
DOI:
10.14359/51725846
18-121
March 1, 2020
Magdalena Dobiszewska and Robert W. Barnes
Materials Journal
2
This paper describes a study of the use of waste basalt powder to enhance mortar properties when used as a partial replacement of fine aggregate. This basalt powder is a waste product resulting from the preparation of aggregates for asphalt mixture production. Experiments were performed on mixtures containing up to 20% replacement of sand by basalt powder to determine the impact on the compressive and flexural strength of mortar as well as on the flow characteristics, density, and porosity. The results indicate that use of basalt powder as a partial replacement of sand leads to improvement of the compressive strength and flexural strength. The mortar porosity in the capillary pore range was reduced. Use of the basalt powder can improve the management of industrial waste while improving the mechanical properties of cementitious mortar.
10.14359/51722392
19-161
Sarah Mariam Abraham and G. D. R. N. Ransinchung
A comprehensive analysis on the effect that fine fraction of reclaimed asphalt pavement (RAP) aggregates can produce on the fresh properties, strength, and durability characteristics of cementitious mixtures—that is, mortar and concrete—when used as partial or full replacement of natural fine aggregates (NA) is represented in this study. The replacements of NA were done by volume at 25, 50, 75, and 100% catering to the difference in specific gravity between the aggregates. The cement was also partially replaced by volume using silica fume and activated sugarcane bagasse ash (SCBA). To achieve this objective, effect of RAP aggregates was studied in both mortar and concrete. Although recycling is not a novel concept, altering the conventional mixture design and testing methodology whilst using RAP aggregates were looked into. The application of this study was focused upon rigid pavements, where flexural strength is of great importance. The mixtures considered did achieve the design flexural strength and protected the reinforcement from corrosion due to basic pH and absence of carbonation.
10.14359/51722398
15-190
July 1, 2017
Ziyad Majeed Abed and Abeer Abdulqader Salih
114
4
Roller-compacted concrete (RCC) is concrete that has no slump, no forms, no reinforcing steel, no finishing, and is wet enough to support compaction by vibratory rollers. Due to the effectiveness of curing on properties and durability, the essential aim of this research is to study the effect of various curing methods (air curing, 7 days of water curing, emulsified asphalt curing, and permanent water curing) and porcelanite (lightweight aggregate used as an internal curing agent) with different replacement percentages of fine aggregate (volumetric replacement) on RCC and to explore the possibility of introducing practical RCC for road pavement with a minimum requirement of curing. Specimens were sawed from slabs of 14.96 x 14.96 x 3.94 in. (380 x 380 x 100 mm). Results show that using 5% porcelanite improved RCC (with air curing) as compared to reference RCC (with permanent water curing) by percentages ranging from 0.4 to 1.7, 3.6 to 28.9, and 15.9 to –41.3% for bulk density, flexural strength, and water absorption, respectively
10.14359/51689775
14-180
November 1, 2015
Michael Berry, Bethany Kappes, and Lenci Kappes
112
6
This study was focused on evaluating the feasibility of using minimally processed reclaimed asphalt pavement (RAP) as aggregate replacement in concrete pavements. A statistical experimental design procedure (response surface methodology) was used to investigate the effects of key mixture parameters on concrete responses. The response surfaces generated from this analysis adequately characterized the behavior of these concrete mixtures, and were ultimately used to develop optimum mixtures to meet varying performance criteria. In laboratory tests, the optimum mixtures performed well and as predicted, thus validating the feasibility of using RAP in this application and this mixture design methodology.
10.14359/51687854
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