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International Concrete Abstracts Portal

Showing 1-5 of 38 Abstracts search results

Document: 

22-424

Date: 

January 4, 2024

Author(s):

Chidchanok Pleesudjai, Devansh Patel, Kenneth A. Williams G., Mehdi Bakhshi, Verya Nasri, Barzin Mobasher

Publication:

Materials Journal

Abstract:

Statistical process control (SPC) procedures are proposed to improve the production efficiency of precast concrete tunnel segments. Quality control test results of more than 1000 ASTM C1609 beam specimens were analyzed. These specimens were collected over 18 months from the fiber-reinforced concrete (FRC) used for the production of precast tunnel segments of a major wastewater tunnel project in the Northeast, USA. The Anderson-Darling (AD) test for the overall distribution indicated that the data is best described by a normal distribution. The initial residual strength parameter for the FRC mixture, fD600, is the most representative parameter of the post-crack region. The lower 95% confidence interval (CI) values for 28-day flexural strength parameters of f1, fD600, and fD300 exceeded the design strengths, and hence validate the strength acceptability criteria set at 3.7 MPa (540 psi). A combination of Run Chart, exponential weighted moving average (EWMA), and cumulative sum (CUSUM) control charts successfully identified the out-of-control mean values of flexural strengths. These methods identify the periods corresponding to incapable manufacturing processes that should be investigated to move the processes back into control. This approach successfully identified the capable or incapable processes. The study also included the Bootstrap Method to analyze standard error in the test data and its reliability to determine the sample size.

DOI:

10.14359/51740373


Document: 

22-226

Date: 

May 1, 2023

Author(s):

Savitha Sagari Srinivasan and Raissa Douglas Ferron

Publication:

Materials Journal

Volume:

120

Issue:

3

Abstract:

Most concrete service life models are designed for uncrackedconditions, and the effect of microcracks on such models has not been as well researched. A service life model for concrete structures that takes into account microcracking is presented. A unique feature of this model is that its input parameters can be determined using only nondestructive methods, thus allowing it to be used when samples for laboratory tests cannot be extracted— for example, in in-service or critical infrastructure. The model was developed for low water-cementitious materials ratio (w/cm) concrete mixtures and validated on full-scale prestressed concrete girders. The results showed that the presence of a large number of microcracks could cause a loss in the remaining service life of concrete structures, even if individual microcracks did not cause asignificant impact.

DOI:

10.14359/51738686


Document: 

22-136

Date: 

May 1, 2023

Author(s):

D. F. Marbaniang, A. Kar, D. Adak, K. K. Ramagiri, D. Srinivas, and I. Ray

Publication:

Materials Journal

Volume:

120

Issue:

3

Abstract:

Thermal-cured alkali-activated binders (AABs) are a potential replacement for traditional portland cement (PC) in concrete, primarily for precast applications. To avoid this energy-intensive regime and encourage wider application, this study investigates the development of ambient-cured AABs by adding graphene oxide (GO) nanoparticles. The mechanical strength and durability characteristics are determined for alkali-activated slag (AAS) mortar specimens prepared using 4, 6, and 8 molar (4, 6, and 8 M) concentrations of sodium hydroxide in the alkaline activator. The different percentages of GO by weight of slag are 0.0, 0.03, 0.06, and 0.09%. The mechanical parameters considered are compressive, flexural, and splitting tensile strengths. The durability parameters investigated are the rapid chloride permeability test (RCPT), sorptivity, and acid resistance. The performance of ambient-cured AAS mortar specimens containing GO is compared with thermalcured AAS mortar specimens (without any GO inclusions) and the control cement mortar (PC) to evaluate the effect of GO on the mortar characteristics. The strength of AAS mortar is observed to be higher both with and without GO inclusions for the molarity of sodium hydroxide greater than 4 M. The mixture containing 0.06% GO with a 4 M activator is found to exhibit optimal mechanical and durability characteristics. Mineralogical, chemical, and microstructural investigations confirm that the addition of GO to the ambient-cured AAS accelerates the rate of hydration, even at a lower concentration of the activator (4 M) due to its high specific surface area and consequent formation of a greater number of nucleation sites. Hence, ambient-cured AAS mortar prepared using 4 M sodium hydroxide and 0.06% GO is recommended for practical use.

DOI:

10.14359/51738708


Document: 

21-466

Date: 

January 1, 2023

Author(s):

Xiaoguang Chen, Zeger Sierens, Elke Gruyaert, and Jiabin Li

Publication:

Materials Journal

Volume:

120

Issue:

1

Abstract:

Mixed recycled aggregate (MRA) is considered a sustainable construction material, and its use in precast concrete is currently banned due to its poor engineering performance. This paper aims to evaluate the feasibility of partial replacement of natural coarse aggregate with MRA in self-consolidating concrete (SCC) for manufacturing architectural precast concrete sandwich wall panels. To this end, five MRAs from recycling plants were characterized, out of which two were selected to develop SCC. SCC mixtures with three replacement levels and three water compensation degrees were produced, and their physical, mechanical, durability, and aesthetic properties were examined. The results showed that the incorporation of MRA dominated the mechanical properties of SCC, while the water compensation degree primarily affected the flowability and carbonation resistance. The presence of MRA had no considerable effect on the aesthetic characteristics. Up to 10% MRA in weight of total aggregates could be used in precast SCC.

DOI:

10.14359/51737333


Document: 

20-451

Date: 

November 1, 2021

Author(s):

D. Heras Murcia, M. Abdellatef, M. Genedy, and M. M. Reda Taha

Publication:

Materials Journal

Volume:

118

Issue:

6

Abstract:

Conventional cement-based concrete is widely used as a construction material due to its ability to flow before hardening and to adopt the shape of the formwork as it is placed. Contrarily, in layered extrusion additive manufacturing, commonly known as three-dimensional (3D) printing, concrete is shaped without formwork. This imposes stringent time-dependent rheological requirements of materials used for 3D printing. Polymer concrete (PC) is a material extensively used in the precast industry. This paper reports on the potential use of PC for 3D printing applications. The influence of mixture design parameters—specifically rheology modifier content, filler-polymer ratio, and aggregate-polymer ratio—on the rheological properties of a 3D-printable PC are investigated. The rheological properties of seven PC mixtures are tested and characterized. PC can be described as a Bingham pseudoplastic material, and a Herschel-Bulkley model can accurately describe its rheological behavior (dynamic shear stress) over time. The evolution of static yield stress over time was found to follow an exponential trend. The use of these models to predict the dynamic and static yield stress of PC shall enable the design of efficient and stable 3D printing. Finally, 3D-printed PC shows good mechanical performance with compressive strength above 30 MPa (4351 psi) at 7 days of age. Automation of the PC precast industry using 3D printing will create new opportunities for the use of PC in civil infrastructure.

DOI:

10.14359/51733123


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