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International Concrete Abstracts Portal

Showing 1-5 of 322 Abstracts search results

Document: 

22-076

Date: 

April 1, 2024

Author(s):

Kavya Vallurupalli, Nicolas Ali Libre, and Kamal H. Khayat

Publication:

Materials Journal

Volume:

121

Issue:

2

Abstract:

Successful implementation of extrusion-based three-dimensional (3-D) printing requires the development of print materials with adapted rheology. In this study, filtration characteristics coupled with rheological properties of mortar mixtures are investigated to characterize the extrudability of print materials and establish a “printability window” (that is, the acceptable range of material properties for successful extrusion and shape stability). The extrudability was measured as the maximum force needed for the ram extrusion of the material. The fluid filtration rate was assessed in terms of desorptivity of the fresh mixture under pressure. The yield stress, plastic viscosity, and desorptivity were varied by changing the water-cement ratio (w/c), high-range water-reducing admixture (HRWRA) dosage, and welan gum (WG) content. Regression analysis indicated that during extrusion-based printing, the yield stress and desorptivity values can exhibit a more significant effect on extrudability than plastic viscosity.

DOI:

10.14359/51740301


Document: 

23-055

Date: 

February 8, 2024

Author(s):

Sangyoung Han, Thanachart Subgranon, Hung-Wen Chung, Kukjoo Kim, Mang Tia

Publication:

Materials Journal

Abstract:

A compressive laboratory testing program, field testing program, numerical analysis, and life-cycle cost analysis were conducted to evaluate the beneficial effects of incorporating shrinkage-reducing admixture (SRA), polymeric microfibers (PMF), and optimized aggregate gradation (OAG) into an internally cured concrete (ICC) mix for rigid pavement application. Results from the laboratory program indicate that all ICC mixes outperformed the standard concrete (SC) mix. All ICC mixes showed a decrease in drying shrinkage compared to the SC mix. Based on the laboratory program, three ICC mixes and one of the SC mixes were selected for the full-scale test subjected to a heavy vehicle simulator for accelerated fatigue testing. Extensive testing and analysis have shown that ICC mixes incorporating SRA, PMF, and OAG can be beneficially used in pavement applications to achieve increased pavement life.

DOI:

10.14359/51740564


Document: 

23-101

Date: 

February 8, 2024

Author(s):

Le Teng, Alfred Addai-Nimoh, Kamal H. Khayat

Publication:

Materials Journal

Abstract:

This study evaluates the potential to use shrinkage-reducing admixture (SRA) and pre-saturated lightweight sand (LWS) to shorten the external moist curing requirement of ultra-high-performance concrete (UHPC), which is critical in some applications where continuous moist curing is challenging. Key characteristics of UHPC prepared with and without SRA and LWS and under 3 days, 7 days, and continuous moist curing were investigated. Results indicate that the combined incorporation of 1% SRA and 17% LWS can shorten the required moist curing duration since such mixture under 3 days of moist curing exhibited low total shrinkage of 360 µε at 56 days and compressive strength of 135 MPa (19,580 psi) at 56 days and flexural strength of 18 MPa (2,610 psi) at 28 days. This mixture subjected to 3 days of moist curing also had a similar hydration degree and 25% lower capillary porosity in paste compared to the Reference UHPC prepared without any SRA and LWS and under continuous moist curing. The incorporation of 17% LWS promoted cement hydration and silica fume pozzolanic reaction to a degree similar to extending the moist curing duration from 3 to 28 days and offsetting the impact of SRA on reducing cement hydration. The lower capillary porosity in the paste compensated for the porosity induced by porous LWS to secure an acceptable level of total porosity of UHPC.

DOI:

10.14359/51740566


Document: 

22-388

Date: 

December 1, 2023

Author(s):

R. M. Ghantous, V. Bui, S. Schaef, B. Fronczek, C. B. Jablonski, S. R. Reese, and W. J. Weiss

Publication:

Materials Journal

Volume:

120

Issue:

6

Abstract:

This study uses neutron radiography (NR) and visual inspection to quantify water penetration in concrete samples exposed to water pressure on one face. It provides experimental data regarding the impact of mixture proportions on the hydraulic permeability of concrete. Specifically, it illustrates the influence of water-cement ratio (w/c), curing duration, entrained air content, and coarse aggregate (CA) size and volume on water transport. In addition, this paper quantifies the impact of permeability-reducing admixtures (PRAs) on water transport in concrete. It was observed that decreasing the w/c and/or increasing the curing duration reduced the fluid transport. Liquid and powder PRAs efficiently reduced fluid transport in concrete without impacting the compressive strength. The liquid PRA showed more consistent results, likely due to better dispersion than the powder PRA. Fluid ingress in concrete samples appears to increase with entrained air content due to a lower degree of saturation (DOS) at the start of the test. Increasing the CA volume fraction or decreasing the CA size will increase the fluid transport in concrete due to an increase in the connectivity of the interfacial transition zone. The influence of entrained air content, curing duration, CA volume fraction, and CA size was less noticeable on mixtures with PRAs due to the higher density and low permeability of these samples compared to control samples.

DOI:

10.14359/51739150


Document: 

22-221

Date: 

September 1, 2023

Author(s):

C. F. Hollmann, L. Zucchetti, D. C. C. Dal Molin, and A. B. Masuero

Publication:

Materials Journal

Volume:

120

Issue:

5

Abstract:

Self-healing is a process by which concrete is able to recover its properties after the appearance of cracks, which can improve mechanical properties and durability and reduce the permeability of concrete. Self-healing materials can be incorporated into concrete to contribute to crack closure. This study aims to evaluate the influence of crystalline admixtures and silica fume on the self-healing of concrete cracks. The rapid chloride penetration test was performed on cracked and uncracked samples, from which it was possible to estimate the service life of concretes. The concretes were characterized by tests of compressive strength and water absorption by capillarity. The use of crystalline admixtures did not have a negative influence on concrete properties, but did not favor the chloride penetration resistance. The concrete with silica fume showed the lowest charge passed and highest values of estimated service life.

DOI:

10.14359/51738892


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