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International Concrete Abstracts Portal

Showing 1-5 of 179 Abstracts search results

Document: 

22-296

Date: 

January 1, 2024

Author(s):

Xiaoqin Li, Li Zhang, Wenlu Wen, Shihua Li, and Xu Zhou

Publication:

Materials Journal

Volume:

121

Issue:

1

Abstract:

Engineered cementitious composites (ECCs) have excellent toughness and crack-control abilities compared to other cement-based materials, which can be used in underground and hydraulic engineering. Nevertheless, excellent impermeability and workability and low drying shrinkage are also required. Two groups of ECC mixture proportions with high fly ash-cement (FA/c) and watercement ratios (w/c) were chosen as baselines, and silica fume (SF) and a shrinkage-reducing agent (SRA) were introduced to improve the impermeability, workability, and mechanical behaviors. The workability laboratory evaluation indexes of ECC were also discussed. ECC mixture proportions with excellent workability (pumpability and sprayability), high toughness (ultimate tensile strain ɛtp over 3.5%), good impermeability (permeability coefficient K = 1.713 × 10–11 m/s), and low drying shrinkage (drying shrinkage strain ɛst = 603.6 × 10–6) were finally obtained. Then, flexural and shear tests were carried out for the material flexural/ shear strength and toughness evaluations, giving the characteristic material properties for the final ECC mixture proportions.

DOI:

10.14359/51739200


Document: 

22-286

Date: 

December 12, 2023

Author(s):

K. Sriram Kompella, Andrea Marcucci, Francesco Lo Monte, Marinella Levi, Liberato Ferrara

Publication:

Materials Journal

Abstract:

The early age material parameters of 3D printable concrete defined under the umbrella of Printability, namely pumpability, extrudability, buildability, and the “printability window/open time” are subjective measures. The need to correlate and successively substitute these subjective measures with objective and accepted material properties such as tensile strength, shear strength, and compressive strength, is paramount. This study validates new testing methodologies to quantify the tensile and shear strengths of printable fiber-reinforced concretes still in their fresh state. A tailored mix, with high sulfo-aluminate cement and non-structural basalt fibers has been assumed as a reference. The relation between the above-mentioned parameters with rheological parameters such as yield strength obtained through ICAR rheometer tests is also explored. Furthermore, in an attempt to pave the way and contribute towards a better understanding of the mechanical properties of 3Dprinted concrete, as to be further transferred into design procedures, a comparative study analyzing the work of fracture per unit crack-width in 3-point bending has been performed on printed and companion nominally identical monolithically cast specimens, investigating the effects of printing directions, position in the printed circuit and specimen slenderness (length to depth) ratio.

DOI:

10.14359/51740302


Document: 

21-099

Date: 

September 1, 2022

Author(s):

Mohammed A. Abed, Mohammad Alrefai, Asaad Alali, Rita Nemes, and Sherif Yehia

Publication:

Materials Journal

Volume:

119

Issue:

5

Abstract:

Nominal maximum aggregate size (MAS) and particle distribution affect the performance of concrete significantly. However, their effect is influenced by the type of aggregate and the target concrete strength. This research investigates the effect of MAS on the mechanical performance of high-strength self-consolidating concrete (HSSCC). Two different types of coarse aggregates, natural quartz aggregate (NA) and recycled concrete aggregate (RA), were used in the evaluation. Compressive, splitting tensile, flexural, and shear strengths were tested and used as criteria for evaluation. Ultrasonic pulse velocity and rebound value were also used as nondestructive evaluation techniques. The results showed that compressive strength decreased when using a bigger MAS of NA, while it increased when using a bigger MAS of RA. However, this conclusion cannot be generalized to include all mechanical properties of concrete, as the failure mechanism for each test depends on the type and size of aggregate. In addition, finite and discrete element methods were applied to study the effect of MAS as well as to simulate the experimental performance of concrete. Following proper proportioning and mixing, RA could be used to produce HSSCC concrete.

DOI:

10.14359/51735948


Document: 

21-513

Date: 

September 1, 2022

Author(s):

P. V. P. Moorthi, Francesco Pra Mio, Prakash Nanthagopalan, and Liberato Ferrara

Publication:

Materials Journal

Volume:

119

Issue:

5

Abstract:

The stability and structural buildup of concrete can be evaluated by understanding the nature of the corresponding cementitious suspension using the small-amplitude oscillatory shear (SAOS) test through the time of percolation and rigidification rate, respectively. In the present study, four different cementitious suspensions—namely, 100% ordinary portland cement (OPC), OPC with 70% replacement of slag, OPC with 25% replacement of fly ash (FA), and OPC with 8% replacement of microsilica (MS)—were investigated. From the results, for OPC-based suspensions, the percolation time decreases for increasing dosages of high-range water reducing admixture (HRWRA) at low water-binder ratios (w/b) due to their high reactivity. In contrast, the suspensions with FA and MS exhibit a higher time for the formation of the elastic network, leading to a higher time of percolation. Further, it was identified that the suspensions with slag have the highest affinity toward the HRWRA, resulting in higher dispersion and therefore higher time required for the formation of the initial elastic network. This confirms that the dispersion and reactivity of the particles in suspensions dictate the stability and the structural buildup.

DOI:

10.14359/51735982


Document: 

21-331

Date: 

September 1, 2022

Author(s):

Vadim Potapov, Yuriy Efimenko, Roman Fediuk, and Denis Gorev

Publication:

Materials Journal

Volume:

119

Issue:

5

Abstract:

Cement concretes modified with hydrothermal nanosilica and basalt microfiber were developed. The compressive strength Fcom, flexural strength Fflex, and characteristics of impact viscosity were determined: the number of blows before the first fracture Nff and before ultimate failure Ncd, the coefficient Niv = Ncd/Nff, and the specific energy of impact destruction Eim/Sc. The strong effect of SiO2 action and synergistic effect of the combined action of nanoparticles and microfiber on Ncd and Eim/Sc was revealed. Statistical correlations with high R2 values were obtained between the characteristics of mechanical strength and impact viscosity at different doses of SiO2 nanoparticles. Correlations obtained can be used for reduction of the cross section of concrete structures and cement consumption. The mechanism of the strong synergistic effect of the combination is explained by the enlargement of the volume fraction of the high-density (HD) phase of calcium-silicate-hydrate (C-S-H) gel with more packed nanogranules and an increase in the shear stress of C-S-H gel relative to the lateral microfiber surfaces inside the HD-phase volume. The reduction of the coefficient of water filtration Kf and an increase in the frost resistance were achieved.

DOI:

10.14359/51735952


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