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International Concrete Abstracts Portal

Showing 1-5 of 138 Abstracts search results

Document: 

20-400

Date: 

September 1, 2021

Author(s):

S. Gamze Erzengin and Gulce Senturk Guzey

Publication:

Materials Journal

Volume:

118

Issue:

5

Abstract:

Cross-linked polycarboxylates were synthesized and characterized with Fourier-transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), and thermogravimetric analysis (TGA). A comparative investigation of the mechanism behind the relationship between the molecular structure and performance (in terms of rheology, workability retention, and compressive strength) is the novelty of this research. Presence of cross-linkages in polymer structure provided high workability and workability retaining ability to cement pastes. A moderate cross-link density was determined as an important factor for cement dispersion (cross-link/side chain/main chain units molar ratios are 0.2/0.8/10). On the other hand, compressive strengths of designed concretes were significantly affected from the structure of superplasticizers— namely, highly cross-linked polymer provided better compressive strength (73.5 MPa and 72.5% strength increment to the basis of plain concrete). Finally, it was thought that cross-linked polycarboxylate-type superplasticizers could be the functional alternatives of their traditional counterparts, especially for the applications which required more workability and workability retention.

DOI:

10.14359/51732931


Document: 

20-509

Date: 

September 1, 2021

Author(s):

M. A. R. Manzano, Y. S. B. Fraga, E. F. da Silva, R. B. de Oliveira, B. Caicedo Hormaza, and R. D. Toledo Filho

Publication:

Materials Journal

Volume:

118

Issue:

5

Abstract:

This study investigates the influence of internal curing water on the compressive strength and microstructure of high-performance cementitious materials. For this, three high-performance fine-grained concrete (HPFC) and cement pastes were prepared. Two reference mixtures were investigated with total water-cement ratios (w/c) of 0.30 and 0.35. The third mixture was prepared with a basic w/c of 0.30 and the addition of 0.3% of superabsorbent polymer (SAP), resulting in a total w/c of 0.35. X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), and compressive strength tests were performed. The incorporation of SAP resulted in a refinement of the porous structure of the paste, despite increasing the total porosity. In addition, the paste containing 0.3% SAP resulted in an intermediate calcium hydroxide content compared with the reference pastes. Thus, it was concluded that SAP internal curing water participates in the hydration reactions of the cementitious material.

DOI:

10.14359/51732979


Document: 

20-317

Date: 

July 1, 2021

Author(s):

Ankur Bhogayata, Sneh Kakadiya, and Rinkesh Makwana

Publication:

Materials Journal

Volume:

118

Issue:

4

Abstract:

The paper discusses the development and application of the artificial neural network (ANN) model for predicting the compressive and splitting tensile strength of the geopolymer-based concrete composites (GPC). The strength properties of GPC are influenced by the proportions of the constituents—namely, the alkaline solution, fly ash, aggregates, and sand and water—and require optimization for the desired quality of the composite. The optimum mixture may be obtained by using modern techniques; namely ANN modeling. The ANN models have been developed by training and validating the input data using the sigmoid function and the feed-forward backpropagation algorithm in the hidden layers. The ANN layer is the functional part of the model consisting of the operators to carry out the specific task largely based on mathematical calculations. A five-layered ANN model has been developed and used to predict the strength to optimize the mixture design. The predicted values have been compared with the experimental strength values, and the effects of the most significant constituents have been studied.

DOI:

10.14359/51732711


Document: 

19-421

Date: 

May 1, 2021

Author(s):

Sary A. Malak, Neven Krstulovic-Opara, and Rawan Sarieldine

Publication:

Materials Journal

Volume:

118

Issue:

3

Abstract:

This paper presents the derivation as well as empirical verification of a compressive stress-strain model of concrete confined with fiber-reinforced concrete (FRC) jackets made using steel fibers. Both conventional (that is, strain-softening) FRC and high-performance (that is, strain-hardening) FRC (HPFRC) were considered. The model accounts for the tensile response of the jacket as a function of the fiber properties, fiber volume fraction, orientation, and the effects of fiber debonding, fiber pullout, and multiple cracking. Specific FRC and HPFRC materials used in this study include fiber-reinforced mortar (FRM), FRC, and slurry-infiltrated fiber-reinforced concrete (SIFCON), all made using steel fibers. Experimental behavior of model columns jacketed with FRC and HPFRC was compared to that of columns confined with conventional fiber-reinforced polymer (FRP) jackets. HPFRC jackets made with continuous aligned fibers exhibited fiber debonding and multiple cracking leading to the post-peak softening response. Varying the orientation of fibers in FRC and FRM jackets produces radial tensile stresses on the concrete core, thus reducing the strength of confined concrete. Concrete confined with FRC jackets exhibited post-peak softening response with lower ductilities than concrete confined with HPFRC jackets due to the random orientation and lower volume fraction of fibers within FRC jackets. HPFRC jackets with steel fibers are expected to sustain large rupture strains in the longitudinal and transverse directions, which translates into an improved ductility and energy absorption, making it a suitable retrofit option for existing columns.

DOI:

10.14359/51730419


Document: 

19-406

Date: 

March 1, 2021

Author(s):

Anvit Gadkar and Kolluru V. L. Subramaniam

Publication:

Materials Journal

Volume:

118

Issue:

2

Abstract:

Self-leveling concrete is developed with low-calcium alkali-activated fly ash (AAF) binder paste. The rheological behavior of AAF pastes with different compositions is evaluated. AAF pastes are proportioned with alkali-silicate activating solutions to ensure specific reactive oxide ratios for comparable geopolymer strength. The yield stress and the viscosity of the AAF binder paste vary with the silica content and the silica modulus (SiO2/Na2O mass ratio) in the alkali-silicate activating solution. The slump and flow behaviors of concrete mixtures made with AAF paste are evaluated. The requirements of the AAF binder characteristics, paste content, and aggregate packing for achieving self-leveling flow characteristics under gravity-induced flow are assessed. The transition from a frictional to a flow-type behavior in concrete mixtures depends on the AAF binder paste content. Self-leveling is achieved without the use of admixtures with an AAF binder paste of low yield stress and at a paste content of 45%. Improving the aggregate packing using the Fuller-Thompson curve and reducing the yield stress of the AAF binder paste increase the flow achieved in concrete mixtures. The specifications for cement-based self-consolidating concrete (SCC) are closely applicable for self-leveling AAF-based concrete.

DOI:

10.14359/51729324


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