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International Concrete Abstracts Portal

Showing 1-5 of 272 Abstracts search results

Document: 

20-466

Date: 

September 1, 2021

Author(s):

R. Girardi, D. C. Dal Molin, F. A. P. Recena, and F. Tiecher

Publication:

Materials Journal

Volume:

118

Issue:

5

Abstract:

To dimension the structural systems of reinforced or prestressed concrete, it is necessary to know at least the elastic modulus and the compressive strength of the concrete. This is because several factors directly influence these two properties, from the dosage to the procedure adopted for curing the concrete. Therefore, this study aims to present the influence of two different types of curing (humid and thermal steam) over the elastic modulus of the concrete. The results demonstrate that a significant reduction occurs on the modulus when the concrete is submitted to thermal steam curing. Additionally, the increase in the volume of the paste in the mixture reduces the stiffness of the compound.

DOI:

10.14359/51732936


Document: 

20-376

Date: 

September 1, 2021

Author(s):

Karthik H. Obla and Colin L. Lobo

Publication:

Materials Journal

Volume:

118

Issue:

5

Abstract:

The resistivity of concrete is evolving as a reliable method to measure the penetrability of water and dissolved chemicals into concrete. In Part 1 of this two-part paper, the results of the bulk and surface resistivity of specimens conditioned by different methods were compared to the results of chloride ion penetrability by ASTM C1202, and the precision of test determinations was reported. In Part 2, the results illustrate how changing the specimen conditioning method can change how concrete mixtures are characterized for chloride ion penetrability or transport properties. For the different mixtures evaluated, specimens subjected to the same curing condition had different degrees of saturation levels at the end of the conditioning period. Correcting the measured resistivity for degree of saturation, however, led to inaccurate mixture classification. The paper recommends a preferred specimen conditioning method for the resistivity test.

DOI:

10.14359/51732935


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: 

20-375

Date: 

September 1, 2021

Author(s):

Karthik H. Obla and Colin L. Lobo

Publication:

Materials Journal

Volume:

118

Issue:

5

Abstract:

The resistivity of concrete is gaining acceptance as an easier and more reliable method to measure the penetrability of water and dissolved chemicals into concrete. This study evaluates the surface and bulk resistivity of concrete specimens prepared from mixtures with varying levels of penetrability or transport properties. Test specimens were conditioned by different methods as permitted by the standards. In Part 1, the results indicate that, based on measured resistivity, concrete mixtures are classified for transport properties similar to ASTM C1202. Resistivity measurements were less variable. Changes in the resistivity of specimens placed in simulated service conditions for 1 year are also evaluated. Comparisons were also made on resistivity measured on smaller specimens obtained from different locations of a cylindrical specimen. In Part 2, the impact of various specimen conditioning techniques allowed by the standards on the degree of saturation, resistivity, and characterization of concrete for transport properties are discussed.

DOI:

10.14359/51732934


Document: 

20-013

Date: 

May 1, 2021

Author(s):

H. N. Alnuaimi, S. Sasmal, U. Amjad, A. Nikvar-Hassani, L. Zhang, and T. Kundu

Publication:

Materials Journal

Volume:

118

Issue:

3

Abstract:

Cement paste is the primary constituent of concrete that keeps all other constituents together and gives concrete its strength. During curing, the cement is developed as a binder by going through various chemical reactions. In the present study, ultrasonic testing is carried out on concrete samples during curing in transmission mode. The acoustic signals are generated using lead zirconate titanate (PZT) transducers which are excited by a sweeping frequency signal. Nondestructive testing and evaluation were carried out at various stages of curing for concrete with two different watercement ratios (w/c). The obtained signals were processed to analyze the change in signal characteristics during the different stages of curing. It was found that the nonlinear ultrasonic technique called the side band peak count (SPC) index, which is derived from the frequency spectra, exhibits a clear distinction among various concrete specimens at different stages of curing. Linear ultrasonic parameters, however, do not show such consistency. Therefore, the nonlinear ultrasonic technique provides an easy and effective way for monitoring the degree of concrete curing.

DOI:

10.14359/51730412


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