ABOUT THE INTERNATIONAL CONCRETE ABSTRACTS PORTAL

  • The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.

International Concrete Abstracts Portal

Showing 1-5 of 175 Abstracts search results

Document: 

19-281

Date: 

July 1, 2020

Author(s):

Nader Ghafoori, Iani Batilov, and Meysam Najimi

Publication:

Materials Journal

Volume:

117

Issue:

4

Abstract:

The objective of this study was to evaluate the effectiveness of colloidal nanosilica (nS) as a nanomaterial and pozzolanic admixture to mitigate the deteriorative effects of sodium sulfate-based physical salt attack (PSA) on portland cement mortars. Mortar mixtures of an ASTM C150 Type II (<8% C3A) or a Type V (<5% C3A) portland cement were prepared with 0, 3, and 6% cement replacements with either nS or microsilica (mS). Test samples were subjected to 3 years of exposure under a constant or cyclic PSA-conducive environment. The PSA results were supported with additional water absorption, rapid sulfate ion permeability (RSPT), and porosimetry testing. The Type V cement mortars containing nS exhibited the most observable scaling and flaking under both conditions of PSA exposure. The addition and increase in cement replacement with nS had a clear detrimental effect to PSA resistance for both cement types and both types of PSA exposure. Results indicated nS reduces permeability and diffusion in mixtures of either cement type which, for PSA, the denser and more refined pore network proved conducive to higher damaging tensile stresses and distress. The larger the measured volume of permeable pore space through absorption, the less susceptible the mortars were to PSA, which is counterproductive to conventional good practice of designing high-durability concrete via reducing permeability and sorption, and increasing a mixture’s watertightness.

DOI:

10.14359/51725779


Document: 

19-205

Date: 

May 1, 2020

Author(s):

Rabab Allouzi, Aya Al Qatawna, and Toqa Al-Kasasbeh

Publication:

Materials Journal

Volume:

117

Issue:

3

Abstract:

Foamed concrete is currently studied to investigate its feasibility to be used structurally to produce a lightweight concrete mixture that is workable and has sufficient mechanical properties. This encouraged this research to design a foamed concrete mixture to be used in the construction industry. The main parameters that shall be satisfied for structural use are the workability, density less than 1900 kg/m3, and minimum cylinder compressive strength of 17 MPa (2500 ksi) based on ACI 213R. In this paper, 14 different foamed concrete mixtures are designed and tested to investigate their applicability. As fly ash quality affects foamed concrete permeability and as foamed concrete has low resistance to concentrated stresses, the proposed mixtures do not contain fly ash and are reinforced with polypropylene (PP) fibers. The effect of water-cement ratio (w/c), sand-cement ratio (s/c), PP fibers content, and the foam agent content are investigated. It is found that the compressive strength increases with the increase in density. The optimum s/c is 1:1, w/c is 0.4, and the PP fibers content is 1% by weight of cement. A relationship of splitting tensile strength relative to compressive strength is proposed.

DOI:

10.14359/51722405


Document: 

19-181

Date: 

March 1, 2020

Author(s):

Robert E. Melchers and Igor A. Chaves

Publication:

Materials Journal

Volume:

117

Issue:

2

Abstract:

This paper deals with long-term corrosion of steel reinforcement and how that is influenced by the presence of chlorides in the concrete. It provides experimental evidence that so-called “chloride-induced” long-term corrosion is the result of the accelerating effect of chlorides on the dissolution and loss of calcium hydroxide from concretes. This process progressively moves into the concrete, lowers its pH, increases its permeability, and facilitates inward diffusion of atmospheric oxygen. When these conditions reach the reinforcement, a high rate of reinforcement corrosion becomes thermodynamically possible and is observed in the experiments. It occurs earlier for concrete matrixes more open in structure. This can be attributed to greater internal surface area of exposed calcium hydroxide. The results also show that elevated concentrations of chlorides alone are not sufficient for causing long-term corrosion. The presented results throw a new light on chloride-induced corrosion under long-term exposures.

DOI:

10.14359/51722400


Document: 

18-474

Date: 

March 1, 2020

Author(s):

Boyu Wang and Rishi Gupta

Publication:

Materials Journal

Volume:

117

Issue:

2

Abstract:

In recent years, the construction industry has invested a lot of effort in increasing concrete safety and in extending the service life of structures. Several test methods such as water penetration, surface/ bulk electrical resistivity, rapid chloride permeability (RCP), and half-cell potential have been proposed to study concrete durability. This study establishes the relationship between multiple durability test methods in the context of concrete repair, which was rarely selected as the object for study. By means of experimental study, this study finds that surface resistivity has a linear relation to bulk resistivity and a polynomial relation to water permeability. No relationship can be established between concrete resistivity and compressive strength, though high-strength concrete tends to have a high resistivity. RCP test results do not correlate well with resistivity measurements, which requires further study to overcome its heating and binding effect when measurements are being taken.

DOI:

10.14359/51722396


Document: 

18-514

Date: 

November 1, 2019

Author(s):

Andrés A. Torres-Acosta, Francisco Presuel-Moreno, and Carmen Andrade

Publication:

Materials Journal

Volume:

116

Issue:

6

Abstract:

The potential use of the electrical resistivity (ρ) and the saturated electrical resistivity (ρS) for the durability design of new concrete structures and the forecasting for in-service concrete structures has been increasing in the past three decades. Many investigations have proven the ease of the method and the possibility of it being a quality control/assurance tool during construction of new concrete infrastructure. Some previous investigations even consider the ρS test a feasible one to remove other, more complicated and expensive tests used in cement-based materials as durability indicators; a few of them defined correlations between ρS and the other indexes. The present investigation uses published data to determine if empirical correlations exist between ρS and rapid chloride permeability (RCP), and between ρS and the apparent chloride diffusion coefficient (DAP). A literature search was done on the three durability indexes in question (ρS, RCP, and DAP) and some empirical equations were derived. Good empirical correlations were observed for ρS versus RCP and ρS versus DAP. The latter correlation, obtained from data of different sources, supported that ρS and chloride diffusivity follows the well-defined Einstein law of diffusion with minor modifications for cement-based materials.

DOI:

10.14359/51718057


12345...>>

Results Per Page 




Please enter this 5 digit unlock code on the web page.