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International Concrete Abstracts Portal

Showing 1-5 of 135 Abstracts search results

Document: 

19-355

Date: 

September 1, 2020

Author(s):

Diogo Henrique de Bem and Ronaldo A. Medeiros-Junior

Publication:

Materials Journal

Volume:

117

Issue:

5

Abstract:

No widely accepted method is available to assess the efflorescence in small-scale mortar specimens. Thus, the analysis and determination of parameters that actually have an influence on the occurrence of efflorescence in cementitious materials become difficult to be accomplished, especially considering that its appearance in natural field conditions can take months or even years to happen. This paper has the objective to compare eight small-scale accelerated test methods for the assessment of efflorescence in lime-cement mortars and then to evaluate their sensibility to variations in the mixture composition. The results show that the method in which a water column introduces pressure produced the highest amount of efflorescence in the smallest time. The method was able to clearly identify the impact of silica fume towards the refinement of the porous microstructure and the efflorescence reduction. This study demonstrates that 28 days is enough time to finalize the accelerated testing proposed.

DOI:

110.14359/51724627


Document: 

19-434

Date: 

September 1, 2020

Author(s):

T. Hemalatha, Arjun S, and B. S. Sindu

Publication:

Materials Journal

Volume:

117

Issue:

5

Abstract:

This study investigates the feasibility of using induction furnace slag as a substitute for river sand/manufactured sand (M-sand) in the production of concrete. The properties of concrete made with slag fine aggregate is compared with concrete made of river sand and M-sand. Experimental studies have been carried out on concretes made of three types of aggregates and two types of cement (ordinary portland cement [OPC] and portland pozzolana cement [PPC]). Mechanical and durability property tests performed according to standards showed that the characteristics obtained for the concrete made with slag aggregate is comparable with that of the concrete made with river sand and M-sand. This study suggests the 100% replacement of conventional fine aggregate with slag fine aggregate for the production of concrete without compromising the strength and durability characteristics. Further, the study demonstrates that with the suitable measures, the high water absorption of slag aggregate can be compensated.

DOI:

10.14359/51725981


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: 

18-284

Date: 

May 1, 2020

Author(s):

S. C. L. Lima, L. C. B. Costa, K. C. S. Defáveri, J. M. Franco de Carvalho, R. A. F. Peixoto, and G. J. Brigolini

Publication:

Materials Journal

Volume:

117

Issue:

3

Abstract:

The mining industry is responsible for various environmental problems, including the extraction of natural resources and the generation of a significant volume of waste. The use of such residues in the construction industry as supplementary cementitious material (SCM) is one possible solution to minimize its disposal and a way for both industries to improve their eco-efficiency. This research aims to study the pozzolanic potential of the residue generated in slate cutting, as well as to compare the current standard methods applied to verify the pozzolanic activity (strength activity index) and direct methods based on calcium hydroxide consumption. A milling study in a planetary ball mill was carried out to evaluate the effects of particle size distribution on reactivity. The pozzolanic activity was investigated based on current standard methods (strength activity index) and analytical evaluations. The results of calcium hydroxide consumption were obtained from simultaneous thermal analysis (thermogravimetric and thermal differential analysis) and X-ray diffraction. Conflicting results between the current standard and direct methods were observed. The tested specimens with low or inexpressive calcium hydroxide consumption presented a high-strength activity index, while the specimens that presented a higher calcium hydroxide consumption showed a strength activity index below the minimum values required by the current standards. The results pointed to the potential use of slate cutting waste and contributes to the discussions about the phenomena neglected by the current strength activity index standard.

DOI:

10.14359/51724611


Document: 

18-355

Date: 

November 1, 2019

Author(s):

Rafat Siddique, Malkit Singh, and Arpit Kumar Singhal

Publication:

Materials Journal

Volume:

116

Issue:

6

Abstract:

The use of unprocessed low-calcium wood ash as partial substitution of natural sand in manufacturing of concrete has been explored in the present study. X-ray diffraction (XRD) spectrum indicates the presence of amorphous as well as crystalline silica in unprocessed wood ash. The total composition of silica, alumina, and ferric of 92.93% qualifies the unprocessed wood ash to be used as pozzolanic material. Experimental tests were performed in laboratory for workability, strength, and durability properties of concrete incorporating 0, 5, 10, 15, and 20% wood ash as substitution of natural sand. It was observed that at a fixed water-cement ratio (w/c), the slump of concrete decreased on inclusion of unprocessed wood ash as partial substitution of natural sand. The compressive strength and splitting tensile strength of concrete mixtures made with unprocessed wood ash were lower than control concrete. The wood ash concrete mixtures, except the concrete mixture containing 5% unprocessed wood ash, displayed higher water absorption, sorptivity, and chloride-ion penetrability compared to control concrete. XRD analysis of powdered concrete specimens indicated no qualitative change in phase formation on incorporation of unprocessed wood ash.

DOI:

10.14359/51718052


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