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International Concrete Abstracts Portal

Showing 1-5 of 217 Abstracts search results

Document: 

22-066

Date: 

October 18, 2022

Author(s):

Adeyemi Adesina and Sreekanta Das

Publication:

Materials Journal

Abstract:

In this study, mineral admixtures were used to substitute a high volume of Portland cement (PC) in engineered cementitious composites (ECC), and the corresponding permeability properties and drying shrinkage were evaluated. Six ECC mixtures were made with high-volume mineral admixtures (i.e. MA to PC ratio of 5) alongside a control ECC mixture (i.e. MA to PC ratio of 2.2). The findings from this study revealed that the application of higher content of MAs ensued in a rise in the permeability of the ECCs at early ages. However, the permeability properties of the ECCs were significantly reduced in the long term resulting in similar or lower permeability compared to that of the ECCs made with a lower amount of MA (i.e. 2.2). The 28 days water absorption of ECC made with slag (BFS) as MA at a ratio of MA to PC of 5 is 5.4% while that of the control ECC with MA to PC ratio of 2.2 is 5.1%. The outcome of this research also revealed that the application of ground calcium carbonate (GCC) is beneficial in reducing the drying shrinkage of the ECCs. The drying shrinkage at 32 days of ECC made with GCC at a MA to PC ratio of 5 is 14.3% and 60% lower than when fly ash (FA) and BFS were used at the same MA to PC ratio (i.e. 5). However, GCC should be utilized in ECCs as a filler rather than a MA as there was a significant increase in the permeability of ECCs made with only GCC as the MA. Nonetheless, FA or BFS can be utilized alongside GCC to reduce the detrimental impact of GCC on the permeability characteristics of the ECCs.

DOI:

10.14359/51737292


Document: 

20-088

Date: 

October 18, 2022

Author(s):

Adeyemi Adesina and Sreekanta Das

Publication:

Materials Journal

Abstract:

This paper presents the results from the numerical and experimental evaluation of the effect of various parameters on the properties of basalt fiber-reinforced cementitious composites. The parameters considered in this study are the fly ash to Portland cement content, sand to binder ratio, water to binder ratio, and dosage of basalt fibers. The mixtures investigated were designed using the Taguchi method, and the corresponding compressive strength and permeability properties were investigated. Findings from this study showed that the use of basalt fiber at a dosage of 2% is optimum to achieve good strength and permeability properties. Optimized results also showed a good correlation with experimental results. The optimized composite with compressive strength, sorption, and porosity of 26.1 MPa, 0.4 mm and 4.81%, respectively, yielded experimentally a corresponding 24.6 MPa, 0.32 mm, and 4.03% for compressive strength, sorption, and porosity, respectively.

DOI:

10.14359/51737287


Document: 

21-389

Date: 

September 1, 2022

Author(s):

Yun Zhang, Meng Wang, Chen-Lu Fu, Yan-Hong Gao, and Yu-Rong Zhang

Publication:

Materials Journal

Volume:

119

Issue:

5

Abstract:

The stable time for concrete permeability is of great significance to evaluate the permeability of concrete and predict the service life of actual engineering. Based on a test with an exposure time of more than 3 years in a natural tidal environment, the gas permeability and microstructure parameters of concrete with different water-binder ratios (w/b) and admixtures including fly ash (FA), slag (SG), silica fume (SF), and basalt fiber (BF) were tracked and tested. Then, the time-dependent gas permeability and main microstructure parameters and their stable time were investigated. Finally, the relationship between stable time for the gas permeability coefficient and microstructure parameters was studied. The results show that the apparent and intrinsic gas permeability coefficients of concrete both decrease with exposure time. For ordinary concrete, the gas permeability coefficient and the corresponding stable time increase with w/b. The stable time for gas permeability coefficients of SF concrete is the shortest among admixture concrete, while that of BF concrete is the longest. The time dependent gas permeability is in keeping with the change of total porosity and contributive porosity of large capillary pores (100 to 1000 nm) with exposure time. Moreover, the change trends of stable time for gas permeability, total porosity, and contributive porosity of large capillary pores with w/b and admixture type are consistent. The stable time for the intrinsic gas permeability coefficient has a better correlation with that for contributive porosity of large capillary pores than that for total porosity. The intrinsic gas permeability coefficient stabilizes first, followed by contributive porosity of large capillary pores, which is the most important factor influencing the stable time for the intrinsic gas permeability coefficient, and total porosity stabilizes last.

DOI:

10.14359/51735956


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


Document: 

22-064

Date: 

August 29, 2022

Author(s):

Julia A. Bruce, Evan C. Bentz, Oh-Sung Kwon

Publication:

Materials Journal

Volume:

119

Issue:

6

Abstract:

This paper summarizes the results of a pilot experimental program intended to develop robust data for global airflow through cracked concrete, with comparisons against a traditionally used prediction method. Current models for predicting airflow through concrete based on Poiseuille flow poorly translate to large-scale specimens and real-world conditions without calibration. This paper presents a novel testing apparatus that will be used to identify key variables affecting flow rate and develop numerical prediction methods for industrial applications.

DOI:

10.14359/51737197


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