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International Concrete Abstracts Portal

Showing 1-5 of 903 Abstracts search results

Document: 

22-113

Date: 

November 10, 2022

Author(s):

Alaa M. Rashad, Youssef A. Mosleh, Mahmoud Gharieb

Publication:

Materials Journal

Abstract:

In spite of feldspars being the most torrential menial in the crust of the earth, their uses in alkali-activated materials are still too limited. In this work, for the first time, the effect of different ratios of potassium feldspar on the properties of alkali-activated slag (AAS) concrete was studied. The slag was partially replaced with 10 to 50% feldspar with a stride of 10 wt%. The effects of feldspar on the workability, compressive strength, splitting tensile strength, water absorption, and total porosity of AAS concrete were investigated. Different techniques were applied to investigate the crystalline phases, hydration products, and microstructures of the critical samples. The results showed a positive effect of feldspar on workability, of which the workability increased with increasing feldspar ratio. The incorporation of 10% feldspar has a positive effect on compressive strength, splitting tensile strength, water absorption, total porosity, and refining the microstructure, whilst higher ratios than 10% have a negative effect.

DOI:

10.14359/51737345


Document: 

21-458

Date: 

November 2, 2022

Author(s):

Duo Zhang and Victor C. Li

Publication:

Materials Journal

Abstract:

The built environment is facing an increasing challenge of emission reduction regarding both embodied and operational carbon. As an ultra-durable concrete, engineered cementitious composites (ECC) reduce the need for repair, thus resulting in a prominent reduction of lifecycle footprints. Here, a new version of low-carbon ECC was developed for cast-in-place applications by sequestering CO2 via mineralization. Two waste streams were pre-carbonated and incorporated into ECC as fine aggregate and supplementary cementitious material, respectively. At 28 d, the CO2-sequestered ECC exhibited a compressive strength of 32.2 MPa (4670 psi), a tensile strength of 3.5 MPa (508 psi), and a strain capacity of 2.9%. Multiple fine cracks were distinctly identified, with a residual crack width of 38 µm (0.0015 in.) and a self-healing behavior comparable to that of conventional ECC. The new ECC sequestered 97.7 kg/m3 (164.7 lb/yd3) CO2 (equivalent to 4.7 wt% of final mixture) and demonstrated a 42% reduction in cradle-to-gate emissions compared to conventional concrete at the same strength level. This study demonstrates the viability of turning waste CO2 gas into durable construction materials and proposes a potential path toward carbon neutrality.

DOI:

10.14359/51737331


Document: 

21-465

Date: 

November 2, 2022

Author(s):

Satoshi Fujimoto and Chiaki Kawamura

Publication:

Materials Journal

Abstract:

In cold weather concreting, materials and manufacturing facilities are generally heated to prevent concrete degradation. However, little attention has been paid to the environmental impacts of the heating process. Since heating inevitably requires energy input, the consequent carbon dioxide emissions should be considered. To characterize the regional and climatic factors influencing the environmental impact of concrete production, this paper analyzed heavy oil consumption for the production of ready-mixed concrete (RMC) in cold regions of Japan. Plant records were collected, and heavy oil consumption was monitored on-site. Using these records and monitoring data, the dominant factors of energy consumption were investigated, and a numerical model of heavy oil consumption for RMC production was developed. Model parameters were estimated based on monthly plant records. Heavy oil consumption and carbon dioxide emissions at the RMC production stage were quantified.

DOI:

10.14359/51737332


Document: 

22-116

Date: 

October 18, 2022

Author(s):

S.H. Chu

Publication:

Materials Journal

Abstract:

Concrete mixture design is the foundation of cement and concrete research. Innovations in concrete materials could, should, and would inevitably be incorporated into new mixture designs. Thus, a rigorous method for concrete mixture design can better bridge the research community and the construction industry with high reliability and high fidelity. However, current methods for concrete mixture design vary a lot in literature, thus compromising the accuracy and consistency in interpreting the properties of concrete subject to changes in its raw ingredients. Moreover, the extraneous variables in controlled experiments are not always controlled well. To solve this old but critical problem, this paper summarizes the prevalent concrete mixture design methods in literature and in practice. By contrast, the volume-based mixture design method is superior to the mass ratio-based mixture design method in terms of simplicity, accuracy, and consistency. Further discussion on packing density measurement and water or slurry film thickness (SFT) as a basis of volume-based mixture design is elaborated. Mathematically, the hardened properties were linked to the particle packing behavior and fresh properties of concrete. This research contributes to a unified volume-based design method to bridge the research community and the construction industry. In the end, it is conducive to upgrading from concrete technology to concrete science.

DOI:

10.14359/51737295


Document: 

21-480

Date: 

October 18, 2022

Author(s):

P. N. Ojha, Abhishek Singh, Brijesh Singh, Subhadra Sen, Ritesh Kumar, and Biswajit M. Patra

Publication:

Materials Journal

Abstract:

This study aims to investigate the possibility to utilize LD slag as one of the cementitious materials for the preparation of composite slag (having 8% and 15% LD slag) which will subsequently be used for manufacturing Portland slag cement (PSC). PSC samples (having overall 4% to 9% LD slag) were prepared using LD slag from two sources in a laboratory ball mill. PSC samples were analyzed for various chemical characteristics and physical properties. Studies were conducted on concrete mixes prepared at the water-to-cement ratio of 0.65 and 0.40. Fresh, hardened, and durability properties of concrete mixes prepared using PSCs made with composite slag having up to 15% LD slag, were found to be comparable to their corresponding control mixes. Based on the results, it was observed that composite slag having LD slag up to 15% of total slag can be used up to 60% for manufacturing PSC along with clinker and gypsum. The 3-, 7-, and 28-day compressive strength of PSC samples containing LD slags in different proportions, were found to be comparable to control PSC samples and meeting the IS 455:2015 requirements. Even though the free lime content in LD slags was significantly high (free lime content of 3.03% and 3.48%) in comparison to GBFS, it had an almost negligible effect on the PSC prepared using LD slag and soundness of experimental and control PSC was comparable because the maximum amount of LD slag added in overall PSC was restricted to 9%. The addition of LD slag in different proportions up to 9% in overall PSC does not seem to have any detrimental effect on the performance of concrete in terms of sorptivity, carbonation depth, chloride penetration, and diffusion, which indicates its suitability for application in reinforced concrete structures.

DOI:

10.14359/51737289


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