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International Concrete Abstracts Portal

Showing 1-5 of 52 Abstracts search results

Document: 

19-232

Date: 

May 1, 2020

Author(s):

Mohamed M. Sadek, Mohamed K. Ismail, and Assem A. A. Hassan

Publication:

Materials Journal

Volume:

117

Issue:

3

Abstract:

This study aimed to optimize the use of fine and coarse expanded slate lightweight aggregates in developing successful semi-lightweight self-consolidating concrete (SLWSCC) mixtures with densities ranging from 1850 to 2000 kg/m3 (115.5 to 124.9 lb/ft3) and strength of at least 50 MPa (7.25 ksi). All SLWSCC mixtures were developed by replacing either the fine or coarse normal-weight aggregates with expanded slate aggregates. Two additional normal-weight self-consolidating concrete mixtures were developed for comparison. The results indicated that due to the challenge in achieving acceptable self-consolidation, a minimum binder content of at least 500 kg/m3 (31.2 lb/ft3) and a minimum water-binder ratio (w/b) of 0.4 were required to develop successful SLWSCC with expanded slate. The use of metakaolin and fly ash were also found to be necessary to develop successful mixtures with optimized strength, flowability, and stability. The results also showed that SLWSCC mixtures made with expanded slate fine aggregate required more high-range water-reducing admixture than mixtures made with expanded slate coarse aggregate. However, at a given density, mixtures developed with expanded slate fine aggregate generally exhibited better fresh properties in terms of flowability and passing ability, as well as higher strength compared to mixtures developed with expanded slate coarse aggregate.

DOI:

10.14359/51722407


Document: 

19-088

Date: 

March 1, 2020

Author(s):

B. Cantero Chaparro, I. F. Sáez del Bosque, A. Matías Sánchez, M. I. Sánchez de Rojas, and C. Medina

Publication:

Materials Journal

Volume:

117

Issue:

2

Abstract:

A full understanding of the characteristics of the granular skeleton comprising different percentages of conventional and recycled aggregates is requisite to the reusability of construction and demolition waste. This study analyzed the effect of partially replacing natural aggregate with recycled concrete (RCA) and mixed (RMA) aggregates on the performance of granular mixtures. Each type of aggregate was characterized physically, chemically, mineralogically, and mechanically, and the physical and mechanical properties of the mixtures were assessed. Correlations were established to predict the optimal mixture proportions. The recycled aggregates analyzed met most requirements laid down in the national legislation and complied with international recommendations. The mixtures exhibited a close linear correlation between the properties analyzed and the recycled aggregate replacement ratios. For concrete, the upper limit was 75% for RCA and RMA, and for the base and intermediate layers in medium/low traffic roads, 75% for RCA and 35% for RMA.

DOI:

10.14359/51720299


Document: 

18-050

Date: 

January 1, 2019

Author(s):

G. Medina, I. F. Sáez del Bosque, M. Frías, M. I. Sánchez de Rojas, and C. Medina

Publication:

Materials Journal

Volume:

116

Issue:

1

Abstract:

The cement industry, aware of the environmental benefits of partially replacing clinker with supplementary cementitious materials (SCMs), has been including SCMs in its manufacturing process. This paper analyses the effect of one such material, granite waste, on the hydration and mechanical performance of new blended cements and discusses the results of a multivariate analysis of variance (MANOVA) conducted to ascertain the impact of the factors involved on mechanical strength. The findings showed no differences between the hydration phases present in these and standard cement pastes: the C-S-H gels formed had similar characteristics and mean chain lengths. The pastes bearing 20% granite waste nonetheless exhibited slightly lower mechanical performance, a more refined pore size, and a smaller amount of C-S-H gel than the conventional material. The statistical analysis revealed that the presence of waste and curing age had a significant effect. Interage group differences in mean mechanical performance were found to be more significant at later ages in the additioned than in the unadditioned pastes due primarily to the pozzolanic action of the waste.

DOI:

10.14359/51710961


Document: 

17-099

Date: 

January 1, 2018

Author(s):

Weina Meng, V. A. Samaranayake, and Kamal H. Khayat

Publication:

Materials Journal

Volume:

115

Issue:

1

Abstract:

In this study, lightweight sand is used as an internal curing agent in ultra-high-performance concrete (UHPC). A factorial design approach was employed to evaluate the effects of multiple mixture proportioning parameters that are important for mixture optimization of UHPC. The investigated mixture design parameters included the substitution volume ratio of lightweight sand for river sand (LWS/NS: 0 to 25%), the cementitious materials-to-sand volume ratio (cm/s: 0.8 to 1.2), and the water-cementitious materials ratio (w/cm: 0.17 to 0.23). The evaluated properties included fresh properties, compressive strengths at up to 91 days, and autogenous shrinkage at up to 28 days. Statistical models that take into account the coupling effects of mixture proportioning parameters were formulated to predict the UHPC properties. The w/cm and LWS/NS were the most significant parameters influencing the compressive strength and autogenous shrinkage, respectively. By replacing the river sand with 25% lightweight sand, the compressive strength at 91 days increased from 150 to 170 MPa (22.5 to 25.5 ksi) and the autogenous shrinkage at 28 days decreased from 410 to 70 μm/m (410 × 10–6 to 70 × 10–6 in./in.). The mixture with w/cm of 0.23, LWS/NS of 0.25, and cm/s of 1.2 is determined as the optimum UHPC mixture. The material properties of the mixture: the HRWR demand was 0.6%, the 28-day autogenous shrinkage was 260 μm/m (260 × 10–6 in./in.), and the 91-day compressive strength was 147 MPa (22.1 ksi).

DOI:

10.14359/51700995


Document: 

16-006

Date: 

January 1, 2018

Author(s):

Ahmed Abdelbary and Ashraf Ragab Mohamed

Publication:

Materials Journal

Volume:

115

Issue:

1

Abstract:

This paper aims to introduce steel slag as a green construction material. The object of the study is to investigate the possibility and effect of replacing natural coarse aggregate in concrete paving block with electrical arc furnace slag (EAFS) to enhance its properties. The effect of different mixing ratios of EAFS on abrasion resistance, compressive strength, and water absorption were evaluated. It is observed that all the mixtures achieved most of the required ASTM C936 limits. The abrasion resistance and compressive strength of the slag-based mixtures showed higher values compared to the control mixture with conventional limestone aggregate. However, the abrasion requirement for interlocking concrete pavers is debated in the light of ASTM C936 standards. A suggested adaptation of the standard specification for solid concrete interlocking paving units, ASTM C936, is argued to consider macrotexture characteristics of the paver surface—ASTM E965 or ASTM E2157—as one of the paving requirements.

DOI:

10.14359/51700898


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