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International Concrete Abstracts Portal

Showing 1-10 of 313 Abstracts search results

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: 

18-021

Date: 

January 1, 2019

Author(s):

Youngjae Choi and Shih-Ho Chao

Publication:

Structural Journal

Volume:

116

Issue:

1

Abstract:

This paper presents an experimental study on the seismic performance of reinforced concrete (RC) perimeter interior special moment frames (SMFs) that use high-performance fiber-reinforced concrete (HPFRC) in joint and beam plastic hinge regions. This research evaluates the feasibility of using both HPFRC joint and beams as major sources of energy dissipation in an effort to reduce overall damage and repair cost after earthquakes and to provide ease of construction for beam-column connections. A balanced damage concept was used so the energy dissipation was shared by the joint and beam plastic hinges, thereby preventing severe damage from occurring to the beams. This concept together with the mechanical properties provided by HPFRC, including high shear and bond strength, reduce the need of placing a large number of transverse reinforcement in the joint and beam plastic hinge regions. A full-scale HPFRC slab-beam-column (SBC) subassemblage designed with this concept was tested under large displacement reversals. This specimen used a small amount of transverse reinforcement (approximately 20% of that used in a typical RC joint) in the joint and no transverse reinforcement in the beam plastic hinge regions, thus significantly enhancing the constructability. A counterpart conventional RC specimen compliant with ACI 318-14 was tested under the same loading protocol. Both specimens showed stable hysteretic responses up to 3.5% column drift ratio without significant strength degradation, which meets the collapse prevention structural performance according to the criteria given in ACI 374. Experimental results show that the damage in the HPFRC specimen was distributed in both joint and beam ends, whereas the conventional RC specimen had severe damage concentrated in the beam plastic hinging regions. This research proves the feasibility of using ductile HPFRC joint to dissipate seismic energy, thereby balancing the damage between the joint and beams.

DOI:

10.14359/51710875


Document: 

17-391

Date: 

September 1, 2018

Author(s):

Rou-Ling Yeh, Chien-Chuang Tseng, and Shyh-Jiann Hwang

Publication:

Structural Journal

Volume:

115

Issue:

5

Abstract:

To provide practical functions, reinforced concrete (RC) walls in residential buildings often have door or window openings that divide the RC wall into different segments. This study conducted experiments on four RC wall specimens with openings. By observing the crack development within the specimen, the effect of special horizontal reinforcement on the shear strength of vertical wall segments is assessed. Experimental observations show that placing special horizontal shear reinforcement or carbon fiber tapes above and below vertical wall segments at the edges of walls can satisfy nodal force balance at these locations and effectively increase the shear strength of these vertical wall segments. In addition to reporting the experimental results, this study compares the shear strength obtained from experiments and that computed based on the ACI 318-14 Building Code, and proposes an appropriate strut-and-tie model for predicting the shear strength.

DOI:

10.14359/51702377


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


Document: 

16-279

Date: 

November 1, 2017

Author(s):

Mark Bediako, Sudhaunshu Shrikant Purohit, and John Tristan Kevern

Publication:

Materials Journal

Volume:

114

Issue:

6

Abstract:

There is a growing interest on the use of calcined clays as suitable supplementary cementitious materials (SCMs) for construction in recent times. However, the origin of clay presents some form of variations that influences their use as SCM. This study seeks to analyze clay obtained from the Nyamebekyere area of Ghana. The Ghanaian clay was calcined at temperatures of 600, 700, 800, 900, and 1000°C (1112, 1292, 1472, 1652, and 1832°F) in a laboratory furnace. The properties of the raw and calcined clay were characterized using thermal gravimetric analysis (TGA), 27Al and 29Si solid-state magic angle spinning nuclear magnetic resonance (SS MAS NMR), and Fourier transformed infrared (FTIR) spectroscopic techniques. Pozzolanic strength activity indexes (PSAIs) were determined by replacing portland cement with 20% of the calcined materials. The results from the 27Al SS MAS NMR showed that the clay was a 1:1 kaolinitic clay type. The PSAI results were corroborated with the TGA, 27Al and 29Si SS MAS NMR, and the FTIR spectra results to achieve the optimum calcination temperature, which indicated that clay calcined at 800°C (1652°F) attained a more reactive pozzolanic phase that consequently positively influenced the strength activity index. The study recommends calcination temperature of 800°C (1652°F) as the most appropriate temperature for the Ghanaian clay.

DOI:

10.14359/51700896


Document: 

16-347

Date: 

September 1, 2017

Author(s):

Sungchul Chun, Min-Seo Bae, and Byung-Soo Lee

Publication:

Structural Journal

Volume:

114

Issue:

5

Abstract:

The confining effects of the cover and transverse reinforcement are excluded from the ACI 318 provisions on the development length of 43 and 57 mm (No. 14 and No. 18) hooked bars because of the absence of experimental evidence. Twenty-six simulated beamcolumn joint tests were therefore conducted using 43 and 57 mm (No. 14 and No. 18) hooked bars of 550 MPa (80,000 psi) yield strength in this study. The test variables include the embedment length, concrete compressive strength, side cover, and transverse reinforcement. An intentional side-face blowout failure occurred due to the prevention of the other failure modes. As the embedment length and side cover increased, the anchorage capacity of the hooked bars increased as well. By placing ties, the anchorage strength of the hooked bars increased, but a wide scattering of the improved strengths also occurred. At failure, the entire bar force was resisted by the hook bearing only, and the bond along the straight region of the hooked bars vanished. From regression analyses of 74 datasets, including Marques and Jirsa’s tests, a model is proposed for predicting the anchorage strength of hooked bars terminated within exterior beam-column joints.

DOI:

10.14359/51700804


Document: 

16-342

Date: 

July 1, 2017

Author(s):

Inamullah Khan, Arnaud Castel, and Raymond Ian Gilbert

Publication:

Materials Journal

Volume:

114

Issue:

4

Abstract:

This paper focuses on the effects of fly ash on early-age mechanical and viscoelastic properties of concrete and on early-age cracking. Fly ash is a supplementary cementitious material that is mainly used to increase the durability of concrete. The effect on shrinkage-induced cracking of replacing some ordinary portland cement (OPC) with fly ash has not been studied previously. Material properties such as compressive strength, indirect tensile strength, and elastic modulus were measured with different percentage replacements of OPC with fly ash. Tensile creep and drying shrinkage were also measured on two types of specimens by using two different experimental techniques. The cracking age of plain concrete was observed by using a restrained ring test. Results revealed that the strength evolution of fly-ash-blended concrete is lower than the corresponding OPC concrete and the age at which restrained shrinkage cracking first occurs is also reduced. Slightly higher tensile creep coefficients were observed for fly-ash-blended concrete compared to OPC concrete, but drying shrinkage was not altered to any great extent.

DOI:

10.14359/51689898


Document: 

15-270

Date: 

May 1, 2017

Author(s):

Tao Ji, Qiaoling Gao, Wenyuan Zheng, Xujian Lin, and Hwai-Chung Wu

Publication:

Materials Journal

Volume:

114

Issue:

3

Abstract:

In this study, both micro and macro tests were performed to investigate the effect of activator types on the characteristics of the interfacial transition zone (ITZ) in alkali-activated slag concrete (AASC) with presoaked ceramsite. Two types of chemical activators (Na2SO4 and Na2SO4 plus water glass) were used, each leading to unique cement products. Microhardness was measured within ITZ and analyzed together with microstructure observations by scanning electron microscopy (SEM). Macroscopic properties, including compressive strength and splitting tensile strength, were also measured. For the AASCs with natural coarse aggregate and ceramsite activated by Na2SO4, the microhardness and the Ca/Si ratio of the ITZ are lower than that of portland-cement concrete (PC). For the natural coarse aggregate-AASC activated by Na2SO4 plus water glass, the microhardness of the ITZ is higher than that of PC, and the Ca/Si ratio of the ITZ is lower than that of PC; replacing natural coarse aggregate with ceramsite, the microhardness of the ITZ improves further.

DOI:

10.14359/51689473


Document: 

16-080

Date: 

January 1, 2017

Author(s):

Iman Abavisani, Omid Rezaifar, and Ali Kheyroddin

Publication:

Structural Journal

Volume:

114

Issue:

1

Abstract:

A novel feasibility study was launched into real-time structural behavior controlling and improving properties of flexural reinforced concrete (RC) members, using alternating magnetic field (AMF) and alternating current (AC) electricity of different intensities. Hence, a strong AMF of 0.5 tesla (T) was directly applied to some small-scale RC beams in both pasty and solid phases. To allow for better discussion about the effect of AMF, some compressive cube plain concrete (PC) specimens were prepared and exposed to AMF at the same stages as the RC beams were. Then the results were compared and they were found to correlate with each other. Also, the effect of applying AC of different intensities up to 36 ampere (A) to the steel reinforcement system of RC beams was evaluated. It was observed that applying AMF in pasty phase facilitates concrete placing process for RC structures but it has a marginal effect on structural properties of RC beams. As to solid phase, applying AMF to hardened RC beams affected their structural properties such as load-bearing capacity, deflection, bending stiffness, and ductility during the loading history. Regarding AC, ductility of RC beams was found to increase with increase in current intensity, following a cubic function. The results can be a base for construction of a new generation of smart structures through magnetic fields and electric currents.

DOI:

10.14359/51689452


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