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CONTENTS
Volume 10, Number 5, November 2020
 

Abstract
Reduction of disposal of waste materials due to construction demolition has become a great concern in recent decades. The research work presents the hardened properties of concrete where the partial substitution of recycled coarse aggregate with natural aggregate in amount of 0%, 10%, 30% and 50%. By using different mixed proportions, fresh and hardened properties of concrete were conducted for this investigation. These properties were compared with control concrete. It can be seen that all of the hardened properties of concrete were decreased with the increasing percentage of recycled aggregate in concrete mixes. It was noticed that up to 30% recycled aggregate replacement can be yielded the optimum strength when it used in normal concrete. Finally, it can be said that disposed recycled concrete utilizing as a partial replacement in natural aggregate is a great way to reuse and reduce environmental hazards which achieve sustainability approach in the construction industry.

Key Words
waste concrete; concrete; recycled coarse aggregate; performance; compressive strength

Address
Shanjida A. Shohana, Md. I. Hoque and Md. H.R. Sobuz: Department of Building Engineering and Construction Management, Khulna University of Engineering and Technology,
Khulna-9203, Bangladesh

Abstract
This study aimed to develop reference materials (RMs) for mortar that can simulate the initial flow characteristics with constant quality over a long period. Through the previous research on the development of RMs for cement paste, the combination of limestone, glycerol, and water was used as the basic matrix for developing RMs for mortar in this study. In addition, glass beads of three particle sizes (0.5, 1.0, and 2.0 mm) and ISO standard sand were selected as tentative candidates to derive fine aggregate substitutes. The mixture of glass beads could simulate the initial flow characteristics of mortar, but under the same mixing ratio, replicates showed an unstable tendency to indicate inconsistent values due to the generation of electrostatic properties between materials and equipment. On the other hand, the mixture using ISO standard Sand not only simulates the constant flow characteristics for a long period of time, but also shows stable results with little error in replicates. Therefore, limestone, glycerol, ISO standard sand, and water were finally determined as components that met the required properties of RMs for mortar. The effect of each component on the flow characteristics of RMs was analyzed. It was found that glycerol increased the cohesion between the particles of standard sand, resulting in a constant increase both in the plastic viscosity and yield stress. Both limestone and standard sand had a dominant effect on the yield stress. The relationships between various mortar mixing ratios and the corresponding mixing ratios of RMs were established. In addition, the results of the verification experiment showed that the rheological properties of the RMs obtained through the relationships correlated with various water/cement ratios and the fine aggregate volume fractions of mortar obtained with same manner. In other words, the RMs for mortar developed in this study can be used as standard samples because they can simulate the initial flow characteristics of mortar of various mixing ratios for a long period without any chemical changes.

Key Words
rheology; mortar; reference materials; yield stress; flow characteristics

Address
Dong Kyu Lim and Myoung Sung Choi: Department of Civil and Environmental Engineering, Dankook University, Gyeonggido Jukjeon-ro 152, Republic of Korea

Abstract
The given research focuses on examining the effect of relatively humidity (RH) and curing temperature on the hydrates as well as the porosity of calcium sulfoaluminate (CSA) cement pastes. Numerous tests, which consist of mercury intrusion porosimetry (MIP), thermosgravi metric (TG) and X-ray diffraction (XRD) were conducted. Various characterization techniques which include, scanning electron microscopy, Fourier transform microscopy along with X-ray diffraction evaluations were conducted on the samples to examine phase formation and crystallinity, morphology and microstructure along with bond formations and functional groups, respectively. During long-term study, the performance of concrete which consisted of limestone and flash-calcined was close to those from standard Portland cement concrete. Traditional classifications and methods of corrosion were widely used for the assessment of steel in concrete which may get employed to concrete which contains LC3 to recalibrate the range of polarization resistance for passitivity condition. For example, there is up to 79.5% and 146% respective flexural and compressive strengths. Moreover, they developed more advance electrical and thermo-mechanical performance with a substantial reduction in absorption of water of close to 400%. These advantages allow this research crucial to evaluate how these methods can be applied. Additionally, the research evaluates developed and more advanced cement preservation and repair techniques. The conclusion suggests concerted efforts by various stakeholders such as policy makers to enable low-carbon rates.

Key Words
cement; concrete; XRD; flexural strength; preservation techniques; crystallinity; polarization resistance

Address
Jiandong Huang: School of Mines, China University of Mining and Technology, Xuzhou, China
Rayed Alyousef: Department of Civil Engineering, College of Engineering, Prince Sattam bin Abdulaziz University, Al-kharj 11942, Saudi Arabia
Meldi Suhatril: Department of Civil Engineering, Faculty of Engineering, University of Malaya, 50603, Kuala Lumpur, Malaysia
Shahrizan Baharom: Department of Civil Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, UKM, 43600, Bangi, Selangor, Malaysia
Hisham Alabduljabbar: Department of Civil Engineering, College of Engineering, Prince Sattam bin Abdulaziz University, Al-kharj 11942, Saudi Arabia
Abdulaziz Alaskar: Department of Civil Engineering, College of Engineering, King Saud University, Riyadh 11362, Saudi Arabia
Hamid Assilzadeh: Institute of Research and Development, Duy Tan University, Da Nang 550000, Vietnam

Abstract
This study investigated the effect of alkaline activators - NaOHaq (NH) (NH: 0-16 M) and Na2SiO3aq (NS) (NS/NH: 0-3.5) in the synthesis of silico-manganese fume (SMF) and ground blast furnace slag (BFS) blended alkali-activated mortar (AASB). The use of individual activator was ineffective in producing AASB of sufficient fresh and hardened properties, compared to the synergy of both activators. This may be attributed to incomplete dissolution and condensation of oligomers required for gelation of the binder. An inverse relationship was noted among the fresh properties and the NH concentration or NS/NH ratio. This was influenced by the dissolution and condensation of silicate monomers under polymerization process. The maximum 28-day strength of ~45 MPa, setting time of 60 min and flow of 182 mm was obtained with the use of combined activators (10M-NH and NS/NH=2.5). The combined activators at NS/10M-NH=2.5 constituted SiO2/Na2O, H2O/Na2O and H2O/SiO2 molar ratio of 1.61, 17.33 and 10.77, respectively. This facilitated the formation of C-S-H, C/K-A-S-H and C-Mn-S-H in the framework together with an increase in the crystallinity due to more silicate re-organization within the aluminosilicate chain. On comparison of the high concentrated with mild alkali synthesized product, it revealed that the concentration of OHand Si monomers together with alkali metals influenced the dissolution of precursors and embedment of the constituent elements in the polymeric matrix. These factors eventually contributed to the microstructural densification of the mortar prepared with NS/10M-NH=2.5 thereby enhancing the compressive strength.

Key Words
alkali concentration; activator dosage; molar composition; silico-manganese fume; blast furnace slag; strength; microstructure

Address
Muhammad Nasir: Department of Civil and Construction Engineering, College of Engineering, Imam Abdulrahman Bin Faisal University, Dammam 31451, Saudi Arabia
Megat Azmi Megat Johari: School of Civil Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Pulau Pinang, Malaysia
Moruf Olalekan Yusuf: Department of Civil Engineering, University of Hafr Al Batin, Hafr Al Batin 31991, Saudi Arabia
Mohammed Maslehuddin: Center for Engineering Research, Research Institute, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia
Mamdouh A. Al-Harthi: Department of Chemical Engineering, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia; Center of Research Excellences in Nanotechnology, Research Institute, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia

Abstract
Waste glass is a global solid waste with huge reserves. The discarded waste glass has caused a series of problems such as resource waste and environmental pollution, so it is urgent to recycle waste glass with high replacement level. Glass powder (GP), as a supplementary cementitious material (SCM), used in cement-based materials has already become one of the important ways to recycle waste glass mainly attributed to its pozzolanic reaction and filling effect, especially to the suppressed ASR expansion. This paper demonstrates an overview of the properties of GP and its effect on the fresh and mechanical properties of cement-based materials. The study found that the influence of GP on the performance of cement-based materials mainly depends on its content, particle size, color and type, curing conditions, and other SCMs. Finally, based on the problems involved in the investigation of concrete containing GP, some corresponding suggestions and efforts are given to further guide the utilization of GP in cement-based materials.

Key Words
glass powder; supplementary cementitious material; cement-based materials; fresh properties; mechanical properties

Address
Zhi-hai He, Ying Yang, Hao Zeng, Jing-yu Chang, Jin-yan Shi: College of Civil Engineering, Shaoxing University, Shaoxing 312000, China
Bao-ju Liu: School of Civil Engineering, Central South University, Changsha 410075, China

Abstract
For the purpose of improving the properties of UHPC as well as the economic efficiency in production of the material, Availability of river sands as fine aggregate instead of micro silica sand were investigated. Four different sizes of river sands were considered. Using river sand instead of micro silica sand increased the flowability, and decreased the yield stress and plastic viscosity in rheological properties, and the effect was higher with larger particle size of river sand. It was demonstrated by analyses based on the packing density. In the results of compressive strength and elastic modulus, even though river sand was not as good as micro silica sand, it could provide high strength of over 170 MPa and elastic modulus greater than 40 GPa. The difference in compressive strength depending on the size of river sand was explained with the concept of maximum paste thickness based on the packing density of aggregate. The flexural performance with river sand also presented relatively lower resistance than micro silica sand, and the reduction was greater with larger particle size of river sand. The flexural performance was proven to be also influenced by the difference in the fiber orientation distribution due to the size of river sand.

Key Words
UHPC; sand; aggregate size; packing density; rheological properties; compressive strength; flexural performance

Address
Su-Tae Kang: Department of Civil Engineering, Daegu University, 201, Daegudae-ro, Jillyang, Gyeongsan, Gyeongbuk, 38453, Republic of Korea

Abstract
In recent years, many studies have been done on the performance of concrete containing glass powder (GP). For the purpose of widespread use of GP in concrete mixes, a knowledge of the performance of such a mixture after a fire is essential for the perspective of structural use. This research work was carried out to evaluate the performance of High Performance Concrete (HPC) made with GP after being exposed to elevated temperature. The studied mixtures include partial replacement of cement by GP with up to 30%. The mechanical performance and structural alterations were assessed after high temperature treatment from 200oC to 800oC. The mechanical performance was evaluated by testing the specimens to the compressive and tensile strength. In addition, the mass loss and the porosity were measured to notice the structural alterations. Changes in microstructure due to temperature was also investigated by the X-ray diffraction (XRD) and thermal gravimetric analyses (TGA) as well as porosity adsorption tests. The results of the concrete strength tests showed a slight difference in compressive strength and the same tensile strength performance when replacing a part of the cement by GP. However, after high temperature exposition, concrete with GP showed better performance than the reference concrete for temperature below 600oC. But, after heating at 800oC, the strength of the concrete with GP drop slightly more than reference concrete. This is accompanied by an important increase in mass loss and water porosity. After the microstructure analysis, no important changes happened differently for concrete with GP at high temperature except a new calcium silica form appears after the 800

Key Words
glass powder; concrete; high temperature; mechanical properties; microstructural changes

Address
Abdenour Kadik: Laboratory of Civil Engineering and Environment Materials (LMGCE), Ecole Nationale Polytechnique, Algiers-10 rue Freres Oudek, El-Harrach 16200, Algiers, Algeria; Laboratory of Applied Mechanic (LMA), University of Science and Technology of Oran, El Mnaouar, BP 1505, Bir El Djir 31000, Oran, Algeria
Messaouda Cherrak: Laboratory of Civil Engineering and Environment Materials (LMGCE), Ecole Nationale Polytechnique, Algiers-10 rue Freres Oudek, El-Harrach 16200, Algiers, Algeria
Abderrahim Bali: Laboratory of Civil Engineering and Environment Materials (LMGCE), Ecole Nationale Polytechnique, Algiers-10 rue Freres Oudek, El-Harrach 16200, Algiers, Algeria
Djilali Boutchicha: Laboratory of Applied Mechanic (LMA), University of Science and Technology of Oran, El Mnaouar, BP 1505, Bir El Djir 31000, Oran, Algeria
Kinda Hannawi: Laboratory of Civil Engineering and Mechanical Engineering, National Institute of Applied Sciences, 35000 Rennes, France

Abstract
This study investigated the effect of horizontal casting joints on the mechanical properties and structural behavior of sustainable self-compacting reinforced concrete beams (SCRCB). The experimental research consisted of two stages. The first stage used four types of concrete mixtures which were produced to indicate the effects of cement replaced with cement waste at 0%, 5%, 10%, and 15% by weight of cement content on fresh concrete properties of self-compacting concrete (SCC) such as, passing ability, filling ability, and segregation resistance. In addition, mechanical properties such as compressive, tensile, and flexural strength were also studied. The second stage selected the best mixture from the first stage and studied the effect of horizontal casting joints on the structural behavior of sustainable SCRCBs. The effect of horizontal casting joints on the mechanical properties and structural behavior were at the 25%, 50%, 75%, and 100% of sample height. Load deflection, failure mode, and theoretical analysis were studied. Results indicated that the incorporation of replacement with cement waste by 5% to 10% led to economic and environmental advantages, and the results were acceptable for fresh and mechanical properties. The results indicated that delaying the time for casting the second layer and increasing the cement waste in concrete mixtures had a great effect on the mechanical properties of SCC. The ultimate load capacity of horizontal casting joints reinforced concrete beams slightly decreased compared with the control beam. The maximum deflection of casting joint beams with 75% of samples height is similar with the control beam. The experimental results of reinforced concrete beams were substantially acceptable with the theoretical results. The failure modes obtained the best forced casting joint on the structural behavior at 50% height of casting in the beam.

Key Words
horizontal casting joints; self-compacting reinforced concrete, mechanical properties, structural behavior

Address
Omar Mohamed Omar Ibrahim: Department of Civil Construction and Architecture, Faculty of Technology and Education, Suez University, Suez, Egypt; Higher Institute for Engineering and Technology at ElManzal, Ad Daqahliyah, Egypt
Ashraf Mohamed Heniegal: Department of Civil Engineering, Faculty of Engineering, Suez University, Suez, Egypt
Khamis Gamal Ibrahim: Department of Civil Construction and Architecture, Faculty of Technology and Education, Suez University, Suez, Egypt
Ibrahim Saad Agwa: Department of Civil Construction and Architecture, Faculty of Technology and Education, Suez University, Suez, Egypt; Department of Civil Engineering, El-Arish High Institute for Engineering and Technology, El-Arish, North Sinai, Egypt


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