Effects of Using Seawater and Recycled Coarse Aggregates on Plain Concrete Characteristics

Using seawater and/or recycled coarse aggregates (RCA) for concrete mixing is deemed advantageous from a sustainability perspective. This paper reports on the results of an experimental study on fresh and hardened properties of concrete mixed with seawater and RCA. Three concrete mixtures were investigated, namely, Mix A (traditional concrete), Mix B (concrete made with seawater), and Mix C (concrete made with seawater and RCA). It was concluded that the use of seawater and/or RCA had a notable effect on fresh concrete properties. Mix B concrete showed a slightly lower strength performance than that of Mix A (<15%), whereas the strength of Mix C concrete had a significant drop (~30%) compared to the reference (Mix A). The permeability performance of hardened concrete for Mixes A and B was similar, whereas Mix C concrete showed 60% increase in water absorption and 100% increase in chloride permeability as compared to Mix A

Steel Reinforced Grout for Strengthening of RC T-section Beams Deficient in Shear

numerous causes. Thus, proper strengthening and rehabilitation techniques are required to restore the strength and extend the service life of the structures. Steel reinforced grout (SRG) has recently been introduced as an efficient and economical strengthening solution, however, the study on its application for the strengthening of shear-deficient RC beams is scarce. Thus, this paper is aimed to investigate the efficacy of SRG for shear strengthening of RC beams with the focus on SRG/stirrups interaction. Six T-cross section beams were grouped into three series based on their internal shear reinforcement ratio and tested under three-point bending. Each series comprised of one reference and one SRG-strengthened beam. The test results revealed that SRG laminates are an effective technique to increase the shear capacity of RC beams. Up to 71% increase in the load-carrying capacity of the strengthened beams was achieved. The increase in the internal shear reinforcement has shown to reduce the shear-strengthening performance of SRG

Long-Term Cost Performance of Corrosion-Resistant Reinforcements in Structural Concrete

Corrosion, which leads to the premature deterioration of reinforced concrete (RC) structures, is increasingly an issue of global concern. Accordingly, corrosion-resistant materials have emerged as alternative reinforcement solutions in concrete structures. Yet, the high initial cost of such materials may mitigate their potential use. This paper reports on the results of two life-cycle-cost-analysis (LCCA) studies that aim at verifying the long-term cost performance of corrosion-resistant reinforcements in structural concrete. The first study conducted a 100-year-based LCCA study to evaluate the relative cost savings of structural concrete that combines seawater, recycled coarse aggregates, and glass fiber-reinforced polymer (GFRP) reinforcement in high-rise buildings as compared to a traditional reinforced concrete (i.e., freshwater-mixed, natural-aggregate, black-steelreinforced). In the second study, a life-cycle-cost comparison was established among four reinforcement alternatives, viz., conventional steel, epoxy-coated steel, stainless steel, and GFRP for a RC water chlorination tank considering a 100-year study period. The results of these two studies suggest that the use of corrosion-resistant reinforcement (especially GFRP) in structural concrete may potentially lead to significant cost savings in the long term: the net present cost of GFRP-RC structures was generally 40-50% lower than that reinforced with black steel.The authors would like to acknowledge the fund received by the NPRP grant # NPRP 9-110-2-052 from Qatar National Research Fund (a member of Qatar Foundation). The findings of this study are solely the responsibility of the author

Near Surface Embedded Application for FRCM Strengthening of RC Beams in Flexure

In this paper, the efficacy of a recent strengthening technique, referred to as Near Surface Embedded (NSE), has been investigated for flexural strengthening of Reinforced Concrete (RC) beams using Fabric Reinforced Cementitious Matrix (FRCM). The process of applying NSE-FRCM strengthening technique involves removing the concrete layer at the beam's soffit (being the most deteriorated), which is then replaced by the FRCM composite. In this study, seven RC beams were constructed and tested under four-point loading considering two test variables, namely, (a) FRCM material (Polyparaphenylene Benzobisoxazole (PBO)/carbon/glass), and (b) strengthening configuration (NSE/ Externally-Bonded (EB)). Amongst the three FRCM materials, the PBO-FRCM system offered the highest strengthening effectiveness (i.e., highest gain in the load carrying capacity). The average gain in the load-carrying capacity was 45% and 58% for the NSE- and EB-FRCM strengthened beams, respectively, compared to the reference (i.e., non-strengthened) specimen. Nonetheless, the results showed a clear advantage for NSE-FRCM strengthening systems over those externally bonded in terms of ductility performance. The advantage of NSE over EB strengthening was also demonstrated by the improved FRCM/concrete bond associated with NSE-FRCM applicationThis paper was made possible by NPRP grant # NPRP 7-1720-2-641 from the Qatar national research fund (a member of Qatar Foundation). The findings achieved herein are solely the responsibility of the authors

Verification of ACI- 549 Code for Flexural Strengthening of Reinforced Concrete Beams Using FRCM

This paper presents an analytical study to verify the ACI 549-4R-16 code for experimentally tested Reinforced Concrete (RC) beams, which were strengthened to enhance the flexural capacity using Fiber-Reinforced Cementitious Mortars (FRCM). Twelve RC beam specimens having 2500 mm length, 150 mm width, and 260 mm depth were prepared with two different reinforcement ratios (?_s^D12=0.72% and ?_ s^D16=1.27%), and were then strengthened with two different FRCM systems, namely carbon and polyparaphenylene-benzobisoxazole (PBO) FRCM systems. Two RC beams were tested as control specimens. Six beams were externally reinforced using single, double and triple layers of carbon FRCM system, while the remaining four beams were repaired with one and two layers of PBO FRCM system. The strengthened RC beams were tested in flexural under four-point monotonic loading. The experimental results revealed that a reasonable gain in flexural strength was achieved for both FRCM systems, with up to 78% increase in flexural capacity for carbon FRCM systems and up to 27.5% for PBO FRCM system over that of their control specimens. Further, the results obtained from the theoretical approach using the ACI 549 code conform well with the experimental loadcarrying capacities. Moreover, the values obtained for experimental to theoretical ratio are quite close to 1.00 which somewhat shows satisfactory computational results

Life Cycle Assessment for Fiber-Reinforced Polymer (FRP)nComposites Used in Concrete Beams: A State-of-the-Art Review

Fiber-reinforced polymer (FRP) composites have become popularly utilized in structural engineering applications. The common use of the FRP composites is related to their economic benefits that can be observed right away or in a long-time period. With increasing concern about global warming and the shortage of natural resources, it is essential to study the environmental implications of the use of FRP composites. Life cycle assessment (LCA) is one of the most common techniques that can be used to take the environmental impact of the FRP into consideration. This paper presents a literature review about the LCA of FRP composites in concrete beams. The LCA results reported in the literature confirmed the use of FRP composites for reinforcing the RC beams instead of conventional steel rebars or that the strengthening of RC beams instead of demolishing and reconstruction is a more environment-friendly approach

International Conference on Civil Infrastructure and Construction (CIC 2020)

This is the proceedings of the CIC 2020 Conference, which was held under the patronage of His Excellency Sheikh Khalid bin Khalifa bin Abdulaziz Al Thani in Doha, Qatar from 2 to 5 February 2020. The goal of the conference was to provide a platform to discuss next-generation infrastructure and its construction among key players such as researchers, industry professionals and leaders, local government agencies, clients, construction contractors and policymakers. The conference gathered industry and academia to disseminate their research and field experiences in multiple areas of civil engineering. It was also a unique opportunity for companies and organizations to show the most recent advances in the field of civil infrastructure and construction. The conference covered a wide range of timely topics that address the needs of the construction industry all over the world and particularly in Qatar. All papers were peer reviewed by experts in their field and edited for publication. The conference accepted a total number of 127 papers submitted by authors from five different continents under the following four themes: Theme 1: Construction Management and Process Theme 2: Materials and Transportation Engineering Theme 3: Geotechnical, Environmental, and Geo-environmental Engineering Theme 4: Sustainability, Renovation, and Monitoring of Civil InfrastructureThe list of the Sponsors are listed at page 1

Parametric Optimization of RC Beams Strengthened with FRCM Using FE Modelling and Response Surface Methodology

This study focuses on the numerical and statistical analyses to predict the mid-span moment capacity of RC beams strengthened with fabric reinforcement cementitious mortar (FRCM) laminate. A finite element model (FEM) has been built to simulate twelve RC beams strengthened with two types of FRCM, namely Polyparaphenylene benzobisoxazole (PBO) FRCM and Carbon (C) FRCM. The FE models were verified based on experimental work available in the literature. The finite element models have shown a good agreement with experimental results in terms of maximum load-carrying capacity, load-deflection curves, and concrete strain values. The numerical simulation was followed by a parametric study on 42 models using face centred response surface methodology (RSM). Combining FEM and RSM, a novel mathematical model has been proposed to predict the mid-span moment capacity of the RC beams strengthened with FRCM. The results of the proposed model have shown optimal predictability with R2 equal to 90.34%. In addition, the proposed model agreed with the ACI design procedures and the existing literature

Engineering students' approaches to learning and views on collaboration: How do both evolve in a PBL environment and what are their contributing and constraining factors?

Background: This study investigated the development of engineering students' approaches to learning and views on collaboration in a PBL environment. Material and methods: An explanatory mixed research approach was employed with participants from four PBL-implementing engineering courses in Qatar and China. 197students responded to two surveys, and 168 students participated in group interviews. Results: While the study reveals increased adoption of deep approaches to learning on team projects, little influence on surface approaches to learning was found. The study also provides evidence supporting the positive relationship between students' adoption of deep learning approaches and their acknowledgement of values of collaboration in teamwork. Conclusions: This study suggests that while PBL characteristics may support deep learning, certain factors may underpin surface learning, including a feeling of insecurity during first experiences with it, lack of skills, and assessment methods that favor surface learning. Further efforts on engaging students with PBL may benefit both deep learning and team effectiveness.Scopu