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This study aims to develop a new thixotropic ultra-high-performance concrete (UHPC) overlay for the repair and strengthening of damaged hot mix asphalt (HMA) pavements. The overlay is purposely designed to accommodate the roadway slope of up to 10% due to presence of viscosifying agent materials. The original UHPC materials are comprised of granite aggregate, ultra-fine calcium carbonate, shrinkage-reducing admixture, viscosifying agent, and expansive agent. The study is conducted with three sets of samples provided and considers thixotropic and mitigated shrinkage properties through comparing control (non-thixotropic) overlay 1 (thixotropic), and overlay 2 (thixotropic) mixtures. Based on the obtained results, only overlay 1 corresponds to the minimum requirement for pavement rehabilitation, with 160-200 mm flowability and -545.3 µm/m free shrinkage. As a result, an average 50 mm thick overlay 1 is selected to repair a damaged HMA pavement (1800 m2), while the field implementation procedures and drawing details are also presented in this paper.

Nuclear energy offers a wide range of applications, which include power generation, X-ray imaging, and non-destructive tests, in many economic sectors. However, such applications come with the risk of harmful radiation, thereby requiring shielding to prevent harmful effects on the surrounding environment and users. Concrete has long been used as part of structures in nuclear power plants, X-ray imaging rooms, and radioactive storage. The direction of recent research is headed toward concrete’s ability in attenuating harmful energy radiated from nuclear sources through various alterations to its composition. Radiation shielding concrete (RSC) is a composite-based concrete that was developed in the last few years with heavy natural aggregates such as magnetite or barites. RSC is deemed a superior alternative to many types of traditional normal concrete in terms of shielding against the harmful radiation, and being economical and moldable. Given the merits of RSCs, this article presents a comprehensive review on the subject, considering the classifications, alternative materials, design additives, and type of heavy aggregates used. This literature review also provides critical reviews on RSC performance in terms of radiation shielding characteristics, mechanical strength, and durability. In addition, this work extensively reviews the trends of development research toward a broad understanding of the application possibilities of RSC as an advanced concrete product for producing a robust and green concrete composite for the construction of radiation shielding facilities as a better solution for protection from sources of radiation. Furthermore, this critical review provides a view of the progress made on RSCs and proposes avenues for future research on this hotspot research topic.

Since the emergence of construction technology, construction of affordable and environmentally-sensible home at fast pace has brought dream home within the reach. Structural Insulated Panel (SIP) has become a topic of interest among researchers in the recent years. SIP has the advantages of minimal material wastage and labour-savingness whilst having potential to save house builders’ time and money as well as retaining the controlled quality. Nonetheless, it suffers from few drawbacks which should be further explored by researchers in its future design. This study present a brief overview of SIP history and common methods and materials utilised for SIP production. It reviews the recent research in the field of SIP by evaluating its application and drawbacks which enable SIP designers improve on SIP. The review of evaluating SIP application and its drawbacks clearly point to the need for further studies to progress beyond the current SIP to an improved one. It might be achieved by replacement of new material with common material used as skin and core of SIP. Considerably more research will need to be done to obtain SIP universal design standard.

The Strut-and-Tie Model (STM) has been incorporated into the codes and standards because of its consistency and rationality since last decade. However, it has encountered few challenges whilst its implementation. The effective compressive strength of strut has been a complex issue among researchers since emergence of STM. This review serves as a base for future developments of STM. It addresses several ways towards enhancing our understanding of strut performance in the STM. It also throws up questions for further investigation of effective compressive strength of strut in the STM. This review is confined to the evaluation of strut effectiveness factor based on the available codes and standards particularly AASHTO LRFD and ACI 318-08. According to the example given in this paper, there is sometimes a marked difference of approximately 50% between strut effectiveness factor recommended by AASHTO LRFD and ACI 318-08. More broadly, research is needed to determine which of the complicated strut effectiveness factor recommended by AASHTO LRFD and the simple one recommended by ACI 318-08 is optimum.

Deep beams are commonly used in tall buildings, offshore structures, and foundations. According to many codes and standards, strut-and-tie model (STM) is recommended as a rational approach for deep beam analyses. This research focuses on the STM recommended by ACI 318-11 and AASHTO LRFD and uses experimental results to modify the strut effectiveness factor in STM for reinforced concrete (RC) deep beams. This study aims to refine STM through the strut effectiveness factor and increase result accuracy. Six RC deep beams with different shear span to effective-depth ratios (a/d) of 0.75, 1.00, 1.25, 1.50, 1.75, and 2.00 were experimentally tested under a four-point bending set-up. The ultimate shear strength of deep beams obtained from non-linear finite element modeling and STM recommended by ACI 318-11 as well as AASHTO LRFD (2012) were compared with the experimental results. An empirical equation was proposed to modify the principal tensile strain value in the bottle-shaped strut of deep beams. The equation of the strut effectiveness factor from AASHTTO LRFD was then modified through the aforementioned empirical equation. An investigation on the failure mode and crack propagation in RC deep beams subjected to load was also conducted.

Strut-and-tie model (STM) method evolved as one of the most useful designs for shear critical structures and discontinuity regions (D-regions). It provides widespread applications in the design of deep beams as recommended by many codes. The estimation of bottle-shaped strut dimensions, as a main constituent of STM, is essential in design calculations. The application of carbon fibre reinforced polymer (CFRP) as lightweight material with high tensile strength for strengthening D-regions is currently on the increase. However, the CFRP-strengthening of deep beam complicates the dimensions estimation of bottle-shaped strut. Therefore, this research aimed to investigate the effect of CFRP-strengthening on the deformation of RC strut in the design of deep beams. Two groups of specimens comprising six unstrengthened and six CFRP-strengthened RC deep beams with the shear span to the effective depth ratios (a/d) of 0.75, 1.00, 1.25, 1.50, 1.75, and 2.00 were constructed in this research. These beams were tested under four-point bending configuration. The deformation of struts was experimentally evaluated using the values of strain along and perpendicular to the strut centreline. The evaluation was made by the comparisons between unstrengthened and CFRP-strengthened struts regarding the widening and shortening. The key variables were a/d ratio and applied load level.

Joints between precast segmental bridge girders (PSBGs) represent the locations of discontinuity through which compression and shear forces are transmitted. Therefore, knowledge of the joint behavior to accurately predict the response of PSBGs is essential. The aim of this research is to investigate the shear behavior, shear capacity, and shear-transfer mechanisms of the ultra-high-performance fiber-reinforced concrete (UHPFRC) keyed dry and epoxy joints. For this purpose, a series of full-scale UHPFRC keyed joint specimens were manufactured and tested with three variable parameters--namely, number of shear keys, confining stress, and the type of joint (dry or epoxy). The observations from experimental tests showed that the capacity of the UHPFRC keyed joints increased with increasing confining pressure applied across the joint, number of shear keys, and the epoxy layers applied on joints. Furthermore, a new design shear model for UHPFRC precast segmental bridges was developed and validated with experimental data. [ABSTRACT FROM AUTHOR]

This paper presents the current state of practice in the development of ultrahigh-performance concrete (UHPC) bridge construction in Malaysia. Since 2006, Dura Technology (DT) has pioneered research in the optimal uses of UHPC in bridge construction through its Sustainable Bridge Construction Initiative. After several years of research and development work, DT has collaborated with the Malaysia Works Ministry to design and build bridges in some of their bridge projects, especially those bridges under the rural development program where sourcing of material, site access, and construction method are major challenges when using conventional methods. The most current information and details on the completed and ongoing UHPC bridge projects in Malaysia are presented. To date, a total of 26 segmental UHPC bridge projects have been constructed and opened for service. In this paper, a selected UHPC bridge case study is examined in terms of the design aspects, quality control, constructability, and of how UHPC has helped to make the bridge more affordable, sustainable, easier to build, and economical. [ABSTRACT FROM AUTHOR]

Strut-and-tie model (STM) has been recommended by many codes and standards as a rational model for discontinuity regions in structural members. STM has been adopted in ACI building code for analysis of reinforced concrete (RC) deep beams since 2002. However, STM recommended by ACI 318-11 is only applicable for analysis of ordinary RC deep beams. This paper aims to develop the STM for CFRP strengthened RC deep beams through the strut effectiveness factor recommended by ACT 318-11. Two sets of RC deep beams were cast and tested in this research. Each set consisted of six simply-supported specimens loaded in four-point bending. The first set had no CFRP strengthening while the second was strengthened by means of CFRP sheets using two-side wet lay-up system. Each set consisted of six RC deep beams with shear span to effective depth ratio of 0.75, 1.00, 1.25, 1.50, 1.75, and 2.00. The value of strut effectiveness factor recommended by ACT 318-11 is modified using a proposed empirical relationship in this research. The empirical relationship is established based on shear span to effective depth ratio. [ABSTRACT FROM AUTHOR]

Strut-and-tie model (STM) method evolved as one of the most useful designs for shear critical structures and discontinuity regions (D-regions). It provides widespread applications in the design of deep beams as recommended by many codes. The estimation of bottle-shaped strut dimensions, as a main constituent of STM, is essential in design calculations. The application of carbon fibre reinforced polymer (CFRP) as lightweight material with high tensile strength for strengthening D-regions is currently on the increase. However, the CFRP-strengthening of deep beam complicates the dimensions estimation of bottle-shaped strut. Therefore, this research aimed to investigate the effect of CFRP-strengthening on the deformation of RC strut in the design of deep beams. Two groups of specimens comprising six unstrengthened and six CFRP-strengthened RC deep beams with the shear span to the effective depth ratios (a/d) of 0.75,1.00,1.25,1.50,1.75, and 2.00 were constructed in this research. These beams were tested under four-point bending configuration. The deformation of struts was experimentally evaluated using the values of strain along and perpendicular to the strut centreline. The evaluation was made by the comparisons between unstrengthened and CFRP-strengthened struts regarding the widening and shortening. The key variables were a/d ratio and applied load level. [ABSTRACT FROM AUTHOR]

Since the emergence of construction technology, construction of affordable and environmentally-sensible home at fast pace has brought dream home within the reach. Structural Insulated Panel (SIP) has become a topic of interest among researchers in the recent years. SIP has the advantages of minimal material wastage and labour-savingness whilst having potential to save house builders' time and money as well as retaining the controlled quality. Nonetheless, it suffers from few drawbacks which should be further explored by researchers in its future design. This study present a brief overview of SIP history and common methods and materials utilised for SIP production. It reviews the recent research in the field of SIP by evaluating its application and drawbacks which enable SIP designers improve on SIP. The review of evaluating SIP application and its drawbacks clearly point to the need for further studies to progress beyond the current SIP to an improved one. It might be achieved by replacement of new material with common material used as skin and core of SIP. Considerably more research will need to be done to obtain SIP universal design standard. [ABSTRACT FROM AUTHOR]

While the database of tests on shear in reinforced concrete members without stirrups is extensive, the pool of test data for fiber-reinforced specimens is limited. Fewer still are tests undertaken on high-performance fiber-reinforced concrete members with the fiber concrete designed to carry the full shear capacity. This paper reports the results of a testing program on ultrahigh-performance steel fiber-reinforced concrete beams. Eight prestressed concrete beams were tested in shear with the test variables being the shear span-to-depth ratio and the quantity and type of steel fibers. The results of the tests, together with additional tests reported in the literature, are compared to the values derived from the plastic shear variable engagement predictive model for the determination of shear strength of steel fiber-reinforced concrete beams. A good correlation is observed with a mean model to experimental strength ratio of 0.92 and coefficient of variation of 0.12. [ABSTRACT FROM AUTHOR]

This article presents an overview of the material characteristics of a Malaysia blend of ultra-high performance 'ductile' concrete (UHPdC). Examples of the environmental impact calculations of UHPdC structures compared to that of conventional reinforced concrete (RC) design are presented. The comparison studies show that many structures constructed from UHPdC are generally more environmentally sustainable than built of the conventional RC with respect to the reduction of CO2 emissions, embodied energy and global warming potential. The enhanced durability of UHPdC also provides for significant improvements in the design life, further supporting the concept of sustainable development. [ABSTRACT FROM AUTHOR]