Spin casting is the oldest method of manufacturing precast concrete pipes among all existing meth... more Spin casting is the oldest method of manufacturing precast concrete pipes among all existing methods. While improved concrete mixtures incorporating fibers for other methods of concrete pipe manufacturing, such as the vibration method and roller compaction method, have been developed, no such concrete mixture has yet been developed for spun-cast concrete pipes. This study was designed to explore the possibility of incorporating locally manufactured steel fibers and commercially available polypropylene fibers to develop an improved concrete mixture for use in the manufacturing of full-scale spun-cast concrete pipes. The used steel fibers were of two types, i.e., straight and bundled steel fibers, manufactured by cutting locally available long straight and bundled steel wires, respectively. Various dosages of steel fibers (i.e., 20, 30, 40, and 50 kg/m3) and polypropylene fibers (i.e., 5, 10, 15, and 20 kg/m3) were used in mono and hybrid (steel and polypropylene) forms. The propertie...
In this study, the durability of cement-based repairs was observed, especially at the interface o... more In this study, the durability of cement-based repairs was observed, especially at the interface of debonding initiation and propagation between the substrate–overlay of thin-bonded cement-based material, using monotonic tests experimentally and numerically. Overlay or repair material (OM) is a cement-based mortar with the addition of metallic fibres (30 kg/m3) and rubber particles (30% as a replacement for sand), while the substrate is a plain mortar without any addition, known as control. Direct tension tests were conducted on OM in order to obtain the relationship between residual stress-crack openings (σ-w law). Similarly, tensile tests were conducted on the substrate–overlay interface to draw the relationship between residual stress and opening of the substrate–overlay interface. Three-point monotonic bending tests were performed on the composite beam of the substrate–overlay in order to observe the structural response of the repaired beam. The digital image correlation (DIC) me...
The continuous development of the marble industry has led to an increase in the accumulation of w... more The continuous development of the marble industry has led to an increase in the accumulation of waste marble sludge causing landfilling and health-associated issues. The intention of the current study is to explore the potential of waste marble sludge powder (MS) utilization as a means of controlling alkali-silica reaction (ASR) in concrete. Specimen (cubes, prisms, and mortar bars) were prepared to incorporate reactive aggregates and various proportions of MS ranging from 5% to 40% as a replacement for aggregates. Expansion and mechanical strength characteristics were determined to investigate the effectiveness of MS to control ASRfor up to 150 days. Results revealed that on replacing aggregates in the control specimen with 25% MS, the ASR expansion at 14 days reduced from 0.23% to 0.17%, and the expansion at 28 days reduced from 0.28% to 0.17% which is within limits as per American Standard for Testing of Materials (ASTM) C1260. Furthermore, specimens incorporating MS exhibited im...
Although the disposal of waste ashes causes environmental hazards, recycling them helps in reduci... more Although the disposal of waste ashes causes environmental hazards, recycling them helps in reducing their harmful impacts and improves the characteristics of building materials. The present study explores the possible use of locally available waste ashes including Rice husk ash (RHA)and Silica Fumes (SF) as a partial replacement for cement in concrete to counter the negative impact of alkali-silica reactions (ASRs). In the present study, ternary blends including RHA (0–30%), SF (5% and 10%) and Portland cement were investigated. The amorphous behavior of RHA and SF was confirmed by conducting an X-ray diffraction analysis. A petrography analysis was carried out to ensure the reactive nature of aggregates used to prepare the concrete specimen. Accelerated mortar bar tests were performed in accordance with ASTM C 1260 for up to 90 days. It was revealed that specimens incorporating a ternary blend of SF, RHA, and Portland cement exhibited less expansion compared to the control specimen...
Each year, about 730 million tons of bottom ash is generated in coal fired power plants worldwide... more Each year, about 730 million tons of bottom ash is generated in coal fired power plants worldwide. This by-product can be used as partial replacement for Portland cement, favoring resource conservation and sustainability. Substantial research has explored treated and processed coal bottom ash (CBA) for possible use in the construction industry. The present research explores using local untreated and raw CBA in mitigating the alkali–silica reaction (ASR) of reactive aggregates in concrete. Mortar bar specimens incorporating various proportions of untreated CBA were tested in accordance with ASTM C1260 up to 150 days. Strength activity index (SAI) and thermal analysis were used to assess the pozzolanic activity of CBA. Specimens incorporating 20% CBA achieved SAI greater than 75%, indicating pozzolanic activity. Mixtures incorporating CBA had decreased ASR expansion. Incorporating 20% CBA in mixtures yielded 28-day ASR expansion of less than the ASTM C1260 limit value of 0.20%. Scanni...
Exponential development of post-yield strain (Ԑpost) is a pivotal indicator of failure in embankm... more Exponential development of post-yield strain (Ԑpost) is a pivotal indicator of failure in embankments constructed on soft saturated clays. This paper characterizes saturated clay stratum comprising very soft to very stiff stratigraphy, with plasticity index (PI) ranging from 19% to 31%, by performing widely used geotechnical engineering tests, i.e., the prebored pressuremeter (PMT) test, the triaxial (TXL) test, and constant-rate-of-strain (CRS) consolidation. PMT, TXL, and CRS tests were performed at a strain rate range of 0.18%/min to 0.21%/min to explore the yield stress (σ′y), the pre-yield strain (Ԑpre), and the post-yield strain (Ԑpost). Results indicate that Ԑpost/Ԑpre for PMT, TXL, and CRS stress–strain curves range from 2.7 to 19 in the loading phase and 2 to 21 in the unloading phase. An exponential increase in Ԑpost/Ԑpre is observed in the range of 10 to 21 for very soft to soft clay which is congruent with the realistic sustainable range of 4 to 30 for embankment failure...
Pakistan Journal of Engineering and Applied Sciences, 2016
Self compacting concrete (SCC) is a type of concrete which can flow and spread through reinforcem... more Self compacting concrete (SCC) is a type of concrete which can flow and spread through reinforcement and narrow sections which fills the empty spaces completely without any mechanical vibration. This type of concrete requires large quantity of powder, for which either fine pozzolanic (e.g. fly ash, ground granulated blast furnace slag and silica fume etc) or non-pozzolanic additions (crushed limestone or sand stone etc) are used. The composition of this blend of cement and filler material is significant in SCC, as high amount of cement with lower water content may cause autogenous shrinkage. Therefore, the use of non-pozzolans material with cement needs to be investigated. The concrete industry is among the largest consumer of raw materials. Limestone fillers are generally used in concrete. As marble stone is of limestone origin i.e. marble is formed by metamorphism of limestone. The effect of addition of non-pozzolans powder waste from marble industry is studied for its suitability...
Pakistan Journal of Engineering and Applied Sciences, 2016
Nondestructive evaluation of existing structures is a vital part and an active area of research i... more Nondestructive evaluation of existing structures is a vital part and an active area of research in civil engineering industry. Whenever modifications in a structure or its use are proposed the process begins with the evaluation of existing condition. Rebound hammer (RH) and ultrasonic pulse velocity (UPV) tests are the two readily available and easy-to-perform methods that are widely used in the industry. Current research work is focused on evaluation of an eight years old, half-built reinforced concrete building. The objective was to gather information to decide about the future construction and use. The study concludes that concrete is of reasonable quality and building is appropriate for future construction and use. However, one column in the basement has very poor quality concrete and needs strengthening. Paper also provides a comparison of existing regression models for the prediction of concrete strength based on RH and UPV test data.
Prestressed concrete girders are the main superstructure elements in many bridge structures. Shea... more Prestressed concrete girders are the main superstructure elements in many bridge structures. Shear failures in these girders are undesirable due to brittle failure and little warning time. To prevent shear controlled brittle failure, it is normal practice to increase the amount of transverse reinforcement in flexural members. However, past studies have revealed that even higher transverse reinforcement ratios (i.e. > 4%) may not be able to eliminate shear failure in some cases. Moreover, the increased reinforcement makes it more difficult to place and consolidate the concrete. This research program aimed to investigate the feasibility of replacing traditional shear reinforcement in prestressed concrete beams with steel fibers. A total of 14 rectangular and 8 I-shaped prestressed concrete beams were investigated after subjecting them to two-point loading test. The beams were casted with steel fiber ratios ranging from 0.75% to 2.00%. Experimental results revealed that the inclusio...
Pakistan has vast potential of concrete aggregates due to having numerous mountainous ranges. How... more Pakistan has vast potential of concrete aggregates due to having numerous mountainous ranges. However, the properties of these aggregates are yet to be explored as scant research has been carried out in this area. In this study, an experimental approach was adopted to compare the engineering properties of widely used coarse aggregates in Pakistan. Aggregate samples were gathered from four various quarries in accordance with ASTM sampling procedure and their physical as well as mechanical properties were evaluated through laboratory testing according to ASTM and BS standards. Tests were performed on Margalla, Sargodha, Barnalla and Mangla crushes. Different concrete specimens were also prepared using the above mentioned aggregates and tested for their mechanical properties (compressive, tensile and flexural strengths). Test results revealed that the aggregates from evaluated quarries are suitable to be used in concrete. Each sample of aggregates have different characteristics which i...
Pakistan Journal of Engineering and Applied Sciences, 2017
Pakistan is currently facing massive energy crisis and requiring huge investment into the power t... more Pakistan is currently facing massive energy crisis and requiring huge investment into the power transmission line infrastructure. The longest transmission lines of the country are of 220 kV lines stretching up to 7359 km. The contemporary factored design wind load effects for overhead lattice transmission line tower are evaluated based on the applicable wind load factor, gust response factor and design wind speed as recommended by WAPDA/IEC Specifications (1988), ASCE-74 (1991) and ASCE-7 (2005). The current factors and design wind speed were developed considering linear elastic responses. However, information on the non-linear inelastic responses of such towers under dynamic wind loading and on the structural capacity of towers in relation to the design capacities is lacking. The knowledge and assessment of the capacity curve and its relation to the design strength is important to evaluate the integrity and reliability of these towers. Therefore, in this study, analysis was perform...
ABSTRACT Ultra-high performance concrete (UHPC) is a new generation of steel fiber-reinforced con... more ABSTRACT Ultra-high performance concrete (UHPC) is a new generation of steel fiber-reinforced concrete with superior mechanical and durability properties. However, limited data is available on the influence of the steel fiber length and dosage on UHPC mechanical and durability performance. Therefore, in this study, a number of UHPC mixtures with varying steel fiber lengths (8 mm (0.31 in), 12 mm (0.47 in) and 16 mm (0.62 in)) and dosages (1%, 3% and 6%) by mixture volume were tested. Mechanical properties of UHPC including compressive, splitting tensile and flexural strengths were assessed. Moreover, its resistance to chloride ions penetration and mechanical degradation under various chloride exposures (i.e. 3.5% and 10%) were evaluated. Results showed an increase in mechanical properties as the fiber dosage increased. UHPC mixtures incorporating short steel fibers exhibited enhanced flexural properties compared to that of mixtures with similar volume of longer steel fibers. At higher fiber dosage, UHPC mixtures exhibited relatively improved durability. Moreover, no degradation in UHPC mechanical properties was observed after exposure to various chloride ions solutions.
ABSTRACT The overall stability of a segmental tunnel lining ring is highly dependent on the struc... more ABSTRACT The overall stability of a segmental tunnel lining ring is highly dependent on the structural integrity of its individual precast segments, which provide protection against the surrounding exposure conditions. In this study, the settlement and punching behavior of full-scale conventional reinforced concrete (RC) and steel fiber-reinforced concrete (SFRC) precast tunnel lining segments fabricated for a subway tunnel in Canada were investigated. Precast concrete tunnel lining (PCTL) segment specimens were subjected to mid-span load on their intrados faces. Such loading can be induced as a result of vehicular accidents inside the tunnel and/or soil settlement underneath the PCTL segments. Moreover, a punching test was conducted to replicate the expansion of rocks or other geotechnical surrounding conditions above or underneath the tunnel segments. The experimental results showed that the peak load carrying capacity of the RC segments was higher than that of the SFRC segments for both the settlement and punching behavior. However, SFRC segments exhibited higher initial cracking load, more stable post-peak cracking pattern compared to that of the RC segments and significant reduction in crack width. This makes SFRC attractive for the fabrication of segmental tunnel linings where the initial cracking is a governing criterion. Furthermore, it was confirmed that both the tested RC and SFRC PCTL segments satisfied common settlement and punching loads design criteria.
ABSTRACT Tunnels play a key role in facilitating the movement of people, goods, and services. The... more ABSTRACT Tunnels play a key role in facilitating the movement of people, goods, and services. The functionality of tunnels depends on the structural and durability performance of its lining system. Tunnel lining systems act as lines of defense against large overburden loads and complex geotechnical surrounding conditions. In this study, the structural behavior of precast concrete tunnel lining (PCTL) segments from a subway extension tunnel project in Canada was investigated. Flexural monotonic and cyclic load tests were performed on full-scale conventional reinforced concrete (RC) and steel fiber-reinforced concrete (SFRC) PCTL segments to evaluate their bending resistance. Moreover, a thrust load test was conducted to simulate the thrust loading action during tunnel boring machine operation. As expected, flexural test results indicate that the peak load-carrying capacity of RC segments was higher than that of the SFRC segments. However, SFRC segments exhibited higher cracking load and more stable post-peak cracking behavior compared to that of RC segments. RC and SFRC segments exhibited similar behavior during thrust load tests. Both types of segments satisfied the design flexural capacity and thrust loading criteria for monotonic and cyclic loads. The SFRC crack control capability supports its potential as an alternative for conventional RC tunneling segments.
ABSTRACT Steel corrosion induces distress in concrete structures, resulting in the cracking and s... more ABSTRACT Steel corrosion induces distress in concrete structures, resulting in the cracking and spalling of the concrete cover, which accelerates further damage. Chloride ions (Cl–) and carbonation are the primary causes of steel corrosion in concrete. This study investigates the effects of Cl– in precast concrete tunnel lining (PCTL) segments through conducting various tests on cylindrical cores extracted from conventional reinforced concrete (RC) and steel fiber-reinforced concrete (SFRC) segments. The full-scale PCTL segments were fabricated and cured at an industrial precast plant. Experimental results show that the external specimens (extrados and intrados faces) of both the RC and SFRC PCTL segments exhibited lower Cl– penetration due to surface treatment using a cement slurry. The Cl– diffusion coefficient was a function of the exposure period and concentration of the salt solution for both the RC and SFRC segments. SFRC PCTL segments better resisted the ingress of Cl– than control RC segments due to a barrier effect induced by steel fibers (SF), which helped inhibiting the penetration of Cl– into the hardened concrete. This study demonstrates the potential of SFRC as a more durable alternative for precast segmental tunnel linings compared to conventional RC.
Considering its superior engineering properties, ultrahigh performance concrete (UHPC) has emerge... more Considering its superior engineering properties, ultrahigh performance concrete (UHPC) has emerged as a strong contender to replace normal strength concrete (NSC) in diverse construction applications. While the mechanical properties of UHPC have been thoroughly explored, there is still dearth of studies that quantify the durability of UHPC, especially for sustainable mixtures made with local materials. Therefore, this research aims at investigating the alkali-silica reactivity (ASR) potential in sustainable UHPC in comparison with that of NSC. Sustainable UHPC mixtures were prepared using waste untreated coal ash (CA), raw slag (RS), and locally produced steel fibers. UHPC and benchmark NSC specimens were cast for assessing the compressive strength, flexural strength, and ASR expansion. Specimens were exposed to two curing regimes: accelerated ASR conditions (as per ASTM C1260) and normal water curing. UHPC specimens incorporating RS achieved higher compressive and flexural strength...
Ultrahigh-performance concrete (UHPC) is a novel material demonstrating superior mechanical, dura... more Ultrahigh-performance concrete (UHPC) is a novel material demonstrating superior mechanical, durability and sustainability performance. However, its implementation in massive structures is hampered by its high initial cost and the lack of stakeholders’ confidence, especially in developing countries. Therefore, the present study explores, for the first time, a novel application of UHPC, incorporating hybrid steel fibers in precast tunnel lining segments. Reduced scale curved tunnel lining segments were cast using UHPC incorporating hybrid 8 mm and 16 mm steel fibers at dosages of 1%, 2% and 3% by mixture volume. Flexural and thrust load tests were conducted to investigate the mechanical behavior of UHPC tunnel lining segments thus produced. It was observed that the flow of UHPC mixtures decreased due to steel fibers addition, yet steel fibers increased the mechanical and durability properties. Flexural tests on lining segments showed that both the strain hardening (multiple cracking)...
Spin casting is the oldest method of manufacturing precast concrete pipes among all existing meth... more Spin casting is the oldest method of manufacturing precast concrete pipes among all existing methods. While improved concrete mixtures incorporating fibers for other methods of concrete pipe manufacturing, such as the vibration method and roller compaction method, have been developed, no such concrete mixture has yet been developed for spun-cast concrete pipes. This study was designed to explore the possibility of incorporating locally manufactured steel fibers and commercially available polypropylene fibers to develop an improved concrete mixture for use in the manufacturing of full-scale spun-cast concrete pipes. The used steel fibers were of two types, i.e., straight and bundled steel fibers, manufactured by cutting locally available long straight and bundled steel wires, respectively. Various dosages of steel fibers (i.e., 20, 30, 40, and 50 kg/m3) and polypropylene fibers (i.e., 5, 10, 15, and 20 kg/m3) were used in mono and hybrid (steel and polypropylene) forms. The propertie...
In this study, the durability of cement-based repairs was observed, especially at the interface o... more In this study, the durability of cement-based repairs was observed, especially at the interface of debonding initiation and propagation between the substrate–overlay of thin-bonded cement-based material, using monotonic tests experimentally and numerically. Overlay or repair material (OM) is a cement-based mortar with the addition of metallic fibres (30 kg/m3) and rubber particles (30% as a replacement for sand), while the substrate is a plain mortar without any addition, known as control. Direct tension tests were conducted on OM in order to obtain the relationship between residual stress-crack openings (σ-w law). Similarly, tensile tests were conducted on the substrate–overlay interface to draw the relationship between residual stress and opening of the substrate–overlay interface. Three-point monotonic bending tests were performed on the composite beam of the substrate–overlay in order to observe the structural response of the repaired beam. The digital image correlation (DIC) me...
The continuous development of the marble industry has led to an increase in the accumulation of w... more The continuous development of the marble industry has led to an increase in the accumulation of waste marble sludge causing landfilling and health-associated issues. The intention of the current study is to explore the potential of waste marble sludge powder (MS) utilization as a means of controlling alkali-silica reaction (ASR) in concrete. Specimen (cubes, prisms, and mortar bars) were prepared to incorporate reactive aggregates and various proportions of MS ranging from 5% to 40% as a replacement for aggregates. Expansion and mechanical strength characteristics were determined to investigate the effectiveness of MS to control ASRfor up to 150 days. Results revealed that on replacing aggregates in the control specimen with 25% MS, the ASR expansion at 14 days reduced from 0.23% to 0.17%, and the expansion at 28 days reduced from 0.28% to 0.17% which is within limits as per American Standard for Testing of Materials (ASTM) C1260. Furthermore, specimens incorporating MS exhibited im...
Although the disposal of waste ashes causes environmental hazards, recycling them helps in reduci... more Although the disposal of waste ashes causes environmental hazards, recycling them helps in reducing their harmful impacts and improves the characteristics of building materials. The present study explores the possible use of locally available waste ashes including Rice husk ash (RHA)and Silica Fumes (SF) as a partial replacement for cement in concrete to counter the negative impact of alkali-silica reactions (ASRs). In the present study, ternary blends including RHA (0–30%), SF (5% and 10%) and Portland cement were investigated. The amorphous behavior of RHA and SF was confirmed by conducting an X-ray diffraction analysis. A petrography analysis was carried out to ensure the reactive nature of aggregates used to prepare the concrete specimen. Accelerated mortar bar tests were performed in accordance with ASTM C 1260 for up to 90 days. It was revealed that specimens incorporating a ternary blend of SF, RHA, and Portland cement exhibited less expansion compared to the control specimen...
Each year, about 730 million tons of bottom ash is generated in coal fired power plants worldwide... more Each year, about 730 million tons of bottom ash is generated in coal fired power plants worldwide. This by-product can be used as partial replacement for Portland cement, favoring resource conservation and sustainability. Substantial research has explored treated and processed coal bottom ash (CBA) for possible use in the construction industry. The present research explores using local untreated and raw CBA in mitigating the alkali–silica reaction (ASR) of reactive aggregates in concrete. Mortar bar specimens incorporating various proportions of untreated CBA were tested in accordance with ASTM C1260 up to 150 days. Strength activity index (SAI) and thermal analysis were used to assess the pozzolanic activity of CBA. Specimens incorporating 20% CBA achieved SAI greater than 75%, indicating pozzolanic activity. Mixtures incorporating CBA had decreased ASR expansion. Incorporating 20% CBA in mixtures yielded 28-day ASR expansion of less than the ASTM C1260 limit value of 0.20%. Scanni...
Exponential development of post-yield strain (Ԑpost) is a pivotal indicator of failure in embankm... more Exponential development of post-yield strain (Ԑpost) is a pivotal indicator of failure in embankments constructed on soft saturated clays. This paper characterizes saturated clay stratum comprising very soft to very stiff stratigraphy, with plasticity index (PI) ranging from 19% to 31%, by performing widely used geotechnical engineering tests, i.e., the prebored pressuremeter (PMT) test, the triaxial (TXL) test, and constant-rate-of-strain (CRS) consolidation. PMT, TXL, and CRS tests were performed at a strain rate range of 0.18%/min to 0.21%/min to explore the yield stress (σ′y), the pre-yield strain (Ԑpre), and the post-yield strain (Ԑpost). Results indicate that Ԑpost/Ԑpre for PMT, TXL, and CRS stress–strain curves range from 2.7 to 19 in the loading phase and 2 to 21 in the unloading phase. An exponential increase in Ԑpost/Ԑpre is observed in the range of 10 to 21 for very soft to soft clay which is congruent with the realistic sustainable range of 4 to 30 for embankment failure...
Pakistan Journal of Engineering and Applied Sciences, 2016
Self compacting concrete (SCC) is a type of concrete which can flow and spread through reinforcem... more Self compacting concrete (SCC) is a type of concrete which can flow and spread through reinforcement and narrow sections which fills the empty spaces completely without any mechanical vibration. This type of concrete requires large quantity of powder, for which either fine pozzolanic (e.g. fly ash, ground granulated blast furnace slag and silica fume etc) or non-pozzolanic additions (crushed limestone or sand stone etc) are used. The composition of this blend of cement and filler material is significant in SCC, as high amount of cement with lower water content may cause autogenous shrinkage. Therefore, the use of non-pozzolans material with cement needs to be investigated. The concrete industry is among the largest consumer of raw materials. Limestone fillers are generally used in concrete. As marble stone is of limestone origin i.e. marble is formed by metamorphism of limestone. The effect of addition of non-pozzolans powder waste from marble industry is studied for its suitability...
Pakistan Journal of Engineering and Applied Sciences, 2016
Nondestructive evaluation of existing structures is a vital part and an active area of research i... more Nondestructive evaluation of existing structures is a vital part and an active area of research in civil engineering industry. Whenever modifications in a structure or its use are proposed the process begins with the evaluation of existing condition. Rebound hammer (RH) and ultrasonic pulse velocity (UPV) tests are the two readily available and easy-to-perform methods that are widely used in the industry. Current research work is focused on evaluation of an eight years old, half-built reinforced concrete building. The objective was to gather information to decide about the future construction and use. The study concludes that concrete is of reasonable quality and building is appropriate for future construction and use. However, one column in the basement has very poor quality concrete and needs strengthening. Paper also provides a comparison of existing regression models for the prediction of concrete strength based on RH and UPV test data.
Prestressed concrete girders are the main superstructure elements in many bridge structures. Shea... more Prestressed concrete girders are the main superstructure elements in many bridge structures. Shear failures in these girders are undesirable due to brittle failure and little warning time. To prevent shear controlled brittle failure, it is normal practice to increase the amount of transverse reinforcement in flexural members. However, past studies have revealed that even higher transverse reinforcement ratios (i.e. > 4%) may not be able to eliminate shear failure in some cases. Moreover, the increased reinforcement makes it more difficult to place and consolidate the concrete. This research program aimed to investigate the feasibility of replacing traditional shear reinforcement in prestressed concrete beams with steel fibers. A total of 14 rectangular and 8 I-shaped prestressed concrete beams were investigated after subjecting them to two-point loading test. The beams were casted with steel fiber ratios ranging from 0.75% to 2.00%. Experimental results revealed that the inclusio...
Pakistan has vast potential of concrete aggregates due to having numerous mountainous ranges. How... more Pakistan has vast potential of concrete aggregates due to having numerous mountainous ranges. However, the properties of these aggregates are yet to be explored as scant research has been carried out in this area. In this study, an experimental approach was adopted to compare the engineering properties of widely used coarse aggregates in Pakistan. Aggregate samples were gathered from four various quarries in accordance with ASTM sampling procedure and their physical as well as mechanical properties were evaluated through laboratory testing according to ASTM and BS standards. Tests were performed on Margalla, Sargodha, Barnalla and Mangla crushes. Different concrete specimens were also prepared using the above mentioned aggregates and tested for their mechanical properties (compressive, tensile and flexural strengths). Test results revealed that the aggregates from evaluated quarries are suitable to be used in concrete. Each sample of aggregates have different characteristics which i...
Pakistan Journal of Engineering and Applied Sciences, 2017
Pakistan is currently facing massive energy crisis and requiring huge investment into the power t... more Pakistan is currently facing massive energy crisis and requiring huge investment into the power transmission line infrastructure. The longest transmission lines of the country are of 220 kV lines stretching up to 7359 km. The contemporary factored design wind load effects for overhead lattice transmission line tower are evaluated based on the applicable wind load factor, gust response factor and design wind speed as recommended by WAPDA/IEC Specifications (1988), ASCE-74 (1991) and ASCE-7 (2005). The current factors and design wind speed were developed considering linear elastic responses. However, information on the non-linear inelastic responses of such towers under dynamic wind loading and on the structural capacity of towers in relation to the design capacities is lacking. The knowledge and assessment of the capacity curve and its relation to the design strength is important to evaluate the integrity and reliability of these towers. Therefore, in this study, analysis was perform...
ABSTRACT Ultra-high performance concrete (UHPC) is a new generation of steel fiber-reinforced con... more ABSTRACT Ultra-high performance concrete (UHPC) is a new generation of steel fiber-reinforced concrete with superior mechanical and durability properties. However, limited data is available on the influence of the steel fiber length and dosage on UHPC mechanical and durability performance. Therefore, in this study, a number of UHPC mixtures with varying steel fiber lengths (8 mm (0.31 in), 12 mm (0.47 in) and 16 mm (0.62 in)) and dosages (1%, 3% and 6%) by mixture volume were tested. Mechanical properties of UHPC including compressive, splitting tensile and flexural strengths were assessed. Moreover, its resistance to chloride ions penetration and mechanical degradation under various chloride exposures (i.e. 3.5% and 10%) were evaluated. Results showed an increase in mechanical properties as the fiber dosage increased. UHPC mixtures incorporating short steel fibers exhibited enhanced flexural properties compared to that of mixtures with similar volume of longer steel fibers. At higher fiber dosage, UHPC mixtures exhibited relatively improved durability. Moreover, no degradation in UHPC mechanical properties was observed after exposure to various chloride ions solutions.
ABSTRACT The overall stability of a segmental tunnel lining ring is highly dependent on the struc... more ABSTRACT The overall stability of a segmental tunnel lining ring is highly dependent on the structural integrity of its individual precast segments, which provide protection against the surrounding exposure conditions. In this study, the settlement and punching behavior of full-scale conventional reinforced concrete (RC) and steel fiber-reinforced concrete (SFRC) precast tunnel lining segments fabricated for a subway tunnel in Canada were investigated. Precast concrete tunnel lining (PCTL) segment specimens were subjected to mid-span load on their intrados faces. Such loading can be induced as a result of vehicular accidents inside the tunnel and/or soil settlement underneath the PCTL segments. Moreover, a punching test was conducted to replicate the expansion of rocks or other geotechnical surrounding conditions above or underneath the tunnel segments. The experimental results showed that the peak load carrying capacity of the RC segments was higher than that of the SFRC segments for both the settlement and punching behavior. However, SFRC segments exhibited higher initial cracking load, more stable post-peak cracking pattern compared to that of the RC segments and significant reduction in crack width. This makes SFRC attractive for the fabrication of segmental tunnel linings where the initial cracking is a governing criterion. Furthermore, it was confirmed that both the tested RC and SFRC PCTL segments satisfied common settlement and punching loads design criteria.
ABSTRACT Tunnels play a key role in facilitating the movement of people, goods, and services. The... more ABSTRACT Tunnels play a key role in facilitating the movement of people, goods, and services. The functionality of tunnels depends on the structural and durability performance of its lining system. Tunnel lining systems act as lines of defense against large overburden loads and complex geotechnical surrounding conditions. In this study, the structural behavior of precast concrete tunnel lining (PCTL) segments from a subway extension tunnel project in Canada was investigated. Flexural monotonic and cyclic load tests were performed on full-scale conventional reinforced concrete (RC) and steel fiber-reinforced concrete (SFRC) PCTL segments to evaluate their bending resistance. Moreover, a thrust load test was conducted to simulate the thrust loading action during tunnel boring machine operation. As expected, flexural test results indicate that the peak load-carrying capacity of RC segments was higher than that of the SFRC segments. However, SFRC segments exhibited higher cracking load and more stable post-peak cracking behavior compared to that of RC segments. RC and SFRC segments exhibited similar behavior during thrust load tests. Both types of segments satisfied the design flexural capacity and thrust loading criteria for monotonic and cyclic loads. The SFRC crack control capability supports its potential as an alternative for conventional RC tunneling segments.
ABSTRACT Steel corrosion induces distress in concrete structures, resulting in the cracking and s... more ABSTRACT Steel corrosion induces distress in concrete structures, resulting in the cracking and spalling of the concrete cover, which accelerates further damage. Chloride ions (Cl–) and carbonation are the primary causes of steel corrosion in concrete. This study investigates the effects of Cl– in precast concrete tunnel lining (PCTL) segments through conducting various tests on cylindrical cores extracted from conventional reinforced concrete (RC) and steel fiber-reinforced concrete (SFRC) segments. The full-scale PCTL segments were fabricated and cured at an industrial precast plant. Experimental results show that the external specimens (extrados and intrados faces) of both the RC and SFRC PCTL segments exhibited lower Cl– penetration due to surface treatment using a cement slurry. The Cl– diffusion coefficient was a function of the exposure period and concentration of the salt solution for both the RC and SFRC segments. SFRC PCTL segments better resisted the ingress of Cl– than control RC segments due to a barrier effect induced by steel fibers (SF), which helped inhibiting the penetration of Cl– into the hardened concrete. This study demonstrates the potential of SFRC as a more durable alternative for precast segmental tunnel linings compared to conventional RC.
Considering its superior engineering properties, ultrahigh performance concrete (UHPC) has emerge... more Considering its superior engineering properties, ultrahigh performance concrete (UHPC) has emerged as a strong contender to replace normal strength concrete (NSC) in diverse construction applications. While the mechanical properties of UHPC have been thoroughly explored, there is still dearth of studies that quantify the durability of UHPC, especially for sustainable mixtures made with local materials. Therefore, this research aims at investigating the alkali-silica reactivity (ASR) potential in sustainable UHPC in comparison with that of NSC. Sustainable UHPC mixtures were prepared using waste untreated coal ash (CA), raw slag (RS), and locally produced steel fibers. UHPC and benchmark NSC specimens were cast for assessing the compressive strength, flexural strength, and ASR expansion. Specimens were exposed to two curing regimes: accelerated ASR conditions (as per ASTM C1260) and normal water curing. UHPC specimens incorporating RS achieved higher compressive and flexural strength...
Ultrahigh-performance concrete (UHPC) is a novel material demonstrating superior mechanical, dura... more Ultrahigh-performance concrete (UHPC) is a novel material demonstrating superior mechanical, durability and sustainability performance. However, its implementation in massive structures is hampered by its high initial cost and the lack of stakeholders’ confidence, especially in developing countries. Therefore, the present study explores, for the first time, a novel application of UHPC, incorporating hybrid steel fibers in precast tunnel lining segments. Reduced scale curved tunnel lining segments were cast using UHPC incorporating hybrid 8 mm and 16 mm steel fibers at dosages of 1%, 2% and 3% by mixture volume. Flexural and thrust load tests were conducted to investigate the mechanical behavior of UHPC tunnel lining segments thus produced. It was observed that the flow of UHPC mixtures decreased due to steel fibers addition, yet steel fibers increased the mechanical and durability properties. Flexural tests on lining segments showed that both the strain hardening (multiple cracking)...
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