Search

The research work presented in this manuscript focused on the comparative examination of the influence of the Compression Casting Technique (CCT) and the conventional casting method (i.e., compaction through vibration) on the performance of 100% Recycled Aggregate Concrete (RAC). The minimum target compressive strength of 100% RAC was 15 MPa keeping in view its application in the manufacturing of load-bearing concrete masonry units. A total of 28 concrete compositions were prepared by varying the coarse to fine aggregates ratio (i.e., 70:30 and 60:40), cement content (10% and 15%) by weight of total aggregates, casting technique, and applied pressure for compression casting (i.e., 25, 35, and 45 MPa). The concrete compositions were tested to determine their density, compressive strength, Elastic Modulus (EM), and Ultrasonic Pulse Velocity (UPV). For comparison, samples of Natural Aggregate Concrete (NAC) were also tested for the same properties. The results highlighted the positive impact of CCT on the properties of 100% RAC. The compressive strength and EM of fully RAC was increased by 20–80% and 15–50%, respectively, by changing casting method from vibration to CCT. At casting pressure of 35 MPa and 15% cement, compressed 100% RAC exhibited compressive strength higher than vibrated NAC. The UPV value exhibited by 100% RAC was increased by changing the casting technique. The analytical models were proposed using regression analysis of experimental results to predict compressive strength and EM of compressed 100% RAC and NAC. These proposed models were evaluated using statistical parameters, i.e., average absolute error (AAE) and mean (M) and found to be able to predict the compressive strength and EM of RAC with reasonable accuracy as compared to the analytical models already existing in the literature. This study finally concluded that through CCT, 100% RAC with low cement content could achieve minimum target compressive strength of 15 MPa. The development and use of compressed load-bearing 100% RAC construction units would help to achieve sustainability in construction.

The alkali–silica reaction (ASR) is a primary cause for premature concrete degradation. An accelerated mortar bar test is often used to access the detrimental phenomena in concrete caused by the ASR of aggregates. However, this test requires a certain environmental conditioning as per ASTM C1260. The objective of this study is to explore the effects of the cement alkali content, exposure solution concentration, temperature, and test duration on mortar bar expansion. Factorial experimental design and analysis was conducted to delineate the effects of the individual factors as well as their interaction. Five different aggregates with various mineralogical properties were used, representing reactive and non-reactive aggregates. Various dosages of cement alkalis (0.40, 0.80, and 1.20 Na2Oe), sodium hydroxide (NaOH) solution concentrations (0.5, 1.0, and 1.5 N), and temperature (40 °C, 80 °C, and 100 °C) were the studied variables. Mortar bar expansion was measured at 3, 7, 14, 21, 28, 56, and 90 days. Mortar bars incorporating Jhelum aggregates incurred expansion of 0.32% at 28 days, proving to be reactive aggregates as per ASTM C1260. Similarly, specimens incorporating Taxila aggregates showed expansion of 0.10% at 28 days, indicating non-reactive nature. It was observed that specimens with Sargodha aggregates showed expansion of 0.27% at 28 days for 0.50 N NaOH solution concentration compared to 0.31% expansion for identical specimens exposed to 1.5 N solution. Moreover, expansion increased with exposure duration for all the tested specimens. Experimental results showed that the cement alkali contents had relatively lesser effect on expansion for 1.0 N NaOH; while, in the case of 0.5 N and 1.5 N NaOH, the cement alkali had a significant effect. It was noted that expansion increased with an increase in the temperature. Jhelum aggregates showed 28-day expansion of 0.290% when exposed to 40 °C, but at a temperature of 100 °C, expansion increased to 0.339%. Factorial analysis revealed that the exposure solution had a major contribution towards the expansion of mortar bar specimens. This study highlights the contribution of various exposure conditions on the ASR expansion, which leads to a decisive role in selecting the aggregate sources for various applications and exposure conditions leading to sustainable construction.

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 properties in the fresh state and mechanical properties of the test mixtures were investigated. Full-scale spun-cast concrete pipes having a 450 mm internal diameter were manufactured and tested using the three-edge bearing test. The compressive strength of the mixtures was largely insensitive to the dosage of the fibers. The splitting tensile strength of all fiber-reinforced concrete mixtures was higher than that of the reference mixture without fibers, with a 24% increase recorded for the concrete mixture incorporating 50 kg/m3 of bundled steel fibers relative to the reference mixture with no fibers. The flexural performance of the fiber-reinforced concrete mixtures was superior to that of the reference mixture without fibers in terms of flexural strength, toughness, residual strength, and crack control, with up to 28% higher flexural strength relative to the reference mixture without fibers. The three-edge bearing tests on full-scale spun-cast pipes incorporating steel fibers showed that the use of fibers is a promising alternative to the traditional steel cage in spun-cast concrete pipes.

Due to the production of industrial slags in massive amounts, there is a high demand for recycling these slags and avoiding their dumping in landfills. This article aims to recycle industrial slags in brick manufacturing and investigates the performance of fired clay bricks incorporating different kinds of industrial slags such as granulated blast furnace slag (GBS), ferrochromium slag (FCS), and steel slag (STS). For this purpose, two different dosages of slags (i.e., 10 and 20 wt % of clay) and two different firing temperatures (i.e., 1000 and 1100 oC) were considered. Various physical, mechanical, and durability tests were performed to evaluate the properties of bricks incorporating industrial slags. Results show that the compressive strength of the bricks incorporating industrial slags are well above the minimum compressive strength limits of bricks as per different building standards. The bricks incorporating industrial slag can be classified as load-bearing bricks for structural applications in accordance with the ASTM C469 standard. An increase in the porosity of bricks is observed with the addition of STS. However, reduced porosity is observed for bricks incorporating FCS and GBS than traditional bricks. Based on the water absorption and efflorescence test results, bricks incorporating industrial slags can be used as severe weather resistant bricks following ASTM C62 standard and slight efflorescence bricks per ASTM C67 standard. The amounts of heavy metals in the leachates of bricks are observed below the specified limits of the Environment Protection Authority. SEM images and EDS analysis of bricks are also supporting the results of this study. Based on the results, utilizing industrial slags in brick manufacturing can help recycle the abundant industrial wastes and develop the fired clay bricks with desired properties.

The focus of this study was to develop manually compressed interlocking mud bricks and study their compressive strength. For this purpose, mud bricks were manufactured incorporating wheat straw (1–4% by weight of soil) and rice husk (1–5% by weight of soil). Furthermore, mud bricks were also manufactured using lime (12%, 15% and 19% by weight of soil) and a combination of wheat straw and rice husk, named straw husk (1–4% by weight of soil) as an additive. To investigate the strength and failure pattern of interlocking mud bricks, compressive strength testing was performed. The control mud bricks showed shrinkage cracks, but no signs of shrinkage cracking were observed in specimens incorporating fibres (wheat straw, rice husk and straw husk). A decrease in compressive strength was observed with increasing content of fibres in the mud brick specimens. However, interlocking mud bricks incorporating fibres fulfilled the minimum strength requirements of different standards for mud bricks. A decrease in compressive strength of the mud bricks was also observed when using lime as an additive. Nevertheless, interlocking mud bricks incorporating lime (up to 19%) satisfied the minimum strength requirement of the Turkish standard. Therefore, interlocking mud bricks incorporating fibres and lime can be used in earthen construction, leading towards sustainable structures.

In this research study, environmentally friendly unburnt coal ash (CA) bricks were investigated as an alternative to conventional burnt clay bricks. In this research study, various physical and mechanical properties of unburnt CA bricks were investigated. The unburnt CA bricks were prepared by using 60% CA and 10% lime by weight. In these unburnt CA bricks, varying cement contents (5%, 10%, and 15%), sand contents (10% and 15%), and quarry dust contents (5% and 10%) by weight were used. A forming pressure of 29 MPa was applied through an automatic pressure control system either for 3 s or 6 s. The prepared bricks were moist cured for 28 days. The experimental results exhibited that unburnt CA bricks with 10% cement, 10% sand, and 10% quarry dust subjected to forming pressure for 3 s exhibited the highest compressive strength of 19 MPa and flexural strength of 2.1 MPa. The unburnt CA bricks exhibited reduced water absorption, reduced efflorescence, and lower weight per unit area than the conventional clay bricks. A cost comparison of unburnt CA bricks and clay bricks exhibited that unburnt CA bricks are cost-effective compared to clay bricks.

Raising of the Mangla Dam in Pakistan submerged about 15,780 acres of land, resulting in the relocation of 8020 inhabitants to a newly developed town named New City. The new site, consisting of 1300 acres, is in the sub-tropical zone and comprises badland topography. The parent soils (Siwalik clay) pose infrastructure serviceability issues, causing immense loss to property. The study aims to improve the properties of Siwalik clay (base soil) using industrial wastes like marble and glass powders (5 to 20%) and polypropylene fibers (0.25 to 1.25%) as modifiers. Laboratory tests including grain size distribution, Atterberg limits, standard Proctor compaction, unconfined compression, indirect tensile strength, swell potential, and California bearing ratio were conducted on the control and modified clay samples. The results showed that unconfined compressive strength (UCS) and swelling strains (SS) were increased by 43% and 8% at 1.57 kPa pressure with 15% replacement of marble powder. However, the addition of the 20% glass powder and 0.5% polypropylene fibers not only improved UCS by 110% and 39%, but also reduced SS by 27% and 86%, respectively. The capital construction cost of 1 km long road with modified subgrade using 15% glass powder was reduced by 16% whereas it increased for marble powder and polypropylene fibers by 22% and 17%, respectively. All modifiers had very low hazard to adjoining aqueous environment. Conclusively, glass powder and polypropylene fibers can be used as environmentally-friendly soil improvement modifiers, leading towards sustainable solutions of the serviceability problems.

Diamer Basha dam is to be located on the mighty Indus River about 315 km upstream of Tarbela dam. The dam will be 272 m high and constructed from roller-compacted concrete (RCC). Earlier studies for the RCC mixture and placement conditions regarding heat development showed that extensive use of cement substitutes is essential for the construction of the RCC dam. The total amount of cementitious substitutes will be up to 2·0 Mt, which need to be supplied over a period of 4·5–5 years. Potential substitutes (blast-furnace slag from Pakistan Steel Mills, Karachi and fly ash from Lakhra, Pakistan and Bathinda, India) were considered unfeasible due to low production capacities, long distances from the project site and political reasons. In this study, locally available potential pozzolanic materials from Gini Gah, about 54 km upstream of the dam site, were investigated through physical, chemical and pozzolanic activity tests to assess their suitability for use in mass concrete. The results revealed that glacial moraines obtained from Gini are acceptable for use in RCC.

Application of recycled aggregate concrete (RAC) in the concrete structures is very limited due to inferior performance. Moreover, design of concrete structures ignores the role of transverse reinforcement in the strength enhancement of compression members. This study aims to utilize pre-existing transverse reinforcement to improve the performance of RAC. For this purpose, spirally confined concrete specimens were examined under axial compression, with the variation of three recycled aggregates (RA) replacement ratios (i.e., 0, 50 and 100%) and three pitches of spiral reinforcement (i.e., 20, 30 and 40 mm). The results show that increase of RA will cause a reduction of peak strength and peak strain. However, improved strength and ductility of RAC are observed with the increase in confinement pressure. A comparative study of the existing models for stress-strain behavior of steel confined normal aggregate concrete (NAC) with the test results indicates that the stress-strain characteristics of steel confined RAC cannot be well predicted using these existing models. Based on the test results, a model is developed in this work by modifying the parameters of best performing stress-strain model for steel confined NAC to incorporate the influence of RA replacement ratio. The proposed model can estimate the stress-strain characteristics of both NAC and RAC confined by steel spiral, which may be helpful in designing the sustainable RAC compression members. Moreover, an equation is presented to estimate the amount of RA for the given confinement level which can be recycled without compromising the design strength of spirally confined concrete compression members.

This study aims to investigate the axial stress-strain behavior of macro-synthetic fiber reinforced recycled aggregate concrete. Concrete cylinders reinforced with macro-synthetic fibers were tested under axial compression, with the variation of three different replacement ratios of recycled aggregates (i.e., 0, 50 and 100%) and three different dosages of macro polypropylene fibers (i.e., 0, 0.5 and 1% of volume of recycled aggregate concrete). A comparative study of the existing stress-strain models for steel fiber reinforced normal and recycled aggregate concrete with the test results indicates that the stress-strain behavior of steel fiber reinforced normal and recycled aggregate concrete can be well predicted by these existing models. No stress-strain model for macro-synthetic fiber reinforced normal and recycled aggregate concrete has been developed. Based on the test results, a stress-strain model is developed in this work by modifying the parameters of best performing stress-strain model for steel fiber reinforced normal aggregate concrete. The proposed model can effectively predict the stress-strain behavior of both steel and macro-synthetic fiber reinforced normal and recycled aggregate concrete. Test results show that the peak stress, peak strain and ultimate strain of concrete specimens increase with the increase in fiber dosage and the addition of fibers has a better effect on recycled aggregate concrete and as compared to normal aggregate concrete.

The addition of macro-polypropylene fibres improves the stress-strain performance of natural aggregate concrete (NAC). However, limited studies focus on the stress-strain performance of macro-polypropylene fibre-reinforced recycled aggregate concrete (RAC). Considering the variability of coarse recycled aggregates (CRA), more studies are needed to investigate the stress-strain performance of macro-polypropylene fibre-reinforced RAC. In this study, a new type of 48 mm long BarChip macro-polypropylene fibre with a continuously embossed surface texture is used to produce BarChip fibre-reinforced NAC (BFNAC) and RAC (BFRAC). The stress-strain performance of BFNAC and BFRAC is studied for varying dosages of BarChip fibres. Results show that the increase in energy dissipation capacity (i.e., area under the curve), peak stress, and peak strain of samples is observed with an increase in fibre dosage, indicating the positive effect of fibre addition on the stress-strain performance of concrete. The strength enhancement due to the addition of fibres is higher for BFRAC samples than BFNAC samples. The reduction in peak stress, ultimate strain, toughness and specific toughness of concrete samples due to the utilisation of CRA also reduces with the addition of fibres. Hence, the negative effect of CRA on the properties of concrete samples can be minimised by adding BarChip macro-polypropylene fibres. The applicability of the stress-strain model previously developed for macro-synthetic and steel fibre-reinforced NAC and RAC to BFNAC and BFRAC is also examined.

Self-compacting concrete (SCC) incorporating secondary raw materials has been extensively used around the globe due to its improved fresh, mechanical and durability properties. This study was planned to evaluate the suitability of locally available waste alumina powder (AP) and nylon textile fibers (NF) as a partial replacement for fine and coarse aggregates with the ultimate goal to locally produce SCC with desired properties. The used AP was acquired from a local market and NF was collected from a local textile factory. Various dosages of AP (10%, 20%, 30%, 40% and 50% by volume of fine aggregates) and NF (1% and 2% by volume of coarse aggregates) were studied. Tests including slump flow, V-funnel and J-ring tests were performed for examining the fresh properties of developed SCC. Results showed that the addition of AP has an insignificant effect on the superplasticizer dosage for maintaining a constant flow of 70 cm. However, a higher dosage of superplasticizer was required for a mixture with increasing dosages of NF to sustain a constant flow. Similarly, slump flow time (for a spread of 50 cm) and V-funnel time increased for mixtures with higher dosages of AP and NF. Tested SCC mixtures incorporating 40% and 50% of AP with 1% and 2% of NF showed an extreme blocking assessment due to their increased interparticle friction, the higher water absorption capacity of used AP and NF leading to increased flow resistance and hence, showed lower passing ability. The compressive strength was 16% higher for specimens incorporating 40% of AP due to the filling effect of AP which fills the micro-pores, leading to a more dense and compact internal micro-structure, confirmed through scanning electron microscopy analysis. An ultrasonic pulse velocity test conducted on hardened specimens verified the findings of the compressive strength results. Moreover, it was observed that NF has an insignificant effect on the compressive strength; however, flexural strength was increased due to the incorporation of NF, especially at higher dosages of AP.

Recently, foam concrete (FC) has been widely considered due to higher workability, lightweight, lower cost, thermal and fire resistance relatively to conventional concrete. This study intends to measure the properties of FC incorporating bottom ash (BA) as fine aggregates (FA) and polypropylene fibers (PPF). A total of 18 concrete mixes were produced with two cement contents: 300 and 400 kg/m3. In addition, three foam agent contents (40, 50, and 60 kg/m3) and three PPF contents (0, 0.5, and 1% in terms of volume) were used and considered to investigate the physical, mechanical, thermal, and durability properties of PPF-reinforced FC incorporating BA. Furthermore, the effect of elevated temperature on the properties of specimens was also examined. Results show an increase in apparent porosity, water absorption, and sorptivity of FC with the increase in foam agent content. Conversely, a reduction in thermal conductivity, porosity, and shrinkage is observed with an increase in foam agent, cement, and PPF contents, respectively. The rise in foam agent content declines the mass loss while improves both compressive and flexural strengths of FC under an elevated temperature. Scanning electron microscopic (SEM) analysis of the FC specimens after exposure to the elevated temperature shows the cracks and inter-connected pores due to the thermal stresses by decomposing calcium silicate phases. Results show that all the FC mixes incorporating BA as FA and PPF can be used as moderate-strength concrete following American Concrete Institute guidelines, leading to enhanced FC performance and sustainable construction.

Due to rapid population growth and industrialization, the generation of different industrial and agricultural wastes has surged in the past few decades. In this study, burnt clay bricks are prepared to investigate the synergistic and individual effect of glass sludge (GS), marble sludge (MS), and rice husk (RH) on the physical, mechanical, durability, and thermal properties of brick samples. Results show that the addition of waste materials (GS, MS, and RH) reduces the shrinkage, weight per unit area, and thermal conductivity of brick samples. All the brick samples incorporating different waste materials show efflorescence much lower than 10%. Furthermore, no brick sample faced any cracking even after 50 freeze-thaw cycles. The mass loss of brick samples incorporating 25% of GS is observed lower than the specified limit of ASTM C67 and are classified as freeze-thaw resistant brick samples. All the brick samples incorporating different waste materials satisfy the minimum compressive strength and modulus of rupture requirements for building bricks and can be used in a moderate weather-resistant environment, leading to sustainable masonry construction. Furthermore, all the brick samples show leaching toxicity values much lower than the specified limits of the Environmental Protection Agency . The scanning electron microscopic images also support the results of porosity and water absorption of brick samples observed in this study. Based on the results, all the combinations of waste materials considered in this study for making brick samples can be used for masonry construction leading towards landfill reduction and the production of eco-friendly bricks.

The global generation of millions of tonnes of water treatment sludge (WTS) per day is triggering waste management problems and the up-cycling of WTS in masonry bricks is an eco-friendly solution. Effect of different dosages of WTS on the performance of clay bricks has been studied by researchers. Scant work is available regarding the performance of no-clay bricks i.e. bricks made exclusively with the WTS. This study aims to investigate the engineering performance of no-clay bricks having WTS, glass, and marble wastes. For this reason, WTS bricks are manufactured with different dosages of glass and marble wastes (i.e. 0–15%). Mechanical, durability, thermal, and microstructural performance of all the brick specimens is explored. X-ray fluorescence results show that the collective amount of fluxing agents in WTS exceeds 9% (similar to low refractive clay). All the bricks manufactured in this study exhibited water absorption between 5.3 and 12.6% and can be classified as first-class and severe weather resistant bricks as per ASTM C373-18 and ASTM C62-17, respectively. The thermal conductivity and porosity of no-clay WTS bricks were observed 1.014 W/mK and 11%, respectively. Moreover, the higher compressive strength and bulk density of all the brick specimens fulfill the international building code obligations. Furthermore, no-clay WTS bricks meet the ASTM C902 and ASTM C62-17 requirements for light vehicular traffic and severe weather-resistant bricks, respectively. Empirical relationships between the compressive strength, thermal conductivity, porosity, and density of brick specimens developed in this study can be used to predict the performance of WTS bricks. Therefore, no-clay WTS bricks having glass and marble wastes can be used to produce strong, durable, and sustainable buildings leading towards a cleaner environment and natural clay conservation.

Background: End stage renal disease (ESRD) is a well-recognized risk factor for development of sudden cardiac arrest(SCA). There is limited data on outcomes after an in-hospital SCA event in ESRD patients. Methods: Data were obtained from National Inpatient Sample from January 2007 to December 2017. In-hospital SCA was identified using International Classification of Disease, 9th Revision, Clinical Modification, and International Classification of Disease, 10th Revision, Clinical Modification codes of 99.60, 99.63, and 5A12012. ESRD patients were subsequently identified using codes of 585.6 and N18.6. Propensity -matched analysis using logistic regression with SD caliper of 0.2 was used to match patients with and without ESRD. Crude and propensity-matched (PS) cohorts outcomes were calculated. Results: A total of 1,412,985 patients sustained in-hospital SCA during our study period. ESRD patients with in-hospital SCA were younger and had a higher burden of key co-morbidities. Mortality was similar in ESRD and non-ESRD patients in PS matched cohort (70.4% vs. 70.7%, p = 0.45, figure 1) with an overall downward trend over our study years (figure 2). Conclusion: In the context of in-hospital SCA, mortality is similar in ESRD and non-ESRD patients in adjusted analysis. Adequate risk factor modification could further mitigate the risk of in-hospital SCA among ESRD patients

Introduction: Cardiac Implantable Electronic Device (CIED) infections are a major source of morbidity, mortality and increased healthcare cost. There are several well established risk factors associated with increased infection. An antibiotic coated envelope has been developed as an infection prevention intervention. Hypothesis: Whether antibiotic coated envelope is an effective preventive strategy against Cardiac Implantable Electronic Device Infections. Methods: 6 trials comparing use of antibiotic envelope to control, including 1 randomized trial and 5 cohort studies were selected using PubMed and Embase data bases through May 2019. The efficacy end point was prevention of CIED Infection. Outcomes were combined using random effects model and estimated by odds ratio with 95% confidence intervals (CI). Results: In our analysis of total 12,024 patients undergoing CIED implantation, 5,844 patients received antibiotic envelope while 6,180 patients were included in the control group. Antibiotic envelope was superior to control in reducing the risk of device infection (OR 0.40 CI [0.17-0.95], p=0.04). Conclusions: The use of antibiotic envelope in Cardiac Implantable Electronic Devices (CIED) is associated with reduced incidence of CIED infection.

In order to achieve sustainability in construction industry, recycling of construction and demolition wastes in new concrete is gaining a lot of attention. However, extensive research is needed to explore the complete behavior of resulting recycled aggregate concrete (RAC). This study aims to investigate the fracture behavior, mechanical performance and microstructure of macro-synthetic fiber reinforced RAC. For this purpose, notched beam specimens were produced using three different replacement ratios of recycled concrete aggregates (RCA) (i.e., 0, 50% and 100%) and three different dosages of macro-synthetic fibers (i.e., 0, 0.5% and 1% of volume of RAC). Three-point bending and other mechanical tests were performed to investigate the post peak behavior (residual flexural tensile strength, fracture energy and toughness) and mechanical properties (compressive strength, flexural strength and split tensile strength) of macro-synthetic fiber reinforced normal and RAC. Fracture surface analysis was also performed to develop the empirical relationships between number of fibers and post peak behavior of fiber reinforced RAC. Furthermore, microstructure characteristics of macro-synthetic fiber reinforced normal and RAC were also investigated using scanning electron microscopy (SEM). Results showed that reduction in mechanical properties of concrete was observed with the increase in RCA replacement ratio. However, increase in mechanical properties particularly split tensile strength of normal and RAC was observed with the increase in dosage of macro-synthetic fibers. Concrete specimens also showed increase in residual flexural tensile strengths with the increase in dosage of macro-synthetic fibers. RAC reinforced with 1% dosage of macro-synthetic fibers showed increase in fracture energy and toughness by 380% and 129%, respectively. A strong influence of number of fibers on residual flexural tensile strength and fracture energy of concrete mixtures was observed during the study. Microstructural analysis also showed the existence of bond between mortar paste and macro-synthetic fiber, which improved the mechanical properties and post peak behavior of macro-synthetic fiber reinforced concrete. Based on this study, it can be concluded that macro-synthetic fibers improve the fracture energy and mechanical properties of RAC leading towards higher ductility and better energy dissipation. Moreover, number of fibers strongly influences the residual flexural tensile strength and fracture energy of RAC.

The risk of alkali–silica reaction of concrete aggregates in many parts of the world remains largely unexplored. In particular, a suitable approach for testing aggregates with marginal to moderate alkali–silica reactivity has not been clearly identified. In this study, the mineralogical compositions of aggregates from five different quarries were investigated. Mortar bar expansion for these aggregates was tested as per the guidelines of both C 227 and C 1260. Although the tested aggregate sources proved non-reactive under ASTM C 227 test conditions, ASTM C 260 identified one group of aggregates as potentially reactive. Scanning electron microscopy imaging confirmed that two sources of aggregates were reactive. The compressive and flexural strength test results of aged specimens with reactive aggregates indicated that the strength reduction of those subjected to 1 month of ASTM C 260 exposure was similar to those of specimens under 6 months of ASTM C 227 exposure. Based on the experimental results, it appears that aggregates with potential alkali–silica damage may be characterised as non-reactive if the appropriate test method is not adopted. The findings indicate that the ASTM C 1260 procedure is more effective in determining the reactivity potential of marginally to moderately reactive aggregates.

In this study, the intrinsic properties of recycled coarse aggregates (RC), associated with bonded mortar, were modified with two different pretreatment techniques viz-a-viz HCl pretreatment and Na2SO4 pretreatment, while maintaining a fixed aggregate-to-solution ratio of 1:4.5. The residual bonded mortar was quantified to evaluate the potential of both techniques. HCl pretreatment yielded greater removal of bonded mortar content (BMC), almost twice as high as achieved by Na2SO4 pretreatment. Subsequently, the concretes were developed (termed as recycled aggregate concrete; RAC) by incorporating HCl treated coarse aggregates (HTC) and Na2SO4 treated coarse aggregates (STC). Both natural and recycled (untreated) fine aggregates (NF and RF, respectively) were used. Control specimens with natural coarse aggregates (NC) were prepared for comparative assessment. The resulting properties showed significantly influenced by bonded mortar content (BMC). About 14% higher compressive strength was achieved by using HTC in comparison with untreated RC, while a mere corresponding decline of 5% was seen when compared with NC. Likewise, the carbonation resistance and the resistance to chloride ion penetration showed better performance for HTC and STC incorporated concretes. Such superior performance is attributed to the denser interface (between the aggregate and paste matrix) with reduced pores/voids, as assessed from the optical and scanning electron microscopy. Further, the determined properties were used to develop regression models for the prediction of RAC properties. The prediction equations thus obtained showed remarked precision with the experimentally determined results, and as such these can be used for strength and durability prediction.

Deterioration of concrete structures with time is well understood. One of the major reasons of deterioration is reaction between cement paste and reactive siliceous aggregates which is known as alkali silica reaction (ASR). This article reviews the studies on ASR in concrete. Although a vast literature is available on mechanisms and preventive measures against ASR, however there are still a lot of deficiencies regarding the test methods to detect the ASR potential in concrete. The aim of this article is to discuss different factors affecting ASR, consequences of ASR and different challenges encountered by researchers in the detection of ASR. The study revealed that alkali content of cement, aggregates grading, mineralogical combinations, testing methods and testing conditions are all the challenges, researchers face during evaluation of ASR potential in concrete.

Now-a-days, construction of energy efficient buildings is highly in demand all over the world. The main focus of this study is to utilize waste marble sludge (WMS) in the production of energy efficient burnt clay bricks on industrial scale. For this purpose, WMS was obtained from a local marble industry. Burnt clay bricks were prepared, in an industrial brick kiln under actual field conditions, using various dosages of WMS (i.e., 5 %, 10 %, 15 %, 20 % and 25 % by weight of clay) and were examined for different physico-mechanical and thermal properties. It was observed that lightweight bricks can be manufactured using WMS, which are helpful in reducing the overall construction costs. Although the reduction in compressive strength was observed with WMS incorporation in clay bricks, 15 % replacement level exhibited satisfactory strength requirements. Clay bricks showed increase in apparent porosity and water absorption with increasing WMS content. A porous structure having interconnected and irregular shaped open pores was observed after incorporating WMS in clay bricks, which improved the thermal insulating properties. Brick specimens incorporating up to 15 wt% WMS showed decrease in thermal conductivity by about 16 %. Based on this study, 15 wt% WMS is deemed optimum for the manufacturing of burnt clay bricks leading towards sustainable, economical, environment friendly and energy efficient construction.

This paper investigates the effects of incorporating slag waste (Ground Granulated Blast Furnace Slag; GGBS) as cement replacement in high early strength concrete. GGBS was used in various replacement ratios and resulting properties of the developed concretes were evaluated. Compressive strength, heat of hydration and shrinkage were determined for evaluating hydration attributes while chloride penetrability and carbonation resistance were investigated for studying the durability-related characteristics of the resulting concretes. The optimum ratio of GGBS as SCM has been determined, in this study, as 30% at which there is merely an average strength decline of 11% while reducing the total carbon dioxide emissions by 30%. Similarly, at this replacement level, the decreased chloride ion penetrability (15%) and higher carbonation resistance (3%) further encourage its use in precast concrete incorporating (HESC). Finally, the beneficial effects of using slag waste in concrete were quantified by determining associated CO2 emissions. It is concluded that slag incorporation in concrete significantly reduces the CO2 emissions, (up to 68%) depending on the cement replacement level, thus promoting green construction and sustainable development.

Approximately, 0.3 million tons of waste glass sludge (WGS), a by-product of plate glass manufacturing is being landfilled or discarded every year around the globe. Previously, mechanical and durability properties of burnt clay bricks incorporating WGS were reported by authors. The focus of this study is to explore the thermal properties of industrially manufactured burnt clay bricks incorporating WGS. For this purpose, WGS was obtained from a local glass cutting and polishing industry. Burnt clay bricks incorporating different dosages of WGS (i.e, 5%, 10%, 15%, 20% and 25% by weight of clay) were prepared in an industrial kiln and were studied for different physico-mechanical and thermal properties. It was observed that dense brick specimens can be manufactured by using WGS in replacement of clay. Increase in compressive strength of clay bricks was observed after addition of WGS. Burnt clay bricks incorporating 25% WGS showed 37% increase in compressive strength. Reduction in apparent porosity and water absorption was also observed with increasing content of WGS in brick specimens. Microscopic images also showed dense and homogenous structure with reduced porosity after adding WGS in brick specimens, which increased the thermal conductivity of burnt clay bricks incorporating WGS. Control brick specimens showed thermal conductivity of 0.53 W/mK, which increased to 0.59 W/mK after incorporating 25% WGS in brick specimens. However, results were observed within the thermal conductivity range (i.e., 0.4–0.7 W/mK) of traditional burnt clay bricks for masonry construction. Based on this study, utilization of WGS (up to 25%) in the production of burnt clay bricks can be helpful in reducing the landfill and associated environmental problems of WGS. Moreover, burnt clay bricks with improved properties can be manufactured on industrial scale leading towards sustainable and cleaner production.

This paper studies the influence of polyvinyl alcohol (PVA) fibers on the mechanical and water resistance properties of fiber-reinforced magnesium phosphate cement (FR-MPC) mortar composites. The dosage of fiber was kept at 0%, 0.13%, 0.25%, 0.5% and 0.75% respectively. The increase in fiber content gradually reduced the fluidity of FR-MPC composites. The addition of PVA fibers increased the water absorption, porosity, and loss in mass. The compressive, three-point flexural, four-point flexural, and splitting tensile strength were improved with the addition of PVA fibers. In all cases, an amount of 0.5% PVA fiber was found as an optimum dosage. Fracture toughness and ductility performance were enhanced due to inclusion of fibers. However, there was a continuous decrease in water resistance with the increase in fiber content. Observations by SEM revealed that fibers show non-uniform distribution at a high dosage of 0.75%, which also corroborated with the findings of mechanical properties.

Due to the recent surge in the lithium slat industry, a high amount of lithium slag (LS) is generated as industrial waste and stacked open, causing environmental pollution and occupying land resources. In this regard, this research very first time investigates the use of LS to prepare and study the physical and mechanical properties of magnesium ammonium phosphate cement (MAPC). It is believed that results will be helpful in reducing the burden of LS on the environment and in improving the construction sector sustainability. For this purpose, LS was replaced with the MAPC by 10%, 20%, 30%, 40%, and 50%. A gradual increase in LS quantity decreased the fluidity and increased the setting time of LS-MAPC mortars. Comparison of results showed that heat curing of samples at 70 °C for 24 h produced LS-MAPC mortars having high strength than the air-curing. Among all mixtures, a replacement level of 10% was found as the optimum dosage and produced the best results as compared to other mixtures. Mechanical properties of LS-MAPC mortars were improved when amount of MAPC replacement by LS was 10%. Water absorption and porosity of mortars showed a direct relationship with the percentage of LS. Reaction products were studied by X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscope analysis and their findings corroborated with experimental results.

Burnt clay brick is one of the ancient building material. The use of waste materials in bricks can lessen the consumption of clay material and reduce the environmental burden due to accumulation of waste materials. Furthermore, addition of recycled materials can decrease the high carbon footprint. In the current study, bricks were manufactured using fly ash (by-product of coal) and conventional earthen materials. Fly ash was acquired from the coal power plant. Manufacturing of brick specimens was done in a local brick industry. The main variable in this study was the percentage of fly ash (i.e. 0–25% of clay). Results indicate that the compressive strength of bricks incorporating fly ash was lower as compared to that of clay bricks without fly ash. However, compressive strength of bricks incorporating up to 20% of fly ash satisfied the minimum requirements of the Pakistan Building Code. Reduction in weight was also observed in the fly ash bricks which would lead to overall weight reduction of the structures. Furthermore, less efflorescence was observed in bricks incorporating fly ash. Therefore, it can be concluded that clay bricks incorporating fly ash can be helpful in producing more sustainable bricks leading to economical solution.

Recycling of wastes in building materials is gaining a lot of attention worldwide. This not only conserves natural resources but also enhances the properties of existing building materials leading to economical and environment friendly construction. The main aim of this study was to explore the efficiency of waste marble powder (WMP) in controlling alkali silica reactivity (ASR) of concrete. For this purpose, WMP was obtained from a marble industry. To initiate the ASR phenomena, reactive aggregate was used in the study. Mortar bar specimens prepared with WMP as cement replacement material at 10%, 20%, 30% and 40% replacement levels (by cement weight) were evaluated in the standard ASTM C1260 test method. Compressive strength and thermal analysis tests were performed to investigate the effect of WMP on strength development of concrete. Results of compressive strength and thermal analysis showed improved strength after 10% of cement replacement with WMP. Moreover, 28% and 50% reduction in mortar bar expansion was observed after replacing 10% and 40% of cement with WMP, respectively. Scanning electron microscopic images also showed no signs of ASR cracking for mortar bars incorporating WMP. However, presence of cracks due to ASR was observed in control specimens. Furthermore, energy disperse X-ray spectroscopy (EDS) showed that amount of alkalies reduced after replacing cement with WMP, leading to overcome ASR expansion. Therefore, based on the results WMP can be effectively used to control ASR expansion leading to durable, sustainable and economical construction.

Pozzolanic materials are used worldwide to improve concrete properties. In this study, the pozzolanic behavior of sugarcane bagasse ash (SBA) and its role in controlling alkali silica reaction (ASR) was investigated. For this purpose, SBA was acquired from a sugar processing industry. Locally available reactive aggregates were used to introduce the phenomenon of ASR. To evaluate the role of SBA in mitigating ASR, mortar bar specimens were prepared following ASTM C1260 with various SBA dosages (10%, 20%, 30% and 40% by cement weight). To investigate the pozzolanic behavior of SBA strength activity index test and thermal analysis were performed. Results of activity index and thermal analysis showed the pozzolanic behavior of SBA. Moreover, reduction in mortar bar expansion was observed 23% and 46% after replacing 10% and 40% cement with SBA, respectively. Microscopic examination also showed no signs of cracks in mortar bars incorporating SBA; however minor cracking was observed in control specimens due to ASR. Furthermore, Energy disperse X-ray spectroscopy (EDS) showed low Ca/SiO2 ratio of mortar bars incorporating SBA due to dilution process and alkali absorption leading to control the ASR expansion. Therefore, based on the results it can be concluded that pozzolanic behavior of SBA can be helpful in controlling ASR expansion by binding alkalies.

Giving the high amount of carbon and energy emission from the use of traditional building materials, the use of bio-composites made from industrial crops especially hemp has caught attention from researchers in recent years. These bio-composites not only enhance the thermal performance of buildings but also promote sustainable development due to their eco-friendly nature. Due to their highly heterogeneous nature, however, most of the existing studies on the bio-composites have only focused on experimental investigations, while mathematical modeling of physical, thermal and mechanical properties of bio-composite remains a challenge for the researchers. In this paper, an artificial intelligence (AI) based gene expression programming (GEP) technique is used to develop the mathematical models for predicting the dry density, compressive strength and thermal conductivity of hemp-based bio-composites. A large amount of database was established based on past studies and the most influential parameters were identified by several trial analyses. The proposed mathematical models showed a high correlation with the experimental results. All the models passed the statistical and performance index checks showing strong predictability, generalization capability and high accuracy of GEP-AI models. Comparison of results with the regression analysis techniques further proved the superiority of GEP-AI models over the traditional methods.

The inferior performance of eco-friendly concrete owing to the addition of waste materials is a big hurdle in its practical adaptation. This study focuses on developing eco-friendly and green concrete, having performance similar to normal aggregate concrete (NAC). For this purpose, two waste products, including recycled aggregates (RA) and waste tire chipped rubber (CR), were used during the study. Furthermore, green concrete was also manufactured using RA treated through techniques such as lime immersion with carbonation and acetic acid immersion with mechanical rubbing. To achieve the strength of green concrete similar to NAC, an innovative concrete casting approach was followed. Green concrete specimens were cast and then compressed in the fresh state using specially designed molds. Results show that the compressive strength of recycled aggregate concrete (RAC) incorporating 20% CR in replacement of coarse aggregates is noticed 49% lower than NAC. However, the compressive strength and elastic modulus of compressed RAC and treated RAC incorporating 10-20% of CR in replacement of coarse aggregates are quite close to traditional concrete specimens without CR. No such method is available in the current literature through which green concrete incorporating RA and CR can achieve properties similar to NAC. Furthermore, the cost comparison and cement strength contribution index calculated in this study also show the industrial application potential of the new casting approach. Therefore, the developed concrete casting approach promotes the efficient utilization of RA and CR in the production of precast concrete members resulting in eco-friendly and sustainable construction.

This paper studies the influence of a new bio-based capillary active insulation (CAI) materials (corn stalk based vegetal derived concrete namely CS-1 and CS-2) and two traditional insulation materials (aerated autoclaved concrete (AAC) and aerated insulation brick (IB)) on the hygrothermal properties of multilayer wall. The reference wall consists of solid brick masonry plastered on the internal and external sides. Walls based on CAI materials consist of an extra layer of insulation and weather-resistive barrier (WRB) on the facade surface. Simulations were performed under the natural climatic condition of hot-humid and cold regions. Optimum thickness for the bio-based CAI materials to be used as internal insulation was 100 mm beyond which higher insulation thickness triggered the risk of mould growth. All walls based on CAI insulation materials (CS-1, CS-2, AAC, and IB) showed the mould index (MI) within the acceptable range. Bio-based CAI materials showed considerable improvement in the temperature and relative humidity at the interior surface. CAI materials reduced the heat losses through the wall by 58–69% as compared to the reference wall. Drying behavior of the wall was significantly improved with the combination of CAI and WRB and no risk of condensation was observed in the walls.