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Utilization of high-performance and highly reactive sustainable materials in concrete are gaining popularity nowadays for the development of strong, durable and sustainable infrastructures. Therefore, current study focuses on viable use of highly reactive silica extracted from rice husk ash (RHA) for the production of high-performance sustainable cement mortar. Mortar containing various percentages of extracted micro-silica (EMS) as a partial substitute of cement (5%, 15%, and 25%) were cast to test fresh as well as hardened properties, and compare its results to that of control mortar. Test results showed that the standard consistency increased with increasing percentage of EMS, whereas, a delay in the setting time was observed. The compressive and flexural strengths of all mortar mixes containing EMS were improved with aging and an effective role played by EMS in mitigating the expansion caused by the alkali–silica reaction was observed. However, a slight reduction of strength at later ages was observed in mortar having 25% EMS. At relatively low addition of EMS (5% and 15%), micro- and pore structural investigations revealed the formation of improved high-density C-S-H phases, which aid the formation of refined and homogenous microstructures. The agglomeration was observed through micro- and pore structural investigations in high dosage EMS mortars that occurred due to the oversaturation and poor dispersion, which consequently affected the hydration products and increased the porosity of the paste matrix. The current findings suggest that the reactive silica resource extracted from RHA can be used as a potential revenue stream in concrete industry for the development of high-performance and sustainable cement mortar.

Surface electromyography (sEMG) signals acquired with linear electrode array are useful in analyzing muscle anatomy and physiology. Most algorithms for signal processing, detection, and estimation require adequate quality of the input signals, however, multi-channel sEMG signals are commonly contaminated due to several noise sources. The sEMG signal needs to be enhanced prior to the digital signal and image processing to achieve the best results. This study is using spatio-temporal images to represent surface EMG signals. The motor unit action potential (MUAP) in these images looks like a linear structure, making certain angles with the x-axis, depending on the conduction velocity of the MU. A multi-scale Hessian-based filter is used to enhance the linear structure, i.e., the MUAP region, and to suppress the background noise. The proposed framework is compared with some of the existing algorithms using synthetic, simulated, and experimental sEMG signals. Results show improved detection accuracy of the motor unit action potential after the proposed enhancement as a preprocessing step.

In the current research work, an attempt is made to increase the seismic capacity of unreinforced masonry (URM) structures by proposing a new composite material which can improve shear strength and deformation capacity of URM wall systems. Fiber Reinforced Polymer (FRP) having high tensile and shear stiffness can significantly increase in-plane and out-of-plane strength of masonry walls, but, inherently, FRP strengthened wall systems exhibit brittle failure under extreme seismic loading. Polypropylene (PP-band) is a low cost material with sufficient ductility and deformation capacity. Keeping in view the behavior of FRP and PP-band, a composite of FRP and PP-band is proposed for retrofitting of URM walls. Mechanical behavior of the proposed composite material is assessed by carrying out an in-plane diagonal compression test and an out-of-plane bending test on twenty-five 1/4-scaled masonry wall panels. Experimental plan for each panel, URM, PP-band retrofitted, FRP retrofitted and FRP + PP-band retrofitted masonry, is diagonal compression test and three-point bending test. Experimental results have determined that FRP + PP-band composite increased, not only the initial peak strength, but also the ductility, deformation capacity and residual strength of URM wall systems.

In this study, the influence of mechanically activated electric arc furnace slag (EAFS) was investigated through compressive strength tests on 50 mm mortar cubes. The objective was to convert the wasteful EAFS into a useful binding material to reduce the cement content in concrete without compromising strength and economy. Four different groups of mortar were cast which include control mortar, reference fly ash mortar, mortar containing EAFS to determine its optimum fineness and replacement with cement, mortar blend containing fly ash and EAFS of optimum fineness. EAFS were identified with respect to its fineness as slag ground (SG), slag-fine (SF) 100% passing 75 µm sieve, and slag-super-fine (SSF) 100% passing 45 µm sieve. Compressive strength was measured according to ASTM C109. Specimens were cured under different temperatures and moisture to incorporate the effects of normal and hot environmental conditions. Compressive strength of mortars increases with fineness of EAFS and its strength activity index matches the ASTM C989 blast furnace slag (BFS) Grade 80 up to 30% cement substitution and Grade 100 when 10% cement substituted with SSF. The influence of curing temperatures was also significant in mortars containing SG or 10% SF where strength decreased with increasing curing temperature. However, a 20–30% and 20% cement substitution with SF produced strength comparable to control and reference fly ash mortars under moderate (40 °C) and high curing temperature (60 °C), respectively. The utilization of EAFS as binder in concrete may reduce needs for cement, as well as save environment and natural resources from depletion.

The ability of encapsulated Burkholderia cepacia G4 (ATCC 53617) for trichloroethylene (TCE) degradation (1.5, 5, 10, and 20 mg/L) in the presence of toluene (10 and 60 mg/L) as enhancement substrate was evaluated experimentally. Burkholderia cepacia G4 cultures were encapsulated in cylindrical pellets (4 mm in diameter and 4 mm in height (preferred)) using polyethylene glycol (PEG). Higher transformation capacities were observed for the encapsulated cultures for both toluene concentrations. The highest transformation capacities measured for the encapsulated cultures and suspended cultures were 46.98 and 5.94 μg TCE/mg biomass, respectively. The Monod equation was used to simulate the degradation rates of toluene and Haldane's equation was employed to describe the degradation kinetics of TCE. The first-order reaction rate constant (k/Ks) for toluene degradation in the encapsulated cultures was 2.3-fold higher than the value of the suspended cultures, whereas the kc/Ksc value for TCE was 4.3-fold higher compared to the suspended cultures. The higher kinetic values of the encapsulated cultures indicate that the degradation efficiency and capability of B. cepacia G4 was enhanced through PEG encapsulation. Moreover, the higher inhibition constant value for the encapsulated cultures compared with the suspended cultures demonstrated that PEG-encapsulated B. cepacia G4 can tolerate and degrade much higher TCE concentrations.

This study focuses on evaluating the effect of the fineness of basaltic volcanic ash (VA) on the engineering properties of cement pozzolan mixtures. In this study, VA of two different fineness, i.e., VA fine (VF) and VA ultra-fine (VUF) and commercially available fly ash (FA) was used to partially replace cement. Including a control and a hybrid mix (10% each of VUF and FA), eleven mortar mixes were prepared with various percentages of VA and FA (10%, 20% and 30%) to partially replace cement. First, material characterization was performed by using X-ray florescence (XRF), X-ray powder diffraction (XRD), particle size analysis, and a modified Chappelle test. Then, the compressive strength development, alkali silica reactivity (ASR), and drying shrinkage of all mortar mixes were investigated. Finally, XRD analysis on paste samples of all mixes was performed to assess their pozzolanic reactivity at ages of 7 and 91 days. The results showed increased Chappelle reactivity values with an increase in the fineness of the VA. Mortars containing high percentages of VUF (20% and 30%) showed almost equal compressive strength compared to corresponding FA mortars at all ages, however, the hybrid mix (10% VUF + 10% FA) exhibited higher strength than that of the reference mix (100% cement), particularly, at 91 days. At low percentages (10%), ASR expansion in both VF and VUF mortars was higher compared to the corresponding FA mortar and the opposite behavior was observed at high percentages (20% and 30%). Among all the mixes including the control, mortar with VUF was found to be most effective in controlling drying shrinkages at all ages. The rate of consumption of calcium hydroxide (Ca(OH)2) for pastes containing VUF and FA was almost the same, while VF showed low Ca(OH)2 intensity. These results indicate that an increase in the fineness of VA significantly improvs performance, and therefore, it could be a feasible substitute for commercial admixtures in cement composites.

The bending and shear behavior of RC beams strengthened with Carbon Fiber-Reinforced Polymers (CFRP) is the primary objective of this paper, which is focused on the failure mechanisms and on the moment-curvature response prior-to, and post, strengthening with different amounts and layouts of the CFRP reinforcement. Seven reinforced concrete beams were tested in 4-point bending, one without any CFRP reinforcement (control beam, Specimen C1), four with the same amount of CFRP in flexure but with different layouts of the reinforcement for shear (Specimens B1&ndash, B4), and two with extra reinforcement in bending, with and without reinforcement in shear (Specimens B6 and B5, respectively). During each test, the load and the mid-span deflection were monitored, as well as the crack pattern. The experimental results indicate that: (a) increasing the CFRP reinforcement above certain levels does not necessarily increase the bearing capacity, (b) the structural performance can be optimized through an appropriate combination of CFRP flexural and shear reinforcement, and (c) bond properties at the concrete&ndash, CFRP interface play a vital role, as the failure is very often triggered by the debonding of the CFRP strips. The experimental values were also verified analytically and a close agreement between the analytical and experimental values was achieved.

The effects of different catchment types and storage conditions on Pseudomonas aeruginosa in harvested rainwater under wet and dry seasons were investigated. Both horizontal (roof intercepted to outlet point) and vertical (surface to bottom) quality variation inside storage tanks of different rainwater harvesting (RWH) systems was also monitored. The numbers of P. aeruginosa varied from 30 to 400 colony forming units (CFU)/100 mL during the dry season and 200 to 1800 CFU/100 mL during the wet season. A relatively good quality of harvested rainwater was observed in dry season. The horizontal and vertical quality variation of P. aeruginosa revealed best quality at the supply point. The number of P. aeruginosa was the highest (about 1800 and 1000 CFU/100 mL during wet and dry seasons, respectively) in rainwater harvested from mountain catchment while the lowest (about 30 and 1000 CFU/100 mL during dry and wet seasons, respectively) numbers was seen from concrete roof catchment. Dark, covered storage conditions resulting low rainwater temperatures showed better microbial quality of rainwater than uncovered and open storage conditions exposed to light. The study suggests that the improvement in the quality of harvested rainwater is possible when appropriate tank designs, maintenance of catchment surfaces, and proper storage conditions are considered in RWH systems.

This paper investigates prediction models estimating the hydration properties of concrete, such as the compressive strength, the splitting tensile strength, the elastic modulus,and the autogenous shrinkage. A prediction model is suggested on the basis of an equation that is formulated to predict the compressive strength. Based on the assumption that the apparent activation energy is a characteristic property of concrete, a prediction model for the compressive strength is applied to hydration-related properties. The hydration properties predicted by the model are compared with experimental results, and it is concluded that the prediction model properly estimates the splitting tensile strength, elastic modulus, and autogenous shrinkage as well as the compressive strength of concrete.

To predict thermal stress independent of uncertain material properties of early age concrete, a new thermal stress device was developed by Kim et al. in [1] . Several experiments and numerical analyses were performed to verify its validity. However, the application of the device in a real structure has yet to be attempted. Thus in this paper, the application of a stress device for predicting hydration-induced thermal stress in an actual structure is investigated. For this purpose, a series of experiments were performed by varying the amount of restraint in the thermal stress device. The reasonably good agreement between the restraint strains from the site and the stress device indicates that variation of the thermal stress at any position in concrete structures can be measured during the design stage even when the properties of the concrete are uncertain. The application of various degrees of constraint at a site can be achieved by the thermal stress device by varying the thermal expansion coefficient and the cross sectional area of the restraining frame.

The current study is devised to evaluate the seismic performance of fiber-reinforced polymer (FRP) retrofitted buildings with openings at different FRP reinforcement levels. Required objectives are achieved by performing five shake table tests on 1/4-scale models of single-story boxlike masonry buildings. Out of five building models, one was an unreinforced masonry (URM) building model whereas the other four were retrofitted with different quantities and layouts of FRP reinforcement. FRP reinforcement is reduced by decreasing FRP strip widths and strip spacing and applying FRP strips on either the inside or outer faces of walls. Each building model was subjected to the same series of input ground motions with gradually increasing amplitudes. A series of diagonal compression tests was also conducted to decide the appropriate type of FRP and trial FRP reinforcement ratios for the masonry building models. Descriptions of the tested models are provided, including the structural response in terms of ba...

Structural hollow sections are gaining worldwide importance due to their structural and architectural advantages over open steel sections. The only obstacle to their use is their connection with other structural members. To overcome the obstacle of tightening the bolt from one side has given birth to the concept of blind bolts. Blind bolts, being the practical solution to the connection hindrance for the use of hollow and concrete filled hollow sections play a vital role. Flowdrill, the Huck High Strength Blind Bolt and the Lindapter Hollobolt are the well-known commercially available blind bolts. Although the development of blind bolts has largely resolved this issue, the use of structural hollow sections remains limited to shear resistance. Therefore, a new modified version of the blind bolt, known as the “Extended Hollo-Bolt” (EHB) due to its enhanced capacity for bonding with concrete, can overcome the issue of low moment resistance capacity associated with blind-bolted connections. The load transfer mechanism of this recently developed blind bolt remains unclear, however. This study uses a parametric approach to characterising the EHB, using diameter as the variable parameter. Stiffness and load-carrying capacity were evaluated at two different bolt sizes. To investigate the load transfer mechanism, a component-based study of the bond and anchorage characteristics was performed by breaking down the EHB into its components. The results of the study provide insight into the load transfer mechanism of the blind bolt in question. The proposed component-based model was validated by a spring model, through which the stiffness of the EHB was compared to that of its components combined. The combined stiffness of the components was found to be roughly equivalent to that of the EHB as a whole, validating the use of this component-based approach.

To accurately estimate the temperature effects on autogenous shrinkage of concrete, a new prediction model based on time–temperature dependent activation energy is proposed in this study. For this purpose, a series of autogenous shrinkage tests are performed considering different water to cementitious materials ratios and curing temperatures. Results revealed that the temperature dependency of autogenous shrinkage cannot be described solely by the simple time shift of the existing maturity method. In particular, maturity cannot incorporate the cross-over effect of autogenous shrinkage by which later age autogenous shrinkage of concrete, subjected to low curing temperature, usually exceeds the autogenous shrinkage of concrete subjected to relatively high curing temperature. Therefore, to overcome the shortcomings of the maturity method, a new prediction model based on time–temperature dependent activation energy is proposed. Reasonably good agreement is observed between experimental and predicted autogenous shrinkage, thus indicating that the proposed prediction model can be successfully used to estimate the time–temperature effects in the development of autogenous shrinkage. However, the absolute value of autogenous shrinkage strain still cannot be obtained from the proposed model, because the model gives only the development of autogenous shrinkage. Therefore, a prediction model for the absolute value of autogenous shrinkage is needed in order to obtain predicted autogenous shrinkage strain.

In this study, we investigate and improve the testing methods for more accurate measurement of the early-age autogenous shrinkage (AS) in concrete. During the first 24 h after casting, the temperature of concrete rises due to hydration heat and causes the simultaneous development of thermal deformation (TD) and AS. Because there is no general agreement on evolution of coefficient of thermal expansion (CTE) in the literature, the most commonly adopted approach of subtracting the TD based on an assumed constant value of CTE results in incorrect values of early-age AS. To avoid such errors, we propose improvements in measuring rig and control of hydration-induced temperature, which serves as an aid in achieving isothermal conditions in concrete specimens right after casting. The validity of the proposed improvements is investigated by performing a series of tests under semi-adiabatic (including TD) and artificially controlled isothermal conditions (excluding TD). Results indicate that the AS calculated from ...

An experimental study is conducted to simulate the thermal stresses generated in mass concrete. Accurate prediction of the thermal stresses by analysis is quite difficult particularly at early ages, due to uncertain age-dependent properties of concrete. A series of tests was conducted in which the amount of restraint in a thermal stress device (TSD) was varied. The effect of aging and the amount of restraint on stress development that can occur in realistic structures was evaluated. The influence of the uncertain early-age properties of concrete (i.e., elastic modulus, thermal dilation, autogenous deformation and transitional thermal creep), on the generation of thermal stresses was incorporated using a TSD due to the simultaneous development of temperature and the corresponding stress in a restrained specimen from the very beginning of the process. The effect of various amounts of restraint on the generation of thermal stress was pronounced. Numerical simulations of the thermal stress setup were also performed using the finite element code DIANA to verify and extend the experimental interpretation and to determine the maximum value of restrained stress which would occur under highest level of restraint. Adopting this methodology may simplify the complexity of thermal stress analyses (i.e., more precise 3-D thermal stress analysis can be performed using material properties achieved from 1-D uniaxial tests) due to the difficulty of accurately determining the early-age properties of concrete.

Efficiency of solar based disinfection of Pseudomonas aeruginosa (P. aeruginosa) in rooftop harvested rainwater was evaluated aiming the potability of rainwater. The rainwater samples were exposed to direct sunlight for about 8-9 hours and the effects of water temperature (°C), sunlight irradiance (W/m2), different rear surfaces of polyethylene terephthalate bottles, variable microbial concentrations, pH and turbidity were observed on P. aeruginosa inactivation at different weathers. In simple solar disinfection (SODIS), the complete inactivation of P. aeruginosa was obtained only under sunny weather conditions (>50°C and >700 W/m2) with absorptive rear surface. Solar collector disinfection (SOCODIS) system, used to improve the efficiency of simple SODIS under mild and weak weather, completely inactivated the P. aeruginosa by enhancing the disinfection efficiency of about 20% only at mild weather. Both SODIS and SOCODIS systems, however, were found inefficient at weak weather. Different initial concentrations of P. aeruginosa and/or Escherichia coli had little effects on the disinfection efficiency except for the SODIS with highest initial concentrations. The inactivation of P. aeruginosa increased by about 10-15% by lowering the initial pH values from 10 to 3. A high initial turbidity, adjusted by adding kaolin, adversely affected the efficiency of both systems and a decrease, about 15-25%; in inactivation of P. aeruginosa was observed. The kinetics of this study was investigated by Geeraerd Model for highlighting the best disinfection system based on reaction rate constant. The unique detailed investigation of P. aeruginosa disinfection with sunlight based disinfection systems under different weather conditions and variable parameters will help researchers to understand and further improve the newly invented SOCODIS system.

The severe hot temperature and high traffic loadings in the Kingdom of Saudi Arabia (KSA) are causing distress in flexible pavements within a few years of service. Secondly, the conventional bitumen extracted from Saudi oil refineries have a performance grade of 64-10 (PG 64-10), which does not meet the SuperPave performance grade requirement for most of the KSA’s regions. In order to improve the performance grade of bitumen, different percentages of municipal wastes (plastic and crumb rubber) were used as bitumen additives. The performance of bitumen at low, intermediate, and high temperatures was evaluated. This is important as the waste production is rising significantly due to the fast urbanization and high population growth in the KSA. Particularly, when there are very few ways of recycling these wastes (municipal, as well as industrial), which in fact have great impact on the environment. High-density polyethylene (HDP), low-density polyethylene (LDP), and crumb rubber (CR) with 5%, 10%, and 15% by weight of bitumen, were mixed with the base bitumen (PG 64-10). Rotational viscometer (RV), dynamic shear rheometer (DSR), and bending beam rheometer (BBR) were used to evaluate the viscosity, rutting, fatigue, and low-temperature behavior of base and modified binders. The test results indicated that the rutting (permanent deformation) and fatigue resistance were significantly improved in modified binders due to the improvement in the visco-elastic properties.

This study investigates the influence of different curing temperatures and humidity conditions on the development of mechanical properties of sulphate resistant concrete (SRC) and its prediction relations. A series of experiments were performed considering three distinct curing temperatures (20°C, 40°C, and 60°C). For each curing temperature, 60-specimen were cast and exposed to four different moisture conditions (moist, 55% humidity, three-day moist then 55% humidity, seven-day moist then 55% humidity). The experimental results revealed that higher curing temperatures along with continuous lower and higher degrees of saturation yield high early-age and lower 28-day compressive strength, splitting tensile strength, and elastic modulus of SRC and vice versa for lower curing temperatures. Finally, applicability of existing relationships to estimate elastic modulus and splitting tensile strength from compressive strength of concrete were investigated. Prediction models which best fits the current experimental results were identified and proposed for their future uses in SRC.

An experimental study was conducted to simulate the generation of thermal stresses due to hydration heat and restraint by using a thermal stress measuring device (TSD). The net effects of time-dependent properties of hardening concrete can be well incorporated in TSD due to simultaneous development of temperature and corresponding stress in restrained specimen. Moreover, experiments were conducted to measure a precise value of early-age autogenous shrinkage (AS) and to evaluate the basic creep model with respect to AS. In cracking risk analysis, precise value of early-age AS must accurately predict the time of shrinkage-induced cracking. A significant difference exists between apparent (including AS) and real basic creep (excluding AS) for low water-cement ratio concrete and early-age normal strength concrete. To improve the crack sensitivity analysis, it is recommended to precisely measure early-age AS and modify the basic creep model to prevent from possible errors and computational problems.