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The efficiency of load transfer between the concrete surface and carbon fiber reinforced polymer (CFRP) is greatly influenced by the adhesive agent used in any composite system. This study investigates the effects of using nano montmorillonite clay (nC) as a toughening agent with the epoxy adhesive, to improve the confinement efficiency of CFRP-wrapped stay-in-place (SIP) composite column. Twenty scaled columns were tested under axial compressive load including, unwrapped (reference columns) and wrapped with one layer (1 L) or two layers (2 L) of CFRP. Two cross-section column shapes, square and circular, were evaluated based on their nC-modified adhesive efficiency. Results revealed that SIP columns made with nC-modified epoxy adhesive showed superior compressive behavior, stress, and strain capacity, compared to unmodified composite columns, even when wrapped with 2 L of CFRP. Using 1 L and 2 L of CFRP bonded with unmodified adhesive of circular specimens, increased the confinement efficiency (CE) by about 134 % and 183 % respectively. However, the improvements for the circular specimens with nC-modified epoxy adhesive were higher by up to 15 % than their counterparts’ ones made with unmodified adhesive. For square specimens, the use of nC-modified adhesive improved the CE by up to 16 % as compared with their counterparts’ specimens made with unmodified adhesive.Scanning electronic images revealed that using adhesive modified with nC induces several shorter microcracks, instead of a few wide cracks appearing in the unmodified adhesive. This toughening mechanism as well as the enhancement in the IZ between the adhesive matrix and the fabric yarns, explain the improvements in the ultimate strain capacity of the column specimens made with modified adhesive.

This research study examines the practicability of using micro and nano size silica to improve the asphalt characteristics. Asphalt cement penetration grade of (60 /70) was prepared using (0%, 2%, 4% and 6%) of silica filler by weight of asphalt and investigated in terms of the softening point, penetration, and penetration index, viscosity, and ductility values. To modify the asphalt binder, the silica powder was mixed by a mechanical blender set at (2000) rpm at a mixing temperature of 140°C. However, the main challenge is an agglomeration of nano-silica powder which can reduce the ductility of nano silica modified binder. Therefore, this paper studies the efficiency of mixing period to obtain a homogeneous composite binder while alleviating the agglomeration issue. To do so, the effect of periods of mixing ranged between (30 to 60) minutes were examined on characteristics of modified asphalt binders. Overall, the addition of silica filler has an encouraging impact on the asphalt binder rheological properties. Also, the ductility value decreases with the addition of nano-silica content, attributed to the huge surface area and degree of agglomeration. Furthermore, results exhibited that 6% of micro silica powder and 4 % of nano silica powder were reasonable to develop the rheological properties.

Corrosion of reinforcement has been identified as the deterioration mechanism of reinforced concrete structures, which seriously affects the safety and integrity of structures. The corrosion of the embedded reinforcing steel in concrete is a major problem facing civil engineers today, which initiates 80% of the reinforced concrete structures deterioration. This paper reveals the outcomes of an experimental investigation on the mechanical performance (residual strength) of circular steel reinforced columns which have been damaged by corrosion of the steel rebar. Small scale circular reinforced concrete columns with a diameter of 100 mm and 300 mm in height were adopted. Different rates of steel reinforcement mass loss (corrosion damage) ranged between 10%, 20% to 30 % were created in the columns by using a galvanostatic accelerated corrosion method combined with wetting-drying cycles. The uniaxial compression test was implemented for damaged columns up to failure. Based on the experimental outcomes, it was revealed that the corrosion damage had substantially reduced the performance of columns. The decrement of the load capacity of corroded columns ranged between 19% to 40% and for corrosion level ranged from 10% to 30%, respectively. The decrement of the final deformation of corroded columns ranged between 15% to 30% and for corrosion level ranged from 10% to 30%, respectively. Likewise, the failure mode and relationship between the stress and strain for corroded columns had been adversely affected by corrosion.

Nitric oxide generated from various sources like car combustion is one of the most surrounding pollutants, which can be transferred from one form to another in the presence of sunlight. Titanium dioxide considered one of the most environmentally friendly active photocatalytics that can be used with building materials safely and effectively to react with nitric oxides. To study the possibility for the reduction of air pollutants like nitric oxides, two types of substrates coatings were prepared. First, mixing nano particles of TiO2 with cement paste in two percents 3% and 6%. Second, mortar substrates coated with nano TiO2 aqueous solution. Two coating methods have been used dip and spray. A laboratory test procedure was adopted to assess the performance of the prepared photoactive specimens. The specimens were subjected to NO gas and there efficiency in gas removal was monitored with time. Results showed the effectivity of coating building materials with titanium dioxide, the removal of gaseous pollutants like nitric oxide reached to 98.85% when spray and dip methods are used. Mixing nano titanium with a percent of 3% was also efficient in the removal of nitric oxides, the removal reached to 97%. It was concluded that spray method was more practical to be used.

Photon absorption parameters for glucose solution at different concentrations such as linear attenuation coefficient, mass attenuation coefficient, effective atomic number, electron density and density determined at 59.54 keV photon energy. The mass attenuation coefficient is calculated using the mixture rule and a correction factor to approximate the experimental model is added. Accordingly, the effective atomic number and electronic density appears to decrease with increasing glucose concentration. Moreover, the measured linear attenuation coefficient and the density for the solution are linearly increased with concentration. We can conclude that the electrical conductivity of the solution depends on the physical nature of the electrical charge carrier in the solution, concentration of the solute material, and the electronic density of the solution at the same time.

The effective linear attenuation coefficients and build-up factors for single shield of Al, Fe, Pb, and for multi-layer shield of Al-Pb, Al-Fe, Fe-Pb, Al-Fe-Pb as a function of shield thickness, atomic number, and order of the materials composing the shield are investigated for two photon energies of 0.662 MeV and 1.25 MeV. Two derived practical formulas to calculate the effective attenuation coefficient and build-up factor for multilayer shields are used. It is noticed that changing the order of the materials among the shield has no significant effect on the experimental result. Measurement agrees well with the trend of the suggested formulas for calculating the effective attenuation coefficient and the buildup factor. The linear attenuation coefficient is observed to have a strange dependency with the atomic number and photon energy. For single layer shield, the attenuation coefficient increases with decreasing atomic number at low photon energy and increasing with increasing atomic number at high photon energy.

Accurate measurement was carried out for the dose gradient in Teflon irradiated with filtered X-ray spectra having effective energies of 40 keV and 55 keV when in contact with aluminum, titanium, copper, and tin. At low photon energies, the interface region is only extended for about 10 microns from the interface, therefore, ultra-thin LiF/Teflon discs of the order of 3 microns thick was developed and used to measure directly the dose gradient in Teflon. Due to the relatively large slope of the depth dose curves near the interfaces, a displacement correction factor was introduced to determine the effective measuring point of the detector. A fitting exponential formula is suggested and used to estimate the dose gradient for Bone-Teflon interface. The interface dose for Bone-Teflon is 3.8 times the equilibrium dose at 70 KV, while it is about 3.1 at 100 KV.

This research concerned studying the combined effect of using nano-silica and/ or hybrid fibers on key mechanical properties of self-consolidating concrete SCC. A comprehensive experimental work has been carried out, using steel fiber (SF) with volume fraction (0, 0.5% and 1.5%), polypropylene fiber (PPF) (0%, 0.05% and 0.15%) and SiO2 nanoparticles (0%, 2% and 4%) by weight of powdered material (silica fume- Sf ) with constant w/c ratio (0.48) to produce eleven different mixtures and tested at different ages (7, 28 and 90 days). Results showed that adding fibers adversely affect SCC workability and thus more dosage of super plasticizer (SP) should be added to stay within the standard limits. comparable to conventional concretes, the presence of steel fibers with SCC provide slight increase in compressive strength at 28 days, (up to 11%), while significant enhancement in tensile properties were observed (up to 24% and 32% for splitting and flexural strength respectively). Polypropylene or hybrid fibers however, provide lower enhancement compared with steel fibers. In contrast, implementation of nanosilica leads to significant improvement in concrete strengths particularly at 4% dosage. Combined effect of 4% nanosilica and 1.5% of steel fibers provide the superior hardening effect on the flexural performance compared with softening effect provided by other added dosages. Scanning Electron Micrograph (SEM) images confirm the matrix densification effect due to nanosilica adding. Flexural strength of SCCs without nanosilica was generally higher than splitting testing results. This fact does not change even with the presence of nanosilica and/ or fibers.

This paper aims to give a recommendation about the suitable nano silica proportion and curing method for testing its strength pozzolonic activity, in addition to suggest a mixing or batching procedure of this material with other concrete ingredients. Theinfluence of nanoand micro silicaon concrete compressive strength is also studied. Three proportions of nano silica (0.5, 5, &10%) , two curing methods (accelerated in oven and normal in water) and two tested agesare used in pozzolonic activity test of nano silica. For compressive strength test, eleven mixes are considered:without-adding (two mixes), three micro silica (M) mixes with replacement ratios of 5, 10 & 15%, four nano silica (N) mixeswith replacement ratiosof 0.5,1.5, 3 & 5%, and three micro plus nano silica mixes (0.5N+9.5M,1.5N+8.5M and 3N+7M%) are adopted.Results of pozzolanic activity test denoted that nano silica has remarkable pozzolanic activity for all tested replacements.However, it is suggest using 5% nano silica for performing this testby usingeither accelerated or water curing. Additionally, it was found that nano silica had more impact on compressive strength of concrete than micro silica for all tested ages.Where, maximum enhancement ratios of compressive strength were about 33% and 27% for 3% nano silica mix at 7 and 90 days age respectively, and 22% for 5% nano silica mix at 28 days age. For micro silica mixes, higher improvement ratios were found in 15% micro silica mix: 2%,5%&7% at 7,28 &90 days age respectively.

The present work investigates the suitability of utilizing date palm residues in manufacturing wood-based cementitious boards. It also concerns other environment issues like trying to consume the pollutant carbon dioxides in the boards manufacturing process as an accelerated curing method. Two categories of date palm cellulose fiber cement boards were produced and evaluated, (8% and 5% cellulose fiber content by weight). Comparisons were made between the flexural strengths, stiffness and toughness of the produced boards whichfabricated with conventional and different concentrations of CO2 curing (i.e. 0%, 30%, and 100%). This paper is an attempt to fabricate sustainable products- preferably environmentally friendly- that incorporate agriculture waste in Iraq. Analysis results yielded that higher concentration (100%) has significant effects on the performance of the produced boards, particularly in lower fiber/matrix ratio (5%). Lower CO2 concentration; however, were generally comparable to those obtained at 0% concentration (conventional curing). SEM images confirm the matrix densification effect due to CO2 curing.

The main aim of this research is to study the effect of using hooked end steel fiber on the fresh and hardened properties of self-consolidating concrete. The experimental work includes two stages. First stage involved conducting several trial mixes and then choosing the one that conform tothe international standards in terms of fresh properties. Second stage concerned on the compressive, flexural tensile and splitting tensile strengths evaluationof the selected mixes, at 28 and 90 days.Four concrete mixes were obtained and evaluated. They were similar in mix proportions and differ only in volume fractions of steel fibers incorporated: 0%, 0.5%, 1%, and 1.5%. Results showed that adding hooked steel fibers adversely affect SCC workability and thus more dosage of SP should be added to stay within the standard limits. Similar to conventional HPC, the presence of steel fibers with SCC provide slight increase in compressive strength at 28 days, (up to 11%), while significant enhancement in tensile properties were observed (up to 68% and 80% for splitting and flexural strength respectively). Flexural strength (i.e. modulus of rapture) was generally still higher than splitting testing results in a decreasing order. This order is still applicable in SCC even with the presence of steel fibers.

Concrete elastic modulus is a basic property required for the appropriatepredicting of its basic behavior and for its correct implementation in a variety ofconstructional and engineering applications. This study presents an experimental and analytical evaluation of elastic modulus of high performance concretes (HPC) produced bysteel fiber and silica fume. The aim of this study is to develop the elastic modulus propertyof HPC and to show the applicability of ACI models to predict the elastic modulus of HPC from compressive strength. Four volume fractions of steel fiber with an aspect ratio (fiber length/ fiber diameter) of 60 were used (0, 0.5, 1.0, and 2.0 %). Incorporations of silica fume into the concrete were 0% and 15% by weight as a cement replacement. Water/cement ratio was ranged (0.28-0.4) with different amount of superplasticizer, and the reference slump was 170 mm. Both compressive and elastic modulus tests were made on hardened concretes reinforced with steel fibers and then compared with control specimens at 14 and 28 days. The results showed that the presence of silica fume enhanced the compressive strength and modulus of elasticity of evaluated concretes. In addition, adding steel fiber slightly increased both strength and modulus of elasticity values. Also, results showed that the elastic modulus of HPC is relative to the compressive strength, the ACI 318 expression is predicting elastic modulus of HPC and HPC-SF superior than ACI 363, but ACI 363 equation seems to be better in prediction modulus of elasticity of HPC-SF0.5S, HPC-F1.0S, and HPC-SF2.0S in comparison with ACI 318.

This study investigates the possibility of achieving unity energy response using the very sensitive CaSO4:Dy/Teflon thermoluminescent detector at photon energies below 100 keV. Accurate measurements for the energy responses were carried-out using ultra thin, 3 micron thick, TLD discs with average grain size of about 3μm. The present work shows that the experimental reduction factor for the 15 % phosphor loading with average grain size of 3 μm is in good agreement with the calculation based on the cavity theory but at grain size of 1.0 μm. This indicates that the cavity theory is underestimating the real experimental reduction factor in the energy response. The present work expect that unity energy response can be achieved with grain size of about 1 μm.

Microstructure imaging interpretation of polished surface has become well established as a method for the study of cement and concrete microstructure. This paper is an attempt to provide micro-level examination to the microstructure of cement paste in concrete particularly the hydrated mineral admixture and interfacial transition zone, which received increasing attention due to their effect on the hardened concrete properties. Furthermore, illustrations are provided of the transition area of cement paste adjacent to the aggregate border as well as other cement paste areas. SEM images reveal that pozzolanic reaction is not the only benefit of using mineral admixture. Spherical shape of grains is important to improve the microstructure of cement paste particularly in the interfacial transition zone.

The main aim of this study was to evaluate the asphalt mixture properties for samples that were taken from different sites and plants: Amanat Baghdad, Faluja municipality, and Baghdad Governorate, which almost produced in private plants. Forty seven asphalt mixtures samples were tested following Marshall Test. The tested properties were: Marshall Stability, Marshall Flow, specimen density, and air voids. Asphalt extraction was carried out according to quantative extraction of bitumen from paving mixtures test. A statistical analysis of the collected field data was performed and a prediction model was built. The variables such as asphalt content, stability and flow data were analyzed using computer software. The statistical analysis includes four stages: data extraction and evaluation, verification, calibration, and validation.Results of this study indicate that both of Marshall Stability and Marshall Flow correlate positively with asphalt content, but with different degree. Asphalt content affect Stability property much more than flow property of the asphalt mixes.

In this study, the compatibility of five different cement based repair materials and substrate concrete was investigated in three stages. First stage includes studying the individual properties of repair materials, and also two types of concrete, such as compressive strength, flexural strength, and dry shrinkage using BS 1881: part 116, ASTM C78-06, ASTM C157 -06 test procedure respectively. Second stage includes evaluating the bond strength of composite cylinder for different combinations of repair materials and substrate concrete. Third stage includes investigating the compatibility using a composite beam of repair material and substrate concrete under third point loading.The experimental results show that one individual property has no crucial effect on the success of concrete repair system. Bond strength and dry shrinkage however has a strong indication about the compatibility.

In this study, the mechanical properties of five different cement based repairing materials were evaluated. These materials were classified into two groups: laboratory made materials with or without admixtures (3 types), and other two types of commercial proprietary pre-packaged with additives. Mechanical properties, such as compressive strength, modulus of rupture and drying shrinkage were studied. Results show that these mechanical properties were varying significantly from each other. The drying shrinkage of the commercial proprietary repair materials was less than that of the conventional mortar. This will lead to a reduced cracking risk in the former repair materials compared to the latter. Through the regression analysis on the experimental data collected, power relation with coefficient of determination of 0.766 is obtained between compressive and modulus of rupture.

This comparison study focuses on the impacts of using nano-silica (nS) on chemical attack resistance of self-consolidating concrete (SCC) and its effectiveness in comparison to similar replacement levels of the more widely employed micro-silica (mS). Two types of cement were used to produce concrete mixes and three different percentages (3, 4.5, and 6 %) of nanosilica and microsilica were added as a replacement of cement by weight. Concrete specimens were cast and exposed to four harmful conditions including: sulfate solution, chloride solution and both of them for a period of up to 400 days. Based on the obtained results, replacement with colloidal nS proved to be significantly more effective in the chemical resistance than equivalent replacement of dry powder mS. The noticed improvements in chloride resistance and chloride penetration performance for concretes contained nS was correlated with the compressive strength results, which indicates for better pore structure characteristics. As expected, the improvement in the chemical resistance was more pronounced in concretes with cement type V.

In this study, the compatibility of Metakaolin repair mortar and substrate concrete was investigated in three stages. First: individual properties of Metakaolin as a pozzolanic material and conventional repair materials(cement mortar), and two types of concrete, such as compressive strength, split tensile strength, and flexural strength, were determined using standard ASTM test procedure. Second: the bondstrength of composite cylinder for different combinations of repair materials and substrate concrete were evaluated. Third: the compatibility was investigated using a composite beam of repair material and substrate concrete under third point loading.The experimental results indicated that repairing weak substrate concrete by Metakaolin modified repair material is not preferable du to disparity in mechanical properties and create high level of mismatch between them. Furthermore, bond strength is considered as great influence factor on the success range of repair system.

In this study, the compatibility of polymer modified repair mortar andsubstrate concrete was investigated in three stages. First stage includes studying the individual properties of polymer and conventional repair materials, and also two types of concrete, such as compressive strength, split tensile strength, and flexural strength using standard ASTM test procedure. Second stage includes evaluating the bond strength of composite cylinder for different combinations of repair materialsand substrate concrete. Third stage includes investigating the compatibility using a composite beam of repair material and substrate concrete under third point loading. The experimental results show that the compressive strength, split tensile strength and flexural strength is not a crucial factors for the success of concrete repair system. While bond strength tests are provide strong indication about thecompatibility. The bond strength of S.B.R polymer material produced by Al- Khaleej Company was not strong enough to be recommended to use for concrete repairing systems.

The applications of a mineral admixture, or a zinc coating to steel surface, or acombination of both are methods used for the corrosion prevention of ferrocementelement in this study. Results of a study to evaluate many corrosion protection systemswith metakaolin and/or galvanized steel mesh are presented in six U-shaped specimens.Specimens were built to simulate exposure conditions typical for marine environment.Laboratory data collected along duration of 40 weeks of exposure were used inmodeling the cover depth as a function of time to corrosion initiation of the investigatedcorrosion prevention methods. Methods used to assess the condition of specimensincluded chloride concentration measurements, and corrosion rates. Model predictionsshow that the ferrocement specimen of high-performance mortar with metakaolinprovides much better level of protection against moisture and chlorides than theconventional specimen, by delay rate of chloride ingress. Application of a galvanizedsteel mesh causes an elevation of the chloride threshold resulting in an additionalincrease in the predicted time to corrosion initiation.

Two types of whey protein concentrates were prepared,one from acid whey and the other from sweet whey .These preparations were acetylated and succinylated to various degrees and their functional properties were assessed. Acetylation or succinylation of different whey protein concentrates decreased protein ,lactose and fat,but their total solid and gel strength were increased. Functional properties of sweet and acid whey protein concentrates were more effected by acetylation compared to succinylation. Nine treatments of yoghurt were made to study the effect of fortification of cow milk with acetylated and succinylated whey protein concentrates on the quality of yoghurt at 2 and 4% ratios. Total protein,ash and curd tension ,while whey syneresis decreased by fortification of cow milk with acetylated and succinylated whey protein concentrates through zero,1,3 and 4 days of the storage period. This effect was greater with 4 fortification .Results showed that ash% were higher in the yoghurt fortified with acid whey protein concentrate compared to that of sweet whey protein concentrate. Organoleptic scores of yoghurt fortified with acetylated and succinylated whey protein concentrates to 2.0% were not significantly different from those of the control yoghurt. The yoghurt fortified with 2.0% gained the highest organoleptic scores and was the most acceptable product.

AbstractThe replacement of waste glass powder (WGP) and electric arc furnace slag (EAFS) is a sustainable method for cost-effective and eco-friendly ultra-high-performance concrete (UHPC). This article evaluates the effects of using EAFS and WGP as weight replacements with fine aggregates and cement on the flow, setting time, compressive strength, thermal conductivity, and environmental performance. Nano-silica (NS) powder was used as a possible controller for the best rheological and hardened properties. Binary and ternary binder blends were assessed using the design of experiments (DoE) approach to investigate the technical feasibility of EAFS, WGP, and NS and their complementary role in improving concrete properties. Along with life cycle assessment (LCA), numerical optimisation was performed using second-order polynomial models accurately correlated between the investigated parameters and dependent responses to obtain an eco-friendly mixture having proper rheological properties and maximum compressive strength (>150 MPa). Results indicated replacing 11.6% WGP, 70% EAFS, and 0.6% NS in the UHPC mixture produced a 200-mm flow with enhanced strength (192 MPa). Maximum replacement of EAFS, 50%, and WGP, 30%, shows the best performance in energy, material, and climate footprints with a saving potential of up to 26%. In comparison, less saving is shown regarding water footprint with 9%. [ABSTRACT FROM AUTHOR]