The reactive powder concrete (RPC) is one of the special concrete types that characteristics with high cement content which means high production cost and CO2 emissions to the atmosphere. Therefore, to enhance the environment as well as to develop green RPC, alternatives to cement, such as supplementary cementitious materials (SCMs) were used. Limited studies addressed the use of a high volume fraction of SCMs as a binary combination in the production of RPC. Thus, this study aims to replace a high percentage of cement (50%) with binary combinations of silica fume (SF), type F fly ash (FA) and metakaolin (MK). The experimental program included two phases. In phase one, two groups (SF+FA and MK+FA) were cast without steel fibers. Based on group performance in the first phase, one group was chosen to be used with steel fibers in the second phase. The flow rate, compressive and flexural strengths, density, ultrasonic pulse velocity and dynamic modulus of elasticity tests were conducted. The phase one results showed that SF+FA combination mixtures had better performance than MK+FA mixtures thus they were selected to be used in the second phase (with the addition of 1% volumetric fraction micro steel fibers). Results indicated that it is possible to produce sustainable RPC in which the cement can be replaced with 30% SF and 20% FA (the total replacement is 50%) in the presence of 1% steel fibers with a remarkable enhancement in compressive strength and flexural strength reached up to 44% and 10%, respectively.
Cement is considered a base material in preparing blending mixtures that applying in various projects in the civil engineering field. Nevertheless, the cement production process cause indubitable negative environmental influences such as emitting CO2. The production of cement produces around 7% of the global CO2 emissions. Thus, searching for alternate binders in building processes to minimise or substitute cement has been one of the social problems. A by-product or waste products are among the potential alternatives to the mentioned problem. The present investigation involves the consumption of paper sludge ash (PSA) waste as cement replacement to produce environmentally friendly, cementitious material. Limited studies were addressed the PSA grinding time impact on mortar or concrete properties. Moreover, limited studies replaced the cement with high volume of PSA. Therefore, during this study, the effect of grinding time and replacement level (up to 50%) of the PSA on the surface electrical resistivity and compressive strength of mortar were investigated. Three grinding periods (in addition to without grinding), two replacement levels and three testing ages were considered. The results indicated that grinding the PSA for 10 minutes and use it to replace up to 50% of the cement content have similar mechanical and durability performance to ordinary Portland cement after 28 curing days. This innovative binder will also cause a major difference in decreasing the building materials cost and CO2 emissions.
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.
Environmental pollution and the relatively high cost of waste disposal has been a major focus for scientists around the world, leading researchers to find a solution to reuse waste materials in different applications. Iraqi people consume hundreds of tons of black tea each year, which produce a large quantity of the used tea, leaves as waste. These large quantities go to landfills without any benefit or recycling. Additionally, landfills are considered one of the biggest crisis facing the Iraqi government. Therefore, this study aims to recycle the black tea waste ash (BTWA) by utilizing it as a partial replacement of cement. Cement mortar mixes containing five replacement levels of cement with BTWA (0%, 2.5%, 5%, 7.5% and 10% by weight) were carried out. The compressive strength and flexural strength tests were adopted to show the effect of BTWA on mechanical properties of cement mortar. The flow rate of fresh mortar was also measured. Results indicated that, up to 7.5% replacement, the compressive strength values were improved. For 10% replacement, the compressive strength values were equal to that for control specimens. In contrast, the BTWA had a negative impact on the flexure strength of mortar at replacement levels 5%, 7.5% and10%. For 2.5% substitution, however, the flexure strength was enhanced slightly (about 2%).
The increase in cement production as a result of growing demand in the construction sector means an increase in energy consumption and CO2 emissions. These emissions are estimated at 7% of the global production of CO2. Ultra-high-performance concrete (UHPC) has excellent mechanical and durability characteristics. Nevertheless, it is costly and affects the environment due to its high amount of cement, which may reach 800–1000 kg/m3. In order to reduce the cement content, silica fume (SF) was utilized as a partial alternative to cement in the production of UHPC. Nevertheless, SF is very expensive. Therefore, the researchers investigated the use of supplementary cementitious materials cheaper than SF. Very limited review investigates addressed the impact of such materials on different properties of UHPC in comparison to that of SF. Thus, this study aims to summarize the effectiveness of using some common supplementary cementitious materials, including fly ashes (FA), ground granulated blast furnace slag (GGBS), metakaolin (MK) and rice husk ashes (RHA) in the manufacturing of UHPC, and comparing the performance of each material with that of SF. The comparison among these substances was also discussed. It has been found that RHA is considered a successful alternative to SF to produce UHPC with similar or even higher properties than SF. Moreover, FA, GGBS and MK can be utilized in combination with SF (as a partial substitute of SF) as a result of having less pozzolanic activity than SF.
This study aims to investigate the effect of ternary combination of silica fume, and glass and ceramic waste as a partial replacement of cement on selected properties of mortar in the presence of steel-polypropylene hybrid fibers. Thirteen mixtures have been made: one control mix and twelve mixes in which the cement has been replaced by constant proportion (30% of cement weight) of ternary combination of silica fume, and glass and ceramic waste. The steel fibers have been added in the proportion of 1% while polypropylene fibers have been applied in the percentages of 0.25%, 0.5% and 1% (by volume for both fibers types). The flow rate, the compressive and the flexure strength and the bulk density tests have been examined. The hardened tests have been carried out at age of 28 days. Results have showed that the flow rate values have been reduced after replacing cement with the combination of silica fume, and glass and ceramic waste. Moreover, it has been found out that the compressive and flexure strength values for all combination mixtures have been higher than that for control mixture. The enhancement ranges have been 31% to 62% for compressive strength and 3% to 25% for flexure strength. In addition, results have demonstrated that there has been no significant change in bulk density values for cement replacement mixtures related to the one for control specimens.
Industrial waste is constantly increasing, so measures must be taken to recycle it in more practical and environmentally friendly ways. The aim of this study was to investigate the suitability of sawdust wasted particles for the production of cement bonded particleboards, and to enhance their compatibility with cement by using physical pretreatment processes, addition of nano slag and accelerated carbonation curing. All tests were carried out with different manufacturing parameters: sawdust/cement: (20%, 30% and 40%), treated and untreated wood, CO 2 curing and the addition of nano slag. Experiments were performed to assess the mechanical properties of produced particleboards such as density (D), water absorption (WA), thickness swelling (TS), bending strength (BS), and microstructural properties of the cement particleboards. For treated sawdust, the outcomes demonstrated an enhancement in the mechanical and microstructural characteristics of produced cement bonded particleboards by using the accelerated CO 2 curing method for sawdust particleboards. According to Scanning Electron Microscopy (SEM) micrographs, part of the carbonate crystals was found to be diffused into the cell walls and cavities and were found to protrude from sawdust surfaces.
The utilization of natural fiber wastes could be an ideal way to tackle two problems. Firstly, this may be a solution to the issue of environmental challenges related to agricultural wastes. Secondly, it can potentially fix high-strength concrete's (HSC) issue of unexpected (sudden) collapse. This study looked at the results of using two different kinds of natural fiber waste in HSC. Seven HSC mixtures were manufactured; three included rice straw fibers (RSF), three contained palm leaf sheath fibers (PLSF), and one was a control mix (without fibers). In this research, the volume fractions of RSF and PLSF ranged from 1% to 3% and had an aspect ratio equal to 100. Different tests, including slump test, compressive strength, modulus of elasticity, flexural strength and tensile strength were conducted to determine their various properties. There were no significant improvements on compressive strength due to use of natural fiber while its tensile and flexural strengths increased particularly when including 1% RSF. RSF improved the properties of HSC more significantly than PLSF.
This analytical study aims to investigate the flexural behavior of simply supported RC beams having longitudinal hole with circle cross section under monotonic two point loads. The commercial FE program ABAQUS was used for simulating and implementing the specimens behavior that tested experimentally in previous researches. The overall specimens investigated were thirteen RC rectangular beam specimen, the first one was solid while the others with longitudinal circular hole. The specimens with holes divided into three groups, each one has a specified hole diameter 25 mm, 40 mm, and 50 mm. The distance from center of hole to the top section face was variable where the hole would be completely in the stress block, below it, or partially within it. The validity of the simulated model were verified by comparing the available load deflection data with the implemented one, where good agreement were noticed. The simulated models could introduce the ultimate load, first cracking load and its propagation in addition to the maximum attended deflection. It is concluded that the existence of a longitudinal hole with a percentage of diameter to beam depth ratio below 20% with different positions from top surface of the cross-section to the center of the hole values caused decreasing in ultimate load not exceeding 5% compared with the solid beam.
Increased rate of seizures and respiratory complications due to tramadol poisoning have been observed, even with first time of tramadol intake. So, the present work was used to investigate the clinical manifestations and laboratory investigations of acute tramadol toxicity and the correlation between toxic tramadol manifestations and blood tramadol level and laboratory parameters. A study was performed on 100 patients (80 males and 20 females) acutely intoxicated with tramadol, admitted to toxicology unit of Al-Azhar University Hospital (New Damietta) in the period from January to December 2017. Informed consent, urine sample was collected and 10 mL of blood was separated and used for extraction of tramadol residues by using a high-performance liquid chromatography (HPLC) and other blood samples were stored at-8°C for routine investigations. Then a detailed clinical examination was done to all patients. Generally, the frequency of seizures was (46 %) with acute tramadol poisoning. There was no correlation between blood tramadol level and toxic manifestations of tramadol poisoning. So, the frequency of seizures and toxic manifestations are not dosed dependent. Cannabis was the most common co-ingested drugs and adult males were more commonly affected by tramadol poisoning. It is recommended that the drug abuse problem must be treated at the level of community problems in order to minimize medical emergencies related to acute tramadol overdose occurring mostly by addiction and further studies should be proposed to extend our knowledge about relationships between sex and seizures among tramadol intoxicated patients
