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The exposure of concrete or cement mortars to fire or other elevated temperatures negatively affects the mechanical properties, and a change may also occur in the pore structures, leading to cracking and spalling. In order to hinder or reduce the negative impact of elevated temperature on cement mortar, as well as to promote reuse of waste in the concrete industry to improve the environment, this study aims to investigate the effect of elevated temperature on the mechanical properties of cement mortar reinforced with rope waste fibres (RWF). The fibres were obtained by cutting a used polymeric rope (0.034 mm in diameter) into small fibres with average lengths of 12 mm. Four mortar mixtures, including one reference mixture (without fibres) and three mixtures containing RWF in proportions of 0.25%, 0.5% and 0.75% (by mortar weight), were cast. After 28 days of curing, the hardened specimens were air dried for at least two weeks, and some specimens were exposed to a controlled temperatures of 300 and 600 °C for two hours, while the others were placed at ambient temperature. All specimens were then examined via compressive strength, flexural strength, mass loss, ultrasonic pulse velocity and visual inspection tests. The results indicated that RWF can prevent cracks appearing at 600 °C; however, the RWF had a negative impact on the compressive strength of the mortar under elevated temperatures, despite the flexural strength and UPV properties being improved significantly.

The present study involved assessing the replacement of fine aggregate in the mortar with sustainable local materials like clay bricks and glass included 168 specimens (cubes and prisms). Seven mixtures were cast for this work, one control mix (R1) with 100% natural sand whereas mixes from R2 to R5 have 10% and 20% replacing natural sand with waste clay bricks and waste glass separately and respectively. Mix R6 was included 20% replacing sand with combination waste materials (10% waste clay bricks with 10% waste glass). Mix R7 has involved the same percent of replacing the previous mix R6 but with adding Polypropylene fibers 1% by volume. The samples have put in an electrical oven for one hour at 200, 400, and 600 ᵒC then cooled to room temperature to be tested and compared with samples at normal temperature 24 ᵒC. Different mechanical tests were adopted involved flow tests, density, weight loss, compressive strength, flexural strength, and water absorption. The results at different temperatures were discussed where many findings were specified. The flexural strength at 400 ᵒC was showed improving by 56% for 20% waste clay brick and 69% with 10% waste glass, as well all combination mixes illustrated higher strength than the control. Doi: 10.28991/cej-2021-03091729 Full Text: PDF

This study presents a computer program designed in Visual Basic 6 program. The capability of this program is to design wastewater treatment plant units and determination of its construction cost. The program deals with two types of wasted sludge the first type is wasted sludge from the aeration basin, while the second system is wasted sludge from the secondary clarifier. Also, there is a detailed output shows the design flowrate, mass balance analysis and composition of each stream in and out of each treatment unit. Program results are verified with hand calculations within the allowable recommended values and they showed a good accuracy. The volume of aeration basin and secondary sedimentation tank increased with the elimination of primary sedimentation tank from the design of the wastewater treatment plant. Generally, an increment of about (52-170) % for aeration basins and (58-185) % for secondary sedimentation tanks are observed in the present study. From other hand, gravity thickener volume is decreased by (29-42) %, anaerobic digester volume is decreased about (38-52) % and drying beds is decreased by (29-38) % approximately. The cost analysis showed that the cost of a wastewater treatment plant is increased after a certain amount of influent. That amount is nearly (36,708.33) m 3 /d when wasted sludge is taken from aeration basin and (24,833.33) m3/d when wasted sludge is taken from secondary clarifier.

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