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For decades, ferrocement has been used to repair, strengthen, and even build structural components because it is a long-lasting and reasonably priced material. However, onsite ferrocement jacketing is time-consuming and labour-intensive. Alternatively, prefabricated ferrocement jacket installation eliminates these shortcomings. Therefore, this study utilises wearable prefabricated ferrocement jackets to repair and strengthen axially loaded sub-standard low-strength concrete elements. In order to repair cracked specimens and strengthen existing intact specimens, two types of wearable prefabricated jackets are proposed, 'L' shape and 'U' shape. Besides a control specimen, two preloaded and two unloaded square concrete specimens were utilised to repair and strengthen using the Prefabricated Ferrocement Jacketing system. The test results and crack patterns show that all the jacketed specimens performed better than the control specimens in terms of load-bearing capacity, ultimate axial and lateral deflection, and ductility. In terms of load-bearing capacity, the unloaded strengthened specimens showed significant results consistently. Based on the results, the proposed solutions were found to be effective in solving the problem of typical square ferrocement jackets. [ABSTRACT FROM AUTHOR]

This study evaluated the effect of alum sludge as an alternative to fly ash in fabricating geopolymer paste and mortar. The blending of this industrial waste (alum sludge and fly ash) is not only for the benefit of sustainable construction and disposal of industrial waste but also for the reduction of CO2 emissions due to the increasing production of Portland cement from the cement production industry. A laboratory investigation was carried out on the workability and mechanical properties of geopolymer paste and mortar produced with alum sludge replacement in different proportions (0, 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100). A combination of an alkaline solution of sodium silicate and sodium hydroxide of 14 molarity was employed as an activator for the manufacturing of both paste and mortar geopolymer specimens. It was observed from the findings that geopolymer paste and mortar was flowable and workable when alum sludge is replaced for fly ash at higher replacement content. The addition of alum sludge to the mix improved some properties such as density, strength, water absorption, and the elevated temperature behavior. It was observed that the addition of alum sludge was optimum at the 50% replacement level. The addition of alum sludge up to 50% significantly increased the compressive strength of mortar (up to 80% increase in 28 days strength). The compressive strength of the paste and mortar increased with an increase in curing age. Thus, alum sludge and fly ash can be employed together in the production of eco-friendly cementing material for environmental sustainability. [ABSTRACT FROM AUTHOR]

Bagasse is produced as a waste in the sugar production process, which is used as fuel to stoke boilers in the sugar mills. The concluding product of this burning is residual sugarcane bagasse ash (BA), which is normally dumped or used as low-quality fertilizer. The ash for this study was collected from a reputed sugar mill located in the northern region of Bangladesh. Type I Portland cement (PC) was partially replaced with that finely ground bagasse ash without any pretreatment. The ground BA was used as a replacement for Portland cement at 5, 10, 15, 20, 25 and 30% of BA, respectively, in structural mortar. In addition, chemical characterization, specific gravity, X-ray diffraction (XRD), scanning electron microscopy (SEM), setting time, a strength activity index, compressive strength, water absorption, density and durability in a chloride environment of mortar were determined. The strength activity index result indicates that the used BA has the pozzolanic properties to be used as a partial cement replacement. The results showed that, at the age of 56 days, the mortar samples containing 5–15% ground bagasse ash had higher compressive strengths than the control mixture (mortar without ground bagasse ash). Mortar containing 15% ground bagasse ash had the highest mechanical and durability properties. Therefore, the substitution of 15% BA is acceptable for producing good quality structural mortar in the civil engineering construction field except in chloride environments. [ABSTRACT FROM AUTHOR]

Recently, as a supplement of cement, the utilization of pozzolanic materials in cement and concrete manufacturing has increased significantly. This study investigates the scope to use pozzolanic wastes (slag, palm oil fuel ash and rice husk ash) as an alkali activated binder (AAB) that can be used as an alternative to cement. To activate these materials, sodium hydroxide solution was used at 1.0, 2.5 and 5.0 molar concentration added into the mortar, separately. The required solution was used to maintain the flow of mortar at 110% ± 5%. The consistency and setting time of the AAB-paste were determined. Mortar was tested for its flow, compressive strength, porosity, water absorption and thermal resistance (heating at 700 °C) and investigated by scanning electron microscopy. The experimental results reveal that AAB-mortar exhibits less flow than that of ordinary Portland cement (OPC). Surprisingly, AAB-mortars (with 2.5 molar solution) achieved a compressive strength of 34.3 MPa at 28 days, while OPC shows that of 43.9 MPa under the same conditions. Although water absorption and porosity of the AAB-mortar are slightly high, it shows excellent thermal resistance compared to OPC. Therefore, based on the test results, it can be concluded that in the presence of a chemical activator, the aforementioned pozzolans can be used as an alternative material for cement. [ABSTRACT FROM AUTHOR]

Schmidt rebound hammer test was employed in this study as a nondestructive test. This test method has been universally utilized due to its non-destructiveness for quick and easy assessment of material strength properties and quality of concrete of an existing structure. Industrial waste materials (air-dried alum sludge, treated alum sludge, limestone dust and quarry dust) were employed as replacement material for fine aggregates in this study. A normal strength concrete was designed to achieve 35 MPa at 28 days, with industrial waste materials replacing fine aggregate at different percentages (0%, 5%, 10% and 15%), and then cured for 7, 28 and 180 days. The compressive strength values and rebound numbers for all the mixes obtained were correlated, and a regression equation was established between compressive strength and Schmidt rebound number. The correlation result showed an excellent relationship between rebound number and compressive strength of concrete produced in this study at all curing ages, with correlation coefficients of R2 = 0.98, R2 = 0.99 and R2 = 0.98. The predicted equation showed a strong relationship with the experimental compressive strength. Therefore, it can be used for the prediction of compressive strength of concrete with industrial waste as a replacement for fine aggregate. [ABSTRACT FROM AUTHOR]

Existing assessment tools have not been successfully used to evaluate the performance of the remedial treatment of concrete flat roofs by building users or building management personnel because they are complicated and difficult to be applied by non-experts. In this study, a semi-quantitative method has been developed to assess the quality of remedial treatment on concrete flat roofs of multiple buildings. A 10-point scale weighting was calculated based on the results of ranking, and then the score assessment scheme was developed. Results revealed that the repairing principles included protection against ingress (W = 7.25), physical resistance against ingress (W = 5.23), concrete restoration (W = 8.22), structural strengthening (W = 8.22), moisture control (W = 6.59), and chemical resistance (W = 4.57). The grouped principles included physical resistance (W = 6.24), structural stability (W = 8.22), and chemical resistance (W = 5.58). The scoring assessment scheme was applied to a remedial treatment on multilayer concrete flat roof which was treated with bituminous membrane. The assessment scheme was revised based on the surveyors' comments and then verified by the experts. This assessment method secured and improved the quality of the remedial treatment, since the building management staff/owner successfully evaluated, controlled, and monitored the quality of remedial treatments. [ABSTRACT FROM AUTHOR]

Recently, as a supplement of cement, the utilization of pozzolanic materials in cement and concrete manufacturing has increased significantly. This study investigates the scope to use pozzolanic wastes (slag, palm oil fuel ash and rice husk ash) as an alkali activated binder (AAB) that can be used as an alternative to cement. To activate these materials, sodium hydroxide solution was used at 1.0, 2.5 and 5.0 molar concentration added into the mortar, separately. The required solution was used to maintain the flow of mortar at 110% ± 5%. The consistency and setting time of the AAB-paste were determined. Mortar was tested for its flow, compressive strength, porosity, water absorption and thermal resistance (heating at 700 °C) and investigated by scanning electron microscopy. The experimental results reveal that AAB-mortar exhibits less flow than that of ordinary Portland cement (OPC). Surprisingly, AAB-mortars (with 2.5 molar solution) achieved a compressive strength of 34.3 MPa at 28 days, while OPC shows that of 43.9 MPa under the same conditions. Although water absorption and porosity of the AAB-mortar are slightly high, it shows excellent thermal resistance compared to OPC. Therefore, based on the test results, it can be concluded that in the presence of a chemical activator, the aforementioned pozzolans can be used as an alternative material for cement.