The use of cement in construction causes large amounts of CO2 emissions into the atmosphere. Moreover, the use of large amounts of natural coarse aggregate causes environmental damage, and the ...availability of such natural aggregate is also depleting. The present experimental study explores and optimizes the impact of various parameters on the fresh, mechanical, and durability properties of recycled waste concrete coarse aggregate (RWCA)-based geopolymer concrete (GPC) in combination with ground-granulated blast furnace slag (GGBFS) and fly ash (FA) using the Taguchi-Grey Relational Analysis Method (TGRAM). The coarse aggregates in GPC were fully replaced with RWCA produced by crushing waste concrete. The effects of FA inclusion (%), Na2SiO3/NaOH ratio (SS/SH), molarity of NaOH (SH), dosages of superplasticizer (%), and alkaline solution to binder (Al/Bi) ratio are investigated under ambient curing conditions. The obtained maximum compressive strength and split tensile strength along with minimum water absorption of GPC at 28 days were 67.90 MPa, 3.85 MPa and 2.92 % respectively. The microstructural studies of GPC having low, high, and optimal strength are carried out using XRD, FE-SEM, and EDAX analysis. These studies confirmed the presence of calcium-based hydration products such as CSH and N(C)ASH, which makes the matrix of optimized GPC more compact.
•This paper explores and optimizes the mix composition of GGBFS-FA based GPC using TGRAM.•FA inclusion had a dominant effect on flow value, mechanical strength, and water absorption of GPC.•Microstructure analysis shows the presence of N-(C)-S-H and C-S-H-based hydration products in GPC.•Confirmation test on optimized GPC confirmed competence of TGRAM.
The effective way of recycling waste polyethylene terephthalate (PET) by exposing it to gamma rays, is adopted in formulating the compositions of cementitious grouts for semi-flexible pavement ...surfaces. The ordinary Portland cement in grouts was partially replaced by regular PET (2.5%–10%) and irradiated PET (2.5%–10%) combined with fly ash (FA) and silica fume (SF). The physical, mechanical, and microstructural characteristics of grouts were investigated, and the results achieved from regular and irradiated PET substituted cement gouts were used to develop single hidden layers (SHLs) and two hidden layers (THLs) neural network models. The test results show that replacing cement with regular PET or irradiated PET caused a significant increase in the flow value of cement grouts. When using regular PET, compressive strength is significantly reduced at all curing ages (53–78% at 1 d, 24%–46% at 7 d, and 23%–36% at 28 d). Some of the strength was restored when irradiated PET was used (the recovery is 20–30% at 1 d, 17–24% at 7 d, and 7–12% at 28 d). The pozzolanic characteristics of FA and SF led to an increase in compressive strength. The microstructural analysis by FESEM-EDX and XRD confirms that the irradiated PET causes densification and refinement of microstructure. The statistical evaluation using R, MAE, RMSE, and RSE reflects a close agreement of actual values to the predicted results for the developed ANN models. The proximal values of objective functions to zero represents no overfitting of the trained models. The value of R for all the developed models is ≥ 0.91, which depicts a strong correlation between experimental and predicted results of flow and compressive strength. It is possible to conclude that with the irradiation process, more waste PET can be recycled than regular PET while still achieving similar strength properties, thus providing a sustainable solution to the recycling of waste PET.
Construction projects result in the generation of wastes, which can be broadly classified into physical and non-physical wastes. Non-physical wastes present a different challenge than physical waste ...due to their intangible nature. This study focuses on understanding the importance of the classical Lean Construction (LC) wastes and their degree of influence on the Transformation-Flow-Value (TFV) aspects of construction projects using empirical data. A structured questionnaire was designed and completed by 60 participants from the public and private sectors in Nigeria and analyzed using the Relative Importance Index (RII). The statistical analysis indicated that 'Making-Do' is the most critical non-physical waste during the transformation process of construction, followed closely by 'Non-Utilized Talent'. 'Waiting' and 'Transportation' are the two most essential aspects in the flow aspect of construction, while 'Overproduction' is the most crucial waste category affecting the value aspect of construction. The findings of this study can be used for improving the productivity of construction projects by focusing on techniques to reduce the most critical non-physical wastes.
Faced with increasingly strict carbon surveillance from carbon-related laws and regulations, it has become urgent for high-emission enterprises to find effective methods by which to reduce carbon ...emissions and control carbon emission costs. However, although carbon emission costs are closely related to the production process, current costing methods only pay more attention to the total cost amount rather than to the cost generation process. Therefore, this study aims to develop a carbon emission costing method based on carbon value flows analysis (CVFA) by tracing carbon element flow and accounting for carbon emission monetary value simultaneously. To verify the rationality and effectiveness of this method, this article also implements it in a case company. The results indicate that carbon emissions were reduced by 405,021.97 tons, and RMB 107,300,000 ($15,670,000) was saved through conducting optimized analysis. It is proved that the CVFA method is particularly suitable for process manufacturing enterprises. However, certain conditions are required to apply CVFA, such as the availability of compulsory carbon information disclosure regulations. Also, improving managers’ carbon resources investment decision-making capacity can reduce more carbon emissions and save more carbon emission costs.
•The first project in China to build an island by solidification of waste dredged silt.•Quality control indicators for solidifying silt of artificial island are derived.•The law relating fluidity and ...strength of solidified silt is summarized.•The priority of two silt-cement mixing methods in the projects is discussed.•Curing agent values for two silt-cement mixing methods are discussed.
The artificial island of the Dalian Bay Cross-sea Traffic Engineering Project is the first project in China to use solidified waste dredged soil. The selections of quality control indexes and the suitable silt-cement mixing method for solidified silt island are unclear. We present tests for the curing agent values of different mixing methods, and the compression and permeability characteristics of solidified silt. While the curing agent values for an artificial island is obtained, the selection of mixing method and the primary quality control indicators are discussed, thus providing a reference for similar projects.
Concrete, an indispensable cornerstone of the construction industry, presents a formidable environmental challenge owing to the substantial carbon dioxide (CO
2
) emissions incurred during the ...production of cement. However, in light of the construction sector’s vital economic and social contributions, it becomes imperative to harmonize it with environmental preservation. The concept of sustainability emerges as a paramount principle, addressing pressing issues such as the escalating depletion of non-renewable resources and the imperative need for resource conservation to secure a sustainable legacy for future generations. In this particular context, the prudent utilization of sustainable materials stands out as a pragmatic approach to ameliorate the adverse environmental impacts inherent in cementitious systems, while concurrently enhancing the structural strength and durability of constructions. The subject of this study is centered on the strategic incorporation of recycled concrete powder (RCP), marble powder (MP), glass powder (GP), and limestone powder (LP) as viable substitutes for traditional cement, at varying rates of 25%, 30%, and 35%, with the overarching goal of augmenting sustainability in construction practices. The outcomes of the experimental investigation unveiled significant insights. The inclusion of these waste powders yielded a noteworthy maximum reduction of 44% in compressive strength, albeit it necessitated a maximum increase of 16% in the application of admixtures. Nevertheless, a crucial advantage emerged in the substantial reduction, to the tune of 72%, in the deleterious alkali–silica reaction. Moreover, in terms of workability, while the control mixture experienced a 20% reduction in flow value after 60 min, mixtures infused with waste powders showcased a range of flow value reductions spanning from 23 to 40%. In summary, the study emphasizes that the replacement of conventional cement with waste powders, despite causing acceptable adverse effects on workability, admixture requirements, and strength properties, leads to significant enhancements in alkali-silica reaction resistance. This, in turn, bestows substantive benefits upon the overarching goal of sustainability enhancement within the construction industry.
The influence of the mortar flow value and the effect of the retarding effect of chemical admixtures on the activity index test results were investigated. The main conclusions are as follows. 1) The ...value of the mortar flow in the activity index test influences the increase or decrease of the air content of the fresh mortar. As a result, the value of mortar flow indirectly affects the compressive strength of mortar. 2) It was considered that the setting retardation effect caused by the type and amount of chemical admixture had little effect on results of the activity index test.
Fibers which are used to increase the tensile strength of cementitious systems adversely affect the fluidity by making the mixture more cohesive. The effect of fiber type and utilization rate on the ...rheological and thixotropic characteristics of cementitious systems was a topic covered in the current study. For this, mortar mixtures containing polypropylene, polyamide (PA), and basalt fibers with a 6 mm length were created in three different ratios (0.25%, 0.50%, and 0.75%). According to results, PA- and basalt fiber-containing mixtures showed the best and worst performances, in terms of flowability performance, respectively. In fiber mixes including basalt, the maximum dynamic yield stress (DYS) value was identified. The use of high-range water-reducing admixtures and an increase in the water/cement ratio were shown to result in a drop in the values of DYS, apparent viscosity, the Herschel–Buckley Index, and structural recovery area. It was discovered that fibrous mixtures had a larger structural recovery (anti-thixotropic) area than fiber-free ones.
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