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In this paper, the compressive strength experiment for three groups of recycled aggregate concrete (RAC) specimens with different replacement ratios of recycled aggregate (0%, 50%, 100%) was carried out. The mechanism of the block and mortar properties on the compressive strength of block masonry was investigated by means of a static loading test....
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... from a franchiser in Xi'an, China. NCA was crushed limestone with a nominal size of 5-10 mm and the size range was the same as RCA. The river sand was used as FA with the water absorption and fineness modulus of 1.02% and 2.18, respectively. The size distributions Appl. Sci. 2019, 9,4870 3 of 15 of coarse aggregates are illustrated in Figure 1. The aggregates employed in this research demonstrate a continuous grain curve and conforms to Chinese standard JGJ 52-2006 [24]. The physical properties of the employed NCA and RCA were tested according to Chinese standard GB/T 14685-2011 [25] and are listed in Table 1. The results show that RCAs have a higher crushing value and water absorption compared to NCAs, which may be attributed to the old adhered mortar. Appl. Sci. 2019, 9, x FOR PEER REVIEW 3 of 15 research demonstrate a continuous grain curve and conforms to Chinese standard JGJ 52-2006 [24]. The physical properties of the employed NCA and RCA were tested according to Chinese standard GB/T 14685-2011 [25] and are listed in Table 1. The results show that RCAs have a higher crushing ...Context 2
... to Chinese standard JGJ 52-2006 [24]. The physical properties of the employed NCA and RCA were tested according to Chinese standard GB/T 14685-2011 [25] and are listed in Table 1. The results show that RCAs have a higher crushing value and water absorption compared to NCAs, which may be attributed to the old adhered mortar. Appl. Sci. 2019, 9, x FOR PEER REVIEW 3 of 15 research demonstrate a continuous grain curve and conforms to Chinese standard JGJ 52-2006 [24]. The physical properties of the employed NCA and RCA were tested according to Chinese standard GB/T 14685-2011 [25] and are listed in Table 1. The results show that RCAs have a higher crushing value and water absorption compared to NCAs, which may be attributed to the old adhered mortar. The three types of mixture proportions were used in the study with the RA replacement ratios of 0%, 50%, and 100%, respectively (by weight). The workability of mixture was guaranteed by means of additional water. The mixture proportions for concrete hollow block are summarized ...Context 3
... workability of mixture was guaranteed by means of additional water. The mixture proportions for concrete hollow block are summarized in Table 2. Cement FA NA RA 0 1.5 190 380 633 1232 -50 3.5 239 380 633 616 616 100 5.0 276 380 633 -1232 Three types of RAC hollow blocks were fabricated with the RA replacement ratio of 0%, 50%, and 100%, respectively, and the strength grades of corresponding block were MU10, MU7.5, and MU5. The commonly employed block with dimensions of 390 mm × 240 mm × 190 mm and a half block with dimensions of 190 mm × 240 mm × 190 mm were used as the bond characteristic test piece, as presented in Figure 2. The volume percentages of the vertical holes for whole and half concrete hollow blocks were 33.8% and 33.9%. ...Context 4
... were used in the study with the RA replacement ratios of 0%, 50%, and 100%, respectively (by weight). The workability of mixture was guaranteed by means of additional water. The mixture proportions for concrete hollow block are summarized in Table 2. Cement FA NA RA 0 1.5 190 380 633 1232 -50 3.5 239 380 633 616 616 100 5.0 276 380 633 -1232 Three types of RAC hollow blocks were fabricated with the RA replacement ratio of 0%, 50%, and 100%, respectively, and the strength grades of corresponding block were MU10, MU7.5, and MU5. The commonly employed block with dimensions of 390 mm × 240 mm × 190 mm and a half block with dimensions of 190 mm × 240 mm × 190 mm were used as the bond characteristic test piece, as presented in Figure 2. The volume percentages of the vertical holes for whole and half concrete hollow blocks were 33.8% and 33.9%. The RAC block masonry was prepared in accordance with standard test methods for basic mechanical properties of masonry GB/T 5129-2011 [26]. The thickness of mortar joint was 10 mm. Compressive ...Context 5
... B-0 B-50 B-100 C1 Cement 280 280 280 NA 3.8 1.9 -RA -2 It can be understood from Table 7 that the production process of aggregates and the transportation of materials were main factors leading to differences in carbon emissions between NAC and RAC blocks. The total GWP for RAC block (with recycled aggregate replacement ratio was 100%) was 7.2% lower than that of NAC block. ...Similar publications
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Citations
... The notation for the test beam was RCA replacement ratios-steel bar grade. For instance, 50%-CRB600H denoted a CRB600H reinforced concrete beam with 50% recycled aggregate The impact of transportation on the environment of reinforced concrete beams cannot be overlooked, as transportation was one of the major variables impacting the environment of concrete [79,80]. The pre-production transportation phase includes the transportation of nonrecycled materials (cement, sand, reinforcement and NCA from the factory or extraction site to the prefabricated component factory) and recycled materials (RCA from the recycling factory to the prefabricated component factory). ...
This paper addresses the urgent need for high-performance, eco-friendly construction materials due to increasing urbanization. It introduces CRB600H high-strength reinforcement to enhance recycled aggregate concrete (RAC) beam performance. Comparative analysis with conventional concrete (CC) beams demonstrates RAC's inferior shear performance, which CRB600H reinforcement effectively improves. A novel optimization method for high-strength reinforcement is established based on equal strength principles, demonstrating cost-efficiency. Economic analysis reveals that despite rising production costs with increased recycled aggregate replacement ratios, CRB600H reinforcement substantially reduces expenses, even when more expensive than HRB400 reinforcement. The environmental analysis reveals that the CRB600H reinforcement significantly influences the environmental performance of reinforced concrete beams. Utilizing 100% RAC beam with CRB600H as an illustrative example, the contribution rates of steel bars to Global Warming Potential (GWP), Acidification Potential (AP), Eutrophication Potential (EP), and Cumulative Energy Demand (CED) are determined as 39.30%, 56.85%, 51.87%, and 55.76%, respectively. In comparison to CC beam with HRB400, the 100% RAC beam with CRB600H exhibit reductions of 10.27%, 18.59%, 19.03%, and 16.93% in terms of GWP, AP, EP, and CED, respectively. In conclusion, CRB600H reinforcement offers cost-effective, eco-friendly solutions, promising significant advancements in RAC applications.
... It is clear from table 1 that the CRCAs used in most of the reported investigations in the literature were sourced from C&D wastes. However, Zhao et al., 14 Reddy and Reddy, 20 and Liu et al. 23 report that CRCAs were sourced from concrete plant waste. It is well known that CRCAs have a lower density, greater water absorption, and higher crushing strength than natural aggregates due to the presence of cement mortar. ...
... The rest of the investigations used the weight mixing method in proportioning the mix ingredients. The CRCAs used in five investigations 15,17,18,22,23 were introduced to the mixes in dry conditions, which necessitated using higher water content in RCA block mixes. In three investigations, 15,17,18 higher cement contents (an additional 10% to 25%) were used in the RCA block mixes to allow the production of concrete blocks with strength characteristics similar to those of concrete blocks with natural aggregates. ...
... Figure 3 depicts the test results of the hardened density of concrete blocks manufactured with CRCA as reported by multiple investigations. [17][18][19][20][21]23 It can be seen in figure 3 that the hardened density of concrete masonry reduces as the CRCA replacement ratio increases, with the reduction being more profound for the 100% replacement ratio. The only exception to this trend was noticed by Matar and El Dalati, 17,18 who reported slight increases in the hardened density of masonry made with 30% and 50% CRCA replacement ratios. ...
Concrete block masonry units (CBMUs) are the most commonly used building
material in the construction industry. However, CBMUs are still produced from
conventional materials like natural aggregates. Aggregate materials normally
occupy about 70% of the CBMU volume. The excessive extraction of virgin aggregate depletes natural resources, destroys the habitats of many species, and
affects the natural flow of streams in water bodies. At the same time, the amount
of solid waste, including construction waste from the demolition of old buildings,
continues to increase, leading to higher costs for disposing of these wastes in increasingly scarce landfill sites. One solution to address the growing solid waste
challenge and to preserve natural aggregate resources from depletion is the
adoption of large-scale recycling of glass, plastic, rubber, construction and
demolition, and other solid wastes into aggregate that can be used in the production
of CBMUs. This study presents a critical review of the latest research on
using recycled aggregates in CBMU manufacturing. The physical, mechanical,
and durability properties of CBMUs that incorporated recycled aggregates were
extensively analyzed, and concluding remarks and practical recommendations
were drawn. This review work shows that advancing the incorporation of
recycled aggregates in the manufacture of CBMUs needs additional concerted
efforts in terms of research work, standards and codes of practice, education,
and public awareness.
... Recently, the manufacture of such components has evolved based on environmental requirements. The mechanical performance and environmental benefits of recycled aggregate concrete hollow blocks were studied and guides for design were also proposed in [7]. Tall buildings are some of the most emblematic architectural structures. ...
This Special Issue on “Architectural Structure” aims to gather general advances in human-made constructions which simultaneously are driven by aesthetic and structural engineering considerations [...]
Carbon emission calculation during power transmission and substation construction provides valuable insights into the trend of carbon emissions and the development of low-carbon power grids. In this regard, this study divides the power transmission and substation construction process into production, transportation, and construction stages based on the sources of carbon emissions and employs a life cycle assessment to calculate the total carbon emissions using the carbon emission factor method for typical 500 kV projects. The results show that in the construction process the production stage contributes the most carbon emissions, with material and equipment production for power transmission accounting for 78% and 14% of the total emissions, respectively. The transportation and construction stage contribute 1% and 7% of the total emissions, respectively. For substations, material and equipment production contribute 67% and 30% of the total emissions, respectively. The transportation and construction phases contribute 1% and 2% of the total emissions. Through the qualitative and quantitative analysis of the carbon emission results, the construction scale and the topography and geology have significant impacts on carbon emissions from power transmission and substation projects. Finally, some targeted recommendations for carbon emission reduction for power transmissions and substations are proposed based on the influencing factors of each stage of the construction.
There are growing stockpiles of industrial by-products world-wide, and Australia is not an exception. Recycling industrial by-products in an innovative way is a common challenge faced by many industries. “Nu-Rock” is a one of the reliable solutions to the industrial by-product dilemma by converting waste from coal fired power stations into a range of unique and superior masonry products for the construction industry. Nu-Rock produces a range of building products including common or rendered bricks and blocks, masonry bricks, blocks, pipes, pavers, tiles, and sheeted products. This research study conducted a detailed, and robust life-cycle analysis from cradle-to-cradle considering two parameters: cost and environmental impacts. A model has been prepared using GaBi 8.0 software for calculating the climate change and ozone depletion potential. The life-cycle cost analysis calculated the current and likely future expenditure arising from block manufacturing process focusing on Nu-Rock and the customers/end-users. Nu-Rock technology can process approximately 250,000 tonnes of ash per annum and manufacture the equivalent of up to 330,000 tonnes volume of traditional building materials. The selling price of Nu-Rock brick fall within the rage of a common brick in Sydney, Australia. The only difference between Nu-Rock blocks and common bricks is that Nu-Rock blocks derive a waste range of environmental benefits. Nu-Rock blocks emit carbon emissions approximately 27kg CO2-eq per tonne during the raw material extraction phase although for a conventional block it ranges from 67-113 kg CO2-e per tonne.
Recycled aggregate concrete (RAC) is expected to a sustainable solution to alter the virgin aggregate concrete (VAC) in structural use. While it is able to address environmental issues for both virgin aggregate (VA) consumption and waste generation, not so many studies quantify the environmental burdens through life cycle assessment (LCA). RAC is a composite material, which LCA should be analysed by considering its mixtures, and corresponding production technologies. This aggravates the complexity of LCA model since it involves great numbers of unit processes. Through reviewing 90 articles, this paper overviews the developments of LCA for RAC, and identifies the research trend shifts with the promotion of RAC technology. Although many relevant studies have become more comprehensive, there are still numerous inconsistencies and uncertainties existing in LCA processes that avoid LCA results from comparisons. From the review, it clearly points out that results are greatly affected by two aspects that are mix design and LCA mechanism. Cement production has the predominant contribution to the environmental impacts of concrete, and normally followed by transportation process. Accordingly, mix design, together with treatment technology of raw materials, influence the overall environmental performance of concrete. With respect to LCA phases, selections of FU, system boundary, allocation rule, LCI and LCIA methodology are highly subjective, causing more uncertainties that hinder the comparisons across the studies. It is therefore suggested that variations of mix design and inconsistencies from LCA mechanism could be explored further in the field of RAC to establish the holistic and multi-criteria study for comparison and decision making.
Comprehensively considering the positive contribution of energy conservation and the reduction of the construction skill requirement for workers, a new type of interlocking hollow block using recycled aggregates concrete (IHAC) with the compressive strength defined as MU10 was proposed, which could help improve more than 56% of the construction efficiency compared to common used concrete hollow blocks. In order to study the shear properties and promote its application in building engineering, the shear strength of 10 groups (three specimens for each group) of masonries considering different axial stress level and whether or not to use concrete in the grouting holes were studied, and the failure mode as well as the shear strength of the masonries were analyzed. And then, the calculation formulas for predicting the shear strength of the IHAC masonry were obtained by using the parameter fitting method based on the Coulomb failure theory, which could well reflect the parabolic shaped changing characteristic of the shear strength with the increasing of the axial stress, and the maximum difference was within 18% between the calculated and test results.
