Magazine of Concrete Research最新文献

{"title":"Mechanical properties of recycled aggregate concrete containing brick particles","authors":"Yafei Zhang, Faning Dang, Xinzheng An","doi":"10.1680/jmacr.23.00134","DOIUrl":"https://doi.org/10.1680/jmacr.23.00134","url":null,"abstract":"To investigate the mechanical properties of recycled aggregate concrete containing brick particles(RACB), compressive strength tests were conducted on RACBs with different water cement ratios and recycled fine aggregate substitution rates. The changes in compressive strength, elastic modulus, and peak strain of RACB with recycled fine aggregate substitution rates were analyzed, and a stress–strain equation was established. A damage model was established using ultrasonic nondestructive testing technology to reveal the damage mechanism of RACB. Results show that the basic mechanical properties of RACB reach the best when the replacement rate of recycled fine aggregate (r) is 30%. The model parameter a of the stress–strain curve equation is consistent with the change rule of elastic modulus with r. The model parameter b has a quadratic function relationship with r, reflecting the brittleness of RACB. The initial damage of RACB is relatively large, and the cracks penetrate the recycled coarse aggregate, and lead to specimen failure.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140992343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characterisation proposal of direct shear strength of steel fibre-reinforced concrete","authors":"Aaron Kadima Lukanu Lwa Nzambi, Dênio Ramam Carvalho de Oliveira, Vander Luiz da Silva Melo, Ronnan Wembles Martins Barreira, Heber Dioney Sousa Moraes","doi":"10.1680/jmacr.23.00335","DOIUrl":"https://doi.org/10.1680/jmacr.23.00335","url":null,"abstract":"This study proposes the direct pure shear characterisation of steel fibre-reinforced concrete specimens with two grooved shear planes. Initially, the crimped fibre type was used with a rate varying between (0.0 %, 0.5 %, 1.0 %, and 1.5%), a concrete compressive strength of 35 MPa, a maximum aggregate size of 9.5 mm, and eight specimens subjected to the direct shear test. The results showed a significant gain in shear strength with increased fibre consumption, 90% at a rate of 1.5%. Based on these observations, three analytical expressions were formulated to compute the shear stress. The validation of the models was applied to a group of fifteen blocks of the same smaller size geometry and had as additional variables the hooked-end fibre, the concrete compressive strength of 25 MPa, the type and the maximum size of the coarse aggregate (19 mm and 25 mm). Crimped fibre confirmed good performance compared to the hooked-end, with a strength gain of around 100% at a rate of 1.5% with the maximum coarse aggregate particle size of 25 mm, showing variability between 2 and 7% in the proposed analytical models.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140886907","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Punching shear tests and design of UHTCC-enhanced RC slab-column joints with shear reinforcements","authors":"Zhe-Xin Yu, Gen-Shu Tong, Jing-Zhong Tong, Xiao-Ning Huang, Qing-Hua Li, Shi-Lang Xu","doi":"10.1680/jmacr.23.00362","DOIUrl":"https://doi.org/10.1680/jmacr.23.00362","url":null,"abstract":"Reinforced concrete (RC) flat slab structure may suffer progressive collapse, which is usually caused by the punching shear failure of slab-column joints. Existing research has shown that the utilization of shear reinforcements or ultra-high toughness cementitious composite (UHTCC) in slab-column joints is efficient in improving their punching shear performance. In this study, shear reinforcement was introduced into UHTCC-enhanced RC slab-column joints. Specimens of UHTCC-enhanced slab-column joints considering the effect of shear reinforcements were tested. The cracking development process, bearing capacity, and ductility were analyzed. Yield line theory and critical shear crack theory were adopted to predict flexural and punching shear capacities, respectively. Finally, the failure patterns of the specimens were discriminated by comparing the predicted punching shear and flexural capacities, taking the ductile coefficient into account. The theoretical results combined with test results show the effect of shear reinforcement on the behavior of UHTCC-enhanced joints. Significant improvement in the bearing capacity and ductility of joints is achieved by applying shear reinforcement. The failure pattern of a joint varies from premature punching shear failure to flexural-triggered punching shear failure with the application of UHTCC, and this transform is more pronounced with shear reinforcement applied into the UHTCC-enhanced joint.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140812997","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bond behaviour between steel fibre and cement mortar exposed to elevated temperature","authors":"Yuyang Pang, Qun Tang, Zhenqi Li, Danying Gao, Lin Yang, Dongxu Liu, Dawei Li","doi":"10.1680/jmacr.23.00210","DOIUrl":"https://doi.org/10.1680/jmacr.23.00210","url":null,"abstract":"In order to accurately evaluate the deterioration of the mechanical properties of steel fibre reinforced concrete (SFRC) after exposure to elevated temperature, it is particularly important to study the bonding properties between steel fibre and concrete matrix. In this paper, four types of steel fibre and five types of cement mortars with different strengths were selected to investigate the bond behaviour of the steel fibre-mortar interface after exposure to elevated temperature. The results showed that the compressive strength and flexural strength of each mortar decreased significantly after elevated temperature treatment, and the attenuation degree of flexural strength was greater than that of the compressive strength. In addition, the ultimate pull-out load of specimen with the straight steel fibre gradually decreased with the increase of temperature. However, the ultimate pull-out load of specimen with the end-hooked steel fibre had no significant change between 20°C and 400°C. When the temperature exceeded 400°C, the ultimate pull-out load gradually decreased with the increase of elevated temperature. Subsequently, the damage mechanism of the interface between steel fibre and mortar matrix under condition of elevated temperature was analyzed by testing the interfacial microstructure and phase change of cement paste. Finally, the calculation formula of the ultimate bond strength and temperature was established.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140688488","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Developing geopolymer concrete using fine recycled concrete powder and recycled aggregates","authors":"Paramveer Singh, K. Kapoor","doi":"10.1680/jmacr.23.00360","DOIUrl":"https://doi.org/10.1680/jmacr.23.00360","url":null,"abstract":"The paper investigates the efficacy of Fine Recycled Concrete Powder (FRCP) and Recycled Aggregates (RA) as partial replacements of Fly Ash (FA) and Natural Aggregates (NA) respectively to develop sustainable Geopolymer Concrete (GC). The strength of GC was measured in terms of Compression Strength. To evaluate durability performance, such as Capillary Suction Test (CST), Initial Surface of Absorption (ISA) test and Acid Attack were performed at ambient curing. The compression strength of GC made with 50% RA (both coarse and fine) along with FRCP is comparable to that of GC made with NA. Similarly, the inclusion of FRCP in GC mixes results in a pore-blocking effect to restrict the water ingress in GC through Capillary Suction and Surface Absorption even with 50% Coarse and 25% Fine RA. The study has demonstrated that sustainable GC can be developed using appropriate doses of FRCP and RA.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140704426","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Engineering and microstructural properties of self-compacting concrete containing coarse recycled concrete aggregate","authors":"Dinesh Kumar, Kanta Rao, P. Lakshmy","doi":"10.1680/jmacr.23.00338","DOIUrl":"https://doi.org/10.1680/jmacr.23.00338","url":null,"abstract":"In this paper, the possibility of utilizing coarse recycled concrete (CRCA) aggregate obtained from a Construction and Demolition Waste (CDW) Plant in Delhi for making a 60 MPa Self compacted concrete (SCC) was evaluated. The CRCA was used in as-collected condition and was not processed any further. Aggregate Packing (bulk) Density (APD) method was adopted to obtain an aggregate mixture exhibiting maximum bulk density/least void content (45%) with which the SCC-CRCA mixture was prepared. In addition, SCC was also made using aggregate mixtures in which the NCA was replaced with CRCA at 0%, 20%, and 100 % (of the total coarse aggregate content) by weight. The cement, fly ash, silica fume, and water were kept constant for all SCC mixtures. The effect of CRCA on the flow behavior, mechanical strength, shrinkage characteristics, and microstructure properties of SCC mixtures were evaluated. The test results indicated that the SCC mixtures made with CRCA up to 45% replacement can be used for structural concrete which is higher than that recommended in Indian (20 %) and International specifications (35 %) for traditionally vibrated (conventional) concrete.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140615948","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Age-dependent deflection analysis of reinforced concrete beams incorporating high volume fly ash: experimental and ANN modeling approach","authors":"A. Hashmi, M. Shariq, A. Baqi, M. Ayaz, A. Bilal","doi":"10.1680/jmacr.23.00197","DOIUrl":"https://doi.org/10.1680/jmacr.23.00197","url":null,"abstract":"The research examines the influence of high-volume fly ash (HVFA) on reinforced concrete (RC) beam deflections over 180 days of continuous loading. The study comprises eight fly ash-based concrete mixes with varying fly ash ratios (0-60%). Experimental assessments are conducted on two load levels, corresponding to 25% and 50% of the initial cracking load. Thirty-two full-scale RC beams, each measuring (100×150×1800) mm, are fabricated for both load levels. Long-term deflections are monitored for all concrete mixes through sustained four-point bending tests at ages ranging from 1 to 180 days. A comparative analysis of the overall mid-span deflection between conventional and fly ash concrete RC beams is carried out against established design codes. It has been determined that high volume fly ash RC beams exhibited lesser contribution to creep and shrinkage deflection compared with conventional RC beams. Moreover, ANN modeling has also been carried out to propose a significant model helpful in predicting the total deflection of RC beams containing any fly ash content and at any age of concrete. The present study offers valuable insights for engineers and designers, facilitating the evaluation of age-dependent deflection patterns in RC beams constructed with reinforced high-volume fly ash concrete.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140706299","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modelling chloride diffusion in concrete with carbonated surface layer","authors":"Ping Li, Chuanfei Li, Dawang Li, Runhao Chen, Jinghong Chen","doi":"10.1680/jmacr.23.00202","DOIUrl":"https://doi.org/10.1680/jmacr.23.00202","url":null,"abstract":"Due to the demand for carbon neutrality, concrete carbonation has been reconsidered as an interesting topic because of its potential for capturing CO₂ from the atmosphere. Concrete carbonation can significantly modify the chemical and microstructure properties of concrete and thus will have important effects on chloride diffusion. This paper presents a chloride diffusion model in which the concrete cover is divided into three different zones, each with their own defined porosity and chloride binding isotherm. One is the fully carbonated concrete near the surface, where the porosity and chloride binding isotherm can be obtained from the experimental data of fully carbonated concrete. One is the uncarbonated concrete near the reinforcement, where the porosity and chloride binding isotherm can be obtained from the experimental data of normal concrete. One is the transition zone between the fully carbonated and uncarbonated concretes, where the porosity and chloride binding isotherm can be assumed to vary continuously from the carbonated concrete to uncarbonated concrete. To validate the present model, the comparison of the present model with published experimental results is also provided, which demonstrates the importance of considering different zones in chloride diffusion model when the concrete has a carbonated layer near the surface.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140582430","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"From risk study to field evidence: an unprecedented and isolated case of DEF in Brazil","authors":"Igor Ferraz Torres, Sandro Marden Torres, Tibério Andrade","doi":"10.1680/jmacr.23.00272","DOIUrl":"https://doi.org/10.1680/jmacr.23.00272","url":null,"abstract":"This paper presents the first case ever reported in Brazil where delayed ettringite formation (DEF) has been confirmed as the sole cause of deterioration in field concrete. Still under construction and with less than 2 years of age, numerous cracks were observed in the foundation structures of a building located in Recife, a city known for its history of alkali-aggregate reaction (AAR) cases. In addition to the field survey of cracks, microstructural analyses, residual expansion, compressive strength, review of structural design, the determination of the sulfates content in the groundwater and simplified thermal analysis were carried out. Results confirmed that the DEF was the isolated cause of the damages present in those cast-in-place concrete structures, with no evidence of AAR or any other deterioration process. This work corroborates studies previously published on the high risk of the occurrence of DEF in the region, demonstrating the urgent need for a preventive technical standard in the country, considering the chemical composition of cements and mainly prior thermal analyzes to adopt possible preventive measures to limit the maximum internal temperature of the concrete.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140367348","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Shear friction capacity of monolithic construction joints reinforced with self-prestressing reinforcing steel bars","authors":"Yeon-Back Jung, Ju-Hyun Mun, Sanghee Kim, Seung-Hyeon Hwang, Jae-Il Sim","doi":"10.1680/jmacr.23.00317","DOIUrl":"https://doi.org/10.1680/jmacr.23.00317","url":null,"abstract":"This study examined the shear friction capacity of a monolithic concrete interface reinforced with newly developed self-prestressed reinforcing steel bars (SPRBs). Twelve push-off specimens with SPRBs were prepared according to the different compressive strengths of concrete (<i>f</i>′<i>_c</i>) by applying compressive stresses (<i>σ_x</i>) on a monolithic concrete interface. To compare the shear friction capacities of monolithic concrete interfaces reinforced with conventional reinforcing bars, four companion specimens were prepared. The test results showed that the shear cracking and shear friction capacities were high for specimens with high <i>f</i>′<i>_c</i> and <i>σ_x</i> values, resulting in the highest values for specimens with <i>f</i>′<i>_c</i> = 40 MPa and <i>σ_x</i> = 0.5<i>f_y</i>, where <i>f_y</i> is the yield strength of the reinforcing steel bar. The test results confirmed that at a similar (<i>ρ_vff_y</i>+<i>σ_x</i>)/<i>f</i>′<i>_c</i>, a <i>σ_x</i> of more than 0.35<i>f_y</i> is required for the SPRBs to achieve a <i>λ_n</i> value comparable to that of the specimens reinforced with conventional reinforcing bars, where <i>ρ_vf</i> is the transverse reinforcement ratio and <i>λ_n</i> is the shear friction capacity. The prediction models ACI 318-19 and AASHTO significantly underestimated the shear friction capacity with low accuracies. In particular, the difference between the experimental and underpredicted values became large as the (<i>ρ_vff_y</i>+<i>σ_x</i>)/<i>f</i>′<i>_c</i> value increased. However, the Mattock's model well-estimated the measured shear friction capacities of all the specimens tested in this study, irrespective of <i>ρ_vff_y</i> and <i>σ_x</i>. Thus, the mean and standard deviation values of the measured-to-predicted shear friction capacity ratio were 1.07 and 0.13, respectively.","PeriodicalId":18113,"journal":{"name":"Magazine of Concrete Research","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140317005","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}