Issue 49

Y. Liu et alii, Frattura ed Integrità Strutturale, 49 (2019) 714-724; DOI: 10.3221/IGF-ESIS.49.64 723 compression load proposed in this study, the carbonization damage degree of the lower part can be derived from the data obtained from the upper part of the block. This not only makes the operation easy but also ensures the accuracy of the data. However, it should be noted that the compression zone of the concrete will be crushed and nearly damaged under high pressure, which will show different carbonization performance from those in the study, so the carbonization influence coefficient is only applicable under 0%-60% of the ultimate bending load level. C ONCLUSION n this study, a long-term bending load device was developed to explore how the pouring surface and bending load affect the carbonization resistance of reinforced concrete under rapid carbonization. In addition, the relationship between the bending-tension and bending-compression loads with respect to their effects on the carbonization damage of test blocks was also investigated. The following conclusions are drawn: (1) There is less coarse aggregate in the reinforced concrete pouring surface than at the same position in the bottom surface, with poorer compactness and lower carbonization resistance. The effect of the pouring surface is greater than that without fly ash on the carbonization resistance of fly ash concrete. (2) When the fly ash content is constant, the bending-compression load has a significant effect on the carbonization of reinforced concrete blocks. The larger the bending load is, the smaller the carbonization depth will be. The carbonization influence coefficient of the bending-compression load and the bending load stress level follows a second-order polynomial relationship. (3) When the fly ash content is constant, the bending-tension load has a significant effect on the carbonization of reinforced concrete blocks. The larger the bending load is, the greater the carbonization depth will be, which is typical under 40%-60% of the ultimate bending load. There is an exponential relationship between the carbonization influence coefficient of bending-tension load and the bending load stress level. (4) The carbonization influence coefficient of bending tension-compression load of reinforced concrete under the bending load is defined. There is a second-order polynomial relationship between the carbonization influence coefficient of bending tension-compression load and the bending load stress level. In practical engineering, for those parts of the buildings that are difficult to measure, the degree of carbonization damage can be estimated using the carbonization influence coefficient. It provides scientific guidance for the detection and evaluation of carbonization damages in concrete structures. A CKNOWLEDGEMENTS his research is supported by Provincial Nature Science Foundation of Hebei Province: Study on concrete structure durability based on multi-factor coupling effect (NO. E2015204111) and Key Projects of Provincial Education Department of Hebei Province: Study on durability of existing concrete structures under loading (NO. ZD2016037) and Technology Foundation of Agricultural University of Hebei (No. LG201808). R EFERENCE [1] Grzegorz, L.G. (2017). Improve of fracture toughness of green concrete as a result of addition of coal fly ash. Characterization of fly ash, Materials Characterization, 134, pp. 335-346. [2] Harilal, M., Rathish, V.R., Anandkumar, B. (2019). High performance green concrete (HPGC)with improved strength and chloride ion penetration resistance by synergistic action of fly ash, nanoparticles and corrosion inhibitor, Construction and Building Materials, 198, pp. 299-312. [3] Zheng, L., Xia, Z., Zhang, X.Y. (2018). Comparison between geopolymer reaction and cement hydration in solidification of fly ash generated in municipal solid waste incineration, Revue des Composites et des Matériaux Avancés, 28(3), pp. 395-403. [4] Uthaman, S., Vishwakarma, V., George, R.P. (2018). Enhancement of strength and durability of fla ash concrete in seawater environments: Synergistic effect of nanoparticles, Construction and Building Materials, 187, pp. 448-459. [5] Kurda, R., Silvestre, J.D., De Brito, J. (2018). Toxicity and environmental and economic performance of fly ash and recycled concrete aggregates use in concrete: A review, Heliyon, 4, pp. 38-45. I T