摘要：
The purpose of this paper is to investigate the effect of different methods on reducing the pH value of soil in Porous Sea Sand Concrete Mixtures (PSSCM) through a series of experiments. Thereinto, the X-ray diffraction (XRD) technology was applied to analyzing the mechanism of pH value change, and the relationship between the fundamental performance (effective porosity, sound absorption coefficient and compressive strength) and the optimum mixture proportion of PSSCM successfully. In all experiments, plant varieties which have a high matching degree with PSSCM were screened out, and the vegetation performance of PSSCM was verified by field investigation. Consequently, it is showed that the content of calcium hydroxide in PSSCM was positively correlated with the pH value of soil in PSSCM. The four approaches, adding mineral admixtures, appending acid-modified materials, accelerating carbonization, and immersing Deep penetration sealer (DPS), help reduce the pH value. Among them, the lowest pH value (7.8) was obtained by the addition of 10% silica fume, accelerating carbonization for 28 days, and subsequently immersing in DPS for 28 h. Besides, these methods all reduce PSSCM pore and soil pH value by consuming calcium hydroxide. In addition, the best fundamental performance was obtained on the condition that the water-cement ratio of PSSCM was 0.26 and the effective porosity of PSSCM was 25.95%. Likewise, the matching degree between tall fescue and PSSCM was the best under this pH condition. After 120 days of sowing, their stems were thick and strong, and leaves were green and lush. In the meantime, their rhizomes length exceeds 8 cm. (C) 2020 Elsevier Ltd. All rights reserved.
摘要：
A multifunctional material can be used to protect and monitor the degraded concrete infrastructure, providing a self-sensing capacity that is designed to specifically diagnose cracking. Strain-hardening cementitious composites (SHCC) presents superb tensile ductility and pseudo strain-hardening property. In this study, the electrical and mechanical properties of SHCC incorporating carbon black (CB) nanoparticles and air entraining agent (AEA) are examined. The electrical response of SHCC, HFA-SHCC (high fly ash SHCC), and CB-SHCC under direct tension is investigated using the four-point probe test. The results show that the bulk resistivity of all specimens increased with the crack propagation, and the increase ratio in the inelastic phase is much higher than that in the elastic phase. Furthermore, CB-SHCC specimens showed the most sensitive response to first cracking, which can be potentially utilized to detect micro cracking by means of variation in resistivity.
摘要：
Due to material requirements for grouting in loose deposits, a new polymer-modified cement grout (PMCG) material was designed by addicting polyethylene glycol (PEG), polycarboxylate superplasticizer (PS) and sodium silicate into the cement grout. Then, the properties of PMCG were predicted statistically by using the response surface method (RSM) and the effects of the four parameters (w/c, PEG content, sodium silicate content and PS content) as well as their interaction on the response variables (fluidity, bleeding rate, gel time, and early strength) were investigated. Furthermore, the optimal formulation of PMCG (w/c of 0.9, 8.7% sodium silicate, 4% PEG and 1% PS) can be obtained using a multi-objective optimization technique considering the multi-performance requirements of grouting material in loose deposit. Finally, the macro-performance of the grouting material formed by optimal formulation was validated by a set of experiments. The results demonstrated that the proposed designing method can work effectively in determining the optimal formulation of the grouting material to meet various engineering demands. (C) 2020 Elsevier Ltd. All rights reserved.
作者：
Chunning Deng;Weiqun Cai;Jian Yin;Fen Yang;Linchen Li
期刊：
International Journal of Transportation Engineering and Technology,2019年5(4):97-102 ISSN：2575-1743
作者机构：
[Chunning Deng; Weiqun Cai; Jian Yin; Fen Yang; Linchen Li] College of Civil Engineering, Central South University of Forestry and Technology, Changsha, China
摘要：
Autoclaved aerated concrete (AAC) is a new type of green building material rapidly developed nowadays. Moisture content plays a significant effect on its mechanical properties. In this study, a series of uniaxial compression tests were conducted to evaluate the effect of moisture content on the mechanical behaviors. During the tests, full stress-strain curves were obtained. The influence of water content on AAC stress-strain full curve shape, elastic modulus, peak stress, peak strain and ultimate strain was analyzed. The fitting equations of water content with peak stress, peak strain and elastic modulus were established. The results show that the brittleness of AAC decreased with the increased of water content, and the failure mode gradually transited from brittle to ductile failure. When the water content increased from 0% to 10%, obvious difference in the stress-strain curves can be observed. The peak stress decreased by 20.00% and 11.63% when the moisture content was 5% and 10%, respectively. However, when the water content increased from 10% to 40%, the peak stress decreased slowly. The rising section relation model of AAC stress-strain full curve can be fitted by cubic polynomial, which provided reference basis for finite element analysis.
期刊：
Advances in Materials Science and Engineering,2019年2019:1-12 ISSN：1687-8434
通讯作者：
Yin, J
作者机构：
[He, Xiao; Yin, Jian; Yang, Jiewen; Liang, Qiao; Wu, Songyun] Cent South Univ Forestry & Technol, Sch Civil Engn, Shaoshan South Rd 498, Changsha 410004, Hunan, Peoples R China.
通讯机构：
[Yin, J ] ;Cent South Univ Forestry & Technol, Sch Civil Engn, Shaoshan South Rd 498, Changsha 410004, Hunan, Peoples R China.
摘要：
<jats:p>Moisture absorbability is the characteristic of autoclaved aerated concrete that differs from other wall materials. For autoclaved aerated concrete, dry-wet circulation is the main actual service environment and can directly affect moisture absorbability, which influences cracking performance of structure. In this study, autoclaved aerated concrete with dry-wet circulation times of 0, 30, 60, 150, and 270 is selected. The experiment is performed under the condition of temperatures 20°C, 30°C, 40°C, and 50°C and relative humidities (RH) of 40%, 60%, and 80%. The temperature and humidity have significant effects on moisture absorption. When the dry-wet circulation times are increased, the moisture absorption performance improves; when comparing the specimen at the dry-wet circulation of 0 times with the specimen of dry-wet circulation of 270 times, the amount of moisture absorption content increased by 85.7%, at the temperature of 50°C and RH of 80%. Origin software is chosen to fit the moisture absorption kinetics model. SPSS software is used to analyse the linear regression and variance. The results of hygroscopic kinetics showed that the fitting effect of the double exponential function was optimal, and the temperature and humidity were closely correlated with the specimens under dry-wet circulation, for <jats:italic>R</jats:italic><jats:sup>2</jats:sup> greater than 0.941.</jats:p>
期刊：
International Journal of Transportation Engineering and Technology,2019年5(4):103-110 ISSN：2575-1743
作者机构：
[Weiqun Cai; Jian Yin; Songyun Wu; Chunning Deng; Fen Yang; Linchen Li; Jiongjun Yuan] College of Civil Engineering, Central South University of Forestry and Technology, Changsha, China
关键词：
Cement Mortar;Flexural Strength;Compressive-flexural Ratio;Polypropylene Fiber;Orthogonal Test
摘要：
In this study, laboratory tests were conducted to investigate the mechanical behaviors of cement mortars incorporated with different admixtures, such as polypropylene fiber (PP), slag, silica fume and fly ash. Orthogonal tests were designed to evaluate the effects of the admixtures on the brittleness. The flexural strengths and the compressive-flexural ratios were selected to evaluate the brittleness. The optimal proportion can be obtained when PP content was 1.6 kg/m3, and the content of fly ash, slag and silica fume was 10%, 20% and 3% of the cement content respectively. Using the optimal proportion, the 3d flexural strength of cement mortar was 5.65 MPa, which was 19% larger than the specimens without the addition of admixtures; the compressive-flexural ratio was 4.1, which was reduced by 19% in contrast to the control group. The flexural strength at 28d was 9.04 MPa, which was 13% higher than the control group; and the compressive-flexural ratio was 4.21, decreasing 24% compared to the control group. SEM technology was utilized to characterize the evolution of the microstructure induced by the addition of mineral admixtures and PP fiber. Results showed that mineral admixtures made the mortars denser, and the PP fiber formed a cross-linking structure, improving the brittle-resistance. The test results provided some guidance for the mixture design of pavement concrete with a high flexural strength and a low brittleness.
摘要：
制备生态多孔混凝土试件,切片后,采用数字图像处理技术,通过对切片处理方案的选择对比,选取合理的切片图像处理方案;应用PS、MATLAB、IMAGE PRO PLUS、IMAGE J等软件对多孔混凝土试件切片切面进行处理分析,计算试件的图像分析孔隙率,与实测孔隙率比较分析;用数盒子数法计算生态多孔混凝土试件孔隙结构分形维数并建立其孔隙结构特征与分形维数的关系。试验结果表明:各生态多孔混凝土试件的实测孔隙率都不相同,但都在20%～30%的目标孔隙率之间;各生态多孔混凝土试件的分形维数都不相同,说明了生态多孔混凝土孔隙结构的复杂性、不规则性和多样性;分形维数与实测孔隙率密切相关。
