摘   要：设计了一种基于超高性能混凝土配合比的3D打印材料，研究了3D打印混凝土试件和浇筑试件的抗渗性能和抗冻性能。结果表明，用该配合比配制的3D打印混凝土试件和浇筑试件均具有良好的抗渗性能和抗冻性能，试件均能在1.4 MPa水压力下保持不渗水，300次冻融循环后保持较高的力学性能和相对动弹性模量，且3D打印试件测试结果更好。为增强结构密实度，混凝土原材料添加了钢纤维，通过CT扫描发现，3D打印试件结构更加紧密，内部缺陷较少，受到冻融破坏时能保持较完整的结构。 Abstract: A 3D printed material based on the ultra-high performance concrete mix proportion was designed. 3D printed specimens and casted specimens were prepared to study their impermeability and frost resistance. The results show that these concrete specimens with ultra-high performance concrete mix proportion have good impermeability and frost resistance. The experimental specimens can maintain impermeability under 1.4 MPa water pressure, and maintain great mechanical properties and relative dynamic elastic modulus after 300 freeze-thaw cycles, and the test results of 3D printed specimens are better. CT scan analysis reveals that the structure of 3D printed concrete is denser. The addition of steel fibers can improve the compactness of the structure when freeze-thaw damage occurrs. Thus, 3D printed specimens have better comprehensive performance due to fewer internal defects.

吴凯,赖建中,杜龙雨,等.3D打印超高性能混凝土的抗渗及抗冻性能研究[J].混凝土与水泥制品,2022(10):1-6. WU K,LAI J Z,DU L Y,et al.Impermeability and Frost Resistance of 3D Printed Ultra-high Performance Concrete[J].China Concrete and Cement Products,2022(10):1-6.

摘   要：为解决风机基础混凝土面层修补加固时出现开裂的问题，运用弹性力学方法计算了圆环形基础在中心受钢筒约束条件下面层修补加固混凝土中的应力状况，通过结构参数的代入，建立了弹性力学计算方程，并进行了弹性力学分析。结果表明：在基础环钢筒的约束下，面层修补加固混凝土的早期收缩和温度变形会产生较大的约束拉应力；当该拉应力大于混凝土的抗拉强度时，会导致混凝土开裂；提供了消减约束应力的相应措施和涉及到的相应技术参数，以便削弱该约束应力，使其在整个发展期均小于混凝土的抗拉强度，可为解决此类混凝土基础面层开裂问题提供借鉴。 Abstract: In order to solve the problem of cracking during the repair and reinforcement of the wind-powder tower concrete foundation surface layer, the elastic mechanics method was used to calculate the stress state of the repaired and strengthened concrete layer of the annular foundation under the constraint condition of the steel cylinder in the center. Mechanics equations were calculated, and elastic mechanics analysis was carried out. The results show that under the constraint of the foundation ring steel cylinder, the early shrinkage and temperature deformation of the repaired and strengthened concrete of the surface layer will generate a large constrained tensile stress, which is greater than the tensile strength of the concrete will cause the concrete to crack. Corresponding measures to reduce restraint stress and related technical parameters are provided in order to weaken the restraint stress and make it less than the tensile strength of concrete in the whole development period, which can provide reference for solving the cracking problem of concrete foundation surface.

摘   要：采用了体积掺量25%的泡沫与陶粒复合制备了不同密度等级（800、1 000、1 200、1 400）的大流动性陶粒泡沫混凝土，研究了微硅粉掺量对其性能影响，测试了陶粒泡沫混凝土的流动性、不同龄期的抗压强度、劈裂抗拉强度、吸水率、导热系数等。结果表明：引入泡沫可使混凝土的坍落度大于240 mm，具有大流动性的同时有效解决了陶粒易上浮的问题；微硅粉的掺入提高了陶粒泡沫混凝土的力学性能，且密度等级越低，微硅粉的提高效果越明显；陶粒泡沫混凝土的孔隙率和吸水率随陶粒掺量的增加而增加，随微硅粉掺量的增加而降低；陶粒可以改善混凝土的保温性能，其导热系数随陶粒掺量的增加而降低。 Abstract: High-flowability ceramsite foamed concrete with different density grades(800, 1 000, 1 200, 1 400) was prepared by compounding foam and ceramsite with the volume content of 25%. The influence of microsilica silica fume content on its performance was studied, and the fluidity, compressive strength at different ages, splitting tensile strength, water absorption and thermal conductivity of ceramsite foamed concrete were tested. The results show that the introduction of foam can make the slump of concrete larger than 240 mm, which has large fluidity and effectively solves the problem of easy floating of ceramsite. Microsilica silica fume improves the mechanical properties of ceramsite foamed concrete, and the lower the density grade, the better the improvement effect of microsilica silica fume. The porosity and water absorption of ceramsite foamed concrete increase with the increase of ceramsite content, and decrease with the increase of microsilica silica fume. Ceramsite can improve the thermal insulation performance of concrete, and its thermal conductivity decreases with the increase of ceramsite content.

魏威,陈兵,李德生,等.大流动性陶粒泡沫混凝土试验研究[J].混凝土与水泥制品,2022(10):12-16. WEI W,CHEN B,LI D S,et al.Experimental Research on High-flowability Lightweight Aggregate Foamed Concrete[J].China Concrete and Cement Products,2022(10):12-16.

摘   要：利用预制不同初始缝长的小尺寸混凝土梁试件，进行了冻融循环试验，并通过三点弯曲试验研究了冻融作用后混凝土的断裂性能。基于边界效应模型，引入反映材料非连续性与非均匀性的系数，利用试件的极限荷载，确定了不同冻融循环次数下混凝土的拉伸强度与断裂韧度。结果表明：随着冻融循环次数的增加，混凝土的拉伸强度与断裂韧度明显降低；相对于未经冻融循环的试件，当经75次冻融循环时，混凝土拉伸强度与断裂韧度的降低超过了38%；基于边界效应模型得到的拉伸强度考虑了材料的非连续性和非均匀性，使计算结果明显高于混凝土的劈裂抗拉强度，可较准确地反映冻融作用后混凝土的劣化损伤程度。 Abstract: The fracture behavior of concrete beam specimens with different initial notch lengths after freeze-thaw was studied by using three-point bending test. Based on the boundary effect model, the coefficients reflecting the material discontinuity and inhomogeneity were introduced, and the maximum fracture load of the specimens was used to determine the real tensile strength and fracture toughness of concrete under different freeze-thaw cycles times. The results show that as the number of freeze-thaw cycles increases, the tensile strength and fracture toughness of concrete are obviously reduced. Compared with the specimens without freeze-thaw cycles, the tensile strength and fracture toughness of concrete are reduced by more than 38% when the number of freeze-thaw cycles reached 75 times. The tensile strength obtained based on the boundary effect model is significantly higher than the splitting tensile strength of concrete due to the incorporation of the discontinuity and non-uniformity of materials, and can more accurately reflect the deterioration and damage degree of concrete after freeze-thaw action.

孟令彤,杨树桐,杨松.冻融循环条件下混凝土的拉伸强度与断裂韧度研究[J].混凝土与水泥制品,2022(10):17-21. MENG L T,YANG S T,YANG S.Study on the Influence of Freeze-thaw Cycles on the Tensile Strength and Fracture Toughness of Concrete[J].China Concrete and Cement Products,2022(10):17-21.

徐琳琳,周双喜.多因素耦合作用下氯离子在混凝土中的时变扩散模型研究[J].混凝土与水泥制品,2022(10):22-26. XU L L,ZHOU S X.Study on Time-varying Diffusion Model of Chloride Ion in Concrete Under Multi Factor Coupling[J].China Concrete and Cement Products,2022(10):22-26.

摘   要：基于大体积混凝土温度-应力场耦合计算方法和大体积混凝土开裂风险评估技术，针对实际工程新建泵闸项目，进行浇筑后28 d温度变化预测、温度预警评估和开裂风险评估，并及时提供温控建议。结果表明，通过综合考虑控温方式和控温时间设置，有效控制了该底板的最高温度≤70 ℃，内表温差≤25 ℃/d，入模温度≤30 ℃，降温速率≤2 ℃/d，符合JTS/T 202—1—2022《水运工程大体积混凝土温度裂缝控制技术规范》的要求，达到了良好的预测效果和裂缝控制效果。 Abstract: Based on the coupled temperature-stress field calculation method and the cracking risk assessment technology of mass concrete, the temperature change prediction, temperature early warning assessment and cracking risk assessment 28 d after pouring were carried out for a new pump gate project of the actual project, and the temperature control suggestions were provided in time. The results show that by comprehensively considering the temperature control method and temperature control time setting, the maximum temperature of the bottom plate is effectively controlled ≤70 ℃, the internal surface temperature difference is ≤25 ℃/d, the molding temperature is ≤30 ℃, and cooling rate is ≤ 2 ℃/d, which can meet the specification requirements of the JTS/T 202—1—2022 Technical Specification for Thermal Cracking Control of Mass Concrete of Port and Waterway Engineering and achieve good prediction and crack control effect.

刘丹.泵闸大体积混凝土开裂风险评估与温度控制[J].混凝土与水泥制品,2022(10):27-31. LIU D.Cracking Risk Assessment and Temperature Control of Mass Concrete for Pump Gate[J].China Concrete and Cement Products,2022(10):27-31.