西安建筑科技大学学报(自然科学版)

海洋环境中服役的结构在受到高温侵蚀作用后产生的损伤是不可估量的.碱激发海砂混凝土抵抗裂缝展开的能力需要被评估后才可以将其应用于海洋环境中.然而混凝土内部通常是不均匀的以及不连续的,并且这种情况在高温作用后会更加明显.为了探究这个问题,本文研究了两种不同矿渣粉(GGBFS)/粉煤灰(FA)质量比海水、海砂拌制的碱激发海砂混凝土在加热制度为10 ℃/min、恒温时间为180 min的情况下加热到200 ℃、400 ℃、600 ℃以及800 ℃的目标温度后的残余力学性能、微观表现以及基于边界效应模型(BEM)通过标准三点弯梁试验对无尺寸效应断裂参数抗拉强度ft和断裂韧度KIC的预测.研究发现:随着高温温度升高,ft和KIC逐渐降低并且降低速度越来越大.在400 ℃以下,更高GGBFS/FA质量比的碱激发海砂混凝土预测得到的断裂参数值比低GGBFS/FA质量比的混凝土高; 超过400 ℃后,前者强度损失更大并且其残余强度明显低于后者.

The damage to structures in service in the marine environment after exposure to the erosive effects of high temperature is incalculable. The ability of alkali-stimulated marine sand concrete to resist crack development needs to be assessed before it can be used in a marine environment. However, concrete is often internally heterogeneous as well as discontinuous, and this becomes more pronounced after high temperatures. In order to explore this problem, this paper studied the residual mechanical properties and microscopic performance of alkali-activated sea sand concrete mixed with seawater and sea sand with two different mass ratios of ground granulated blast-furnace slag( GGBFS )/ fly ash( FA )when heated to 200 ℃, 400 ℃, 600 ℃ and 800 ℃ under the heating system of 10 ℃/min and constant temperature time of 180 min, and based on Boundary Effect Model(BEM), the tensile strength ft and fracture toughness KIC of fracture parameters without size effect were predicted through the standard three-point bending beam test. It was found that with the increase of high temperature, the ft and KIC gradually decreased and the decrease rate was increasing. Below 400 ℃, the predicted fracture parameters of alkali-activated sea sand concrete with higher GGBFS/FA mass ratio were higher than those of concrete with lower GGBFS/FA mass ratio. When the temperature exceeded 400 ℃, the strength loss of the former was greater and its residual strength was significantly lower than that of the latter.

引言
1 试验方案
2 试验结果分析
3 结论

表1 矿粉和粉煤灰的主要化学成分<br/>Tab.1 Main chemical compositions of GGBFS and FA /%

表1 矿粉和粉煤灰的主要化学成分
Tab.1 Main chemical compositions of GGBFS and FA /%

表2 海砂的基本参数<br/>Tab.2 Basic parameters of sea sand

表2 海砂的基本参数
Tab.2 Basic parameters of sea sand

表3 粗骨料的基本参数<br/>Tab.3 Basic parameters of aggregates

表3 粗骨料的基本参数
Tab.3 Basic parameters of aggregates

图1 试验用骨料的粒径分布<br/>Fig.1 Size distributions of aggregates used in the test

图1 试验用骨料的粒径分布
Fig.1 Size distributions of aggregates used in the test

表4 AASSC的配合比(kg/m3)<br/>Tab.4 Mix proportion of AASSC(kg/m3)

表4 AASSC的配合比(kg/m3)
Tab.4 Mix proportion of AASSC(kg/m3)

图2 加热示意图<br/>Fig.2 Schematic of heating procedure

图2 加热示意图
Fig.2 Schematic of heating procedure

图3 三点弯梁试验图<br/>Fig.3 Test setup for three-point-bending beam

图3 三点弯梁试验图
Fig.3 Test setup for three-point-bending beam

图4 常温下7d和28d的AASSC立方体抗压强度和劈裂抗拉强度结果<br/>Fig.4 Result of 7 d and 28 d cubic compressive strength and splitting tensile strength at 20℃

图4 常温下7d和28d的AASSC立方体抗压强度和劈裂抗拉强度结果
Fig.4 Result of 7 d and 28 d cubic compressive strength and splitting tensile strength at 20℃

图5 不同高温后两种AASSC立方体抗压强度和劈裂抗拉强度的结果<br/>Fig.5 Results of cubic compressive strength and splitting tensile strength of two types AASSC exposed different elevated temperature

图5 不同高温后两种AASSC立方体抗压强度和劈裂抗拉强度的结果
Fig.5 Results of cubic compressive strength and splitting tensile strength of two types AASSC exposed different elevated temperature

图6 两种AASSC不同高温后SEM分析<br/>Fig.6 SEM analysis of two types AASSC exposed different elevated temperature

图6 两种AASSC不同高温后SEM分析
Fig.6 SEM analysis of two types AASSC exposed different elevated temperature

图7 当Fmax达到时截面应力分布<br/>Fig.7 Stress distribution in the cross-section when Fmax is reached

图7 当Fmax达到时截面应力分布
Fig.7 Stress distribution in the cross-section when Fmax is reached

图8 σn随ae变化曲线<br/>Fig.8 Variation of σn with ae

图8 σn随ae变化曲线
Fig.8 Variation of σn with ae

图9 不同高温下ft随a0的变化<br/>Fig.9 Variation of ft with a0 after exposure to different temperatures

图9 不同高温下ft随a0的变化
Fig.9 Variation of ft with a0 after exposure to different temperatures

图10 ft随温度变化曲线<br/>Fig.10 Variation of ft with temperature

图10 ft随温度变化曲线
Fig.10 Variation of ft with temperature

表5 ft和KIC的计算结果<br/>Tab.5 Results of ft and KIC

表5 ft和KIC的计算结果
Tab.5 Results of ft and KIC

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备注

引言

1 试验方案

2 试验结果分析

3 结论

期刊信息