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Artificial microcracking of granites subjected to salt crystallization aging test
Bulletin of Engineering Geology and the Environment ( IF 4.2 ) Pub Date : 2020-07-10 , DOI: 10.1007/s10064-020-01891-y
Ahmad Zalooli , Mashalah Khamehchiyan , Mohammad Reza Nikudel , David Martín Freire-Lista , Rafael Fort , Shahram Ghasemi

Salt crystallization-induced decay of Vardavard granodiorite and Shirkouh monzogranite, two Iranian building stones, were assessed with two non-destructive methods: saturation-buoyancy technique and P- and S-wave velocity measurement. Moreover, polarized and fluorescence microscopy studies were used to evaluate the behavior of the studied stones at microscopic scale against a salt crystallization aging test. The aging test extended pre-existing microcracks and generated new ones. Intracrystalline microcracking was the most predominant microcrack type for both samples. Fine-grained Vardavard granodiorite experienced higher intercrystalline microcracking than coarse-grained Shirkouh monzogranite. The microcracking mechanism of feldspars substantially depends on their alteration degree and microstructural precursors. When a growing microcrack reaches a biotite, it propagates within the crystal if the growing microcrack coincides with the cleavage plane; otherwise, it propagates as an intercrystalline one. The increase in maximum microcrack length of the samples was higher than the increase in their mean microcrack length. Low-strength Vardavard granodiorite showed higher microcrack width after the aging test. Dry weight loss in low-strength Vardavard granodiorite was more pronounced than in high-strength Shirkouh monzogranite. Dry unit weight decreased at a higher rate than saturated unit weight with the increase of effective porosity. The reduction in ultrasonic wave velocities and the increment in effective porosity and water absorption were more pronounced for Vardavard granodiorite, indicating a higher degree of decay, i.e., higher microcrack generation, enlargement, and widening. Shirkouh monzogranite, which has large-sized crystals and pores, wider initial microcracks, high tensile strength, and low effective porosity and microcrack density, was more durable than Vardavard granodiorite.



中文翻译:

花岗岩的人工微裂纹经过盐结晶时效测试

用两种非破坏性方法评估了盐结晶引起的两种伊朗建筑石材Vardavard花岗闪长岩和Shirkouh辉长花岗岩的衰变:饱和浮力法和P波和S波速度测量。此外,偏光和荧光显微镜研究被用来评估所研究的宝石在盐析老化试验下的微观行为。老化测试扩展了先前存在的微裂纹并产生了新裂纹。对于两个样品,晶内微裂纹是最主要的微裂纹类型。细粒Vardavard花岗闪石比粗粒Shirkouh单晶花岗岩经历了更高的晶间微裂纹。长石的微裂纹机理主要取决于它们的蚀变程度和微结构前体。当生长的微裂纹到达黑云母时,如果生长的微裂纹与劈裂面重合,它就会在晶体中传播。否则,它以晶间形式传播。样品的最大微裂纹长度的增加高于其平均微裂纹长度的增加。时效试验后,低强度的瓦达瓦花岗闪长岩显示出较高的微裂纹宽度。低强度Vardavard花岗闪长岩的干重损失比高强度Shirkouh辉长花岗岩更明显。随着有效孔隙率的增加,干燥单位重量以比饱和单位重量更高的速率降低。对于Vardavard花岗闪长岩,超声波速度的降低以及有效孔隙率和吸水率的增加更为显着,这表明其衰减程度更高,即产生了更高的微裂纹,扩大和扩大。Shirkouh monzogranite具有较大的晶体和孔洞,较宽的初始微裂纹,较高的拉伸强度以及较低的有效孔隙率和微裂纹密度,比Vardavard的花岗闪长岩更耐用。

更新日期:2020-07-10
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