Mechanical Performance and Void Structure Change of Foamed Cement Paste Subjected to Static and Cyclic Loading under Plane Strain Conditions

Abstract

Cement-based lightweight materials have received much attention recently in embankment backfill applications, the boundary of which is more close to a plane strain condition. To study the influence of plane strain condition on the behavior and void structure of cement-based lightweight material under cyclic loading, this paper conducted a series of compression tests on foamed cement pastes with densities of 700 and 900 kg/m3 subjected to static and cyclic loading under plane strain conditions. The X-CT technique was adopted to obtain the three-dimensional (3-D) void structures of the specimens before and after the loading tests. The results showed that the plane strain conditions yielded specimen compression strengths 30–50% higher than the unconfined conditions. The specimen integrity endured under load levels of less than 0.5, but failed after approximately 1000 cycles under a load level of 0.8, indicating that cyclic loading could accelerate the degradation of the specimena. The void structures of the specimens showed that the void volumes were featured bfatured an unimodal distribution with unimodal positions in a range of 0.1–0.2 mm3. The unimodal position became higher with the increasing cyclic load level. Slices of the specimens after static and cyclic loading tests suggested that cyclic load could easily lead to the rupture of voids that then merge into bigger voids and the connection of voids forming cracks.

Strength Degradation of Foamed Lightweight Soil Due to Chemical Erosion and Wet-Dry Cycle and Its Empirical Model

“…The FLS in this experiment was mainly made of three components: cement, tap water, and foaming agent. In practical engineering applications, the FLS with a density of 500-1000 kg/m 3 is usually used [4]. Therefore, specimens with densities of 800 and 900 kg/m 3 were selected in this study.…”

“…To quantitatively characterize the sensitivity of the influence factors (i.e., SO 4 2− concentration and FLS density) on strength degradation of FLS, the orthogonal experiments and range analysis were conducted in this section [25]. The density of the FLS generally ranges from 0.6 to 1.6 g/cm 3 in practice [4,26]. The SO 4 2− concentration in the underground water near the coastal region is commonly within the range of 0.338% to 3.38% [27].…”

“…FLS contains a large number of closed voids formed by a mixture of prefabricated foam, cement, and water, and sometimes clay or sand can be added to adjust its cost and performance [1]. Due to the adjustable density and strength of FLS, good engineering performance, and ease of construction [2], it has been increasingly used in practice, including abutment embankment, slope treatment, retaining wall backfilling, and pipeline backfilling [3,4].…”

“…The FLS will suffer rainfall infiltration, evaporation or fluctuation of the groundwater table, temperature change, freeze and thawing, salt solution erosion, and so on [5,6]. The existing studies have presented that such environmental conditions affect the long-term performance of FLS [4,7,8]. Thus, it is vital to investigate the mechanical performance of the FLS considering the real service environment.…”

Algorithm of Estimation of the Degree of Porosity Homogeneity of Foamed Concretes by Local Volumes by X-ray Computed Tomography Method

“…The internal structure of different building materials can be investigated by X-ray computed tomography (XCT) [15][16][17]. The latter is successfully applied for the improvement of the production process of industrial foam concrete, including nontraditional natural raw materials and industrial waste [18][19][20][21]. The analysis of the internal structure of foam concrete and other porous materials considers the pore size as a random value.…”