Abstract
Alkali-activated slag (AAS) is becoming an increasingly popular building material due to its excellent engineering properties and low CO2 emissions, but its large shrinkage is an important reason to restrict its application and popularization. This work is aimed to study the possibility of inhibiting the shrinkage of AAS mortar by incorporating polypropylene fiber (PPF). For this, an experimental study was carried out to evaluate the effects of PPF content on setting time, fluidity, physical properties, mechanical properties, impact resistance, and microstructure of AAS mortar. The volume content of PPF is 0.05%, 0.1%, 0.15%, and 0.2%. The working, physical (porosity, water absorption, and bulk density), mechanical, shrinkage, and impact resistance properties of the AAS mortars were evaluated. The results show that incorporating PPF effectively reduces the shrinkage deformation of AAS mortar, significantly improves its impact resistance, enhances its toughness, and slightly improves its compressive strength in the later stage. At the same time, PPF delays the initial setting time of AAS mortar and reduces the fluidity, density, porosity, and water absorption of AAS mortar. SEM results show that the bridging effect of PPF between AAS mortars can inhibit the generation and propagation of cracks, improve the internal microstructure, and enhance the performance of AAS mortar.
Highlights
Cement is the largest manufactured product on Earth by mass [1]. e cement industry has grown steadily in the recent decades from 2.31 billion tons in 2005 to 4.13 billion tons in 2017, most of which are driven by the increasing demand from developing countries [2]
Aydın and Baradan [47] investigated the effects of length and volume fraction of steel fibers on the mechanical properties and drying shrinkage behavior of steel fiber reinforced alkali-activated slag/silica fume (AASS) mortars. e results showed that the mechanical performance of AASS mortars was significantly better than ordinary Portland cement (OPC) control mortar, and the drying shrinkage of AASS mortars decreased with the increasing fiber dosage
polypropylene fiber (PPF) with length 9 mm was provided by Changsha Liqiang Building Material Co., Ltd (China). e main performance indicators of PPF are shown in Table 2. e macroscopic and microscopic shapes of PPF are shown in Figure 1. e sand was obtained from local sources with fineness modulus of 2.6 and apparent density of 2550 kg/m3
Summary
Cement is the largest manufactured product on Earth by mass [1]. e cement industry has grown steadily in the recent decades from 2.31 billion tons in 2005 to 4.13 billion tons in 2017, most of which are driven by the increasing demand from developing countries [2]. Ese cementitious materials have many advantages over ordinary Portland cement (OPC) in environmental protection (reducing CO2 emissions, saving energy, and waste utilization) [15,16,17,18], mechanical properties [19, 20], and durability [21,22,23]. Aydın and Baradan [47] investigated the effects of length and volume fraction of steel fibers on the mechanical properties and drying shrinkage behavior of steel fiber reinforced alkali-activated slag/silica fume (AASS) mortars. E results showed that the mechanical performance of AASS mortars was significantly better than OPC control mortar, and the drying shrinkage of AASS mortars decreased with the increasing fiber dosage. It is proved that PPF is a promising reinforcement agent of AAS cementitious materials
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