The Effects of Recycled Tire Rubbers and Steel Fibers on the Performance of Self-compacting Alkali Activated Concrete

In this study, the effects of recycled tire rubbers (RTR) and steel fiber (SF) on the fresh and hardened state properties of the self-compacted alkali activated concrete (SCAAC) were investigated. The ground granulated blast furnace slag, 1 % hooked-end SF, and two types of RTR were utilized. The crumb rubbers (CR) and tire rubber chips (TCR) were used as a substation to natural aggregates at substation levels of 10 % and 15 %. The fresh state performances were evaluated by T50 value, slump flow, V-funnel, and L-Box tests, while mechanical performances were assessed through compressive, flexural, and splitting tensile strength tests. Also, detailed crack and microstructural analyses were conducted. The RTR adversely affected the fresh state properties, which reduced more with SF inclusions. Among the RTR, the TR specimens exhibited lower fresh state performance than the CR specimens. Similar mechanical strengths were obtained on the TR and CR specimens under the same replacement ratios. However, TR specimens exhibited higher deformation capacities than the CR specimens, when SF was utilized. The SCAAC specimens with 1 % SF and 15 % RTR showed more and wider flexural cracks, higher mechanical strength, and deformation capacity, which can be utilized in structural applications, particularly in high seismic zones

Bond Strength and Fracture Toughness of Alkali Activated Self-Compacting Concrete Incorporating Metakaolin or Nanosilica

This study aims to evaluate the effect of nanosilica (NS) and metakaolin (MK) as binder replacement materials on the fresh and hardened characteristics of slag (GGBS)-based alkali-activated self-compacting concretes (A-ASCC). Therefore, nine A-ASCC mixes, with and without metakaolin, were prepared, as well as mixes with and without NS incorporation. In the production of A-ASCC mixes, GGBS was used as a binder material. The fresh properties of A-ASCC were determined using the L-box, V-funnel, T50 value, and slump flow tests, while the hardened properties were examined using compressive strength, bonding strength (pullout test), fracture toughness, and flexural tensile strength tests. A relationship analysis was also conducted on the A-ASCC experimental data. The experimental results showed that NS and MK had a negative effect on the fresh properties of GGBS-based A-ASCC mixtures, whereas metakaolin had a greater influence. The addition of 1% and 2% NS, on the other hand, improved the mechanical performance of the A-ASCC specimens significantly. The use of more than 2% NS had a harmful effect on the mechanical properties of A-ASCC. A 5% replacement ratio of metakaolin improved the mechanical properties of A-ASCC. The use of metakaolin at ratios of more than 5% had a negative effect on the properties of A-ASCC

Performance of Fiber-Reinforced Alkali-Activated Mortar with/without Nano Silica and Nano Alumina

The current study is aimed to evaluate the effect of nanomaterials (nano alumina (NA) and nano silica (NS) on the mechanical and durability performance of fiber-reinforced alkali-activated mortars (FRAAM). Polypropylene fiber (PPF) was added to the binders at 0.5% and 1% of the volume of the alkali-activated mortar (AAM). Design-expert software was used to provide the central composite design (CCD) for mix proportions. This method categorizes variables into three stages. The number of mixes was created and evaluated with varied proportions of variables. The primary binders in this experiment were 50% fly ash (FA) and 50% ground granulated blast slag (GGBS). The alkali-activated solution to binder ratio was 0.5, and the sodium hydroxide (NaOH) concentration was 12 molarity. The sodium silicate to sodium hydroxide ratio was 2.5. The cubic specimens and prisms were evaluated in an ambient atmosphere at 23 + 3 °C room temperature at the ages of 7 and 28 days. The mechanical performance of AAM was indicated through evaluation of the compressive and flexural strength, flowability, and unit weight of the alkali activator mortar. In addition, the durability performance and microstructure analysis were also evaluated. The experiments demonstrated that the AAM without fibers and nanomaterials had a higher flow rate than the other mixtures. However, the flowability of all mixtures was acceptable. The highest compressive strength was deducted through the use of 2% NA and higher flexural tensile strength was obtained for mixtures included 1% NS and 0.5% PPF. The lower water absorption was noted through the combination of 2% nano silica and 1% polypropylene fiber. Whereas, the combination of 2% nano silica, 1% nano alumina, and 0.5% polypropylene fiber had the lower sorptivity. In addition, the microstructure analysis indicated that the nanomaterials significantly improved the matrix and the porosity of the matrix was considerably reduced

The Performance of Alkali-Activated Self-Compacting Concrete with and without Nano-Alumina

The environmental pollution crisis has infiltrated all aspects of life, making it hard to avoid the hazards. To address this, it is essential to recycle industrial waste through green concrete technology, such as ground-granulated blast furnace slag (S), silica fume, and fly ash (FA). In this study, the effect of nano-alumina (NA) on the fresh and hardened stag of fly ash and/or slag-based alkali-activated self-compacting concrete (A-ASCC) cured in an ambient environment was investigated. Three different types of binders were used: 100% slag, 50% slag and 50% fly ash, and 100% fly ash. Four ratios of nano-alumina (0%, 0.5%, 1%, and 1.5%) were used as partial replacements for binder materials. The fresh characteristics of A-ASCC were evaluated by indicating the slump flow, T50 value, V-funnel, and L-Box tests. The mechanical properties of A-ASCC were evaluated by measuring the compressive strength, flexural tensile strength, and splitting tensile strength test values to assess the qualities of the hardened state. Scanning electron microscopy (SEM) was also used to clarify the microstructure of the A-ASCC specimens. Regardless of the binder materials used, the addition of NA has a negative effect on fresh state performance. The mechanical performance of alkali-activated A-ASCC was significantly improved by the incorporation of NA. The incorporation of NA with 50% slag and 50% fly ash showed better properties than other binder materials. However, the highest flexural and compressive strengths were achieved with 1% NA and 100% FA, and the maximum splitting tensile strength was achieved with 1.5% NA. Furthermore, using NA significantly increases the A-ASCC setting time and may be used to produce A-ASCC in an ambient environment

The Effect of Nano-Silica and Nano-Alumina with Polypropylene Fiber on the Chemical Resistance of Alkali-Activated Mortar

This study investigates the simultaneous effect of nano-silica and nano-alumina with and without polypropylene fiber on the chemical-resistant of alkali-activator mortar (AAM) exposed to (5% Sulfuric Acid, 5% Magnesium Sulphate, and 3.5% Sodium chloride) attack. Design-expert software provided the central composite design (CCD) for mixed proportions. Nano-silica (NS) and nano-alumina (NA) at 0, 1%, and 2%, and with polypropylene fiber (0, 0.5%, and 1%) were used in the production of AAM. The alkali activator mortar mixes were created using an alkaline activator to binder ratio of 0.5. The binder materials include 50% fly ash Class F (FA) and 50% ground granulated blast furnace slag (GGBS). A sodium silicate solution (Na2SiO3) and sodium hydroxide solution (NaOH) were combined in the alkaline activator at a ratio of 2.5 (Na2SiO3/NaOH). The mechanical properties of AAM were tested via compressive strength and flexural strength tests. The results show that the acid attack, more than the sulphate and chloride attacks, significantly influenced the AAM. The addition of both nanomaterials improved the mechanical properties and chemical resistance. The use of nanomaterials with PPF showed a superior effect, and the best results were indicated through the use of 2%NA–1%PPF

Enhancement of shrinkage behavior of lightweight aggregate concretes by shrinkage reducing admixture and fiber reinforcement

This paper presents the results obtained from an experimental study conducted to investigate the effect of shrinkage reducing admixture (SRA) and steel fiber addition on the performance properties of lightweight aggregate concrete (LWAC). Total of seven LWAC mixes with SRA or steel fibers were produced at the same water-cement ratio using cold-bonded fly ash coarse aggregates. The percentage of steel fiber volume fractions used in the mixes was 0.25, 0.75 and 1.25. The amount of SRA used in the mixes was 0.75%, 1.5% and 3 % by weight of cement. Ring type specimens were used for the restrained shrinkage cracking test. At the same time, free shrinkage and weight loss of LWACs were measured. Moreover, the compressive and split tensile strength tests were undertaken. The results indicated that the use of steel fibers has little effect on compressive strength but it improves the split tensile strength. The addition of SRA decreases compressive strength without affecting tensile strength. Moreover, the utilization of steel fiber or SRA extends the cracking time and reduces the crack width of LWAC resulting in finer cracks associated with lower free shrinkage. (C) 2013 Elsevier Ltd. All rights reserved

Fire Resistance Performance of Fiber Reinforced Geopolymer Concrete: Review

Geopolymer is a relatively new substance that has sparked a surge of research into nearly every field of geopolymers in recent years. It's still on the verge of becoming a competitive OPC concrete alternative. Mechanical, hardness, and fire resistance properties of geopolymer are exceptional. There has been no/limited research on the effect of fiber integration on fire resistance of geopolymer concrete. In fire-exposed concrete, fiber can help to resist spalling. The goal of this study is to develop materials that exhibit eco-friendly properties and better fire-resistant behavior. Moreover, the combined effect of binder materials and different fibers on the fire resistance of geopolymer concretes. According to the findings, the fire resistance of fiber-reinforced geopolymer concretes increased in the order of carbon fiber-based GPC, micro-steel fiber-based GPC, hooked steel fiber-based GPC, and polypropylene fiber-based GPC. Furthermore, as compared to slag and metakaolin-based GPC, fly ash-based GPC has greater stability and fire resistance. Fiber-reinforced GPC can also be used as a sustainable and durable building material in various construction applications where high performance is needed