A review of concrete exposed to low-temperature environments at early ages: mechanical properties and durability

This paper investigates the effect of steel fibre and alkaline-resistance glass fibre lightweight foamed concrete with fly ash inclusion towards mechanical and durability properties. The lightweight foamed concrete (LFC) with a density of 1000 kg/m3with constant water sand ratio of 1: 1:5 and water cement ratio of 0.45 was cast and tested. Steel and alkaline-resistance glass fibres were used as additives and 30% of cement was replaced by fly ash. Detail experiments were setup to study the behaviour and reaction of additives which is expected to give different results on mechanical and durability properties of LFC. Compared to AR-glass fibre, steel fibre has greater contribution in terms of mechanical properties. SFLFC resulted as the most effective approach for compressive, flexural, tensile split and water absorption with strength 6.13 N/mm2, 1.96 N/mm2, 1.52 N/mm2and lowest water absorption at 6.5% respectively. On the other hand, AR-glass fibre is better in controlling drying shrinkage which leads to controlling the cracking at early age. Fly ash does not change the mechanical properties and durability due to unprocessed stage to its finer forms.

Synergic effect of nano-silica and natural pozzolans on transport and mechanical properties of blended cement mortars

The proper mix ratio of hybrid fiber reinforced concrete and frost resistant concrete as bridge deck pavement materials are needed for optimal design. These are based on both the control of strength and durability and consideration of the environment of the construction site. Without reducing its mechanical properties and durability, 0.7% volume ratio of steel fiber and 0.5% volume ratio imitation steel fiber (treated polypropylene fiber) mixed and prepared as C40 hybrid fiber reinforced concrete. The imitation steel fiber can make up for the fact that steel fiber is easily corroded, rather heavy, higher cost, and difficult to use in construction. C40 frost resistant concrete by the admixture of 0.1% volume ratio Dura fiber to improve the freeze-thaw resistance capacity and reduce shrinkage cracks in an early age. The mechanical properties, impermeability, freeze-thaw resistance has improved greatly compared with ordinary concrete. But its mechanical properties and durability can be somewhat less than hybrid fiber reinforced concrete. Frost resistant concrete has an advantage over hybrid fiber reinforced concrete on workability and simple construction. It is recommended superplasticizer can be used to improve the mechanical properties and frost resistance concrete durability.

Despite being most widely used construction materials, cement-based composites are brittle materials with low tensile strength and susceptible to cracking, especially under harsh environments. Over the past three decades, numerous studies have been conducted to enhance the mechanical properties and durability of cementitious composites through the use of various nanomaterials such as carbon nanotubes (CNTs) and carbon nanofibers (CNFs). More recently, graphene nanoplatelets (GNPs) has emerged as an ideal 2D nano-reinforcement for composite materials due to their favorable mechanical, thermal and electrical properties. However, the effects of different dispersing agents and particle size and surface area of GNPs on the mechanical properties of cement-based composites needs to be further investigated. This paper explores the influence of GNP addition on the mechanical properties and durability of cement-based composites. Two types of GNPs with different lateral size (<2 μm and 25 μm) and specific surface area (300 m²/g and 120 m²/g) are used in this study. The GNP concentration is set to be 0.1% by weight of cement in all mixtures. In order to study the effect of dispersion agents, four different dispersion method are utilized to disperse and stabilize GNP particles in aqueous solution. Compressive strength and flexural strength tests are conducted to assess the mechanical properties, while sorptivity test and surface resistivity measurement are carried out to evaluate the durability. In order to explore the effect of GNPs on hydration process of cement mortar, mechanical properties tests are conducted at 7 day and 28 day curing ages and thermal gravimetric analyses are conducted.

Application of the X-ray densitometry in the evaluation of the quality and mechanical properties of biomass pellets

Silica fume as a partial replacement for cement in high-strength concrete has been the focus of numerous studies. However, the impact of substituting cement with silica fume in concrete mixtures on the mechanical and thermal properties of high-strength concrete remains insufficiently explored. Silica fume, characterized by its high pozzolanic activity and ultra-fine particles, is incorporated into concrete mixtures to enhance their mechanical properties and durability. The research examines the influence of varying silica fume content on the compressive strength and CTE of high-strength concrete. In the present study, concrete specimens with a water-cement ratio of 0.32 were prepared, with 5%, 10%, and 15% of the cement replaced by silica fume. Experimental results demonstrate that silica fume significantly improves compressive strength, particularly at early ages, starting from 7 days. However, the CTE of these mixtures is not significantly affected, with the average values varying slightly, ranging from 8.95 to 9.93 × 10⁻⁶/°C. This study contributes to further clarifying the role of silica fume in concrete mixtures and its effect on the CTE

SCC modification by use of amorphous nano-silica

The effect of fly ash and silica fume on mechanical properties and durability of coral aggregate concrete

Concrete mixtures consisting of nanomaterials and fly ash have been shown to be effective for improving the performance of concrete. This study investigates the combined effects of nano‐CaCO3 and fly ash on the mechanical properties and durability of concrete; the mix proportion is optimized through orthogonal experiments. In the first phase, nine concrete mixtures were prepared with three water‐to‐binder ratios (0.4, 0.5, and 0.6), three fly ash contents (15%, 20%, and 25% replacement of the cement weight), and three nano‐CaCO3 contents (1%, 2%, and 3% replacement of the cement weight). Based on the orthogonal analysis, the optimal concrete mix proportion was determined as a water‐to‐binder ratio of 0.4, 20% fly ash, and 1% nano‐CaCO3. In the second phase, further investigations were carried out to examine the superiority of the optimal concrete and evaluate the synergistic effect of nano‐CaCO3 and fly ash. The results showed that nano‐CaCO3 contributed to increasing the compressive strength of fly ash concrete at the early ages, but its effect was quite limited at later ages. Furthermore, the scanning electron microscopy analysis revealed that the seeding effect, filling effect, and pozzolanic effect were the primary mechanisms for the improvement of concrete performance.

This study aims to develop a sustainable solution in the construction industry by incorporating recycled aggregate (RA) into concrete, partially replacing natural gravel aggregate, and enhancing the strength of RA concrete through the addition of hybrid s The study investigates the effect of steel and polypropylene hybrid s on the mechanical and durability properties of recycled aggregate concrete (RAC). The research was carried out in three phases/mixes. The first mix is with different proportions of recycled aggregate (25% and 50%). The second mix is recycled aggregate concrete with only macro-steel , and the third mix is recycled aggregate concrete with different proportions of macro-steel and micro-polypropylene . Mechanical and durability properties were investigated in all three types of concrete mixes and compared with the control mix. The study concluded that the mechanical properties of hybrid fiber reinforced recycled aggregate concrete (HFRRAC) are dependent on the amount of recycled aggregate, proportions, and type. The macrosteel fibers with high elasticity modulus and stiffness improve the concrete's strength and toughness. The increase in content affects the workability of - reinforced concrete. Synthetic microfibers with excellent ductility and dispersion improve concrete's mechanical properties and durability. Synthetic microfibers when used along with macro-steel improve both mechanical properties and durability characteristics.

Effect of addition of nanoclay and SBR latex on fly ash-slag geopolymer mortar

Novel insights on the setting process, hardened properties, and durability of sustainable ultra-high-performance seawater sea sand concrete

Scientists have effectively demonstrated that the introduction of a waste product comprising cementitious chemical compositions can enhance the mechanical properties and durability of cold bitumen emulsion mixes (CBEMs). On the other hand, the high air void content of the CBEM mix remains a challenge that is considered unsatisfactory by paving engineers. As a result, this investigation highlights two major changes that were made. The first is the use of waste paper sludge ash (PSA) as a filler in CBEM instead of the conventional mineral filler (CMF). The second change was made to further improve the mixture by reducing the amount of CBEM air voids using microwave (MW) heating energy as a post-treatment method. When compared to typical hot mix asphalt (HMA), the new CBEMs showed great mechanical properties and durability. Moreover, the proposed method, using CBEMs, has lower environmental risks, is safer, and is more cost-effective than existing paving mix technologies. This study presents a method for controlling air voids within pavement specifications without affecting mechanical behaviour or generating additional environmental or economic considerations. When compared to typical mixtures, laboratory test results showed that MW-heating can enhance both the stiffness modulus and the air void content. Furthermore, these results revealed a minor reduction in creep stiffness and water sensitivity. Nevertheless, in terms of mechanical, volumetric, and economic properties, the suggested post-mix treatment was comparable to HMA. The findings point to the need to adopt CBEM post-heating approaches, particularly the MW treatment procedure.

The role of ultra-fine supplementary cementitious materials in the durability and microstructure of airport pavement concrete

Expansive high-performance concrete for chemical-prestress applications