Search

Within the domain of municipal solid waste (MSW) management, incineration is recognized as an efficient volume reduction method, yet it produces substantial quantities of bottom ash (IBA). Redirecting IBA into cementitious frameworks is challenging due to diminished workability, mechanical properties, and durability. This study investigates alumina micro powder (ALMP)'s effect on improving the mechanical and durability aspects of ecological ultra-high performance concrete (EUHPC) produced with IBA. The research examines ALMP's role at various doping levels on the EUHPC's rheological properties, mechanical strengths, durability indices, ultrasonic pulse velocity (UPV), and elastic modulus. Additionally, nanoindentation tests discern ALMP's reinforcing effect on EUHPC's stiffness. Summarizing key findings: ALMP significantly enhances EUHPC's flexural and compressive strengths, with increases ranging from 6.98 % to 24.87 % and 12.39–20.81 %, respectively. Moreover, ALMP raises the elastic modulus by 6.05–19.07% and UPV by 3.11–7.18 %, reflecting a denser, more compact matrix structure. Durability enhancements are evidenced by reductions in drying shrinkage by 4.41–20.01 % and decreased chloride migration by 7.01–22.14 %. Nanoindentation reveals a densification in the microstructure, with escalated high-density C-S-H phases and reduced low-density C-S-H and unhydrated materials. IBA replacement yields energy savings of 11.43 %, CO 2 emission reduction of 7.01 %, and cost savings of 1.18 %. The optimal ALMP inclusion is identified at 10 %, balancing workability, mechanical and microstructural benefits in EUHPC. These revelations position IBA as a useful component in the concrete sector and advocate for ALMP as a beneficial adjunct to elevate the performance of IBA-based concrete towards sustainable development goals. • Mixture of eco-UHPC was designed via MAA particle packing model. • Properties of eco-UHPC were improved via Al 2 O 3 micro-powder. • Optimal content of Al 2 O 3 micro-powder in eco-UHPC was 10%. • Al 2 O 3 micro-powder contributed to a denser microstructure of eco-UHPC. • Environmental friendliness of eco-UHPC was improved via Al 2 O 3 micro-powder. [ABSTRACT FROM AUTHOR]

• UHPC with high elastic modulus was designed via MAA particle packing model. • Workability, microstructure, and mechanical strength of HMUHPC were studied. • Elastic modulus of HMUHPC ranged from 40.5 GPa to 49.3 GPa. • Optimal content of steel chips in HMUHPC was 50 wt%. Elastic modulus is one of the key parameters to weigh the stiffness of concrete members and structural design in civil engineering. Despite its excellent performance in durability and mechanical properties, ultra-high performance concrete (UHPC) is featured with relatively low elastic modulus, which prevents UHPC from being applied in a much larger scope. This study was conducted to explore the feasibility of preparing UHPC with high elastic modulus (HMUHPC) by using steel chips. The modified Andreasen and Andersen (MAA) particle packing model was used to design the initial mixture of HMUHPC. Based on this, some steps were followed to investigate the impacts of varying contents of steel chips on HMUHPC with regard to its mechanical properties, workability, and apparent density. In addition, attention was also paid to how steel chips affected the microstructure of HMUHPC and the ultrasonic pulse velocity (UPV) propagated in HMUHPC. It was found that: 1) Due to the addition of steel chips, there was an increase from 9.65% to 21.73%, 6.38% to 15.85%, 1.28% to 10.49%, and 3.11% to 16.44%, respectively, in the elastic modulus, compressive strength, flexural strength, and apparent density of HMUHPC; 2) The addition of steel chips could reduce the porosity of HMUHPC and optimize its pore size distribution; 3) Considering the effects of steel chips on HMUHPC regarding its microstructure, mechanical properties, and workability, the optimal content of steel chips in HMUHPC was 50 wt%. [ABSTRACT FROM AUTHOR]

• SCM with high elastic modulus was developed by using AMP. • Fluidity, microstructure, mechanical strength, and durability of SCM were studied. • DME of SCM was characterized via ultrasonic testing technology. • DME of SCM was increased by 4.37 ∼ 9.97% due to the addition of AMP. • Durability properties of SCM were markedly improved due to the addition of AMP. Cementitious composites are one of the most widely used building materials in civil engineering. However, their low Young's modulus cannot meet the requirements of long-span structures. This work carried out a feasibility study on producing self-compacting mortar (SCM) with high elastic modulus by using Al 2 O 3 micro powder (AMP). Effects of AMP on the workability, microstructure, mechanical properties, and durability properties of SCM were systematically investigated. The dynamic modulus of elasticity (DME) of SCM was characterized via ultrasonic testing technology. It was found that, 1) due to the addition of AMP, the porosity of SCM was reduced by 2.64 ∼ 13.64%, and the threshold pore diameter of SCM was decreased; 2) the flexural strength and compressive strength of SCM were increased by 4.40 ∼ 15.85% and 2.35 ∼ 14.33%, respectively, because of the incorporation of AMP; 3) the drying shrinkage of SCM was reduced by 6.46 ∼ 11.21%, and the chloride migration coefficient of SCM was decreased by 3.38 ∼ 18.64%, due to the addition of AMP; 4) the optimal content of AMP in SCM was 10%, considering the effects of AMP on the microstructure, mechanical properties, and durability properties of SCM; 5) it was feasible to produce SCM with high elastic modulus by using AMP, and the DME of SCM was increased by 4.37 ∼ 9.97%, because of the incorporation of AMP. [ABSTRACT FROM AUTHOR]

• UHPC with high elastic modulus was design by MAA particle packing model. • Workability, microstructure, and mechanical strength of HEMUHPC were studied. • Elastic modulus of HEMUHPC ranged from 40.50 GPa to 47.13 GPa. • Relationship between elastic modulus and compressive strength was a power function. • Optimal content of alumina micro-powder in HEMUHPC was 10%. Elastic modulus is an important parameter in engineering structural design for evaluating the stiffness of concrete members. Ultra-high-performance concrete (UHPC) has excellent mechanical properties and durability, but the relatively low elastic modulus prohibits the widespread use of the UHPC. In this study, high elastic modulus UHPC (HEMUHPC) was designed according to Modified Andreasen and Andersen particle packing model proposed by Funk and Dinger. Effects of alumina micro-powder (the content of alumina is higher than 99%, and the particle size is lower than 100 μ m) on the workability, microstructure, and mechanical properties of HEMUHPC were systematically investigated. The reason for the improvement of elastic modulus of HEMUHPC was revealed by nano indentation test. It was found that, 1) the porosity and threshold pore diameter of HEMUHPC were reduced because of the addition of alumina micro-powder; 2) the flexural strength, compressive strength, and elastic modulus of HEMUHPC were increased by 3.54–11.23%, 8.89–22.83%, and 6.19–16.37%, respectively, due to the addition of alumina micro-powder; 3) the optimal content of alumina micro-powder was 10%, considering its effects on the workability, mechanical properties, and microstructure of HEMUHPC; 4) Nano indentation experiments showed that the elastic modulus of the alumina micro-powder was 90–135 GPa, which is much higher than the elastic modulus of hydration products of HEMUHPC, and thus the elastic modulus of the HEMUHPC matrix could be improved, due to the addition of alumina micro-powder. [ABSTRACT FROM AUTHOR]

• Producing cement-based sacrificial materials with strontium ferrite is feasible. • Adding strontium ferrite decreases the mechanical properties of cement mortar. • Adding strontium ferrite reduces the drying shrinkage of cement mortar. • Strontium ferrite does not participate in the hydration reaction of cement mortar. • A model between the damage of cement mortar and the temperature is proposed. The safety of nuclear power plant can be improved via core catcher, and cement-based sacrificial materials are widely used in most core catchers because of their simple construction process and the low manufacturing cost. This paper carried out a preliminary investigation to explore the feasibility of using strontium ferrite to prepare cement-based sacrificial materials. The effects of strontium ferrite on the room temperature and high temperature properties of cement mortar were systematically studied in the work. In addition, the damage evolution of cement mortar containing strontium ferrite subjected to elevated temperatures was also identified according to the damage mechanics theory. It was found that, (1) the addition of strontium ferrite led to the deterioration of the mechanical properties, microstructure and pore structure of cement mortar; (2) it was feasible to prepare cement-based sacrificial materials containing strontium ferrite that met the requirements on basic properties like mechanical properties, free water content, volume stability, and the high temperature integrity by controlling the content of strontium ferrite; (3) the correlation between the internal damage of cement mortar and the temperature could be described by Weibull Distribution Model, which provided a basis for the identification and evaluation of serious nuclear power accidents. [ABSTRACT FROM AUTHOR]