Optimization of autogenous shrinkage and microstructure for Ultra-High Performance Concrete (UHPC) based on appropriate application of porous pumice

In view of the performance requirements of mass ultra-high performance concrete (UHPC) for the Pang Gong bridge steel cable tower in China, the UHPC incorporating of steel slag powder and hybrid expansive agents is optimized and prepared. The effects of steel slag powder and hybrid expansive agents on the hydration characteristics and persistent shrinkage of UHPC are investigated. The results indicate that 15 wt.% steel slag powder and 5 wt.% hybrid expansive agents can effectively reduce the drying shrinkage deformation of UHPC with a slight decrease of strength. Heat flow calorimetry results show that the incorporation of steel slag powder and expansive agents decreases the hydration heat at three days. Moreover, the obtained adiabatic temperature rise of UHPC is 59.5 °C and the total shrinkage value at 180 days is 286 με. The hydration heat release changes of large volume UHPC in the steel-concrete section of cable tower is agreed with the result of adiabatic temperature rise in the laboratory.

Section: Introductionmentioning

confidence: 99%

Effects of Steel Slag Powder and Expansive Agent on the Properties of Ultra-High Performance Concrete (UHPC): Based on a Case Study

Cheng

et al. 2020

“…In summary, the effect of SAP on strength depends on the system being studied. Compared with SAP, LWA can reduce the autogenous shrinkage of concrete, but whether the compressive strength of the concrete structure is reduced depends on the type of LWA material [17]. Wang et al [18] studied the effects of three different types of pre-wetted LWA (fly ash-clay ceramsite, shale ceramsite, and clay ceramsite) on the compressive strength and shrinkage of concrete and found that LWA will reduce the compressive strength of concrete.…”

Section: Introductionmentioning

confidence: 99%

Effect of Pre-Wetted Zeolite Sands on the Autogenous Shrinkage and Strength of Ultra-High-Performance Concrete

Zhang

Wang

2020

In this study, the carrier effect of zeolite sands in reducing the autogenous shrinkage and optimizing the microstructure of ultra-high-performance concrete (UHPC) is studied. Pre-wetted calcined zeolite sand (CZ), calcined at 500 °C for 30 min, and natural zeolite sand (NZ), with 15 wt.% and 30 wt.% in UHPC, are used to partially replace standard sands. On that basis, a series of experiments are executed on the developed UHPC, including compressive strength, autogenous shrinkage, X-ray diffraction (XRD), and isothermal calorimetry experiments. With the increase of the zeolite sand content, the autogenous shrinkage of UHPC decreases gradually. Moreover, when the added CZ content is 30 wt.% (CZ30 specimen), it is effective in reducing autogenous shrinkage. Meanwhile, at the age of 28 days, the compressive strength of CZ30 is 97% of the control group. In summary, it is possible to effectively reduce the autogenous shrinkage of UHPC containing 30 wt.% CZ, without sacrificing its mechanical properties.

“…These three processes are the reflex of a series of chemical and physical reactions in the UHPC system [54]. As commonly known, the rapid growth stage is crucial to the overall autogenous shrinkage of UHPC [5]. Accounting to fact that the autogenous shrinkage at an early age mainly comes from the tensile strain capacity [55,56], cracking easily occurs for UHPC at an early age.…”

Section: Autogenous Shrinkage Of Designed Uhpc With Iotmentioning

confidence: 99%

“…Hence, the research and application in engineering of UHPC is becoming more and more extensive. A typical UHPC mixture comprises of cement, fly ash (FA), silica fume (SF), steel fiber, fine aggregates, superplasticizer, and water [5,6]. Generally, the production of UHPC consumes a large amount of energy and emits an abundance of CO 2 , since the UHPC mix contains huge amounts of cementitious materials (800-1000 kg/m 3 ) [7,8].…”

Section: Introductionmentioning

confidence: 99%

Utilizing Iron Ore Tailing as Cementitious Material for Eco-Friendly Design of Ultra-High Performance Concrete (UHPC)

Shui

Gao

et al. 2021

Self Cite

In this research, iron ore tailing (IOT) is utilized as the cementitious material to develop an eco-friendly ultra-high performance concrete (UHPC). The UHPC mix is obtained according to the modified Andreasen and Andersen (MAA) packing model, and the applied dosage of IOT is 10%, 20%, and 30% (by weight), respectively. The calculated packing density of different mixtures is consistent with each other. Afterwards, the fresh and hardened performance of UHPC mixtures with IOT are evaluated. The results demonstrate that the workability of designed UHPC mixtures is increased with the incorporation of IOT. The heat flow at an early age of designed UHPC with IOT is attenuated, the compressive strength and auto shrinkage at an early age are consequently reduced. The addition of IOT promotes the development of long-term compressive strength and optimization of the pore structure, thus the durability of designed UHPC is still guaranteed. In addition, the ecological estimate results show that the utilization of IOT for the UHPC design can reduce the carbon emission significantly.