scholarly journals Synthesis of Modified Polycarboxylate and Its Application in Ultra-High Performance Concrete

2021 ◽  
Vol 8 ◽  
Author(s):  
Shuncheng Xiang ◽  
Yansheng Tan ◽  
Yingli Gao
Keyword(s):  
Silica Fume ◽  
High Performance ◽  
Chain Transfer ◽  
High Performance Concrete ◽  
Raw Materials ◽  
Synthesis Method ◽  
Drying Shrinkage ◽  
Polymerization Reaction ◽  
Ultra High Performance Concrete ◽  
Initiation System

Modified polyurethane prepolymer was prepared using the segmental synthesis method. Then, pectiniform polycarboxylate was synthesized at normal temperature in the complex initiation system of H2O2, APS, sodium bisulfite, Vc, and Rongalit according to the free radical polymerization reaction mechanism, using TPEG, AA, and PEG as raw materials and TGA as the chain transfer agent. Compared with commercial Sika polycarboxylate, its flowability, strength, drying shrinkage, and auto-shrinkage were studied. The experimental results show that the synthesized polycarboxylate could be better dispersed. Adding silica fume can enhance the compressive strength of ultra-high performance concrete (UHPC), while slag may decline its strength. By incorporating slag and silica fume, the drying shrinkage of UHPC was reduced, but its auto-shrinkage was increased.

scholarly journals Synthesis of Pectiniform Polyurethane-Modified Polycarboxylate and Its Preliminary Application in Ultrahigh-Performance Concrete

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Shuncheng Xiang ◽  
Yingli Gao
Keyword(s):  
Silica Fume ◽  
Negative Impact ◽  
Raw Materials ◽  
Synthesis Method ◽  
Autogenous Shrinkage ◽  
Drying Shrinkage ◽  
Isophorone Diisocyanate ◽  
Initiation System ◽  
Dry Shrinkage ◽  
Preliminary Application

In this paper, modified polyurethane prepolymer was synthesized by the segmental synthesis method using isophorone diisocyanate (IPDI), hydroxyl-terminated silicone, and polyether glycol dimethylolpropionic acid as raw materials. After that, pectiniform polycarboxylate, of which side chains were in roughly the same polymerization degree and main chains were in different lengths, was synthesized at normal temperature in the complex initiation system of H2O2, APS, sodium bisulfite, and Vc. Then, compared with commercial Sika polycarboxylate, their applications in ultrahigh-performance concrete (HUPC), including flowability, strength, drying shrinkage, and autogenous shrinkage, were investigated. The results showed that, due to the molecular structure of polyorganosiloxane, the synthesized polycarboxylate could be better dispersed. Dosage of silica fume could effectively improve the compressive strength of UHPC, while slag had a certain negative impact on its strength. Incorporation of slag and silica fume could effectively reduce the dry shrinkage of UHPC.

Mechanical Properties and Durability of Ultra-High Performance Concrete Incorporating Coarse Aggregate

2014 ◽  
Vol 629-630 ◽  
pp. 96-103 ◽  
Author(s):  
Juan Yang ◽  
Gai Fei Peng ◽  
Yu Xin Gao ◽  
Hui Zhang
Keyword(s):  
Compressive Strength ◽  
High Performance ◽  
Coarse Aggregate ◽  
High Performance Concrete ◽  
Fresh Concrete ◽  
Raw Materials ◽  
Autogenous Shrinkage ◽  
Mineral Admixtures ◽  
Ultra High Performance Concrete ◽  
Spalling Failure

Ultra-high performance concrete (UHPC) incorporating coarse aggregate was prepared with common raw materials. Fresh concrete had excellent good workability with slump of 265 mm and slump spread of 673 mm. Compressive strength of UHPC at 56 d reached 150 MPa. However, UHPC exhibited high brittleness in terms of spalling failure which occurred during compression loading.The ratio of splitting tensile strength to compressive strength of about 1/18 and the ratio of flexural strength to compressive strength of about 1/14 at 56 d were also associated with the brittleness of UHPC in this research. Mineral admixtures and fluidity of fresh concrete influenced compressive strength of UHPC significantly. Moreover, UHPC had excellent permeation-related durability but considerable shrinkage. Autogenous shrinkage of UHPC was less than half of free shrinkage, for which the reason is unknown and needs further research.

scholarly journals Production of Ultra-High-Performance Concrete with Low Energy Consumption and Carbon Footprint Using Supplementary Cementitious Materials Instead of Silica Fume: A Review

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8291
Author(s):  
Mays A. Hamad ◽  
Mohammed Nasr ◽  
Ali Shubbar ◽  
Zainab Al-Khafaji ◽  
Zainab Al Masoodi ◽  
...  
Keyword(s):  
Energy Consumption ◽  
Silica Fume ◽  
High Performance ◽  
High Performance Concrete ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Ultra High Performance Concrete ◽  
Cement Production ◽  
Granulated Blast Furnace Slag ◽  
The Impact

The increase in cement production as a result of growing demand in the construction sector means an increase in energy consumption and CO2 emissions. These emissions are estimated at 7% of the global production of CO2. Ultra-high-performance concrete (UHPC) has excellent mechanical and durability characteristics. Nevertheless, it is costly and affects the environment due to its high amount of cement, which may reach 800–1000 kg/m3. In order to reduce the cement content, silica fume (SF) was utilized as a partial alternative to cement in the production of UHPC. Nevertheless, SF is very expensive. Therefore, the researchers investigated the use of supplementary cementitious materials cheaper than SF. Very limited review investigates addressed the impact of such materials on different properties of UHPC in comparison to that of SF. Thus, this study aims to summarize the effectiveness of using some common supplementary cementitious materials, including fly ashes (FA), ground granulated blast furnace slag (GGBS), metakaolin (MK) and rice husk ashes (RHA) in the manufacturing of UHPC, and comparing the performance of each material with that of SF. The comparison among these substances was also discussed. It has been found that RHA is considered a successful alternative to SF to produce UHPC with similar or even higher properties than SF. Moreover, FA, GGBS and MK can be utilized in combination with SF (as a partial substitute of SF) as a result of having less pozzolanic activity than SF.

scholarly journals Matrix Optimization of Ultra High Performance Concrete for Improving Strength and Durability

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 6944
Author(s):  
Julio A. Paredes ◽  
Jaime C. Gálvez ◽  
Alejandro Enfedaque ◽  
Marcos G. Alberti
Keyword(s):  
Silica Fume ◽  
High Performance ◽  
Mercury Intrusion Porosimetry ◽  
High Performance Concrete ◽  
Silica Sand ◽  
Nano Silica ◽  
Ultra High Performance Concrete ◽  
Matrix Optimization ◽  
Binder Ratio ◽  
Strength And Durability

This paper seeks to optimize the mechanical and durability properties of ultra-high performance concrete (UHPC). To meet this objective, concrete specimens were manufactured by using 1100 kg/m3 of binder, water/binder ratio 0.20, silica sand and last generation of superplasticizer. Silica fume, metakaolin and two types of nano silica were used for improving the performances of the concrete. Additional mixtures included 13 mm long OL steel fibers. Compressive strength, electrical resistivity, mercury intrusion porosimetry tests, and differential and thermogravimetric thermal analysis were carried out. The binary combination of nano silica and metakaolin, and the ternary combination of nano silica with metakaolin and silica fume, led to the best performances of the UHPC, both mechanical and durable performances.

Effect of the Type of Silica Fume and Filler on Mechanical Properties of Ultra High Performance Concrete

2018 ◽  
Vol 774 ◽  
pp. 349-354 ◽  
Author(s):  
Kyung Taek Koh ◽  
Seung Hun Park ◽  
Gum Sung Ryu ◽  
Gi Hong An ◽  
Byung Suk Kim
Keyword(s):  
Mechanical Properties ◽  
Silica Fume ◽  
High Performance ◽  
High Performance Concrete ◽  
Strength Loss ◽  
Limestone Powder ◽  
Cement Kiln ◽  
Ultra High Performance Concrete ◽  
Silica Powder ◽  
Kiln Dust

The large quantities of expensive materials such as steel fiber, silica fume, filler and superplasticizer required in the composition of Ultra-High Performance Concrete (UHPC) make its fabrication cost significantly higher than ordinary concrete. This study evaluates the effect of the type of silica fume and filler on mechanical properties of UHPC. The evaluation shows that the use of Zr silica powder instead of common silica fume improves significantly the fluidity of UHPC without loss of the strength and enables to reduce the amount of superplasticizer by maximum 70%. Moreover, the evaluation of the effect of the type and size of the filler reveals that modifying the size of the filler from 2 μm to 4 μm enhances the fluidity without strength loss and that the use of cement kiln dust (CKD) and limestone powder can achieve UHPC with compressive strength higher than 150 MPa. These results show that the use of the materials such as Zr silica powder, CKD and limestone powder can help to fabricate more economic UHPC.

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