scholarly journals Effects of HPMC on Workability and Mechanical Properties of Concrete Using Iron Tailings as Aggregates

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6451
Author(s):  
Xiaowei Gu ◽  
Xiaohui Li ◽  
Weifeng Zhang ◽  
Yuxin Gao ◽  
Yaning Kong ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Crack Resistance ◽  
Building Materials ◽  
Hydroxypropyl Methylcellulose ◽  
Air Entrainment ◽  
Recycled Aggregate ◽  
Chemical Effects ◽  
Electric Flux ◽  
Physical And Chemical ◽  
Massive Accumulation

Iron ore tailings (IOTs) are gradually used as building materials to solve the severe ecological and environmental problems caused by their massive accumulation. However, the bulk density of IOT as aggregate is too large, which seriously affects the concrete properties. Therefore, in this paper, the effect of hydroxypropyl methylcellulose (HPMC) on the workability, mechanical properties, and durability of concrete prepared from IOT recycled aggregate was studied. The action mechanism of HPMC on the workability and the mechanical properties of the IOT concrete was analyzed by mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM). The results show that HPMC can effectively improve the segregation problem caused by the sinking and air entrainment of IOT aggregate and improve the crack resistance of concrete with little effect on its compressive strength and electric flux. These results are due to the air-entraining thickening effect of HPMC, which improves the slurry viscosity, hinders the sinking of aggregate, and improves the workability. At the same time, HPMC film, after concrete hardening, will bridge the slurry and aggregate through physical and chemical effects, hinder the propagation of microcracks, and improve the crack resistance.

scholarly journals Effect of Macro-, Micro- and Nano-Calcium Carbonate on Properties of Cementitious Composites—A Review

Materials ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 781 ◽  
Author(s):  
Mingli Cao ◽  
Xing Ming ◽  
Kaiyu He ◽  
Li Li ◽  
Shirley Shen
Keyword(s):  
Mechanical Properties ◽  
Calcium Carbonate ◽  
Dilution Effect ◽  
Hydration Process ◽  
Cementitious Composites ◽  
Inert Filler ◽  
Nucleation Effect ◽  
Chemical Effects ◽  
Physical Effects ◽  
Physical And Chemical

Calcium carbonate is wildly used in cementitious composites at different scales and can affect the properties of cementitious composites through physical effects (such as the filler effect, dilution effect and nucleation effect) and chemical effects. The effects of macro (>1 mm)-, micro (1 μm–1 mm)- and nano (<1 μm)-sizes of calcium carbonate on the hydration process, workability, mechanical properties and durability are reviewed. Macro-calcium carbonate mainly acts as an inert filler and can be involved in building the skeletons of hardened cementitious composites to provide part of the strength. Micro-calcium carbonate not only fills the voids between cement grains, but also accelerates the hydration process and affects the workability, mechanical properties and durability through the dilution, nucleation and even chemical effects. Nano-calcium carbonate also has both physical and chemical effects on the properties of cementitious composites, and these effects behave even more effectively than those of micro-calcium carbonate. However, agglomeration of nano-calcium carbonate reduces its enhancement effects remarkably.

The Mechanical Properties of Recycled Aggregate Concrete

2013 ◽  
Vol 671-674 ◽  
pp. 1852-1855
Author(s):  
Zuo Shan Li ◽  
Li Hui Xie ◽  
Jun Ya Luo ◽  
Xiang Chao Zhang
Keyword(s):  
Mechanical Properties ◽  
Laboratory Experiments ◽  
Building Materials ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Hardened Concrete ◽  
Preparation Process ◽  
Aggregate Concrete ◽  
Waste Concrete ◽  
Natural Aggregates

The experimental investigation of the preparation process of recycled aggregate concrete (RAC) using the waste concrete as recycled aggregate concrete (RCA) was reported. By conducting a series of laboratory experiments, the crushing and sieving procedure of wasted concrete to produce RCA were studied, the RACs with different strengths were designed, the strengths of hardened concrete were investigated. The results indicated that the representative strength for designing C10, C15 and C25 grade RAC using RCA were 11.3, 16.2 and 27.3 Mpa, respectively. The results gained in this study prove to be a valuable building materials using RCA for doveloping the RAC. Recycling and reuse of building wastes have been found to be an appropriate solution to the problems of dumping hundred of thousands tons of debris accompanied with shortage of natural aggregates.

Physical and Chemical Properties of Adhesives Based on Geocement for Restoration and Rehabilitation of Building Materials

2013 ◽  
Vol 688 ◽  
pp. 123-129 ◽  
Author(s):  
Grigorii Vozniuk ◽  
Еlena Kаvalerova ◽  
Pavel Vasiljevich Krivenko ◽  
Оleg Petropavlovsky
Keyword(s):  
Mechanical Properties ◽  
Bond Strength ◽  
Building Materials ◽  
Chemical Properties ◽  
Physical And Chemical Properties ◽  
Physico Chemical ◽  
User Friendly ◽  
Physical And Chemical ◽  
And Chemical Properties

This paper covers the results of study of physico-chemical and mechanical properties of the adhesives based on geocements which have a number of advantageous properties, among them: high compressive and bond strength in the conditions of long-term exposure of various factors, excellent durability, etc. These adhesives are environmentally and user-friendly and safety, their cost is compatible to the known-in-the-art analogs. The results of study suggested to draw a conclusion that they could be successfully used for rehabilitation and restoration of the building materials such as concrete, ceramics, natural stone.

scholarly journals Experimental Study on the Mechanical Properties and Compression Size Effect of Recycled Aggregate Concrete

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2323
Author(s):  
Yubing Du ◽  
Zhiqing Zhao ◽  
Qiang Xiao ◽  
Feiting Shi ◽  
Jianming Yang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Size Effect ◽  
Compressive Stress ◽  
Failure Modes ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Aggregate Concrete ◽  
Substitution Ratio ◽  
The Impact

To explore the basic mechanical properties and size effects of recycled aggregate concrete (RAC) with different substitution ratios of coarse recycled concrete aggregates (CRCAs) to replace natural coarse aggregates (NCA), the failure modes and mechanical parameters of RAC under different loading conditions including compression, splitting tensile resistance and direct shear were compared and analyzed. The conclusions drawn are as follows: the failure mechanisms of concrete with different substitution ratios of CRCAs are similar; with the increase in substitution ratio, the peak compressive stress and peak tensile stress of RAC decrease gradually, the splitting limit displacement decreases, and the splitting tensile modulus slightly increases; with the increase in the concrete cube’s side length, the peak compressive stress of RAC declines gradually, but the integrity after compression is gradually improved; and the increase in the substitution ratio of the recycled aggregate reduces the impact of the size effect on the peak compressive stress of RAC. Furthermore, an influence equation of the coupling effect of the substitution ratio and size effect on the peak compressive stress of RAC was quantitatively established. The research results are of great significance for the engineering application of RAC and the strength selection of RAC structure design.

scholarly journals Discrete Element Simulation Analysis of Biaxial Mechanical Properties of Concrete with Large-Size Recycled Aggregate

2021 ◽  
Vol 13 (13) ◽  
pp. 7498
Author(s):  
Tan Li ◽  
Jianzhuang Xiao
Keyword(s):  
Mechanical Properties ◽  
Stress State ◽  
Strain Curve ◽  
Confining Pressure ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Aggregate Model ◽  
Large Size

Concrete made with large-size recycled aggregates is a new kind of recycled concrete, where the size of the recycled aggregate used is 25–80 mm, which is generally three times that of conventional aggregate. Thus, its composition and mechanical properties are different from that of conventional recycled concrete and can be applied in large-volume structures. In this study, recycled aggregate generated in two stages with randomly distributed gravels and mortar was used to replace the conventional recycled aggregate model, to observe the internal stress state and cracking of the large-size recycled aggregate. This paper also investigated the mechanical properties, such as the compressive strength, crack morphology, and stress–strain curve, of concrete with large-size recycled aggregates under different confining pressures and recycled aggregate incorporation ratios. Through this research, it was found that when compared with conventional concrete, under the confining pressure, the strength of large-size recycled aggregate concrete did not decrease significantly at the same stress state, moreover, the stiffness was increased. Confining pressure has a significant influence on the strength of large-size recycled aggregate cocrete.

scholarly journals Effects of Various Types of Expandable Graphite and Blackcurrant Pomace on the Properties of Viscoelastic Polyurethane Foams

Materials ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1801
Author(s):  
Rafał Oliwa ◽  
Joanna Ryszkowska ◽  
Mariusz Oleksy ◽  
Monika Auguścik-Królikowska ◽  
Małgorzata Gzik ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Chemical Structure ◽  
Oxygen Index ◽  
Polyurethane Foams ◽  
Expandable Graphite ◽  
Ftir Analysis ◽  
Limiting Oxygen Index ◽  
Peak Heat Release Rate ◽  
Physical And Chemical ◽  
Scanning Electron

We investigated the effect of the type and amount of expandable graphite (EG) and blackcurrant pomace (BCP) on the flammability, thermal stability, mechanical properties, physical, and chemical structure of viscoelastic polyurethane foams (VEF). For this purpose, the polyurethane foams containing EG, BCP, and EG with BCP were obtained. The content of EG varied in the range of 3–15 per hundred polyols (php), while the BCP content was 30 php. Based on the obtained results, it was found that the additional introduction of BCPs into EG-containing composites allows for an additive effect in improving the functional properties of viscoelastic polyurethane foams. As a result, the composite containing 30 php of BCP and 15 php of EG with the largest particle size and expanded volume shows the largest change in the studied parameters (hardness (H) = 2.65 kPa (+16.2%), limiting oxygen index (LOI) = 26% (+44.4%), and peak heat release rate (pHRR) = 15.5 kW/m2 (−87.4%)). In addition, this composite was characterized by the highest char yield (m600 = 17.9% (+44.1%)). In turn, the change in mechanical properties is related to a change in the physical and chemical structure of the foams as indicated by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) analysis.

scholarly journals Composite Material of PDMS with Interchangeable Transmittance: Study of Optical, Mechanical Properties and Wettability

2021 ◽  
Vol 5 (4) ◽  
pp. 110
Author(s):  
Flaminio Sales ◽  
Andrews Souza ◽  
Ronaldo Ariati ◽  
Verônica Noronha ◽  
Elder Giovanetti ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Experimental Study ◽  
Room Temperature ◽  
Casting Process ◽  
Optical Characteristics ◽  
Smart Devices ◽  
Superhydrophobic Coating ◽  
Gravity Casting ◽  
High Flexibility ◽  
Physical And Chemical

Polydimethylsiloxane (PDMS) is a polymer that has attracted the attention of researchers due to its unique properties such as transparency, biocompatibility, high flexibility, and physical and chemical stability. In addition, PDMS modification and combination with other materials can expand its range of applications. For instance, the ability to perform superhydrophobic coating allows for the manufacture of lenses. However, many of these processes are complex and expensive. One of the most promising modifications, which consists of the development of an interchangeable coating, capable of changing its optical characteristics according to some stimuli, has been underexplored. Thus, we report an experimental study of the mechanical and optical properties and wettability of pure PDMS and of two PDMS composites with the addition of 1% paraffin or beeswax using a gravity casting process. The composites’ tensile strength and hardness were lower when compared with pure PDMS. However, the contact angle was increased, reaching the highest values when using the paraffin additive. Additionally, these composites have shown interesting results for the spectrophotometry tests, i.e., the material changed its optical characteristics when heated, going from opaque at room temperature to transparent, with transmittance around 75%, at 70 °C. As a result, these materials have great potential for use in smart devices, such as sensors, due to its ability to change its transparency at high temperatures.

scholarly journals Design of Concrete Made with Recycled Brick Waste and Its Environmental Performance

Minerals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 463
Author(s):  
Ivan Janotka ◽  
Pavel Martauz ◽  
Michal Bačuvčík
Keyword(s):  
Building Materials ◽  
Research Process ◽  
Added Value ◽  
Recycled Aggregate ◽  
Partial Replacement ◽  
Fine Aggregate ◽  
Type Ii ◽  
Natural Clays ◽  
Natural Aggregates ◽  
Standardized Parameters

In addition to the known uses of natural clays, less publication attention has been paid to clays returned to the production process. Industrially recovered natural clays such as bricks, tiles, sanitary ceramics, ceramic roofing tiles, etc., are applicable in building materials based on concrete as an artificial recycled aggregate or as a pozzolanic type II addition. In this way, the building products with higher added value are obtained from the originally landfilled waste. This paper details the research process of introducing concrete with recycled brick waste (RBW) up to the application output. The emphasis is placed on using a RBW brash as a partial replacement for natural aggregates and evaluating an RBW powder as a type II addition for use in concrete. A set of the results for an RBW is reported by the following: (a) an artificial RBW fine aggregate meets the required standardized parameters for use in industrially made concrete, (b) a RBW powder is suitable for use in concrete as industrially made type II addition TERRAMENT showing the same pozzolanic reactivity as a well-known and broadly used pozzolan-fly ash, and (c) such an RBW as aggregate and as powder are, therefore, suitable for the production of industrially made TRITECH Eco-designed ready-mixed concrete.

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