scholarly journals EXPERIENCE OF APPLICATION HIGH PERFORMANCE CEMENT COMPOSITES FOR CREATING DURABLE SCULPTURAL ELEMENTS

2017 ◽  
Vol 3 ◽  
pp. 286
Author(s):  
Genadijs Sahmenko ◽  
Sandis Aispurs ◽  
Aleksandrs Korjakins
Keyword(s):  
Water Absorption ◽  
High Performance ◽  
Cement Composite ◽  
Cement Composites ◽  
Freezing And Thawing ◽  
Initial Water ◽  
Good Potential ◽  
Freezing And Thawing Cycles ◽  
Material Ductility ◽  
And Control

Traditionally, sculptural and decorative elements of building facades are created from mortar mixes based on lime, gypsum or Portland cement. Generally these materials have porous and permeable structure, which determines their accelerated degradation, especially in the aggressive environment of modern cities. High performance cement composites (HPCC) have been considered for production and restoration of sculptural elements in historical buildings. For this purpose, fine-graded, multi-component and highly workable mixes were elaborated. Mix compositions were modified with micro-fillers, plasticizing and stabilizing admixtures, as well as fibers to improve material ductility and control shrinkage cracking. Basic mechanical properties and durability (such as water absorption, frost resistance) were determined and two types of HPCC were compared (>50 MPa: HPCC and >120 MPa: UHPCC). It has been confirmed that cement composite mixes are characterized by self-consolidating effect, high compressive strength, extremely high resistance versus freezing and thawing cycles and low water absorption. Surface quality was evaluated and initial water absorption (tube tests) were performed for laboratory samples and real sculptural elements after 5 years of exploitation. The results confirmed good potential for using HPCC for creating more attractive and durable architectural shapes and façade elements compared to elements made using traditional cement and lime mortar.

Crack path and fracture surface modifications in cement composites

2015 ◽  
Author(s):  
Sajjad Ahmad ◽  
Jean Marc Tulliani ◽  
Giuseppe Andrea Ferro ◽  
Rao Arsalan Khushnood ◽  
Luciana Restuccia ◽  
...  
Keyword(s):  
Tensile Strength ◽  
High Performance ◽  
Cement Composite ◽  
Absorption Capacity ◽  
Cementitious Composites ◽  
Cement Composites ◽  
Stress Concentrations ◽  
Strength Capacity ◽  
Macro Scale ◽  
Applied Stresses

There is a tremendous increase in the use of high strength and high performance self-consolidating cementitious composites due to their superior workability and mechanical strengths. Cement composites are quasi-brittle in nature and possess extremely low tensile strength as compared to their compressive strength. Due to the low tensile strength capacity, cracks develop in cementitious composites due to the drying shrinkage, plastic settlements and/or stress concentrations (due to external restrains and/or applied stresses) etc. These cracks developed at the nanoscale may grow rapidly due to the applied stresses and join together to form micro and macro cracks. The growth of cracks from nanoscale to micro and macro scale is very rapid and may lead to sudden failure of the cement composites. The present paper reports the modifications in the crack growth pattern of the high performance cement composites to achieve enhanced ductility and toughness. The objective was accomplished by the incorporation of the micro sized inert particulates in the cement composite matrix. The results indicate that the incorporation of micro sized inert particles acted as the obstacles in the growth of the cracks thus improving the ductility and the energy absorption capacity of the self-consolidating cementitious composites.

scholarly journals Freezing and thawing resistance of internally cured high performance concrete

2018 ◽  
Vol 162 ◽  
pp. 02011
Author(s):  
Muthana Saadi ◽  
Tareq al-Attar ◽  
Shatha Hasan
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Internal Curing ◽  
Fine Aggregate ◽  
Freezing And Thawing ◽  
Cast Concrete ◽  
Curing Method ◽  
Compressive And Flexural Strengths ◽  
Limestone Dust ◽  
Freezing And Thawing Cycles

The behavior of internally cured high performance concrete, HPC, exposed to freezing and thawing cycles, was investigated. Two saturated curing agents, Limestone dust and powder of Porcelanite rock, were used to facilitate internal curing for concrete. These agents were used as partial replacements of fine aggregate in two volumetric percentages, 20 and 30 percent. The cast concrete specimens were separated in two groups according to curing method: water-cured and sealed (only internally-cured) specimens. The concrete specimens were subjected to three exposure systems, F0: without freezing and thawing, and F1 and F2: with 50 and 100 cycles of freezing and thawing, respectively. The freezing and thawing test was done as stipulated by the ASTM C666. The conducted tests for each exposure were: compressive and flexural strengths. The results revealed that internal curing does not enhance the concrete resistance to freezing and thawing cycles. Using saturated agents has increased the moisture content of concrete and makes it more vulnerable to frost action deterioration. Sealed specimens for all investigated mixes showed lower reductions in strength than water-cured ones. The lesser water content of these mixes may be the reason for that behavior.

scholarly journals Electrical, Piezoresistive and Electromagnetic Properties of Graphene Reinforced Cement Composites: A Review

Nanomaterials ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 3220
Author(s):  
Shengchang Mu ◽  
Jianguang Yue ◽  
Yu Wang ◽  
Chuang Feng
Keyword(s):  
Material Properties ◽  
High Performance ◽  
Cement Composite ◽  
Electromagnetic Properties ◽  
Cement Matrix ◽  
Future Research ◽  
Cement Composites ◽  
Preparation Methods ◽  
Reinforced Cement ◽  
Filler Dispersion

Due to their excellent combination of mechanical and physical properties, graphene and its derivatives as reinforcements have been drawing tremendous attention to the development of high-performance and multifunctional cement-based composites. This paper is mainly focused on reviewing existing studies on the three material properties (electrical, piezoresistive and electromagnetic) correlated to the multifunction of graphene reinforced cement composite materials (GRCCMs). Graphene fillers have demonstrated better reinforcing effects on the three material properties involved when compared to the other fillers, such as carbon fiber (CF), carbon nanotube (CNT) and glass fiber (GF). This can be attributed to the large specific surface area of graphene fillers, leading to improved hydration process, microstructures and interactions between the fillers and the cement matrix in the composites. Therefore, studies on using some widely adopted methods/techniques to characterize and investigate the hydration and microstructures of GRCCMs are reviewed and discussed. Since the types of graphene fillers and cement matrices and the preparation methods affect the filler dispersion and material properties, studies on these aspects are also briefly summarized and discussed. Based on the review, some challenges and research gaps for future research are identified. This review is envisaged to provide a comprehensive literature review and more insightful perspectives for research on developing multifunctional GRCCMs.

scholarly journals On the Fresh/Hardened Properties of Cement Composites Incorporating Rubber Particles from Recycled Tires

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Alessandra Fiore ◽  
Giuseppe Carlo Marano ◽  
Cesare Marti ◽  
Marcello Molfetta
Keyword(s):  
Cement Composite ◽  
Cement Composites ◽  
Test Results ◽  
Freezing And Thawing ◽  
Chloride Permeability ◽  
Fine Aggregates ◽  
Rubber Particles ◽  
Suitable Amount ◽  
Hardened Properties ◽  
Rubberized Mortar

This study investigates the ameliorative effects on some properties of cement-based materials which can be obtained by incorporating rubber particles as part of the fine aggregates. The aim is to find out optimal cement composite/mortar mixtures, containing recycled-tyre rubber particles, suitable for specific engineering applications. Different percentages of rubber particles, from 0% to 75%, were used and, for each percentage, the suitable amount of sand was investigated in order to achieve the best fresh/hardened performances. In particular the following characteristics were examined: density, compressive strength, modulus of elasticity, shrinkage, weight loss, flexural behaviour, thermal conductivity, rapid freezing and thawing durability, and chloride permeability. The experimental results were compared with the ones of cement composite specimens without rubber aggregates. Test results show that the proposed rubberized mortar mixes are particularly suitable for some industrial and architectural applications, such as under-rail bearings, road constructions, paving slabs, false facades, and stone backing.

Study of Frost Resistance of 50 Years Concrete Exposed to Saline Areas

2013 ◽  
Vol 275-277 ◽  
pp. 1341-1346
Author(s):  
De Cheng Zhang ◽  
Yan Ping Lv ◽  
Zheng Mao Ye
Keyword(s):  
Frost Resistance ◽  
High Performance ◽  
Large Temperature ◽  
Freezing And Thawing ◽  
The North ◽  
Single Side ◽  
Concrete Mechanical Properties ◽  
Saline Area ◽  
Design Requirements ◽  
Freezing And Thawing Cycles

The Hong Run petrochemical oil depot is located in a saline area in the north of Weifang.This area is severe cold in winter and has large temperature span throughout a year. Due to the area's rigorous environmental conditions, concrete with 50 years durability and strength grade of C40 was fabricated with the ordinary Portland cement, high performance superfine mineral powder and high performance pumping agent. Tests using the onsite concrete samples show that concrete mechanical properties meet the design requirements. After 300 freezing and thawing cycles including accelerated freezing thawing method and single-side freezing thawing method, the quality loss rate and relative dynamic modulus both comply with the design requirements. This suggests that the sample concrete has excellent frost resistance ability.

scholarly journals Rehabilitation of buildings in winter conditions

2011 ◽  
Vol 9 (3) ◽  
pp. 357-366
Author(s):  
Slavko Zdravkovic ◽  
Dragoslav Stojic ◽  
Dragana Turnic
Keyword(s):  
Water Absorption ◽  
Porous Materials ◽  
Hardened Concrete ◽  
Freezing And Thawing ◽  
Volume Changes ◽  
Winter Conditions ◽  
Volume Measure ◽  
Solidification Processes ◽  
Freezing And Thawing Cycles

Various factors are taken as the criteria for determining the susceptibility of materials to frost, such as: porosity and water absorption, volume changes, the number of freezing and thawing cycles. Mortars as a mixture of binder, water and sand, after placing and undergoing bonding and solidification processes, represent extremely porous materials, and the same holds for concrete. When the water turns into ice, it changes its volume measure unit from (V?) into Vt = 1.09 V?. If the concrete that has not completed bonding is exposed to frost, the process is likely to be suspended, and later when the warming starts, followed by the thawing of concrete, it will need the repeated vibrating in order to bind again and harden up without the detrimental effects on its strength. However, there are cases of devastating effects of frost on the hardened concrete. All the mentioned strategies should be kept in mind when performing remediation.

scholarly journals Effect of Hydrophobic Treatments on Improving the Salt Frost Resistance of Concrete

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5361
Author(s):  
Guo Li ◽  
Chunhua Fan ◽  
Yajun Lv ◽  
Fujun Fan
Keyword(s):  
Water Absorption ◽  
Frost Resistance ◽  
Contact Angles ◽  
Water Repellent ◽  
Freezing And Thawing ◽  
Ordinary Water ◽  
Salt Scaling ◽  
Mass Losses ◽  
Hydrophobic Treatment ◽  
Freezing And Thawing Cycles

Hydrophobic treatment is an important method to improve the waterproof properties of concrete. To evaluate the effectiveness of hydrophobic treatments on improving the salt frost resistance of concrete, two representative commercial ordinary water repellent agents of silane and organosilicone emulsion were selected, and concrete specimens with three water/cement ratios were fabricated. After the application of repellent agents on concrete surfaces, accelerated saline (5% MgCl2) freeze-thaw cycles were conducted on the specimens. The mass losses and relative dynamic modulus of elasticity (RDME) of concrete were tested periodically. The contact angles and water absorption ratios of concrete with and without hydrophobic treatments were also tested. Results showed that the repellent agents could substantially enhance the hydrophobicity of concrete and greatly reduce its water absorption. Different repellent agents exerted diverse improvements on concrete hydrophobicity. Meanwhile, the repellent agents could improve concrete resistance against salt scaling and RDME losses to a certain degree, and concrete with strong hydrophobicity showed relatively high salt frost resistance. However, the ordinary water repellent agents cannot achieve the same enhancement on salt frost resistance of concrete as that on the water hydrophobicity of concrete. With saline freezing and thawing cycles, the hydrophobic layer formed by the repellent agents on superficial concrete was destroyed gradually. As a result, the salt frost resistance of concrete from the hydrophobic treatments was ultimately lost.

scholarly journals Effect of Expanded Perlite Aggregate Size on Physical and Mechanical Properties of Ultra Lightweight Concrete Produced with Expanded Perlite Aggregate

2019 ◽  
Author(s):  
Mucip Tapan ◽  
Celil Engin
Keyword(s):  
Thermal Conductivity ◽  
Compressive Strength ◽  
Water Absorption ◽  
Bending Strength ◽  
Lightweight Concrete ◽  
Unit Weight ◽  
Ultra Sound ◽  
Expanded Perlite ◽  
Freezing And Thawing ◽  
Freezing And Thawing Cycles

In this study, ultra-light weight concrete (ULWC) with heat-insulating properties is produced by using different size expanded perlite aggregates and various admixtures. The compressive strength, 4 point bending strength, freezing and thawing resistance, water absorption, dry unit weight, ultra sound velocities and thermal conductivity of the samples were determined by applying appropriate tests. The effect of different size expanded perlite aggregate on the properties of ULWC were also investigated in this study and it was found that as the expanded perlite aggregate diameter increased, the void volume uniformity, water absorption percentage and freezing-thawing resistance increased while the unit volume weight of ULWC samples, ultrasound speed velocities, thermal conductivity and compressive strength were decreased. The changes in the masses and compressive strength of ULWC samples subjected to freezing and thawing cycles were examined. The compressive strength loss was found to be between 5 % and 47 % while the weight loss was between 1 % and 3.5 % after 15 freezing and thawing cycles. Finally, the effects of the admixtures on the fresh properties of ULWC were examined and it was determined that the use of 4.5 kg of air-entraining material in one cubic meter of concrete mix is the most ideal ratio and the use of more than 0.01 % by volume of polypropylene fiber is caused settlements in fresh concrete mixtures.

Effect of coating type on the mechanical performance of warp-knitted fabrics and cement-based composites

2018 ◽  
Vol 52 (19) ◽  
pp. 2563-2576 ◽  
Author(s):  
Till Quadflieg ◽  
Sebastian Leimbrink ◽  
Thomas Gries ◽  
Oleg Stolyarov
Keyword(s):  
High Performance ◽  
Mechanical Performance ◽  
Cement Composite ◽  
Potassium Silicate ◽  
Bending Test ◽  
Styrene Butadiene Rubber ◽  
Cement Composites ◽  
Butadiene Rubber ◽  
Knitted Fabrics ◽  
Coating Type

High-performance textiles are used for reinforcing concrete structural parts. This paper presents a technique for producing coated weft-inserted warp-knitted fabrics for concrete applications. Three types of reinforced fabrics differing in coating type and composed of alkali-resistant-glass rovings resulting in a cement composite matrix were produced. The investigated coatings include potassium silicate, carboxylated styrene butadiene rubber and epoxide. The mechanical properties of the developed fabrics and cement composites were determined according to the coating type. Thereafter, the mechanical performance of the warp-knitted reinforced fabrics was investigated using tensile tests. Finally, the properties of the composites were examined according to the coating type using a four-point bending test. The results of the characterization of the coated weft-inserted warp-knitted reinforced fabrics and cement composites based on them are presented and discussed. It is shown that the coating material has high influence on the composite properties. Samples with potassium silicate showed highest strength at the limit of proportionality, while samples with epoxide showed the highest flexural strength.

Pharmacokinetics and Tissue Distribution Study of Ferruginol in Wistar Rat by High-performance Liquid Chromatography

2018 ◽  
Vol 15 (1) ◽  
pp. 67-73 ◽  
Author(s):  
Guiyun Cao ◽  
Suqiao Han ◽  
Keke Li ◽  
Li Shen ◽  
Xiaohong Wang ◽  
...  
Keyword(s):  
Tissue Distribution ◽  
Mobile Phase ◽  
High Performance ◽  
Wistar Rat ◽  
Freezing And Thawing ◽  
Promising Candidate ◽  
Distribution Study ◽  
Substance Loss ◽  
Tissue Distribution Study ◽  
The Brain

Background: Ferruginol (FRGN) exhibits a broad range of pharmacological properties which make it a promising candidate for chemoprevention. However, little is known about its absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties. Methods: A rapid, sensitive and specific HPLC-DAD method was established to quantify FRGN in the plasma and tissues of Wistar rats. After extraction of FRGN with ethyl acetate (EtOAc), chromatographic separation was performed on a YMC ODS C18 column (250 × 4.6 mm I.D., 5 µm) with a mobile phase consisting of methanol-water (92:8, v/v) at a flow rate of 0.9 mL/min. Detection was conducted with a wavelength of 273 nm at 25 °C. Results: The calibration curves for FRGN were linear in the concentration range of 0.5-20 µg/mL for plasma, 0.5-10 µg/mL for heart, liver, spleen, lung, kidney, stomach, intestine, brain and muscle. After three cycles of freezing and thawing, the concentration variations were within ± 7% of nominal concentrations, indicating no significant substance loss during repeated thawing and freezing. The assay was applied to pharmacokinetic and tissue distribution study in rats. Results suggested that lung, heart, liver, spleen and kidney were the major distribution tissues of FRGN in rats, and FRGN could permeate the blood-brain barrier to distribute in the brain of rats. Conclusion: The information provided by this research is very useful for gaining knowledge of the pharmacokinetic process and tissue distribution of FRGN.

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