Flexural and Compressive Strength of the Cement Paste with Recycled Concrete Powder

2017 ◽  
Vol 1144 ◽  
pp. 65-69
Author(s):  
Jaroslav Topič ◽  
Josef Fládr ◽  
Zdeněk Prošek
Keyword(s):  
Compressive Strength ◽  
Cement Paste ◽  
Cost Reduction ◽  
Negative Impact ◽  
Reference Sample ◽  
Strength Properties ◽  
Recycled Concrete ◽  
Cement Composites ◽  
Cement Production ◽  
Cement Replacement

In previous work focused on using recycled concrete powder as cement replacement the basic dependency of the mechanical properties on the amount of recycled concrete powder was defined. Influence of the amount of recycled concrete powder on the flexural and compressive strength was shown on 0, 33, 67 and 100 wt. % cement replacement. Based on the previous data the strength properties of the cement paste with recycled concrete powder below 33 wt. % was almost constant and strength properties were comparable with reference sample made of cement only. After the recycled concrete powder in cement paste exceeded amount of 33 wt. % the flexural and compressive strength decrease rapidly. In case of 67 wt. % amount of recycled concrete powder the compressive strength decrease about 65 %. The aim of this article is define critical amount of recycled concrete powder in cement paste when strength properties start decrease rapidly and cement replacement is no longer beneficial. This critical amount will be located somewhere between 30 and 50 wt. % of recycled concrete powder. Replacement below critical amount could lead to cost reduction of cement composites and also the negative impact of the cement production and concrete disposal on environmental could be reduced.

Influence of Finely Ground Recycled Concrete on Microstructure of Cement-Based Composite Material

2016 ◽  
Vol 714 ◽  
pp. 111-115
Author(s):  
Jaroslav Topič ◽  
Zdeněk Prošek ◽  
Josef Fládr ◽  
Jan Trejbal ◽  
Pavel Tesárek ◽  
...  
Keyword(s):  
Cement Paste ◽  
Cost Reduction ◽  
Recycled Concrete ◽  
Partial Substitution ◽  
Partial Replacement ◽  
Cement Pastes ◽  
Cement Production ◽  
Construction Waste ◽  
First Results

This article deals with using recycled concrete in cement-based composite materials. The recent studies were mostly focused on utilization of recycled concrete in the form of an aggregate filler. In this study we are investigating the possibility of using finely ground recycled concrete as microfiller or partial substitution for binder. In particular, we focus on changes in microstructure of the cement paste which differed in amount of finely ground recycled concrete (FGRC). We used four mixtures of cement pastes containing 0, 33, 50 and 67 wt. % of FGRC, respectively. For the examination of their microstructure, phase distinction and determination of FGRC influence, the images obtained using optical and electron microscope were used. The first results indicate that cement paste with 33 wt. % of FGRC has similar mechanical properties as reference cement paste. Partial replacement of cement by finely ground recycled concrete leads to a cost reduction of cement-based composites and also can reduce environmental impacts of construction waste disposal and cement production.

Relationship between Compressive Strength and Young's Modulus of Cement Paste with Recycled Concrete Powder

2016 ◽  
Vol 722 ◽  
pp. 254-259 ◽  
Author(s):  
Jaroslav Topič ◽  
Jan Trejbal ◽  
Tomáš Plachý ◽  
Zdeněk Prošek
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
High Speed ◽  
Reference Sample ◽  
Milled Powder ◽  
Recycled Concrete ◽  
Cement Pastes ◽  
Cement Replacement ◽  
Cement Based Materials

This article deals with utilization of recycled concrete in form of high-speed milled powder into cement based materials. Recycled concrete powder in that form is used as microfiller and cement replacement. This article contains results of mechanical properties of the cement pastes with different amount of recycled concrete powder. The mechanical properties as the compressive strength, flexural strength, dynamic Young's and share moduli are observed during 409 days. According to results can be assumed that recycled concrete powder can be used as microfiller and cement replacement under 30 wt. % of total amount. Especially the results of compressive strength are comparable with reference sample. But there are some abnormalities in long term development of the strength that need to be explained.

scholarly journals Effect of Waste Clay Brick Powder on Physical and Mechanical Properties of Cement Paste

2021 ◽  
Vol 15 (1) ◽  
pp. 370-380
Author(s):  
David Sinkhonde ◽  
Richard Ocharo Onchiri ◽  
Walter Odhiambo Oyawa ◽  
John Nyiro Mwero
Keyword(s):  
Compressive Strength ◽  
Cement Paste ◽  
Setting Time ◽  
Partial Replacement ◽  
Clay Brick ◽  
X Ray ◽  
Cement Replacement ◽  
Clay Bricks ◽  
Brick Powder ◽  
Scanning Electron

Background: Investigations on the use of waste clay brick powder in concrete have been extensively conducted, but the analysis of waste clay brick powder effects on cement paste is limited. Materials and Methods: This paper discusses the effects of waste clay brick powder on cement paste. Fragmented clay bricks were grounded in the laboratory using a ball mill and incorporated into cementitious mixes as partial replacement of Ordinary Portland Cement. Workability, consistency, setting time, density and compressive strength properties of paste mixes were investigated to better understand the impact of waste clay brick powder on the cementitious paste. Four cement replacement levels of 2.5%, 5%, 7.5% and 10% were evaluated in comparison with the control paste. The chemical and mineral compositions were evaluated using X-Ray Fluorescence and X-Ray Diffractometer, respectively. The morphology of cement and waste clay brick powder was examined using a scanning electron microscope. Results: The investigation of workability exhibited a reduction of slump attributed to the significant addition of waste clay brick powder into the cementitious mixes, and it was concluded that waste clay brick powder did not significantly influence the density of the mixes. In comparison with the control paste, increased values of consistency and setting time of cement paste containing waste clay brick powder confirmed the information available in the literature. Conclusion: Although waste clay brick powder decreased the compressive strength of cement paste, 5% partial cement replacement with waste clay brick powder was established as an optimum percentage for specimens containing waste clay brick powder following curing periods of 7 and 28 days. Findings of chemical composition, mineral composition and scanning electron microscopy of waste clay brick powder demonstrated that when finely ground, fragmented clay bricks can be used in concrete as a pozzolanic material.

Cellulose Fibres as a Reinforcing Element in Building Materials

2017 ◽  
Author(s):  
Viola Hospodarova ◽  
Nadezda Stevulova ◽  
Vojtech Vaclavik ◽  
Tomas Dvorsky ◽  
Jaroslav Briancin
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Compressive Strength ◽  
Building Materials ◽  
Reference Sample ◽  
Physical And Mechanical Properties ◽  
Natural Fibre ◽  
Cement Composites ◽  
Cellulose Fibres ◽  
Cellulosic Fibres

Nowadays, construction sector is focusing in developing sustainable, green and eco-friendly building materials. Natural fibre is growingly being used in composite materials. This paper provides utilization of cellulose fibres as reinforcing agent into cement composites/plasters. Provided cellulosic fibres coming from various sources as bleached wood pulp and recycled waste paper fibres. Differences between cellulosic fibres are given by their physical characterization, chemical composition and SEM micrographs. Physical and mechanical properties of fibre-cement composites with fibre contents 0.2; 0.3and 0.5% by weight of filler and binder were investigated. Reference sample without fibres was also produced. The aim of this work is to investigate the effects of cellulose fibres on the final properties (density, water absorbability, coefficient of thermal conductivity and compressive strength) of the fibrecement plasters after 28 days of hardening. Testing of plasters with varying amount of cellulose fibres (0.2, 0.3 and 0.5 wt. %) has shown that the resulting physical and mechanical properties depend on the amount, the nature and structure of the used fibres. Linear dependences of compressive strength and thermal conductivity on density for plasters with cellulosic fibres adding were observed.

Experimental Study of the Recycled Plastic Aggregate Lightweight Composites Based on Different Kinds of Binder

2020 ◽  
Vol 868 ◽  
pp. 32-38
Author(s):  
Valéria Gregorová ◽  
Zuzana Štefunková ◽  
Miriam Ledererová
Keyword(s):  
Thermal Conductivity ◽  
Compressive Strength ◽  
Bulk Density ◽  
Thermal Conductivity Coefficient ◽  
Negative Impact ◽  
Cement Composites ◽  
Ethyl Vinyl ◽  
Cement Binder ◽  
Lightweight Composites ◽  
Recycled Waste

In this paper, the selected properties of lightweight composites based on the different kinds of binder and recycled waste plastics aggregate were studied. Plastic waste e.g. foamed polystyrene, polypropylene, polyurethane foam or ethyl vinyl acetate (EVA) as an aggregate in these composites was used. Cement CEM II B/S 32.5 R and an organic-based adhesive with the business name Conipur 360 were used as a binder. The cement composites consisted of constant water to cement ratio 0.50 and dose of cement 175 kg/m3. Mixtures of adhesive composites were prepared with constant dose of adhesive 100 kg/m3. The kind of recycled waste aggregate was only changed. The physical properties, such as bulk density, compressive strength and thermo-technical properties were verified. The application of organic-based adhesive resulted in a significant decreasing values of the bulk density (100 kg/m3 - 230 kg/m3) and the thermal conductivity coefficient (0.0511 W/m.K - 0.0686 W/m.K) of lightweight composites. The negative impact of this type of binder resulted to a decreasing value of the compressive strength (0.15 MPa - 0.32 MPa). Use of cement binder caused to an increasing of bulk density (290 kg/m3 - 375 kg/m3) and worsening of the thermal conductivity coefficient of these composites (0.0660 W/m.K - 0.0799 W/m.K). The compressive strength values of cement composites ranged from 0.24 MPa to 0.50 MPa.

scholarly journals Compressive strength of green concrete with low cement and high filler content

2021 ◽  
Vol 64 (2) ◽  
pp. 93-108
Author(s):  
Andrija Radović ◽  
Snežana Marinković ◽  
Aleksandar Savić
Keyword(s):  
Compressive Strength ◽  
Filler Content ◽  
Negative Impact ◽  
Economic Benefits ◽  
Limestone Filler ◽  
Suitable Alternative ◽  
Green Concrete ◽  
Cement Replacement ◽  
Alternative Materials ◽  
Wide Availability

It is estimated that by the end of the current decade, about 26% of clinker will be replaced by suitable alternative materials, among which limestone filler probably has the greatest potential due to its wide availability and relatively low price. Although codes allow as much as 35% of clinker to be replaced by limestone filler, the amounts used in practice are far lower and average only 6-7% globally. In order to use the great potential of fillers, it is necessary to know the key parameters that affect the properties of green concrete with low cement and high filler content in fresh and hardened states. Therefore, thorough literature review was conducted, followed by design of 18 concrete mixtures, in order to analyze the effects of the percentage of cement replacement, water-cement ratio, but also the particle size of the applied filler. The results of experimental research show that at the same w/c ratio there is an increase in compressive strength with increasing percentage of cement replacement and that it is possible to make medium-strength concrete with significantly reduced amount of cement 180 kg/m3 compared to traditional concrete. Thus, economic benefits can be achieved, but also the negative impact of the concrete industry on the environment can be reduced. Unfortunately, the workability of such mixtures can be impaired to the extent that their practical application is prevented, so it is necessary to take further steps to solve this problem.

scholarly journals Recycled aggregate amount variation of fraction 4/8 mm and 8/16 mm in the concrete mixture

2020 ◽  
Vol 15 (2) ◽  
pp. 49-54
Author(s):  
Jozef Junák ◽  
Natália Junáková
Keyword(s):  
Compressive Strength ◽  
Reference Sample ◽  
Point Of View ◽  
Recycled Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Concrete Aggregate ◽  
Economic Point ◽  
Aggregate Fractions ◽  
Aggregate Amount

AbstractThe introductory part of the paper is devoted to the classification of aggregates according to various criteria, one of them is the geographical origin of aggregates. From the point of view of the circular economy, the use of recycled aggregates comes to the fore, mainly from the ecological point of view but also from the economic point of view.The paper summarizes the results of research focused on the variation of the amount of 2 Recycled concrete aggregate fractions in concrete, followed by an evaluation of the effect of the presence of recycled material in the mixture on the selected property, specifically compressive strength. The highest compressive strength 34.7 MPa after 28 days hardening reached sample containing 100% recycled fraction 4/8 mm, and 60% recycled fraction 8/16 mm. This value is only slightly different from the compressive strength of the reference sample (34.4 MPa).

scholarly journals Concrete with Partial Substitution of Waste Glass and Recycled Concrete Aggregate

Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 430
Author(s):  
Jawad Ahmad ◽  
Rebeca Martínez-García ◽  
Jesús de-Prado-Gil ◽  
Kashif Irshad ◽  
Mohammed A. El-Shorbagy ◽  
...  
Keyword(s):  
Performance Test ◽  
Coarse Aggregate ◽  
Mechanical Performance ◽  
Negative Impact ◽  
Strength Properties ◽  
Waste Glass ◽  
Recycled Concrete ◽  
Partial Substitution ◽  
Concrete Aggregate ◽  
Recycled Concrete Aggregate

The current practice of concrete is thought to be unsuitable because it consumes large amounts of cement, sand, and aggregate, which causes depletion of natural resources. In this study, a step towards sustainable concrete was made by utilizing recycled concrete aggregate (RCA) as a coarse aggregate. However, researchers show that RCA causes a decrease in the performance of concrete due to porous nature. In this study, waste glass (WG) was used as a filler material that filled the voids between RCA to offset its negative impact on concrete performance. The substitution ratio of WG was 10, 20, or 30% by weight of cement, and RCA was 20, 40, and 60% by weight of coarse aggregate. The slump cone test was used to assess the fresh property, while compressive, split tensile, and punching strength were used to assess the mechanical performance. Test results indicated that the workability of concrete decreased with substitution of WG and RCA while mechanical performance improved up to a certain limit and then decreased due to lack of workability. Furthermore, a statical tool response surface methodology was used to predict various strength properties and optimization of RCA and WG.

scholarly journals An Investigation of the Mechanical and Physical Characteristics of Cement Paste Incorporating Different Air Entraining Agents using X-ray Micro-Computed Tomography

Crystals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 23 ◽  
Author(s):  
Mohamed Abd Elrahman ◽  
Mohamed E. El Madawy ◽  
Sang-Yeop Chung ◽  
Stanisław Majer ◽  
Osama Youssf ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Compressive Strength ◽  
Thermal Insulation ◽  
Cement Paste ◽  
Aluminum Powder ◽  
Hollow Microspheres ◽  
Cement Composites ◽  
Micro Computed Tomography ◽  
Cement Pastes ◽  
X Ray

Improving the thermal insulation properties of cement-based materials is the key to reducing energy loss and consumption in buildings. Lightweight cement-based composites can be used efficiently for this purpose, as a structural material with load bearing ability or as a non-structural one for thermal insulation. In this research, lightweight cement pastes containing fly ash and cement were prepared and tested. In these mixes, three different techniques for producing air voids inside the cement paste were used through the incorporation of aluminum powder (AL), air entraining agent (AA), and hollow microspheres (AS). Several experiments were carried out in order to examine the structural and physical characteristics of the cement composites, including dry density, compressive strength, porosity and absorption. A Hot Disk device was used to evaluate the thermal conductivity of different cement composites. In addition, X-ray micro-computed tomography (micro-CT) was adopted to investigate the microstructure of the air-entrained cement pastes and the spatial distribution of the voids inside pastes without destroying the specimens. The experimental results obtained showed that AS specimens with admixture of hollow microspheres can improve the compressive strength of cement composites compared to other air entraining admixtures at the same density level. It was also confirmed that the incorporation of aluminum powder creates large voids, which have a negative effect on specimens’ strength and absorption.

INVESTIGATING THE EFFECT OF NANO SILICA ON THE MECHANICAL PROPERTIES OF HARDENED CEMENT PASTE

2016 ◽  
Vol 3 (1) ◽  
Author(s):  
Sameer Hamoush ◽  
Miguel Picornell ◽  
Taher Abu-Lebdeh
Keyword(s):  
Compressive Strength ◽  
Cement Paste ◽  
Silica Content ◽  
Hydration Process ◽  
Hardened Cement ◽  
Nano Silica ◽  
Hardened Cement Paste ◽  
Cement Replacement ◽  
Water Curing ◽  
Curing Method

This study investigated the compressive strength of hardened cement paste and the formation of calcium silicate hydrate (C-S-H) with the addition of nano silica (SiO2). Through this search, the development of the concretes strength was determined to better understand the process of cement hydration. Compressive strength testing was performed using MTS and Forney testing machines to determine stress-strain curves and elastic modulus of materials. The hydration process and formation of C-S-H and calcium hydroxide (CH) was examined using Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). This study also incorporates the use of vacuum curing, in comparison to that of the traditional water curing method. Results indicate an increase in compressive strength using 1%, 3% and 5% of nano silica to cement replacement by volume in comparison to the control mix (without nano silica). The optimum cement replacement to yield maximum strength was of the 1% nano silica content. The formation of C-S-H increases significantly during the early testing days which correspond with the drastic increase in compressive strength. The hydration process continues to increase throughout the 56 day trails at a moderate rate. The traditional water curing method proves to be more efficient and beneficial than of the vacuum curing method. However, vacuum cured results showed only about a 5% reduction in strength after 56 day tests in comparison to the water curing method.

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