scholarly journals Compression resistance of repaired structural concrete elements after core extraction

2020 ◽  
Vol 13 (4) ◽  
Author(s):  
Tauana Bartikoski ◽  
Vanessa Oerle Kautzmann ◽  
Vinicius de Kayser Ortolan ◽  
Bernardo Fonseca Tutikian ◽  
Regina Modolo
Keyword(s):  
Mechanical Strength ◽  
Cross Section ◽  
Reference Values ◽  
Reliable Method ◽  
Structural Concrete ◽  
Core Drilling ◽  
Concrete Blocks ◽  
Core Extraction ◽  
Concrete Elements ◽  
Compression Resistance

Abstract Core sampling for testing is considered a reliable method to provide information on structural materials and is one of the most implemented techniques in the evaluation of concrete elements. However, core drilling results in a decrease in cross section that can compromise structural mechanical strength even if the extracted section is repaired. Norm NBR 7680-1 recommends dry pack as a repair method but also allows the use of other techniques as long as its effectiveness is proven. This work evaluated the resistance of repaired structural prototypes after core drilling sampling. Concrete blocks with 20 MPa resistance were produced from which cores of 100 mm, 75 mm and 50 mm in diameter were extracted. The blocks were repaired with 20 MPa concrete, grout and dry pack techniques. The reconstitution with concrete showed poorest performance, while dry pack led to strengths even higher when compared to reference values.

SETTING A DIAGRAM APPROACH TO CALCULATING VIBRATED, CENTRIFUGED AND VIBROCENTRIFUGED REINFORCED CONCRETE COLUMNS WITH A VARIATROPIC STRUCTURE

2020 ◽  
pp. 22-34
Author(s):  
Л. Р. Маилян ◽  
С. А. Стельмах ◽  
Е. М. Щербань ◽  
М. П. Нажуев
Keyword(s):  
Experimental Data ◽  
Reinforced Concrete ◽  
Bearing Capacity ◽  
Cross Section ◽  
Concrete Columns ◽  
Reinforced Concrete Columns ◽  
The Cross ◽  
Concrete Elements ◽  
Diagram Approach

Состояние проблемы. Железобетонные элементы изготавливаются, как правило, по трем основным технологиям - вибрированием, центрифугированием и виброцентрифугированием. Однако все основные расчетные зависимости для определения их несущей способности выведены, исходя из основного постулата - постоянства и равенства характеристик бетона по сечению, что реализуется лишь в вибрированных колоннах. Результаты. В рамках диаграммного подхода предложены итерационный, приближенный и упрощенный способы расчета несущей способности железобетонных вибрированных, центрифугированных и виброцентрифугированных колонн. Выводы. Расчет по диаграммному подходу показал существенно более подходящую сходимость с опытными данными, чем расчет по методике норм, а также дал лучшие результаты при использовании дифференциальных характеристик бетона, чем при использовании интегральных и, тем более, нормативных характеристик бетона. Statement of the problem. Reinforced concrete elements are typically manufactured according to three basic technologies - vibration, centrifugation and vibrocentrifugation. However, all the basic calculated dependencies for determining their bearing capacity were derived using the main postulate, i.e., the constancy and equality of the characteristics of concrete over the cross section, which is implemented only in vibrated columns. Results. Within the framework of the diagrammatic approach, iterative, approximate and simplified methods of calculating the bearing capacity of reinforced concrete vibrated, centrifuged and vibrocentrifuged columns are proposed. Conclusions. The calculation according to the diagrammatic approach showed a significantly better convergence with the experimental data than that using the method of norms, and also performs better when using differential characteristics of concrete than when employing integral and particularly standard characteristics of concrete.

scholarly journals Are We Able to Print Components as Strong as Injection Molded?—Comparing the Properties of 3D Printed and Injection Molded Components Made from ABS Thermoplastic

2021 ◽  
Vol 11 (15) ◽  
pp. 6946
Author(s):  
Bartłomiej Podsiadły ◽  
Andrzej Skalski ◽  
Wiktor Rozpiórski ◽  
Marcin Słoma
Keyword(s):  
Tensile Strength ◽  
Injection Molding ◽  
Mechanical Strength ◽  
Cross Section ◽  
Fused Deposition Modeling ◽  
High Strength ◽  
Large Cross Section ◽  
Fused Deposition ◽  
Injection Molded ◽  
The Cross

In this paper, we are focusing on comparing results obtained for polymer elements manufactured with injection molding and additive manufacturing techniques. The analysis was performed for fused deposition modeling (FDM) and single screw injection molding with regards to the standards used in thermoplastics processing technology. We argue that the cross-section structure of the sample obtained via FDM is the key factor in the fabrication of high-strength components and that the dimensions of the samples have a strong influence on the mechanical properties. Large cross-section samples, 4 × 10 mm2, with three perimeter layers and 50% infill, have lower mechanical strength than injection molded reference samples—less than 60% of the strength. However, if we reduce the cross-section dimensions down to 2 × 4 mm2, the samples will be more durable, reaching up to 110% of the tensile strength observed for the injection molded samples. In the case of large cross-section samples, strength increases with the number of contour layers, leading to an increase of up to 97% of the tensile strength value for 11 perimeter layer samples. The mechanical strength of the printed components can also be improved by using lower values of the thickness of the deposited layers.

scholarly journals Modified mortar pad behavior in the transfer of compressive stresses

2016 ◽  
Vol 9 (3) ◽  
pp. 414-434
Author(s):  
J. D. Ditz ◽  
M. K. EL Debs ◽  
G. H. Siqueira
Keyword(s):  
Precast Concrete ◽  
Concrete Strength ◽  
Compressive Load ◽  
Stress Transfer ◽  
Compressive Stresses ◽  
Bonded Phase ◽  
Concrete Blocks ◽  
Load Tests ◽  
Styrene Butadiene ◽  
Concrete Elements

ABSTRACT This research aims to analyze the compressive stress transfer between precast concrete elements using cement mortar pads modified with polypropylene fibers, styrene-butadiene latex and heat-expanded vermiculite. The stress transfer analyses are performed interleaving a cementbearing pad between two concrete blocks, subjecting the entire specimen to different compressive load tests. The parameters analyzed in the tests are: surface roughness (using bosses on the bonded phase of different thicknesses), compressive strength with monotonic and cyclic loadings. The main results obtained in this study are: a) the presence of pad increased the strength in 24% for thicknesses of imperfections of 0.5 mm and approximately 12% for smooth faces blocks; b) gain of effectiveness of the bearing pad when the concrete strength was reduced; c) for cyclic loading, the bearing pad increased in 48% the connections strength.

scholarly journals Incorporation of recycled aggregates from construction and demolition waste in paver blocks

2020 ◽  
Vol 13 (4) ◽  
Author(s):  
Cinthia Maia Pederneiras ◽  
Maria Del Pilar Durante ◽  
Ênio Fernandes Amorim ◽  
Ruan Landolfo da Silva Ferreira
Keyword(s):  
Natural Resources ◽  
Mechanical Strength ◽  
Reference Sample ◽  
Construction And Demolition Waste ◽  
Recycled Aggregates ◽  
World Population ◽  
Fine Aggregate ◽  
Demolition Waste ◽  
Concrete Blocks ◽  
Modified Block

ABSTRACT: The consumption of natural resources and energy increased proportionally with the growth of the world population and its economic level. There was an increasing exponential consumption of natural resources, which implied an increase in environmental impacts. The construction sector is responsible for a very significant production of construction and demolition waste (CDW). Thus, there is a concern in search of a more sustainable final disposal. Many studies have been investigated the development of new materials with the incorporation of recycled aggregates from CDW. This paper presents a study of performance evaluation of concrete blocks produced with CDW. For that purpose, an experimental campaign was performed, including a characterization of the aggregates used. The incorporation of 100% of fine and coarse recycled aggregates. The mixtures were designed according to the condition of the aggregate (dry, washed or saturated). The performance of these blocks was evaluated in terms of mechanical strength and water absorption. Some additional tests were also performed to deeper analyze of the microstructure of these blocks. To assess the durability of the concrete blocks, a full-scale road was built. The results were very positive, since there were no significant differences between the modified concrete blocks and the reference sample (0% of the CDW). The modified block with fine aggregate presented the best performance of all the blocks, concerning mechanical strength. In addition, the performance of concrete blocks with washed recycled aggregates had a better performance compared to the others. The results obtained were satisfactory for the application of the blocks in the streets with low movement and low load.

Evaluation of Cu/Sn-Cu Bump Bonding Processes for 3D Integration Using a Fluxing Adhesive

2010 ◽  
Vol 7 (3) ◽  
pp. 143-145 ◽  
Author(s):  
Alan Huffman ◽  
Christopher Gregory ◽  
Matthew Lueck ◽  
Jason Reed ◽  
Dorota Temple ◽  
...  
Keyword(s):  
Mechanical Strength ◽  
Environmental Protection ◽  
Cross Section ◽  
Sem Analysis ◽  
Electrical Measurements ◽  
3D Integration ◽  
Test Vehicle ◽  
Area Array ◽  
Underfill Material

We present the results of a study to evaluate the use of a fluxing adhesive developed by LORD Corp. in the bonding of Cu/Sn-Cu bump structures for interconnection in 3D integration structures. Using an area-array daisy chain test vehicle with a bump pitch of 25 μm, samples are prepared using our standard bonding methodology and also with the fluxing adhesive and then evaluated through electrical measurements and cross section SEM analysis. The results show that the use of the fluxing underfill material results in a well-formed bond between the Cu and Cu/Sn bumps and encapsulates the interconnects to provide environmental protection and additional mechanical strength to the interconnect array.

CHANGES IN THE CODE OF RULES FOR THE DESIGN OF STRUCTURES MADE OF CONCRETE WITH POLYMER COMPOSITE REINFORCEMENT

2021 ◽  
pp. 51-55
Author(s):  
Takhir MUKHAMEDIYEV
Keyword(s):  
Polymer Composite ◽  
Cross Section ◽  
Cross Sections ◽  
Base Point ◽  
Limit States ◽  
Axial Tension ◽  
Line Diagram ◽  
Moment Of Resistance ◽  
Concrete Elements ◽  
Composite Reinforcement

The article presents information about the changes made to the code of rules for the design of concrete structures reinforced with polymer composite reinforcement. New rules for the formation of relative deformations at the base point of a two-line diagram of concrete under axial tension, used to calculate reinforced concrete elements for the second group of limit states, are described. The rules for calculating re-reinforced structures of T-or I-beam cross-sections with a shelf in a compressed zone by the method of limiting forces are presented. The rules for taking into account the inelastic properties of concrete of the stretched zone when determining the elastic- plastic moment of resistance for the extreme stretched fibre of concrete with a rectangular cross-section and a T-shape with a shelf located in the compressed zone are clarified.

scholarly journals Two-layer reinforced concrete panels with uniformly compressed sections

2020 ◽  
Vol 315 ◽  
pp. 07004
Author(s):  
Dmitry Mailyan ◽  
Alik Blyagoz ◽  
Konstantin Kretinin
Keyword(s):  
Reinforced Concrete ◽  
Cross Section ◽  
Concrete Panels ◽  
The Creation ◽  
Concrete Elements

The paper contains the issues related to the creation of a non-uniform prestress cross-section of reinforced concrete elements compressed during operation of working with a one-way eccentricity of the resultant longitudinal forces.

Strength Model Analysis of the Foam Concrete

2012 ◽  
Vol 450-451 ◽  
pp. 610-613
Author(s):  
Long Fei Cheng ◽  
Ya Nan Fu ◽  
Ting Qiang Zhou
Keyword(s):  
Cross Section ◽  
Unit Volume ◽  
Concrete Strength ◽  
Volume Ratio ◽  
Weak Links ◽  
Strength Model ◽  
Foam Concrete ◽  
Large Space ◽  
Concrete Aggregates ◽  
Compression Resistance

Foam concrete aggregates and inclusions have greater strength, but the pore almost has no compression resistance; hydrated cements and pores are the weak links in the pressure cross-section of the foam concrete. As for unit volume of foam concrete, cement accounts for a large space and the pore occupies less, so the block intensity will be larger. Considering mechanical properties of the aggregates and hydrous cements are different, the volume ratio of hydrous cements to the sum of cements and pores is used to build the strength model of foam concrete, which can be simple and feasible. It can response the foam concrete strength characteristics more accurately.

scholarly journals Use of Recycled Tyre Rubber in Non-structural Concrete

2018 ◽  
Vol 203 ◽  
pp. 06001
Author(s):  
Muhammad Bilal Waris ◽  
Hussain Najwani ◽  
Khalifa Al-Jabri ◽  
Abdullah Al-Saidy
Keyword(s):  
Compressive Strength ◽  
Water Absorption ◽  
Coarse Aggregate ◽  
Partial Replacement ◽  
Fine Aggregate ◽  
Structural Concrete ◽  
Cement Ratio ◽  
Mix Proportion ◽  
Water To Cement Ratio ◽  
Concrete Blocks

To manage tyre waste and conserve natural aggregate resource, this research investigates the use of waste tyre rubber as partial replacement of fine aggregates in non-structural concrete. The research used Taguchi method to study the influence of mix proportion, water-to-cement ratio and tyre rubber replacement percentage on concrete. Nine mixes were prepared with mix proportion of 1:2:4, 1:5:4 and 1:2.5:3; water-to-cement ratio of 0.25, 0.35 and 0.40 and rubber to fine aggregate replacement of 20%, 30% and 40%. Compressive strength and water absorption tests were carried out on 100 mm cubes. Compressive strength was directly proportional to the amount of coarse aggregate in the mix. Water-to-cement ratio increased the strength within the range used in the study. Strength was found to be more sensitive to the overall rubber content than the replacement ratio. Seven out of the nine mixes satisfied the minimum strength requirement for concrete blocks set by ASTM. Water absorption and density for all mixes satisfied the limits applicable for concrete blocks. The study indicates that mix proportions with fine to coarse aggregate ratio of less than 1.0 and w/c ratio around 0.40 can be used with tyre rubber replacements of up to 30 % to satisfy requirements for non-structural concrete.

Response of structural concrete elements to severe impulsive loads

1994 ◽  
Vol 53 (1) ◽  
pp. 119-130 ◽  
Author(s):  
T. Krauthammer ◽  
H.M. Shanaa ◽  
A. Assadi
Keyword(s):  
Structural Concrete ◽  
Impulsive Loads ◽  
Concrete Elements
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