scholarly journals Study on Durability and Pore Characteristics of Concrete under Salt Freezing Environment

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7228
Author(s):  
Xinchao Zheng ◽  
Fang Liu ◽  
Tao Luo ◽  
Yanfu Duan ◽  
Yu Yi ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Frost Resistance ◽  
Three Dimensional ◽  
Clean Water ◽  
Two Dimensional ◽  
Nacl Solution ◽  
Freezing And Thawing ◽  
Pore Characteristics ◽  
Resistance Durability

The macroscopic mechanical properties and frost resistance durability of concrete are closely related to the changes in the internal pore structure. In this study, the two-dimensional and three-dimensional ICT (Industrial Computerized Tomography) pore characteristics of C30 concrete specimens before and after freezing and thawing in clean water, 5 wt.% NaCl, 5 wt.% CaCl2, and 5 wt.% CH3COOK solution environments are obtained through concrete frost resistance durability test and ICT scanning technology. The effects of pore structure changes on concrete frost resistance, durability, and compressive strength mechanical properties after freezing and thawing cycles in different salt solution environments are analyzed. This paper provides new means and ideas for the study of concrete pores. The results show that with the increase in the freezing and thawing times, the concrete porosity, two-dimensional pore area, three-dimensional pore volume, and pore number generally increase in any solution environment, resulting in the loss of concrete compressive strength, mortar spalling, and the decrease in the relative dynamic elastic modulus. Among them, the CH3COOK solution has the least influence on the concrete pore changes; the NaCl solution has the greatest influence on the change in the concrete internal porosity. The damage of CaCl2 solution to concrete is second only to the NaCl solution, followed by clean water. The increase in the concrete internal porosity from high to low is NaCl, CaCl2, clean water, and CH3COOK. The change in the pore volume of 0.1 to 1 mm3 after the freeze–thaw cycle is the main factor for reducing concrete strength. The test results have certain guiding value for the selection of deicing salt in engineering.

Experimental Research on New Concrete Air Entraining Agent

2011 ◽  
Vol 194-196 ◽  
pp. 1063-1068
Author(s):  
Bao Min Wang ◽  
Ni Tu
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Dynamic Modulus ◽  
Frost Resistance ◽  
Loss Rate ◽  
Strength Loss ◽  
Weight Loss Rate ◽  
Thaw Cycle ◽  
New Type ◽  
Resistance Durability

Using waste to produce a new type of air entraining agent (AEA), carrying out research of the concrete’s mixture performance, mechanical properties and frost resistance durability after mixing with the AEA, with results showing that amount of air entrained in the concrete mixture and the water reducing rate increases along with the increase of the addition of the new AEA, and its compressive strength loss laws are similar with that of normal AEAs. During the frost-thaw cycle test, when the weight loss rate has reached its limit, concrete with the new AEA added can withstand almost 300 cycles, and at this time the relative dynamic modulus of the concrete, when the amount of air entrained in it is 4.5%, is 83.5%, and the relative dynamic modulus is 85.4% when the amount of air entrained is 5.3%. The addition of the AEA has obviously improved the pore structure of the concrete, and significantly raising its frost resistance durability.

Three-Dimensional Structure of Cloned T3 Connector Protein at 1.6nm Resolution

1990 ◽  
Vol 48 (1) ◽  
pp. 282-283
Author(s):  
José L. Carrascosa ◽  
José M. Valpuesta ◽  
Hisao Fujisawa
Keyword(s):  
Dna Sequences ◽  
Expression Vector ◽  
Three Dimensional ◽  
Deae Cellulose ◽  
Dna Packaging ◽  
Dimensional Structure ◽  
Two Dimensional ◽  
Freezing And Thawing ◽  
Three Dimensional Structure ◽  
Dimensional Reconstruction

The head to tail connector of bacteriophages plays a fundamental role in the assembly of viral heads and DNA packaging. In spite of the absence of sequence homology, the structure of connectors from different viruses (T4, Ø29, T3, P22, etc) share common morphological features, that are most clearly revealed in their three-dimensional structure. We have studied the three-dimensional reconstruction of the connector protein from phage T3 (gp 8) from tilted view of two dimensional crystals obtained from this protein after cloning and purification.DNA sequences including gene 8 from phage T3 were cloned, into Bam Hl-Eco Rl sites down stream of lambda promotor PL, in the expression vector pNT45 under the control of cI857. E R204 (pNT89) cells were incubated at 42°C for 2h, harvested and resuspended in 20 mM Tris HC1 (pH 7.4), 7mM 2 mercaptoethanol, ImM EDTA. The cells were lysed by freezing and thawing in the presence of lysozyme (lmg/ml) and ligthly sonicated. The low speed supernatant was precipitated by ammonium sulfate (60% saturated) and dissolved in the original buffer to be subjected to gel nitration through Sepharose 6B, followed by phosphocellulose colum (Pll) and DEAE cellulose colum (DE52). Purified gp8 appeared at 0.3M NaCl and formed crystals when its concentration increased above 1.5 mg/ml.

Study on the Mechanical Properties and Frost Resistance of Recycled Concrete Prepared by Village Construction Wastes

2011 ◽  
Vol 418-420 ◽  
pp. 406-410
Author(s):  
Jun Liu ◽  
Yao Li ◽  
Dan Dan Hong ◽  
Yu Liu
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Frost Resistance ◽  
Cement Mortar ◽  
Strength Loss ◽  
Recycled Concrete ◽  
Recycled Aggregate ◽  
Replacement Rate ◽  
Concrete Mechanical Properties ◽  
Better Than

Abstract. Recycled aggregate—rural building material wastes pretreated by cement mortar—are applied into concrete with different replacement rates: 0, 25%, 50%, 75%, and 100%. Results from measurements of compressive strength, cleavage tensile strength, mass loss after fast freeze-thaw cycles, and compressive strength loss indicate that a different recycled aggregate replacement rate certainly influences concrete mechanical properties and frost resistance. Recycled aggregate replacement rates less than 75% performs better than common concrete. Data from the 100% replacement rate is worse than that of rates less than 75% but still satisfy the general demands of GB standard on C30 concrete.

scholarly journals Estimation of the compression strength and surface roughness of the as-built SLS components using weibull distribution

2021 ◽  
pp. 1-6
Author(s):  
Hamaid Mahmood KHAN
Keyword(s):  
Mechanical Properties ◽  
Surface Roughness ◽  
Compressive Strength ◽  
Weibull Distribution ◽  
Selective Laser Sintering ◽  
Three Dimensional ◽  
Random Variable ◽  
Production Quality ◽  
Laser Source ◽  
Distribution Method

Selective laser sintering (SLS) is a process of fabrication of three-dimensional structures by fus- ing powder particles using a guided laser source. The uncertainty in the mechanical properties of the SLS parts fabricated at the same time and with the same process parameters can affect the repeatability of the SLS process. A vast difference in the mechanical properties of the concurrently processed parts can lower the production quality of the batch. Therefore, the param- eters are required to be design based on the most probable outcome of the desired properties. Weibull distribution is one such statistical-based probability distribution method to measure the likelihood of the occurrence of a value of any random variable falling within a particular range of values. Here, the Weibull distribution was used to measure the relative likelihood (90% probability) of the surface roughness and the compressive strength values of the SLS-built polyamide PA2200 components in the given sample space that was obtained from 20 random samples. The results show that the variance in the surface roughness (scan and built plane) and the compressive strength values were in the range of 6–7 μm and around 10 MPa, respectively. Moreover, the surface roughness of the two orthogonal planes with 90% reliability was measured at 14.81 μm (scan plane) and 12.15 μm (built plane). Similarly, the yield strength and the compressive strength with 90% reliability were found 25.87 MPa and 62.64 MPa, respectively.

scholarly journals Influence of Restrained Condition on Mechanical Properties, Frost Resistance, and Carbonation Resistance of Expansive Concrete

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2136
Author(s):  
Nguyen Duc Van ◽  
Emika Kuroiwa ◽  
Jihoon Kim ◽  
Hyeonggil Choi ◽  
Yukio Hama
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Frost Resistance ◽  
Total Porosity ◽  
Length Change ◽  
Ratio Test ◽  
Expansive Concrete ◽  
Restrained Condition ◽  
Carbonation Resistance ◽  
Compressive Strength Test

This paper presents the results of an experimental investigation of the effect of the restrained condition on the mechanical properties, frost resistance, and carbonation resistance of expansive concrete with different water–binder ratios. In this study, length change ratio test, expansion strain test, compressive strength test, mercury intrusion porosimetry test, underwater weighing test, freezing–thawing test, and accelerated carbonation test were performed to evaluate the mechanical properties, pore size distribution, total porosity, and durability of expansive concrete under both restrained and unrestrained conditions. The test results indicate that the length change ratio and expansion strain of the expansive concrete were controlled by the restrained condition. The compressive strength of expansive concrete was enhanced by the triaxial restraining when the amount of expansive additive was 40 kg/m3 of concrete. Two hypotheses were described to explain the change of pore structure change expansive mortar. The results also indicate that the carbonation resistance and frost resistance were improved by the uniaxial restrained condition. Furthermore, the effect of the restrained condition must be considered to evaluate not only the experimental results of the expansive concrete with a high EX replacement level but also the expansive concrete combining other cement replacement materials.

scholarly journals Influence of Mullite Wool Waste on the Properties of Ceramics

1970 ◽  
Vol 17 (1) ◽  
pp. 80-85
Author(s):  
Jurgita MALAIŠKIENĖ
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Water Absorption ◽  
Firing Temperature ◽  
Frost Resistance ◽  
Effective Porosity ◽  
Flow Reserve ◽  
Optimum Quantity ◽  
Ceramic Samples ◽  
Porous Volume

In the paper, the influence of mullite wool waste additive on the properties of building ceramics is analysed. For that purpose four formation masses were prepared, dried and fired at the analogous regimes (maximum firing temperature 1080 °C). The fired samples were used to determine the structural and physical-mechanical properties. The values of these parameters are analysed: water absorption, total and effective porosity, rate of capillary mass flow, reserve of porous volume, compressive strength, density and estimated exploitation frost resistance. It has been determined that mullite wool waste can be applied to the production of building ceramics and the optimum quantity of waste in a formation mass is 10 % according to weight. Water absorption of those ceramic samples was less than 4 %, compressive strength was 28.6 MPa, density - 2033 kg/m3, forecasted resistance to frost about 400 cycles.http://dx.doi.org/10.5755/j01.ms.17.1.255

scholarly journals The effect of the aggregate type on the properties of pavement concrete

2018 ◽  
Vol 67 (4) ◽  
pp. 83-94
Author(s):  
Grzegorz Rogojsz ◽  
Damian Skupski ◽  
Bartosz Januszewski
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Modulus Of Elasticity ◽  
Frost Resistance ◽  
Laboratory Tests ◽  
Indirect Tensile Strength ◽  
Cement Concrete ◽  
Pore Characteristics ◽  
Road Surfaces ◽  
Indirect Tensile

This paper presents the results of laboratory tests on the properties of cement concrete containing various types of aggregate. The purpose of the tests was to determine the effect of aggregate on compressive strength, indirect tensile strength, air pore characteristics, frost resistance and the modulus of elasticity of concrete for road surfaces. The aggregate that meets the requirements for road concrete was determined on the basis of the tests. Keywords: road concrete, frost resistance of aggregate, frost resistance of road concrete.

scholarly journals KARAKTERISTIK SELF COMPACTING CONCRETE (SCC) TANPA CURING

2018 ◽  
Author(s):  
erniati
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Fresh Concrete ◽  
Strength Test ◽  
Splitting Tensile Strength ◽  
Good Resistance ◽  
Self Compacting Concrete ◽  
Compressive Strength Test ◽  
Resistance Durability

Self Compacting Concrete (SCC) is one solution to get concrete construction which it has good resistance. Durability of concrete was obtained by the good concrete compaction to be done by a skilled workforce. However, one of the negligence that often occur in the field ie after casting they was ignoring curing of the hardening concrete. This study discusses the workability of fresh concrete and mechanical properties (compressive strength and splitting tensile strength) on SCC without curing. Testing of the concrete workability based on EFNARC standard. The mechanical properties test based on ASTM standards. The method Compressive strength test based on ASTM standards 39 / C 39M - 12a, whereas splitting tensile strength accordance standard ASTM C496 / C496M-11. The results of the study indicate that the SCC without curing effect on the reduction in compressive strength at ages 1, 3, 7, 28, and 90 days in a row at 4.11 MPa (16.1%); 4.90 MPa (13.9%); 6.64 MPa (13.1%); and 6, 72 MPa (12.75%). Splitting tensile strength decreased respectively by 0.1 MPa (3.25%); 0.26 MPa (7.99%); 0.4 MPa (9.52%); and 0.39 MPa (9.16%).

scholarly journals Frost resistance of cement-sand and concrete beams during unilateral freezing

2021 ◽  
Vol 2 (1) ◽  
pp. 64-74
Author(s):  
Nepomyach Alexander Nikolaevich ◽  
Vyrovoy Valeriy Nikolaevich ◽  
Chistyakov Artem Aleksaedrovich
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Frost Resistance ◽  
Bending Strength ◽  
Concrete Beams ◽  
Transmission Rate ◽  
Beam Structure ◽  
Freeze Thaw ◽  
Damage Coefficient ◽  
Negative Temperatures

Abstract The work investigates changes in the beam structure under the action of local freezing, which leads to a change of the mechanical properties of the material and, consequently, of the beam structure. Two types of beam samples were used: from cement-sand mortar and from concrete. The work investigates the change in the development of deformations depending on the conditions of freezing of samples. The second accelerated method for assessing frost resistance was chosen according to DSTU B В.2.7-47-96. An accelerated method was chosen for assessing frost resistance at the temperature of -20 ±2 C°. After every five freeze-thaw cycles, the following changes were monitored: mass, water absorption, ultrasound transmission rate, damage coefficient, tensile bending strength, splitting strength, compressive strength, carbonization depth. The results showed that both in concrete and in mortar samples, the compressive strength after freezing was lower by 8% and 15% accordingly. The experimental results obtained confirm the assumptions made that the frost resistance of the material depends on the conditions of exposure of negative temperatures on products and structures and it can be used in a wider range of construction which will push regional development.

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