Influence of Structural Characteristics on Concrete Strength under Dynamic Effects

2019 ◽  
Vol 968 ◽  
pp. 368-379
Author(s):  
Andrii A. Plugin ◽  
Olena Palant ◽  
Dmytro Plugin ◽  
Sergii Miroshnichenko
Keyword(s):  
Mechanical Properties ◽  
Crack Resistance ◽  
Structural Characteristics ◽  
Concrete Strength ◽  
Physical And Mechanical Properties ◽  
Dynamic Effects ◽  
Cement Ratio ◽  
Fine Aggregates ◽  
Water To Cement Ratio ◽  
Optimal Values

The article deals with theoretical and experimental research into dependency of crack resistance of concrete under dynamic effects on coefficients of grain separation of coarse and fine aggregates. It was established that these dependencies were of extreme nature. The research yielded the optimal values of coefficients of grain separation of coarse and fine aggregates, cement particles, and also water-to-cement ratio for the materials under study; these factors provided the best physical and mechanical properties of concrete, including its crack resistance under dynamic effects, both impacts and vibrations..

scholarly journals Lime based Dry Mixes with Carbonate Aggregates

2019 ◽  
Vol 8 (11) ◽  
pp. 3289-3292 ◽  
Keyword(s):  
Mechanical Properties ◽  
Quartz Sand ◽  
Carbonate Rocks ◽  
Physical And Mechanical Properties ◽  
Lime Mortar ◽  
Fine Aggregates ◽  
Lime Mortars ◽  
The Matrix ◽  
Optimal Values ◽  
Quarry Dust

The use of carbonate rocks as aggregates for cement concretes and mortars is limited due to their insufficient strength and the threat of corrosion. The use of quarry dust from crushing carbonate rocks are technically and economically feasible in building compositions based on air-hardening lime. The results of the study of the effect of replacing a part of quartz sand in lime mortar by limestone and dolomite fine aggregates on the basic physical and mechanical properties of lime mortars for restoration are presented in the paper. The matrix of planning experiments, which allows increasing the informativity of the research results in order to reduce the number of experiments in the search for optimal values, is proposed. The efficiency of replacement of the quartz sand with quarry dust of carbonate rocks in the production of dry mixes for restoration is shown.

scholarly journals RESEARCH OF EFFECT OF DPEI-PROCESSING OF SHIITAKE FRUIT BODY ON PHYSICAL AND MECHANICAL PROPERTIES OF MUSHROOM SUSPENSION

2018 ◽  
Vol 41 (1) ◽  
pp. 27-33
Author(s):  
N.O. Sharkova ◽  
E.К. Zhukotskyi ◽  
Т.Y. Тurchyna ◽  
H.V. Dekusha ◽  
A.A. Makarenko
Keyword(s):  
Mechanical Properties ◽  
Dynamic Viscosity ◽  
Structural Characteristics ◽  
Specific Energy Consumption ◽  
Fruit Body ◽  
Heterogeneous Systems ◽  
Physical And Mechanical Properties ◽  
Water Soluble ◽  
Shiitake Mushroom ◽  
Working Bodies

The use of discrete-pulse energy input (DPEI) mechanisms in various industries has become a reliable tool for the intensification of heat and mass transfer processes in various technological lines and reduction of specific energy consumption. The study of structural transformations in heterogeneous systems under influence of mechanisms of DPEI opens up new possibilities for their use as evidenced by this article. Under certain conditions it is possible to prepare a mushroom suspension with specified characteristics for drying and enhance medicinal properties of the obtained powder product while retaining all valuable components of feedstock. The article presents the results of research of DPEI-processing effect of the shiitake mushroom fruit body on the on physical and mechanical properties and structural characteristics of the mushroom suspension. The influence of hydro module, temperature of the suspension and the layout of the working bodies of the rotor-pulse apparatus (RPA) on its dynamic viscosity was studied and the possibility of reducing viscosity by 2-3 times is shown.  An analysis of mushroom suspension microstructure has showed that with a certain layout of the working bodies of the RPA it is possible to control the degree of dispersion of particles and change the spatial structure of the aggregates in the volume of the dispersion medium. It is determined that self-organization of spatial aggregates from individual hyphae in such suspensions occurs over time. Moreover, the smaller the size of hyphae (≤ 25 microns after the RPA of the first version of the arrangement: rotor-stator-rotor) are, the larger the size of the spatial aggregates are formed. After the RPA with the second layout option, the fragments of hyphae had sizes ≥ 50 μm, but the dimensions of the spatial aggregates were three times smaller. It is found that after three times passing of the mushroom suspension through the RPA and its subsequent treatment in the cavitation device, the dynamic viscosity of the suspension is reduced by 20%. Confirmation of the the effectiveness of the DPEI-mechanisms in obtaining mushroom suspension is that due to the hydromechanical destruction of the polysaccharide structures of the chitin-glucan complex of the shiitake mushroom the content of the bioavailable complex of water-soluble oncostatic and immunoregulatory polysaccharides in the powder obtained by drying the mushroom suspension in an experimental spray dryer increased 6 times. References 13, figures 6.

Effects of Fly Ash Addition on Compressive Strength and Flexural Strength of Foamed Cement Composites

2013 ◽  
Vol 795 ◽  
pp. 664-668 ◽  
Author(s):  
Roshasmawi Abdul Wahab ◽  
Mohd Noor Mazlee ◽  
Shamsul Baharin Jamaludin ◽  
Khairul Nizar Ismail
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Fly Ash ◽  
Flexural Strength ◽  
Cement Composites ◽  
Volume Percent ◽  
Foaming Agent ◽  
Cement Ratio ◽  
Water To Cement Ratio

In this study, the mixing of polystyrene (PS) beads and fly ash as a sand replacement material in foamed cement composites (FCC) has been investigated. Specifically, the mechanical properties such as compressive strength and flexural strength were measured. Different proportions of fly ash were added in cement composites to replace the sand proportion at 3 wt. %, 6 wt. %, 9 wt. % and 12 wt. % respectively. The water to cement ratio was fixed at 0.65 meanwhile ratios of PS beads used was 0.25 volume percent of samples as a foaming agent. All samples at different mixed were cured at 7 and 28 days respectively. Based on the results of compressive strength, it was found that the compressive strength was increased with the increasing addition of fly ash. Meanwhile, flexural strength was decreased with the increasing addition of fly ash up to 9 wt. %. The foamed cement composites with 12 wt. % of fly ash produced the highest strength of compressive strength meanwhile 3 wt. % of fly ash produced the highest strength of flexural strength.

Microstructure and Mechanical Properties of Cement/Fly Ash/Natural Rubber Composites

2017 ◽  
Vol 866 ◽  
pp. 195-198
Author(s):  
Rakchanok Promudom ◽  
Suparut Narksitipan ◽  
Nittaya Jaitanong
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Portland Cement ◽  
Natural Rubber ◽  
Natural Rubber Latex ◽  
Physical And Mechanical Properties ◽  
Ammonia Solution ◽  
Rubber Latex ◽  
Water To Cement Ratio ◽  
Natural Rubber Composites

The physical and mechanical properties of Portland cement (PC) - natural rubber latex (NRL) - fly ash (FA) composites have been investigated. The latex per cement ratios that use in this experiment are 0, 5, 7.5 and 10% by weight of cement. Portland cement (PC) was partially replaced with fly ash 0-40% by weight of binder. Water to cement ratio were used in range of 0.305-0.385 (by weight not include water in latex). Nonionic surfactant was added in cement before mixed with natural rubber latex. In addition, to provide latex from natural rubber latex, the ammonia solution is added into natural rubber. The specimens were packing into an iron mold which sample size of 4x4x16 cm3. Moreover, the PC-NRL-FA composites were cured in water for 7 and 28 days at room temperature before measurement. Then, mechanical properties (flexural strength) and microstructure were studied.

scholarly journals Study of Physical and Mechanical Properties of Centrifuged Concrete

2019 ◽  
Vol 18 (4) ◽  
pp. 319-329
Author(s):  
I. I. Palevoda ◽  
S. M. Zhamoidzik ◽  
D. S. Nekhan ◽  
D. S. Batan
Keyword(s):  
Mechanical Properties ◽  
Water Content ◽  
Cross Section ◽  
Outer Layer ◽  
Concrete Strength ◽  
Concrete Structures ◽  
Physical And Mechanical Properties ◽  
Concrete Mixture ◽  
Density Analysis

The paper presents a complex of laboratory and theoretical studies of physical and mechanical properties in centrifuged concrete while using samples of sectoral cross-section which are cut in layers from a finished product. A post made of concrete having B40 grade for compression strength and manufactured while using centrifugation with the help of РТЦ-5 machine. Assessment of heterogeneity across section thickness has been carried out by visual determination of composition changes in cross section, determination of strength, density of the obtained concrete samples, and water content over cross section of concrete mix. According to the results of a visual study on composition of a concrete structure it has been revealed that 1/8 part of the structure (from an inner surface) does not have a large aggregate. Later, as it moves to periphery, there is an increase in coarse aggregate and a decrease in size and number of cells between grains of gravel. An analysis of experimental data has shown that properties of the centrifuged concrete in samples being sawn in layers change significantly: density of concrete in samples of an inner layer is lower by 8 % than in samples of an outer layer, and compressive strength of concrete – by 34 %, water content of concrete mixture of samples of the inner layer has turned out to be by 43 % higher than in samples of the outer layer. Approximating curves showing regularities of changes in density, concrete strength, water content of concrete mixture over thickness have been constructed in the paper. Linear and exponential equations have been obtained that describe changes in physical and mechanical properties of centrifuged concrete over section depending on structure properties as a whole, which, taking into account the obtained correction factors k1 and k2, can be used with an acceptable level of confidence in practical calculations of centrifuged concrete structures. Relationship between strength of centrifuged concrete varying over cross section and action of a centrifugal force of inertia has been revealed in the paper. An equation has been obtained that relates the strength of centrifuged concrete to its density. Analysis of the research results makes it possible to assert that the main source of loading perception in centrifuged concrete structures is outer layers.

scholarly journals Optimization of the Physical and Mechanical Properties of Grouting Material for Non-Soil-Squeezing PHC Pipe Pile

Crystals ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 10
Author(s):  
Zhenkun Hou ◽  
Mengxiong Tang ◽  
Shihua Liang ◽  
Yi Zhu
Keyword(s):  
Mechanical Properties ◽  
Physical And Mechanical Properties ◽  
Reducing Agent ◽  
Curing Time ◽  
Shrinkage Ratio ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Cement Mixture ◽  
Early Strength ◽  
Late Stages

The physical and mechanical properties of grouting materials greatly affect the friction resistance and the bearing performance of a non-soil-squeezing PHC pipe pile. Orthogonal tests for four factors at five levels were carried out to optimize the proportion of the water–cement mixture by using Portland cement as a raw material and a water-reducing agent, expansion agent and early-strength agent as additives. The following conclusions were obtained: (1) Both the water–cement ratio and the dosage of water-reducing agent are positively correlated with the fluidity of the water–cement mixture and have the greatest influence on the fluidity, followed by the expansion agent and early-strength agent. The saturation point of the water-reducing agent is 1.5%. (2) The strength of the grouting body decreases linearly with the increase of the water–cement ratio, and the dosage of the water-reducing agent has no obvious effect on the strength. As the dosage of expansion agent increases, the strength of the grouting body decreases rapidly. The expansion agent mainly plays a key role in the middle and late stages of the hardening process of the slurry. Early-strength agents have a greater impact on the early strength, but less on the later strength. When the slurry is solidified for 3 h, the early-strength agent has the greatest impact on the strength with an optimal dosage of 5%. (3) The volume of the grouting body has an inverse relationship with the water–cement ratio, and the optimal amount of expansion agent is 12%. The incorporation of an expansion agent makes the volume increase of the grouting body exceed the volume shrinkage ratio caused by the hardening of the grouting body with a curing time of more than 3 days, ensuring a slight increase in the volume of the grouting body. After 3 days, even though the effect of the expansion agent is gradually weakened, it can still ensure that the volume of the grouting body does not shrink. With the increase of the amount of water-reducing agent, the volume of the grouting body gradually decreases. When the amount of water-reducing agent exceeds 1.5%, the volume of the grouting body no longer decreases. (4) The early-strength agent has almost no effect on the volume of the grouting body. When the curing time is 3 h, the water–cement ratio has the greatest influence on the volume of the grouting body, followed by the water-reducing agent, and, finally, the expansion agent. After 3 h, the water–cement ratio still has the greatest influence, and the influence of the expansion agent gradually exceeds that of the water-reducing agent. The water-reducing agent mainly affects the volume of the grouting body in the water separation stage, and the expansion agent mainly plays a role in the middle and late stages of the slurry solidification. After optimized ratio analysis, the fluidity of the water–cement mixture can be improved, the volume shrinkage ratio rate can be lowered and the early strength can be increased.

Proportion Design of Concrete with Gravel-Crushed Proto-Machine-Made Sand

2011 ◽  
Vol 295-297 ◽  
pp. 436-439
Author(s):  
Chang Yong Li ◽  
Qiu Yan Sun ◽  
Feng Lan Li
Keyword(s):  
Mechanical Properties ◽  
Water Content ◽  
Fresh Concrete ◽  
Hardened Concrete ◽  
Cement Ratio ◽  
Water To Cement Ratio

Experiments were conducted to study the workability of fresh concrete and basic mechanical properties of hardened concrete with gravel-crushed proto-machine-made sand. Effects of water to cement ratio and content of stone powder were mainly considered. Based on the test and before, the values of practical parameters in formula are obtained for calculating mixed strength of concrete, and the beneficial range of water to cement ratio is proposed. Meanwhile, the reasonable water content, sand ratio and content of stone powder are also suggested.

The Effect of Redistribution of the Mixing Water of the Concrete Lining on its Quality

2016 ◽  
Vol 843 ◽  
pp. 103-110
Author(s):  
Yuri Kulikov
Keyword(s):  
Mechanical Properties ◽  
Physical And Mechanical Properties ◽  
External Pressure ◽  
Concrete Lining ◽  
Residual Water ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Axial Forces ◽  
Roof Part ◽  
Mixing Water

In the heart of the processes of formation of physical and mechanical properties of secondary lining of underground structures is the residual water-cement ratio, which indicates the extraction of the mixing water of the concrete mixture under the action of external pressure forces. This article examines the nature of the redistribution of the mixing water in the concrete lining of the tunnels. Under the influence of radial and axial forces from laid concrete mix there is an increase in water-cement ratio in the direction from the sole to the vault head of the tunnel. This leads to deterioration of physical and mechanical properties of the lining in the roof part of the tunnel. When calculating the strength and water resistance of the secondary concrete tunnel lining the characteristics of the concrete type by strength and waterproof, adjusted by the weakest part of the lining – its roof part – should be taken into account. The analysis of influence on the technology of erection of the lining is given.

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