Ordinary Sand Research Articles

FIBER REINFORCED SAND BACKFILL FOR UNDERGROUND PEDESTRIAN CROSSINGS

Crosswalk is an essential element of the transport system of any city. A priority assignment in any such crossing is to ensure the safety of pedestrians. Underground pedestrian crossings are much safer than crossings at another level, but they lose in attraction when it comes to cost. The cost of the construction of an underground pedestrian crossing often leads to project abandonment. The cost of construction can be reduced through the use of flexible corrugated metal structures instead of ordinary concrete structures. The stress-strain state of the structural shells need to be known to facilitate their rational design. The stress-strain state of flexible corrugated metal shells largely depends on the strength and deformation characteristics of the surrounding soil. Therefore, improving the characteristics of backfill soil is an urgent task in reducing the cost of construction for such tunnels. One way to improve the strength and deformation characteristics of soils is the use of reinforcement. Currently, there are a large number of reinforcement schemes and also associated reinforcing materials. One of the most prospective methods of soil reinforcement is the use of fibre filaments. Fibre reinforced soils have significantly higher strength and deformation characteristics in comparison with unreinforced soils. Numerical modelling of a tunnel shell made out of a corrugated metal structure was undertaken to evaluate the effectiveness of using fibre reinforced sand. Ordinary sand and sand reinforced with polypropylene fibres have been used as soil backfill. The calculation results for a pedestrian tunnel structure involving different strength and deformation characteristics of the backfill soil are presented in this article.

Characteristics of Sand of the Oueds in the Region of Oued Righ (Oued N'SA, Oued M’ZAB and Oued Rtem) in the Making of Concrete in the Arid Regions

We usually use, in the making of reinforced concrete, the ordinary sand which is generally extracted from quarry, oueds or from beaches. This material is a necessary element for the concrete, but unfortunately, it is not always available in market and hence makes both rare and expensive despite of its gigantic reserve in the many oueds in the region of oued righ. We have chosen the sand of the oueds as a substitution material in the composition of the concrete taken precisely from Oued N'ssa - Oued M’ zab and Oued Rtem. We have opted for an experimental study that deals with the physic-mechanical and chemic characteristics of the sand and its use in the field of concrete construction, as well as the property of this based-sand concrete.

Numerical Simulation of Shielding Performance of Different Aggregate Concrete

The shielding properties of different energy (1MeV, 2MeV, 3MeV) γ-rays were studied for the concrete with magnetite, magnetite ore, barite, barite ore, steel ball, ordinary sand and crushed stone as aggregates. Based on MCNP5 program, the shielding performance of different aggregate concrete was simulated and analyzed, and the attenuation coefficients, transmittance and transmission spectrum of the three-rays concrete through different aggregate concrete were obtained. Research indicates：For the same energy γ-rays, the shielding effect of concrete with steel ball, magnetite ore and magnetite as the aggregate is the best, and the shielding effect of the concrete decreases with the increase of γ-rays energy. And the transmittance of γ-rays of the same aggregate concrete is different; when γ-rays energy is higher than 1.02MeV, from the transmission spectrum can be seen, γ-rays and concrete electron-pair effect and the Compton effect probability increases

The effect of temperature on the compressive strength of concrete

Not available

An Experimental Study of pH Value and Flexural Strength of Cement Sand Mortar with Surface Untreated Multi-Walled CNTs

Background/Objectives: The paper describes the study carried out on test specimens of cement mortar composite admixed with multi-walled carbon nanotubes (CNTs) in order to investigate the physical property changes under nano-level hydration. Methods/Statistical Analysis: In this study, the standard engineering tests such as pH value identification, flexural strength test and compression strength tests were carried out for both control and test specimens which were cast and cured as per Indian Standard specifications. Test specimens of cement mortar composite consisted of ordinary Portland cement and river sand added with 0.2% (by weight of cement) pristine multi-walled CNTs ultrasonicated but without any surface treatment. Findings: The pH value of ultrasonicated multi-walled CNTs dispersed in de-ionised (DI) water was first determined and found to be 6.85. The pH of control mix without multi-walled CNTs was 12.64 and the pH of test mix with multi-walled CNTs was 12.37. The percentage addition of multi-walled CNTs was very small and hence the reduction in alkalinity was found to be equally small. Flexural strength of test specimens showed 23%, 31.41% and 31.46% increase at 7, 28 and 45 days respectively over control specimens. Compressive strength of test specimens showed 6.1% increase at 28 days over control specimens. Application/Improvements: In view of improvement in flexural strength in mortar, addition of multi-walled CNTs to concrete elements may help in improving their performance under dynamic loading. Further improvements are required to study the effect of an increased percentage addition of multi-walled CNTs without any surface treatment and without any surfactant in cement sand mortar (1:3).

Assessment of gamma radiation exposure of beach sands in highly touristic areas associated with plutonic rocks of the Atticocycladic zone (Greece)

This study aims to evaluate the activity concentrations of 238U, 226Ra, 232Th, 228Th and 40K along beaches close to the plutonic rocks of the Atticocycladic zone that ranged from 15 to 628, 12-2292, 16-10,143, 14-9953 and 191-1192 Bq/kg respectively. A sample from island of Mykonos contained the highest 232Th content measured in sediments of Greece. The heavy magnetic fraction and the heavy non-magnetic fraction as well as the total heavy fraction, were correlated with the concentrations of the measured radionuclides in the bulk samples. The heavy fractions seem to control the activity concentrations of 238U and 232Th of all the samples, showing some local differences in the main 238U and 232Th mineral carrier. Similar correlations have been found between 238U, 232Th content and rare earth elements concentrations. The measured radionuclides in the beach sands were normalized to the respective values measured in the granitic rocks, which at least in most cases are their most probable parental rocks, so as to provide data upon their enrichment or depletion. Since the Greek beaches are among the most popular worldwide the annual effective dose equivalent received due to sand exposure has been estimated and found to vary between 0.002 and 0.379 mSv y−1 for tourists and from 0.018 to 3.164 mSv y−1 for local people working on the beach. The values corresponding to ordinary sand samples are orders of magnitude lower than the limit of 1 mSv y−1, only in the case of heavy minerals-rich sands the dose could reach or exceed the recommended maximum limit.

Experimental Study of Splitting Tensile Strength of Polymer Resin Grout with Fly Ash

Polymer resin grout can be used as bonding material for grouted sleeve connections This paper presents the experimental results on the effectiveness of fly ash as micro filler to the splitting tensile strength of polymer grout. In addition, the cement grout that is usually used as bonding material had been tested for comparison. Eleven proportions, of fly ash as the filler and polymer as binder, were tested with the binder to filler volume ratios of 1:1 and 1:1.5. The test results revealed that fly ash can be used as a micro-filler material to partially replace ordinary river sand in polymer resin grout. The splitting tensile strength of the polymer grout increases with the increase of fly ash contents. However, for higher level of fly ash of more than 22%, the splitting tensile strength deteriorated. For binder: filler ratio of 1:1, the optimum fly ash content of 22% gave the maximum splitting strength of 17.62 MPa, which can be considered acceptable for producing grout with high strength bonding material.

Field behaviour geotextile reinforced sand column

Stone columns (or granular column) have been used to increase the load carrying capacity and accelerating consolidation of soft soil. Recently, the geosynthetic reinforced stone column technique has been developed to improve the load carrying capacity of the stone column. In addition, reinforcement prevents the lateral squeezing of stone in to surrounding soft soil, helps in easy formation of stone column, preserve frictional properties of aggregate and drainage function of the stone column. This paper investigates the improvement of load carrying capacity of isolated ordinary and geotextile reinforced sand column through field load tests. Tests were performed with different reinforcement stiffness, diameter of sand column and reinforcement length. The results of field load test indicated an improved load carrying capacity of geotextile reinforced sand column over ordinary sand column. The increase in load carrying capacity depends upon the sand column diameter, stiffness of reinforcement and reinforcement length. Also, the partial reinforcement length about two to four time's sand column diameter from the top of the column was found to significant effect on the performance of sand column.

Study on the Compressive Strength and Mixing of Ultra-High Performance Concrete

The test in order to obtain liquidity, higher intensity ultra-high performance concrete(UHPC), in the course of preparation, high intensity quartz sand to replace the ordinary sand,reasonable mixture ratio control low water-cement ratio,the incorporation of part of the test piece ofsteel fibers, produced eight specimens . In the ordinary molding and the standard conservation 28d thecase, the ultra-high-performance concrete compressive strength of more than 170MPa.Thepreparation of the test method and test results will provide the basis for further study of the law of themechanical properties of ultra high strength properties of concrete.

Experimental Study on the Pumice Aggregate Concrete

Pumice is a kind of natural lightweight aggregate with well-developed porosity and moderate-intensity. Amorphous Si-Al oxide is its main mineral composition. This paper focused on the performance and features of the pumice pozzolan and aggregate firstly. Then a kind of pumice concretes was prepared with the ordinary Portland cement, ordinary sand and strengthened coarse pumice aggregates. And its mechanical properties, durability, insulation and absorbing performance were investigated. The result showed that the compressive strength of pumice concrete was 20MPa, anti-freezing durability was more than 100 freeze-thaw cycles, electric flux within 6 hours was 1749C, thermal conductivity coefficient was 0.318W/ mK, and the electromagnetic wave absorption was-5dB ranging from 8 to 18GHz. The results indicated that the pumice concrete could be developed as the green and multi-functional concrete materials in the future.

The Effect of Use the Silica Sand on Some Mechanical Properties of Concrete

This research includes study the effects of use the silica sand at different rates and comparison some characteristics with other concrete mixture contains ordinary sand to investigate the effect on some mechanical properties of concrete such as compressive strength, density absorption and flexural strength after (3, 7, 14 and 28) days for four mixtures. , the ordinary sand was replaced by the (Silica Sand) at different rates ( 25%, 50%, 75%, 100%). Sodium Silicate solution at percentage of cement ratio(water tocement ratio is decreased on same ratio) added to the Ideal silica sand mixture to study the effect of addition of some additives on concrete. The study showed that the best results of mixture was when replaced (75%) of the ordinary sand by silica sand , then study some mechanical properties of mixtures such as compressive strength, density absorption and flexural strength after (3, 7, 14 and 28) days .The study showed the optimum percentage of sodium silicate was (1.75%). The study showed that the best result of Density was (2493Kg/m3) after (28) days, and the increment ratio in Density was (2.95%), and the large value in compressive strength was (85.76 MPa) which was (42.9%) after (28) days. The study showed also that the best results of absorption were (0.77) after (28) days, and the decrement ratio in Absorption was (33.8%). The study showed that the best result of flexural strength was (8.02 MPa) after (28) days, and the maximum increment ratio in Flexural Strength was (150.6%) after (28) days.

Utilization of Waterworks Sludge in the Production of Fired/Unfired Water Permeable Bricks

Waterworks sludge was used as raw material to make fired water permeable bricks (WPB) and unfired water permeable bricks (WPB). Results show that when 30% ~ 40% sludge was added with 30% ~ 35% ordinary sands ranging from 1.0 to 1.4mm and some other materials, pressed at 30 MPa and then sintered at 1150°C for 1h, the compressive strength (CS)and permeability coefficient (PC) of produced fired WPB were 36.53MPa and 1.08×10-2 cm/s respectively. When the ratio of waterworks sludge increased from 20% to 35%, the CS of the unfired WPB decreased but stayed above 20 MPa, while the change of PC is insignificant.

Effect of Admixed Recycled Aggregate on Properties of Recycled Concrete

The mixture proportion of recycled concrete was discussed by orthogonal design method. The influence of water-cement ratio, recycled aggregate quantity on workability, cube compressive strength of recycled concrete was analyzed. The experimental results indicated that，Recycled concrete mix proportion design should consider the impact of the water absorption of recycled aggregate. Unit water amount of recycled concrete should be plain concrete unit water consumption and recycled aggregate additional amount of water. Sand ratio should increase in the corresponding ordinary aggregate concrete sand ratio on the basis of 1 to 3 percent. When the water-cement ratio is 0.36 and construction waste content of 40% slag content of 20%, 28d compressive strength of concrete is 48.1MPa, slightly higher than the reference concrete (48.0MPa).

Research and Application of Lost Foam Technology of Goods Train Low-Carbon Alloy Steel Casting

Apply an organic whole technological medium of computer aided three dimensions design 、computer aided solidification process numerical value simulation engineering ＆ computer aided numerical control programming manufacturing, by means of optimization product pattern structure、foundry processing parameters 、die auxiliary equipment and tool、riser gating system ＆ die cavity numerical control cutter location source file , the type of Z8A goods train low-carbon alloy adapter lost foam casting has been under development .Compare lost foam technology to ordinary sand mold casting ,the casting monomer weight lightened 3kg , grade of casting weight precision come to MT7 , grade of casting size precision come to CT8 ,foundry processing yield come to 65% ；Casting defects easily appeared in the course of large quantities production has been analysed ＆ offered solution methods in this article.

Toughness increase of self compacting concrete reinforced with polypropylene short fibers

Increases in bending tests by the addition of low volume fractions of Polypropylene (PP) Short Fibers PP. These toughness increases are similar to those attained by Fiber Reinforced Concrete (FRC) referred elsewhere as Engineered Cementitious Composites (ECC), having some ductility and strain hardening in direct tensile and flexural tests. Concretes mixtures were manufactured using natural pozzolanic blended Portland cement, volcanic crushed coarse aggregates and fine sand from Sahara desert dunes (0-1 mm) from Canary Islands quarries and sand reservoirs, respectively, besides ordinary siliceous sand (0-4 mm) and fly ash from an anthracite-coal heat generator.

Some Key Points on High Strength Grey Iron Cylinder Block Production

Three key points are discussed to manufacture 300Mpa cylinder block castings. The first one is the design of grey iron chemical composition. The chemical composition used for production is as follows: C: 3.20-3.30%, Si: 1.60-1.80%, Mn: 0.70-1.00%, S: <0.10%, P: <0.06%, Cu: 0.70-0.80%, Cr: 0.25-0.35%, Ni: 0.30-0.40%, Sn: 0.06-0.08%. The stream inoculation is adopted. Another key point is to increase the chilling effect of molding material. A kind of ceramic sand is used in the experiment. The ceramic sand is mainly composed of electric fusion bauxite. The material gives much stronger chilling effect. The tensile strength can be 20 MPa higher compared with ordinary silica sand. The third key point is to use the technology of synthetic cast iron. The 300 MPa cylinder block is successfully developed.

Strength Development of Concrete with Proto-Machine-Made Sand

The proto-machine-made sand is a new artificial material for environmental protection with grain size smaller than 5 mm made of water cleaned crushed stones or gravels broken and separated by machines, in which the stone powder maintains as prototype and certain content by improving the production technology. The paper introduces a series of test results of grade C50 concrete mixed by proto-machine-made sand with stone powder in mass content of 3 %, 7 % and 13 %. Based on the cubic compressive strength of concrete at different ages of 3 d, 4 d, 7 d, 14 d, 28 d, 56 d, 90 d, 120 d, 150 d and 180 d, the developing regularities of strength affected by the content of stone powder are analyzed, the formula for predicting the cubic compressive strength of concrete at any ages is proposed. It is proved that the effect of stone-powder in proto-machine-made sand on concrete strength is virtually different from that of the stone powder mixed with powdered mud in ordinary machine-made sand, and the limit value of stone powder content lower than 5 % is not suitable to proto-machine-made sand for mixing concrete with grade of C50.

Column collapse of granular rods

We investigate the collapse of granular rodpiles as a function of particle (length/diameter) and pile (height/radius) aspect ratio. We find that, for all particle aspect ratios below 24, there exists a critical height Hl below which the pile never collapses, maintaining its initial shape as a solid, and a second height Hu above which the pile always collapses. Intermediate heights between Hl and Hu collapse with a probability that increases linearly with increasing height. The linear increase in probability is independent of particle length, width, or aspect ratio. When piles collapse, the runoff scales as a piecewise power law with pile height, with rf ~H(1.2±0.1) for pile heights below H(c) ≈ 0.74 and r(f) ≈ H(0.6±0.1) for taller piles.

An analytical study on the water penetration and diffusion into concrete under water pressure

Because concrete is a type of porous material, water or air can permeate freely into the concrete and that decreases the durability of concrete. Therefore, it is possible to permeate some corrosion inhibitors from the surface of concrete to inside the concrete due to its porosity even the steel-frame location by applying water pressure. The objective of this study is to investigate the depth of the water penetration in concrete forced under pressure. For achieving this purpose, the experiments for the depth of penetration were executed through selecting related factors and levels, such as water pressure and water pressurizing time. The water flow in concrete was examined theoretically and experimentally. As a result, in the case of the low water pressure approximately at 0.15 MPa or less, it was found that the flow showed a Darcy seepage flow and the same flow as an ordinary sand stratum. However, in the case of the high water pressure, the flow was diffused as a seepage flow that is accompanied by an internal deformation of concrete. This study attempts to develop a method that penetrates corrosion inhibitors to the location of steel bars and investigate the penetration depth of corrosion inhibitors by verifying water penetration in concrete under applied pressure.

Numerical Modeling of Flow in a Horizontal Sand Filter

Problem statement: Horizontal sand filters may offer some advantage over vertical sand filters as they could be used for in-line treatment of wastewaters. Horizontal pipelines of tens and if not hundreds of meters length, filled with ordinary sand or permeable reactive media such as activated carbon or natural zeolite or iron filings, may be used to remove impurities from mine drainage waters, sewer and storm waters. Approach: However, in reality, in industrial-scale applications, the sand filled horizontal structures are almost always avoided due to the fact that water seeks out the path of least resistance. Once such a path is created, the vast majority of the water channels towards the least resistance zone and very small percentage of the water will go through the sand. Results: This study, applying numerical modeling using FLUENT software, which is based on the integral control volume approach, explores a number of geometries to identify a design that helps the inlet water to sweep the entire sand with the least channeling. The Navier Stokes equations for laminar and incompressible flow through porous media (i.e., the sand) including the viscous resistance were solved. Retention time of a fluid with properties similar to water, called tracer, were also estimated using Eulerian unsteady two phase flow analysis. Conclusion: The results of the models showed that the geometries involving a pipe with spiral protrusions or plate (baffles) inside, would be partially successful in drawing the water away from the channeling zone and moving it through the sand, however the geometry with the spiral protrusions uses much less power than the one with the baffles.