River Aggregate Research Articles

Use of perlite powder to suppress the alkali–silica reaction

Reported below are the results from a study aimed at mitigating the deleterious alkali–silica reaction by using perlite powder as an admixture. The expansion of mortar bars containing various amounts of silica fume (SF), expanded perlite, and natural perlite was studied. Two kinds of reactive aggregates were used in the study: highly reactive river aggregate containing opal and marginally reactive monzo-diorite aggregate. Expanded perlite and silica fume were tested with both aggregate, separately; on the other hand, natural perlite was tested only with monzo-diorite aggregate. The bars were cast in accordance with ASTM C1260, accelerated mortar bar method, and were stored in NaOH solution for 30 days. Length changes were measured and reported. The results showed that both expanded and natural perlite powder (NPP) have potential to suppress the deleterious alkali–silica expansion.

Impact analysis of river aggregate mining on river environment

Impact of river gravel mining on river environment is analyzed in this research. Water-quality and ecological conditions of the study area that is being dredged were compared with those of the reference site that is located on the upper stream of that study area. Long-term variations of the riverbed in the study area were simulated and predicted after gravel mining. The study area is a part of the Youngsan River, which is located in the south-west of the Korean Peninsula. Water quality conditions are not influenced by the mining except for a slight increase in suspended solids. Ecological conditions on fishes, mammalia, amphibia, reptilia and birds are influenced in a measure by river aggregate mining. Results of the study of numerical simulation on bottom topography do not show a build-up of sediment and show stabilization after mining. These study results can be used for environmental impact study.

고로슬래그미분말을 혼입한 고유동콘크리트에서 골재조합이 콘크리트 유동성상에 미치는 영향에 관한 실험 연구

The purpose of study is to offer base data for high fluid concrete mix property, as grasp effect of aggregate to reach much more effect for producing high fluid concrete. For this study, there are three types of combined aggregates, river sand + river aggregate(type A), river sand + crusted aggregate(type B), washed sea sand + crushed aggregate(type C) and take a factor, water-contents, water-binder ratio and S/a. And so, we had following conclusion, resulting application-ability of high fluid mortar by K-slump tester to use a handy consistency measuring instrument. And so, we had following conclusion, resulting application-ability of high fluid concrete by K-slump tester to use a handy consistency measuring instrument. 1) In cafe of regular water binder ratio, high fluid concrete suffered much effect of combined aggregates and water binder ratio. Range of water binder ratio by combined aggregates is w/b 0.4 downward(type A and B), w/b 0.35 downward(type C). 2) Water contents to need for producing high fluid concrete is minimum 170kg/ without regard to combined aggregates. 3) The effect of S/a on high fluid concrete by combined aggregates is approximately S/a 50% (type A and B), s/a 50-55% (type C). 4) Consistency measuring of high fluid concrete by K-slump tester is possible and first indication value, high fluid concrete can be produced, is 6~10.5cm.

Characteristics, Dynamics and Importance of Aggregates in Rivers - An Invited Review

The current knowledge of micro- and macroaggregates in running waters as well as an assessment of their importance will be given in this overview. Micro- and macroscopic aggregates are an abundant component of running waters, considering both rivers and estuaries. They are composed of different kinds of organic and inorganic matter and elements, mainly from the aquatic but also from the terrestrial environment. Their production is determined by natural and anthropogenically influenced abiotic and biotic factors. Aggregate abundance, size and composition vary greatly along the longitudinal profile of running waters. Aggregates are actively or passively colonized by bacteria, protozoa (amoebae, ciliates and flagellates) and metazoa (copepods, nematodes, rotifers, veliger larvae) and they show higher loads of nutrients and organisms compared to the surrounding water. Detritus in running waters has been examined over a period of 100 years but investigations of single aggregates began only in 1996, after pioneering works in the marine field and in lakes. Since then studies have been focused on several aspects of aggregate formation, colonization, nutrient recycling and decomposition. Aggregates have been identified as foci of microbial activity. It has been shown that the significance of aggregate – associated organisms and processes varies both temporally and spatially and is also affected by the nutrient status of surrounding water. An important conclusion from recent studies is that the resuspension and sedimentation of aggregates connects pelagic and benthic food webs to an aquatic food web. It also underlines the importance of the microbial food web, with its fluxes among aggregate-associated pico- and nano-organisms, to organisms of higher trophic levels. Predators of higher trophic levels are only able to eat small-sized organisms if they are associated to aggregates.

PRELIMINARY FINDINGS OF OIL-SOLIDS INTERACTION IN EIGHT ALASKAN RIVERS

ABSTRACT The formation of oil-mineral aggregates in rivers with high concentrations of suspended solids could be an important mechanism for transferring oil from a surface slick into the water column. Seven glacier-fed rivers in south-central Alaska were sampled three times in the summer of 1999 and tested to see how suspended solids in the water would interact with crude oil. Oil-mineral aggregates formed with all samples, which lead to the conclusion that similar oil-solids interaction should occur if oil is spilled into other glacier-fed rivers. The amount of oil associated with the solids after mixing was roughly proportional to the concentration of suspended solids in the samples. The oil-loading results ranged between 0.01 and 0.45 g oil/g solid, with most of the measurements falling between 0.03 and 0.24 g oil/g solid. The average loading for all tests was 0.13 g oil/g solid, which is consistent with the findings of a similar study done in 1998 on the Yukon River. This result indicates that the suspended solids in the streams studied—especially the larger Yukon, Copper, and Lowe Rivers—have a large oil-holding capacity and would be capable of scavenging a considerable volume of oil. The exact quantity would depend on several factors, including the volume and dimensions of the slick, concentration of suspended solids, and current velocity of the river. Historical data on stream flow, suspended-solids concentration, and particle-size distribution were gathered and used in conjunction with the laboratory oil-solids interaction results to identify the times of the year when such interaction could occur to a significant degree. This data indicated that oil-mineral aggregates are expected to form in all rivers tested, with the most significant periods being during the summer months.

Track and support rehabilitation for a mine company railroad

The initial support and tie foundation problems of a railroad track built in 1974 to carry axle loads 21% greater than presently (1998) permitted under interchange laws at a speed of 88 km/h are presented. Some of the concerns related to and affecting the final rehabilitation that resulted in a final satisfactory performance are documented. The foundation engineer's interest is directed to the ballast, the tie, and to a lesser extent the rail's behaviour. Cobble-sized (75-150 mm) river gravel was used as the source for the ballast in the rehabilitation. The ballast's satisfactory performance has permitted the establishment of guidelines for future use of this type source of material where suitable quarried rock is not available. The railroad's satisfactory performance after rehabilitation has proven that the design concepts involving 36 t (40 tons) axle loads operating on 60 kg/m (119 lb/yd) continuously welded rail, concrete ties, and ballast manufactured by crushing from a river aggregate were achievable.Key words: railway track, concrete ties, ballast aggregate, aggregate, crushed face, rail, 36 t (40 tons) axle loads.

Determination of Apropriate Concrete Mixtures in Concrete Lined Irrigation Canals Used in the Gap Region

This research was aimed at determining appropliate concrete ratios in concrete lined irrigation channels used under the climatic conditions of Sanliurfa region. Firat river's aggregates, brought from Samsat (Adiyaman) region, were used in preparation of concrete. According to the results obtained, it was found that aggregates used was suitable for concrete production. Different ratios of cement used in the mixture, were prepared through mixing with aggregates with fly ash and chemical admixture called Sika-AER. Amounts of cements in the mixture were decreased in ratios of 0, 10, 15, 20 and 25% by weight and was replaced instead with, fly ash from Afsin-Elbistan Thermal Power Station. The best concrete mixture was found with 15% fly ash. Basic characteristics of this concrete were found as following: compressive strength of 232 kgf/cm2, water absorption of 3.75%, specific weight of 2.41 kg/dm3, relative dynamic elasticity module of 77.13 %, ratios of pore 8.75 %. Sika-AER was added in ratios of 0.05, 0.10 and 0.15% of cement in weight. The most suitable cement was obtained with Sika-AER of 0.05 %. And the resulting, concrete mixture had a compressive strengt of 186 kgf/cm2, water absorption of 3.43 %, specific weight of 2.32 kg/dm3, relative dynamic elasticity module of 106.28 %, ratios of pore 8.00 %. At the result fly ash and Sika-AER added were bettened the concrete quality and those type of adding can be used in the GAP region successfully.

In situ observation of suspended solid aggregates in rivers

In situ observation of suspended solid aggregates in rivers

Stereological Estimation of Fractal Number of Fracture Planes in Concrete

ABSTRACTConcrete is a man-made material containing a particulate filler designed on the basis of a sieve curve. In case of river aggregate, the particles are approximately spherical and smoothtextured. The particle-matrix interface is mostly the weakest chain link in the mechanical system. This implies damage evolution to start at particle-matrix interfaces. In case of direct tension, these interface cracks will be on average perpendicular to the loading direction. In case of direct compression, they will be parallel to the loading direction. A single fracture surface is formed in tension and a series of fracture surfaces in compression. They are the result of crack concentration within a process zone, in which the engineering crack closely meanders around a dividing plane. This allows to model these fracture surfaces on different resolution levels. It is shown, using stereological notions, that the very phenomenon is of a non-ideal fractal nature. Estimates for fractal dimension of fracture surfaces in concretes based on sieve curves at the border of the practical range are found to closely match experimental data reported in the literature.

Bedload transport of mud as pedogenic aggregates in modern and ancient rivers

Bedload transport of mud as pedogenic aggregates in modern and ancient rivers

Bedload transport of mud as pedogenic aggregates in modern and ancient rivers

ABSTRACTAbundant sand‐sized mud aggregates in the Cooper and Diamantina Rivers, Lake Eyre Basin, Australia are attributed to bedload transport of aggregates formed in deeply‐cracked floodplain soils. The conditions required for formation of pedogenic mud aggregates are: (i) abundant clay containing at least minor swelling clay, and (ii) a climate with at least seasonally hot dry periods. The worldwide distribution of these soils (Vertisols) suggests that a significant amount of mud is transported as pedogenic aggregates by modern rivers.Ancient analogues in which mud aggregates and Vertisol profiles have been recognized are the Jurassic East Berlin Formation (Connecticut, USA) and the Carboniferous Maringouin Formation (New Brunswick and Nova Scotia, Canada). The dominant red mudstones of these formations are interpreted as mainly bedload sediments deposited by sheet floods in semi‐arid palaeoclimates. The Triassic Hawkesbury Sandstone (NSW, Australia) also contains sand‐sized mudstone aggregates, thought to be pedogenic, but its paleosol and other facies point to formation in a wetter palaeoclimate. The indications are that bedload transport of mud as pedogenic aggregates was as significant a process in ancient rivers as it is at present.

Effect of oil soaking on the dynamic modulus of concrete

This paper describes a study to assess the degree of deterioration and/or changes in concrete due to direct contact with crude oil. Dynamic modulus of elasticity of concrete prisms 100 × 100 × 500 mm , has been measured at different ages for a period of 3 years; ordinary portland cement, natural river aggregates, four water/cement ratios and four curing regimes were considered. Specimens were soaked in crude oil, whilst similar specimens were continuously kept in water and others in a controlled environment of constant temperature 16 ± 0.5 ° C and relative humidity of 60 ± 2%. The dynamic modulus of concrete increased by 8–10% due to oil soaking, while water saturated specimens showed an increase of 10–15%.

Concrete with fly-ash and blast furnace cement showing high resistance towards chemical agents

This paper deals with investigations into concrete prepared with common river aggregate and a binder containing 70% fly-ash and 307 blast furnace cement, and discusses the results obtained. The fly-ash used in the concrete mixtures results from the combustion of brown coal and pit coal. It contains SiO 2 + Al 2 3 + Fe 2 3 > 70%, and shows a chemical activity of 30–50 mg CaO fixed by 1 g of fly-ash. It yields a paste of normal consistency with 22–26% of water. The blast furnace cement contains a grinding admixture of 40–50% granulated blast furnace slag, and shows compressive strengths of not less than 250 daN/cm 2 at 28 days. Concrete thus prepared shows compressive strengths ranging from 600–1900 N/cm 2 at 28 days, and from 1000–2500 N/cm 2 at 90 days old. It is highly resistant towards sulfate and seawater and has a satisfactory behavior towards acid attack.

Shrinkage of oil-soaked concrete

Synopsis This paper describes an investigation into the shrinkage of concrete in direct contact with crude oil. The shrinkage or volume change was studied by using 100 × 100 × 500 mm concrete prisms. Ordinary Portland cement, natural river aggregates, four water/cement ratios, and four curing regimes were used. Similar specimens were cast and continuously kept in water and in a constant temperature and humidity room for comparative purposes.

High strength and water impermeability of concrete as a function of surface area of aggregate

The author has developed a new approach for analyzing the relationship between aggregate gradation and strength of concrete. The method is applied to a number of different types of aggregate. This relationship is a surface area factor. The total surface area of all particles in one pound is defined as the “surface area factor”. Since this is a quantitative alternate for the fineness modulus the formulas include only the quantity of aggregate retained on the No. 100 sieve. Simple formulas are presented for the determination of the surface area of one pound of aggregate. These formulas are useful for any kind of structural concrete using river aggregate, crushed rock or lightweight aggregate. Preliminary experimental results are presented which support the formulas. Numerical examples illustrate the use of the formulas.