scholarly journals Full-scale test of precast prestressed concrete double-tee girder for rural bridges

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Dinh Hung Nguyen ◽  
Hong Nghiep Vu ◽  
Thac Quang Nguyen
Keyword(s):  
Fly Ash ◽  
Prestressed Concrete ◽  
Rural Areas ◽  
Full Scale ◽  
Concrete Aggregate ◽  
Span Length ◽  
Natural Sand ◽  
Linear Elastic ◽  
Bridge Structures ◽  
Concrete Blocks

AbstractIncreasing the number of small and medium-sized bridges is a need to improve accessibility in rural areas of the Mekong River Delta of Vietnam. Many types of bridge structures can be the suitable selection for rural bridges, on which the overall load of the operating truck is about 100kN. An objective of this paper is to propose a double-tee (DT) girder with the span length varying from 12 m to 15 m for the rural bridge types B and C in the Vietnamese standard. New concrete aggregate using crushed sand and fly ash for the DT girders is also examined to solve the scarcity of natural sand and environmental problem from industrial waste. A full-scale DT girder with a span length of 12 m is tested to confirm the capacity of the proposed design. Result finds out that the concrete sand, which the natural sand is replaced by 90% of the crushed sand and 10% of the fly ash by weight, could be well applied for the proposed DT girders. Another finding is a linear elastic uncracked response of the tested DT girder under loads of a rural vehicle and concrete blocks of 306kN. Therefore, the proposed DT girders are suggested to the rural bridges.

scholarly journals Experimental Study on Water Percolating Concrete

2021 ◽  
Vol 10 (4) ◽  
pp. 169-170
Author(s):  
Ayapilla Narasimha Murthy
Keyword(s):  
Fly Ash ◽  
Rural Areas ◽  
Water Conservation ◽  
Pervious Concrete ◽  
Partial Replacement ◽  
Published Data ◽  
Porous Concrete ◽  
Coarse Aggregates ◽  
Run Off ◽  
Concrete Blocks

This paper addresses two aspects namely a new method for manufacturing of percolating concrete blocks using different proportions of concrete mixture such as Portland cement, Coarse aggregates, fine aggregates, limestone, and water have been designed. Apart from this an attempt has also been made by adding small quantities of additives such as fly ash, rice husk ash etc. for its strength and suitability on par with the normal Concrete blocks. Another is a partial replacement of cement with supplementary cementation materials such as fly ash and metakaolin in different proportions for reducing high grade cement consumptions been proposed. The design of a Pervious Concrete is made in such a way that it allows the entire surface run off water to percolate down without retaining any drop/quantity in it. Thus, it is named as water percolating Pervious Concrete/ porous concrete. An alternative for reducing cement usage in concrete makes concrete eco-friendly. Thus, there comes an idea of partially replacing cement with supplementary cementations materials, The concern has been growing in recent years towards reducing the pollutants in water conservation and the environment. The continual urbanization has led to the increase in impervious surface area of the cities, further leading to blockage in percolation of precipitation from rainfall. This result is excess surface run off. To counteract this, pervious concrete is the solution. Hence, the pervious concrete having 15% to 35% interconnected pores by volume, allows direct infiltration of water through its structure. Since the strength of this block for highway suitability of roads is not yet tested. The main aim of this paper is to improve the strength characteristics of porous concrete. However, on comparison, with the published data it is suitable for foot paths/ pathways and parking lots and as driveways in the residential and small rural areas where less vehicular traffic. This will help in reducing the risk of water clogging and recharges the nearby ground water level. The Maintenance of the slab is also minimum and can be repaired and cleaned easily. Thus, it is worthy and useful in many ways

Preliminary Study of Pressed Lightweight Geopolymer Block Using Fly Ash, Portland Cement and Recycled Lightweight Concrete

2016 ◽  
Vol 718 ◽  
pp. 184-190
Author(s):  
Patcharapol Posi ◽  
Piyawat Foytong ◽  
Pearploy Thongjapo ◽  
Natakorn Thamultree ◽  
Phongsathon Boontee ◽  
...  
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Lightweight Concrete ◽  
Concrete Block ◽  
Concrete Aggregate ◽  
Fine Aggregate ◽  
Geopolymer Concrete ◽  
Lignite Fly Ash ◽  
Concrete Blocks ◽  
Preliminary Study

In this research, the properties of pressed lightweight fly ash geopolymer concrete block containing Portland cement and recycled lightweight concrete aggregate. The recycled lightweight concrete aggregate (RLCA) was crushed and classified as coarse aggregate (CA), medium aggregate (MA) and fine aggregate (FA). The RLCA with CA : MA : FA of 30 : 30 : 40 by weight was used to reduce the weight of concrete block. Lightweight geopolymer concrete block was produced from lignite fly ash, NaOH, Na2SiO3, RCLA and PC. The lightweight geopolymer concrete blocks with 28-day compressive strengths between 2.0 and 14.1 MPa and densities between 1130 and 1370 kg/m3 were obtained.

scholarly journals Use of Prefabrication, Construction and Demolition Wastes as an Aggregate in Vibropressed Precast Concrete Blocks Production

2022 ◽  
Vol 11 (1) ◽  
pp. 20-28
Author(s):  
Grzegorz Łój ◽  
Wiesława Nocuń-Wczelik
Keyword(s):  
Precast Concrete ◽  
Recycled Concrete ◽  
Recycled Aggregate ◽  
Partial Substitution ◽  
Concrete Aggregate ◽  
Recycled Concrete Aggregate ◽  
Concrete Technology ◽  
Natural Sand ◽  
Natural Aggregate ◽  
Concrete Blocks

The aim of current study was to determine the recycled concrete aggregate (RCA) applicability in the production of concrete mixture for vibropressed concrete blocks. The experiments were focused especially on the crushed waste material from the same concrete elements producing plant.  For this type of precast elements only some finer fractions can be implemented and the “earth-moist” consistency of fresh mixture is required. The series of samples was prepared in which the mixture of natural aggregates was partially or totally substituted by recycled concrete aggregate. The 0/4 RCA fraction, which is usually rejected in ready mix concrete technology, plays a role of 0/2 sand.  The substitution of sand fraction was from 20% to 100% respectively. The substitution of the coarser aggregate fractions by 4/16 RCA was also done. The standard properties of vibropressed elements, such as the degree of densification, the density of material, the compressive and splitting tensile strength and the water absorption capacity according to the relevant standards were determined. The parameters of materials with the natural aggregate substitution by RCA are affected by the ratio of recycled concrete aggregate. In most cases the results do not decline specially from those for reference samples, when only the natural sand (0/2) fraction is substituted by the 0/4 recycled aggregate. As one could expect, as lower the substitution, as better the test results. The partial substitution of natural aggregate by coarser fractions requires experimental verification; over 20% substitution of natural aggregate by 4/8, 8/16 or 0/16 RCA should be excluded.

scholarly journals Reactivity of Ground Coal Bottom Ash to Be Used in Portland Cement

J ◽  
2021 ◽  
Vol 4 (3) ◽  
pp. 223-232
Author(s):  
Esperanza Menéndez ◽  
Cristina Argiz ◽  
Miguel Ángel Sanjuán
Keyword(s):  
Fly Ash ◽  
Coal Fly Ash ◽  
Bottom Ash ◽  
Blended Cement ◽  
Coal Ash ◽  
Pozzolanic Reaction ◽  
Natural Sand ◽  
Coal Bottom Ash ◽  
Novel Material ◽  
Pozzolanic Properties

Ground coal bottom ash is considered a novel material when used in common cement production as a blended cement. This new application must be evaluated by means of the study of its pozzolanic properties. Coal bottom ash, in some countries, is being used as a replacement for natural sand, but in some others, it is disposed of in a landfill, leading thus to environmental problems. The pozzolanic properties of ground coal bottom ash and coal fly ash cements were investigated in order to assess their pozzolanic performance. Proportions of coal fly ash and ground coal bottom ash in the mixes were 100:0, 90:10, 80:20, 50:50, 0:100. Next, multicomponent cements were formulated using 10%, 25% or 35% of ashes. In general, the pozzolanic performance of the ground coal bottom ash is quite similar to that of the coal fly ash. As expected, the pozzolanic reaction of both of them proceeds slowly at early ages, but the reaction rate increases over time. Ground coal bottom ash is a promising novel material with pozzolanic properties which are comparable to that of coal fly ashes. Then, coal bottom ash subjected to an adequate mechanical grinding is suitable to be used to produce common coal-ash cements.

scholarly journals Optimal Surface Aeration Control in Full-Scale Oxidation Ditches through Energy Consumption Analysis

Water ◽  
2018 ◽  
Vol 10 (7) ◽  
pp. 945 ◽  
Author(s):  
Yong Qiu ◽  
Chi Zhang ◽  
Bing Li ◽  
Ji Li ◽  
Xiaoyuan Zhang ◽  
...  
Keyword(s):  
Control System ◽  
Energy Consumption ◽  
Rural Areas ◽  
Energy Model ◽  
Full Scale ◽  
Economic Feasibility ◽  
Model Parameters ◽  
Online Data ◽  
Improve Energy Efficiency ◽  
Aeration Control

Oxidation ditches are popularly used in rural areas and decentralized treatment facilities where energy deficiency is of concern. Aeration control technologies are well established for diffusion systems in order to improve energy efficiency, but there are still challenges in their application in oxidation ditches because surface aerators have unique characteristics with respect to oxygen transfer and energy consumption. In this paper, an integral energy model was proposed to include the energy, aeration, and fluidic effects of surface aerators, by which the energy for aeration of each aerator can be estimated using online data. Two types of rotating disks with different diameters (1800 mm and 1400 mm) were monitored in situ to estimate the model parameters. Furthermore, a feedforward–feedback loop control strategy was proposed using the concept of energy analysis and optimization. The simplified control system was implemented in a full-scale Orbal oxidation ditch, achieving an approximately 10% saving in full-process energy consumption. The cost–benefit analysis and carbon emission assessment confirmed the economic feasibility and environmental contribution of the control system. The energy model can help process designers and operators to better understand and optimally control the aeration process in oxidation ditches.

Recycling of Waste Concrete and Fly Ash for Recycled Aggregate Concrete: Fundamental Characteristics Evaluation

2009 ◽  
Vol 620-622 ◽  
pp. 255-258 ◽  
Author(s):  
Cheol Woo Park
Keyword(s):  
Fly Ash ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Experimental Program ◽  
Concrete Aggregate ◽  
Fine Aggregate ◽  
Recycled Concrete Aggregate ◽  
Aggregate Concrete ◽  
Waste Concrete

As the amount of waste concrete has been increased and recycling technique advances, this study investigates the applicability of recycled concrete aggregate for concrete structures. In addition fly ash, the industrial by-product, was considered in the concrete mix. Experimental program performed compressive strength and chloride penetration resistance tests with various replacement levels of fine recycled concrete aggregate and fly ash. In most case, the design strength, 40MPa, was obtained. It was known that the replacement of the fine aggregate with fine RCA may have greater influence on the strength development rather than the addition of fly ash. It is recommended that when complete coarse aggregate is replaced with RCA the fine RCA replacement should be less than 60%. The recycled aggregate concrete can achieve sufficient resistance to the chloride ion penetration and the resistance can be more effectively controlled by adding fly ash. It I finally conclude that the recycled concrete aggregate can be successfully used in the construction field and the recycling rate of waste concrete and flay ash should be increased without causing significant engineering problems.

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