This chapter describes the methodology used in EPA’s Waste Reduction Model (WARM) to estimate streamlined life-cycle greenhouse gas (GHG) emission factors for concrete beginning at the point of waste generation. The WARM GHG emission factors are used to compare the net emissions associated with concrete in the following two waste management alternatives: recycling and landfilling. Exhibit 1 shows the general outline of materials management pathways for concrete in WARM. For background information on the general purpose and function of WARM emission factors, see the Introduction & Overview chapter. For more information on Recycling and Landfilling, see the chapters devoted to these processes. WARM also allows users to calculate results in terms of energy, rather than GHGs. The energy results are calculated using the same methodology described here but with slight adjustments, as explained in the Energy Impacts chapter.

나의 Concrete 연구실

Use of geopolymer concrete for a cleaner and sustainable environment – A review of mechanical properties and microstructure

Geopolymer, green alkali activated cementitious material: Synthesis, applications and challenges

Despite the extensive use of self-compacting concrete in constructions over the last decades, there is not yet a robust quantitative method, available in the literature, which can reliably predict its strength based on its mix components. Τhis limitation is due to the highly nonlinear relation between the self-compacting concrete’s compressive strength and the mixed components. In this paper, the application of artificial neural networks for predicting the mechanical characteristics of self-compacting concrete has been investigated. Specifically, surrogate models (such as artificial neural network models and a new proposed normalization method) have been used for predicting the 28-day compressive strength of admixture-based self-compacting concrete (based on experimental data available in the literature). The comparison of the derived results with the experimental findings demonstrates the ability of artificial neural networks to approximate the compressive strength of self-compacting concrete in a reliable and robust manner. Furthermore, the proposed formula for the normalization of data has been proven effective and robust compared to available ones.

Self-compacting concrete strength prediction using surrogate models

Despite the widespread use of self-compacting concrete (SCC) in construction in the last decades, there is not yet a robust quantitative method, available in the literature, which can reliably predict their strength based on the mix components. This is mainly due to the highly non-linear behaviour exhibited by the compressive strength in relation to the components of the concrete mixtures. In the present paper, the application of artificial neural networks (ANNs) to predict the mechanical characteristics of SCC has been investigated. Specifically, ANN models for the prediction of the 28-days compressive strength of admixture-based self-compacting concrete (based on experimental data available in the literature) are presented. The comparison of the derived results with experimental findings demonstrates the promising potential of using back propagation neural networks for the reliable and robust approximation of the compressive strength of self-compacting concrete.

Prediction of self-compacting concrete strength using artificial neural networks

This paper presents a review of the properties of fresh concrete including workability, heat of hydration, setting time, bleeding, and reactivity by using mineral admixtures fly ash (FA), silica fume (SF), ground granulated blast furnace slag (GGBS), metakaolin (MK), and rice husk ash (RHA). Comparison of normal and high-strength concrete in which cement has been partially supplemented by mineral admixture has been considered. It has been concluded that mineral admixtures may be categorized into two groups: chemically active mineral admixtures and microfiller mineral admixtures. Chemically active mineral admixtures decrease workability and setting time of concrete but increase the heat of hydration and reactivity. On the other hand, microfiller mineral admixtures increase workability and setting time of concrete but decrease the heat of hydration and reactivity. In general, small particle size and higher specific surface area of mineral admixture are favourable to produce highly dense and impermeable concrete; however, they cause low workability and demand more water which may be offset by adding effective superplasticizer.

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Effects of Different Mineral Admixtures on the Properties of Fresh Concrete

Several review papers exist in literature related to the concrete containing mineral admixtures; however, this paper reviews the durability characteristics of the concrete containing fly ash (FA), silica fume (SF), ground granulated blast furnace slag (GGBS), metakaolin (MK) and rice husk ash (RHA). Durability related properties reviewed include permeability, resistance to sulfate attack, alkali-silica reaction (ASR), carbonation, chloride ion penetration, freezing and thawing, abrasion, fire, acid, and efflorescence. From review of existing literature, it is found that permeability of concrete depends upon the content of alumina in mineral admixtures, i.e. higher the alumina content, lesser the permeability which results higher resistance to sulfate and chloride ion penetration. Highly reactive mineral admixtures prevent more ASR and reduce efflorescence. The carbonation increases with the mineral admixtures because higher water binder ratio and lesser content of portlandite in concrete due to pozzolanic reaction. Mineral admixtures require air entrainment except MK and RHA for better resistance to freezing and thawing. Keywords—Alkali silica reaction, carbonation, durability, mineral admixture, permeability.

/pdf/durability-of-concrete-with-different-mineral-admixtures-a-2gh6z6s088.pdf

Durability of Concrete with Different Mineral Admixtures: A Review

Fly ash, silica fume and rice husks are hazardous waste materials that have no use and in the past have been landfilled. However, landfilling is becoming expensive and causes contamination to soil ...

Utilisation of waste material in geopolymeric concrete

The mechanical properties of high-strength ductile concrete (HSDC) have been investigated using Metakaolin (MK) as the cement replacing material and PVA fibers. Total twenty-seven (27) mixes of concrete have been examined with varying content of MK and PVA fibers. It has been found that the coarser type PVA fibers provide strengths competitive to control or higher than control. Concrete with coarser type PVA fibers has also refined microstructure, but the microstructure has been undergone with the increase in aspect ratio of fibers. The microstructure of concrete with MK has also more refined and packing of material is much better with MK. PVA fibers not only give higher stiffness but also showed the deflection hardening response. Toughness Index of HSDC reflects the improvement in flexural toughness over the plain concrete and the maximum toughness indices have been observed with 10% MK and 2% volume fraction of PVA fibers.

/pdf/strength-development-of-high-strength-ductile-concrete-1ox3got1eo.pdf

Strength Development of High-Strength Ductile Concrete Incorporating Metakaolin and PVA Fibers

This paper presents the study on the effect of fly ash (FA), silica fume (SF) and microwave incinerated rice husk ash (MIRHA) as cement replacement material (CRM) on the mechanical and fresh properties of self-compacting Concrete (SCC). Some of the CRM materials are supposed to enhance the properties of SCC by avoiding the Bleeding at fresh stage and increase the strength in the long term at hardened stage, in addition of that CRM can reduce the total cost of mixing depends on the replacement percentage. The experimental work included the workability test as well as mechanical test of SCC. Workability test determined the flowability, filling ability and segregation resistance by slump flow, slump T50, Lbox and V-funnel testes. The mechanical properties by applying compressive strength, splitting tensile strength and flexural strength were investigated. There were a total of nine mixes created with different CRM contents. The result showed that the MIRHA needed more water as compared to SF to achieve the similar fresh properties, similarly concrete with 5% SF showed about 9.70% higher compressive strength after 90 days, 5.10 MPa high tensile strength and 10.12 MPa flexural strength when compared with other mixes.

M.F. Nuruddin

Papers

Effects of Different Mineral Admixtures on the Properties of Fresh Concrete

Durability of Concrete with Different Mineral Admixtures: A Review

Utilisation of waste material in geopolymeric concrete

Strength Development of High-Strength Ductile Concrete Incorporating Metakaolin and PVA Fibers

Study the effectiveness of the different pozzolanic material on self-compacting concrete