scholarly journals Estimating CO2 Emission Savings from Ultrahigh Performance Concrete: A System Dynamics Approach

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 995
Author(s):  
Mubashar Sheheryar ◽  
Rashid Rehan ◽  
Moncef L. Nehdi
Keyword(s):  
System Dynamics ◽  
Co2 Emissions ◽  
New Technologies ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Civil Infrastructure ◽  
Portland Cement Concrete ◽  
Flexible Framework ◽  
Cement And Concrete

Ordinary Portland cement concrete (OPC) is the world’s most consumed commodity after water. However, the production of cement is a major contributor to global anthropogenic CO2 emissions. In recent years, ultrahigh performance concrete (UHPC) has emerged as a strong contender to replace OPC in diverse applications. UHPC has much higher mechanical strength, and thus less material is used in a structural member to resist the same load. Moreover, it has a much longer service life, reducing the long-term need for repair and replacement of aging civil infrastructure. Thus, UHPC can enhance the sustainability of cement and concrete. However, there is currently no robust tool to estimate the sustainability benefits of UHPC. This task is challenging considering that such benefits can only be captured over the long-term since variables, such as population growth and cement demand per capita, become more uncertain. In addition, the problem of CO2 emissions from cement and concrete is a complex system affected by time-dependent feedback. The System Dynamics (SD) method has specifically been developed for modeling such complex systems. Accordingly, a SD model was developed in this study to test various pertinent policy scenarios. It is shown that UHPC can reduce cumulative CO2 emissions of cement and concrete—over the studied simulation period—by more than 17%. If supplementary cementitious materials are further deployed in UHPC and new technologies permit reducing the carbon footprint per unit mass of cement, emission savings can become more substantial. The model offers a flexible framework where the user controls various inputs and can extend the model to account for new data, without the need for reconstruction of the entire model.

Evaluation of strength of concrete on different initial exposure condition

2020 ◽  
Vol 13 ◽  
Author(s):  
Sri Ram Krishna Mishra ◽  
Pradeep Kumar Ghosh ◽  
Manoj Kulshreshtha
Keyword(s):  
Portland Cement ◽  
High Strength ◽  
Cementitious Materials ◽  
General Purpose ◽  
Supplementary Cementitious Materials ◽  
Exposure Condition ◽  
Portland Cement Concrete ◽  
Initial Exposure ◽  
Skilled Manpower ◽  
Standard Practices

Background: The previous studies have focused curing effect of mainly on high strength concrete, where strict supervision is maintained. This study is based upon general purpose concreting work for commercial and residential construction in absence of skilled manpower and supervision. Objective: The objective of this study is to establish a thumb rule to provide 7 days initial curing for maintaining quality for unsupervised concreting irrelevant to type of cement and grading. Methods: In this study concrete samples made with locally available commercial cements were cured for various initial exposure. Results: The results shows that concrete cured after a gap of 4 days from the time of de-moulding have given lowest strength as compared to concrete cured in standard practices i.e. where proper curing protocol had been followed. Conclusion: Initial curing is most important aspect of gaining desired strength. The findings after this study shows that curing affects the strength of concrete in variable grading. Initial curing has great importance for concrete with all types of Portland cement. Concrete with supplementary cementitious materials gives lowest strength initially but results higher strength after 28 days as compared to Portland cement.

scholarly journals Long-term mechanical and shrinkage properties of cementitious grouts for structural repair

2019 ◽  
Vol 4 ◽  
pp. 9-15
Author(s):  
Md Shamsuddoha ◽  
Götz Hüsken ◽  
Wolfram Schmidt ◽  
Hans-Carsten Kühne ◽  
Matthias Baeßler
Keyword(s):  
Fly Ash ◽  
Flexural Strength ◽  
Cementitious Materials ◽  
Response Surfaces ◽  
Supplementary Cementitious Materials ◽  
Strength Development ◽  
Structural Repair ◽  
Positive Effects ◽  
Micro Silica

Grouts have numerous applications in construction industry such as joint sealing, structural repair, and connections in precast elements. They are particularly favoured in rehabilitation of structures due to penetrability and convenience of application. Grouts for repair applications typically require high-performance properties such as rapid strength development and superior shrinkage characteristics. Sometimes industrial by-products referred as supplementary cementitious materials (SCM) are used with neat cement due to their capabilities to provide binding properties at delayed stage. Micro silica, fly ash and metakaolin are such SCMs, those can modify and improve properties of cement products. This study aims at investigating long-term mass loss and linear shrinkage along with long-term compressive and flexural strength for grouts produced from ultrafine cement and SCMs. A series of mixtures were formulated to observe the effect of SCMs on these grout properties. Properties were determined after 365 days of curing at 23oC and 55% relative humidity. The effect of SCMs on the properties are characterised by statistical models. Response surfaces were constructed to quantify these properties in relation to SCMs replacement. The results suggested that shrinkage was reduced by metakaolin, while micro silica and fly ash had positive effects on compressive and flexural strength, respectively.

scholarly journals Utilization of tailings in cement and concrete: A review

2019 ◽  
Vol 26 (1) ◽  
pp. 449-464 ◽  
Author(s):  
Mifeng Gou ◽  
Longfei Zhou ◽  
Nathalene Wei Ying Then
Keyword(s):  
Compressive Strength ◽  
Cementitious Materials ◽  
Solid Wastes ◽  
Supplementary Cementitious Materials ◽  
Cement Clinker ◽  
Fine Aggregate ◽  
Granulated Blast Furnace Slag ◽  
Fine Aggregates ◽  
Compressive Strength Of Concrete ◽  
Cement And Concrete

AbstractOne of the advantages of cement and the cement concrete industry in sustainability is the ability to utilize large amounts of industrial solid wastes such as fly ash and ground granulated blast furnace slag. Tailings are solid wastes of the ore beneficiation process in the extractive industry and are available in huge amounts in some countries. This paper reviews the potential utilization of tailings as a replacement for fine aggregates, as supplementary cementitious materials (SCMs) in mortar or concrete, and in the production of cement clinker. It was shown in previous research that while tailings had been used as a replacement for both fine aggregate and cement, the workability of mortar or concrete reduced. Also, at a constant water to cement ratio, the compressive strength of concrete increased with the tailings as fine aggregate. However, the compressive strength of concrete decreased as the replacement content of the tailings as SCMs increased, even whentailings were ground into smaller particles. Not much research has been dedicated to the durability of concrete with tailings, but it is beneficial for heavy metals in tailings to stabilize/solidify in concrete. The clinker can be produced by using the tailings, even if the tailings have a low SiO2 content. As a result, the utilization of tailings in cement and concrete will be good for the environment both in the solid waste processing and virgin materials using in the construction industry.

The Evolution of Cementitious Materials Through History

1994 ◽  
Vol 370 ◽  
Author(s):  
David Bonen ◽  
Mehmet A. Tasdemir ◽  
Shondeepl. Sarkar
Keyword(s):  
Portland Cement ◽  
High Strength ◽  
Cementitious Materials ◽  
Portland Cement Concrete ◽  
Slaked Lime ◽  
Cracking Pattern ◽  
The 19Th Century ◽  
Highly Porous ◽  
Microstructural Examination

AbstractThe use of cementitious materials dates back to the beginning of the Epipaleolithic period. Examples for ancient cementitious materials from Israel, Egypt, Turkey, and Italy are numerous.Prior to Aspdin's patent of portland cement at the first half of the 19th century, cementitious materials were composed of earth, mixture of earth and limestone, calcium sulfates, and slaked lime with and without pozzolans. The latter comprises pozzolanic materials from volcanic and sedimentary origin, crushed burnt clay brick, and dust brick. Frequently, organic fibers were incorporated for reinforcement. This paper describes the evolution of the cementitious materials through time and highlights the durability of ancient cementitious materials as compares to that of portland cement concrete.Although modem concrete is characterized by its high strength and low permeability, it often faces durability problems. In turn, ancient concretes examined exhibit low strength but have proved to be durable materials. Microstructural examination reveals that the groundmass of the latter has been carbonated and is highly porous. Nevertheless, no specific cracking pattern could be observed. The outstanding performance of ancient concrete structures implies that thermodynamic stability rather that mechanical strength is a key point for a long-term durability.

scholarly journals Long-term performance of sustainable pavements using ternary blended concrete with recycled aggregates

2021 ◽  
Author(s):  
Gilson Lomboy ◽  
Douglas Cleary ◽  
Seth Wagner ◽  
Yusef Mehta ◽  
Danielle Kennedy ◽  
...  
Keyword(s):  
Portland Cement ◽  
Cementitious Materials ◽  
Recycled Concrete ◽  
Supplementary Cementitious Materials ◽  
Recycled Aggregates ◽  
Concrete Aggregate ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
Concrete Aggregates ◽  
Concrete Mixtures

Dwindling supplies of natural concrete aggregates, the cost of landfilling construction waste, and interest in sustainable design have increased the demand for recycled concrete aggregates (RCA) in new portland cement concrete mixtures. RCA repurposes waste material to provide useful ingredients for new construction applications. However, RCA can reduce the performance of the concrete. This study investigated the effectiveness of ternary blended binders, mixtures containing portland cement and two different supplementary cementitious materials, at mitigating performance losses of concrete mixtures with RCA materials. Concrete mixtures with different ternary binder combinations were batched with four recycled concrete aggregate materials. For the materials used, the study found that a blend of portland cement, Class C fly ash, and blast furnace slag produced the highest strength of ternary binder. At 50% replacement of virgin aggregates and ternary blended binder, some specimens showed comparable mechanical performance to a control mix of only portland cement as a binder and no RCA substitution. This study demonstrates that even at 50% RCA replacement, using the appropriate ternary binder can create a concrete mixture that performs similarly to a plain portland cement concrete without RCA, with the added benefit of being environmentally beneficial.

Long-term alkali-silica mitigation of high-alkali concrete with cement replacements

2021 ◽  
pp. 1-29
Author(s):  
Douglas Hooton ◽  
Benoit Fournier
Keyword(s):  
Cementitious Materials ◽  
Outdoor Exposure ◽  
Supplementary Cementitious Materials ◽  
Concrete Prism ◽  
Different Temperatures ◽  
Concrete Blocks ◽  
High Alkali ◽  
Mortar Bar ◽  
The Impact

The impact of high-alkali Portland cements on the prescribed level of supplementary cementitious materials required in the Canadian standard for akali-silica reaction mitigation was evaluated. Based on the results, for concretes containing aggregates exhibiting moderate reactivity, the maximum allowable cement alkali limit was raised from 1.00% to 1.15%. For all levels of aggregate reactivity, cement alkali contents could be allowed up to 1.25% provided the recommended level of mitigation by supplementary cementitious materials was increased. In the initial laboratory study, mortar bars and concrete prisms were cast and monitored using two different reactive aggregates and recommended levels of fly ash and slag. For the concrete prism tests, the alkali contents of the cements were increased to 1.25%, as per the standard, or were increased by 0.25%. Instrumented outdoor exposure concrete blocks, along with additional concrete prisms stored at different temperatures, were cast from numerous mixtures made with cement alkali equivalents ranging up to 1.22%. This paper report on the long-term performance of the prisms and concrete blocks after 12 and 27 years. The performance of the outdoor blocks is also compared to predicted performance based on the accelerated mortar bar and concrete prism test results.

Pozzolanic Reaction of Supplementary Cementitious Materials and Its Effects on the Strength of Mass Concrete

2010 ◽  
Vol 168-170 ◽  
pp. 505-511 ◽  
Author(s):  
Hua Shan Yang ◽  
Kun He Fang ◽  
Sheng Jin Tu
Keyword(s):  
Cementitious Materials ◽  
Pozzolanic Reaction ◽  
Supplementary Cementitious Materials ◽  
Mass Concrete ◽  
X Ray Diffraction ◽  
X Ray ◽  
Slag Powder ◽  
Phosphorous Slag ◽  
Better Than

The present study aims to investigate the opportunity to largely substitute low heat Portland cement of mass concrete with supplementary cementitious materials. The pozzolanic reaction of two types of supplementary cementitious materials, phosphorous slag powder and fly ash , were determined by X-ray diffraction, differential thermal analysis–thermogravimetry and scanning electron microscopy from 28 to 90 days. The properties of mortar and mass concrete containing 30% of supplementary cementitious materials were also investigated. Results showed that supplementary cementitious materials could decrease the amount of calcium hydroxide, fill the capillary pores, thus making the mortar and mass concrete more compact and durable. Long-term strength of mass concrete containing 30% of supplementary cementitious materials were comparable (or even better) than the control concrete (without supplementary cementitious materials) at constant workability, while the Young’s modulus was lower than the control concrete.

Crack Growth Resistance in Fibre Reinforced Geopolymer Concrete Exposed to Sustained Extreme Temperatures

2016 ◽  
Vol 711 ◽  
pp. 511-518 ◽  
Author(s):  
Vivek Bindiganavile ◽  
Jose R.A. Goncalves ◽  
Yaman Boluk
Keyword(s):  
Portland Cement ◽  
Crack Growth ◽  
Volume Fraction ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Geopolymer Concrete ◽  
Extreme Temperatures ◽  
Portland Cement Concrete ◽  
Promising Alternative ◽  
Cement Binder

Portland cement concrete (PCC) is now second only to potable water in per capita consumption. And notwithstanding its numerous benefits, Portland cement itself is responsible for between 4 to 5% of the world’s manmade greenhouse gas emissions. In this context, geopolymer concrete is a promising alternative, wherein the Portland cement binder is replaced entirely by supplementary cementitious materials triggered by alkaline activators. Relatively little is known on the fracture response of this system, especially when exposed to extreme temperatures. The study reported here focused on the crack growth response of such a system prepared with Class F fly ash and reinforced with steel and polymeric fibres up to 1% volume fraction. The geopolymerization was effected with a blend of sodium hydroxide and sodium silicate to achieve a compressive strength of 30 MPa at 28 days. The resulting geopolymer concrete was subjected to temperatures between-30 oC to 300 oC, sustained for 2 hours. A fibre blend of steel to polypropylene in the mass ratio of 4:1 was incorporated. Based on the results, four different stages for fracture behaviour were identified with superior fibre efficiency seen at sub-zero temperatures.

scholarly journals The Influence of Chemical Activators on the Hydration Behavior and Technical Properties of Calcium Sulfoaluminate Cements Blended with Ground Granulated Blast Furnace Slags

Buildings ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 268
Author(s):  
Milena Marroccoli ◽  
Antonio Telesca
Keyword(s):  
Blast Furnace ◽  
Co2 Emissions ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
X Ray Diffraction ◽  
Cement Production ◽  
Blended Cements ◽  
Calcium Sulfoaluminate ◽  
Technical Performance ◽  
Technical Properties

The manufacture of Ordinary Portland cement (OPC) generates around 8% of the global CO2 emissions related to human activities. The last 20 years have seen considerable efforts in the research and development of methods to lower the carbon footprint associated with cement production. Specific focus has been on limiting the use of OPC and employing alternative binders, such as calcium sulfoaluminate (CSA) cements, namely special hydraulic binders obtained from non-Portland clinkers. CSA cements could be considered a valuable OPC alternative thanks to their distinctive composition and technical performance and the reduced environmental impact of their manufacturing process. To additionally reduce CO2 emissions, CSA cements can also be blended with supplementary cementitious materials. This paper investigates the influence of two separately added chemical activators (NaOH or Na2CO3) on the technical properties and hydration behavior of four CSA blended cements obtained by adding to a plain CSA cement two different ground granulated blast furnace slags. Differential thermal-thermogravimetric, X-ray diffraction and mercury intrusion porosimetry analyses were done, along with shrinkage/expansion and compressive strength measurements.

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