scholarly journals Prediction Models for Thermal Conductivity of Cement-based Composites

2018 ◽  
Vol 58 (1) ◽  
pp. 163-171 ◽  
Author(s):  
Mohammad H. Baghban ◽  
Mahdi Kioumarsi ◽  
Sotirios Grammatikos
Keyword(s):  
Thermal Conductivity ◽  
Construction Industry ◽  
Prediction Models ◽  
Cementitious Materials ◽  
Mix Design ◽  
Structural Elements ◽  
Building Envelopes ◽  
Heating Systems ◽  
Cement Based Materials ◽  
Floor Heating

Abstract Cement-based materials are the most consumed materials in the construction industry. Low or high thermal conductive cement-based materials are of interest in applications such as embedded floor heating systems, building envelopes or structural elements. This paper describes prediction models for thermal conductivity of cementitious composites by considering different variables such as constituent materials, porosity and moisture content. The presented prediction models may be used for thermal conductivity based mix design of cementitious materials. Based on the desired accuracy, different solutions are proposed.

Effect of Hydrophobic Aerogel Granules on Thermomechanical Properties of Cementitious Composites

2019 ◽  
Vol 971 ◽  
pp. 114-118
Author(s):  
Mohammad Hajmohammadian Baghban ◽  
Mohaddeseh Tahanpour Javadabadi
Keyword(s):  
Thermal Conductivity ◽  
Construction Industry ◽  
Heat Insulation ◽  
Cementitious Materials ◽  
Thermomechanical Properties ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
Low Thermal Conductivity ◽  
Thermal Bridge ◽  
Cast Concrete

Thermal conductivity is an important material property in the energy design process of the buildings. While cement-based materials are the most consumed materials in construction industry, thermal properties of these materials can play a significant role in energy efficiency of the buildings. Cementitious materials with low thermal conductivity can be desirable for using as a part of heat insulation or for thermal bridge calculations. In this study, hydrophobic aerogel granules were used as aggregate and combination of Portland cement and fly ash was considered as the binder in order to achieve a material with low thermal conductivity. Replacement of 50 vol% hardened cement paste (hcp) by aerogel granules led to about 70% reduction in thermal conductivity of air dried samples (from 0.67 W/mK to 0.20 W/mK). However, this reduction was nearly 50% in moist samples submerged in water for three days (from 0.97 W/mK to 0.50 W/mK) due to replacement of air by water in hcp pores, which can be avoided by using hydrophobic agents. The thermal conductivity can be reduced by increasing water-cement ratio as well as aerogel content. This type of composite can be used as cast concrete or on-site 3D printing of wall elements.

Study on the Thermal Conductivity Model of Cement-Based Materials by a New Test Method

2012 ◽  
Vol 457-458 ◽  
pp. 457-460 ◽  
Author(s):  
Zhen Zhong Wei ◽  
De Jian Shen ◽  
De Qing Jia
Keyword(s):  
Thermal Conductivity ◽  
Prediction Models ◽  
Aggregate Size ◽  
Test Method ◽  
Test Results ◽  
Correct Model ◽  
Cement Based Materials ◽  
Thermal Conductivity Model ◽  
Wire Method ◽  
Experimental Values

Thermal conductivity prediction models of cement-based materials are inconsistent. In order to get the correct model, parallel hot wire method is used to measure the thermal conductivity of aggregate, cement paste, mortar and cement-based materials. Theoretical analysis values and experimental values of thermal conductivity of cement-based materials are compared to get the correct series-parallel model of the material. Through further research, the test results that the influence of aggregate location and aggregate size on the thermal conductivity of cement-based materials can be ignored in the case of the same aggregate content.

scholarly journals Extrusion of cement-based materials - an overview

2019 ◽  
Vol 3 ◽  
pp. 91-97 ◽  
Author(s):  
Arnaud Perrot ◽  
Damien Rangeard ◽  
Venkatesh Naidu Nerella ◽  
Viktor Mechtcherine
Keyword(s):  
Construction Industry ◽  
Surface Defects ◽  
Soil Mechanics ◽  
Digital Fabrication ◽  
Cementitious Materials ◽  
Cement Based Materials ◽  
Mechanical Behaviours ◽  
Reinforced Cement ◽  
Pass Through ◽  
Underlying Mechanisms

Extrusion is a process that consists in forcing a formable material to pass through a die having the cross-section of the part to be obtained. This way of processing is used with conventional and fibre-reinforced cement-based materials to fabricate various construction elements such as panels, pipes and roadside curbs. Recently, with the development of digital fabrication methods and especially 3D concrete printing by selective deposition, the extrusion techniques have experienced a significant increase in interest. This letter describes the screw and ram extrusion techniques and their applications in construction industry. Furthermore, the underlying mechanisms involved during extrusion flow are delineated and the roles of rheological and hydro-mechanical behaviours (the latter one in a soil mechanics sense) in defining the extrudability – ability of being extruded – of the cementitious materials are highlighted. Finally, specific points such as flow-induced anisotropy of fibre reinforced cementitious materials or surface defects are addressed.

scholarly journals A Review on Application of Formaldehyde in Cement-Based Materials

2021 ◽  
Keyword(s):  
Construction Industry ◽  
Construction Material ◽  
Cementitious Materials ◽  
Flow Strength ◽  
Durability Properties ◽  
Cement Based Materials ◽  
Strength And Durability ◽  
The Impact ◽  
Flooring Materials ◽  
Nose And Throat

Abstract. Formaldehyde is environment contamination, which causes irritation in the eyes, nose, and throat with concentration above 1.0ppm. But still, it is used as a construction material as an admixture and furthermore to make paints, adhesives, pressed wood, and flooring materials, etc. This paper reviews the impact of formaldehyde in the cement on flow, strength, and durability properties. In this most of the researchers studied the water reducing nature of formaldehyde-based cementitious materials (FBCM) because of its repulsive property, that can ensure improved workability and provides good mechanical strength. Finally, the challenges in the application of formaldehyde in cement-based materials are discussed to conclude some future scope in the field of the construction industry to use formaldehyde in cement.

scholarly journals Energy Saving Potential of Radiant Floor Heating Assisted by an Air Source Heat Pump in Residential Buildings

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1321
Author(s):  
Yu-Jin Hwang ◽  
Jae-Weon Jeong
Keyword(s):  
Energy Saving ◽  
Heat Pump ◽  
Residential Buildings ◽  
Heating Systems ◽  
Air Source Heat Pump ◽  
Heating Capacity ◽  
Heating Loads ◽  
Radiant Floor Heating ◽  
Floor Heating ◽  
Floor Temperature

The objective of this research is to establish an appropriate operating strategy for a radiant floor heating system that additionally has an air source heat pump for providing convective air heating separately, leading to heating energy saving and thermal comfort in residential buildings. To determine the appropriate optimal operating ratio of each system taking charge of combined heating systems, the energy consumption of the entire system was drawn, and the adaptive floor surface temperature was reviewed based on international standards and literature on thermal comfort. For processing heating loads with radiant floor heating and air source heating systems, the heating capacity of radiant floor heating by 1 °C variation in floor temperature was calculated, and the remaining heating load was handled by the heating capacity of the convective air heating heat pump. Consequently, when the floor temperature was 25 °C, all heating loads were removed by radiant floor heating only. When handling all heating loads with the heat pump, 59.2% less energy was used compared with radiant floor heating only. Considering the local discomfort of the soles of the feet, the floor temperature is expected to be suitable at 22–23 °C, and 31.5–37.6% energy saving compared with those of radiant floor heating alone were confirmed.

scholarly journals Assessment for Thermal Conductivity of Frozen Soil Based on Nonlinear Regression and Support Vector Regression Methods

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Fu-Qing Cui ◽  
Wei Zhang ◽  
Zhi-Yun Liu ◽  
Wei Wang ◽  
Jian-bing Chen ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Support Vector Regression ◽  
Nonlinear Regression ◽  
Prediction Accuracy ◽  
Prediction Models ◽  
Frozen Soil ◽  
Support Vector ◽  
Soil Thermal Conductivity ◽  
Fine Grained ◽  
Fine Grained Soil

The comprehensive understanding of the variation law of soil thermal conductivity is the prerequisite of design and construction of engineering applications in permafrost regions. Compared with the unfrozen soil, the specimen preparation and experimental procedures of frozen soil thermal conductivity testing are more complex and challengeable. In this work, considering for essentially multiphase and porous structural characteristic information reflection of unfrozen soil thermal conductivity, prediction models of frozen soil thermal conductivity using nonlinear regression and Support Vector Regression (SVR) methods have been developed. Thermal conductivity of multiple types of soil samples which are sampled from the Qinghai-Tibet Engineering Corridor (QTEC) are tested by the transient plane source (TPS) method. Correlations of thermal conductivity between unfrozen and frozen soil has been analyzed and recognized. Based on the measurement data of unfrozen soil thermal conductivity, the prediction models of frozen soil thermal conductivity for 7 typical soils in the QTEC are proposed. To further facilitate engineering applications, the prediction models of two soil categories (coarse and fine-grained soil) have also been proposed. The results demonstrate that, compared with nonideal prediction accuracy of using water content and dry density as the fitting parameter, the ternary fitting model has a higher thermal conductivity prediction accuracy for 7 types of frozen soils (more than 98% of the soil specimens’ relative error are within 20%). The SVR model can further improve the frozen soil thermal conductivity prediction accuracy and more than 98% of the soil specimens’ relative error are within 15%. For coarse and fine-grained soil categories, the above two models still have reliable prediction accuracy and determine coefficient (R2) ranges from 0.8 to 0.91, which validates the applicability for small sample soils. This study provides feasible prediction models for frozen soil thermal conductivity and guidelines of the thermal design and freeze-thaw damage prevention for engineering structures in cold regions.

scholarly journals The Potentials of Iron and Steel Slags as Supplementary Cementitious Materials in the Nigerian Construction Industry: A Review

2018 ◽  
Vol 2 (2) ◽  
pp. 208-218
Author(s):  
O. R. Ogirigbo ◽  
J. O. Ukpata ◽  
I. Inerhunwa
Keyword(s):  
Portland Cement ◽  
Construction Industry ◽  
Waste Product ◽  
Steel Production ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Partial Replacement ◽  
Iron And Steel ◽  
Tropical Environments ◽  
Iron And Steel Production

Ground Granulated Blast Furnace Slag (GGBS) is a type of Supplementary Cementitious Material (SCM) that is currently being used extensively in the global construction industry. SCMs are cheaper than Portland cement, help to improve certain properties of concrete and also help to reduce the environmental footprint associated with the production of Portland cement. GGBS is readily available in most parts of the world as a waste product from iron and steel production. However, its use as a SCM in some countries has not been fully maximized. This is primarily because of lack of documented studies on the properties of GGBS that influences its suitability as a SCM, especially in tropical environments. This paper reviewed the use of GGBS as a SCM for the partial replacement of Portland cement, with particular emphasis on its potential use in tropical warm environments such as Nigeria and other similar countries.

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