scholarly journals Influence of Parent Concrete Properties on Compressive Strength and Chloride Diffusion Coefficient of Concrete with Strengthened Recycled Aggregates

Materials ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 4631 ◽  
Author(s):  
Jingwei Ying ◽  
Zewen Han ◽  
Luming Shen ◽  
Wengui Li
Keyword(s):  
Compressive Strength ◽  
Diffusion Coefficient ◽  
Water Absorption ◽  
Recycled Aggregates ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Wide Range ◽  
Different Types ◽  
Compressive Strength Of Concrete ◽  
Silica Slurry

Parent concrete coming from a wide range of sources can result in considerable differences in the properties of recycled coarse aggregate (RCA). In this study, the RCAs were obtained by crushing the parent concrete with water-to-cement ratios (W/Cparent) of 0.4, 0.5 and 0.6, respectively, and were strengthened by carbonation and nano-silica slurry wrapping methods. It was found that when W/Cparen was 0.3, 0.4 and 0.5, respectively, compared with the mortar in the untreated RCA, the capillary porosity of the mortar in the carbonated RCA decreased by 19%, 16% and 30%, respectively; the compressive strength of concrete containing the carbonated RCA increased by 13%, 11% and 13%, respectively; the chloride diffusion coefficient of RAC (DRAC) containing the nano-SiO2 slurry-treated RCA decreased by 17%, 16% and 11%; and that of RAC containing the carbonated RCA decreased by 21%, 25% and 26%, respectively. Regardless of being strengthened or not, both DRAC and porosity of old mortar in RCAs increased with increasing W/Cparent. For different types of RCAs, DRAC increased obviously with increasing water absorption of RCA. Finally, a theoretical model of DRAC considering the water absorption of RCA was established and verified by experiments, which can be used to predict the DRAC under the influence of different factors, especially the water absorption of RCA.

scholarly journals Effects after 1500 Hardening Days on the Microstructure and Durability-Related Parameters of Mortars Produced by the Incorporation of Waste Glass Powder as a Clinker Replacement

2021 ◽  
Vol 13 (7) ◽  
pp. 3979
Author(s):  
Rosa María Tremiño ◽  
Teresa Real-Herraiz ◽  
Viviana Letelier ◽  
Fernando G. Branco ◽  
José Marcos Ortega
Keyword(s):  
Diffusion Coefficient ◽  
Water Absorption ◽  
Glass Powder ◽  
Cementitious Materials ◽  
Cement Industry ◽  
Waste Glass ◽  
Supplementary Cementitious Materials ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Waste Glass Powder

One of the ways of lessening the CO2 emissions of cement industry consists of replacing clinkers with supplementary cementitious materials. The required service life of real construction elements is long, so it is useful to characterize the performance of these materials in the very long term. Here, the influence of incorporating waste glass powder as a supplementary cementitious material, regarding the microstructure and durability of mortars after 1500 hardening days (approximately 4 years), compared with reference mortars without additions, was studied. The percentages of clinker replacement by glass powder were 10% and 20%. The microstructure was studied using impedance spectroscopy and mercury intrusion porosimetry. Differential thermal and X-ray diffraction analyses were performed for assessing the pozzolanic activity of glass powder at the end of the time period studied. Water absorption after immersion, the steady-state diffusion coefficient, and length change were also determined. In view of the results obtained, the microstructure of mortars that incorporated waste glass powder was more refined compared with the reference specimens. The global solid fraction and pores volume were very similar for all of the studied series. The addition of waste glass powder reduced the chloride diffusion coefficient of the mortars, without worsening their behaviour regarding water absorption after immersion.

Influence of the Nanomaterials of Kaolin Content on the Chloride Permeability of Cement Mortar

2017 ◽  
Vol 730 ◽  
pp. 406-411 ◽  
Author(s):  
Xiao Yu Guo ◽  
Ying Fang Fan ◽  
Kun Yang
Keyword(s):  
Compressive Strength ◽  
Diffusion Coefficient ◽  
Cement Mortar ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Chloride Permeability

This study investigated the influence of nanokaolin content on the behavior of cement mortar at various curing ages. The fluidity, chloride permeability, bending and compressive strength of cement mortar with various nanokaolin additives were examined. The addition of 0%, 1%, 2%, 3%, 4%, 5% and 6% nanokaolin were taken into consideration. The results showed that the addition of nanokaolin decreases the fluidity of cement mortar, and the fluidity the cement mortar decreases with the increase of nanokaolin additives. It is obtained that the addition of nanokaolin increases both the bending and compressive strength of cement mortar, and with the increase of nanokaolin additives, the bending and compressive strength of cement mortar increase. The addition of 4% nanokaolin can result in a significant low chloride permeability of cement mortar among the seven dosages. The chloride diffusion coefficient of the mortar with the addition of 4% nanokaolin was decreased by 18.93%, 12.68% and 31.05% at 7, 14 and 28 curing days, respectively.

scholarly journals Evaluation of Chloride Resistance of Early-Strength Concrete Using Blended Binder and Polycarboxylate-Based Chemical Admixture

2020 ◽  
Vol 10 (8) ◽  
pp. 2972 ◽  
Author(s):  
Taegyu Lee ◽  
Jaehyun Lee
Keyword(s):  
Compressive Strength ◽  
Diffusion Coefficient ◽  
Portland Cement ◽  
Chloride Ion ◽  
Strength Criterion ◽  
Chloride Ions ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Characteristic Strength ◽  
Early Strength

The mixing proportions of concrete were examined with regard to the durability performance and early strength in coastal areas. Research was conducted to improve the C24 mix (characteristic strength of 24 MPa). C35 concrete (characteristic strength of 35 MPa) was selected as a comparison group, as it exhibits the minimum proposed strength criterion for concrete in the marine environment. To secure the early strength of the C24 concrete, 50% of the total ordinary Portland cement (OPC) binder was replaced with early Portland cement (EPC); and to provide durability, 20% was substituted with ground granulated blast-furnace slag (GGBS). In addition, a polycarboxylate (PC)-based superplasticizer was used to reduce the unit water content. The compressive strength, chloride ion diffusion coefficient, chloride penetration depth, and pore structure were evaluated. After one day, the compressive strength improved by 40% when using EPC and GGBS, and an average increase of 20% was observed over 91 days. EPC and GGBS also reduced the overall porosity, which may increase the watertightness of concrete. The salt resistance performance was improved because the rapid early development of strength increased the watertightness of the surface and immobilization of chloride ions, decreasing the chloride diffusion coefficient by 50%.

Influence of Fly Ash to Concrete Protecting Steel Corrosion Ability

2015 ◽  
Vol 744-746 ◽  
pp. 169-172 ◽  
Author(s):  
Qiao Yang ◽  
Xiao E Zhu
Keyword(s):  
Diffusion Coefficient ◽  
Fly Ash ◽  
Water Absorption ◽  
Permeability Coefficient ◽  
Corrosion Potential ◽  
Steel Corrosion ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Concrete Permeability ◽  
The Common

The compressive strengths of the concrete cubes added fly ash were increased 53.2%, the density was almost unchanged, but the water absorption was decreased 30%. The concrete permeability coefficient and chloride diffusion coefficient added fly ash were lower than the common concrete at all ages. The concrete specimens corrosion potential added fly ash were higher than-300mV, while common concrete almost were lower than-500mV. Corrosion probability was small and there was no crack and corrosion pot on the surface of the specimens until 82 times cycles in wet-dry chlorides solution. Fly ash in concrete has obvious act for improving concrete behavior in protecting the embedded steel in corrosion.

scholarly journals THE INFLUENCE OF RIVER AND VOLCANIC SAND AS COATINGS ON POLYPROPYLENE WASTE COARSE AGGREGATE TOWARDS CONCRETE COMPRESSIVE STRENGTH

2020 ◽  
Vol 82 (4) ◽  
Author(s):  
Gandjar Pamudji ◽  
Madsuri Satim ◽  
Mochamad Chalid ◽  
Heru Purnomo
Keyword(s):  
Compressive Strength ◽  
Water Absorption ◽  
Coarse Aggregate ◽  
Experimental Tests ◽  
Concrete Compressive Strength ◽  
Replacement Ratio ◽  
River Sand ◽  
Aggregate Concrete ◽  
Different Types ◽  
Compressive Strength Of Concrete

One of the most important factors used to determine the compressive strength of concrete is its aggregate and matrix adhesion. This study examines the surface properties of polypropylene (PP) waste coarse aggregate (PWCA) to determine the influence of sand. The PWCA was made from the PP waste and different types of coating such as PWCA-R (river sand) and PWCA-V (volcanic sand), with experimental tests conducted on the physical properties of sand and PWCA, while the compressive strength, FESEM and density of polypropylene waste coarse aggregate concrete (PWCAC). Concrete specimens were prepared by replacing natural coarse aggregate with PWCA in percentages of 0%, 25%, 50%, 75%, and 100%, varying the water-cement ratio by 0.3 and 0.42 and using polypropylene (PP) waste coarse aggregate (PWCA-R and PWCA-V) as the coating material. The results showed that fineness modulus (F.M) and water absorption of the river sand was higher compared to volcanic sand. The PWCA-V had higher density and specific gravity compared to PWCA-R. On the other hand, water absorption of the PWCA-V was lower than PWCA-R. The PWCA concrete had density which varies from 1740 kg/m3 to 2074 kg/m3. For both, the PWCA concrete compressive strength at 28 days with a 100% replacement ratio was reduced by 43% to 55% compared to the natural coarse aggregate (NCA) concrete with 0.3 and 0.42 water-cement ratios. Also, the structural efficiency of PWCAC decreased with an increase in replacement ratio. River sand adhered to the PWCA surface resulted in a better compressive strength value compared to the volcanic sand. 

scholarly journals Engineering Properties of Ternary Cementless Blended Materials

2020 ◽  
Vol 10 (3) ◽  
pp. 191-199
Author(s):  
Wei-Ting Lin ◽  
Kinga Korniejenko ◽  
Marek Hebda ◽  
Michał Łach ◽  
Janusz Mikuła
Keyword(s):  
Compressive Strength ◽  
Diffusion Coefficient ◽  
Blast Furnace ◽  
Fly Ash ◽  
Blast Furnace Slag ◽  
Engineering Properties ◽  
Chloride Diffusion ◽  
Total Charge ◽  
Chloride Diffusion Coefficient ◽  
Furnace Slag

A new non-cement blended materials is developed as a full replacement of cement without alkali activator. This study was conducted to explore a suitable method for activating new ternary green materials with desulfurization gypsum, water-quenched blast-furnace slag and co-fired fly ash from circulating fluidized bed combustion as non-cement inorganic binder. Test subject was included flowability, compressive strength, absorption, total charge-passed from rapid chloride permeability test, chloride diffusion coefficient from accelerated chloride migration test and SEM observation. Test results indicate that a ternary mixture containing 1% desulfurization gypsum, 60% water-quenched blast-furnace slag and 39% co-fired fly ash was a suitable development in compressive strength. The new non-cement blended materials were performed a well compressive strength, lower absorption, and lower chloride diffusion coefficient. In addition, the compressive strength decreased as the inclusion of desulfurization gypsum increased. It was concluded that using desulfurization gypsum alone decreased the setting time and compressive strength. SEM micrographs were verified the development in compressive strength originated from the C-S-H and C-A-S-H gel produced by Ca(OH)2, SiO2, and Al2O3.

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