scholarly journals Effect of Mix Constituents and Curing Conditions on Compressive Strength of Sustainable Self-Consolidating Concrete

2019 ◽  
Vol 11 (7) ◽  
pp. 2094 ◽  
Author(s):  
Osama Ahmed Mohamed
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Silica Fume ◽  
Stability Index ◽  
Strength Development ◽  
Self Consolidating Concrete ◽  
Curing Conditions ◽  
Practical Applications ◽  
Water Curing ◽  
Curing Method

The production of cement requires significant energy and is responsible for more than 5% of global CO2 emissions; therefore it is imperative to reduce the production and use of ordinary portland cement (OPC). This paper examines the compressive strength development of low water-to-binder (w/b) ratio self-consolidating concrete (SCC) in which 90% of the cement is replaced with industrial by-products including ground granulated blast furnace slag (GGBS), fly ash, and silica fume. The emphasis in this paper is on replacing a large volume of cement with GGBS, which represented 10% to 77.5% of the cement replaced. Fresh properties at w/b ratio of 0.27 were examined by estimating the visual stability index (VSI) and t50 time. The compressive strength was determined after 3, 7, 28, and 56 days of curing. The control mix made with 100% OPC developed compressive strength ranging from 55 MPa after three days of curing to 76.75 MPa after 56 days of curing. On average, sustainable SCC containing 10% OPC developed strength ranging from 31 MPa after three days of curing to 56.4 MPa after 56 days of curing. However, the relative percentages of fly ash, silica fume, and GGBS in the 90% binder affect the strength developed as well. In addition, this paper reports the effect of the curing method on the 28 day compressive strength of environmentally friendly SCC in which 90% of the cement is replaced by GGBS, silica fume, and fly ash. The highest compressive strength was achieved in samples that were cured for three days under water, then left to air-dry for 25 days, compared to samples cured using chemical compounds or samples continuously cured under water for 28 days. The study confirms that SCC with 10% OPC and 90% supplementary cementitious composites (GGBS, silica fume, fly ash) can achieve compressive strength sufficient for many practical applications by incorporating high amounts of GGBS. In addition, air-curing of samples in a relatively high temperature (after three days of water curing) produce a higher 28 day compressive strength compared to water curing for 28 days, or membrane curing.

scholarly journals Durability and Compressive Strength of High Cement Replacement Ratio Self-Consolidating Concrete

Buildings ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 153 ◽  
Author(s):  
Osama Mohamed
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Silica Fume ◽  
Structural Engineering ◽  
Chloride Ion ◽  
Strength Development ◽  
Replacement Ratio ◽  
Self Consolidating Concrete ◽  
Granulated Blast Furnace Slag ◽  
Chloride Penetration Resistance

This study examines durability and mechanical properties of sustainable self-consolidating concrete (SCC) in which 80% of the cement is replaced with combinations of recycled industrial by-products including fly ash, silica fume, and ground granulated blast furnace slag (GGBS). The water to binder (w/b) ratio of SCC mixes studies was maintained at 0.36. The study proposes empirical relationships to predict 28-day compressive strengths based on the results of three-day and seven-day compressive strengths. In addition, the chloride penetration resistance of the various sustainable SCC mixes was determined after three days, seven days, and 28 days of moist curing of concrete standards. It was concluded that fly ash, silica fume, and GGBS contribute favorably to enhancing strength development, fresh properties, and durability of SCC in comparison to ordinary Portland cement (OPC). The compressive strength of the sustainable SCC mixes falls within ranges suitable for structural engineering applications. Replacing cement with 15% silica fume produced a 28-day average compressive strength of 95.3 MPa, which is 44.2% higher than the control mix. Replacing cement with 15% or 20% silica fume reduced the chloride ion permeability to very low amounts compared to high permeability in a control mix.

HYDRATION KINETICS OF CEMENT PASTE WITH SILICA FUME AND FLY ASH

2016 ◽  
Vol 3 (1) ◽  
Author(s):  
Miguel Picornell ◽  
Sameer Hamoush ◽  
Taher Abu-Lebdeh
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Silica Fume ◽  
Cement Paste ◽  
Regional Analysis ◽  
Testing Machine ◽  
Testing System ◽  
Hydration Kinetics ◽  
Curing Conditions ◽  
Water Curing

This research study investigates the effect of fly ash and silica fume on the cement paste hydration. A total of 350 samples of different percentages of each additive were tested and compared with the controlled cement paste without additives. Testing method includes water curing and vacuum curing conditions and involves the use of Forney Universal Testing Machine and MTS Landmark Servohydraulic Testing System (MTS) for compressive strength; Fourier Transfer Infrared Spectroscopy (FTIR) monitored the hydration with spectra; and Scanning Electron Microscope (SEM) generated images for regional analysis. Compressive strength testing demonstrated that silica fume replacement had the highest overall strength under water curing. Replacement of fly ash exhibited the highest overall strength under vacuum curing. The hydration process was monitored with the use of FTIR and SEM. Signatures of CSH which produce most of the concretes’ strength, has been determined and examined from 3 to 56 days. FTIR and SEM testing showed an increase in the change of CSH area with age. SEM testing revealed the formation of pores, CSH, and CH in images at all ages. The area of CSH grows most in early ages and diminishes over time. It is clear that the method of curing makes a difference in hydration. Results indicated that the area at which the possible formation of CSH was determined from each sample, has increased with respect to time; signifying the increase in strength over the course of testing days.

scholarly journals Compressive Strength Performance of Alkali Activated Concretes under Different Curing Conditions

2021 ◽  
Author(s):  
Anıl Niş ◽  
İlhan Altındal
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Strength Performance ◽  
Curing Conditions ◽  
Standardization Process ◽  
Water Curing ◽  
Curing Regimes ◽  
Alkali Activated Concrete ◽  
Alkali Activated ◽  
Ambient Curing

This study investigated the influence of different curing conditions on the compressive strength (CS) of the different alkali activated concrete (AAC) specimens at the ages of 2, 28, and 90 days for the structural utilization and standardization process of AAC instead of OPC concrete. For this aim, 100% slag (S100), 75% slag and 25% fly ash (S75FA25), and 50% slag and 50% fly ash based (S50FA50) AAC specimens were produced. Based on the oven-curing (O), water-curing (W), and ambient-curing (A) methods, the influence of 2O for 2 days, 26A2O, 2O26A, 28A, 28W, 26W2O, and 2O26W for 28 days, and 88A2O, 2O88A, 90A, 88W2O, 2O88W, 90W for 90 days on the CS of the AAC were examined in details. In addition, the influence of delayed oven-curing conditions on CS development was also investigated. The results indicated that curing conditions significantly affected on the CS and the water-curing condition could provide a better CS for those of AAC at 90 days. Although, the oven-curing enhanced CS of the S100 specimens at initial ages (first oven-curing applied), delayed oven-curing (oven-curing applied later) was found significant for S75FA25 and S50FA50 specimens. The delayed oven-curing affected more on the CS of the AAC when fly ash content increased. The most of AAC specimens with oven-curing had significantly enhanced the CS at 28 days, but S50FA50 at the age of 90 days decreased. Different curing regimes were proposed for the superior compressive strength values for each AAC specimens at the ages of 28 and 90 days.

scholarly journals Influence of Mechanical and Mineralogical Activation of Biomass Fly Ash on the Compressive Strength Development of Cement Mortars

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6654
Author(s):  
Jakub Popławski ◽  
Małgorzata Lelusz
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Silica Fume ◽  
Cement Mortar ◽  
Setting Time ◽  
Green Energy ◽  
Biomass Combustion ◽  
Strength Development ◽  
Compressive Strength Development ◽  
Biomass Fly Ash

Biomass combustion is a significant new source of green energy in the European Union. The adequate utilization of byproducts created during that process is a growing challenge for the energy industry. Biomass fly ash could be used in cement composite production after appropriate activation of that material. This study had been conducted to assess the usefulness of mechanical and physical activation methods (grinding and sieving), as well as activation through the addition of active silica in the form of silica fume, as potential methods with which to activate biomass fly ash. Setting time, compressive strength, water absorption and bulk density tests were performed on fresh and hardened mortar. While all activation methods influenced the compressive strength development of cement mortar with fly ash, sieving of the biomass fly ash enhanced the early compressive strength of cement mortar. The use of active silica in the form of silica fume ensured higher compressive strength results than those of control specimens throughout the entire measurement period.

Durability of Sustainable Self-Consolidating Concrete

2018 ◽  
Vol 765 ◽  
pp. 285-289
Author(s):  
Osama Ahmed Mohamed ◽  
Waddah Al Hawat ◽  
Omar Fawwaz Najm
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Silica Fume ◽  
Cementitious Materials ◽  
Chloride Penetration ◽  
Supplementary Cementitious Materials ◽  
Test Results ◽  
Self Consolidating Concrete ◽  
Human Footprint ◽  
Granulated Blast Furnace Slag

Supplementary cementitious materials such as fly ash, silica fume and ground granulated blast furnace slag (GGBS) have been used widely to partially replace cement in producing self-consolidating concrete (SCC). The production of cement is associated with emission of significant amounts of CO2 and increases the human footprint on the environment. Fly ash, silica fume, and GGBS are recycled industrial by-products that also impart favorable fresh and hardened properties on concrete. This study aims to assess the effect of the amounts of fly ash and silica fume on strength and chloride penetration resistance of concrete. Rapid Chloride Penetration Test (RCPT) was used to assess the ability of SCC to resist ingress of chlorides into concrete. SCC mixes with different dosages of fly ash and silica fume were developed and tested at different curing ages. Test results showed that replacing 20% of cement with fly ash produced the highest compressive strength of 67.96 MPa among all fly ash-cement binary mixes. Results also showed that replacing15% of cement with silica fume produced the highest compressive strength of 95.3 MPa among fly ash-cement binary mixes. Using fly ash and silica fume consistently increased the concrete resistance to chloride penetration at the early ages. Silica fume at all dosages results in low or very low levels of chloride penetration at all curing ages of concrete.

Development of Cementless Fly Ash Based Alkali-Activated Mortar

2009 ◽  
Vol 417-418 ◽  
pp. 721-724 ◽  
Author(s):  
Kyung Taek Koh ◽  
Su Tae Kang ◽  
Gum Sung Ryu ◽  
Hyun Jin Kang ◽  
Jang Hwa Lee
Keyword(s):  
Compressive Strength ◽  
High Temperature ◽  
Fly Ash ◽  
High Strength ◽  
Molar Ratio ◽  
Early Age ◽  
Water Curing ◽  
Curing Method ◽  
Alkali Activated Concrete ◽  
Alkali Activated

This study investigates the effects of alkaline activators and curing method on the compressive strength of mortar for the development of cementless alkali-activated concrete using 100% of fly ash as binder. Results reveal that the compressive strength improved according to the increase of the molar concentration of NaOH. In addition, molar ratio Na2O to SiO2 of 1.12 activated the reaction of fly ash with Si and Al constituents and resulted in the most remarkable development of strength. In the case of mortar requiring high strength at early age, higher curing temperatures appeared to be advantages. Curing at 60°C during 48 hours is recommended for requiring high strength at age 28days. Moreover, performing atmospheric curing after high temperature curing appeared to be more effective for the development of strength than water curing. Based on these results, it has been analyzed that alkaline activators fabricated with proportions of 1:1 of 9M NaOH and sodium silicate should be used and that atmospheric curing should be performed after curing at 60°C during 48 hours to produce high strength alkali-activated mortar exhibiting compressive strength of 70MPa at age 28 days.

EFFECT OF POST-CURING REGIME ON DENSITY, COMPRESSIVE STRENGTH AND CROSSLINKING OF POLYMER CONCRETE

2015 ◽  
Vol 77 (12) ◽  
Author(s):  
Nur Hafizah A. Khalid ◽  
Mohd Warid Hussin ◽  
Mohammad Ismail ◽  
Mohamed A. Ismail ◽  
Azman Mohamed ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Apparent Density ◽  
Curing Temperature ◽  
Polymerization Process ◽  
Polymer Concrete ◽  
Strength Development ◽  
Sem Images ◽  
Curing Conditions ◽  
Curing Method ◽  
Curing Regime

Polymer concrete is produced from polymer binder, aggregates, and filler. Its curing follows the polymerization process once polymer additive is added, and can be accelerated through post-curing. In this study, the Orthophthalic- and Isophthalic-based polymer concrete (Ortho-PC and Iso-PC) were cured and investigated at different curing temperature (30oC, 50oC and 70oC) and period (1, 3, 6, 16, 24 hours) to complete the compressive strength development. Effect of curing temperature and period on apparent density, compressive strength, and morphology properties were investigated. The outcomes exhibited that all specimens had achieved full compressive strength within 6 hours of curing time at both 50oC and 70oC. When cured at 30oC, this went up to more than 16 hours of curing period to achieve the same compressive strength. The form of crosslinking at different curing conditions was captured in Scanning Electron Microscope, SEM images. Results also showed that curing temperature and period insignificant affected the apparent density. This study can be used as references to manufacturer, fabricator, and engineers when dealing with polymer concrete which goes for post-curing method as curing process.

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