Preparation and Mechanical Properties of Potassium Metakaolin Based Geopolymer Paste

In this study, geopolymer samples were prepared by mixing metakaolin (MA) with activator solution made of potassium alkali silicate solution, potassium hydroxide flakes, and additional water. The aim of the experiment is to evaluate the mechanical strength of hardened samples based on four test variables including the SiO2/K2O molar ratios, K2O concentration, H2O/MA water coefficient, and curing temperature. The results reveal that K2O concentration and H2O/MA water coefficient impact strongly on the compressive strength, whereas varying of SiO2/K2O molar ratios in the range from 1.0 – 1.4 does not significantly change the compressive strength of geopolymer samples. On the other hand, high-temperature curing leads to higher mechanical strength of the samples in the early-age compared to curing at room temperature, due to the faster establishment of hard structure in the early-age of geo-polymerization process. However, curing at a temperature range of 80°C – 100°C contributes the non-linear strength development of the samples over the time.

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

Jurnal Teknologi ◽

10.11113/jt.v77.6305 ◽

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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Compressive Strength Gain Behavior and Prediction of Cement-Stabilized Macadam at Low Temperature Curing

Journal of Advanced Transportation ◽

10.1155/2020/2469436 ◽

2020 ◽

Vol 2020 ◽

pp. 1-10

Author(s):

Yongli Xu ◽

Guang Yang ◽

Hongyuan Zhao

Keyword(s):

Compressive Strength ◽

Low Temperature ◽

Curing Temperature ◽

Strength Development ◽

Construction Process ◽

Strength Gain ◽

Estimation Model ◽

Maturity Method ◽

Temperature Ranges ◽

Natural Temperature

For cement-based materials, the curing temperature determines the strength gain rate and the value of compressive strength. In this paper, the 5% cement-stabilized macadam mixture is used. Three indoor controlled temperature curing and one outdoor natural curing scenarios are designed and implemented to study the strength development scenario law of compressive strength, and they are standard temperature curing (20°C), constant low temperature curing (10°C), day interaction temperature curing (varying from 6°C to 16°C), and one outdoor natural temperature curing (in which the air temperature ranges from 4°C to 20°C). Finally, based on the maturity method, the maturity-strength estimation model is obtained by using and analyzing the data collected from the indoor tests. The model is proved with high accuracy based on the validated results obtained from the data of outdoor tests. This research provides technical support for the construction of cement-stabilized macadam in regions with low temperature, which is beneficial in the construction process and quality control.

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Impact of Temperature on the Strength Development of the Tailing-Waste Rock Backfill of a Gold Mine

Advances in Civil Engineering ◽

10.1155/2019/4379606 ◽

2019 ◽

Vol 2019 ◽

pp. 1-9

Author(s):

Bin Han ◽

Shengyou Zhang ◽

Wei Sun

Keyword(s):

Compressive Strength ◽

Mass Concentration ◽

Critical Concentration ◽

Curing Temperature ◽

Strength Development ◽

Gold Mine ◽

Critical Interval ◽

Cement Ratio ◽

Rate Of Increase ◽

The Impact

This study investigated the influencing rules of curing temperature (5, 10, 16, and 20°C), cement ratio (8%, 10%, 12%, and 14%), and mass concentration (70%, 73%, 74%, and 75%) on the strength of backfill. In addition, a scanning electron microscope (SEM) is employed to analyze the microtopography of the backfill. Experimental results indicate that the uniaxial compressive strength (UCS) of the backfill decreases as the curing temperature diminishes; temperature substantially influences the earlier strength of backfill (it is much significant below 10°C). In addition, as the cement ratio rises, the critical point for the impact of temperature on strength gradually moves toward a low-temperature zone; in pace with the slurry mass concentration increase, the compressive strength of the backfill also rises and its rate of increase enlarges after going beyond the critical concentration. In case the curing temperature is lower than 10°C, the extent of hydration is also low inside the backfill. Through experiments, the critical concentration of slurry in the Jinying gold mine is determined as 73%, and the critical interval of the cement ratio ranged between 10% and 12%. Corresponding measures can be taken to increase the strength of backfill in the Jinying Gold Mine by 129.9%. As a result, backfill collapse is effectively controlled.

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Mine Backfilling in the Permafrost, Part II: Effect of Declining Curing Temperature on the Short-Term Unconfined Compressive Strength of Cemented Paste Backfills

Minerals ◽

10.3390/min9030172 ◽

2019 ◽

Vol 9 (3) ◽

pp. 172

Author(s):

Mamert Mbonimpa ◽

Parrein Kwizera ◽

Tikou Belem

Keyword(s):

Compressive Strength ◽

Unconfined Compressive Strength ◽

Room Temperature ◽

Freezing Temperature ◽

Curing Temperature ◽

Strength Development ◽

Short Term ◽

Practical Applications ◽

Humidity Chamber ◽

Paste Backfill

When cemented paste backfill (CPB) is used to fill underground stopes opened in permafrost, depending on the distance from the permafrost wall, the curing temperature within the CPB matrix decreases progressively over time until equilibrium with the permafrost is reached (after several years). In this study, the influence of declining curing temperature (above freezing temperature) on the evolution of the unconfined compressive strength (UCS) of CPB over 28 days’ curing is investigated. CPB mixtures were prepared with a high early (HE) cement and a blend of 80% slag and 20% General Use cement (S-GU) at 5% and 3% contents and cured at room temperature in a humidity chamber and under decreasing temperatures in a temperature-controlled chamber. Results indicate that UCS is higher for CPB cured at room temperature than under declining temperatures. UCS increases progressively from the stope wall toward the inside of the CPB mass. Under declines in curing temperature, HE cement provides better short-term compressive strength than does S-GU binder. In addition, the gradual decline in temperature does not appear to affect the fact that the higher the binder proportion, the greater the strength development. Therefore, UCS is higher for samples prepared with 5% than 3% HE cement. Findings are discussed in terms of practical applications.

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Investigation of the Relationship between Compressive Strength and Hydrate Formation Behavior of Low-Temperature Cured Cement upon Addition of a Nitrite-Based Accelerator

Materials ◽

10.3390/ma12233936 ◽

2019 ◽

Vol 12 (23) ◽

pp. 3936 ◽

Cited By ~ 1

Author(s):

Jihoon Kim ◽

Daiki Honda ◽

Heesup Choi ◽

Yukio Hama

Keyword(s):

Compressive Strength ◽

Calcium Nitrate ◽

Hydrate Formation ◽

Strength Development ◽

Early Age ◽

Enhancement Effect ◽

Freezing Damage ◽

Formation Behavior ◽

Relative Production ◽

The Relationship

When concrete is used for construction in cold-temperature regions, cold-resistant accelerators based on calcium nitrite (Ca(NO2)2) and calcium nitrate (Ca(NO3)2) are added to prevent early freezing damage. Although cold-resistant accelerators increase the early compressive strength and prevent early freezing damage by promoting cement hydration, the strength enhancement effect owing to the formation of such hydrates has not been evaluated quantitatively thus far. This study covers various types of analysis to understand the relationship between cement hydrate formation behavior and strength development upon the addition of varying amounts of nitrite-based accelerator. We find that the early compressive strength is enhanced by the addition of nitrite-based accelerator via the promotion of the relative production of monosulfate and C-S-H in the early age. However, the development of compressive strength decreases with an increase in the curing age. Furthermore, we find that the promotion of hydration reactions at an early age with the addition of nitrite-based accelerator can affect the formation ratio of each hydrate at a late age. We believe our findings can significantly contribute to developments in concrete application and allied fields.

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Recovery of Silicon Dioxide from Waste Foundry Sand and Alkaline Activation of Desilicated Foundry Sand

Journal of Sustainable Metallurgy ◽

10.1007/s40831-020-00303-5 ◽

2020 ◽

Vol 6 (4) ◽

pp. 700-714

Author(s):

Tebogo Mashifana ◽

Thandiwe Sithole

Keyword(s):

Potassium Hydroxide ◽

Solution Concentration ◽

Curing Temperature ◽

Strength Development ◽

Waste Generation ◽

Optimum Conditions ◽

Foundry Sand ◽

Solid Ratio ◽

Waste Foundry Sand ◽

Alkaline Activator

Abstract This study was conducted to recover silica (desilication) as a valuable metalloid from waste foundry sand (WFS) by a leaching process and to find application for desilicated foundry sand (DFS). The leaching time applied was 5 h; 3 M of potassium hydroxide (KOH) was used as a leaching reagent. The agitation speed of 200 rpm and the liquid/solid ratio of 25 were found to be the best conditions for optimum leaching results. A geopolymer from DFS was developed by using NaOH as an alkaline activator. The results obtained showed that the optimum conditions for the synthesis of a geopolymer were 15 M NaOH, 150 µm DFS particle size, and a curing temperature of 80 ℃ for 72 h. The geopolymer strength development was due to the formation of Phillipsite and Kalsilite as new hydration products. At the optimum alkaline solution concentration, the highest unconfined compressive strength (UCS) of 4.8 MPa was achieved. The developed geopolymer met the minimum strength requirements for load bearing material. This study provides an innovative and novel solution for the beneficiation of spent foundry sand and the recovery of a valuable metalloid, resulting to zero waste generation. Graphical Abstract

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Comparative Analysis and Strength Estimation of Fresh Concrete Based on Ultrasonic Wave Propagation and Maturity Using Smart Temperature and PZT Sensors

Micromachines ◽

10.3390/mi10090559 ◽

2019 ◽

Vol 10 (9) ◽

pp. 559 ◽

Cited By ~ 2

Author(s):

Tareen ◽

Kim ◽

Park

Keyword(s):

Phase Transition ◽

Compressive Strength ◽

Wave Propagation ◽

Ultrasonic Wave ◽

Penetration Resistance ◽

Strength Development ◽

Early Age ◽

Ultrasonic Wave Propagation ◽

Maturity Method ◽

Concrete Maturity

Recently, the early-age strength prediction for RC (reinforced concrete) structures has been an important topic in the construction industry, relating to project-time reduction and structural safety. To address this, numerous destructive and NDTs (non-destructive tests) are applied to monitor the early-age strength development of concrete. This study elaborates on the NDT techniques of ultrasonic wave propagation and concrete maturity for the estimation of compressive strength development. The results of these comparative estimation approaches comprise the concrete maturity method, penetration resistance test, and an ultrasonic wave analysis. There is variation of the phase transition in the concrete paste with the changing of boundary limitations of the material in accordance with curing time, so with the formation of phase-transition changes, changes in the velocities of ultrasonic waves occur. As the process of hydration takes place, the maturity method produces a maturity index using the time-feature reflection on the strength-development process of the concrete. Embedded smart temperature sensors (SmartRock) and PZT (piezoelectric) sensors were used for the data acquisition of hydration temperature history and wave propagation. This study suggests a novel relationship between wave propagation, penetration tests, and hydration temperature, and creates a method that relies on the responses of resonant frequency changes with the change of boundary conditions caused by the strength-gain of the concrete specimen. Calculating the changes of these features provides a pattern for estimating concrete strength. The results for the specimens were validated by comparing the strength results with the penetration resistance test by a universal testing machine (UTM). An algorithm used to relate the concrete maturity and ultrasonic wave propagation to the concrete compressive strength. This study leads to a method of acquiring data for forecasting in-situ early-age strength of concrete, used for secure construction of concrete structures, that is fast, cost effective, and comprehensive for SHM (structural health monitoring).

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Difference in Strength Development between Cement-Treated Sand and Mortar with Various Cement Types and Curing Temperatures

Materials ◽

10.3390/ma13214999 ◽

2020 ◽

Vol 13 (21) ◽

pp. 4999

Author(s):

Lanh Si Ho ◽

Kenichiro Nakarai ◽

Kenta Eguchi ◽

Yuko Ogawa

Keyword(s):

Portland Cement ◽

Ordinary Portland Cement ◽

Bound Water ◽

Curing Temperature ◽

Strength Development ◽

Early Age ◽

Cement Type ◽

A Value ◽

Water To Cement Ratio ◽

Novel Method

To improve the strength of cement-treated sand effectively, the use of various cement types was investigated at different curing temperatures and compared with the results obtained from similar mortars at higher cement contents. The compressive strengths of cement-treated sand specimens that contained high early-strength Portland cement (HPC) cured at elevated and normal temperatures were found to be higher than those of specimens that contained ordinary Portland cement (OPC) and moderate heat Portland cement at both early and later ages. At 3 days, the compressive strength of the HPC-treated sand specimen, normalized with respect to that of the OPC under normal conditions, is nearly twice the corresponding value for the HPC mortar specimens with water-to-cement ratio of 50%. At 28 days, the normalized value for HPC-treated sand is approximately 1.5 times higher than that of mortar, with a value of 50%. This indicates that the use of HPC contributed more to the strength development of the cement-treated sand than to that of the mortar, and the effects of HPC at an early age were higher than those at a later age. These trends were explained by the larger quantity of chemically bound water observed in the specimens that contained HPC, as a result of their greater alite contents and porosities, in cement-treated sand. The findings of this study can be used to ensure the desired strength development of cement-treated soils by considering both the curing temperature and cement type. Furthermore, they suggested a novel method for producing a high internal temperature for promoting the strength development of cement-treated soils.

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Effect of Partial Replacement of Fly Ash by Metakaolin on Strength Development of Fly Ash Based Geopolymer Mortar

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.744.131 ◽

2017 ◽

Vol 744 ◽

pp. 131-135 ◽

Cited By ~ 4

Author(s):

Muhammad Zahid ◽

Nasir Shafiq ◽

Mohd Fadhil Nuruddin ◽

Ehsan Nikbakht ◽

Asif Jalal

Keyword(s):

Compressive Strength ◽

Fly Ash ◽

Sodium Hydroxide Solution ◽

Base Material ◽

Sodium Silicate Solution ◽

Silicate Solution ◽

Partial Replacement ◽

Strength Development ◽

Class C ◽

Class F

This article aims to investigate the compressive strength variation by the addition of metakaolin as a substitute of fly ash in the fly ash based geopolymer mortar. Five, ten and fifteen percent by weight of fly ash was replaced by highly reactive metakaolin. Two type of fly ashes namely, ASTM class F and ASTM class C were used as a base material for the synthesis of geopolymer mortar. Eight molar sodium hydroxide solution mixed with sodium silicate solution was used as alkaline activator. For optimum geopolymerization, mortar was cured at sixty degree Celsius for twenty four hours duration. Results show different behavior of metakaolin replacement on compressive strength for two different types of fly ash based geopolymer mortar. Improvement in compressive strength was seen by addition of metakaolin in ASTM class F fly ash based geopolymer. On the other hand compressive strength was decreased abruptly in fly ash class C based geopolymer up to certain replacement level.

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Effect of Curing Temperature Histories on the Compressive Strength Development of High-Strength Concrete

Advances in Materials Science and Engineering ◽

10.1155/2015/965471 ◽

2015 ◽

Vol 2015 ◽

pp. 1-12 ◽

Cited By ~ 5

Author(s):

Keun-Hyeok Yang ◽

Jae-Sung Mun ◽

Myung-Sug Cho

Keyword(s):

Compressive Strength ◽

High Strength Concrete ◽

High Strength ◽

Relative Strength ◽

Curing Temperature ◽

Strength Development ◽

Curing Conditions ◽

Strength Concrete ◽

Equivalent Age ◽

Compressive Strength Development

This study examined the relative strength-maturity relationship of high-strength concrete (HSC) specifically developed for nuclear facility structures while considering the economic efficiency and durability of the concrete. Two types of mixture proportions with water-to-binder ratios of 0.4 and 0.28 were tested under different temperature histories including (1) isothermal curing conditions of 5°C, 20°C, and 40°C and (2) terraced temperature histories of 20°C for an initial age of individual 1, 3, or 7 days and a constant temperature of 5°C for the subsequent ages. On the basis of the test results, the traditional maturity function of an equivalent age was modified to consider the offset maturity and the insignificance of subsequent curing temperature after an age of 3 days on later strength of concrete. To determine the key parameters in the maturity function, the setting behavior, apparent activation energy, and rate constant of the prepared mixtures were also measured. This study reveals that the compressive strength development of HSC cured at the reference temperature for an early age of 3 days is insignificantly affected by the subsequent curing temperature histories. The proposed maturity approach with the modified equivalent age accurately predicts the strength development of HSC.

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