Effects of Limestone Powder in Manufactured Fine Aggregate on Early Hydration Process and Types of Cement Hydrates

2009 ◽  
Vol 405-406 ◽  
pp. 262-266
Author(s):  
Ji Wei Cai ◽  
Shao Bo Zhang ◽  
Ming Kai Zhou ◽  
Bei Xing Li
Keyword(s):  
Fly Ash ◽  
Calcium Hydroxide ◽  
Hydration Process ◽  
Limestone Powder ◽  
Fine Aggregate ◽  
Dormant Period ◽  
Early Hydration ◽  
Acceleration Period ◽  
Hydrated Calcium

The crusher dust in Manufactured fine aggregate (MFA), e.g. limestone powder in calcareous MFA, constitutes micro gradation of the aggregate and suitable content of crusher dust in MFA can improve the properties of concretes. In this paper, early hydration processes of samples substituting limestone powder and fly ash for part of cement are analyzed, and effects of limestone powder on cement hydrates are studied through experiment of mortar prepared with MFA partially replaced by limestone powder and fly ash. The result reveals that both the dormant period and acceleration period of hydration ended earlier in the samples substituting limestone powder for part of cement, and amount of crystals of calcium hydroxide and hydrated calcium carboaluminate increases in hardened paste in the samples substituting limestone powder for part of MFA, i.e. calcareous dust (limestone powder) in MFA can stimulate and enhance hydration of cement.

scholarly journals The Relationship between Cementitious Composition and Properties of Ultrahigh Strength Concrete

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Dehui Wang ◽  
Zhiwen Zhang
Keyword(s):  
Fly Ash ◽  
Calcium Hydroxide ◽  
Silica Fume ◽  
Design Method ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Strength Concrete ◽  
Ultrahigh Strength ◽  
Acceleration Period ◽  
The Relationship

It is well known that supplementary cementitious materials (SCMs) have obvious effects on the properties of concrete. In order to understand the relationship between cementitious materials and properties of ultrahigh strength concrete (UHSC), the cementitious compositions of UHSC were designed by the simple-centroid design method. The effects of cementitious compositions on the properties of UHSC were investigated. It was found that the incorporation of silica fume (SF) improved the flowability and strength of UHSC, but it decreased the time of acceleration period, calcium hydroxide (CH) content, and porosity of UHSC at a certain content. The incorporation of fly ash (FA) increased the flowability, time of acceleration period, and porosity of UHSC, but it decreased the strength and CH content of UHSC. The relationships between cement, silica fume, and fly ash and the properties of UHSC were calculated based on the simple-centroid design method.

Ultrasound In Situ Testing of early Hydration Process of Supplementary Cementitious Pastes

2011 ◽  
Vol 477 ◽  
pp. 132-135 ◽  
Author(s):  
Zhi Yong Liu ◽  
Yun Sheng Zhang ◽  
Guo Wen Sun ◽  
Qian Jiang ◽  
Wei Wei Zhu
Keyword(s):  
Fly Ash ◽  
Silica Fume ◽  
Hydration Process ◽  
Mineral Admixtures ◽  
Early Hydration ◽  
Water To Cement Ratio ◽  
Influence Of Water ◽  
Binder Ratio ◽  
Water To Binder Ratio

The early hydration process was investigated using ultrasonic monitoring apparatus for pastes made with various mineral admixtures: silica fume (4%, 13%), slag (10%, 30%, 50%, 70%), and fly ash (10%, 30%, 50%). The influence of water to binder ratio (0.23, 0.35 and 0.53) was also studied. The results show that the hydration rate of cementitious material is obviously accelerated with decreasing in water to cement ratio and Silica fume addition, while the reverse phenomenon is observed when fly ash and slag are incorporated.

scholarly journals The Role of Various Powders during the Hydration Process of Cement-Based Materials

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Shuhua Liu ◽  
Hongling Wang ◽  
Jianpeng Wei
Keyword(s):  
Early Stage ◽  
Steel Slag ◽  
Pozzolanic Reaction ◽  
Hydration Process ◽  
Limestone Powder ◽  
Strength Development ◽  
Early Hydration ◽  
Cement Based Materials ◽  
Early Strength

The role of various powders including glass powder (GP), limestone powder (LP), and steel slag powder (SSP) during the hydration process of cement-based materials was investigated by using X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA), scanning electron microscopy (SEM), and strength tests. GP has adverse impact on early strength, but the pozzolanic reaction at later stage enhances the strength development greatly. LP can significantly improve early strength. SSP has a good contribution to the early and later strength of the paste when its content is less than 15%. GP has little effect on the kind of hydration products but relatively large effects on the quantity. Calcium hydroxide (CH) content of GP paste decreases over curing age gradually, which is different from pure cement paste because its pozzolanic activity consumes more CH than that generated from the cement hydration. SSP and LP mainly play a role of filling effect at early stage. Nucleating effect of LP also promotes the early hydration of cement. The hydration of LP occurs at later stage and forms the calcium carboaluminate hydrates. The hydration of SSP is relatively slow, which generates CH at later stage and is effective in the strength development.

Reaction Products in Fly Ash Concrete

1984 ◽  
Vol 43 ◽  
Author(s):  
Mark D. Baker ◽  
Joakim G. Laguros
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Calcium Hydroxide ◽  
Setting Time ◽  
Heat Of Hydration ◽  
Hydration Process ◽  
Reaction Products ◽  
Fly Ash Concrete ◽  
Xrd Studies ◽  
One Year

AbstractThe setting and strength gaining process of PC concrete containing Class C high lime fly ash were related to the reaction products identified using XRD and SEM. Four fly ash concrete mixes (20, 30, 40, and 50 percent replacement of cement by fly ash) and similar paste mixes were compared to control mixes for curing periods up to one year. Setting time and early compressive strength were adversely affected by the addition of fly ash. Beyond one week all of the fly ash concrete mixes gained strength at a faster rate than the corresponding control mixes. XRD studies suggest that the retardation mechanism may be associated with the high levels of ettringite formed early in the hydration process and its conversion to monosulfoaluminate. A decrease in the level of calcium hydroxide, typical of pozzolanic activity, was not in evidence. SEM micrographs of fly ash spheres in concrete at the various stages of hydration reveal an intricate crystal framework. A simple heat of hydration test is presented which helps explain the strength gains observed.

scholarly journals Investigation on Hydration and Mechanical Properties of Mortar Containing Limestone Powder and Fly Ash Based on the Coupled Chemical–Thermal–Mechanical Method

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4387
Author(s):  
Wei Zhou ◽  
Wenxiang Tian ◽  
Tianqi Qi ◽  
Shuhua Liu ◽  
Chuqiao Feng ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Experimental Tests ◽  
Cementitious Materials ◽  
Hydration Process ◽  
Limestone Powder ◽  
Superior Performance ◽  
Early Age ◽  
Mechanical Method ◽  
Engineering Structures

The composited cementitious materials usually have superior performance; for example, using limestone powder (LP) and fly ash (FA) as the admixtures of cement in concrete/mortar is a popular way of improving the properties of concrete/mortar structures. In this work, we performed experimental tests to study the hydration process and pore distribution in mortar containing different ratios of LP and FA. Based on the results of mercury intrusion porosimetry (MIP), a numerical mortar model with random pore is built. The model can reflect the synergistic hydration interaction and filling effect caused by the admixtures of LP and FA. After analyzing the hydration process, the coupled chemical–thermal–mechanical method was used to simulate the characteristics of mortar containing LP and FA. The coupling model can simulate the “hump-type” hydration acceleration stage of the mortar at early age, which is specifically caused by the LP, proved in the experimental test. Additionally, the special, “hump-type” stage is important to enhance the early strength of the mortar. At different levels of admixture content, the random pore model and coupled method can predict the evolution process of the mechanical properties well, at early age and for long-term strength. Both experimental and numerical results suggest that the mortar containing admixtures of the proper ratio of LP to FA have good mechanical properties, which can be applied to engineering structures.

Limestone Powder- A New Type of Mineral Admixture for Dam Concrete

2014 ◽  
Vol 488-489 ◽  
pp. 614-619
Author(s):  
Xiang Zhi Kong ◽  
Gai Xin Chen ◽  
Tao Ji ◽  
Guo Jin Ji
Keyword(s):  
Fly Ash ◽  
Size Range ◽  
Mineral Admixture ◽  
Limestone Powder ◽  
Pore System ◽  
Early Hydration ◽  
Roller Compacted Concrete ◽  
New Type ◽  
Dam Concrete ◽  
Furnace Slag

Influences of limestone powder on the hydration progress of cement and the properties of dam concrete were studied in this paper. The results show that, as mineral admixture, limestone powder accelerates the cement early hydration and takes part in this hydration which produces the calcium monocarboaluminate hydrate, but, limestone powder doesnt have the pozzolanic activity. Limestone powder has an adverse impact on the pore system of hardened pastes, especially these pores size range from 3 nm to 107 nm. Fortunately, the pore system will be optimized by using some fly ash instead of part of limestone powder. Limestone powder, no matter used alone or blended with fly ash or ground blast furnace slag to form a double-doped material, can be used as mineral admixture for the dam concrete including conventional and roller-compacted concrete. Compared with fly ash, it increases concrete water content and improves the 7 days strength, but almost has no function on the 90 days strength.

scholarly journals Description of the concrete carbonation process with adjusted depth-resolved thermogravimetric analysis

2021 ◽  
Author(s):  
Nico Vogler ◽  
Philipp Drabetzki ◽  
Mathias Lindemann ◽  
Hans-Carsten Kühne
Keyword(s):  
Calcium Hydroxide ◽  
Bound Water ◽  
Reference Method ◽  
Microscopic Analysis ◽  
Limestone Powder ◽  
Gravimetric Analysis ◽  
Sample Material ◽  
Accelerated Carbonation ◽  
Temperature Range ◽  
Carbonation Process

AbstractThe thermal gravimetric analysis (TG) is a common method for the examination of the carbonation progress of cement-based materials. Unfortunately, the thermal properties of some components complicate the evaluation of TG results. Various hydrate phases, such as ettringite (AFt), C–S–H and AFm, decompose almost simultaneously in the temperature range up to 200 °C. Additionally, physically bound water is released in the same temperature range. In the temperature range between 450 °C and 600 °C, the decomposition of calcium hydroxide and amorphous or weakly bound carbonates takes place simultaneously. Carbonates, like calcite, from limestone powder or other additives may be already contained in the noncarbonated sample material. For this research, an attempt was made to minimise the influence of these effects. Therefore, differential curves from DTG results of noncarbonated areas and areas with various states of carbonation of the same sample material were calculated and evaluated. Concretes based on three different types of cement were produced and stored under accelerated carbonation conditions (1% CO2 in air). The required sample material was obtained by cutting slices from various depths of previously CO2-treated specimen and subsequent grinding. During the sample preparation, a special attention was paid that no additional carbonation processes took place. As reference method for the determination of the carbonation depth, the sprayed application of phenolphthalein solution was carried out. Microscopic analysis was examined to confirm the assumptions made previously. Furthermore, the observed effect of encapsulation of calcium hydroxide by carbonates caused by the accelerated carbonation conditions was examined more closely.

scholarly journals The Influence of Water Reducing Agents on Early Hydration Property of Ferrite Aluminate Cement Paste

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 731
Author(s):  
Chunlong Huang ◽  
Zirui Cheng ◽  
Jihui Zhao ◽  
Yiren Wang ◽  
Jie Pang
Keyword(s):  
Setting Time ◽  
Critical Role ◽  
Hydration Product ◽  
Reducing Agents ◽  
Reducing Agent ◽  
Hydration Process ◽  
Early Hydration ◽  
Cement Pastes ◽  
Hydration Rate ◽  
Aluminate Cement

The ferrite aluminate cement (FAC) could rapidly lose fluidity or workability due to its excessive hydration rate, and greatly reduce the construction performance. Chemical admixtures are commonly used to provide the workability of cement-based materials. In this study, to ensure required fluidity of FAC, chemically different water reducing agents are incorporated into the FAC pastes. The experiments are performed with aliphatic water reducing agent (AP), polycarboxylic acid water reducing agent (PC) and melamine water reducing agent (MA), respectively. Influence of the water reducing agents on fluidity, setting time, hydration process, hydration product and zeta potential of the fresh cement pastes is investigated. The results show that PC has a better dispersion capacity compared to AP and MA. Besides decreasing water dosage, PC also acts as a retarder, significantly increasing the setting times, delaying the hydration rate and leading to less ettringite in the hydration process of FAC particles. The water reducing agents molecules are adsorbed on the surface of positively charged minerals and hydration products, however, for PC, steric hindrance from the long side chain of PC plays a critical role in dispersing cement particles, whereas AP and MA acting through an electrostatic repulsion force.

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