Flash Setting Research Articles

Effect of granulated phosphorus slag on physical, mechanical and microstructural characteristics of Class F fly ash based geopolymer

Granulated phosphorus slag (GPS) is an industrial byproduct generated from the yellow phosphorus manufacturing process through the electric furnace method, which not only occupies enormous fields but also causes serious environmental issues. This study investigated the effect of GPS on physical, mechanical and microstructural characteristics of Class F fly ash (FFA) based geopolymer. Samples synthesized from FFA with different GPS content (0%, 10%, 20%, 30%, 40% and 50%) were produced by reacting with a mixture of NaOH and Na2SiO3 solution. Meanwhile, other variables including different NaOH concentrations (2.5 M, 5 M, 7.5 M and 10 M), various curing temperatures (ambient 20℃ and elevated 60℃) and curing times (3, 7, 14 and 28 days) were also considered. The setting time and compressive strength of geopolymer paste were measured, respectively. The results indicated that the GPS addition decreased the setting time but did not result in the flash setting of FFA based geopolymer paste. Besides, the incorporation of GPS increased the compressive strength of geopolymer samples. Increasing NaOH concentration and curing temperature were beneficial for the strength improvement. Scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analysis were utilized to identify the microstructure and phase composition of geopolymer samples. The test results showed that after the hydration reaction, the relatively high amount of CaO in the GPS generated calcium silicate hydrate (C-S-H) gel which coexisted with sodium aluminate silicate hydrate (N-A-S-H) gel and thus resulted in a denser and more homogeneous microstructure. This study confirmed the feasibility of utilizing GPS to partially replace FFA, which could not only improve the mechanical property of the derived geopolymer but also realize the synergy between granulated phosphorous slag recycling and geopolymer industry.

Impact of Drilling Fluid Contamination on Performance of Rock-Based Geopolymers

Summary Our objective is to present selected rheological and mechanical properties of rock-based geopolymers contaminated with different concentrations of drilling fluids. The possible flash setting and the maximum intake of drilling fluids before seeing a dramatic deterioration of the geopolymers are presented. Rock-based geopolymers designed for cementing conductor and surface casing were prepared and cured for up to 28 days at 22°C and atmospheric pressure. Water-based drilling fluids (WBDFs) and oil-based drilling fluids (OBDFs) were designed in accordance with the recommendations from the petroleum industry. The fluid samples were prepared, and their viscous behavior was characterized before and after hot-rolling. The geopolymeric slurries were mixed and then blended with the prepared drilling fluid volumes. The contaminated geopolymeric slurries were cured and tested at different time intervals. American Petroleum Institute (API) Class G neat cement was used as a reference. These samples were cured and contaminated with the same drilling fluids. The properties of contaminated geopolymer slurries were benchmarked with those of the contaminated Class G cement. The obtained mechanical properties showed that the rock-based geopolymers are more sensitive to WBDFs than to OBDFs. However, for contaminated Portland cement samples, the obtained results were opposite, and the contamination effect of OBDF on cement was more noticeable than WBDF. The impact of geopolymer contamination is a function of curing time. Although geopolymeric samples showed dramatic strength retrogression at the early time, strength buildup of the samples compensated for the impact of contamination.

Early performances of cement paste in the presence of triethanolamine: Rheology, setting and microstructural development

AbstractThe effect of triethanolamine (TEA) at various dosages on the early performance of cement paste was systematically evaluated through the techniques of rheological measurements, penetration tests, and ultrasonic pulse velocity. The correlation of early performance to the chemical hydration process was analyzed by calorimetry, zeta potential, in situ XRD, and pore solution analysis. It is found that the effect of TEA on the early performance of cement paste is strongly dependent on its dosage. With the TEA dosage below 0.1 wt%, the setting and microstructural development of cement paste are retarded. Meanwhile, the yield stress of fresh paste is decreased due to the increasing zeta potential of cement grains. The promoted formation of ettringite (AFt) and monosulfate (AFm) caused by TEA decreases the rheological retention ability. At dosages ≥0.2 wt%, the reaction of aluminate‐containing phases is greatly accelerated and a flash setting is observed. Besides, the importance of ferric phase on the reaction of cement with TEA is highlighted. At a low dosage, TEA prefers to accelerate the dissolution of tetracalcium aluminoferrite (C4AF) first and increases the [Fe] in the pore solution of cement paste. In cement without C4AF, the retardation of TEA on silicate phase hydration is significantly alleviated.

Effect of locally sourced Nigerian gypsum on the strength and microstructure of Portland cement mortar

The objective of this study was to investigate the suitability of Nigerian, sourced Gypsum for the manufacture of Portland cement. Gypsum samples were obtained from eighteen deposits across Nigeria. These were classified into five purity groups based on their calcium sulphate content.Foreign Gypsum, imported from Morocco, was used as control. Six cement samples where produced for each of the five Gypsum purity groups by grounding and blending cement clinker with 3%, 4%, 5%, 6% and 7% Gypsum content. The group 1 cement mix (having not more than 65% calcium sulphate content) has displayed flash set and could not be moulded and therefore not used for further analysis. Cement mortar prisms were produced for the groups 2, 3, 4 and 5 cement mixes, and subjected to flexural and compressive strength tests at 7, 14, 21 and 28 day curing periods. The cement mortar prisms were also subjected microstructure analysis at 7 and 28 days curing period. The spongy, gel and whitish colouration observed from the microstructure of the specimens indicated silicates enriched regions which have proven the strength increase from 7 to 28 day curing period. The optimum gypsum content of 5.5% was recommended. The results show that all but the class one gypsum with less than 65% purity content are suitable for cement manufacture.
 Keywords: Gypsum, clinker, mortar, microstructure, compressive strength, flexural strength

Influences of calcium sulfate bearing material and zinc oxide nanoparticle on hydration properties of white cement clinker

The present study investigates the influence of zinc oxide nanoparticles, gypsum, and combinations of them on hydration properties of white cement clinker. Gypsum optimization for the clinker was detected using highly purified gypsum. Compressive strength, setting time, and soundness of all mixes were examined. The results showed that the setting time of pure clinker (C) and clinker with ZnO (CZ) mixes yields flash set after few minutes from the preparation time. While the clinker with gypsum (CG) and clinker with combination from gypsum and ZnO (CGZ) mixes yields a recordable value for setting time. The optimum compressive strength of the (CZ) mix obtained from the mix with content (100% clinker + 0.7% ZnO) reaches 41.9, 55.8, and 63.9 MPa at 3, 7, and 28 days, respectively. The optimum compressive strength of (CGZ) mix achieved from the mix with content (97% clinker + 3% gypsum + 0.7% ZnO) reaches 53.0, 68.9, and 75 MPa at 3, 7, and 28 days, respectively. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectrometry (FTIR) of mortars showed that the absence of gypsum in the mixes retarded the hydration of C3S phase due to the rapid formation of calcium aluminate hydrate C-A-H. The optimum combination of gypsum and ZnO accelerates the hydration process of the C3S phase, reduces the formation of C-A-H and improves the strength.

Review of Sprayability of Wet Sprayed Concrete

Abstract Wet sprayed concrete quality is affected by more production factors than cast concrete, particularly due to the propulsion through the nozzle and the flash set caused by the set accelerator. Practitioners often use the term “sprayability” to describe these factors. We propose a definition of “sprayability” that relates the application to the final properties of the hardened sprayed concrete and review factors affecting it: concrete constituents, proportioning, and application mechanics. These factors affect the hardening and the structure of the hardened sprayed concrete – the porosity, permeability and durability. We consider improving sustainability through proportioning with increased share of supplementary cementitious materials, calculate the placed composition and focus on factors that affect water transport, and hence durability. Due to the spray application and flash-set, irregular compaction voids dominate the macro pore structure of sprayed concrete. Studies of permeability of sprayed concrete have shown that it is possible to obtain low permeabilities given adequate composition and curing. Presumably these samples have been well-cured, uncracked and with non-percolating macro voids. Given observations of cracks in sprayed concrete linings and the macro voids, important further studies will be on the effect of accelerator, compaction porosity and cracking on permeability.

Properties of fly ash geopolymer modified with red mud and silica fume: a comparative study

Alkali-activated geopolymer has emerged as a sustainable alternative to highly polluting conventional cement. The present paper investigates the activation of fly ash-based geopolymer paste modified by red mud and silica fume. Three geopolymer mixes are considered: (1) fly ash; (2) fly ash—red mud; and (3) fly ash—silica fume. Mass proportions of modifiers in the respected mixes varied by 0, 5%, 10%, 15%, 20%, and 25% of total binder. Heat curing (60 °C) provided for 24 h just after casting. Alkaline activator consists of sodium hydroxide and sodium silicate solutions. Workability results reveal that both red mud and silica fume triggered the reduction in workability with the later one had a greater impact. A flash set was obtained with the silica fume content of more than 15%. Both the modifiers cause a decrease in the setting time at ambient temperature, and silica fume proved to be more productive with the reduction of more than 65% of setting time. Mixes containing red mud exhibit slightly higher density. Water absorption of fly ash geopolymer increases with red mud. Compressive strength increases with the addition of modifiers, and geopolymer containing silica fume possesses the highest compressive strength among the three mixes considered. Compressive strength exhibited a linear correlation with molar ratios (Si/Al and Na/Si) of source materials. XRD and SEM methods showed that the geopolymerization reaction is affected by the red mud and silica fume. It is recommended that the flash set and setting time at higher contents of modifiers must be examined for the design of a modified geopolymer mix.

State of the art on geopolymer concrete

PurposeImportant differentiating attributes in the procedures used, the characteristic mineral composition of the binders, and the implications these have on the final long term stability and physico-mechanical performance of the concretes produced are identified and discussed, with the intent to improve transparency and clarity in the field of geopolymer concrete technologies.Design/methodology/approachThis state-of-the-art review covers the area of geopolymer concrete, a class of sustainable construction materials that use a variety of alternative powders in lieu of cement for composing concrete, most being a combination of industrial by-products and natural resources rich in specific required minerals. It explores extensively the available essential materials for geopolymer concrete and provides a deeper understanding of its underlying chemical mechanisms.FindingsThis is a state-of-the-art review introducing the essential characteristics of alternative powders used in geopolymer binders and the effectiveness these have on material performance.Practical implicationsWith the increase of need for alternative cementitious materials, identifying and understanding the critical material components and the effect they may have on the performance of the resulting mixes in fresh as well as hardened state become a critical requirement to for short- and long-term quality control (e.g. flash setting, efflorescence, etc.).Originality/valueThe topic explored is significant in the field of sustainable concrete technologies where there are several parallel but distinct material technologies being developed, such as geopolymer concrete and alkali-activated concrete. Behavioral aspects and results are not directly transferable between the two fields of cementitious materials development, and these differences are explored and detailed in the present study.

Performance Evaluation of Polycarboxylic Acid Dispersant for Oil Well Cementing

The conventional oil-well cement dispersant has the characteristics of poor dispersion at high temperature, poor compatibility with other additives, and environmental pollution during the production process. In this article, with ultra-early strong polyether monomer, acrylic acid, 2-acrylamine-2-methylpropyl sulfonic acid, sodium methacrylate as copolymer monomers, an environmentally friendly polycarboxylic acid dispersant, DRPC-1L, was prepared by the aqueous solution free-radical polymerization. The chemical composition and thermal stability of the synthetic copolymer were characterized by FTIR and TGA techniques. The evaluation results show that DRPC-1L has a wide temperature range (30~210 °C), good salt-resistance and dispersing effect. It can significantly improve the rheological performance of cement slurry, and it is well matched with oil-well cement additives such as fluid loss agent, retarder and so on. Moreover, it is beneficial to the mechanical strength development of set cement, especially the early compressive strength. It can also inhibit the abnormal gelation phenomenon of cement slurry, flash set, that occurs during high temperature thickening experiments, which plays an important role in enhancing the comprehensive performance of cement slurry. Consequently, the novel polycarboxylic acid dispersant has good application prospects in deep and ultra-deep wells cementing.

Oil well casing cement flash setting problem causes and identification strategy based on cheese model

This paper deals with oil well cementing flash setting problem definition, interpretation and localization via PABM (phenomenon analysis-based method) and Swiss cheese model investigation. Cementing is the most critical job throughout the well realization process; it presents the face of the well during production or abandonment. Within cement job some, problems come out and could lead to lose the well objectives, and it can be classified as cementing program’s awkward or operational hitches. This work is oriented toward operational stage, even if cement program and preparation seem in the rules of the art, the execution stage can interrupt the smooth running of cement job. Flash setting is one of the most critical problems that could be occurred, and it can be recognized by the prior increases in pressure to reach unpumpable stage. Identifying flash setting phenomenon and distinguishing them from other operational comportment stay hard task and present the heart of this work. Consequences could be varied from simple cement left inside casing to total free pipe of the annulus. PABM together with cheese model is proposed to be used for deep analysis of flash setting problems and points out the real causes, if they exist, rather than flash setting. The method proposed includes five steps, description of the operation, phenomenon, assumptions, cheese model and conclusion. The three first steps construct operation scrutiny, and the fourth step represents PABM. In this latter method, assumptions will pass through a selective process made from operation facts, and only the adequate assumption reaches the last layer of the model. Practical cases have been detailed to point out the merit of this method and distinguishing flash setting from other related cement problems.

Fresh and Hardened Properties of High Calcium Fly Ash-Based Geopolymer Matrix with High Dosage of Borax

Geopolymer is synthesized by mixing material rich in alumina and silica, such as fly ash, with a highly alkaline solution to form a hardened matrix. However, when using high calcium fly ash as a precursor, a flash set frequently occurs, i.e., the mixture hardens very rapidly before casting can be completed. The use of borax as an additive has been reported due to its potential to prolong the setting time. In this study, the use of a significantly higher dosage of borax is explored. The results show that the addition of borax up to 20% of fly ash, by mass, into the alkaline solution prolongs the setting time by up to 90 min. Conversely, the addition of higher amounts of borax tends to decrease the compressive strength of the geopolymer, whereas adding a small amount of calcium oxide into the mixture increases the strength marginally, especially when the borax content is small. However, the amount of calcium oxide should be limited because at higher content, the effectiveness of borax to prolong the setting time is reduced.

Influence of superplasticizers and retarders on the workability and strength of one-part alkali-activated fly ash/slag binders cured at room temperature

One-part alkali-activated fly ash/slag binders have been promoted as an environmentally friendlier alternative to Ordinary Portland Cement (OPC). However, its tendency towards flash setting and high sensitivity of the mixture’s strength to water content have been sources of major concern in the industry. This study investigates the effects of different w/b ratios, admixtures (such as superplasticizers and/or retarders) and the dosage of the selected admixture on the fresh and hardened properties of one-part alkali activated fly ash/slag based binders. To evaluate the fresh properties of binders, setting time and flowability tests were carried out. The compressive and flexural strength tests were conducted to determine the mechanical strength of the samples. The mineralogy and microstructure of the samples were studied using X-ray diffraction (XRD) and scanning electron microscope (SEM) in conjunction with energy dispersive spectroscopy (EDS) which was used to observe the elemental composition. Additionally, an optical microscope was also used to study the surficial physical properties of the hardened binders. The experimental results showed that an increase in w/b ratio led to an improvement in fresh properties of binder but significantly decreased the mechanical strength. A w/b ratio of 0.3 was deemed to be optimal in this study because at this ratio the hardened samples showed no surficial cracking and had enough compressive strength to be viable as a construction material. Test results also showed borax to be superior to all the other admixtures tested when both mechanical strength and workability are considered.

Suitability of alkali activated slag/fly ash (AA-GGBS/FA) concretes for chloride environments: Characterisation based on mix design and compliance testing

Ground granulated blast furnace slag (GGBS) and fly ash are two of the most common industrial by-products used as precursors in an alkali activated material (AAM). Alkali-activated systems with fly ash as the sole precursor often require elevated temperature curing, while if made with GGBS alone can lead to flash setting, low workability and high degree of drying shrinkage. This article presents data from a range of GGBS/Fly Ash blends designed to avoid elevated temperature curing whilst achieving desirable fresh properties. Further, the suitability of such blended concrete for their use in chloride environments is outlined with the help of diffusivity testing and binding assessment. The results show that while attractive engineering properties can be achieved, chloride ingress in the AA-GGBS/FA concretes studied here with ≥20% fly ash is moderate to high. Reduction in pH resulting from the long term exposure to chloride solution also affected the ability of the binder to chemically or physically binding chlorides.

Experimental methods to determine the feasibility of steel slags as supplementary cementitious materials

Limited applications for the large amounts of steel slags produced globally exist. In this study, the hydraulic and pozzolanic behavior of basic oxygen furnace slag (BOFS) and ladle furnace slag (LFS) are studied and contrasted with the behavior of ground granulated blast furnace slag (GGBFS). Pozzolanic test, isothermal calorimetry, thermogravimetric analysis, and compressive strength test are performed to determine the feasibility of these slags as supplementary cementitious materials (SCMs). The pozzolanic test is performed by measuring the heat release and calcium hydroxide consumption of slag-calcium hydroxide blends at 50 °C and pH 13.5. The other tests are performed on cementitious pastes with 20% slag replacement by mass at 23 °C and 50 °C. GGBFS shows the best performance among all slags in the tests, followed by BOFS, followed by LFS. It is suggested that BOFS and LFS should not be used as SCMs as-is. The poor performance of LFS is due to flash setting, likely caused due to the rapid reaction of C12A7, which causes hydration retardation and poor strength gain. The BOFS shows moderate performance as it has low hydraulic activity, likely explained by its low amorphous content and the presence of low amount of reactive crystalline phases. An important finding from this study is that in order to state whether materials could be used as SCMs or not, the combined use of pozzolanic test, isothermal calorimetry, and compressive strength test is more accurate than the use of only one test method. While the results obtained may here not be broadly generalizable to other materials due to variations in slag chemistry, the approach suggested may be generalizable to obtain insights into whether any powder may be used as SCM.

Properties of Steel Slag and Stainless Steel Slag as Cement Replacement Materials: A Comparative Study

To enhance the understanding about the utilization of steel slags as a cementitious material, we comparatively studied the chemical, mineralogical and morphological properties of two types of steel slag; basic-oxygen-furnace carbon slag (BOF C) and electric-arc-furnace stainless steel slag (EAF S). Moreover, we studied the standard consistency, setting time and the effect of the slag replacement ratios on the fluidity and compressive strength of blended cement mortar. The experimental results showed that BOF C had higher alkalinity, higher pH value and more hydraulic phases than EAF S. Both types of slag showed water reduction effect due to its high fineness. Neat BOF C paste showed flash set and acceleration in the initial setting time of blended cement especially at high slag proportions. However, EAF S prolonged the setting time of blended cement even at low slag proportions. The pH values for blended cement contained 50% BOF C or EAF S were lower than those of pure cement paste. Despite of slag type, compressive strength gradually decreased with increasing slags content. The strength of BOF C mortar was higher than that of EAF S mortar with the same replacement ratio for the same age. Slag activity index demonstrated that BOF C and EAF S conformed to the Chinese National Standard (GB/T 20491-2006) requirements for steel slag as grade one and grade two, respectively.

Characteristics of Lightning within Electrified Snowfall Events using Lightning Mapping Arrays.

This study examined 34 lightning flashes within four separate thundersnow events derived from lightning mapping arrays (LMAs) in northern Alabama, central Oklahoma, and Washington DC. The goals were to characterize the in-cloud component of each lightning flash, as well as the correspondence between the LMA observations and lightning data taken from national lightning networks like the National Lightning Detection Network (NLDN). Individual flashes were examined in detail to highlight several observations within the dataset. The study results demonstrated that the structures of these flashes were primarily normal polarity. The mean area encompassed by this set of flashes is 375 km2, with a maximum flash extent of 2300 km2, a minimum of 3 km2, and a median of 128 km2. An average of 2.29 NLDN flashes were recorded per LMA-derived lightning flash. A maximum of 11 NLDN flashes were recorded in association with a single LMA-derived flash on 10 January 2011. Additionally, seven of the 34 flashes in the study contain zero NLDN identified flashes. Eleven of the 34 flashes initiated from tall human-made objects (e.g., communication towers). In at least six lightning flashes, the NLDN detected a return stroke from the cloud back to the tower and not the initial upward leader. This study also discusses lightning's interaction with the human built environment and provides an example of lightning within heavy snowfall observed by GOES-16's Geostationary Lightning Mapper.

A Hot Downflowing Model Atmosphere for Umbral Flashes and the Physical Properties of Their Dark Fibrils

Abstract We perform non-LTE inversions in a large set of umbral flashes, including the dark fibrils visible within them, and in the quiescent umbra by using the inversion code NICOLE on a set of full Stokes high-resolution Ca ii λ8542 observations of a sunspot at disk center. We find that the dark structures have Stokes profiles that are distinct from those of the quiescent and flashed regions. They are best reproduced by atmospheres that are more similar to the flashed atmosphere in terms of velocities, even if with reduced amplitudes. We also find two sets of solutions that finely fit the flashed profiles: a set that is upflowing, featuring a transition region that is deeper than in the quiescent case and preceded by a slight dip in temperature, and a second solution with a hotter atmosphere in the chromosphere but featuring downflows close to the speed of sound at such heights. Such downflows may be related, or even dependent, on the presence of coronal loops, rooted in the umbra of sunspots, as is the case in the region analyzed. Similar loops have been recently observed to have supersonic downflows in the transition region and are consistent with the earlier “sunspot plumes,” which were invariably found to display strong downflows in sunspots. Finally, we find, on average, a magnetic field reduction in the flashed areas, suggesting that the shock pressure is moving field lines in the upper layers.

Nanosecond dynamics of destruction of the surface layer of a heterogeneous nanocrystalline solid (sandstone) under the friction

It has been found that the friction of a heterogeneous material, namely, sandstone, leads to the appearance of triboluminescence. The phenomenon of triboluminescence corresponds to luminescence of ≡Si–O free radicals and Fe3+ ions. These radicals and ions are formed as a result of the breaking of Si–O–Si bonds in nanocrystals of quartz and feldspar entering into the composition of the sandstone. The time dependence of the triboluminescence intensity represents a set of flashes, each having the duration of a few nanoseconds. It has been assumed that triboluminescence flashes correspond to the appearances of cracks in the material. Сrack opening is found to be approximately 180 nm. The size distribution of the cracks is exponential.

Petroleum sludge treatment and reuse for cement production as setting retarder

Petroleum sludge is a dangerous waste that needs to be treated to avoid any contamination of soil and groundwater due to its disposal. As an attempt to treat this waste, it has been incorporated into cement production as substitution for gypsum. As results, 5% of petroleum sludge has shown effective results and could play the same role of gypsum in delaying the flash setting of cement clinker.

5-Aminosalicylic acid inhibits inflammatory responses by suppressing JNK and p38 activity in murine macrophages

Context: 5-Aminosalicylic acid (5-ASA), as an anti-inflammatory drug, has been extensively used for the treatment of mild to moderate active ulcerative colitis (UC), but the possible mechanisms of action remain unclear.Objective: To investigate the effects of 5-ASA on the production of inflammatory mediators by murine macrophages stimulated with lipopolysaccharide (LPS), and determine the underlying pharmacological mechanism of action.Materials and methods: The levels of nitric oxide (NO) and interleukin-6 (IL-6) were measured by Varioskan Flash and IL-6 Enzyme-Linked Immunosorbent Assay sets. Real time quantitative polymerase chain reaction was used to determine the level of induced nitric oxide synthase (iNOS). The effects of 5-ASA on iNOS, the c-Jun N-terminal kinases (JNKs), p38 and nuclear factor (NF)-κB signaling pathways were examined using western blotting.Results: 5-ASA suppressed the production of NO and IL-6, and also decreased the expression of iNOS in LPS-induced RAW264.7 cells. 5-ASA inhibited the phosphorylation of JNKs and p38, but did not block NF-κB activation at all doses tested.Discussion and conclusion: The results indicated that the anti-inflammatory effect of 5-ASA was mainly regulated by the inhibition of the JNKs, p38 pathways rather than NF-κB pathway. Further research is required to clarify the detailed mechanism of the action.