Dry Curing Research Articles

Application of micro-crystalline cellulose as additive in Portland cement-based and alkali activated slag-fly ash mortar: Comparison of compressive strength, hydration and shrinkage

The research aims to examine the effects of micro-crystalline cellulose (MCC) as additive in Portland cement-based (OPC) and sodium hydroxide slag-fly ash blend (AAM) with the objective of mitigating shrinkage and improve mechanical and durability properties of constructions. MCC was dispersed using ultrasonication and added at dosages of 0.25%, 0.50% and 1% by weight of binder. The mentioned engineering properties of OPC-mortar and AAM-mortars were examined under three exposure conditions – sealed curing (SC), dry curing (DC, 30◦C/65% RH) and steam curing (STC, only for AAM). The experimental outcome suggests that addition of 1% MCC mitigates loss in strength and hydration of OPC-mortar when curing condition is changed from SC to DC, and offers similar strength as control at 28-day age. In comparison, 0.25% MCC dosage is found to be optimal for AAM, offering lower porosity and slight improvement (7 – 10%) in compressive strength at 28-day mark. Increase in MCC dosage to 1% drastically reduces compressive strength, which is attributed to noticeable retardation in fly ash dissolution in the presence of MCC and alkaline environment based on isothermal calorimetry. Addition of MCC has a substantial effect on shrinkage of OPC-mortar, evident from reduction in 7-day sealed shrinkage by 67%, 31% and 66% than control due to addition of 0.25%, 0.50% and 1% MCC respectively. In comparison, MCC eliminates shrinkage of AAM under sealed condition until 3-day and reduces total shrinkage by 8 – 36% at 7-day and 50-day age. Combination of STC and 1% MCC dosage is found to offer a substantial reduction in total shrinkage by 68% at 7-day and 23% at 50-day mark compared to control. The findings from the study suggest a promising potential of using MCC, which can be extracted from locally generated biomass wastes and textile wastes, as curing additive for OPC and alkali-activated based construction materials.

Experimental studies on strength and durability of alkali activated slag and coal bottom ash based geopolymer concrete

This thesis work describes the experimental evaluation of the durability and strength properties of nominally mixed conventional concrete of grade M35, Alkali Activated Slag Based Geopolymer Concrete. Research on Rapid Chloride Permeability Test (RCPT) durability properties has been conducted. Sodium hydroxide (NaOH) and sodium Chloride (NaCl) must be mixed in a 2.5:1 M ratio and at molarities of 12 and 16, respectively, in order to make alkali activators, with dry curing and open-air curing serving as distinct curing regimes. NaOH concentrations of 12 M and 16 M were used to make nine distinct mixes, one of which was designated as the control mix. Then, these mixtures were cured at room temperature in the open air. Prior to the testing day, they were maintained at room temperature after a 24-hour dry curing procedure at 90 °C in a hot air oven. Each of the nine mixes underwent split tensile and flexural strength and durability testing after 90 days. Compressive strength tests are conducted at 28, 56, and 90 days. The results show that tensile strength increases as NaOH solution concentration decreases, but compressive and flexural strength increase as NaOH solution concentration increases. However, it was discovered that the Geopolymer concrete made from Alkali Activated Slag and Coal Bottom Ash (CBA) did not perform well in tests of water fast chloride penetrability because surface cracking predominated. When compared to the results of the control mix, the Alkali Activated Slag and Coal Bottom Ash (CBA)-based geopolymer concrete mix shows a superior improvement in strength measures than standard concrete. At this time, it seems that making geopolymer concrete costs less than regular concrete.

Optimising the Performance of CO2-Cured Alkali-Activated Aluminosilicate Industrial By-Products as Precursors

Three industrial aluminosilicate wastes were studied as precursors to produce alkali-activated concrete: (i) electric arc furnace slag, (ii) municipal solid waste incineration bottom ashes, and (iii) waste glass rejects. These were characterized via X-ray diffraction and fluorescence, laser particle size distribution, thermogravimetric, and Fourier-transform infrared analyses. Distinctive combinations of anhydrous sodium hydroxide and sodium silicate solution were tried by varying the Na2O/binder ratio (8%, 10%, 12%, 14%) and SiO2/Na2O ratio (0, 0.5, 1.0, 1.5) to find the optimum solution for maximized mechanical performance. Specimens were produced and subjected to a three-step curing process: (1) 24 h thermal curing (70 °C), (2) followed by 21 days of dry curing in a climatic chamber (~21 °C, 65% RH), and (3) ending with a 7-day carbonation curing stage (5 ± 0.2% CO2; 65 ± 10% RH). Compressive and flexural strength tests were performed, to ascertain the mix with the best mechanical performance. The precursors showed reasonable bonding capabilities, thus suggesting some reactivity when alkali-activated due to the presence of amorphous phases. Mixes with slag and glass showed compressive strengths of almost 40 MPa. Most mixes required a higher Na2O/binder ratio for maximized performance, even though, contrary to expectations, the opposite was observed for the SiO2/Na2O ratio.

Production of biologically active non-woven textiles from recycled polyethylene terephthalate.

Recently, various studies have focused on the development of multifunctional non-woven polyethylene terephthalate (PT; polyester) textiles. Herein, we introduce multifunctional non-woven polyester fabrics by pad dry curing silver nitrate (AgNO3 ) and aniline monomer into plasma-pretreated non-woven PT textile. This creates a nanocomposite layer of silver nanoparticles (AgNPs) and polyaniline (PANi) on the fabric surface. In order to prepare a non-woven fibrous mat, we applied the melt-spinning technique on previously shredded recycled PT plastic waste. On the surface of the cloth, PANi was synthesized by REDOX polymerization of aniline. Due to the oxidative polymerization, the silver ions (Ag+ ) were converted to Ag0 NPs. PANi acted as a conductor while AgNPs inhibited the growth of microorganisms. Microwave-assisted curing with trimethoxyhexadecylsilane (TMHDS) gave PT textiles with superhydrophobic properties. The morphological studies were performed using Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDX). The stiffness and breathability of finished non-woven PT textile materials were analyzed to establish their comfort levels. Both of Escherichia coli and Staphylococcus aureus were used to test the efficacy of the AgNPs-treated textiles as antimicrobial materials. Moreover, the processed polyester textiles showed excellent electrical conductivity and great ultraviolet-ray blocking.

Properties of Calcined Oebelo Red Soil Modified Fly Ash based Geopolymer

Research on fly ash has developed rapidly in recent years, one of which is its use as an environmentally friendly geopolymer concrete material. This research study the effect of calcination temperature and duration of red soil to compressive strength and setting time of fly ash based geopolymer paste. The red soil calcination process was carried out with variations in temperature of 400°C, 600°C, and 800°C for 4 and 8 hours of calcination. The activator solution was prepared by mixing a solution of NaOH with a solution of Na2SiO3 with a 1:1 composition. Sample treatment was carried out in 2 types, with ambient curing type and dry curing type. From the results of this study, the fastest setting time and maximum compressive strength of geopolymer paste of 23.14 MPa achieved at 800°C red soil calcination at 8 hours, and dry curing.

The Strength of Reinforced Concrete Slabs of 30% Candlenut Shell Variation Using Destructive Testing Methods

The compressive strength of concrete is one of the parameters used to control the quality of concrete. Concrete compressive strength testing method which is considered the highest level of reliability is a destructive testing method using a compression testing equipment. Based on the case, a testing tool is needed to measure or determine the compressive strength of concrete known as the Universal Testing Machine (UTM). Experimental research is conducted with a scientific approach using several of variables. The purpose of this research is to get the compressive strength value of concrete slabs variation of 30% candlenut shells. From the test results using a UTM so that it can be obtained the quality of reinforced concrete. The research variable are the 28 days age of concrete and the curing methods (wet curing and dry curing). The number of specimens of reinforced concrete slabs is 4 pieces measuring 50cm x 25cm x 12cm. The results of the study are the compressive strength of concrete slabs 30% variation of candlenut shells using UTM shows that the strength of reinforced concrete slabs reaches 75 MPa in wet curing and 59 MPa in dry curing or equivalent to the quality of K400 to K500 concrete at 28 days. The results also show the compressive strength of concrete in wet curing is higher than in dry curing.

Optimizing the Mechanical Performance and Microstructure of Alkali-Activated Soda Residue-Slag Composite Cementing Materials by Various Curing Methods

Aiming to promote further the application of alkali-activated soda residue-ground granulated blast furnace slag (SR-GGBS) cementing materials, this study explored the optimal curing method for enhancing mechanical performance. The optimal curing method was determined based on the development of compressive strengths at different curing periods and microstructural examination by XRD, FTIR, SEM, and TG-DTG. The results show that the strength of cementing materials after room-temperature (RT) dry curing was the poorest, with the slow development of mechanical performance. The 7d and 28d compressive strengths were only 14.62 and 20.99 MPa, respectively. Compared with the values after RT dry curing, the samples’ 7d and 28d compressive strengths after RT water curing, standard curing, and RT sealed curing were enhanced by 16.35%/24.06%, 30.98%/23.77%, and 38.24%/37.97%, respectively. High-temperature (HT) curing can significantly improve the early strength of the prepared cementing materials. Curing at 60 °C for 12 h was the optimal HT curing method. Curing at 60 °C for 12 h enhanced the 3d strength by 100.84% compared with standard curing. This is because HT curing promoted the decomposition and aggregation of GGBS, and more C-A-S-H gel and crystal hydration products, including ettringite and calcium chloroaluminate hydrate, were produced and filled the inner pores, thereby enhancing both the overall compactness and mechanical performance. However, curing at too high temperatures for too long can reduce the material’s overall mechanical performance. After excess HT curing, many shrinkage cracks were produced in the sample. Different thermal expansion coefficients of different materials led to a decline in strength. The present study can provide a theoretical foundation for extensive engineering applications of alkali-activated SR-GGBS composite cementing materials.

Studies on High Performance Concrete Using Mineral Admixtures

Abstract: High performance concrete is made using byproducts called cement replacement materials. Comparatively little information has been published regarding the results of different Effects of mineral admixtures on concrete's microstructural and team performance characteristics under various curing regimes. Additionally, it is unclear how concrete's strength relates to its conductivity and porous structure. Workability of the new concrete as well as engineering characteristics like cube and revised cube compressive strength and flexural strength were among the properties examined. The findings demonstrate that lanaba dry curing makes concretes weaker, more porous, with a increased pore size, and more permeable. It was discovered that tiny amounts of silica fume can make up for the reduction early in life compressive strength caused by the insertion of bagasse ash from sugar cane. With increasing concentrations of sugar cane bagasse ash or slag in the mixtures, the microstructural and engineering characteristics and concrete's capacity to breathe that contain them they seem to be more vulnerable to inadequate than concrete cubes for curing.

Performance and microstructure development of lime – calcined fluvial sediment binders under different curing conditions

Fluvial sediments need to be periodically dredged from waterways. At the same time, the building sector has to find high-volume alternatives to the extraction of non-renewable mineral resources. In this context, recent research has shown the benefit of reusing calcined sediments as supplementary cementitious materials. On a different note, this study examines the hydration and performance of blends of calcined fluvial sediment with low amounts (10 to 30 wt%) of hydrated lime with the aim of keeping the carbon footprint of the binder the lowest as possible. The effect of different curing conditions (moist curing at 20 °C or 50 °C and dry curing at 65%RH) is studied on compressive strength, reaction kinetics (fixed lime by TGA and heat of hydration), reaction products (XRD), microstructure (SEM) and porosity (MIP). The outcomes of the study revealed that heat curing for 3 days and 10 wt% of lime results in satisfactory strength development for the design of bio-based concretes (compressive strength of 9 MPa). Furthermore, the highest compressive strength of 17.5 MPa was achieved at 110 days at 20 °C for the mix with 20 wt% of lime. The amount of unreacted lime was found to be the highest for the mix including 30 wt% of lime for which the degree of reaction of lime at 90 days was around 0.7 for both curing temperatures. Under dry curing, a large part of the initially available lime was carbonated and some reaction products underwent carbonation leading to very low strength by 110 days.

Formation of heterocyclic aromatic amines in grilled pork depending on the pre-thermal treatment method

Electric grilled pork pretreated using four methods was analyzed for heterocyclic aromatic amines: 2-amino-3,8-dimethylimidazo [4,5-f] quinoxaline (MeIQx) and 2-amino-1-methyl-6-phenylimidazo [4,5-b] pyridine (PhIP). It was found that pre-thermal treatment of pork led to both a decrease and an increase in the content of heterocyclic aromatic amines in grilled steaks. In contrast to the control sample, the sample pretreated with an oil-based marinade exhibited a 3.2-fold decrease in the amount of MeIQx and 4.82-fold decrease in the amount of PhIP. The sample pretreated with a water-based marinade exhibited a 1.75-fold decrease in the amount of PhIP and a 3.81-fold increase in the amount of MeIQx. The sample pretreated with a dry curing mixture with red hot pepper exhibited a 3.5-fold increase in the amount of MeIQx and a 2.44-fold increase in the amount of PhIP. The sample pretreated with a dry curing mixture with paprika showed a 8.21-fold increase in the amount of MeIQx and a 3.65-fold increase in the amount of PhIP compared to the control sample. The study has shown that pretreatment of meat leads to both an increase and a decrease in the amount of heterocyclic aromatic amines formed during high-temperature thermal treatment depending on the non-meat ingredients used.

Differences in Fatty Acid Profile and Physical-Chemical Composition of Slavonska slanina-Dry Cured Smoked Bacon Produced from Black Slavonian Pig and Modern Pigs.

Simple SummaryResearch on the products of local pig breeds is quite challenging as the populations are small, breeders are less educated and it is often difficult to design systematic research in various and usually different breeding conditions, compared to commercial breeds. In this study, we have analysed dry cured bacons, produced from the local Black Slavonian and modern breeds on the small home-made scale, and compared their physico-chemical properties and fatty acid profiles. Results have showed significant differences in chemical composition and fatty acid profiles between analysed pig breeds.The objective of this study was to compare the psysico-chemical composition and fatty acid (FFA) profile of traditional dry cured bacon Slavonska slanina, produced from the authentic Black Slavonian Pig (BP) and modern pigs (MP), using traditional homemade principles. The samples of Slavonska slanina produced from BP had a significantly (p < 0.05) higher fat content (78.32%) than the samples produced from MP (46.47%), while the samples produced from MP showed significantly higher (p < 0.05) protein and moisture content. The samples produced from BP also showed lower aw and salt content but higher pH. Determination of fatty acid composition was performed at the end of the production process. The composition of fatty acids with respect to the groups of saturated (SFA), monounsaturated (MUFA) and polyunsaturated (PUFA) fatty acids was determined, as well as the ratios n-6/n-3 and PUFA/SFA. The results of fatty acid composition determination of Slavonska slanina produced from BP and MP show that oleic acid (C18: 1n9) is the most dominant fatty acid from the MUFA group (47.02 and 46.25%), the most common SFA acid was palmitic acid (C16: 0) (23.44 and 24.96%), and PUFA linoleic acid (C18: 2n-6c) (10.76 and 9.74%). The genotype had a significant (p < 0.05) effect on the SFA and USFA composition of Slavonska slanina. The ratios PUFA/SFA (0.34–0.28) and n-6/n-3 (31.84–27.34) for samples of Slavonska slanina produced from BP and MP are in concordance with previously published data for different dry cured meat products, and do not comply with the nutritionally recommended values of international health organizations (PUFA/SFA > 0.4 and n-6/n-3 < 4).

Study on the effect of WER and EVA on the performance and microstructure of cement mortars for a prefabricated residential floor

In this study, cement mortars were modified with ethylene-co-vinyl acetate (EVA) powder and water-based epoxy resin (WER) emulsion. This study aimed to investigate the effect of the content of the two polymers on the mechanical properties, abrasion resistance, and toughness of the mortar and to relate these properties to the microstructure of the mortar. We combined IPP(a combination of Stereo Light Microscopy and Image-Pro Plus image processing software) and the mercury intrusion porosimetry (MIP) to analyze the microscopic pore structure of polymer modified mortars. The microstructure of polymer modified mortars was studied by scanning electron microscopy (SEM). The results show that the use of alternating wet and dry curing regimes helps to improve the toughness of the modified mortar. Under this curing regime, the maximum flexural strength of the polymer modified mortar was 14.32 MPa and the maximum compressive strength was 90.52 MPa. The addition of polymer significantly improved the abrasion and impact resistance of the cement mortar, with a 28% reduction in abrasion volume from 116 mm3 to 83 mm3 and a 36% increase in impact strength from 13.92 J/cm2 to 18.97 J/cm2. Both polymers have the effect of filling capillary pores in the mortar, but there is a difference in the effect on large-size pores at high dosing levels. This work contributes to an in-depth understanding of the role of polymers in improving the performance of cement mortars, which enables rational development of polymer modified cementitious materials for prefabricated residential floors.

An Insight into the Effect of Rice Straw Biochar on Compressive Strength and Thermal Conductivity of Cement

It is well known that is very important to improve the quality of cement material concerning its compressive strength and thermal conductivity, which may reduce its quantity of usage and improve the heat maintenance of a structure compared with the traditional cement. In order to improve the properties of cement and other building materials, the test pieces were prepared by incorporating rice straw biochar with different pyrolysis temperatures into cement paste, and the compressive strength and thermal conductivity were tested after curing under both wet and dry conditions. The results showed that with the increase of biochar incorporation, the strength and thermal conductivity of the test blocks were decreased, but the thermal insulation performance of them was increased, and the quality and density of the test block were reduced. Under the condition of wet curing, the strength of the test pieces enhanced greatly with the dosage of 1% and 5%. When the dosage was 1%, the strength of the wet curing test block was the highest, which was increased by 51.06% compared with the blank control. The block strength increased by 14.98%; the thermal conductivity of the test piece incorporating biochar was reduced, and the test piece with 10% of the dry curing showed better thermal insulation performance, and the thermal conductivity was reduced by 39.21%. It can be seen that the addition of biochar improves the strength of the test block and optimizes the thermal insulation performance of the cement.

Utilization of biomass-based by-product lignin to suppress moisture loss-induced shrinkage of silty soil

The global stockpiles of by-product lignin are increasing rapidly with the growing demand on wood-based industry and biomass energy, creating a potential threat to environmental safety without proper disposal. The presented study aimed to evaluate the feasibility of utilizing biomass-based by-product lignin to suppress the shrinkage of silt expected as filling material in engineering construction. A series of laboratory experiments were conducted to investigate the variations in geometry size, mass loss Δm, moisture content w, and unconfined compressive strength qu of the treated samples exposed to the artificial dry condition. The effects of additive dosage and curing time on shrinkage behaviors of lignin treated silt were analyzed. The roles of matric suction on qu and soil microstructure were discussed to understand the mechanism leading to the soil shrinkage. The test results demonstrated that the addition of lignin effectively suppressed shrinkage of compacted silt subjected to dry curing. Both linear shrinkage rate es and volumetric shrinkage rate ev increased with an increase in lignin dosage, indicating excessive addition of lignin produced a negative impact on the shrinkage resistance. The values of es and ev of lignin treated samples were controlled within 1.0% and 3.0%, respectively. As compared to quicklime, lignin exhibited slightly inferior performance of suppressing shrinkage, while it promoted the water-holding capacity of the treated silt. The matric suction resulted from moisture loss was beneficial for strength improvement and also accelerated the process of soil shrinkage. The shrinkage characteristics of lignin treated silt mainly depended on the combined functions of lignin cementation and matric suction. Additional research is recommended to quantitatively evaluate the matric suction variation of lignin treated soils in dry environment. The outcomes of this study are invaluable in facilitating sustainable soil treatment in engineering construction and providing a viable answer to the cleaner production of biomass-based business.

Behaviour of Listeria monocytogenes and Natural Microflora during the Manufacture of Riojano Chorizo (Spanish Dry Cured Sausage).

Riojano chorizo is a dry cured sausage manufactured with traditional technologies without adding starter cultures at low temperatures. Its characteristics differ from other types of chorizo since sugars and nitrites are no added and processing temperatures are low- This work evaluates the behaviour of Listeria monocytogenes during the processing of inoculated Riojano chorizo as well as the natural microflora that can play a technological role or be of interest as indicators. The sausage mixture was inoculated with a cocktail of three selected strains of L. monocytogenes (CECT 932, CECT 934 and CECT 4032) (4 log10 CFU/g) and after processed following the traditional production method. Samples were taken before inoculation, after inoculation, after stuffing (day 0) and on days 6, 13, 21 and 28 of processing. L. monocytogenes, mesophiles, Micrococcaceae, lactic acid bacteria, Enterobacteriaceae, S. aureus, sulfite-reducing clostridia and molds and yeast counts were evaluated. Furthermore, pH, water activity and humidity were determined. No growth of L mocytogenes was observed during the first 6 days, when the temperature of processing was 4 °C. The low temperature in the initial stages was a relevant hurdle to control L. monocytoegenes growth. A significant decrease (p ≤ 0.05) in L. monocytogenes counts was observed on day 13 compared to the initial counts. During drying (days 6 to 21) a reduction in this pathogen of 1.28 log CFU/g was observed. The low water activity below 0.92 on day 13 and 0.86 on day 21 seems to be critical for the reduction of L. monocytogenes.

Chemical Characteristics of Croatian Traditional Istarski pršut (PDO) Produced from Two Different Pig Genotypes

Chemical characteristics of raw and processed Istarski pršut (PDO) produced from two different pig genotypes were studied with special emphasis on amino and fatty acid composition and factors of lipid stability. Raw hams of Large White (LW)xLandrace (L), and (LWxL)xDuroc (D) pig genotypes were used in the study (20 hams of each genotype). All left raw hams from each carcass were processed in accordance with the PDO specification of Istarski pršut, and other half (the right ones) of LWxL)xD genotype were used for analyses of raw hams (fresh muscles). Istarski pršut was evaluated on the basis of the chemical parameters of the raw and matured lean ham. The process of dry curing significantly influenced the chemical properties of Istarski pršut. Despite the higher content of intramuscular fat and polyunsaturated fatty acids, the fat of (LWxL)xD ham was much more resistant to hydrolysis and oxidation, suggesting that fatty acid profile and other factors, also play a significant role. Significant differences between pig genotypes in the amino acid and fatty acid profiles were found. The analyzed Istarski pršut may be distinguished by prints of multivariate chemometric statistical analysis, based on their amino acid and fatty acid compositions.

Performance-Based Approach for Deciding the Age of New Concrete for Thin Epoxy Overlay Application

A thin epoxy overlay application is a capital preventive maintenance activity. Epoxy overlays reduce the rate of chloride ion ingress and extend bridge deck service life. Highway agency policies and manufacturer specifications require maintaining a 28-day curing period (7-day wet and 21-day dry curing) before the application of an epoxy overlay on bridge decks requiring new concrete for patches and repairs. Consequently, the contractors wait for 28 days to apply an epoxy overlay. Delaying application time increases project completion time and the cost of construction and mobility. The suitability of new concrete to receive epoxy overlays and the performance of overlays depend on several parameters including concrete strength, moisture, and tendency to crack. Such parameters depend on concrete mixture ingredients and wet and dry curing periods. This paper presents a performance-based procedure for evaluating the possibility of reducing the 28-day waiting period for a thin epoxy overlay application on new concrete. An experimental program was developed and executed to evaluate the impact of epoxy overlay application parameters and overlay performance using a tensile bond pull-off strength test. The results support developing a performance-based procedure for deciding on the suitable age of new concrete to receive a thin epoxy overlay. The pull-off bond strength of epoxy overlays applied at 7, 14, and 21 days, following a 7-day moist curing, shows the possibility of applying an epoxy overlay before the end of the 28-day curing period stipulated in the current specifications.

Influence of drying on frost resistance of mortar using a nitrite corrosion inhibitor and paraffin waterproofing agent

The frost resistance of cement-based materials can be improved, by using the admixtures such as nitrite corrosion inhibitor (NCI) and paraffin waterproofing agent (PWA). In this work, we studied the influence of water curing and dry curing on frost resistance of mortars when these admixtures are added alone or in combination. Here, the cross sections of mortar samples were observed using the microscope equipped with a charge coupled device (CCD) camera and the pore structure was measured using mercury intrusion porosimetry. The results show that the frost resistance is similar to that of the reference mortars regardless of the addition amount, for the water-cement ratio W/C = 35%, but the frost resistance decreases regardless of the addition amount, for W/C = 55% when NCI is added alone. It is confirmed that the NCI may produce nitrite-type hydrocalumite and decreases frost resistance with the coarsening of pores. Furthermore, the PWA improves frost resistance by suppressing the effect of frost damage of hydrophobic compounds. This improvement is lessened when both admixtures are added in combination. This study advances understanding of the mechanism of suppressing frost damage by hydrophobic compounds.

Effect of curing time on thermal response characterization of carbon-nano cementitious composites

Introducing small amounts of multi-walled carbon nanotubes (MWCNTs) into cement-based materials changes the thermal and electrical characteristics of the composites. The heat generation of cement materials can be enhanced by incorporating MWCNTs. The thermal response of cement composites incorporating MWCNTs under dry curing conditions was experimentally investigated by varying the curing time and MWCNT concentrations of the composite. The temperature change in each specimen was measured by connecting the electrode to the power supply and supplying a constant voltage. The heat generation of the MWCNT cementitious composite increased with the number of curing days. In addition, the heat generation of the composite increased in a quadratic form with increasing MWCNT concentration. The electrical resistance of the composite depended on the progress of the hydration reaction. In the case of cementitious composites containing relatively high concentrations of MWCNTs, the electrical resistance decreased as the number of curing days increased.

Effect of GGBS and curing conditions on strength and microstructure properties of oil well cement slurry

The addition of any supplementary cementitious materials has a significant influence on cement paste properties and its microstructure. In this paper, the effects of micro-fine Ground Granulated Blast Furnace Slag (GGBS) on the properties Oil Well Cement (OWC) slurry are investigated. The class G cement is replaced in a varying percentage (30–70%) with GGBS at intervals of 10%. Further, the influence of different curing conditions (i.e., dry curing, moist curing, curing at 60 °C, curing at 110 °C) on the compressive strength of blended cement with GGBS are also studied. The microstructure analysis of blended cement with GGBS is investigated using isothermal calorimetry, X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), and Mercury Intrusion Porosity (MIP). The results show that the compressive strength of blended cement with 40 % GGBS have significantly increased and more than that of unblended cement. Further, micro-fine GGBS has influence on the emission of hydration heat due to pozzolanic reaction. The heat of hydration of blended cement is decreased significantly with partial replacement of cement with GGBS. The most significant finding in this study is that the permeability of blended cement paste with 40 % GGBS is decreased by 51 % of that of unblended cement, which is very important because it is one of the main factors affecting the gas migration in the wellbore.