Increasing Curing Temperature Research Articles

Efflorescence of fly ash-based geopolymer mortars under quasinatural conditions: the relationship between curing temperature, ion transport, and compressive strength

This investigation reports the effect of curing temperatures ranging from 20 °C to 80 °C on the efflorescence of fly ash-based geopolymer mortars under quasinatural conditions. The microstructures of the geopolymers before and after efflorescence were characterized by SEM and MIP, respectively. These characterizations are adopted to further explain the change in compressive strength. The micromorphology and phase assemblage of the efflorescence products were identified by SEMEDS and XRD, respectively, indicating that the significant ions involved in the efflorescence include Ca2+, Na+, and CO32-; then, the concentrations of those ions in the leachate were detected by ICP, AAS, and acidbase neutralization titration, respectively. The results show that low curing temperatures (≤ 50 °C) promote the diffusion of ions into the leachate, while high curing temperatures (> 50 °C) contribute to the transportation of ions towards the drying part for the formation of hollow structured Na2CO3·7H2O. Although the increase in the compressive strength of the geopolymers resulting from efflorescence decreased with increasing curing temperature, the 50 °C-cured geopolymer exhibited the highest compressive strength during efflorescence. This study provides a reference for mitigating efflorescence and improving practicability in the hydraulic engineering of geopolymers.

Effects of silica fume and rice husk ash contents on engineering properties and high-temperature resistance of slag-based prepacked geopolymers

Geopolymer slurries can be favored to achieve a sustainable approach in prepacked aggregate concretes. This study presented here investigated experimentally the effect of silica fume (SF) and rice husk ash (RHA) on the high-temperature resistance of slag-based sustainable prepacked geopolymers. In the production of prepacked aggregate geopolymers (PAGs), ground granulated blast furnace slag (GGBFS) was utilized as the main aluminosilicate-rich precursor material, and SF and RHA were replaced with GGBFS in various contents including 7.5% and 15%. The physical, mechanical and microstructural properties of specimens cured at 35°C and 70°C for 8 hours were determined comparatively. Residual compressive strength and mass loss of mixtures exposed to elevated temperatures (150°C, 300°C, and 600°C) were determined to observe high-temperature effects. The results revealed that the properties of PAGs were affected considerably by curing temperature and precursor type. The maximum oven-dry density of 2244 kg/m3 with RHA content of 7.5% was obtained at 70˚C curing temperature. Specimens produced with RHA tended to absorb more water under both heat curing conditions and the highest water absorption of 10.2% with RHA content of 7.5% was obtained at 35˚C curing temperature. The compressive strength of PAGs varied between 13.7 and 28.10 MPa, and flexural strengths varied between 1.48 and 2.74 MPa. Increasing curing temperature improved the strength properties of PAGs, and in general, the 8-hour compressive and flexural strength values of SF samples were relatively higher. The application of elevated temperature to the PAG mixtures caused a significant reduction in both compressive strength and mass loss. Among the specimens cured at 35°C, the specimens with RHA showed relatively better high-temperature performance in terms of compressive strength, while the specimens with SF cured at 70°C showed better performance. PAG specimens produced with RHA showed the best high-temperature performance against mass loss. According to the results obtained in the given study, these recycled wastes could be used to improve the physico-mechanical properties and high-temperature performance of slag-based PAGs.

Pilot Study Investigating Effects of Changing Process Variables on Elastic and Energy-Absorbing Characteristics in Polyurethane/Agglomerated Cork Mix for Use in Micro-Transport Helmet.

This pilot investigation identifies the influence that changing the process variables of curing pressure, curing temperature, and mix ratio of a polyurethane/agglomerated cork matrix has on the mechanical properties of energy absorption, Young's modulus of elasticity, and spring stiffness in safety helmets intended for micro-transport riders. The results are compared to expanded polystyrene, a material commonly used in micro-transport helmets. Mechanical testing of the various samples found that, over the range tested, curing pressure had no effect on any of the mechanical properties, while increasing amounts of resin caused a stiffer structure, and increasing curing temperature led to increased energy absorption. Consistent with the elastic modulus findings, all polyurethane/agglomerated cork test samples demonstrated higher median levels of spring stiffness, ranging from 7.1% to 61.9% greater than those found for expanded polystyrene. The sample mixed at a 1.5:1 binder/cork ratio and cured at 40 °C displayed the closest spring stiffness to EPS. While the mechanical properties of the eco-friendly polyurethane/agglomerated cork matrix did not match those of expanded polystyrene, the difference in performance found in this study is promising. Further investigation into process variables could characterise this more ecologically based matrix with equivalent energy-absorbing and structural characteristics, making it equivalent to currently used expanded polystyrene and suitable for use in micro-transport helmets.

Mechanical properties of multi-recycled coarse aggregate concrete, with particular emphasis on experimental and numerical assessment of shrinkage at different curing temperatures

This study investigates the behaviour of concrete manufactured with recycled coarse aggregate (RCA) derived from multiple recycling cycles, with a particular emphasis on experimental and numerical assessment of shrinkage at different curing temperatures (20, 40, and 60 °C). Four types of concretes have been produced: a natural aggregate concrete (NAC) with 100 % natural coarse aggregate (NCA) and three generations of recycled aggregate concrete (RAC) where NCA is replaced by RCA with volume percentages of 50 % and 100 % in each generation. Moreover, silica fume is used to improve the mechanical performance of the third-generation recycled concrete with 100 % RCA. In addition, the total shrinkage was predicted by combining the maturity method with finite-element analysis (FEA), using ANSYS© software. The results revealed that the multi-recycling and the replacement ratio of RCA have a detrimental impact on the mechanical properties. The total shrinkage increases considerably with both increasing curing temperature and increasing RCA replacement ratios in each generation. Furthermore, silica fume has a beneficial effect on the mechanical performance of the multi-recycled concrete; nevertheless, it causes an increase in the total shrinkage. Finally, the comparison between the experimental and numerical data shows that the FEA model, using the maturity method and two-phase serial model, can yield an accurate prediction of the total shrinkage of multi-recycled concrete.

Effect of microscale C–S–H on the properties of Portland cement and hydration kinetics analysis at different curing temperatures

Microscale calcium–silicate–hydrate (C–S–H) is easily accessible and readily storable, enabling a cleaner production process of cement-waste grinding and simple chemical synthesis technology. However, the temperature effects of microscale C–S–H require further exploration. In this study, we evaluated the impact of microscale C–S–H admixture on the properties of Portland cement at different curing temperatures. Microscale C–S–H can not only increase the early strength of cement pastes, but also achieve high strength in the long term. Adding microscale C–S–H to cement can effectively reduce the apparent activation energy Ea of hydration products and accelerate the reaction of C3S and C2S with water and form more hydration products. At a curing temperature of 10 °C, the microscale C–S–H increased the 1 d compressive strength by 70.0% and shortened the hydration induction period by 1.2 h. Microscale C–S–H also increased the 12 h hydration degree by 38.1%. Microscale C–S–H promoted the formation of CH and xonotlite-like C–S–H and changed the composition of hydrates, although the effects diminished with increasing curing temperature. This paper offers theoretical and fundamental data on the usage of microscale C–S–H as an admixture in cement-based materials.

Utilizing a multi‐layer structure to regulate the thermal conductivity of an advanced BN + EP composite insulation material: Effects of content, number of layers, and curing temperature on composites

AbstractBy blending materials such as boron nitride nanosheets (BNNSs), S‐BN and EP, hot pressing is used to realize the layered distribution of BNNSs and S‐BN fillers in the composite material, thereby forming a composite material with a sandwich structure, a horizontal and vertical heat conduction network, and improving performance of composite materials. In this paper, in order to explore the regulation of the influence of the change of objective factor variables on the thermal conductivity and electrical insulation properties of composite materials, BNNSs and S‐BN are used as the thermally conductive fillers of each layer, and EP is used as the matrix to realize the preparation of multilayer composites by high temperature and hot pressing. By changing the content of S‐BN filler in the middle layer, the number of layers of the composite material and the curing temperature of the composite material, the effects of the changes of the three objective factors on the microstructure, thermal conductivity, variable temperature conductance, dielectric, breakdown, DSC and infrared thermal imaging of composite materials are explored respectively. The results show that the multilayer structure ensures good bonding. As the content, number of layers and curing temperature increase, the thermal conductivity gradually raises to 2.64 W/(m·K), which is also proved by DSC and infrared thermal imaging. Composite materials also ensure considerable breakdown strength, control the preparation cost, reduce the preparation difficulty and expand the practicability of thermal insulation materials in the thermal conductivity field.Highlights Form a composite material with a sandwich structure, a horizontal and vertical heat conduction network. By changing three objective factors on the microstructure, Properties of composite materials are explored respectively. The thermal conductivity gradually raises to 2.64 W/(m·K). Composite materials also ensure considerable breakdown strength (insulation), control the preparation cost. Expand the practicability of thermal insulation materials in the thermal conductivity field.

Energy evolution and mechanical properties of modified magnesium slag-based backfill materials at different curing temperatures

To study the mechanical properties and failure characteristics of all-solid waste cementitious materials prepared in the intense geothermal environment of deep mines. Uniaxial compression, acoustic emission (AE), SEM and other tests were adopted to characterize the energy and deformation failure of backfill materials from different temperatures (20 °C, 30 °C, 40 °C). The results show that the temperature has a promoting effect on the development of modified magnesium slag-fly ash cemented paste backfill (MFPB) strength. The elastic strain energy and the dissipated energy corresponding to the peak stress increase as the curing temperature increases. The high frequency phase of the energy scatter plot is accompanied by a rapid increase in the cumulative ringing count and cumulative energy. Tensile cracks increase with the increase of curing temperature. The temperature effectively promotes the hydration process of MFPB. The decrease of strength in the later stage of curing temperature 40 °C is due to the harmful thermal stress within the backfill. The results provide theoretical guidance for the practical application of MFPB.

Mechanical properties under triaxial compression of coal gangue-fly ash cemented backfill after cured at different temperatures

The triaxial mechanical properties of cemented backfill are the key indicators that affect the stability of cemented backfill in underground mining areas, and the high temperature environment in mines has become one of the main factors affecting the mechanical properties of cemented backfill. Understanding the triaxial mechanical properties of cemented backfill in high temperature environments is crucial for the stability of cemented backfill in mining areas. To investigate the effect of temperature on the mechanical characteristics of cemented backfill under triaxial compression, triaxial compression experiments were done on coal gangue-fly ash cemented backfill that had been cured at three temperatures (20 °C, 35 °C, and 50 °C). The deviatoric stress-strain curve of cemented backfill under triaxial compression was produced, its deformation parameters, dilatancy, and failure characteristics were investigated, and a more appropriate strength criteria was proposed. The research results indicate that, peak strength and dilatancy stress of cemented backfill under the same confining pressure decrease first and then increase as the curing temperature increases. The failure patterns of cemented backfill under triaxial compression will exhibit layered splitting failure except tension and shear failure since the curing temperature has increased. By comparing it with several other criteria, the Mogi-Coulomb strength criteria was found to be a good reflection of the failure strength properties of cemented backfill cured at different temperatures under triaxial compression. With curing temperature rises, internal friction angle of cemented backfill steadily lowers, while the cohesion first decreases and subsequently increases. The alteration in cohesion is consistent with the peak strength change rule, illustrating that the primary factor influencing peak strength of cemented backfill is cohesion. This study provides a good theoretical reference value for guiding the design of deep mine filling and optimizing the mixture ratio of cemented backfill.

Effects of Curing Conditions on Splitting Tensile Behavior and Microstructure of Cemented Aeolian Sand Reinforced with Polypropylene Fiber.

Aeolian sand is widely distributed in the Takramagan Desert, Xinjiang, China, which cannot be directly used as railway subgrade filling. It is beneficial for environmental protection to use fiber and cement-reinforced aeolian sand as railway subgrade filling. The present work is to explore the enhancement of tensile strength in cemented aeolian sand via the incorporation of polypropylene fibers under conditions of elevated temperature and drying curing. The purpose Is to delve into the examination of the temperature's impact on not only the mechanical attributes but also the microstructure of cemented aeolian sand reinforced with polypropylene fiber (CSRPF). For this, a comprehensive set of tests encompassing splitting tensile strength (STS) assessments and nuclear magnetic resonance (NMR) examinations is conducted. A total of 252 CSRPF specimens with varying fiber content (0, 6‱, 8‱, and 10‱) are tested at different curing temperatures (30 °C, 40 °C, 50 °C, 60 °C, 70 °C, and 80 °C). The outcomes of the NMR examinations indicate that elevating the curing temperature induces the expansion of pores within CSRPF, both in size and volume, consequently contributing to heightened internal structural deterioration. STS tests demonstrate that the STS of CSRPF decreases as the curing temperature increases. Meanwhile, the STS of CSRPF increases with fiber content, with optimal fiber content being 8‱. Regression models accurately predict the STS, with the curing temperature exhibiting the greatest influence, followed by the fiber content according to sensitivity analysis. The research results provide a valuable reference for the use of CSRPF as railway subgrade filling under high temperature and drying conditions.

Mix-, storage- and temperature-invariant precipitation characteristics in white cement paste, expressed through an NMR-based analytical model

Proton NMR tests on hydrating white cement paste provide access to the mix-, storage-, and temperature-dependent evolutions of the hydrogen portions found in capillary and gel pores, solid C-S-H, and calcium hydroxide, respectively. The aforementioned dependencies vanish once the hydrogen molar fractions are plotted as functions of the precipitation degree, which we have introduced here as the ratio of the amount of hydrogen bound in solids, over the total amount of hydrogen. The precipitation rate is governed by one activation energy and a linear affinity function of the current precipitation degree normalized by its maximum value. The latter decreases linearly with increasing curing temperature, being consistent with the temperature-dependent water content of solid C-S-H. The corresponding water-to-silica ratio, together with the precipitation degree and the mix and storage characteristics, provide access to the volume fractions of the hydrogen-containing phases, of clinker, and of voids, as well as to the degree of hydration.

Experimental study of pure Class G cement hydration up to 150 °C and 50 MPa

A comprehensive experimental investigation of Portland cement hydration kinetics in a wide temperature range from 35 °C to 150 °C with pressure up to 50 MPa was performed by heat of hydration, chemical shrinkage and ultrasonic measurements. Increasing curing temperature was found to have a stronger acceleration effect during the main hydration period while increasing curing pressure had a stronger acceleration effect during the pre-induction period of cement hydration. By comparing chemical shrinkage test results with other methods of estimating cement degree of hydration, such as quantitative X-ray diffraction, non-evaporable water content measured by thermogravimetric analysis, as well as heat of hydration, it was observed that total chemical shrinkage of cement at complete hydration decreased with curing temperature from 35 °C to 75 °C and then stayed stable between 75 °C and 150 °C. Similarly, the P-wave velocity of cement (which is an indicator of physical and mechanical properties) as a function of hydration degree decreased with increasing curing temperature in the range between 35 °C to 75 °C, then remained relatively stable between 75 °C and 130 °C. The reduction of gel water content in C–S–H from 35 °C to 75 °C is believed to be the primary cause of these observed phenomena.

Strength, Deformation Behavior, and Microstructure of Cement Paste Backfill with Calcium Chloride in Subzero Environments

This manuscript presents and discusses the results of an experimental study on the deformation behavior, strength, and microstructural development of cemented paste backfill (CPB) with chloride-bearing antifreeze (calcium chloride, CaCl2) in subzero environments. CPB samples with CaCl2 at various concentrations (0, 5, 15, and 35 g/L) were cured at different subzero temperatures (−1, −6, and −12°C) that represent temperatures to which CPBs may be exposed in mines located in permafrost or cold regions. Unconfined compressive strength (UCS) tests were conducted after specific curing time (7, 28, 60, and 90 days). Moreover, microstructural analyses and monitoring experiments (for volumetric water content and matric suction) were performed. The results showed that the addition of calcium chloride antifreeze reduced the strength of CPB and had a significant impact on its stress–strain behavior and microstructural characteristics. Furthermore, it was also found that the strength of CPB decreased with an increase of calcium chloride concentration and subzero curing temperature. These findings provide important guidance for mine backfilling work of CPB with chloride-bearing antifreeze additives and productivity improvement in subzero environments.

Effect of waste colemanite and PVA fibers on GBFS-Metakaolin based high early strength geopolymer composites (HESGC): Mechanical, microstructure and carbon footprint characteristics

This study investigated the effects of polyvinyl alcohol (PVA) fiber and colemanite on the physical, mechanical and transport characteristics of GBFS-metakaolin-based geopolymer composites with high early-age strength (HESGC). The microstructure was intensified using 100, 150 and 200 kg/m3 colemanite instead of quartz powder. In addition, 0.25% and 0.50% PVA fiber were added to the blend to prevent the permeability problem in the condensed microstructure. HESGCs were cured in 3 different environments: ambient, 60 and 80 °C. The binder dosage (GBFS + Metakaolin) in HESGCs is 750 kg/m3. The alkali solution ratio is approximately 75% (according to binder amount. While the apparent porosity exceeds 10% in HESGCs subject to ambient cure, the porosity % in heat-cured HESGCs) In addition, the porosity and water absorption decrease when colemanite is used in heat cured HESGCs. Adding 0.25% PVA fiber to HESGCs creates a micro-aggregate effect, reducing porosity and water absorption relatively. It varies between 2393 kg/m3. The compressive strength (fc) of HESGCs subjected to ambient cure varies between 27.5 and 43.8, and the fc of HESGCs heat cured at 80 °C varies between 77.4 and 95.6 MPa. The flexural strength (ff) of HESGCs varies between 3.6 and 13.3 MPa. As the PVA fiber content and curing temperature increase, the ff increases. If 0.5% PVA fiber is used, the ff of HESGCs is increased between 8.3% and 89.6%0.200 kg/m3 colemanite is used in heat-cured HESGCs fc can increase up to 20%. While 0.25% PVA fiber ratio is the most suitable ratio in fc, 0.5% PVA fiber ratio is more suitable in ff. The capillary water absorption of HESGCs varies between 0.27–2.67 kg/m2. In the case of heat curing of HESGCs at 80 °C instead of ambient curing, capillary water absorption can be reduced up to 88%. Using colemanite instead of fine aggregate in microstructure investigations intensified the microstructure, but using 0.5% PVA fiber increased the porosity relatively. As a result, it has been observed that heat curing must be used in colemanite-containing HESGCs. When a heat cure is applied to HESGCs containing 0.25% PVA fiber and 200 kg/m3 colemanite, a fc of more than 12 MPa can be obtained.

Effects of thermal treatment on the mechanical properties, microstructure and phase composition of an Ettringite rich cement

Recently calcium sulfoaluminate cements gain increasing attention due to their significant potential to reduce the carbon footprint of cement production compared to Portland cement. However, the conditions applied during its processing play a crucial role for the stability and longevity of the material. Thereby, the temperature has a decisive influence, as it is already known from numerous studies that ettringite structurally changes significantly upon thermal induced dehydration. Within this background, the present study subjects a holistic view of the mechanical, morphological, phase and structural changes of a commercial calcium sulfoaluminate cement related to the dehydration of the contained ettringite upon treatment at drying temperatures from 23 °C to 100 °C for 7 and 28 days. By complementary methods it is shown that with increasing curing temperature, the mechanical stability decreases, the total pore area and porosity increase, while the permeability of the microstructure is lower for samples stored at 100 °C. Removal of water increases the intercolumnar distance within the ettringite lattice, thereby inducing strain which is released upon rehydration. Although during storing at a temperature of 100 °C ettringite is transformed into an X-ray amorphous product, the initial morphology of the crystals embedded in the cementitious matrix is retained.

Mechanical properties of high-ductility concrete at different temperatures

In this study, the uniaxial compression and splitting tensile properties of high-ductility concrete (HDC) at different temperatures were investigated. The uniaxial compression strength and splitting tensile strength of HDC under standard curing (20 ± 2°C; ≥95% humidity), water curing (15 ± 2°C; 100% humidity) and −20°C curing (−20 ± 2°C, 75–85% humidity) conditions were investigated. The variation of stress–strain response, elastic modulus and peak stress of HDC under uniaxial compression at different temperatures and the evolution of splitting tensile strength and energy were analysed. The results revealed the strength variation mechanism of HDC under different curing conditions. From the test data, the relationships between the uniaxial compressive strength, splitting tensile strength of HDC and splitting tensile energy and the curing temperature were obtained. A constitutive model of the uniaxial compression of HDC under environments of different temperatures was established. With increasing curing temperature, the compressive strength, splitting tensile strength, elastic modulus and energy of HDC specimens increased gradually, while the peak strain decreased gradually. The effect of curing temperature on compressive strength was significantly more pronounced than that on splitting tensile strength.

Ultrasound Non-Destructive Characterization of Early Hydration of Cement Pastes: The Effects of Water-Cement Ratio and Curing Temperature

A newly developed ultrasound method that acquires at the same time both reflected and transmitted P-waves, at different angles, using two immersion transducers of 0.5 MHz central frequency, is described in this present study. This non-destructive method allows calculating the longitudinal and transverse velocities, and thus, the Young modulus, so that its evolutions is followed in time domain. The closely correlation between the evolution in time domain of those calculated parameters and hydration properties of cement based materials was used to characterize the effects of different water-cement ratio and curing temperatures on early age hydration behaviour of cement pastes. To do so, cement samples were prepared by mixing Portland cement and freshwater. Results indicates that lower water to cement ratio reduces the workability and increases the Young modulus of resulted cement medium. Also, both ultrasound velocities and Young modulus values increases linearly with increasing curing temperature.

Pozzolanic activity of pumice under different curing temperatures and durations

Objective of the work: This study focused on the investigations of the pozzolanic activity of the pumice under different curing temperatures and durations. 
 Materials and Method: Pumice powder, standard sand and slaked lime were used as materials in this study. Within the scope of the study, only one mixture design was used following TS 25. In total, 9 different curing regimes such as three different heat cures at 55˚C, 75˚C, and 90˚C and three different curing durations as 7, 14, and 28 days for each curing temperature. Some experimental analyses including compressive strength, flexural strength, and ultrasonic pulse velocity test were conducted to investigate the effect of the curing conditions on the pozzolanic activity of pumice. 
 Results: The pozzolanic activity of pumice increased with increasing curing temperature and duration up to a certain level. The optimum curing regime obtained for the puzzolanic activity of pumice in this study was curing at 75 ˚C for 28 days, which the highest strength values were obtained with.

Effect of cure temperature on the mechanical properties of epoxy-aluminium single lap joints

ABSTRACT Mixed adhesive joints combining different stiffnesses and strengths in the same overlap is a good strategy to increase the mechanical properties. For this purpose, different adhesives with distinct curing temperatures are used, whose optimization is crucial to maximize the mechanical performance. In this context, this study considers Araldite® AV 4076–1/HY 4076 and Araldite® AW 106/HV 953 U adhesives to evaluate the effect of curing temperature on tensile strength, creep and stress relaxation response and fatigue strength of single lap joints. It was possible to conclude that both adhesives exhibited higher static strength, lower stress relaxation and lower creep displacements with increasing curing temperature, but while for the brittle adhesive this trend occurred up to 150°C for the ductile one it was only up to 70°C. After this value, all properties regressed due to the degradation of the ductile adhesive with temperature. Considering values corresponding to 25% of the tensile strength, for example, it was noted that the ductile adhesive relaxes 54.7% more than the fragile one and presents a creep displacement around 95.1% higher. On the other hand, while the fatigue life was shown to be insensitive to the curing temperature for the brittle adhesive, in the case of the ductile one it decreases after 70°C. Therefore, when these adhesives are combined into a mixed adhesive joint, the curing temperature must never exceed 70°C.

Experimental Investigation on the Evolution of Tensile Mechanical Behavior of Cement Stone Considering the Variation of Burial Depth

The cement sheath is an annular structure between casing and formation, which is crucial to the integrity of the wellbore system. Considering that the temperature and pressure environment is changing continuously with increasing burial depth, the micro-structure and macro=mechanical properties of the in-situ cement sheath will change accordingly. To investigate the variation of burial depth on the evolution of the tensile mechanical behavior of oil cement stone, five temperature-pressure curing and testing conditions (25 °C—0 MPa, 50 °C—10 MPa, 80 °C—20 MPa, 110 °C—30 MPa, and 140 °C—40 MPa) are set to approximately simulate an in situ temperature-pressure environment at five typical burial depths (0 m, 1000 m, 2000 m, 3000 m, and 4000 m). The in situ tensile behavior, micro-structure and pore size distribution of the cement stones at each condition are tested and comparatively analyzed. Results show that with increasing temperature and pressure, the brittleness of the cement stone reduces and its ductility strengthens accordingly. The tensile strength experiences rapid growth at first, then increases at a slower rate and finally decreases. The failure mode of the cement stone gradually transforms from tensile splitting to tensile-shear composite fracture, accompanied by increasing fracture surface roughness. Microscopically, with increasing curing temperature and pressure, the pore structure of cement stone gradually transforms from closely stacked laminated sheets to interconnected fiber networks. The dense structure of cement stone gradually becomes loose and porous. The porosity also increases from 15.96% to 29.46%.

Effect of curing temperature and water-to-cement ratio on corrosion of steel in calcium aluminate cement concrete

• CAC specimens were made with different w/c, and cured at different temperatures. • The w/c and temperature played a crucial role in the porosity of CAC. • Increasing the curing temperature can improve the corrosion resistance of CAC. This study evaluated the corrosion resistance of pure calcium aluminate cement (CAC) concrete specimens made with water-to-cement ( w/c ) ratios of 0.4, 0.5, and 0.6 and cured at 4, 21, and 90 °C following the ASTM G109 standard. Thermogravimetric analysis results showed increased CAC conversion with increased curing temperature. Compressive strength and bulk electrical resistivity measurements showed that the CAC specimens had lower strength and higher bulk electrical resistivity than ordinary portland cement (OPC) concrete. Macrocell corrosion currents measured after cyclic exposure to chloride solutions showed that the CAC specimens were highly permeable and less resistant to chloride-induced corrosion than OPC concrete. Among the different CAC specimens tested in this study, the specimens made with a w/c of 0.4 and cured at 90 °C showed the highest corrosion resistance.