Strength Retrogression Research Articles

Evaluation and Optimization of Cement Slurry Systems for Ultra-Deep Well Cementing at 220 °C

With the depletion of shallow oil and gas resources, wells are being drilled to deeper and deeper depths to find new hydrocarbon reserves. This study presents the selection and optimization process of the cement slurries to be used for the deepest well ever drilled in China, with a planned vertical depth of 11,100 m. The bottomhole circulating and static temperatures of the well were estimated to be 210 °C and 220 °C, respectively, while the bottomhole pressure was estimated to be 130 MPa. Laboratory tests simulating the bottomhole conditions were conducted to evaluate and compare the slurry formulations supplied by four different service providers. Test results indicated that the inappropriate use of a stirred fluid loss testing apparatus could lead to overdesign of the fluid loss properties of the cement slurry, which could, in turn, lead to abnormal gelation of the cement slurry during thickening time tests. The initial formulation given by different service providers could meet most of the design requirements, except for the long-term strength stability. The combined addition of crystalline silica and a reactive aluminum-bearing compound to oil well cement is critical for preventing microstructure coarsening and strength retrogression at 220 °C. Two of the finally optimized cement slurry formulations had thickening times more than 4 h, API fluid loss values less than 50 mL, sedimentation stability better than 0.02 g/cm3, and compressive strengths higher than 30 MPa during the curing period from 1 d to 30 d.

Long-term performances of hydroceramic systems as a potential cementing material at 240 °C

The performance of the Ca(OH)2–Al2O3–SiO2–H2O hydroceramic system (with and without Al2O3) as a potential well cementing material was investigated from both macroscopic and microscopic perspectives. To simulate the harsh conditions typical of deep wells, marked by high temperature and pressure, the material was cured at 240 °C and 50 MPa. Several hydroceramic systems with varying compositions were designed and a retarder was used to optimize the thickening time of all systems. Finally, the optimized hydroceramic systems were cured for different periods ranging from 2 to 90 days to investigate their long-term stabilities. It is found that the raw materials with finer particle sizes and higher reactivity (such as silica fume and nano-activated alumina) could improve the performance of the hydroceramic system, evidenced by increased compressive strengths and decreased permeability. Changing the Ca/Si molar ratio within the range from 2:1 to 1:1 had little effect on the physical and mechanical properties of the hydroceramic system, despite significant variations in the composition of hydration products. The hydroceramic systems exhibited good stability over a curing period from 2 to 30 days, but strength retrogression phenomenon was observed during longer curing periods from 30 to 90 days. Microscopic evaluations revealed that the strength retrogression could be due to the formation of reyerite in high calcium systems, while it was the conversion of amorphous C–S–H to xonotlite that led to the strength retrogression in low calcium systems.

Anti-strength retrogression cementing materials for deep and ultra-deep wells

Recent studies have brought to light a critical issue pertaining to the conventional silica-enriched Portland cements employed in deep and ultra-deep wells. The traditional silica-enriched oil well cements were found to exhibit substantial strength retrogression during prolonged curing under high temperatures, posing a significant threat to the overall cementing quality and subsequent production safety. This study proposes a novel approach to enhance the long-term stability of traditional silica-cement systems under high temperature conditions by introducing both granulated blast furnace slag (GBFS) and fly ash to the system. Test results indicated that the addition of GBFS increased the strength stability of the traditional silica-cement system but failed to completely prevent its strength retrogression. In contrast, the combined addition of GBFS and fly ash in silica-cement system significantly enhanced its long-term strength measured after 90 d curing. The strength test results were corroborated by further evidences from permeability tests as well mercury intrusion porosimetry analyses. Detailed analysis of the set cement composition suggests that the inhibition of xonotlite phase and the promotion of tobermorite and grossular phases in hydration products are responsible for improved long-term strength stability.

Valorization of lead-zinc mine tailing waste through geopolymerization: Synthesis, mechanical, and microstructural properties

Lead-zinc mine tailing waste can have significant environmental impacts due to its potential for releasing toxic elements into the surroundings and contaminating local soil and water. This paper focuses on the valorization of lead-zinc mine tailing waste through geopolymerization, a sustainable process that can transform waste into useful building materials. Geopolymer matrixes with various mixtures of mine tailing (0−100 wt%), fly ash (0−100 wt%), and flue gas desulfurization (FGD) gypsum (0, 5, and 10 wt%) were synthesized using different activators such as sodium hydroxide (NaOH, 5, 10 M) and sodium silicate (waterglass, 0, 12.5 wt%). Visual inspection, unconfined compressive strength (UCS) testing, and microstructural analysis (e.g., X-ray diffractions, Fourier transforms infrared, and scanning electron microscopy) were employed for the physicochemical characterization of these geopolymers. The highest UCS value of 24.1 MPa was observed in a geopolymer specimen with 100 wt% fly ash and activated by 10 M NaOH and cured for 28 days. The blending of mine tailings would result in strength recession, e.g., the integrating of 25 wt% tailings showed a UCS of 12.3 MPa. The addition of 5 wt% gypsums can improve early strength development, particularly for matrixes with 50–75 wt% fly ash. But adding 10 wt% gypsums would lead to strength retrogression of the resulting geopolymers. The introduction of waterglass can also facilitate geopolymerization and improve strength development. However, the cointegrating of gypsum and waterglass can induce an antagonistic effect and lead to the collapse of the geopolymer specimens. The findings revealed that the strength and microstructural properties of geopolymer are determined by the matrix compositions, alkaline activators, etc. Effective regulation of these factors can produce geopolymer matrixes with high dimensional stability and UCS that well meet construction material standards. Overall, the study indicates that geopolymerization represents a viable and eco-friendly solution for valorizing lead-zinc mine tailing waste and gaining alternative building materials.

Recycling of clay brick powder to improve the microstructure and mechanical properties of oil well cement pastes at high temperature and high pressure conditions

In oil well cementing involving high temperature and high pressure (HTHP), silica sources are usually incorporated into oil well cement to prevent its strength retrogression. This paper aims to use recycled clay brick powder (CBP), a silica-enriched material, as an alternative to the use of silica flour (SF) to inhibit the strength retrogression of the cement pastes after thermal cycling curing at 300 °C/13.0 MPa. Pure pastes (G), blended pastes with 40 wt% SF (40SF) and blended pastes with 40 wt% CBP (40CBP) were prepared to comparative analysis. The results showed that 40CBP and 40SF exhibited lower compressive strength and poorer pore structure than the G samples at 50 °C. However, the incorporation of CBP could effectively improve the compressive strength of the cement at 300 °C/13.0 MPa compared to that of the G paste. Mineralogical analysis indicated that xonotlite phases were the main crystalline phases in 40CBP and 40SF after thermal cycling curing. Compared to reinhardbraunsite in G samples, xonotlite could improve the pore structure and make the microstructure denser. In addition, there are some hibschite phases in 40CBP, which may make its compressive strength slightly lower than 40SF. Nevertheless, the environmental impact and cost analysis showed that the energy intensity and CO2 emissions of 40CBP were significantly lower than those of G and 40SF, and it had great cost advantages. This study is expected to provide some help in the rational recycling of CBP and reducing the CO2 emissions in cement production.

Combined use of fly ash and silica to prevent the long-term strength retrogression of oil well cement set and cured at HPHT conditions

The long-term strength retrogression of silica-enriched oil well cement poses a significant threat to wellbore integrity in deep and ultra-deep wells, which is a major obstacle for deep petroleum and geothermal energy development. Previous attempts to address this problem has been unsatisfactory because they can only reduce the strength decline rate. This study presents a new solution to this problem by incorporating fly ash to the traditional silica-cement systems. The influences of fly ash and silica on the strength retrogression behavior of oil well cement systems directly set and cured under the condition of 200 °C and 50 MPa are investigated. Test results indicate that the slurries containing only silica or fly ash experience severe strength retrogression from 2 to 30 d curing, while the slurries containing both fly ash and silica experience strength enhancement from 2 to 90 d. The strength test results are corroborated by further evidences from permeability tests as well as microstructure analysis of set cement. Composition of set cement evaluated by quantitative X-ray diffraction analyses with partial or no known crystal structure (PONKCS) method and thermogravimetry analyses revealed that the conversion of amorphous C-(A)-S-H to crystalline phases is the primary cause of long-term strength retrogression. The addition of fly ash can reduce the initial amount of C-(A)-S-H in the set cement, and its combined use with silica can prevent the crystallization of C-(A)-S-H, which is believed to be the working mechanism of this new admixture in improving long-term strength stability of oil well cement systems.

Effect of curing regimes on strength of magnesium silicate hydrate cement

This study aimed to investigate the impact of different curing regimes on the strength of magnesium silicate hydrate cement (MSHC). The study employed various microscopic tests, including XRD, TG, SEM, and MIP, to analyze the underlying mechanisms. The research findings demonstrated that the use of short-term high-temperature curing under the two-stage variable temperature curing regime (TTC) significantly enhanced the early strength of MSHC, with a 3d strength exceeding 30 MPa. In contrast, under standard curing (SC), the strength was only around 2 MPa. The samples subjected to TTC did not exhibit the strength retrogression phenomenon observed under high-temperature curing in previous research, and a high-temperature curing duration of 48 h was found to be more beneficial for the strength development of MSHC. However, from a long-term perspective, the late-stage strength of the TTC samples was lower than that of the SC samples. Microscopic tests revealed that increasing the curing temperature substantially improved the early hydration degree of MSHC, reduced its porosity, and resulted in a more compact cement matrix, thereby enhancing the early strength. Under TTC, hydration continued in the later stage, leading to a decrease in porosity and promoting further strength growth. However, in the long-term, the microstructure of the TTC samples became loose, and the interface connection between silica particles and gel weakened. Compared to the SC samples, the TTC samples exhibited higher porosity, resulting in lower long-term strength.

Influence of testing temperature and pressure on the mechanical behavior of well cementing materials

In order to obtain insights into the mechanical responses of well cementing materials under various service conditions and provide more precise guidance for well cementing design, the mechanical behavior of a silica-enriched well cement system was investigated at various temperatures, pressures and drying conditions. Prior to mechanical testing, ultrasonic strength tests and a series of microscopic tests were conducted to verify that the silica-cement system cured at 150 °C/20.7 MPa exhibited stable properties with limited risk of strength retrogression. Triaxial tests conducted at ambient temperature (25 °C) demonstrate that the well cement exhibited an increase of peak strength and plasticity with increasing confining pressure, particularly under dry conditions. Additionally, brittle to ductile transition is more readily achieved for dried samples. However, the simultaneous application of both high temperature and high confining pressure (150 °C/30 MPa) resulted in reduced yield stress of the well cement, possibly because the weakening effect of high temperature overpowers the strengthening effect of high confining pressure. The peak strength and yield stress of the well cement increased significantly with the reduction of water content. The plasticity of the well cement increased upon the removal of evaporable water, but decreased with the removal of nonevaporable C–S–H bound water.

Effects of tannic acid on the late-age strength of autoclave curing cement paste

The long-term performance regression of thermal curing concrete threatens the durability and safety of structure. With the popularization of prefabricated components, the problem needs to be solved urgently. Tannic acid (TA), a natural polyhydroxyl compound, has retarding and enhancing effect on cement. The former effect can partially offset the rapid hydration of thermal curing initially and the latter can resist drying shrinkage in subsequent air curing. Thus TA is proposed to mitigate the strength retrogression of autoclave curing cement paste in this research. As a result, the flexural strength of autoclave curing cement paste mixed with 0.025% TA is improved by 44.1% than samples without TA at 28 days. And the flexural strength loss rates because of total damage and subsequent air curing are decreased to −8.9% and 12.5% from 24.4% and 26.9%, respectively. XRD and TGA results show that the hydration of autoclave curing cement paste can be improved by 0.025% TA where the bound water is increased by 6.6%. SEM observations and MIP analysis prove that 0.025% TA can make the matrix dense and decrease the porosity by 14.4% under thermal curing. Besides, TA can promote the generation of nano network structure and bridge the hydration products, which is beneficial to disperse the tensile load. Thus TA can improve the long-term properties (especially flexural strength) of autoclave curing cement paste greatly.

Performance of Silica Fume on Preventing Strength Retrogression in Hardened Cement Paste and Mortar at Elevated Temperatures

This study examines the effect of silica fume (SF) as a partial replacement for cement to prevent strength retrogression in hardened cement paste (HCP) and mortar at elevated temperatures. An experimental procedure was conducted on 320 specimens, replacing 0, 10, 20, and 30% of the cement by weight with SF. The residual compressive strength of the specimens was evaluated at room temperature (25 °C) and at 100, 200, 300, and 400 °C for 7, 28, and 56 days. The results indicate that the addition of SF to the cement paste and mortar improves the compressive strength both at 25 °C and at temperatures up to 400 °C. That is attributed to the formation of C-S-H phases, such as tobermorite and xonotlite. Additionally, the optimal residual compressive strength was achieved by adding 30% of SF. Therefore, XRD, SEM, and EDS techniques were employed to evaluate the microstructure of HCP specimens with 30% of SF. The results show that adding SF leads to a denser microstructure and lower porosity, resulting in more durable cement paste and mortar at ambient and elevated temperatures. In conclusion, using SF as a partial replacement for cement can be an effective way of developing sustainable fire-resistant construction materials.

Experimental Investigation of Geopolymers for Application in High-Temperature and Geothermal Well Cementing

Summary With recurrent calls for a reduction in carbon emissions, geothermal (GT) energy has received increasing attention in recent years as a prominent source of clean energy. With current drilling technology, GT wells are being constructed in extremely challenging temperature environments, which could reach more than 600°F (315°C) in situ. However, GT well-cementing technology has not changed much over the past few decades, with ordinary Portland cement (OPC) still being the primary choice of cementing material. OPC has several drawbacks, including brittle behavior, shrinkage upon setting, poor bond strength to formation and casing, susceptibility to an acid gas attack, temperature-induced strength retrogression, and low tolerance toward drilling fluid contamination. These factors could lead to a poor cementing job, thus compromising well integrity and not ensuring proper zonal isolation for the life of the GT well. Thus, there is a need to develop an alternative material that is compatible with the GT environment and able to provide long-term zonal isolation. With a low carbon footprint, self-healing ability, and low shrinkage sensitivity, geopolymers or alkali-activated materials could be a suitable option to augment or even replace OPC. Some of the previous studies on geopolymers have shown that they could be a potential candidate for oil and gas well cementing and civil engineering applications, with some being stable at very high temperatures [up to 1,470°F (800°C)]. Geopolymers are formed by mixing an aluminosilicate source such as fly ash (FA) with an alkali-activating solution, such as sodium or potassium hydroxide or silicate. The aim of the study reported here is to demonstrate the applicability of geopolymers for GT well cementing. An experimental investigation was carried out to understand the behavior of geopolymer formulations made from FA, metakaolin (MK), and blast furnace slag in a high-temperature environment. The material properties such as porosity, viscosity, thickening/pump time, compressive strength, tensile strength, and bond strength were tested in the laboratory. It was found that geopolymer can be formulated to have the desired rheological properties with adequate pump time and resistance to drilling fluid contamination. In addition, the formulations can exceed the required compressive and tensile strength for GT cementing operations, while obtaining excellent bond strength values. These findings indicate that geopolymers are well-suited to provide long-term zonal isolation in high-temperature GT wells.

Hydration kinetics and strength retrogression mechanism of silica-cement systems in the temperature range of 110 °C–200 °C

A comprehensive investigation of silica-cement hydration kinetics and engineering properties in the temperature range from 110 °C to 200 °C and pressure range from 25 MPa to 50 MPa were conducted by isothermal calorimetry, chemical shrinkage, and ultrasonic cement analyzer. Test results revealed that the effect of curing temperature on the hydration kinetic profiles is very complex, while the influence of pressure is relatively evident. The heat of hydration of the silica-cement system is approximately proportional to chemical shrinkage and the proportionality constant is invariant with curing temperature. Strength retrogression of silica-cement systems is caused by the transformation of amorphous C-S-H to xonotlite and tobermorite and is accompanied by volume expansion possibly due to the conversion of chemically bound water to free water. Increasing curing pressure can accelerate the volume expansion and phase transformation process during early age, while increasing silica dosage can significantly slow down such process.

Various admixtures to mitigate the long-term strength retrogression of Portland cement cured under high pressure and high temperature conditions

In order to investigate the problem of long-term strength retrogression in oil well cement systems exposed to high pressure and high temperature (HPHT) curing conditions, various influencing factors, including cement sources, particle sizes of silica flour, and additions of silica fume, alumina, colloidal iron oxide and nano-graphene, were investigated. To simulate the environment of cementing geothermal wells and deep wells, cement slurries were directly cured at 50 MPa and 200 °C. Mineral compositions (as determined by X-ray diffraction Rietveld refinement), water permeability, compressive strength and Young's modulus were used to evaluate the qualities of the set cement. Short-term curing (2–30 d) test results indicated that the adoption of 6 μm ultrafine crystalline silica played the most important role in stabilizing the mechanical properties of oil well cement systems, while the addition of silica fume had a detrimental effect on strength stability. Long-term curing (2–180 d) test results indicated that nano-graphene could stabilize the Young’s modulus of oil well cement systems. However, none of the admixtures studied here can completely prevent the strength retrogression phenomenon due to their inability to stop the conversion of amorphous to crystalline phases.

Corrigendum: Mechanism of long-term strength retrogression of silica-enriched Portland cement assessed by quantitative X-ray diffraction analysis

Corrigendum on: Qin J, Pang X, Li H and Zhang Z (2022), Mechanism of long-term strength retrogression of silica-enriched Portland cement assessed by quantitative X-ray diffraction analysis. Front. Mater. 9:982192. doi: 10.3389/fmats.2022.982192 In the published article, there was an error in Figures 4, 8, 9, 10 and 11 as published. The mass absorption coefficient (MAC) is not corrected when calculating the phase compositions of the sample 180d-FS-1. The corrected Figure 4, 8, 9, 10 and 11 and its caption appear below.PAGE \ 2 \ 6 MERGEFORMAT 3

Research on the strength retrogression and mechanism of oil well cement at high temperature (240 ℃)

In light of the problem that the strength retrogression pattern and mechanism of oil well cement containing silica sand at high temperature are still unclear, the strength, permeability, hydration products, and micromorphology for cement containing silica sand under the condition of 240℃ were investigated. The results show that the strength of cement with addition of 50% silica sand gradually decreases with curing time, while the corresponding permeability begins to grow progressively at 240℃. The hydration products are mainly composed of xonotlite and massive scawtite crystals in the early stage. In the later stage, it is needle-rod-shaped xonotlite and scawtite in the surrounding. As a result, the mechanical properties decline significantly. The overall strength of the cement with addition of 80% silica sand is lower than that with 50%, while there are a large number of knitted/coarse needle-shaped crystalline xonotlite and blocky scawtite in the hydration product. Also, xonotlite increases significantly in the early and late stages, but its overall content (for 80% silica sand) was less than the content with additon of 50% silica sand in the same period. This indicates that simply increasing the amount of silica sand could not solve the problem of strength retrogression of cement under extremely-high temperature. The reason for the decline may be that the large content of silica sand inhibits the hydration reaction to some extent.

Effect of the crystalline state of SiO2 on the compressive strength of cement paste at HTHP

Silica flour is often added to oil well cement to prevent the strength retrogression of cement paste at high temperature and high pressure (HTHP). Fused silica, as a non-crystalline form of silicon dioxide (SiO2), has a higher solubility than silica flour during cement hydration at HTHP and has a different effect on the strength stability of cement paste. This paper investigated the compressive strength and permeability of cement pastes incorporating SiO2 with different crystalline state (silica flour and fused silica) cured at 260 °C and 21 MPa for 1, 7 and 28 d. The phase evolution and microstructure of hardened cement pastes (HCPs) were characterized by X-ray diffraction (XRD), mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM) and energy disperse spectroscopy (EDS). The result showed that HCPs incorporating 30 % silica flour had the highest compressive strength. 35 % silica flour was excess and α-SiO2 was observed from XRD pattern. Fused silica was more beneficial to the compressive strength than silica flour when their replacement rates were both 25 %. XRD showed that xonotlite was the main crystal phase in HCPs incorporating silica flour or fused silica. In addition, truscottite was identified in HCPs incorporating 35 % fused silica. The transformation of truscottite was not conducive to the pore structure and strength of HCPs. The properties and microstructure of HCPs were influenced by the different phase evolution. Solubility of SiO2 with different crystalline state affected the equilibrium of CaO-SiO2-H2O system of during the early age cement hydration at HTHP.

Mechanism of long-term strength retrogression of silica-enriched Portland cement assessed by quantitative X-ray diffraction analysis

In order to clarify on the driving force of cement long-term strength retrogression, a comprehensive quantitative X-ray diffraction (XRD) analysis were conducted on silica-enriched (60%–80% by weight of cement) cement samples set and cured under the condition of 200°C and 50 MPa with a maximum duration of 180 days. The phase content evolution with time was determined by three different methods on the average of three specimens: the external standard method; the partial or no known crystal structure (PONKCS) method; and the hybrid method. Although the specific phase content estimated by different methods varied slightly, the overall trend of change of all phases were similar. The phase transformation in set cement at high temperature condition is dependent on the slurry composition. In silica-deficient system, tobermorite and amorphous C-S-H were transformed to xonotlite; while in silica-sufficient system, tobermorite and amorphous C-S-H were transformed to gyrolite. These phase transformations involve gradual structural changes of cement hydration products, which may be the driving force of long-term strength retrogression. However, such structural changes can only be detected by XRD once the transformation is complete.

Effects of various curing methods on the compressive strength and microstructure of blast furnace slag-fly ash-based cementitious material activated by alkaline solid wastes

The large-scale stacking of alkaline industrial solid wastes such as soda residue (SR) and calcium carbide residue (CCR) has caused serious environmental problems. Therefore, a new type of cementitious material was developed in our previous study by using SR-CCR synergistically activated blast furnace slag (BFS)-fly ash (FA), which abbreviated as SCBF. This paper further studied the effects of various curing methods on the compressive strength and microstructure of SCBF, which was expected to provide guidance for its application in the field of non-reinforced products such as baking-free brick. The results show that the optimal curing scheme was heat curing at 75 °C for 12 h. The optimal scheme significantly promoted an early hydration reaction and provided the 3d/28d strength values of 16.4/24.7 MPa, exceeding those of room-temperature (RT) sealed curing and water curing by 154/24.5 % and 264/31 %, respectively. Besides, the optimal scheme accelerated the formation of CSH gel, Hydrotalcite (6MgO·Al2O3·CO2·12H2O), Hydrocalumite (3CaO·Al2O3·CaCl2·10H2O), and other crystal products, as well as increased the consolidation rate of chlorine ion from 37.9 % (in RT sealed curing) to 64.3 %. These hydration products were evenly distributed, effectively filling the pores and reducing the macroporosity from 9.30 (in RT sealed curing) to 1.54 %, thus improving the early and later-age strength. Too high curing temperature (exceeding 75 ℃) or prolong heat curing period (exceeding 12 h) would cause microstructure deterioration, significantly increase the number of macropores and microcracks in the matrix, ultimately leading to strength retrogression.

Effects of Curing Pressure on the Long-Term Strength Retrogression of Oil Well Cement Cured under 200 °C

The influences of curing pressure on the physical and mechanical property development of oil well cement during long-term curing were studied. Five silica-enriched cement slurries designed without and with reinforcement materials (latex fiber and nano-graphene) were autoclaved at 200 °C under two different pressures. The low pressure (50 MPa) curing was conducted for 2, 60, 90 and 180 days; the high pressure (150 MPa) curing was conducted for 2 and 360 days. The physical and mechanical properties of set cement were characterized by compressive strength, Young’s modulus, and water/gas permeability; the mineral composition and microstructure were determined by X-ray diffraction, mercury intrusion porosimetry, thermogravimetry and scanning electron microscope. Test results showed that high pressure (150 MPa) curing led to a more compact microstructure, which reduced the rate of strength retrogression in the long term. Samples with reinforcement materials, especially the latex fiber, showed higher compressive strength, Young’s modulus and lower permeability during long-term curing at both pressures.

Insight into Class G Wellbore Cement Hydration and Mechanism at 150 °C Using Molecular Dynamics

Neat well cement experience significant strength retrogression at high temperatures above 110 °C, especially at approximately 150 °C. To reveal the mechanism of performance degradation and guide the preparation of high-performance cement, we investigate the hydration process, mechanical behavior, and fracture process for well cement at the temperature of 150 °C based on molecular dynamics simulations and experiments. From triaxial pressure tests and Brazilian splitting tests, the strength, elastic modulus, and Poisson’s ratio of well cement decrease drastically with temperature increases from 80 °C to 150 °C. According to XRD, TG/DTG/DSC, and SEM, the hydration degree is insufficient, and larger pores exist in the microstructures. As the main binding phase of well cement, the mechanism of calcium silicate hydrates (C-S-H) influenced by curing temperatures is investigated through molecular dynamics simulations. C-S-H with calcium/silicon ratios (C/S) of 1.1 and 1.8 are simulated in the aqueous and solid states to investigate precipitation and mechanical behaviors. By reducing the C/S ratio to 1.1, the strength rebounds to a certain extent, and the adequacy of the hydration degree improved. It is found from the polymerization process that the increasing temperature promotes the polymerization rate, which is higher with C/S = 1.8 than that of 1.1. However, an increase in the C/S ratio will lead to a decrease in bridging oxygen content, thus a lower polymerization degree. The fracture simulations of C-S-H gels at different temperatures indicate that the failure of the C-S-H structure is mainly attributed to the disassembling of the calcium oxygen layers. With a higher temperature, there are fewer Ca-O bonds breaking, thus less strain energy consumed, resulting in worse performance. The elasticity of C-S-H, including Young’s and shear moduli, also exhibits certain degradations at a higher temperature. The elastic behavior of C-S-H with a low C/S ratio is generally higher than the high C/S.