Compressive Strength of Basic Magnesium Sulfate Cement Coral Aggregate Concrete(MCAC)on Non-Destructive Testing

Basic magnesium sulfate cement coral aggregate concrete(MCAC)is a new type of concrete consisting of basic magnesium sulfate cement,coarse coral aggregate,coral reef sand and seawater.The rebound hammer(RH),the ultrasonic pulse velocity(UPV)and the compressive strength(fcu)tests of 14 sets of cube specimens of the MCAC after 28 d of aging were conducted.The impact of the content and length of sisal fiber on the relationship between the fcu-RH and the fcu-UPV was determined.A mathematical model was established to predict the strength of the MCAC using the UPV,RH,and comprehensive UPV/RH methods and to obtain the curves of test strength.The applicability of the test strength curves of ordinary portland concrete(OPC),light-weight aggregate concrete(LAC),and coral aggregate concrete(CAC)to MCAC was assessed.The results showed that the test strength curves of OPC,LAC and CAC were inappropriate to determine the strength of MCAC using non-destructive method.The relative standard error of the curves of test strength of the RH method and the comprehensive method met the specifications,whereas that of the UPV method did not.

Using Magnesium Sulfate to Prevent Atrial Fibrillation after Coronary Artery Bypass Grafting Surgery: A Single Centre Experience in Bangladesh

Background: Atrial fibrillation commonly occurs following cardiac surgery, particularly after coronary artery bypass grafting. Magnesium, known for its stabilizing effect on cell membranes, has shown promise in preventing postoperative atrial fibrillation. This study aimed to assess the impact of intravenous magnesium infusion in preventing atrial fibrillation after off-pump coronary artery bypass grafting, where maintaining stable cell membranes is crucial in averting this complication. Methods: A cross-sectional study was conducted at the Department of Cardiac Surgery, Bangabandhu Sheikh Mujib Medical University, from March 2020 to February 2022. Sixty-six patients who underwent off-pump coronary artery bypass grafting were enrolled and divided into two groups. Group A (n = 33) received intravenous magnesium sulfate (10 mmol/2.47gm) for three days after surgery, while Group B (n = 33) did not receive magnesium sulfate. Postoperative atrial fibrillation occurrence in the Intensive Care Unit (ICU) within three days after surgery was evaluated using convenient sampling. Statistical analysis was performed with SPSS version 26.0, utilizing independent Student’s t-test for continuous data and Chi-square and Fisher’s exact test for categorical data. A p-value of ≤0.05 was considered statistically significant. Results: No significant differences in age or gender were observed between the two groups. Group B exhibited significantly lower magnesium levels than Group A on the 0th, 1st, 2nd, and 3rd days post-surgery. Additionally, Group B experienced a higher incidence of postoperative atrial fibrillation, longer ICU stays, and two mortalities. The study did not detect any adverse effects associated with magnesium infusion. Conclusion: It has been demonstrated that administering magnesium intravenously after off-pump coronary artery bypass grafting can lower the chances of developing atrial fibrillation. This demonstrates the potential advantages of using magnesium as a preventative measure for postoperative atrial fibrillation in such cases.

Magnesium sulfate and fetal neuroprotection: overview of clinical evidence

Antenatal administration of magnesium sulfate is an important part of the neuroprotective strategy for preterm infants. Strong evidence from five randomized controlled trials and five meta-analyses has demonstrated that magnesium sulfate, when administered before preterm delivery, significantly reduces the risk of cerebral palsy at two years. Through secondary analyses of randomized controlled trials and other original clinical studies, this state-of-the-art review highlights the absence of serious adverse effects in both pregnant women and neonates, as well as the impact of maternal body mass index and preeclamptic status on the maternal and neonatal magnesium levels, which could influence the magnitude of the neuroprotective effect. Although antenatal magnesium sulfate is a cost-effective strategy, some practice surveys have demonstrated that the use of magnesium sulfate is not sufficient and that its use is heterogeneous, differing among different maternity wards. Since 2010, an increasing number of obstetrical societies have recommended its use to improve the neurological outcomes of preterm infants, especially the International Federation of Gynecology and Obstetrics and World Health Organization in 2015, and France in 2017. Considering the neuroprotective impact of magnesium sulfate when administered before delivery, postnatal administration should be considered, and its effects should be assessed using randomized controlled trials.

Effect of Limestone Powder and Fly Ash on Magnesium Sulfate Resistance of Mortar

The effect of limestone powder and fly ash on magnesium sulfate resistance of mortar was studied by testing on the strength, expansion and hydration products of the specimens stored in MgSO4 solution at certain periods. The experimental results show that the strength of mortar stored in MgSO4 solution increases a little before 28 d, but decreases fast subsequently. The more the contents of limestone powder and fly ash, the less the strength losses. Mortar swells in the MgSO4 solution with the soaking time. And the more the contents of limestone powder and fly ash, the less the expansion rate is. The expansion or strength loss of mortars results from the expansion of gypsum, as well as the loss of Ca（OH）2 and other hydration products of cement. The magnesium sulfate resistance of the mortars containing limestone powder and fly ash is high.

Interventional effect of magnesium sulfate on nitric oxide synthase activity after acute craniocerebral injury

BACKGROUND： Abnormal changes in magnesium ion are closely related to cerebral injury. At present, some evidence indicates that magnesium reagent can improve nerve function and prognosis of patients with cerebral injury. OBJECTIVE： To observe the effect of magnesium sulfate on changes in nitric oxide synthase （NOS） activity in brain tissue of rats with acute craniocerebral injury. DESIGN： Completely randomized grouping design and randomly controlled study. SETTING： Laboratory of Neurosurgery, the Third Hospital of Chinese PLA. MATERIALS： Fifty-four male SD rats of clean grade and weighing 220 - 250 g were randomly divided into normal control group （n =6）, cerebral injury group （n =24） and magnesium sulfate group （n =24）. Especially, rats in cerebral injury group and magnesium sulfate group were equally divided into four subgroups and observed at 0.5, 2, 6 and 24 hours after model establishment. A solution of 125 g/L of magnesium sulfate was provided by the Seventh Pharmaceutical Factory of Wuxi and the NOS assay kit by Nanjing Jiancheng Bioengineering Institute. METHODS： The experiment was carried out in the Institute of Neurosurgery, the Third Hospital of Chinese PLA from August 2000 to August 2002. ① Rats in the cerebral injury group and magnesium sulfate group were anesthetized to establish cerebral injury models based on modified Feeney technique; magnesium sulfate group were intraperitoneally injected 600 mg/kg magnesium sulfate （125 g/L）, but rats in the normal control group remained untreated. ② At 0.5, 2, 6 and 24 hours after cerebral injury, rats in cerebral injury group and magnesium sulfate group were decapitated and brains were dissected. Cerebral cortex of rats in cerebral injury group was selected for NOS assay; in addition, at 0.5 hour after cerebral injury, a portion of the parietal lobe was selected from the brains of rats in the normal control group. Brain samples were homogenized, the homogenated centrifuged and the supernatants were used to measure NOS activity with NOS kit. ③ Differences among the three groups were compared with t test. MAIN OUTCOME MEASURES： NOS activity in cerebral cortex of rats in each group. RESULTS： A total of 54 SD rats were involved in the final analysis. At 0.5 hour after cerebral injury, NOS activity in cerebral cortex was （42.45 ± 13.46） nmol/L in cerebral injury group and （41.17 ± 12.53） nmol/L in magnesium sulfate group, respectively, which was higher than that in normal control group [（39.45 ± 11.84） nmol/L, P 〈 0.05]. At 2 hours after cerebral injury, NOS activities were （66.48 ±21.43） and （63.24 ± 19.18） umol/L, respectively, while at 6 hours after cerebral injury, NOS activities were （62.45 ± 24.18） and （51.97 ±20.46） nmol/L, respectively, which were higher than those in normal control group （P 〈 0.0 1）. At 24 hours after cerebral injury, NOS activity returned to basal level. Moreover, NOS activity was significantly lower in the magnesium sulfate group than that in the cerebral injury group at 2 and 6 hours after cerebral injury （P 〈 0.05, 0.01）.CONCLUSION： NOS activity is increased in injured brain tissue of rats with craniocerebral injury, and treatment with magnesium sulfate provides some degrees of protection possibly through inhibition of NOS activity after cerebral injury.

Research on the Evaporating Crystalization Behavior of the Magnesium Sulfate Subtypes Brine at High Temperature

Research the evaporating crystalization process of the magnesium sulfate subtypes brine at high temperature from Dalangtan salt lake in Qinghai province.It was revealed that the salt lake is a typical subtype magnesium

Does magnesium sulfate increase the incidence of postpartum hemorrhage? A systematic review

The incidence of Postpartum Hemorrhage (PPH) is increasing in the western world. We hypothesize that magnesium sulfate (MgSO4) could be a contributing factor. MgSO4 might increase the incidence of PPH by induction of vasodilation, tocolytic effects, and effects on the blood like red cell deformity, platelet activity inhibition and a prolonged bleeding time. Based on these effects of MgSO4 a correlation with PPH is suspected. MgSO4 is widely used in the prevention of eclampsia. However, the working mechanism of this effective drug is largely unknown. We performed a systematic search to find all Randomized Controlled trials (RCTs) containing MgSO4 in preeclamsia as well as all MgSO4 studies with information on PPH. Titles, abstracts and references of publications were evaluated for appropriateness and whether they met the inclusion criteria. RCTs about MgSO4 with original data on PPH prevalence were included in our systematic review. We calculated the relative risk of PPH in every study as well as an overall relative risk. Four relevant and valid RCTs were found, totalling 11,621 relevant patients. The relative risk of PPH in women treated with MgSO4 is 0.964 (95% CI 0.886 - 1.050) In this systematic review we found no significant increase in PPH in women treated with MgSO4. However, there is still room for discussion due to the heterogeneity in methods (dosage and duration of treatment), results, and tertiary outcomes, as well as the small number of studies found with respect to this important issue.

Effect of nifedipine combined with Magnesium Sulfate on oxidative stress,hemorheology,platelet active substances and renal function in patients with pregnancy-induced hypertension

Objective: To investigate effect of nifedipine combined with Magnesium Sulfate on levels of oxidative stress, blood rheology, platelet active substance and renal function in patients with pregnancy-induced hypertension. Methods: A total of 99 cases of patients with pregnancy-induced hypertension were selected as the study object, according to random data table, they were divided into control group (n=50) and observation group (n=49), patients in control group were treated with Magnesium Sulfate, while patients in the observation group received Magnesium Sulfate combined with nifedipine treatment, levels of blood pressure and oxidative stress, blood rheology, platelet activity and renal function index before and after treatment of both groups were compared. Results: There were no significant difference of the level of DBP, SBP, Tac, MDA, SOD, high/low shear blood viscosity, PV, HCT, CD62P, CD63, GPⅡb/Ⅲa, SCr and BUN before treatment between control group and the observation group. Compared with intragroup before treatment, the levels of DBP, SBP, MDA, high/low shear blood viscosity, PV, HCT, CD62P, CD63, GPⅡb/Ⅲa, SCr and BUN after treatment of the two groups were significantly decreased, and the levels of the observation group after treatment was significantly lower than those in the control group, the difference was statistically significant;Compared with level of SOD and Tac, after treatment, the levels of SOD and Tac of the two groups were significantly higher than those in the same group before treatment, and levels of the observation group was significantly higher than in the control group, the difference was statistically significant. Conclusion: Nifedipine combined with magnesium sulfate treatment of pregnancy-induced hypertension, which can effectively reduce the blood pressure level of patients, improve the levels of oxidative stress, blood rheology and platelet active substance, protect renal function, with an important clinical value.

Effect of nifedipine in combined with magnesium sulfate on the hemorheology and coagulation indicators in patients with gestational hypertension

Objective:To explore the effect of nifedipine in combined with magnesium sulfate on the hemorheology and coagulation indicators in patients with gestational hypertension.Methods:A total of 90 patients with gestational hypertension were included in the study and randomized into the observation group and the control group with 45 cases in each group. The patients in the observation group were given magnesium sulfate in combined with nifedipine, while the patients in the control group were only given magnesium sulfate. The patients in the two groups were continuously treated for 2 weeks. The blood pressure, hemorheology indicators, and coagulation indicators before and after treatment in the two groups were detected and compared.Results: SBP, DBP, whole blood high, moderate, and low shear viscosity, plasma viscosity, and HCT after treatment in the two groups were significantly reduced when compared with before treatment (P<0.05). The levels of the above indicators after treatment in the observation group were significantly lower than those in the control group (P<0.05). PT, APTT, and TT after treatment in the two groups were significantly elevated when compared with before treatment (P<0.05), while Fib was significantly reduced (P<0.05). PT, APTT, and TT after treatment in the observation group were significantly higher than those in the control group (P<0.05), while Fib was significantly lower than that in the control group (P<0.05). Conclusions:Nifedipine in combined with magnesium sulfate can significantly stabilize the blood pressure level in patients with gestational hypertension, and improve the hemodynamic and coagulation indicators, with a significant efficacy.

Attack of Limestone Cement-based Material Exposed to Magnesium Sulfate Solution at Low Temperature

Limestone in cement could be a source of CO3^2- needed for thaumasite formation which will result in thanmasite form of sulfate attack （TSA） probably. TSA has more deterioration than ettringite or gypsum form of sulfate attack because it targets the calcium silicate hydrates （C-S-H） which is the main binder phase in all Portland cement-based materials. By means of physical and mechanical property testing as well as erosion phases analysis, magnesium sulfate attack of cement-based material containing 35% limestone powder by mass at 5 ± 2 ℃ is investigated. The compressive strength and flexural strength of mortar specimen immersed in MgSO4 solution increase firstly, then decrease rapidly with the immersing age. Relative dynamic elastic modulus of mortar specimen changes in a phased process. After immersing in MgSO4 solution for 15 weeks, the main erosion phases in paste specimen change from four phases compounds, three phases compounds to two phases compounds from surface to inside. Deterioration course of limestone cement-based material exposed to magnesium sulfate aggressive environment appears progressive damage layer by layer, and every layer probably suffers four stages, which are property strengthening stage, initial degradation stage, thaumasite formation stage and cementation loss stage, respectively.

Ab Initio and DFT Study of Magnesium Sulfate Contact Ion Pairs

The stuctures of contact ion pairs of magnesium sulfate were studied. The geometries of contact ion pairs of MgSO 4(H 2O) n (n =1-6) were optimized by using Hartree Fock (HF/6 31+G *, HF/6 311+G ** ) and density functional theory (DFT) (B3LYP/6 31+G *, B3LYP/6 311+G ** ) methods. The stable structures of monodentate, bidentate and tridentate contact ion pairs were obtained. The bidentate structure of contact ion pairs are the most stable compaired with the monodentate and tridentate ones for the same composition. The hydration enthalpies of contact ion pairs of MgSO 4 (H 2O) n (n =1-4) increase with their hydration numbers.

The Effects of Magnesium Sulfate on Fetal Rats of FGR and the Expression of Caspase-3 in the Placenta of Maternal Rat

To investigate the effect of magnesium sulfate on the fetal rats of FGR and the expression of caspase-3 in the placenta of maternal rat ; To explore the mechanism of using magnesium sulfate to cure the FGR. Establish model of FGR by a way of passive smoking： giving the maternal rats different agent of magnesium sulfate by subcutaneous injection： low agent group （300 mg/kg）, high agent group （600 mg/kg）. Concentration of magnesium sulfate was monitored. The expression of caspase-3 was measured by RT-PCR and immunohistochemistry technology. Both of the concentrations of magnesium sulfate in high and low agents group are higher than the FGR group （P〈0.01）;the weight of the placenta and fetal rat in high agent group are higher than the FGR group （P〈0.05 and P〈0. 01） ; the expression of mRNA and protein of caspase-3 in the two agent group is higher than the FGR group （P〈0.05 respectively） ; concentration of magnesium sulfate in the maternal rat blood correlate to the weight of fetal rat （r=0. 899, P=0. 038） and the expression of caspase-3 in the placenta of maternal rat （r=-0. 747, P=0. 033; r=-0. 915, P=0. 001）. The research suggests that the weight of fetal rat could be increased by treatment of magnesium sulfate. Because it would imfrmove the placental function by depressing the expression of caspase-3.

Comparative effect of intrathecal meperidine,tramadol,magnesium sulfate,and dexmedetomidine on preventing post-spinal anesthesia shivering and adverse events in hip fracture repair patients:A randomized clinical trial

Objective:To compare effect of intrathecal meperidine,tramadol,magnesium sulfate,and dexmedetomidine on the prevention of post-spinal anesthesia shivering and adverse events in hip fracture repair patients.Methods:In a randomized,double-blind trial,132 patients with American Society of Anesthesiology(ASA)ⅠandⅡspinal anesthesia who needed hip fracture surgery were enrolled.Patients were stratified into 4 intervention groups based on a randomized block pattern:meperidine,tramadol,magnesium sulfate,and dexmedetomidine.Hemodynamic parameters including blood pressure,heart rate,and oxygen saturation,as well as the severity of shivering,core body temperature,Ramsay sedation score,adverse events,meperidine consumption were recorded and compared.Results:There was no statistically significant difference in the normal hemodynamic parameters,temperature,duration of surgery,meperidine consumption,and adverse events such as dizziness,hypotension,nausea,and bradycardia among groups(P>0.05).Compared to other groups,severity of shivering was the lower in the dexmedetomidine group 6 and 8 h after surgery.The Ramsay sedation scores were higher in the dexmedetomidine and meperidine groups 4 h after surgery(P=0.020).Conclusion:Dexmedetomidine acts better than the other three adjuvants in reducing complications such as shivering.Overall,these four adjuvants are helpful to prevent postoperative shivering and could be put forward as promising local anesthetics in spinal anesthesia,based on anesthesiologists’discretion and patients’general conditions.Clinical registration:The study was approved by the Research and Ethics Committee at the Valiasr Hospital(Arak,Iran)with the clinical trial code of IRCT20141209020258N153.

Comparison of impact of adjuvant treatment of midazolam, fentanyl, and magnesium sulfate with intrathecal bupivacaine on block characteristics and postoperative analgesia in knee arthroplasty: A randomized clinical trial

Objective:To compare the efficacy of midazolam,fentanyl,and magnesium sulfate as adjuvants to intrathecal bupivacaine on both block characteristics and postoperative analgesia in knee arthroplasty.Methods:This randomized double-blind clinical trial recruited spinal anesthesia patients of the American Society of Anesthesiologists classⅠorⅡ,who needed knee arthroplasty.Patients were stratified into three intervention groups,including the midazolam group,the fentanyl group,and the magnesium sulfate group,and the patients were administered with midazolam,fentanyl,and magnesium sulfate,respectively.Hemodynamic parameters,sensory and motor block,and pain score(Visual Analogue Scale)were measured and compared among the three groups.Results:A total of 105 patients were included in this study with 35 patients in each group.There was no statistically significant difference in terms of oxygen saturation,mean blood pressure,duration of surgery,and postoperative complications,including nausea,vomiting,bradycardia,dizziness,and hypotension,as well as the time of opioid administration among the three groups(P>0.05).Statistically significant differences were found in terms of heart rate at 15,30,45,60,75,and 105 min after beginning of operation among the three groups,which was lower in the midazolam group(P<0.05).The midazolam group showed a shorter time to achieve sensory block after spinal anesthesia,sensory block to T8 or higher and sensory block to T12 and L1(P<0.05).Besides,the three groups showed significantly differences in terms of onset of motor block after spinal anesthesia and time to achieve motor block to T8 or higher or Bromage score 3(P=0.001).No significant difference was noted in pain scores among the three groups(P>0.05).Conclusion:Midazolam resulted in a shorter time to achieve sensory and motor block to T8 or higher,the onset of motor block and sensory block after spinal anesthesia,and time to achieve sensory block to T12 and L1,and the pain scores were not significantly different among the groups.Thus,midazolam can be highly underlined,if a shorter onset of sensory and motor blocks is targeted.[Funded by the research deputy of Arak University of Medical Sciences(No.99258);fa.irct.ir number,IRCT20141209020258N164].

Magnesium Sulfate Effect on Fetal Umbilical Artery and Middle Cerebral Artery Doppler Indicies in Women with Severe Preeclampsia and Eclampsia

Objective: To study MgSO4 effect on fetal MCA and UA blood flow changes using Doppler ultrasound in cases of severe PET and eclampsia. Materials and Methods: A total of 40 patients with severe PET admitted to El-Shatby Maternity University Hospital, Alexandria (Egypt) were examined before and after administration of MgSO4 using Doppler study to measure fetal MCA and UA blood flow changes. Results: After administration of MgSO4, the mean RI of UA, PI of UA showed a statistically significant decrease (P < 0.001) also the systolic-diastolic ratio (p = 0.001). Mean resistivity index (RI) cerebral showed a statistically significant increasing (P = 0.001), pulsatility index (PI)-cerebral and the systolic-diastolic ratio showed a statistically significant increasing (P < 0.001). The C/U (cerebroumblical) ratio increased after the treatment (P < 0.001). Conclusions: Infusion of MgSO4 significantly decreases the fetal RI, PI, SDR umbilical and increases the fetal RI, PI, SDR MCA and increases cerebroumblical ratio indices obtained by Doppler examinations.

The Impact of Adding Magnesium Sulfate to Bupivacaine versus Bupivacaine Alone in Fascia Iliaca Compartment Block in Burn Patients Undergoing Skin Grafting Procedures;Comparative Study

Purpose: The purpose of the study is to evaluate the analgesic effect of adding magnesium sulfate to bupivacaine in Fascia Iliaca Compartment Block (FI-CB). Patients and Methods: Ninety-six burn patients scheduled for skin-grafting procedures were allocated into two equal groups. After induction of general anaethesia, forty-eight patients received US guided FICB using 35 ml bupivacaine 0.25% + 5 ml isotonic sodium chloride solution with a total volume of 40 ml. The other forty-eight patients received 35 ml bupivacaine 0.25% + 250 mg of magnesium sulfate with a total volume of 40 ml. Results: Total postoperative pethidine consumption in the first 24 h post-operative showed a highly statistically significant decrease in the magnesium group in comparison to the bupivacaine group. Conclusion: Adding magnesium sulfate to bupivacaine in FICB in skin grafting procedures decreased the pain scores post-operative, delayed the first request of analgesia and reduced the total analgesic consumption in the first 24 h post-operative without any significant side effects.

Preparation of Adsorbent with Magnesium Sulfate and Straw Pulp Black Liquor and Its Phenol Adsorption Properties

A magnesia adsorbent was prepared from straw pulp black liquor and magnesium sulfate for the first time, and its adsorption of phenol from aqueous solution was examined. The characteristics of the adsorbent were tested through chemical analysis, surface analysis, X-ray diffraction and FT-IR spectroscopy. The effects of various factors, such as dose, adsorption time and adsorption temperature, on phenol adsorption behavior were studied. The results show that the adsorption processes can be fitted to the isotherm Langmuir model very well. It was found that the adsorption process was strongly influenced by temperature and the optimal temperature for phenol removal was 40 ℃. The optimum adsorption time was 10 min, and desorption would happen afterwards. Between the models of Langmuir and Freundlich, the adsorption process of phenol onto magnesia fitted the Langmuir equation better.

Effect of magnesium sulfate combined with labetalol on the apoptosis and invasion molecule expression in placenta as well as maternal endothelial function of patients with severe preeclampsia

Objective: To investigate the effect of magnesium sulfate combined with labetalol on the apoptosis and invasion molecule expression in placenta as well as maternal endothelial function of patients with severe preeclampsia. Methods: A total of 68 patients with severe preeclampsia who were treated in the hospital between October 2015 and August 2017 were chosen as the research subjects and divided into study group (n=34) and control group (n=34) by random number table method. Control group received magnesium sulfate therapy on the basis of conventional therapy, and study group received magnesium sulfate combined with labetalol therapy on the basis of conventional therapy. The differences in the expression of apoptosis and invasion molecules in placenta tissue as well as the levels of maternal endothelial function indexes were compared between the two groups. Results: Fas, Bax and Caspase-3 mRNA expression in the placenta tissues of study group were lower than those of control group whereas Bcl-2 mRNA expression was higher than that of control group;GPR30, LAMA4 and MEST mRNA expression in placenta tissues were lower than those of control group whereas CDKN1C mRNA expression was higher than that of control group;24 h before delivery, maternal serum ET-1 and vWF levels of study group were lower than those of control group whereas NO level was higher than that of control group (P<0.05). Conclusion: Magnesium sulfate combined with labetalol therapy can effectively inhibit the apoptosis of placental trophoblast cells and enhance their invasion ability, and also improve the maternal endothelial function in patients with severe preeclampsia.

Physicochemical Study on the Interface Zone of Concrete Exposed to Different Sulfate Solutions

This paper reports the results of the visual observations and micro-analysis of concrete core samples after 6 and 12 months of their exposure to sodium, ammonium and magnesium sulfate solutions with the same concentration of sulfate ions. XRD, SEM and EDS were used for micro-analysis of the microstructure and the composition of the interface zone in the samples. The results indicate that the deterioration of concrete by different sulfate solutions could proceed differently with regard to the mechanism and the mode of damage caused. The damage of concrete exposed to sodium sulfate solution is mainly caused by the gypsum crystals formed in the interface zone, which lead to expansion and cracking. In the case of concrete immersed in magnesium sulfate solutions, a layer of brucite (magnesium hydroxide) and gypsum was produced in the interface zone, which reduces the cohesiveness of the interface zone in concrete. For the concrete immersed in ammonium sulfate solutions, the conversation of mortar to some mush mass by ammonium ions and the formation of a large of gypsum occurred in the interface zone, consequently, serious softening of hydrated cement pastes and expansion and cracking of concrete are the characteristics of the attack by ammonium sulfate solutions. Also, it is considered that using drilled concrete core as samples to evaluate the sulfate resistance of concrete is a good and accelerated method.

硫酸镁侵蚀作用下高流态水泥砂浆的早期强度劣化特征

高流态早强(HFES)水泥砂浆被广泛应用于土木工程的各个领域。在复杂的工程环境下,HFES水泥砂浆的硫酸盐侵蚀不容忽视。尽管硫酸盐对水泥基材料性能的影响已有一些研究,但HFES水泥砂浆与传统水泥基材料相比有明显不同,其在硫酸盐侵蚀情况下的劣化机制尚不明确。本文研究了不同硫酸镁溶液浓度和侵蚀时间下HFES水泥砂浆的早期抗折和抗压强度,通过扫描电镜(SEM)、X射线衍射(XRD)和差示扫描量热仪(DSC)测试,分析了硫酸镁溶液浓度和侵蚀次数对HFES水泥砂浆微观结构和水化产物的影响,揭示了硫酸镁对HFES水泥砂浆早期强度形成的影响机制。