Influence Of Cement Content Research Articles

Study of the Design and Mechanical Properties of the Mix Proportion for Desulfurization Gypsum–Fly Ash Flowable Lightweight Soil

In order to solve the global problem of bridge head jumping caused by the insufficient compaction of the roadbed in the transition section of highways and bridges, a desulfurization gypsum–fly ash flowable lightweight soil without vibration, capable of self-compaction, low bulk density, and economic and environmental protection, has been developed. This study selected low-grade cement, industrial waste (fly ash and desulfurization gypsum), and Yellow River silt as the raw materials for the design of the mix ratio of a desulfurization gypsum–fly ash flow-state lightweight soil mix. Through multiple indoor experiments, the influence of cement content, silt content, and the fly ash/desulfurization gypsum quality ratio on its fluidity and mechanical properties was systematically studied. The stress–strain relationship under uniaxial compression was analyzed and the strength formation mechanism was revealed through scanning electron microscopy (SEM). The results show that the mechanical properties of the prepared desulfurization gypsum–fly ash flowable lightweight soil meet the engineering requirements. Increasing both the cement and fly ash content results in the decreased fluidity of the desulfurization gypsum and fluidized fly ash. However, as the mass ratio of fly ash to desulfurization gypsum increases, the fluidity reaches its maximum when the mass ratio of fly ash to desulfurization gypsum is 2:1. Based on the stress–strain relationship test results, a uniaxial compressive constitutive model of the desulfurization gypsum–fly ash flowable lightweight soil was proposed. The model was fitted and analyzed with the test results, and the correlation was greater than 0.96. The high degree of agreement showed that desulfurization gypsum can promote the disintegration of fly ash, thereby increasing the specific surface area. This provides more contact points, promotes the hardening process, and enhances the interlocking force between particles and the formation of cementitious substances, further enhancing strength.

Research on the Relationship between Pore Structure and the Compressive Strength of Oil-Well Cement

The integrity of wellbore cement is an important guarantee for the long-term safety and effectiveness of carbon dioxide geological storage. During the process of CO2 capture, utilization, and storage, construction factors will cause changes in temperature and pressure distribution, leading to changes in the pore structure of cement and a decline in compressive strength, which can easily cause the failure of cement ring integrity. To provide theoretical guidance and analysis methods for evaluating the mechanism of cement strength performance degradation and optimizing injection parameters, in this study, we conducted the following research based on relevant studies: (1) The fracture theory was revised based on the characteristic factors of oil-well cement; (2) a pore structure model was established to analyze the failure process of cement, clarifying the relationship between pore structure and the compressive strength of cement; (3) the parameters of the pore structure model were determined and analyzed, considering the influence of cement content and total porosity on the model, and finally, the regression parameter K value was determined to be 1600. This article can provide a useful reference for the research on the failure of cement rings in the CO2 injection process and other related studies.

Influence of Cement Content and Compaction Pressure on the Mechanical Properties of Sandcrete Blocks

Influence of Cement Content and Compaction Pressure on the Mechanical Properties of Sandcrete Blocks

Soil-cement formation factor: methodological approach and relationship with unconfined compression strength

This study investigated the use of the Formation Factor of the material as an alternative way to estimate soil-cement strength involving no destructive tests. This factor is obtained from Archie’s Law and consists of the ratio of pore water electrical conductivity to saturated porous material electrical conductivity, being related to porosity by constant terms. In this study, the electrical conductivity of the pore solution was obtained from a soil-cement leaching test after curing, and the conductivity of the monolithic soil-cement, by applying continuous voltage between 12-35 V onto electrodes of 1 mm thick copper plates. The influence of cement content and dry density on the electrical properties and water absorption was studied and discussed for curing times of 7 and 28 days. The samples molded with higher dry densities and cement contents presented higher Formation Factor for Soil Cement and higher unconfined compression strength. The Formation Factor and the unconfined compression strength are linearly related. Due to the methodology adopted, the Formation Factor was predominantly influenced by the conductivity of the pore solution and was related to the open porosity by means of a power function. Therefore, the Archie’s Law can be applied to soil-cement. In this case, the cementation coefficient varies until 28 days of curing, tending to stabilize around 8 from that age onwards. The volumetric coefficient can be adopted as a constant with a value of 1012.

Analysis of Mechanical Properties of Loess with Cement Incorporation Ratio

Taking loess as the research object, the influence of cement content on mechanical properties of loess was studied. Firstly, the basic physical parameters of loess were obtained through laboratory physical index test, and improved by using Portland cement. Secondly, under different incorporation ratios (3%, 5%, 7%, 9%), heavy compaction test and liquid-plastic limit test were carried out respectively to obtain mechanical parameters of cement-improved loess. Finally, the shear strength parameters and compressive strength of the improved soil samples are obtained by unconsolidation undrained triaxial shear test and unconfined compressive strength test. The results show that the liquid limit, plastic limit and plastic index of loess improved by adding cement increase compared with the original soil sample, indicating that the binding force between soil particles is improved and the plasticity is enhanced. The variation range of dry density and water content has no obvious relationship with the content of cement. At the same time, the compressibility of soil is reduced and the collapsibility of soil is eliminated. With the increase of age, the strength of cement-modified soil also increases. Through unconsolidated and undrained triaxial shear tests and unconfined compressive strength tests, the strength of loess improved significantly after adding cement, and the strength of soil-cement increased with the increase of cement content, and water stability was obviously improved.

Road performance analysis of cement stabilized coal gangue mixture

In order to solve the environmental pollution of coal gangue and the shortage of aggregate resources in road engineering, waste coal gangue is used as road base material instead of natural stone materials. Through physical, mechanical, chemical and activity tests of coal gangue aggregate, the optimal gradation composition of unconfined compressive strength was determined. Through unconfined compressive strength, indirect tensile strength, flexural tensile strength, freeze-thaw and dry shrinkage tests, the influence of cement content on road performance of cement stabilized coal gangue mixture was studied. By means of SEM, ICP AES, XRD and optical digital microscope, the difference between spontaneous combustion coal gangue and Unspontaneous combustion coal gangue was analyzed, the microstructure of cement stabilized coal gangue mixture was characterized, and the strength formation mechanism of mixture was explored. The results show that Spontaneous combustion coal gangue has higher activity than Unspontaneous combustion coal gangue. Based on the selected optimal allocation (BNS:SNS:SSC = 71.26:9.41:18.8). The mixture of 4% cement dosage can not only meet the requirement of early strength 4.16 MPa, but also show an efficient strength growth rate of 36.10%, showing the optimum mechanical properties. The total shrinkage coefficient of cement stabilized coal gangue mixture with 4% cement dosage is 1.12 × 10−2, which shows that the dry shrinkage resistance is the best. With the increase of time, hydration degree is gradually deepened, and gelled substance is more tightly bonded to aggregates. There is no obvious gap between aggregates, and the integrity of the mixture is enhanced, which can show better road performance. Ca (OH)2, a cement hydration product in cement stabilized coal gangue mixture, takes place pozzolana reaction with active SiO2 and Al2O3 in coal gangue to produce gismondine, which is beneficial to the global strength and the bond quality of the mixture.

Research on Mix Design of Cement Stabilized Recycled Aggregate Pavement Base

In this paper, the compaction test of the mixture with different cement content and different replacement rate of recycled aggregate is studied by vibration compaction method. Through the research on the mix design of cement stabilized recycled aggregate pavement base, the optimum content of cementitious materials is determined, and the maximum dry density and optimum water content of each test scheme are obtained. The influence of cement content and recycled aggregate content on the maximum dry density and optimum water content of the mixture is analyzed.

Unconfined compression strength of an artificially cemented aeolian dune sand of Natal/Brazil

Abstract Soil behavior is influenced by the void ratio and bonds between grains. The aim of this study was to describe the strength behavior of an aeolian sand from the dunes of Natal, Brazil, artificially cemented in unconfined compression tests. The influence of cement content and moisture on molding and the validity of using the void/cement factor in estimating unconfined compression strength (UCS) were assessed. Tests were conducted with samples using three molding moisture contents (6, 9 and 12%), four cement contents (2.5, 5.0, 7.5 and 10%) and a void ratio of 0.6 (Dr = 95%). The results showed that unconfined compression strength rises with increase in cement content and decreasing in molding moisture. The void/cement factor proved to be a reliable parameter in predicting the behavior of sand from Natal for the dosage of soil cement.

Investigation on cement-improved phyllite based on the vertical vibration compaction method.

The vertical vibration compaction method (VVCM), heavy compaction method and static pressure method were used to form phyllite specimens with different degrees of weathering. The influence of cement content, compactness, and compaction method on the mechanical properties of phyllite was studied. The mechanical properties of phyllite was evaluated in terms of unconfined compressive strength (Rc) and modulus of resilience (Ec). Further, test roads were paved along an expressway in China to demonstrate the feasibility of the highly weathered phyllite improvement technology. Results show that unweathered phyllite can be used as subgrade filler. In spite of increasing compactness, phyllite with a higher degree of weathering cannot meet the requirements for subgrade filler. With increasing cement content, Rc and Ec of the improved phyllite increases linearly. Rc and Ec increase by at least 15% and 17%, respectively, for every 1% increase in cement content and by at least 10% and 6%, respectively, for every 1% increase in compactness. The higher the degree of weathering of phyllite, the greater the degree of improvement of its mechanical properties.

Strength and deformation behaviors of cemented tailings backfill under triaxial compression

It is of great significance for safety reason to obtain the triaxial compressive properties of cemented tailings backfill(CTB). The influence of cement content, curing age and confining pressure on strength and deformation properties of CTB was examined and discussed. Results indicate that the triaxial compressive and deformation behavior of CTB is strongly affected by the cement content, curing age and confining pressure. The increase in cement content, curing age and confining pressure leads to a change in stress-strain behavior and an increase in the axial strain at failure and post-peak strength loss. The cohesion of CTB rises as the curing age and cement content increase. However, the enhancement in internal friction angle is trivial and negligible. It should be noted that the failure pattern of CTB samples in triaxial compression is mainly along a shear plane, the confining pressure restrains the lateral expansion and the bulging failure pattern is dominantly detected in CTB samples as curing age length and cement content increase. The results will help to better understand the triaxial mechanical and deformation behavior of CTB.

Influence of cement content and maximum aggregate size on the fracture parameters of magnetite concrete using WFM, SEM and BEM

Fracture behavior is an important issue that should be taken into account in analysis and design of important concrete structures such as nuclear power plants. The fracture behavior of concrete is dependent on its constituents. Thus, due to the application of heavyweight aggregates with high densities in heavyweight concrete (HWC), the structure and fracture behavior of this type of concrete will be different from normal concrete. In this experimental research, the effects of maximum aggregate size (MAS = 12.5, 19, 25 mm), cement content (350, 400 kg/m3) and water to cement ratio (w/c = 0.45, 0.65) on the fracture parameters of heavyweight magnetite concrete were studied using three methods: Work of Fracture Method (WFM), Size Effect Method (SEM) and Boundary Effect Method (BEM). The results show that with increasing MAS, fracture energy and ductility increase and this trend is more obvious for lower cement contents and water to cement ratios. In addition, peak loads of heavyweight concrete beams can be acceptably estimated using initial fracture energy (Gf). It was also found that size independent fracture energy values obtained by BEM and Elices et al. methods are close to each other.

Strength evaluation of marine clay stabilized by cementitious binder

Evaluation of the strength of cement-treated clay with a broad range of mix ratios and curing periods was conducted using unconfined compression tests (UCTs). The influence of cement content, total water content, and curing period on the unconfined compressive strength of cemented clay are investigated. It is found that, at constant total water content, higher cement content results in higher unconfined compressive strength, while the total water content has an opposite effect. A power function can be used to correlate the unconfined compressive strength with the cement content or the total water content. For a fixed mix ratio, the unconfined compressive strength of cement-stabilized clay increases with the curing period, the effect of which can be characterized by a semi-log formula. Also, a strength-prediction model that considers both mix ratios and curing periods for cement-admixed marine clay is developed and validated; the model can capture the effect of clay type by considering the plastic index of untreated soils. It is also proved that the proposed framework for strength development is also applicable for other cement types.

Study on Unconfined Compressive Strength of High Volume Cement Stabilized Macadam

This paper mainly studies the effects of different cement content (5%, 7%, 9%, 11%, 13%, 15%) on the unconfined compressive strength of cement stabilized macadam base materials. The effects of different cement content on the compressive properties of the mixture were compared by unconfined compressive strength test analysis. The results show that the influence of cement content on the early strength of the road base layer is greater than the impact on the later strength. When the age is 1 day, the cement content increases from 9% to 11%, and the unconfined compressive strength increase rate of the test piece is the largest (35.93%).

Experiment Investigation and Physical Performance of Geopolymer Fly Ash Bricks

In India an approximate 400-500 million metric tons of fly ash are generated annually from thermal power plant. Maximum use of fly ash is necessary for the sustainable development. In this research, an attempt has been made to develop a method for manufacture of bricks using fly ash geopolymer technology. The influence of cement content in geopolymer fly ash based bricks has been studied. The fly ash, cement, silica fumes mixed with 2 molar of alkaline solution with varying cement content from 0% to 15% and heat curing at 100°C for 24 hours. Bricks were tested for compressive strength, flexure strength, water absorption, efflorescence. The compressive strength, flexure strength of the bricks increases with increase in with cement content up to certain limit then decreases. Efflorescence of bricks are slight as per IS1077:1992. Water absorption of geopolymer fly ash bricks are within limit as per IS1077:1992.

Interface behavior of tensioned bars embedded in cement-soil mixtures

The overall performance of reinforced cement-stabilized soils depends significantly on the interface bond mechanisms that develop between the reinforcement and the surrounding cement-soil mixture. A laboratory experimental investigation based on uniform design theory was carried out to characterize the interface behavior of deformed bars embedded in cement-admixed soils. The study focused on the influence of cement content, water content and curing duration on the interface response. The interface bond strength of reinforced cement-soil mixture, as measured in pullout tests, was found to be proportional to the strength of cement-soil matrix, as obtained from unconfined compression tests. A simplified trilinear bond-slip model was developed as part of this study, which when properly calibrated was found to be capable of characterizing the bar-mixture interface shear response. Correlations were obtained to relate the interface bond strength with the three influence factors investigated in this study. The trends obtained on the influence of each factor on the interface bond resistance provided insights that were suitable to guide current design and construction practice of reinforced cement-soil mixture. The results and testing protocols presented in this study facilitated the understanding for interface shear mechanism between deformed bar and cement-soil mixture, and are expected to provide adequate means to satisfy the current lack of bar-mixture interface bond parameters in design specification for reinforced soil mixing structures.

Effects of cement content and grain-size composition on engineering properties of high-speed-railway macadam subgrade

Cement-stabilized macadam (CSM) is being used in high-speed railway (HSR) subgrade in seasonal frozen regions in China. This study conducted a series of tests to determine the characteristics of HSR CSM subgrade in cold regions. In particular, the influence of cement content and grain-size composition on the compaction effect, frost heave property, permeability, freeze–thaw durability, and shrinkage property of macadam subgrade were analysed. The results show that the compaction quality indexes of CSM subgrade satisfy and even exceed the compaction quality standards for HSR subgrade. Removal of soil particles smaller than a certain size weakens the frost heave sensitivity, improves permeability, and reduces the unconfined compressive strength (UCS) and moisture stability of CSM. Cement addition effectively compensates for the reduction in UCS; however, it increases the shrinkage deformation of CSM. The temperature and dry shrinkage coefficient of CSM increase with cement content. The shrinkage properties of CSM subgrade are the least favourable in the temperature range −10°C to 10°C. The UCS first decreases with increase in the number of freeze–thaw cycles and then becomes stable after 10cycles. In the engineering practice of HSR subgrade in seasonal frozen regions, in a subgrade where permeability is not a necessary characteristic, CSM with 3% fines content and 3% cement addition is suitable, and in a subgrade where permeability is a necessary characteristic, CSM with grains larger than 0.5mm and 3% cement addition is suitable.

Influence of cement content and environmental humidity on asphalt emulsion and cement composites performance

Asphalt and cement concrete are the most popular materials used in the construction of roads, highways, bridge deck surface layers and pavements in airports and other areas with heavy wheel roads. Whereas asphalt possesses, compared to concrete, the advantages of a short curing period, high skid resistance and easy maintenance, it also shows lower fatigue durability, ravelling and rutting due to repeated concentrated loads and susceptibility to temperature changes and moisture. On the other hand, concrete pavements are initially more expensive, have lower driving comfort and are susceptible to cracking due to volume changes and to salt damage. A material with low-environmental impact and with advantages of both asphalt and concrete may be obtained by combining bitumen emulsions and a cementitious material. In this paper, cold asphalt mixtures with different amounts of cement were tested with Marshall stability tests. Selected mixtures were also cured at different environmental relative humidity (35, 70 and 90 % RH). By monitoring the mass of the specimens and estimating the water bound by the cement, the total water remaining in the mixtures was calculated. Details of the microstructure in the mixtures were examined with X-ray microtomography. According to the results of the present study, cement contributes to the hardening of cold asphalt mixtures both by creating cement paste bridges between the aggregates and by removing water from the mixtures through cement hydration. Asphalt and cement composites appear to be promising materials for implementation in real pavements, although their rate of hardening needs to be improved further.

Analysis for Influence Factors of Cold Recycling Mixture Compaction Test

In order to study the factors which influence the inorganic binder stabilized material’s compaction test results, different recycled material content therefore different reclaimed gradation mixtures are tested while varying the amount of cement. The experiment results show that contents of the recycled base material and the recycled surface material on the compaction test results are determined by the change of their density and water absorption ratio. Dry density of the recycled mixture increases with the increase of the reclaimed base material density. Low water absorption ratio of the recycled material reduces the reclaimed mixture’s optimum moisture content. Density of the reclaimed wearing surface material reduces the maximum dry density of the reclaimed mixture because the old wearing surface material has lower density. Its low water absorption reduces the optimum moisture content of the recycled mixture. Influence of cement content on compaction test results is the increase of the cement content can enhance the maximum dry density and optimum moisture content of the recycled material. Through the analysis of the results of the compaction test, the key factors in the recycled material compaction test are unveiled.

Effectiveness of the traditional parameters for specifying carbonation resistance

This paper presents data on carbonation measurements taken from a range of test specimens stored outside but protected from rainfall. A wide range of concretes were tested that were representative of UK ready-mixed concrete production at ages of between 3·5 and 5·7 years. None of the traditional specification parameters (maximum water/cement (w/c) ratio, minimum cement content and compressive strength class) on their own or in combination give a consistent carbonation resistance. When compared at a fixed w/c ratio of 0·55, there was no clear influence of cement content on carbonation resistance. The measured carbonation depths of the Portland cement concretes were too low to show any influence of aggregate type. When extrapolated to 35 years, in a conservative manner, the data provide no grounds for concern with the BS 8500-1 recommendations with respect to carbonation resistance. There is some indication that the BS 8500-1 recommendations with respect to CEM I concretes may be too conservative. The predicted performance of concrete containing 40% or more fly ash indicates that the particular recommendations set out in BS 8500-1:2006 are justified.

Influence of cement content on corrosion resistance

The minimum cement content requirement given in codes of practice over the years to ensure durability of concrete is being increasingly questioned. Of all the durability problems related to concrete structures, corrosion of reinforcing steel is the single most prevalent deteriorating process. This paper describes a study undertaken to determine the influence of variation in cement (binder) content at fixed water/cement ratio on carbonation- and chloride-induced reinforcement corrosion. Cement (binder) content was varied above and below the limits given in current European standards in the tests. The fines content (particles < 75 μm) of some cement-reduced mixes was maintained with the inclusion of a limestone filler as part of the sand content. The results indicate that cement reduction below the given minimum cement contents in current standards has insignificant influence on the overall carbonation-induced reinforcement corrosion process. Moreover, cement content has very little influence on the overall chloride-induced reinforcement corrosion process except the possible better performance of cement-reduced concrete with filler. It is suggested that the attention traditionally given to minimum cement content in determining reinforcement corrosion resistance may be disproportionate to the effective influence of this parameter.