Addition Of Cement Research Articles

Effect of Modifying Aggregates by Rap and the Simultaneous use of Adhesives for the Stabilization of a Sandy Pavement Subgrade

Abstract The improvement, reconstruction and repair of roads in recent years have increased the content of recycled asphalt in pavements. Using these materials in road construction projects because they reduce the costs, will also be of great help in improving environmental issues. In the present study, dune sand, which can be found in most desert area soil but does not have proper strength and loading capacity for a subgrade, was used. In order to increase the strength parameters of dune sand, various contents of cement and recycled asphalt were examined in California Bearing Ratio (CBR) and compressive strength tests. The results showed that the addition of cement and recycled asphalt can increase compressive strength and bearing capacity and reduce rupture deformations. In a stabilized sample with 27.5% recycled asphalt, increasing the cement from 7.5 to 12.5% increased the compressive strength by 1.045 times, which is the highest amount of change in the samples studied. The maximum CBR and minimum rupture deformations are related to 35% of the recycled asphalt and 12.5% of the cement. The predicted functions of the compressive strength, deformation and CBR depend on two variables of the cement content; the recycled asphalt was then calculated using the response surface method

Improvement of the technology of cold reclamation of asphalt concrete in the asphalt plant and the possibility of its application in the republic of Iraq

This article presents the state of the highways in the Republic of Iraq and studying the possibility of using the regeneration technology of asphalt concrete as a base for road pavements strengthen. This technology has not yet used in Iraq. Therefore it proposed to use for the maintenance and reconstruction of roads the technology of cold regeneration of asphalt concrete in the asphalt plant, which ensures the improvement of the properties of asphalt granules due to its preliminary crushing, the introduction of cement additives as a mineral binder. Compositions of asphalt-granular-concrete mixtures have developed, and data from studies of the properties of asphalt-granular-concrete of various documents presented. The most common pavement defects in Iraq are plastic deformations, which are caused by a combination of high temperatures and low strength characteristics of asphalt concrete. Pregame compositions used to strengthen the construction of road pavements with increased strength and shear stability. A cost-effectiveness calculation of using the cold technique is also presented moreover compare the cost this application in Russia and Iraq also.

Working Mechanisms and Design Principles of Comb-like Polycarboxylate Ether Superplasticizers in Cement Hydration: Quantitative Insights for a Series of Well-Defined Copolymers

Cement and concrete are the most widely used building materials and contain comb copolymers such as polycarboxylate ethers (PCEs) as hydration and setting modifiers. The working mechanisms of these additives in cement hydration have remained uncertain, which limits the rational design of additives and of new cement materials with lower CO2 footprint. We identified quantitative correlations between PCE copolymer structure, adsorption, and cement setting properties for a series of copolymer structures and concentrations, combined with insights into conformations and adsorption mechanisms by atomistic simulations. The PCE copolymers have only a small fraction of polydispersity compared to earlier studies, and molecular dynamics simulations utilize Interface force field models for C-S-H phases that enable order-of-magnitude more accurate insights into the dynamics of the nanoscale polymer interfaces compared to earlier models. Two distinct sets of property correlations were discovered. (1) The carboxylate content of the PCEs, i.e., the molar density of ionic side groups per unit mass, correlates with the adsorbed amount of polycarboxylate ethers onto cement pastes, the conductivity of the cement paste, and the retardation of the acceleration period of cement hydration. (2) The combination of the ionic character of the polymer backbone and the length of non-ionic polyethylene glycol (PEG) side chains correlates with the water-to-cement ratio necessary for processing, zeta potentials, and fluidity of the cement pastes in mini slump tests. Simulations indicate that PCE adsorption onto cement particles involves migration of calcium ions in the acrylate backbone onto the calcium silicate hydrate surface, or calcium hydroxide surfaces, followed by ion pairing of the anionic polymer backbone with the positively charged mineral surface. PEG side chains exhibit no affinity to the mineral surface. The best fluidity and water reduction are achieved using an optimum ratio of the volume of PEG side chains to the volume of the anionic backbone, balancing sufficient surface bonding through the ionic backbone and minimization of interparticle forces by the non-ionic PEG side chains. A charge density too low prevents effective adsorption, and a charge density too high leads to multilayer deposition and ionic agglomeration forces between coated particles that reduce the fluidity and increase the necessary water-to-cement ratio. The proposed mechanism supersedes prior models and provides quantitative metrics for the rational design of polymer additives for cement and related particle dispersions.

Development of a constitutive model for fibre reinforced cemented Toyoura sand

In this study, the modified Severn-Trent constitutive model is used to simulate the mechanical behaviour of unreinforced, cemented, fibre, and fibre reinforced cemented Toyoura sand consolidated under drained and undrained triaxial compression and extension loading conditions. The model parameters are derived based on the experimental results in the current study, parametric study, trial and error, and by comparison with previous research studies. The comparisons covered ranges of material from 0–3% fibre, 0–3% cement, and 20–60% relative densities. The experimental results and model simulations were compared in terms of deviatoric stress versus axial strain, volumetric strain versus axial strain, and stress path behaviour. Two additional parameters () obtained from the laboratory tests are added to the standard Severn-Trent model to simulate the stress–strain behaviour of cement and fibre reinforced Toyoura sand. Calibration exercises based on studies in the literature and comparisons with the experimental studies herein are conducted with the modified version of the Severn-Trent model. A close agreement of model simulations with the experimental results is observed for many of the tests performed on pure Toyoura sand, cemented, fibre, and fibre reinforced cemented Toyoura sand. The modified model successfully captured the main features of the behaviour (e.g., increase in strength and stiffness with cement additive, increase in volumetric dilatancy due to fibre and cement additives, and general stress path behaviour for drained and undrained conditions) for different types of composite materials with reasonable accuracy. Hence, the current study might serve and should be considered as a step towards modelling of the behaviour of composite materials.

Recycling of Dolomite and Basalt Asphalt Mixes of Existing Highway at Damietta Governerate.(Dept.C)

Recycling of asphalt mixes can be defined as the restoration of aged mixes. The purpose of this research is to evaluate some old asphaltic surface courses in Damietta governerate for their potential of being recycled. Two types of old asphalt surface in Damietta were sampled and transported to the highway laboratory at Mansoura University. One of the two mixes was a dolomite crushed stone mixed at 6.64 asphalt content and the other was a basalt aggregate mixed at 5.2% asphalt content. Control mixes were also prepared using two virgin aggregates similar to those aggregates under study and designed according to Marshall method. It was found that the two Damietta asphalt mixes had high potential to be hot recycled after the addition of a 12% softener and 30% virgin aggregate. No extra addition of asphalt cement was needed in most cases.

A novel thermo-thickening viscosity modifying admixture to improve settlement stability of cement slurry under high temperatures

The viscosity of cement slurry decreases when the temperature rises, resulting in bleeding and sedimentation issues caused by high temperatures. The available viscosity modifying admixtures (VMAs) usually thicken cement slurry under low temperatures but their performances deteriorate under higher temperatures. This study proposes a novel thermo-thickening VMA (i.e., a thermo-thickening polymer with strong hydrophobicity, HTP); its thickening ability will become stronger with an increase in temperature. HTP helps to compensate for the consecutive viscosity reduction of cement slurry due to temperature increases and yields a constant-consistency cement slurry over a wide temperature range (up to 165 °C). Most importantly, HTP is able to slash the bleeding water exuded from cement slurry and eliminate the compressive-strength/density differences among the upper-middle-lower hardened cement paste segments, resulting in a significant improvement in the settlement stability of cement slurry. Microscopic observations reveal that the HTP molecules may fully stretch in the cement slurry and integrate with cement hydration products, contributing to the uniform micromorphology of hardened cement paste. The novel thermo-thickening VMA imposes a limited impact on the compressive strength, fluid loss and thickening time of cement slurry and is very compatible with various cement additives. Finally, the high-temperature high-density cement slurry system containing HTP exhibits a constant consistency until rapid setting behavior, which suggests that it has good potential for field applications.

Impact of selected cement additives and model compounds on the solubility of Nd(III), Th(IV) and U(VI): screening experiments in alkaline NaCl, MgCl2 and CaCl2 solutions at elevated ionic strength

Abstract The solubility of Nd(III), Th(IV) and U(VI) was studied from undersaturation conditions in the presence of selected organic cement additives and model compounds: adipic acid, methyl acrylate, citric acid, melamine, ethylene glycol, phthalic acid and gluconic acid. Experiments were performed under Ar atmosphere in NaCl (2.5 and 5.0 M), MgCl2 (1.0 and 3.5 M) and CaCl2 (1.0 and 3.5 M) solutions with 9 ≤ pHm ≤ 13 (pHm = −log[H+]). Initial concentrations of organic ligands in solution were set constant in all systems to [L]0 = 0.025 M, except in specific cases (e.g. adipic acid, melamine and phthalic acid) where the ligand concentration in the matrix solutions was lower and controlled by solubility. Adipic acid, methyl acrylate, melamine, ethylene glycol and phthalic acid do not impact the solubility of Nd(III), Th(IV) and U(VI) in the investigated NaCl, MgCl2 and CaCl2 systems. Citrate significantly enhances the solubility of Nd(III), Th(IV) and U(VI) in NaCl systems. A similar effect was observed for Th(IV) and U(VI) in the presence of gluconate in NaCl systems. The impact of pH on the stability of the complexes is different for both ligands. Because of the larger number of alcohol groups in the gluconate molecule, this ligand is prone to form more stable complexes under hyperalkaline conditions that likely involve the deprotonation of several alcohol groups. The complexation of gluconate with U(VI) at pHm ≈ 13 is however weaker than at pHm ≈ 9 due to the competition with the highly hydrolysed moiety prevailing at pHm ≈ 13, i.e. UO2(OH)4 2−. The impact of citrate and gluconate in MgCl2 and CaCl2 systems is generally weaker than in NaCl systems, expectedly due to the competition with binary Mg-L and Ca-L complexes. However, the possible formation of ternary complexes further enhancing the solubility is hinted for the systems Mg/Ca-Th(IV)-GLU and Ca-U(VI)-GLU. These observations reflect again the differences in the complexation properties of citrate and gluconate, the key role of the alcohol groups present in the latter ligand, and the importances of interacting matrix cations. The screening experiments conducted within this study contribute to the identification of organic cement additives and model compounds potentially impacting the solution chemistry of An(III)/Ln(III), An(IV) and An(VI) under intermediate to high ionic strength conditions (2.5 ≤ I ≤ 10.5 M). This shows evident differences with respect to investigations conducted in dilute systems, and thus represents a very relevant input in the safety assessment of repositories for radioactive waste disposal where such elevated ionic strength conditions are expected.

An experimental investigation on strength characteristics of fiber-reinforced clayey soil treated with lime or cement

This paper presents an experimental investigation on the strength properties of fiber-reinforced clayey soil stabilized with lime or cement at lower content (5% by weight) cured for 28 days. A series of consolidated undrained (CU) triaxial compression tests and unconfined compressive (UC) strength tests were conducted on compacted untreated, lime-treated and cement-treated clayey soil specimens reinforced with different polyester fiber content (i.e., 0%, 0.05%, 0.1%, 0.2% by weight) to evaluate the effect of fiber content on the strength behavior of tested soil. Test results indicated that the addition of lime or cement gave a significant increase in strength and strength parameters at a certain fiber content, where the improvement effect of cement is better than that of lime. Strain-softening curves were obtained for lime-treated or cement-treated fiber-reinforced specimens compared with the strain-hardening for fiber-reinforced ones. The residual strength is about 75% on average the peak strength for fiber and lime-treated specimens compared to about 50% decrease of peak strength for fiber and cement-treated specimens. The stress and strain curve for the specimen with higher fiber content lies above on that with lower fiber content. Fiber-reinforced plain soil showed a ductile failure mode compared with brittle failure mode for lime or cement-treated specimen. The values of undrained shear strength, unconfined compressive strength, cohesion and internal friction angle of plain soil and lime-treated soil followed the same increase trend when the polyester fiber content increased from 0% to 0.2%. While for lime-treated soil specimens, peak values can be observed when the fiber content was 0.1%. It is recommended to use the optimum fiber content to achieve a better improvement effect in the engineering applications.

Investigation of the mechanical and durability properties of sustainable high performance concrete based on calcium sulfoaluminate cement

Calcium sulfoaluminate (CSA) cement could be a promising alternative to ordinary Portland cement (OPC) to reduce environmental impact of concrete production. This paper investigates the performance of high performance concretes produced with CSA cement in total or partial substitution of OPC (or OPC with ground granulated blast-furnace slag (GGBS)) at water-binder ratio of 0.35. Mechanical, physical, durability, and microstructural properties of different concretes were assessed. The results show that substitution of OPC with CSA cement improves the mechanical properties of concrete . The addition of CSA cement results in a reduced shrinkage deformation, while it increases the risk of carbonation and corrosion of steel rebars . Combination of CSA cement with OPC and GGBS in the binary and ternary systems causes a reduction of the strengths of concrete, and adversely affects the durability properties. The SEM observation show that ettringite crystals decomposed in the CSA-blended mixes and resulted in the formation of carbonated phases. • High performance concretes were developed with calcium sulfoaluminate (CSA) cement. • Ground granulated blast-furnace slag was utilized in ternary blended concrete mix. • Linear correlation between resistivity and compressive strength was obtained. • Electrical resistivity of CSA mixes can lead to misleading indication on corrosion. • The addition of CSA cement increases the risk of steel rebars corrosion.

Cemental composites with polyurethane and recycled polyvinyl chloride: The influence of industrial waste addition on flammability

AbstractIn the construction industry, the large number of residues presents a challenge for recycling and the possibility of producing new materials. This study reported the effects of the addition of polyvinyl chloride (PVC) residues and cement/alumina trihydrate on the production of a fire‐resistant thermal‐acoustic insulation material. The composites were verified by scanning electron microscopy, the polyurethane (PU) cells were maintained with the addition of PVC, cement, and trihydrate alumina. The reduction in compressive strength for boards with 50% PVC waste as a replacement for the PU raw material. The boards showed the composites' conductivity coefficient was lower than that of the perforated brick and combustion deceleration up to flame extinction in the flammability test (UL94) because of the PVC/cement/alumina trihydrate. They also presented cost savings (~57%) and carbon dioxide emissions (~49%) from the raw material, contributing to developing a less predatory and socio‐environmentally responsible industry.

The Effect of Cement Addition on Water Vapour Resistance Factor of Rammed Earth.

The article aims to determine the effect of cement addition on the water vapour resistance factor of stabilized rammed earth. Literature analysis indicates that different earthen materials show large differences in water vapour resistance factor values. The high diffusion resistance of concrete concerning other construction materials suggests that cement will be one of the factors significantly affecting these values. The paper presents water vapour resistance factor test results of rammed earth with various soil particle sizes and cement contents. The obtained results showed that an increase of cement addition increases the diffusion resistance of the material. However, the diffusion resistance of cement stabilized rammed earth is still low compared to concrete.

Compósito de resíduos de mineração com cimento e cal para materiais de construção sustentáveis

<p> <span class="fontstyle0">Sustainable alternatives have been developed with the use of waste in construction, among which we can highlight mining waste due to its large amount generated and environmental impact caused. This work consists in the joint application of scheelite residue and stone powder with lime and cement addition, producing cylindrical specimens, to evaluate possible uses in constructive materials. After chemical and physical characterization, the percentage of each residue was determined through the analysis of packing between the particles, which resulted in a formulation of 50% of each residue with the addition of cement and / or lime in the contents of 6% and 12%. Essays for simple compressive strength (SCS), water absorption (WA) and chemical phase analysis by scanning electron microscopy (SEM) and X-ray diffraction (XRD) were evaluated at determined cure times. The SCS essays results of formulations with residues and cement reached values above 1 MPa and WA essays results with value below 20%, according to the Brazilian technical standards. Cement phases were observed in SEM and XRD analysis. The results obtained from mixing the waste with the cement are promising for the manufacture of cement building materials.</span> <br /><br /></p>

Significance of compaction time delay on compaction and strength characteristics of sulfate resistant cement-treated expansive soil

Abstract The addition of cement for stabilization of expansive soils is one of the most commonly used methods. As with every calcium-based stabilizer, the time delay between the physical mixing of the stabilizer and compaction plays an important role in achieving the desired results after stabilization. However, a clear insight on the determination of optimum time delay for achieving the maximum desired compaction properties of cement-stabilized soils is yet to be established. Furthermore, the recent studies highlighted the use of sulfate to mitigate the negative effect of compaction time delay. The only drawback with the use of sulfate along with calcium-based stabilizers is the formation of ettringite, which deteriorates the stabilized soil matrix. In view of this, the present study is aimed at using the sulfate resistant cement (SRC) as a stabilizer along with the controlled addition of sulfate solutions to mitigate the negative effect of compaction time delay in stabilizing the expansive soil. To bring out the above effects, three periods of time delays (0 h, 6 h and 24 h) and three sulfate concentrations of 5000 parts per million (ppm), 10,000 ppm and 20,000 ppm were adopted. The experimental results showed that the delay in compaction resulted in the formation of clogs and reduction of strength of SRC-stabilized expansive soil. Upon sulfate addition to SRC-stabilized expansive soil, the formation clogs was not curtailed and resulted in the formation of ettringite clusters. These formations were captured with the help of scanning electron microscope (SEM) images and validated with electron dispersive X-ray spectroscopy (EDAX) analysis. Further, an attempt is also made to explain the mechanism of density and strength reduction with the aid of physico-chemical properties and mercury intrusion porosimetry (MIP) studies.

Compressive strength value of clay soil stabilization with palm oil fuel and cement

Mixing native soil with empty oil palm ash bunches and cement is an attempt to increase the clay soil bearing capacity. The purpose of this study was to determine the effect of adding 5% of oil palm ash and cement bunches of 0%, 5%, 7.5%, and 10%, respectively, to the value of free compressive strength. The contribution of this research can later become recommendations for handling soil improvement. The method used is the testing of the compressive strength-free soil stabilization in a laboratory that refers to SNI 3638: 2012. The results showed that the clay studied was high clay plasticity with a liquid limit value of 55.3%. The addition of empty oil palm bunches ash and cement tends to reduce the value of the soil liquid limit to 41.77% at a percentage of 5% empty oil palm bunches ash and 10% cement. The strength value of soil bearing capacity increased to 4.90 kg/cm² on 5% ash of empty oil palm bunches and 10% of cement at 0 days ripening. The carrying value of native soil is 1.96 kg/cm². The conclusion is that the addition of oil palm and cement bunches ash tends to reduce the value of soil consistency and increase the value of the compressive strength of the soil. Addition of Empty oil palm bunches ash and cement can be an alternative to stabilizing clay soils.

Stiffness, compressibility, and hydraulic conductivity of compacted soil mixtures submitted to acidic percolation

Abstract The inadequate disposal of hazardous solid waste has become a potential issue, mainly because of the impacts on the environment and human health. This occurs mainly through the contamination of subsurface soil and groundwater by leachates, which are often of the acidic constitution. To prevent such situations, the study of more efficient waste containment techniques has become opportune. In this way, this work was aimed to investigate the mechanical and hydraulic behavior of compacted clayey soil, with and without the addition of Portland cement (0 and 2%), submitted to the action of a sulfuric acid solution (2% volume concentration) and to a constant static vertical load (280 kN/m2), aiming at its prospective application as containment barrier. The experimental program comprised a few tests performed in an instrumented rigid-wall permeameter, during which the variations in hydraulic conductivity, shear modulus, and settlements were measured. The results showed that the hydraulic conductivity increased with cement addition when only water was percolated. During the acidic percolation, however, a reduction was observed only for the cemented soil. The acidic attack caused, almost instantaneously, an increase in the settlement rate and a reduction in stiffness, although a trend of stabilization was observed afterward.

Influence of Limestone Mineral Addition in Cements on the Efficacy of SCMs in Mitigating Alkali-Silica Reaction Assessed by Accelerated Mortar Bar Test

AbstractThis study evaluates the effect of limestone mineral addition in cement on the efficacy of supplementary cementitious materials (SCMs) in mitigating alkali-silica reaction (ASR) using the a...

Predicting Resilient Modulus of Cementitiously Stabilized Subgrade Soils Using Neural Network, Support Vector Machine, and Gaussian Process Regression

Artificial neural network (ANN), support vector machine (SVM), and Gaussian process regression (GPR) were developed in this study for predicting resilient modulus (Mr) values of cementitously stabilized subgrade soils. A database was developed using laboratory test results on 160 specimens prepared by using four soils stabilized with three cementitious additives, namely, lime (3%, 6%, 9%), CFA (5%, 10%, 15%), and CKD (5%, 10%, 15%). Of these, 120 specimens (development dataset) prepared using three types of soils were used in development, and the remaining 40 specimens (validation dataset) were used in the validation of the developed models. A commercial software, MATLAB, was leveraged to develop three ANN models (radial basis function network/RBFN; a multilayer perceptrons network/MLPN with one hidden layer; and MLPN with two hidden layers); four SVM models (linear, quadratic, cubic, and radial basis function kernels); and three GPR models (rational quadratic, Matérn, and exponential kernels) by using codes written in MATLAB language. The strengths and weaknesses of the developed models were examined by comparing the predicted Mr values with the observed/experimental values with respect to the mean squared error (MSE) values and determination coefficient (R2) values. Through comprehensive comparison among these three types of models, an MLPN model with one hidden layer was determined as the best performing model developed in this study. It can be used to predict Mr of cementitiously stabilized subgrade soils for Level 2 pavement design applications. This model as well as the other models could be refined using an enriched database.

Strategies for control and mitigation of efflorescence in metakaolin-based geopolymers

Efflorescence can be harmful to material performance as a consequence of microstructural changes due to leaching and carbonation of alkalis. This article identifies mechanisms of efflorescence in metakaolin-based geopolymers, and approaches to reduce free/mobile alkali cations and pore network connectivity, and hence reduce efflorescence. Mechanical, mass transport and microstructural properties are assessed in metakaolin-based geopolymer cements produced using different alkali concentrations in the alkali activator and substitution/addition of blast furnace slag, silica fume, calcium aluminate cement, silicone oil and a dispersive admixture. The most effective strategy to reduce efflorescence results from increasing Si/Al in the geopolymer gel by addition of soluble silicate, silica fume or silicone oil. Addition of calcium aluminate cement or a dispersive admixture also reduce efflorescence, but are less effective. These results confirm that efflorescence may be reduced by controlling the amount of soluble silicates and reducing free alkali cations in geopolymers, providing enhanced performance and durability.

Time Delay Effects on Compactability of Soil-Cement Materials during Proctor Testing

The Proctor test method, as specified in AASHTO T134 and ASTM D558, continues to play a vital role in design and construction quality control for soil-cement materials. However, neither test method establishes a methodology or standardized protocols to characterize the effects of time delay between cement addition and compaction, also known as compaction delay. Compaction delay has been well documented to have a notably negative effect on compactability, compressive strength, and overall performance of soil-cement materials, but specification tools to address this behavior are not prevalent. This paper aims to demonstrate the extent of compaction delay effects on several soil-cement mixtures used in Mississippi and to present recommended new test method protocols for AASHTO T134 to characterize compaction delay effects. Data presented showed that not all soil-cement mixtures are sensitive to compaction delay, but some mixtures can be very sensitive and lead to a meaningful decrease in specimen dry density. Recommended test method protocols were presented for AASHTO T134 and commentary was presented to provide state Departments of Transportation and other specifying agencies a few examples of how the new compaction delay protocols could be implemented.

Designing the Composition of Cement-Stabilized Rammed Earth with the Association Analysis Application.

The main advantage of the structural composite material known as cement-stabilized rammed earth (CSRE) is that it can be formulated as a sustainable and cost-saving solution. The use of the aggregates collected very close to a construction site allows economizing on transportation costs. Another factor that makes sustainability higher and the costs lower is a small addition of cement to the CSRE in comparison to the regular concrete. However, the low cement content makes the compressive strength of this structural material sensitive to other factors. One of them is the composition of the aggregates. Considering the fact that they are obtained locally, without full laboratory control of their composition, achieving the required compressive strength of CSRE is a challenge. To assess the possibility of achieving a certain compressive strength of CSRE, based on its core properties, the innovative algorithm of designing CSRE is proposed. Based on 582 crash-test of CSRE samples of different composition and compaction levels, along with the use of association analysis, the spreadsheet application is created. Applying the algorithm and the spreadsheet, it is possible to design the composition of CSRE with high confidence of achieving the required compressive strength. The algorithm considers a random character of aggregates locally collected and proposes multiple possible ways of increasing the confidence. They are verified through innovatively applied association analyses in the enclosed spreadsheet.