Silica Fume Mixtures Research Articles

Clinker-free CaO-activated silica fume as a cementitious binder for pavement application

Ordinary Portland cement (OPC) production requires heating limestone up to 1450 °C and produces 0.5–0.9 kg of carbon dioxide for every 1 kg produced. Moreover, the massive volume of cement manufactured around the world every year adds to the urgent need to look for sustainable alternatives. This work proposes a novel calcium oxide (CaO)-activated high-volume silica fume mixture as a cementitious binder for pavement application that can address the sustainability concern with cement (because producing CaO requires a much lower calcination temperature than OPC, and that CaO is also used in low-volume in the binder). The combination of low-volume CaO and high-volume silica fume, particularly as a pavement binder has not been studied in the literature before. The compressive and flexural strength results showed that even by using a small fraction of CaO in the binder, it is possible to obtain acceptable strengths that satisfy ASTM pavement design guidelines, while OPC is unable to provide similar strengths at such low dosage. The mix having CaO content as 30 % of the silica fume content (CSF-30) shows the highest compressive strength (28d: 18.4 MPa) and flexural strength (28d: 4 MPa). In contrast, the maximum OPC-silica fume compressive and flexural strengths observed are 13.9 MPa and 2.9 MPa respectively at 28d From the microstructural results, it was seen that CaO–silica fume develops strength due to formation of calcite and calcium silicate hydrate. Almost all CaO–silica fume mixes exhibited lower porosity compared to their OPC-silica fume counterparts; CSF-30, the mix having the best mechanical performance showed the lowest porosity at 28d (2.8 %). A comparative sustainability analysis followed by a 5D analysis considering all the parameters studied in this work revealed that CSF-30 is the best binder alternative (overall score: 5.24). The results of this work will be useful for pavement users, designers, researchers, engineers, and relevant government officials, in having a sustainable clinker-free alternative pavement binder to OPC, particularly for low-volume roads, that satisfies the pavement design guidelines.

Rheological Properties of Silica-Fume-Modified Bioasphalt and Road Performance of Mixtures.

The objective of this research is to enhance the high-temperature antirutting and antiaging characteristics of bioasphalt. In this study, silica fume (SF) was selected to modify bioasphalt. The dosage of bio-oil in bioasphalt was 5%, and the dosage of SF was 2%, 4%, 6%, 8%, and 10% of bioasphalt. The high- and low-temperature characteristics, aging resistance, and temperature sensitivity of Bio + SF were evaluated by temperature sweep (TS), the multiple stress creep recovery (MSCR) test, the bending beam rheology (BBR) test, and the viscosity test. Meanwhile, the road behavior of the Bio + SF mixture was evaluated using the rutting test, low-temperature bending beam test, freeze-thaw splitting test, and fatigue test. The experimental results showed that the dosage of SF could enhance the high-temperature rutting resistance, aging resistance, and temperature stability of bioasphalt. The higher the dosage of SF, the more significant the enhancement effect. However, incorporating SF weakened bioasphalt's low-temperature cracking resistance properties. When the SF dosage was less than 8%, the low-temperature cracking resistance of Bio + SF was still superior to that of matrix asphalt. Compared with matrix asphalt mixtures, the dynamic stability, destructive strain, freeze-thaw splitting strength ratio, and fatigue life of 5%Bio + 8%SF mixtures increased by 38.4%, 49.1%, 5.9%, and 68.9%, respectively. This study demonstrates that the development of SF-modified bioasphalt could meet the technical requirements of highway engineering. Using SF and bio-oil could decrease the consumption of natural resources and positively reduce environmental pollution.

Utilizing ensemble machine learning and gray wolf optimization to predict the compressive strength of silica fume mixtures

AbstractThe concrete compressive strength is essential for the design and durability of concrete infrastructure. Silica fume (SF), as a cementitious material, has been shown to improve the durability and mechanical properties of concrete. This study aims to predict the compressive strength of concrete containing SF by dual‐objective optimization to determine the best balance between accurate prediction and model simplicity. A comprehensive dataset of 2995 concrete samples containing SF was collected from 36 peer‐reviewed studies ranging from 5% to 30% by cement weight. Input variables included curing time, SF content, water‐to‐cement ratio, aggregates, superplasticizer levels, and slump characteristics in the modeling process. The gray wolf optimization (GWO) algorithm was applied to create a model that balances parsimony with an acceptable error threshold. A determination coefficient (R2) of 0.973 demonstrated that the CatBoost algorithm emerged as a superior predictive tool within the boosting ensemble context. A sensitivity analysis confirmed the robustness of the model, identifying curing time as the predominant influence on the compressive strength of SF‐containing concrete. To further enhance the applicability of this research, the authors proposed a web application that facilitates users to estimate the compressive strength using the optimized CatBoost algorithm by following the link: https://sf-concrete-cs-prediction-by-javid-toufigh.streamlit.app/.

Piezoresistive response of geopolymer pastes activated by silica fume-derived alkaline solution

This study examined the self-sensing performance of metakaolin-based geopolymer paste samples activated by an alkali activator, which is a solution mixture of potassium hydroxide and silica fume (SF). Their piezoresistive response under repeated compressive loads was found to improve with increasing SF content. It was found from their XRD, SEM, and FTIR results that the change in the SF content did not alter the phase composition of the geopolymer matrices. The factorial change in the electrical resistivity of geopolymer samples with a maximum SF content was calculated to be about 0.024. Their pore solutions were detected to be mainly filled with potassium and silicon ions due to the use of higher concentrations of SF particles. The UV spectrophotometry measurements of this study confirm that all the geopolymer samples displayed semiconductor behaviour. The SF-derived alkaline activator can enable the self-sensing character of geopolymer-based concrete, which isenvironmentally friendly and has recently shown great potential to monitor structural integrity under applied external loads.

Engineering Characteristics at Early Age of Cemented Silica Fume Paste for Peat Compaction Grouting

Introduction Cemented Silica Fume Paste (CSFP) is currently being investigated for compaction grouting material to improve peat ground engineering properties. The CSFP is made in the laboratory using a proportional mixture of silica fume, cement binder, and tap water. The silica fume material is a byproduct of the metal processing industry, which critically requires a better alternative utilization in the near future in order to cut the storage cost and minimize the environmental impact. Aims This paper aims to present preliminary results on the engineering characteristics of CSFP at an early age through a series of rheological and strength tests. A general observation of the physical properties and microstructure of CSFP is also presented. Methods The CSFP specimens with cement binder range from 0% to 30% with the increment of 5% and Water-to-Solid (W/S) ratio ranges from 0.8, 0.9 and 1.0 were prepared and tested. A series of rheology test and Unconfined Compressive Strength (UCS) tests were carried out for the CSFP specimens at an early age. The data were analyzed statistically and mathematical formulation is presented. Results The results indicate that CSFP mixtures behave as pseudoplastic or shear thinning fluid, where the shear stress and viscosity depend highly on the shear rates. The higher the shear rates, the higher the shear stress and the lower the viscosity. Curve fitting showed that the best relationship between shear stress and shear rate is the power law function (Ostwald–de Waele relationship). Statistical parameters, k, n, R2 of the power law functions are reported. There was no good correlation found between the power law function statistical parameters and the cement content. The UCS tests showed that the shear strength increases with the amount of cement content. The actual W/S reduces as the cement content increases, which is attributed to the cement hydration. Conclusion The CSFP mixtures were found to be a pseudoplastic or shear thinning fluid at an early age that provides an advantage during the material injection on the ground. Cemented Silica Fume Paste can be potentially used as compaction grout to improve peat. The current findings provide a better understanding of the CSFP characteristics and to better design CSFP to be injected into peat ground.

Investigation of the Properties of Metakaolin-Based Geopolymer Materials Using Ferrisilicates as Additives Synthesised in Sodium Hydroxide Solution or Distilled Water

The main objective of this work is to investigate the behaviour of ferrisilicates prepared from hematite and two silica sources (rice husk ash and silica fume) on the compressive strength of geopolymer materials. Some ferrisilicates were synthesised in 2M sodium hydroxide solution. Others were prepared using distilled water as a solvent. The Fe2O3/SiO2 molar ratio contained in the ferrisilicates is set to 0.2. Metakaolin and sodium silicate solution with a molar ratio of SiO2/Na2O of 1.6 were used as the aluminosilicate and hardener in this work. The control geopolymer compressive strength is 53.34 MPa. For ferrisilicates prepared in alkaline solution using rice husk ash and silica fume, their compressive strength values are 71.91 and 77.72 MPa, respectively. The compressive strengths of the geopolymer materials made from ferrisilicates prepared in distilled water using rice husk ash and silica fume are 74.13 and 44.73 MPa, respectively. In the presence of ferrisilicate obtained by dissolving silica fume and hematite in sodium hydroxide solution, the maximum compressive strength of 77.72 MPa was obtained. When ferrisilicates from the mixture of silica fume, hematite, and distilled water are used as an additive, the minimum compressive strength of 43.73 MPa is achieved. It can be concluded that additives synthesised in an alkaline medium and those obtained in distilled water with rice husk ash improve compressive strength. On the other hand, the compressive strength of the geopolymer material that uses the additive produced with silica fume in distilled water is lower (44.73 MPa).

Mechanical Enhanced Involuntary Stress-Strain Characteristics and Environmental Assessment: GGBS & Silica-Fume

The research looks at the characteristics of Normal Concrete (NC) by testing small square blocks and larger cylindrical samples to see how they respond under pressure and strain. The flexibility of different Ground Granulated Blast Furnace Slag (GGBS) and silica fume mixtures is measured using the Saenz Model, and the results are shown in graphs comparing stress and strain. This study examines how substituting materials like GGBS and adding materials like silica fume to concrete affects its strength and environmental impact. Seven mix designs of M35 grade concrete were prepared to study strength, toughness, ability to stretch, and absorb energy, and how stress and strain are related. The results show that substituting 35% GGBS and adding 10% silica fume is best for improving the strength of NC when compressed. The suggested mathematical equations for how well NC can resist being compressed match up closely with the real-life test results. However, the measured factors show that incorporating 30% GGBS with 5% and 15% silica fume in the concrete causes more environmental harm. However, the NC without pozzolana shows a lower measure of its environmental impact, except for its contribution to climate change.

Characterization and optimization of fresh and hardened properties of ultra-high performance geopolymer concrete

Due to the deterioration and environmental issues of cement-based ultra-high-performance concrete (UHPC), there is an increasing interest in utilizing geopolymer technology to develop UHPC. In this regard, a statistically based model using response surface methods is applied to predict the fresh and mechanical properties of ultra-high performance geopolymer concrete (UHPGC) mixtures. Twenty mixtures were designed and generated experimentally using the central composite design (CCD) concept. In this context, the effects of three principal factors—the effects of silica fume (SF), natural sand content, and different curing temperatures—on the flowability, setting times, bulk density, compressive, and flexural strengths were examined. The models presented herein reveal that all the inputs and outputs are perfectly correlated. Microscopic investigations were used to determine the morphological characteristics of the optimum mixture. The results revealed that the bulk density, flexural, and compressive strengths of the UHPGC ranged from 2461 to 2536 kg/m3, 6.48–9.39 MPa, and 104–152 MPa, respectively. According to the validated models and optimization findings, the optimum mixture of SF (22.5%) and sand content (1150 kg/m3) cured at 100 °C was found to develop the optimized UHPGC with the best microstructure performance. From the experimental results, the optimized UHPGC mixture possessed excellent mechanical properties (2521 kg/m3, 9.39 MPa and 152 MPa), and it had a non-porous structure primarily made of a dense geopolymer gel. Overall, the current study provides new insights into the design and production of UHPGC materials using the response surface method, which could contribute to the widespread use of this concrete in practical applications.

Shrinkage, compressive and bond strengths of alkali activated/cement powder for alternative coating applications

This paper reports the properties of a novel coating material produced from alkali-activated/cement powder (AACP), including setting time, strength development, drying and autogenous shrinkages, and bond strength of one-part AACP paste-coated reinforcing steel bars in concrete. The AACP paste was prepared by activating a mixture of dry geopolymer powder (GPP), Portland cement (PC), and silica fume (SF) with tap water and 2 M sodium hydroxide solution. The effect of PC replacement, sodium silicate-to-sodium hydroxide solution (SS-to-SH) ratio, and pre-curing temperature in the production of GPP on the properties of AACP paste were also investigated. Test results showed that the incorporation of FA and PC activated with an SS-to-SH ratio of 2.0 for the production of GPP decreased their setting time of fresh one-part AACP pastes, whereas their strength development marginally increased. Furthermore, the increasing PC content and SS-to-SH ratio had an adverse effect on drying and autogenous shrinkages. However, the pre-curing temperature had a marginal effect on their shrinkages. In addition, one-part AACP paste-coated reinforcing steel bars positively affected the bond strength of reinforced concrete, especially for the GPP produced by FA without PC. The increased reaction products at the contact zone could assist in improving their bond strength. It can be recommended that the use of FA without PC activated with a low SS-to-SH ratio in the production of GPP would be beneficial in improving shrinkage and bond strength while providing high equivalent substrate stiffness (ks).

Mechanical behaviours of cellular lightweight concrete using finite element analysis

Cellular Lightweight Concrete (CLC) is a concrete brick with a density lighter than concrete bricks. The efficiency of the use and quality of CLC can be determined by analysing mechanical behaviour using the finite element method. The purpose of this study is to analyse the mechanical behaviour of lightweight concrete using the finite element method. Analysis of mechanical behaviour using LUSAS finite element software. The CLC model used admixture materials of silica foam, palm oil fly ash (POFA) and lime (CaCO3). The study resulted in the difference between the numeric and experimental analysis being less than 10%. The most considerable deformation occurred at the top of the CLC model based on the deformation contour distribution. The most significant stress and strain contours distribution occurred at the CLC model’s bottom. The controlled load of 6 kN to 60 kN causes an increase in the mechanical behaviour of CLC. The most considerable deformation occurred when the maximum load on the CLC model with a silica fume mixture was 9.239 mm. The stress of the CLC model is 1.148 N/mm2, and the most significant strain occurred in CLC with silica fume admixture with a CLC weight of 0.038. Thus, the finite element method can be used as a comparison of laboratory test results to determine the mechanical behaviour of CLC.

Effect of inclusion of natural pozzolan and silica fume in cement - based mortars on the compressive strength utilizing artificial neural networks and support vector machine

This study illustrates the effect of incorporating natural pozzolan (NP) and silica fume (SF) in cement-based mortars on the compressive strength. Up to 40% of the weight of cement in cement mortars can be replaced by NP powder. NP in its natural state can be used to replace up to 40% of the volume of sand in cement mortars. The replacement levels of cement by weight with SF are 5% and 10% to improve the mechanical properties of the NP-based cement mortars. Experiments were conducted to assess the compressive strength of cement mortars containing NP at 28 and 180 days of curing. The water/cement ratio was 0.49 for all the specimens. Models for the compressive strength of NP-based cement mortars and NP-SF-based cement mortars were formulated based on nonlinear regression analysis, artificial neural network (ANN) , and support vector machine (SVM) approach to explore the impact and exchanges of cement, NP, and SF mixtures. The RMSE of the nonlinear, ANN, and SVM models revealed that the RMSE of the ANN is significantly less than that of the nonlinear and SVM models. A sensitivity analysis for the predicted compressive strength of NP-based cement mortars and NP-SF-based cement mortars was conducted. The application of the SVM technique was evaluated through four different kernels, including sigmoid, linear, polynomial, and radial basis function (RBF). The RBF kernel shows better performance and offers more accurate results than the sigmoid, linear, and polynomial kernels. The results showed that the NP replacing cement and the SF replacing cement are the most dominant parameters for the prediction of compressive strength. Finally, the developed models from this study can be used to predict the compressive strength of cement mortars containing NP and SF.

Increasing the Reliability of Formation Factor-Based Transport Property Prediction for High Performance Concrete Mixtures Through Innovative Matching Pore Solution Curing

Recent specifications for concrete bulk resistivity tests (ASTM C 1876 and AASHTO TP 119) recommend a submerged standard (simulated) pore solution (SPS, solution conductivity = 78.74 mS/cm) for curing concrete specimens. The rationale for the bucket test is that immersing concrete specimens in a soak solution similar to their pore solution would eliminate the need to determine pore solution resistivity for calculating the formation factor (FF) of concrete mixtures. However, the thermodynamic modeling predictions of 91-day pore solution concentration (PSC) for eight high performance concrete (HPC) mixtures evaluated in the current study showed SPS to be a close representation only for reference ordinary Portland cement (OPC) and binary silica fume mixtures. In contrast, the average PSC of Class F and Class C fly ash mixtures was approximately 12% to 20% lower and 20% to 40% higher, respectively, than the SPS. Accordingly, an innovative matching pore solution (MPS) curing approach was developed in which mixtures are grouped based on the influence of supplementary cementitious materials (SCMs), that is, their type and replacement levels of the long-term PSC of concrete mixtures and, thereby, cured in a simulated solution matching the average PSC of a particular group. Based on experimental work in the current study, HPC mixtures under MPS demonstrated a lower coefficient of variation (COV) and more comparable (<10% difference) bulk resistivity (BR) and surface resistivity (SR) measurements compared with SPS. Moreover, the MPS improved the reliability in FF determination and FF-based transport property prediction for HPC mixtures, as verified by lower mean absolute error and improved R2 between FF-predicted diffusion coefficients and experimental measurements.

The effect of dunite powder and silica fume on the viscosity, physico-mechanical properties and sulphate resistance of self-compacting mortars

Recently, the use of waste and novel natural resources in the concrete industry has drawn the attention of researchers from all around the world. Self-compacting mortars (SCMs) can be created using dunite powder (DP) as natural cementitious material and silica fume (SF), and provide the distinctive fresh properties required for SCMs. This study analyzes the viscosity, mechanical characteristics, and sulphate resistance of SCMs containing SF and DP. Twelve different combinations, containing reference, binary, and ternary mixtures, were created by partially substituting Portland cement (PC) with DP and SF. Binary mixes were produced by substituting cement with DP at weight replacement rates of 5, 10, 15, 20, 25, and 30%. Ternary mixes were generated at rates of 5, 10, 15, 20, and 25% DP and 25, 20, 15, 10, and 5% SF, respectively. The compressive and flexural strength of water-cured SCM samples were measured at 3, 28, and 180 days of age. Mechanical performance of 28-day water-cured SCMs specimens was also evaluated after 180 days of exposure to MgSO4 solution. The transport features and sorptivity of water-cured SCMs samples for 28 days were also assessed. Microstructural characteristics using SEM were analyzed. The results demonstrate that all SCM mixtures containing DP and DP + SF have viscosity values higher than the reference mixture. The experimental results exhibited that very good compressive strength performance was gained for the binary SCMs up to 30% DP content at a late age of 180 days. At a long curing age of 180 days, using DP instead of cement up to 30% only slightly decreased the compressive strength by 15%. According to the findings, the specimens that had cement substituted with a 20% DP and 10% SF mixture had superior mechanical properties than the other ternary and most of binary SCMs specimens. The mixture DP20SF10 had the best compressive strength performance. All binary and ternary SCMs exhibited good sulfate resistance.

Alternative Fillers in Asphalt Concrete Mixtures: Laboratory Investigation and Machine Learning Modeling towards Mechanical Performance Prediction.

In recent years, due to the reduction in available natural resources, the attention of many researchers has been focused on the reuse of recycled materials and industrial waste in common engineering applications. This paper discusses the feasibility of using seven different materials as alternative fillers instead of ordinary Portland cement (OPC) in road pavement base layers: namely rice husk ash (RHA), brick dust (BD), marble dust (MD), stone dust (SD), fly ash (FA), limestone dust (LD), and silica fume (SF). To exclusively evaluate the effect that selected fillers had on the mechanical performance of asphalt mixtures, we carried out Marshall, indirect tensile strength, moisture susceptibility, and Cantabro abrasion loss tests on specimens in which only the filler type and its percentage varied while keeping constant all the remaining design parameters. Experimental findings showed that all mixtures, except those prepared with 4% RHA or MD, met the requirements of Indian standards with respect to air voids, Marshall stability and quotient. LD and SF mixtures provided slightly better mechanical strength and durability than OPC ones, proving they can be successfully recycled as filler in asphalt mixtures. Furthermore, a Machine Learning methodology based on laboratory results was developed. A decision tree Categorical Boosting approach allowed the main mechanical properties of the investigated mixtures to be predicted on the basis of the main compositional variables, with a mean Pearson correlation and a mean coefficient of determination equal to 0.9724 and 0.9374, respectively.

Particle Size Effects on the Volumetric Shrinkage of Bentonite–Sand Mixtures

Tests were conducted on bentonite–silica fume mixtures (BSFMs) to determine how particle size affects the volumetric shrinkage of bentonite–sand mixtures (BSMs) used as hydraulic barriers in waste disposal facilities. Free desiccation tests, liquid limit tests, plastic limit tests, and direct shear tests were conducted to compare the soil shrinkage characteristic curves, shrinkage limits, plasticity, and shear strength of BSFMs to that of the commonly used bentonite–standard sand mixtures (BSSMs) at 30% sand percentage. BSFMs exhibited higher air entry values (up to 55.9% higher), shrinkage limits (up to 14.6% higher), final void ratio (up to 43.6% higher), peak shear strength (up to 115% higher), and a smaller percentage of volumetric shrinkage (10.8%) than BSSMs due to the particle contact and constrained particle movement. The liquid and plastic limits of BSFMs, in contrast, were also higher (up to 99.2% and 27.1%) than that of BSSMs. Particle size plays a critical role in controlling the shrinkage limits of BSMs compared to clay fractions.

Effect of Binary and Ternary Binders on Flow and Strength of Cement Mortar

This paper reports the results of laboratory work on the flow and strength of cement mortars containing binary and ternary blends of portland cement, silica fume (SF), Class C fly ash (CFA) and Class F fly ash (FFA). The cement was partially replaced with 20 and 40 wt.% of fly ash (FA) and 5 wt.% of SF as binary mixtures. Besides, the ternary mixtures contained 15%FA+5%SF and 35%FA+5%SF in place of 20% and 40% cement respectively. Both fly ashes were used in the ternary mixtures, thus, 4 mixtures containing ternary binders were prepared. Two sets of mortar mixtures having either same flow or same water/binder (W/B) ratio as those of the control mixture (containing no mineral admixture) were investigated. In total, 15 mortar mixtures were taken into constitution in the present study. The flow of mixtures was measured immediately after casting. In addition, the 7-and 28-day flexural and compressive strength of the mortar mixtures were determined. The use of SF in binary mixtures with constant W/B ratio provided the highest compressive strength (68 MPa). In ternary mixtures the use of 20%FA+5%SF mixture with constant W/B ratio showed the highest 28-day compressive strength (65 MPa). Among the mixtures with constant W/B ratio, ternary mixtures showed the lowest flow values. Besides, in the mixtures with constant flow, once again, the ternary mixtures had the highest W/B ratio. Both in binary and ternary specimens, the mixtures prepared with FFA had a higher flow than that of the CFA mixtures.

Preliminary Assessment of Rice Husk Ash (RHA) as Functional Interphase Agent in Sustainable Composite Systems for Structural Strengthening

Over the last few years, the effectiveness of textile-reinforced mortar (TRM) composite systems for structural retrofitting has led to the widespread adoption of these materials in the practice and to the issue of up-to-date design guidelines. Nonetheless, the weak interfacial bonding that is frequently observed between matrix and fibres is likely to cause inconsistent failure modes and, generally speaking, to severely limit the reinforcing potential of the textile. A promising solution to tackle this issue consists in treating the surface of the reinforcing fibres with a functional coating to improve the adhesion at the interphase. In this paper, a pilot study is presented to assess the effectiveness of a fully sustainable polymer coating, consisting in polyvinyl alcohol (PVA) loaded with with rice husk ash (RHA) or with a 50/50 mixture of RHA and silica fume (SF). The coating was applied on basalt fabrics to reinforce TRM coupons that were mechanically tested under uni-axial tensile loads. The mechanical properties of the TRM samples were significantly increased by up to 20%, and the peak load was attained at a higher deformability level, which is a clue of the enhanced ductility of the reinforced elements.

Preliminary Study of the Fresh and Hard Properties of UHPC That Is Used to Produce 3D Printed Mortar.

Three-dimensional printed concrete (3DPC) is a relatively recent technology that may be very important in changing the traditional construction industry. The principal advantages of its use are more rapid construction, lower production costs, and less residues, among others. The choice of raw materials to obtain adequate behavior is more critical than for traditional concrete. In the present paper a mixture of cement, silica fume, superplasticizer, setting accelerator, filler materials, and aggregates was studied to obtain a 3DPC with high resistance at short curing times. When the optimal mixture was found, metallic fibers were introduced to enhance the mechanical properties. The fresh and hard properties of the concrete were analyzed, measuring the setting time, workability, and flexural and compressive strength. The results obtained demonstrated that the incorporation of fibers (2% in volume) enhanced the flexural and compressive strength by around 163 and 142%, respectively, compared with the mixture without fibers, at 9 h of curing. At 28 days of curing, the improvement was 79.2 and 34.7% for flexural and compressive strength, respectively.

Thermal and microwave synthesis of silica fume-based solid activator for the one-part geopolymerization of fly ash.

This paper tests the development of a silica fume-based material, capable to be used as a solid activator for the one-part geopolymerization of fly ash. Through a simple procedure, a mixture of silica fume, an amorphous and silicon-rich by-product, sodium hydroxide and water, is converted, after a low-temperature treatment, to a new powder product mainly containing sodium silicate (Na2SiO3). Two different treatment methods are tested for the synthesis of the solid activator: heat and microwave treatment. Microwave processing is more sustainable and more efficient than thermal treatment, since purer products are produced with less energy consumption. The use of these low embodied energy products, as the only solid activator of fly ash, leads to geopolymers with comparable mechanical performance to those prepared with commercial products revealing their potential successful addition in the geopolymer market.

STUDY THE EFFECT OF ADDING GLENIUM 51 AND POLYMERIC PLASTICS ON THE MECHANICAL AND PHYSICAL PROPERTIES OF ORDINARY PORTLAND CEMENT

Cement is importance as one of the strategic construction of any civilization depends, and its paramount significance in the construction of building, roads, bridges and infrastructure, which requires the use of cement with special specification and thus the use of polymers as additives to increase the compressive, flexural and tensile strength of the cement used in construction. Cement producing can possibility with high specification and for multiple uses, some studies be carried out on the use of some available additives in small quantities so as to give the cement high desirable specification in terms of color, compressive strength, tensile and permeability compared to ordinary cement. This research aims to know the extent to which some of the physical and mechanical properties of cement mortar, such as compressive strength, flexural and tensile strength, are improved upon weight substitution of specific polymeric materials with high efficiency, such as, silica fume .styrene-butadiene, styrene- acrylic in low weight ratio so that it does not add a high economic cost to the production of therequired concrete .for specific uses and sheds light on the effect of different temperatures on the properties where studied in this study . The study showed that the addition of polymeric materials (Glenium 51, silica fume, styrene –butadiene) with different weight ratio of cement weight at 20°C led to obtaining the highest compressive strength, flexural and tensile strength at the optimum level to the development and improvement of properties. Mechanical and physical cement mortar compared to the reference cement free of additives .As for the use of styrene –acrylic, it had a negative effect and led to a decrease in the compressive and tensile strength .especially in the later ages compared to the reference cement. The optimum ratio of Glenium51 was added to the optimum ratio of each material separately and the mixture was added to the cement mortar at different temperatures( 7, 20, 55 )°C .The effect of additives on the properties of the cement mortar was studied. Also, a mixture (Glenium51, silica fume, styrene-butadiene, styrene-acrylic) was added in the optimum proportions for each material to the cement mortar at different temperatures, and this addition led to increase on compressive, flexural and tensile strength at all temperatures compared with reference cement. Silica fume, styrene-butadiene rubber and styrene acrylic were added separately to the cement mortar without Glenium51, then a mixture of silica fume, styrene-butadiene, and styrene-acrylic was added to the cement mortar .The results showed that the compressive, flexural and tensile strength of cement mortar increase while styrene acrylic decrease these properties when compared with the reference mixture.In addition, the study showed the effect of temperature to the properties of added polymers with cement mortar, All experiments were performed at different temperatures (The temperature which Iraq's climate is exposed under natural conditions.All experiments were conducted at different temperatures (7, 20, 55)°C respectively, to show the effect of degrees on cement compressive strength, which the degree7 represents in winter, 20 in spring and autumn, and 55 in summer.