Weight Of Cementitious Materials Research Articles

Optimum rice husk ash content and bacterial concentration in self-compacting concrete

This study is aimed at optimizing the rice husk ash (RHA) content and bacterial concentration in self-compacting concrete (SCC). For this purpose, cement was partially replaced with RHA at 0%, 5%, 10%, 15%, 20%, 25%, and 30% by weight of cement. In addition, micro-silica (MS) was added to all mixes at a dosage of 10% by weight of cementitious materials. The mix with the optimum RHA content was supplied with bacterial cells with concentrations of 103, 105, and 107 cells/ml to reduce the formation of micro-cracks. The RHA concretes showed reduced workability with increasing RHA content. Energy-dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM) analyses were performed on the control mix, optimal RHA mix, and bacterial concrete mixes. The best strength properties were achieved for a bacterial concentration of 105 cells/ml, whereas the best durability properties were obtained for a bacterial concentration of 107 cells/ml. The 28-day compressive strength of the optimal mix containing 15% RHA increased by 12% compared to the control mix, and the increase in strength reached 21% with inclusion of bacteria at the optimal concentration. The optimal RHA content with the maximum bacterial concentration led to 415% increase in electrical resistivity and reduced the permeability-related properties up to 80% with respect to the control mix. According to the results, it is possible to produce an SCC with low permeability and high strength and filling ability with inclusion of specific RHA dosage and bacterial cell concentration.

Evaluating the impact resistance of roller compacted concrete containing crumb rubber and nanosilica using response surface methodology and Weibull distribution

Purpose Roller compacted concrete (RCC) pavement is used in areas subjected to heavy impact loads; therefore, higher impact resistance is a desirable property of consideration. This study aims to investigate the effect of partial replacement of fine aggregate with crumb rubber (CR) and the addition of nanosilica (NS) by weight of cementitious materials on the impact resistance of roller compacted rubbercrete (RCR). Design/methodology/approach Four replacement levels of CR (0, 10, 20 and 30 per cent) and four addition levels of NS (0, 1, 2 and 3 per cent) were considered. The impact resistance test was carried out using the drop weight test recommended by ACI 544. Findings The results showed that the impact resistance of RCR increases with an increase in both CR and NS addition, though for CR above 20 per cent, sudden drop in impact resistance was observed. However, NS reduces the ductility of RCR by decreasing the post-cracking impact resistance. Response surface methodology was used to develop models for predicting the impact resistance of RCR, and the developed models showed a high degree of correlation. As a result of wide variations in the impact drop test data, two-parameter Weibull distribution function was used for the data analysis, and it was found that the probabilistic distributions of the first crack and ultimate failure impact resistance follow the two-parameter Weibull distribution function. Originality/value In this work, the effect of partial replacement of fine aggregate with CR and the addition of NS by weight of cementitious materials on the impact resistance of RCC pavement has been investigated. CR has been used to increase the impact resistance of RCC Pavement.

Durability performance of high volume fly ash roller compacted concrete pavement containing crumb rubber and nano silica

ABSTRACT This study investigated the effect of a hybrid of crumb rubber and nano silica on the durability performance (Porosity and Permeability) and skid resistance of high volume fly ash (HVFA) roller compacted concrete (RCC) pavement. The HVFA RCC pavement was developed with 50% cement by volume replaced using fly ash. Crumb rubber was used to partially replace fine aggregate at varying percentages, i.e. 0%, 10%, 20%, and 30% by volume replacement. Nano silica was added by weight of cementitious materials at variations of 0%, 1%, 2%, and 3%. The Vebe consistency, water absorption, and mercury intrusion porosimetry were used to measure the consistency, permeability, and porosity of the HVFA RCC pavement, respectively. The skid resistance was measured in terms of the British Pendulum Number (BPN) using the British Pendulum Tester (BPT). The result findings showed that the HVFA increased the consistency, rate of water absorption, and porosity of the RCC pavement. Furthermore, the consistency, water absorption, and porosity of the HVFA RCC pavement increased with an increase in the partial replacement of the fine aggregate with crumb rubber. On the contrary, the addition of nano silica decreased the consistency, rate of water absorption, and porosity of the HVFA RCC pavement. This was due to the larger surface area, finer size, and physiochemical reaction of the nano silica which resulted in pore structure refinement in the hardened matrix of the HVFA RCC pavement by filling the voids within the interconnected pores thereby breaking the interconnectivity and reducing its diameter. The results of the skid resistance showed that incorporation of 10% crumb rubber as the replacement to fine aggregate and addition of up to 2% nano silica by weight of cementitious materials increased the skid resistance of the HVFA RCC pavement.

High volume fly ash mortar containing nano-calcium carbonate as a sustainable cementitious material: microstructure and strength development

The mechanisms underlying the effects of nano-calcium carbonate (NC) on the strength of high volume fly ash (FA) mortar are discussed. Two NCs are used as 2%, 4%, 6%, and 8% by weight of cementitious materials. Hydrated products of fly ash mortar containing NC was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TG) and differential thermal gravity (DTG) analysis. Results indicate that NC could improve strength of FA mortar due to the more rapid growth of hydrated products induced by NC through additional nucleation sites. Corresponding to the highest measured strength of FA mortar, the optimal contents of NC are around 2%. In addition, the presence of 2% NC improved the microstructure of FA mortar after 180 days due to the formation of calcium carbonaluminate hydrate.

EFFECT OF CRUMB RUBBER AND NANO SILICA ON THE CREEP AND DRYING SHRINKAGE OF ROLLER COMPACTED CONCRETE PAVEMENT

Roller compacted concrete (RCC) pavement is used mostly for heavy duty vehicle operations such as log sorting yards, intermodal yards for containers, parking areas for military vehicles and trucks and automobiles, and aircraft parking ramps. Therefore, it is subjected to long-term loading which can cause permanent deformation. Therefore in this study, the long-term creep and drying shrinkage of RCC pavement up to 1 year was studied. High volume fly ash (HVFA) RCC pavement was developed by replacing 50% cement with fly ash. A total of five RCC pavements were developed; one control mixture, two RCC pavement mixtures and two HVFA RCC pavement mixtures. The four mixtures were developed by replacing 10% fine aggregate with crumb rubber by volume and addition of 1% nano silica by weight of cementitious materials. The results showed that the creep and drying shrinkage of RCC pavement increases with time, and with the incorporation of crumb rubber and HVFA and decreases with the addition of nano-silica. The creep strain of RCC pavement mixtures can be predicted at any given time using their compressive strength and age of testing.

Mechanical properties and performance of high volume fly ash roller compacted concrete containing crumb rubber and nano silica

This study deals with the development of an environmentally sustainable roller-compacted concrete (RCC) using high-volume fly ash (HVFA) and crumb rubber as partial replacement for cement and fine aggregate respectively, and nano-silica as an additive to cementitious materials. Response surface methodology (RSM) was used to design, develop statistical models, and carry out the optimization for the mixtures using the variables crumb rubber, HVFA, and nano-silica. The responses used for the RSM are compressive, flexural, and splitting tensile strengths. The proposed models demonstrated a high correlation among the variables and responses. An optimised HVFA RCC mix can be achieved by partially replacing 10% fine aggregate with crumb rubber by volume, replacing 53.72% of cement with fly ash by volume, and the addition of 1.22% nano-silica by weight of cementitious materials. Further experimental investigations showed that the HVFA RCC pavement exhibited lower fresh density, Vebe time, compressive strength, splitting tensile strength, flexural strength, modulus of elasticity, abrasion resistance, and impact resistance compared to conventional (control) RCC pavement. These effects further escalate with increase in partial replacement of fine aggregate with crumb rubber. On the other hand, nano-silica increases the mechanical properties and performance of HVFA RCC pavement with or without crumb rubber. This is because of the ability of nano-silica to partially mitigate the negative effect of crumb rubber on the properties of HVFA RCC by densifying the interfacial transition zone between the cement matrix and crumb rubber and filling the pores in the hardened cement matrix. Furthermore, nano-silica partially ignited the pozzolanic reactivity of fly ash at early ages which leads to higher performance of HVFA RCC pavement at early age.

Influence of activation of fly ash on the mechanical properties of concrete

The use of high volume fly ash as a partial replacement of cement in concrete reduces environmental pollution and conserves natural resources. This study presents the results of an experimental investigation to find out the effect of chemical activation of class F fly ash to overcome the low early strength problem. The replacement ratio of Portland cement with fly ash was 40%. Four different chemical activators were used in the study; 2.5% Na2SO4, 2.5% NaOH, 3.0% (Na2SiO3 and CaO) by ratio (1:8) and 4% Aquis Na2SiO3. Concrete strength was investigated at room temperature and after exposure to elevated temperature. Glass fibers were added by ratio 0.7% to improve concrete ductility. Test results indicated that aquis Na2SiO3 activator is the superior activator for fly ash in view of enhancing concrete compressive, splitting tensile and flexural strengths at early ages. Besides, a significant increase in concrete strength was obtained at elevated temperatures. Adding glass fibers in the ratio of 0.7% by weight of cementitious material with activated FA by using aquis Na2SiO3 greatly enhances the splitting tensile and flexural strengths at normal and elevated temperature.

SUSTAINABLE PERFORMANCE OF REACTIVE POWDER CONCRETE BY USING NANO META KAOLIN

This investigation aimed to study the sustainable effect of Nano Meta Kaolin (NMK ) on some properties of reactive powder concrete. In this study, Reactive powder concrete (RPC) specimens were designed, prepared and cured for different ages (7, 28 and 60) days. The suggested specimens dimensions consist of cubes with (50mm), cylinders with (100×200 mm) and cylinders with (150×300 mm), to study compressive strength, splitting indirect tensile strength, and modulus of elasticity with varied Nano Meta Kaolin content (0, 2%, 3.5% and 5%) by weight of cementitious materials as an addition. All specimens were cured with hot water treatment (60 Cº) for 12 hours, and then put in normal water until testing day. It was found that the compressive strength of concrete with the Nano Meta Kaolin higher than the reference concrete, and also the same trend was observed for the splitting tensile strength. improvement in the compressive strength at 28 days when using (2,3.5, 5%) Nano Meta Kaolin has been about (5-15%), While the improvement in the splitting tensile strength was (3-7%), and the improvement in modulus of elasticity was (10-26%).

Study some mechanical properties of self-compacting concrete with nano silica under severe saline environment conditions

The main aim of this research is to evaluate the performance of Nano silica self-compacting concrete which is subjected to severe saline conditions that contain sulfates and chlorides at concentrations similar to those existing in the soils and ground water of the middle and southern parts of Iraq. For this purpose, ordinary and sulfate resistant Portland cement without and with 3% Nano silica addition by weight of cementitious materials were used. Splitting tensile strength, flexural strength, static modulus of elasticity and ultrasonic pulse velocity were investigated for all exposure conditions and all types of mixes of self-compacting concrete at ages of 28, 60, 90, 120 and 180 days. Test results revealed that the inclusion of Nano Silica in concrete mixes improved clearly the mechanical properties of self-compacting concrete compared with reference concrete.

Hydration characteristics and structure formation of cement pastes containing metakaolin

Metakaolin (MK) is one of the most effective mineral admixtures for cement-based composites. The deposits of kaolin clays are wide-spread in the world. Metakaolin is comparable to silica fume as an active mineral admixture for cement-based composites. In this paper, the rheological and mechanical properties of cement paste containing metakaolin are investigated. The effect of MK is more evident at “tight” hydration conditions within mixtures with low water-cement ratio, provided by application of superplasticizers. The cement is replaced with 0 to 15% metakaolin, and superplasticizer content ranged from 0 to 1.5% by weight of cementitious materials (i.e. cement and metakaolin). An equation is derived to describe the relationship between the metakaolin and superplasticizer content and consistency of pastes. There is a linear dependence between metakalolin content and water demand. Second-degree polynomial describe the influence of superplasticizer content. The application of SP and MK may produce cement-water suspensions with water-retaining capacity at 50-70% higher than control suspensions. The investigation of initial structure forming of cement pastes with SP-MK composite admixture indicates the extension of coagulation structure forming phase comparing to the pastes without additives. Crystallization stage was characterized by more intensive strengthening of the paste with SP-MK admixture comparing to the paste without admixtures and paste with SP. Results on the porosity parameters for hardened cement paste indicate a decrease in the average diameter of pores and refinement of pore structure in the presence of metakaolin. A finer pore structure associated with an increase in strength. X-ray analysis data reveal a growing number of small-crystalline low-alkaline calcium hydrosilicates and reducing portlandite content, when MK dosage increases. Scanning electron microscopy (SEM) data confirm, that hardened cement paste containing MK has crystalline structure with dominance of partially crystalized hydrosilicates and gel-like formations.

Effect of different curing conditions on the mechanical properties of reactive powder concrete

Reactive Powder Concrete (RPC) is an ultra-high performance concrete which has superior mechanical and physical properties, and composed of cement and very fine powders such as quartz sand and silica fume with very low water/ binder ratio and Superplasticizer. Heat treatment is a well-known method that can further improve the performance of (RPC). The current research including an experimental study of the effect of different curing conditions on mechanical properties of reactive powder concrete (compressive strength, modulus of rupture and splitting tensile strength), the curing conditions includes three type of curing; immersion in water at temperature of 35 OC (which is considered as the reference-curing situation), immersion in water at temperature of 90 OC for 5 hours daily and curing with hot steam for 5 hours daily) until 28 days according to ASTM C684-99 [8]. This research includes also the study of effect of adding silica fume as percentage of cement weight on mechanical properties of reactive powder concrete for different percentage ratios (5%,10% and 15%). Super plasticizer is also used with ratio of (1.8%) by weight of cementitious material; constant water cement ratio (0.24) was used for all mixes. For each reactive concrete mix, it has been cast into a cubes of (150*150*150) (to conduct the compression test), a cylinders of 150mm diameter with 300mm height (to conduct split test) and prisms of (500*100*100)mm to conduct the modulus of rupture test. The results showed that the best method of curing (according to its enhancing the RPC mechanical properties) is the method of immersion in hot water at temperature 90 OC for the all silica fume percentages, and the best used silica fume percentage was (10%) for the all used curing methods.

Hydration characteristics and structure formation of cement pastes containing metakaolin

Metakaolin (MK) is one of the most effective mineral admixtures for cement-based composites. The deposits of kaolin clays are wide-spread in the world. Metakaolin is comparable to silica fume as an active mineral admixture for cement-based composites. In this paper, the rheological and mechanical properties of cement paste containing metakaolin are investigated. The effect of MK is more evident at “tight” hydration conditions within mixtures with low water-cement ratio, provided by application of superplasticizers. The cement is replaced with 0 to 15% metakaolin, and superplasticizer content ranged from 0 to 1.5% by weight of cementitious materials (i.e. cement and metakaolin). An equation is derived to describe the relationship between the metakaolin and superplasticizer content and consistency of pastes. There is a linear dependence between metakalolin content and water demand. Second-degree polynomial describe the influence of superplasticizer content. The application of SP and MK may produce cement-water suspensions with water-retaining capacity at 50-70% higher than control suspensions. The investigation of initial structure forming of cement pastes with SP-MK composite admixture indicates the extension of coagulation structure forming phase comparing to the pastes without additives. Crystallization stage was characterized by more intensive strengthening of the paste with SP-MK admixture comparing to the paste without admixtures and paste with SP. Results on the porosity parameters for hardened cement paste indicate a decrease in the average diameter of pores and refinement of pore structure in the presence of metakaolin. A finer pore structure associated with an increase in strength. X-ray analysis data reveal a growing number of small-crystalline low-alkaline calcium hydrosilicates and reducing portlandite content, when MK dosage increases. Scanning electron microscopy (SEM) data confirm, that hardened cement paste containing MK has crystalline structure with dominance of partially crystalized hydrosilicates and gel-like formations.

The effect of SiO2 nanoparticles derived from hydrothermal solutions on the performance of portland cement based materials

The nanoparticles of SiO2 were used in cement systems to modify the rheological behavior, to enhance the reactivity of supplementary cementitious materials, and also to improve the strength and durability. In this research, low-cost nano-SiO2 particles from natural hydrothermal solutions obtained by membrane ultrafiltration and, optionally, by cryochemical vacuum sublimation drying, were evaluated in portland cement based systems. The SiO2-rich solutions were obtained from the wells of Mutnovsky geothermal power station (Far East of Russia). The constant nano-SiO2 dosage of 0.25% (as a solid material by weight of cementitious materials) was used to compare the cement systems with different nanoparticles against a reference mortar and a commercially available nano-SiO2. Nanoparticles were characterized by X-Ray Diffraction (XRD), BET Surface Area, Scanning Electron Microscope (SEM) and Fourier Transform Infrared (FTIR) spectroscopy techniques. It was demonstrated that the addition of polycarboxylate ether superplasticizer and the dispersion treatment using an ultrasound processor can be used to facilitate the distribution of nano-SiO2 particles in the mixing water. The effect of nano-SiO2 particles in portland cement mortars was investigated by evaluating the flow, heat of hydration and compressive strength development. It was demonstrated that the use of nano-SiO2 particles can reduce the segregation and improve strength properties.

The use of a volcanic material as filler in self-compacting concrete production for lower strength applications

This study evaluates the use of large amounts of fine powders (fillers) derived from a Colombian volcanic material into the production of self-compacting concrete (SCC) for lower strength applications. The effects on SCC properties were studied with the incorporation of up to 50% of volcanic material of Tolima (MVT) as a partial substitute of the total weight of Portland cement. The workability was determined through slump flow, V-funnel, and L-box test. The compressive strength results were analyzed statistically by MINITAB. These demonstrated that 30% (by total weight of cementitious material) was the maximum allowable percentage of MVT to be used in the production of SCCs. Based on this, mechanical and permeability properties of SCC MVT 30% were evaluated at 28, 90 y 360 curing days. SCC MVT 30% exhibited compressive strength of 21 and 27 MPa after 28 and 360 days of curing, respectively.

Study of Early Age Properties and Behaviour of Concrete with GGBS as Partial Replacement of Cement

Ground granulated blast furnace slag (GGBS) is used as alternative binder material for cement in the concrete. The use of GGBS in concrete production contributes to the savings of natural resources and energy spent in cement manufacturing process and also to reduce CO 2 emissions and environmental impact. In this research, GGBS is used as binder material for Ordinary Portland Cement in concrete by replacing cement up to 45% by weight of cementitious material. This investigation is carried out to study the fresh properties, early age strength properties and mechanical properties such as compressive strength of concrete specimen by partial replacement of cement with GGBS up to 45% and compared with referral mix. A total of four concrete mix proportion (NC, Mix 1-15%, Mix 2-30%, Mix 3- 5%) with and without GGBS were made. The compression test were carried out to determine the strength properties of concrete at the age of 3 days, 7days and 28 days. The test result shows that the 28days compressive strength at 15 % GGBS content for M35 and M40 grade of concrete is comparable with referral mix. It is observed that concrete made with GGBS have lower strength at early ages, but gain strength more steadily than equivalent concrete made with Portland cement which is having higher early age strength but does not rise rapidly on the later stages. The M40 grade concrete has better workability when compared with M35 grade concrete.

Mechanical properties of ultra-high-performance concrete enhanced with graphite nanoplatelets and carbon nanofibers

Abstract Effects of graphite nanoplatelets (GNPs) and carbon nanofibers (CNFs) on mechanical properties of ultra-high-performance concrete (UHPC) are investigated. A non-proprietary UHPC mixture composed of 0.5% steel micro fibers, 5% silica fume, and 40% fly ash was used. The content of the nanomaterials ranged from 0 to 0.3% by weight of cementitious materials. The nanomaterials were dispersed using optimized surfactant content and ultra-sonification to ensure uniform dispersion in the UHPC mixture. As the content of nanomaterials is increased from 0 to 0.3%, the tensile strength and energy absorption capacity can be increased by 56% and 187%, respectively; the flexural strength and toughness can be increased by 59% and 276%, respectively. At 0.2% of GNPs, the UHPCs exhibited “strain-hardening” in tension and in flexure.

Experimental Investigation on Mechanical Properties of Hybrid Fiber Reinforced Quaternary Cement Concrete

Mechanical properties of quaternary blending cement concrete reinforced with hybrid fibers are evaluated in this experimental study. The steel fibers were added at volume fractions of 0.5%, 1%, and 1.5 % and polypropylene fibers were added at 0.25% and 0.5% by weight of cementitious materials in the concrete mix individually and in hybrid form to determine the compressive strength, split tensile strength, flexural strength and impact resistance for all the mixes. The experimental results revealed that fiber addition improves the mechanical properties and also the ductility and energy absorption of the concrete. The results also demonstrate that the hybrid steel – polypropylene fiber reinforced concrete performs better in compressive strength, split tensile strength, flexural strength and impact resistance than mono steel and mono polypropylene fiber reinforced concrete.

Use of Thermoplastic Polymer in Mortar Composites to Improve its Chloride Penetration Resistance

This paper presents a study of the resistance to chloride penetration of blended Portland cement mortar containing thermoplastic waste polymer polyethylene terephthalate (TWPET). Composite TWPET-mortars are often presented as the materials of the future in reason of their potential for innovation and advantages that offer. In fact, the use of TWPET percentages as a cement substitution reduces energy costs; address problems related to environmental pollution by CO2 emissions and repairs various reinforced concrete structures. Blended Portland cement (CPJ) is partially replaced with TWPET at the amounts of 2%, 4% and 6% by weight of cementitious materials. Chloride penetration depth of full and partial immersions in 3% NaCl solution, rapid chloride permeability test (RCPT) after 28, 90 and 120 days, sorptivity, leaching test and flexural strength of thermoplastic-mortar composites (TMCs) were determined. Test results reveal that the resistance to chloride penetration of TMCs improves substantially with partial replacement of CPJ with TWPET and without significantly affecting the flexural strength in tap water. The chemical resistance is higher with an increase in the replacement level. So, sorptivity, the chloride ion penetration depth, apparent chloride ion diffusion coefficient, the total charge passed in coulombs and leached depth measurements of the TMCs are much smaller than those of reference mortar. The formations which appear such as different calcium salts were determined by X-ray diffraction. These results take into account the use of waste plastics in the manufacture of mortars modified which can be both recommended for preventing the chloride-induced corrosion of the steel in various reinforced concrete structures and participate greatly in the environment preservation.

Experimental Investigation on Mechanical Properties of Hybrid Fiber Reinforced Quaternary Cement Concrete

Mechanical properties of quaternary blending cement concrete reinforced with hybrid fibers are evaluated in this experimental study. The steel fibers were added at volume fractions of 0.5%, 1%, and 1.5 % and polypropylene fibers were added at 0.25% and 0.5% by weight of cementitious materials in the concrete mix individually and in hybrid form to determine the compressive strength, split tensile strength, flexural strength and impact resistance for all the mixes. The experimental results revealed that fiber addition improves the mechanical properties and also the ductility and energy absorption of the concrete. The results also demonstrate that the hybrid steel – polypropylene fiber reinforced concrete performs better in compressive strength, split tensile strength, flexural strength and impact resistance than mono steel and mono polypropylene fiber reinforced concrete.

EXPERIMENTAL INVESTIGATION ON EFFECT OF MINERAL ADMIXTURES ON HIGH PERFORMANCE CONCRETE WITH VARIOUS W/B RATIOS

Now a day's high performance concrete is globally used in the infrastructure industry for strong and durable structure, to produced high performance concrete various supplementary cementitious material are used as mineral admixture. This research involves the use of Fly ash, Alccofine and Silica fume at various proportions to enhance the compressive strength of high performance concrete. the investigation was carried out by replacing 10% fly ash along with 17% of alccofine and 10% fly ash along with 17% of silica fume by weight of cementitious material. To cover a wide range of compressive strength of concrete various water binder ratio (W/b) of 0.25, 0.3 and 0.35 were used. The effect of various parameters such as percentage replacement of mineral admixture, water to binder ratio and corresponding compressive strength is studied on fresh and hardened state of concrete. The study mainly consisted of establishing relation between these parameters graphically. Investigation demonstrates that alcofine performs batter than that of silica fume along with fly ash in fresh and harden state of concrete.