V-funnel Flow Research Articles

A review on rheological behaviour of alkali activated materials and the influence of composition factors

Rheology is the study of how materials change shape and flow when they are subjected to stress. Along with the empirical evaluation methods of workability such as slump value, diameter of slump flow, v-funnel flow time and vee-bee, fundamental characteristics which control rheology such as viscosity, yield stress and thixotropy has important role to define the change in characteristics of concrete with time. Alkali Activated Materials (AAM) are aluminosilicate materials suitably activated using alkaline solutions. Commonly used aluminosilicate materials are fly ash, slag, metakaolin, red mud etc. Hydroxide and silicates of sodium and potassium are the most widely used alkaline activators. As far as the strength and durability is concerned, AAM has emerged as a novel material capable to swap out the typical concrete binder, Ordinary Portland Cement (OPC). The characterization of AAM such as valorization of industrial waste materials, low carbon foot print, sustainable and economical construction material etc. has resulted in increased research activities. But the fast-setting characteristics and low workability of AAM reduces its wide acceptance. Analysing rheological parameters are one of the best approaches to identify the reason behind this fast setting and low workability. This paper comprehensively reviews studies on rheology of AAM, to identify the importance of rheological parameters on fresh properties of AAM. The control of factors such as types of precursors, characteristics of activator solution, silica modulus of activator, admixtures, water to binder ratio, mixing time, temperature etc. on the rheological behaviour of AAM were thoroughly reviewed. The suitability of Bingham model to predict the rheological behaviour of AAM and the need of proper guidelines on the rheological characteristics of AAM to extent its application was also reviewed.

Rheological behavior and key properties of metakaolin and nano-SiO2 blended fibrous self-compacting concretes

The basic aim of the study herein is to experimentally determine and evaluate the influences of nano-SiO2 and metakaolin incorporation on the rheological and workability characteristics as well as mechanical properties of fibrous self-compacting concretes (SCCs). For that purpose, two SCC series were designed at a constant total binder content of 550 kg/m3 and a water-to-binder (w/b) ratio of 0.37. The first SCC series were manufactured as nonfibrous while the second series was produced as a steel fiber reinforced at a volume fraction of 0.5 %. In all SCC mixtures, 30 % of the total binder content was fly ash by weight. In both series, the cement (70 % of the total binder content) was partially replaced with metakaolin (0 % and 10 %) and nano-SiO2 (0 %, 2 %, and 4 %) by weight. In this way, a total of 12 SCC mixtures were designed and manufactured. The ICAR rheometer was employed to carry out the rheology measurements of the mixtures and the modified Bingham model was applied to describe the rheological behavior. Fresh characteristics of mixtures were investigated in terms of slump flow diameter, T50 slump flow time, V-funnel flow time, and l-box height ratio and flow times. In addition, the fundamental mechanical properties like compressive strength, elastic modulus, and splitting tensile strength were determined at the ages of 28 and 90 days. The plain SCC mixture had the slump flow diameter, T50 slump flow time, V-funnel flow time, and l-box height ratio of 750 mm, 2.29 s, 8.3 s, and 0.96, respectively. Metakaolin and nano-SiO2 replacements and steel fiber addition resulted in lower self-compactibility with up to 7% reduction in slump flow diameters. Especially the steel fiber particles played a blocking role and, thereby, caused a decrease in the flowability and passing ability of the mixtures by about 8–10 %. A similar effect was observed in the rheology measurement. The mixtures involving nano-SiO2, metakaolin, and/or steel fiber behaved more cohesively and viscously. On the other hand, the 28-day (90-day) compressive and splitting tensile strengths and modulus of elasticity of plain SCC mixture were respectively 67.5 (76.4) MPa, 3.95 (4.32) MPa, and 37.9 (39.4) GPa. Both metakaolin and nano-SiO2 replacements led to a significant increase in the strength performance of the mixtures, especially at a later age. However, it is hard to state whether steel fiber addition has a distinct and systematic effect on the compressive strength and modulus of elasticity. In contrast, it was clearly observed that steel fiber incorporation remarkably enhanced the mixtures’ tensile performance, resulting in more than 20 % and about 17–24 % increases in 28- and 90-day splitting tensile strengths, respectively.

Predicting the rheological flow of fresh self-consolidating concrete mixed with limestone powder for slump, V-funnel, L-box and Orimet models using artificial intelligence techniques

In this paper, selected materials that influence the viscosity of the self-consolidating concrete (SCC) are introduced like the Limestone Powder (LSP), the High Range Water Reducing Admixture (HRWRA), which reduce the interparticle force between concrete constituents like the aggregates, and other superplasticizers. Moreover, in serious attempts to design the SCC for different infrastructure requirements, there have been repeated laboratory visits, which need to be reduced. In this research paper, the artificial intelligence (AI) methods: Artificial Neural Network (ANN), Evolutionary Polynomial Regression (EPR), and Genetic programming (GP) have been deployed to predict the slump flow (SF), V-funnel flow time (VFFT), L-box ratio (LBR) or passing ratio, and Orimet flow time (OFT) of LSP-admixed SCC. The independent variables of the predictive model were cement, LSP, water, water-binder ratio, HRWRA, sand, and coarse aggregates of 4/8 mm and 8/16 mm sizes. The flow tests were conducted after 5 minutes of waiting time after mixing. The model results showed ANN with superior intelligent learning ability over previous models in terms of overall performance.

Combined Effects of Waste Glass and Nano-Silica Powder on Workability, Durability and Mechanical Properties of Fiber- Reinforced Self-Compacting Mortar

This research aims to combine the effects of waste glass and Nano-silica powder on the properties of fiber-reinforced self-compacting mortar. A detailed study was undertaken to investigate the effect of different glass powder contents as cement replacement on the behavior of mortar. For this purpose, Portland cement was partially replaced by 10%, 15%, and 20% waste glass powder alone, and then in combination with 2% substitution levels for Nano-silica. The amount of water-binder ratio and cementitious materials content were considered constant. Fresh properties of specimens were determined using slump flow, and vfunnel flow time tests, mechanical properties were determined by compressive strength, and tensile strength tests, and durability characteristics evaluated by water absorption, and resistance to sulfuric acid attack. Microstructural morphology of specimens was also assessed by scanning electron microscopy. It was observed that the workability slightly decreased and improved mechanical and durability properties could be achieved. The SEM micrographs illustrated more densified pore structure of the mortars containing waste glass powder which leads to increase in strength and durability of specimens.

The mechanical and durability behaviour of sustainable self-compacting concrete partially contained waste plastic as fine aggregate

ABSTRACT Annually, the disposal of low-density polyethylene (LDP) and waste ceramics have increased, which have a negative impact on environmental pollution. Thus, construction material sustainability can be achieved through the use of these wastes in manufacturing concrete. This experimental investigation aimed to assess the behaviour of self-compacting concrete (SCC) incorporating LDP. A total of six concrete mixes were designed with various volume percentages of 0, 6, 12, 18, 24 and 30% of LDP as fine aggregate and used waste ceramic powder 30% (by weight) as partial substitution of cement for all mixtures. The experimental parameters are composed of fresh properties (fresh density, segregation analysis, H2/H1 ratio, slump flow diameter, V-funnel and T500 slump flow time) and hardened properties of dry density, ultrasonic pulse velocity, compressive and flexural strengths. However, the samples were exposed to elevated temperatures at 25 and 800°C for 3 h to examine dry density and compressive strength. The results showed that the dry density and compressive strength with 30% LDP were decreased by 4.9 and 37.17%, respectively, after being exposed to 800°C. From the compressive strength results, it was determined that all the mixes before and after exposure to elevated temperatures were suitable for structural purposes.

Performance of Self-Compacting mortars modified with Nanoparticles: A systematic review and modeling

During the transition of one material from macro- to nano-range size, considerable changes occur in the electron conductivity, optical absorption, mechanical properties, chemical reacting activity, and surface morphology. These changes can be advantageous in the production of new mixture composites. Due to the need for developing improved infrastructure, new and high-performance materials should also be developed. In this regard, to improve the performance of concrete mixtures, several methods have been investigated, including using nanoparticles (NPs) to enhance various characteristics of the concrete composite like improving fresh and mechanical properties of self-compacting concrete (SCC) as well as improving permeability and absorption capacity of the composite by providing extremely fine particles to fill micro-pores and voids.In this paper, a state-of-the-art review was carried out on the influence of various NPs inclusion on the fresh, mechanical, and durability properties of self-compacting mortars (SCM). So that current and most recent studies previously published were investigated to highlight the influences of different NPs on the slump flow diameter, V-funnel flow time, compression and flexural strengths, water absorption, chloride penetration, and electrical resistivity. Moreover, the main section of this study was devoted to proposing different models, including nonlinear model (NLR), multi-logistic model (MLR), and artificial neural network (ANN), to predict the compressive strength (CS) of SCMs modified with NPs. Based on the analyzed data, it was illustrated that the addition of NPs into SCMs significantly enhances the fresh, mechanical, and durability performance of SCMs. Moreover, the microstructure of SCMs was considerably improved due to the higher specific surface area of NPs and their reaction with undesirable C–H which present in the cement paste matrix to produce additional C-S-H gel.

The influence of pre-coated EGA and aerogel on the properties of lightweight self-compacting cementitious composites

Aerogel and porous lightweight aggregates have adverse impacts on the fresh, mechanical, and water absorption characteristics of concrete. In this study, styrene-butadiene rubber (SBR) and Paraffin were used to coat the lightweight aggregates. The lightweight aggregates were coated in single and double layers. Besides, aerogel particles were also coated with SBR. The properties of the cementitious composites, such as slump flow, T50 flow time, V-funnel flow time, J-ring height, compressive strength, water absorption, porosity, and microstructural analysis, were evaluated. It was observed that single-layer coatings of polymers on EGA improved the slump flow by 6.9% and lowered the water absorption by 26%. The compressive strength of the cementitious composites incorporating polymer coated EGA also improved by 15.9%. Scanning microscopy was used to evaluate the microstructure of EGA, aerogel, and lightweight cementitious composites. A uniform, denser structure of polymer coated EGA was observed in the interfacial transition zone.

Prediction of rheological behavior of self-compacting concrete by multi-variable regression and artificial neural networks

To control the rheological behavior of self compacting concrete, this study attempts to provide predictive models using a multi-variable regression model and artificial neural networks such as machine learning techniques on a database of 59 samples (average of 354 specimens), collated from literature. The statistical significance of the model coefficients and the coefficient of determination are adopted as criteria to check the performance of the model on test data.Interaction terms such as slump flow diameter, V-Funnel flow time, and L-Box ratio were inferred from literature to improve the efficacy of the predictive modeling. Two approaches for the prediction of yield stress and plastic viscosity are proposed and validated.With an increase in slump flow diameter and V-Funnel flow time, there was a significant increase in yield stress and plastic viscosity from 2.1 Pa and 18.2 Pa.s to 98.6 Pa and 198.8 Pa. s, respectively. A significant decrease in these rheological parameters was noted with an increase in L-Box ratio from 0.5 to 1. Thus, the comparison between the two numerical methods proposed shows that, for datasets with only one output, the multi-variable regression presents an important advantage. Thus, the regression model for the plastic viscosity represents values of R of the order of 0.955, 0.968, and 0.916 in correlation with slump flow diameter, V-Funnel flow time, and L-Box ratio, respectively.

Prediction of plastic viscosity and yield stress of self-compacting concrete using machine learning technics

The use of self-compacting concrete (SCC) is increasing from day to day in many construction sites around the world. This type of concrete is made up of a combination of cementitious materials, sand, water, gravel, and chemical additives.Among the most important parameters for self-compacting concrete we find fluidity quality, generally predicted by plastic viscosity and yield stress values. For a complete characterization, these two parameters are measured by a concrete viscometer. But given its price and the difficulty of handling it on construction sites, there are empirical tests that estimate these parameters.In this sense, the objective of this work is to predict the rheological behavior (plastic viscosity and yield stress) of a SCC from the rheological parameters experimentally measured by empirical tests (slump flow diameter, V-Funnel flow time, and L-Box ratio).To do this, we used the most famous machine learning algorithms to know: Multiple Linear Regression (MLR), Random Forest (RF), Decision Tree (DT) and Support Sector Machine (SVM). Finally, the best proposed model is given on the basis of a statistical comparison between the different used algorithms.

Combined Effects of Waste Glass and Nano-Silica Powder on Workability, Durability and Mechanical Properties of Fiber- Reinforced Self-Compacting Mortar

This research aims to combine the effects of waste glass and Nano-silica powder on the properties of fiber-reinforced self- compacting mortar. A detailed study was undertaken to investigate the effect of different glass powder contents as cement replacement on the behavior of mortar. For this purpose, Portland cement was partially replaced by 10%, 15%, and 20% waste glass powder alone, and then in combination with 2% substitution levels for Nano-silica. The amount of water-binder ratio and cementitious materials content were considered constant. Fresh properties of specimens were determined using slump flow, and vfunnel flow time tests, mechanical properties were determined by compressive strength, and tensile strength tests, and durability characteristics evaluated by water absorption, and resistance to sulfuric acid attack. Microstructural morphology of specimens was also assessed by scanning electron microscopy. It was observed that the workability slightly decreased and improved mechanical and durability properties could be achieved. The SEM micrographs illustrated more densified pore structure of the mortars containing waste glass powder which leads to increase in strength and durability of specimens.

New test for the determination of static segregation of self-compacting concrete: Three-circles test

Industry and construction operators are looking for a self-compacting concrete (SCC) formulation that is compressive resistant and sufficiently fluid to fill the most complex shapes but at the same time stable enough to avoid aggregate segregation.In contrast, in the literature, no test has been proposed to characterize both the segregation and the fluidity of SCC. In this regard, our experimental study is concerned with the development of a new experimental process characterizing both the spreading and the segregation of SCC. This is a spreading table coupled to the three circles. Such testing should help gain an understanding of the formulation and stability of a mixture made in the laboratory or situ.The assessment of the segregation and the validation of the proposed approach is carried out according to an experimental process on SCCs made with eight types of superplasticizers. The proposed procedure will make it possible to characterize the risk of segregation as a function of the rheological parameters of the SCCs such as slump flow diameter, V-Funnel flow time, L-Box ratio, and sieve stability, as well as according to the mechanical response such as compressive strength at 1, 7 and 28 days.

Modelization of the rheological behavior of self-compacting concrete using artificial neural networks

Self-Compacting Concrete (SCC) is a fluid concrete designed to flow freely through obstacles (reinforcement) in order to completely fill the formwork without segregation or bleeding. The appearance of this class of concrete increases the need to precisely characterize their behavior during flow. At present, there are several empirical tests to characterize a SCC such as slump flow, L-box and V-Funnel, but no correlation, based on artificial intelligence, has been proposed for the determination of the rheological behavior (plastic viscosity and the yield stress) as a function of rheological parameters found during empirical tests (slump flow diameter, H2/H1 ratio of L-Box and V-Funnel flow time). The objective of this study, numerical and experimental, is to search an optimum correlation between behavior and rheological parameters using the techniques of artificial intelligence, and more precisely, artificial neural networks.

Predicting fresh and hardened properties of self-compacting concrete containing fly ash by artificial neural network model

Self-compacting concrete (SCC) is a highly efficient concrete that can be compacted and formed under its own weight without external vibration. However, the constituents of SCC are many and they have diverse material properties. Hence, it is difficult to predict the working performance of SCC with a single factor regression relationship. Therefore, the artificial neural network (ANN) approach is chosen in the present work to simulate the relationship between proportions of constituents and properties of SCC. This paper aims at predicting properties of SCC containing fly ash based on the experimental data available from the literature. The eight input parameters in the proposed models include amounts of cement, water, water to powder ratio, binder, fly ash, coarse aggregate, fine aggregate, and superplasticizers. The four output parameters are V-funnel flow time, slump flow final spread diameter, compressive strength at 28 and 90 days. A procedure to select the number of hidden layer neurons is discussed. Moreover, the parametric analysis of the developed ANN model is conducted to evaluate the effect of input parameters on SCC properties. By comparing the estimated and experimental results, the proposed ANN model shows great potential in predicting the properties of SCC with different percentage volume fractions of fly ash.

Porosity effects on rheological and mechanical behavior of self-compacting concrete

Unlike ordinary concrete, self-compacting concrete (SCC) is a concrete exceptionally fluid throughout the flow process, without reducing the strength of the material once in place. To reduce bleeding and segregation, admixtures and other modifiers are often used. About this and for improving the resistance of mixture to freezing and thawing, higher air contents may be required.In this study, twenty SCC mixes were designed based on AFGC and EFNARC recommendations. An air-entraining admixture (AEA) was added in several percentages, namely in 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95 and 1% of cement weight.Experimental studies have been performed to examine the rheological and mechanical characteristics of SCC's, such as density, plastic viscosity, yield stress, slump flow diameter, L-Box ratio, V-Funnel flow time, sieve stability segregation, Modulus of Elasticity at 28 days, and compressive strength and sonic velocity (at 1, 7, and 28 days) of the SCC using different air content. However, the linear and polynomial regression models between these parameters are proposed. The statistics coefficients such as “Adj. R-Square”, "Pearson's r", “R-Square” and “standard error” are also indicated whose aim is to determine the best model to adopt for the prediction of rheological and mechanical behavior of SCC according to the intrinsic characteristics of the mixture.As the percentage of AEA in the mixture increases, the values of air content, void ratio, water absorption, slump flow diameter, and L-Box ratio increase as well. Conversely to this, the values of fresh and hardened density as well as plastic viscosity, yield stress, V-Funnel flow time, sieve stability, compressive strength and modulus of elasticity as well as sonic velocity decrease as AEA percentage rises.

Fresh, Mechanical, and Durability Properties of Self-Compacting Mortar Incorporating Alumina Nanoparticles and Rice Husk Ash

This paper presents a comprehensive evaluation on self-compacting (SC) mortars incorporating 0, 1, 3, and 5% alumina nanoparticles (NA) as well as 0% and 30% rice husk ash (RHA) used as Portland cement replacement. To evaluate the workability, mechanical, and durability performance of SC mortars incorporating NA and RHA, the fresh properties (slump flow diameter and V-funnel flow time), hardened properties (compressive strength, flexural strength, and ultrasonic pulse velocity), and durability properties (water absorption, rapid chloride permeability, and electrical resistivity) were determined. The results indicated that the addition of NA and RHA has negligible effect on the workability and water absorption rate of the SC mortars. However, significant compressive and flexural strength development was observed in the SC mortars treated with NA or the combination of NA and RHA. The introduction of RHA and NA also reduced the rapid chloride permeability and enhanced the electrical resistivity of the SC mortars significantly. It is concluded that the coexistence of 30% RHA and 3% NA as cement replacement in SC mortars can provide the best mechanical and durability performance.

A Comprehensive Study of the Mechanical and Durability Properties of High-Performance Concrete Materials for Grouting Underwater Foundations of Offshore Wind Turbines.

With the increasing importance of offshore wind turbines, a critical issue in their construction is the high-performance concrete (HPC) used for grouting underwater foundations, as such materials must be better able to withstand the extremes of the surrounding natural environment. This study produced and tested 12 concrete sample types by varying the water/binder ratio (0.28 and 0.30), the replacement ratios for fly ash (0%, 10%, and 20%) and silica fume (0% and 10%), as substitutes for cement, with ground granulated blast-furnace slag at a fixed proportion of 30%. The workability of fresh HPC is discussed with setting time, slump, and V-funnel flow properties. The hardened mechanical properties of the samples were tested at 1, 7, 28, 56, and 91 days, and durability tests were performed at 28, 56, and 91 days. Our results show that both fly ash (at 20%) and silica fume (at 10%) are required for effective filling of interstices and better pozzolanic reactions over time to produce HPC that is durable enough to withstand acid sulfate and chloride ion attacks, and we recommend this admixture for the best proportioning of HPC suitable for constructing offshore wind turbine foundations under the harsh underwater conditions of the Taiwan Bank. We established a model to predict a durability parameter (i.e., chloride permeability) of a sample using another mechanical property (i.e., compressive strength), or vice versa, using the observable relationship between them. This concept can be generalized to other pairs of parameters and across different parametric categories, and the regression model will make future experiments less laborious and time-consuming.

The effect of content and fineness of natural pozzolana on the rheological, mechanical, and durability properties of self-compacting mortar

Mineral admixtures are used in ordinary and self-compacting mortar to reduce carbon dioxide emission and enhance the performance of mortar at the fresh and hardened states. This paper reports the effect of the content and the fineness of natural pozzolana (NP) on rheological, compressive strength, total and autogenous shrinkage properties of self-compacting mortar. Capillary water absorption of self-compacting mortar was also investigated. Natural pozzolana was used as a partial cement replacement with two levels (15%wt. And 30%wt.) and ground to three specific surface Blaine (SSB) fineness measurements 350 m2/kg, 420 m2/kg and 500 m2/kg. Cement content, water to-binder ratio and superplasticizer content were kept constant for all self-compacting concrete mixtures. Rheological tests were conducted by measuring slump flow and V-funnel flow tests as well as using a rheometer to measure plastic viscosity and yield stress. Compressive strengths of self-compacting concretes were determined at 1, 7, 28, 56, 90 and 180 days of curing. Total and autogenous shrinkage were measured during three months and capillary water absorption of self-compacting mortar was also investigated after 90 days of water curing. The results indicated that the increase of replacement level of natural pozzolana affects negatively the rheological properties of self-compacting mortar. The same tendency is observed as the specific surface Blaine fineness increased. However, in the long-term (beyond 28 days of curing), the compressive strength of NP mixes exceeds that of control mortar. The increase of the fineness of natural pozzolana enhances compressive strength at later age but increases both the total and autogenous shrinkage compared with control mortar. It was observed that increasing the percentage of natural pozzolana generates an increase in water capillary absorption. However, increasing the fineness of natural pozzolana results in slightly lower water absorption of mortar.

Ultra-fine sediment of Changjiang estuary as binder replacement in self-compacting mortar: Rheological, hydration and hardened properties

Managing and dredging of ultra-fine sediment (UFS) in river estuaries becomes an environmental challenge due to its threat to the ecosystem. However, upcycling of UFS for the production of self-compacting mortar (SCM) could be a step toward sustainable waste management and yield the special rheological properties that required for SCM. This paper used UFS to replace cement at ratios of 0%, 5%, 10%, 15%, 20%, 25% and 30% to evaluate the packing density, hydration heat, rheological, fresh and hardened properties of SCM. The microstructure of SCM samples was also characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that all the SCM mixtures met the self-compacting characteristics requirement in accordance to EFNARC. The packing density and fluidity (mini-slump flow and V-funnel flow time) improved with 5% of UFS replacement but decreased at a higher replacement level. Furthermore, SCM mixtures containing UFS behaved like a pseudoplastic fluid, while apparent viscosity of SCM with UFS (up to 20%) during 60 min almost remained a constant value. The incorporation of 5%–15% UFS in SCM decreased the 60-min static yield stress. Based on the calorimetry and mechanical results, the presence of UFS decelerated the hydration, and SCM prepared with 5%–15% of UFS was able to retain 90% and 85% of its original flexural and compressive strengths at 91 days, respectively, with a 28-day strength of mortar grade M. SEM images also revealed that the bond between the UFS particles and the C–S–H gel matrix (interfacial transition zone) was weaker compared with that between the standard sand (NS) particles and the C–S–H gel matrix at higher replacement ratios of cement. Overall, based on the mechanical properties and the microstructure observation, it can be concluded that UFS can be effectively utilized at a replacement level of 5%–15% to produce self-compacting mortar with a lower carbon footprint.

Influence of Polypropylene Fibre Factor on Flowability and Mechanical Properties of Self-Compacting Geopolymer.

The possibility of using geopolymer instead of Portland cement could effectively reduce carbon dioxide emissions from cement manufacturing. Fibre-reinforced self-compacting geopolymers have great potential in civil engineering applications, such as chord member grouting for concrete-filled steel tubular truss beams. However, to the best of the authors’ knowledge, the quantitative relationship between FF and the properties of the fibre-reinforced geopolymer has been rarely reported. In this research, 26 groups of mixtures were used to study the influence of the polypropylene fibre factor (FF) on the flowability and mechanical properties and also the compactness of the fibre-reinforced self-compacting geopolymer. At the same volume fraction, geopolymers with long fibres present worse flowability than those having short fibres due to the easier contacting of long fibres. By growing the FF the influence of fibre addition on the V-funnel flow rate is more significant than the slump spread. This can be ascribed to the consequence of fibre addition and friction by the V-funnel which estimates the restrained deformability. For FF lesser than critical factor Fc = 100, influence of fibres is negligible and fibres are far apart from each other and, thus, they cannot restrict cracking under load and transfer the load to improve the mechanical properties. For FF between the Fc = 100 and density factor Fd = 350, a noteworthy enhancement of mechanical properties was obtained and the geopolymer was still adequately workable to flow by weight of self, without any symbols of instability and fibre clumping. Under this condition, better fibre dispersal and reinforcing productivity can lead to better hardened properties. For FF higher than Fd = 350, fibres tend to come to be entwined together and form clumping resulting from the fibre balling, resulting in worse hardened properties. This research offers a sensible basis for the application of the workability regulator of the fresh properties of fibre-reinforced geopolymer as an operative way to basically obtain ideal mechanical properties.

Short-Term Study on Mechanical and Fresh properties of Micro-silica based Self Consolidating Concrete in Nigeria

The ever increasing environmental challenge arising from improper waste management has been a great concern to researchers and the society. One of such industrial waste is micro silica; a bye-product of the Carbothermic reduction of high purity quartz at temperature of about 2000oC in the presence of coke. The finess of this material and its pozollanic nature makes it suitable for use in the production of self-compacting concrete. In this research micro silica was introduced in percentages of, 5, 10 and 15% as partial replacement of cement in the production of self-compacting concrete. The fresh properties were examined using slump flow, T50cm, slump flow, V-funnel and blockage ratio using L-Box. As the Micro silica were introduced, T50cm time increased, Slump flow reduced, V-funnel flow time increased and L-Box value reduced, due to increase in viscosity. Comparing the experimental results with European Federation of National Associations of Representing for Concrete EFNARC 2002, blockage ratio for 15% was below 0.8. The compressive stresses at 28days were higher than the control at 28days compressive stress with 8.6%, 19.04% and 11.9% for 5%, 10% and 15% respectively. Thus, cement can be partially substituted with micro silica up to 15% with improvement in compressive strength in self-compacting concrete.