Self-compacting Paste Research Articles

Optimization of a Self-Compacting Paste Based on Glass Powder Using Mixture Design and the Desirability Function

Abstract The partial replacement of cement by supplementary cementitious materials is an opportunity for reducing fossil energy consumption and greenhouse gas emissions. In this study, forty (40) pastes were formulated by applying a 4-factor mixture plan, consisting of cement, glass powder (GP), superplasticizer and water. Third order models “special cubic” established for the flow time, spreading diameter, and flow velocity, responses were statistically significant. The analysis of the models allowed the study of the individual and combined effects of the different factors, highlighting the predominant effect of the superplasticizer on the dispersion GP fines. The multi-criteria optimization allowed the development of two optimal pastes SCP1 and SCP2 incorporating 25 and 7% GP, respectively. SCP1 was chosen because at this GP amount, unlike at 28 days, the paste presents the best strengths at 90 days with 4.5% increase for flexural tensile strength and 15.69% increase for compressive strength while maintaining satisfactory workability.

Mechanical Properties of Self-Compacting Paste System Using Wood Saw Dust- an Eco-Friendly Application

An attempt is made in the field of high performance self-compacting cementitious system to have an eco-friendly construction material utilizing raw materials, in this case wood waste sawdust. Two different types of wood sawdust (SD) namely, kikar (Vachellia Nilotica) sawdust (KSD) and partal (Abies pindrow) sawdust (PSD) were used with neat Portland cement paste system in replacement mode. The replacement of SD was 3%, 5% and 7% in each case. results showed a consistency in the slight decrease of compressive strengths, the reduction in shrinkage with samples having sawdust (SD) were highly significant. the effect of water and air curing along with the water absorption capacity of sawdust in powder form and the comparison of water uptake of self-compacting paste samples with and without sawdust at different days during wet curing showed that sawdust has the potential to serve as an internal curing agent in self-compacting cementitious system.

Influence of the fine aggregate particle packing effects on the paste rheological thresholds of self-compacting concrete

The paste rheological threshold theory could guide the prediction of the self-compacting concrete (SCC) performance from the paste mini-slump flow test. The prediction process was simplified, but the prediction did not consider the influence that the fine aggregate caused enough, possibly leading to a wrong mix design when the fine aggregate changed. To solve this issue, this study focused on the effect of the fine aggregate particle packing effects on the paste threshold. Based on the 3-parameter particle packing model, a fine aggregate packing parameter that can describe the fine aggregate particle packing effects more accurately was proposed to replace the original one, which considered only the particle size. Thus, the threshold calculation formulas were modified. To verify the modification, a total of five series of paste and SCC tests with different material compositions were conducted. Based on the bilinear interpolation method, the self-compacting paste zones (SCP zone) were obtained by original and modified thresholds. Through the comparison of SCP and SCC zones, the prediction accuracy of the proposed modification was evaluated by a certain evaluation method. The overlap area and relative position of the self-compacting zones were evaluated by the relative accuracy index Δε and the modification accuracy index Δ|ε’-1|, respectively. Through the modification of the paste thresholds, the overlap area of the modified SCP and SCC zones changed little. But the relative position of the modified SCP zone was closer to the SCC zone than the original SCP zone. The modified SCP zone showed more accuracy in prediction summarily. The proposed modification embodied the influence that the fine aggregate packing properties caused, expanding the description of fine aggregate particle packing effects in the paste threshold theory.

Mix-Design Optimization of Self-Compacting Paste Incorporating Powdery Industrial Solid Wastes Based on a Paste Rheological Threshold Theory

The effect of powdery industrial solid wastes on the optimal proportion of pastes and self-compacting concrete (SCC) is investigated in this study. There were nine groups of powdery industrial solid wastes designed, including cement, fly ash (FA), limestone powder (LP), granulated blast furnace slag (GBFS), and modified phosphogypsum (MPG). The powder materials have different properties, such as zeta potential, density, and specific surface area. The paste rheological threshold theory was used to calculate the self-compacting paste (SCP) zone and the optimal proportion. To assess the effect of powder properties on the optimal mix proportion, a model was proposed. The linear regression method was used to obtain quantitative relationships between the optimal proportion and powder characteristics, which can benefit in the SCC optimization process. A new powder combination was designed, and the optimal water-to-powder ratio by volume (VW/VP) and the dosage of superplasticizer by mass (SP%) can be calculated using the powder combination’s physical and chemical properties. The search area was narrowed, and the SCP zone was obtained, where a good SCC was achieved, validating the powder effect model’s effectiveness.

A new model to predict the optimal mix design of self-compacting concrete considering powder properties and superplasticizer type

This study investigated the effect of powder materials and superplasticizer type on the optimal proportion of pastes and self-compacting concrete (SCC). Nine groups of power materials containing cement, fly ash (FA), limestone powder (LP), granulated blast furnace slag (GBFS), and modified phosphogypsum (MPG) were designed. The powder materials differed in their characteristics including specific surface area, zeta potential and density. Self-compacting paste zone (SCP zone) and the optimal proportion were obtained based on the paste rheological threshold theory. Quantitative relationships between the optimal proportion and powder characteristics were obtained by the linear regression method, which can help in the optimizing process of SCC. A new powder combination was designed to validate the relationships. The optimal water‒powder ratio by volume (VW/VP) and the optimal superplasticizer dosage by mass (SP%) could be calculated considering the physical and chemical properties of the powder combination. According to the optimal mix, the search area was narrowed and the SCP zone was obtained where a good SCC was obtained, which validated the effectiveness of the powder effect model. Finally, an improved powder effect model applicable to different superplasticizer types was proposed based on a good linear relationship between the optimal VW/VP and the basic VW/VP.

Properties of self-compacting mortar made with various mineralogical sources different types of sands and fillers

Purpose By its high fluidity, great deformability and rheological stability, the self-compacting mortar (SCM) is capable of ensuring the ability to be easily implemented without vibration. However, its formulation requires a large volume of fine materials with a high dosage of cement, which is necessary to ensure adequate workability and mechanical strengths, which is necessary to allow its flow. Current environmental considerations encourage reducing the production of cement, it is essential to use additions to replace the cement, because of their great availability and their moderate price. On another side, their use contributes to an economic sort to solve the problems related to the environment. Design/methodology/approach The formulations and characteristics of SCM made with two types of mineralogical sources (silica and limestone) were investigated. Different materials were used separately and in binary combinations; silica river sand (SRS), limestone quarry sand (LQS), silica fillers (SF) and limestone fillers (LF). The formulation starts with the self-compacting pastes (SCPs) then the SCMs at the SRS and the LQS whose the cement is partially replaced by volume contents of SF and LF with 15%, 30% and 45%. Findings The results obtained prove that the incorporation of LQS instead of SRS has a negative effect on the fluidity and deformability and a positive effect on the mechanical strengths of SCM. In addition, the incorporation of the SF and LF reduces the need for water and the saturation dose of superplasticizer in the pastes. Thus, the addition of the SF and LF in specific voluminal contents (15% SF and 30% LF) in the binder can have a beneficial effect on the parameters of the workability and the mechanical strengths of SCM. These results are very interesting to aspects such as technological, economic and environmental. Originality/value Influence of the different type of sands and fillers in improvements the properties of SCM made from various mineralogical sources.

Utilization of Solid Waste from Brick Industry and Hydrated Lime in Self-Compacting Cement Pastes.

The huge amount of solid waste from the brick manufacturing industry can be used as a cement replacement. However, replacement exceeding 10% causes a reduction in strength due to the slowing of the pozzolanic reaction. Therefore, in this study, the pozzolanic potential of brick waste is enhanced using ultrafine brick powder with hydrated lime (HL). A total of six self-compacting paste mixes were studied. HL 2.5% by weight of binder was added in two formulations: 10% and 20% of waste burnt brick powder (WBBP), to activate the pozzolanic reaction. An increase in the water demand and setting time was observed by increasing the replacement percentage of WBBP. It was found that the mechanical properties of mixes containing 5% and 10% WBBP performed better than the control mix, while the mechanical properties of the mixes containing 20% WBBP were found to be almost equal to the control mix at 90 days. The addition of HL enhanced the early-age strength. Furthermore, WBBP formulations endorsed improvements in both durability and rheological properties, complemented by reduced early-age shrinkage. Overall, it was found that brick waste in ultrafine size has a very high degree of pozzolanic potential and can be effectively utilized as a supplementary cementitious material.

Effects of fly ash and limestone powder on the paste rheological thresholds of self-compacting concrete

Self-compacting concrete (SCC) containing composite powders has many advantages, such as its abilities to reduce the heat of hydration, optimise the particle packing, and maintain the workability better than pure cement SCC. The rheology of the paste is important for understanding the flow behaviors of SCC. This study investigates the effects of fly ash (FA) and limestone powder (LP) on the rheological thresholds of SCC pastes. By introducing a powder fitting coefficient, intrinsic viscosity, and volume fractions, the original rheological model is improved. Both models are used to predict the paste yield stress threshold and paste plastic viscosity threshold of fresh SCC. After calibrating the fitting coefficient and intrinsic viscosity of the FA and LP, the modified model can accurately predict the self-compacting paste (SCP) zone, where SCC can be obtained by mixing paste with sand and gravel. The absolute and relative accuracies of the modified model are far greater than those of the original model, except for the case of C + 30%FA, for which the modified model is superior to the original model in terms of the location of the SCP zone. SCC experiments with different coarse aggregate contents, sand properties, and powder compositions are conducted to verify the modified model, and indicate that the powder fitting coefficient and intrinsic viscosity remain constant.

Research on a mix design method of self-compacting concrete based on a paste rheological threshold theory and a powder equivalence model

This work studied a mix design method of self-compacting concrete (SCC) containing limestone powder (LP) or fly ash (FA) or both. The addition of LP or FA or both was shown to reduce the water/powder volumetric ratio (Vw/Vp) and the superplasticizer/powder mass ratio (SP%) and increase the SCC flowability. The reason for these phenomena is that powders such as LP and FA have ball bearing effect, filler effect and adsorption effect, which play a larger role in paste than in SCC owning to the relative percentage of LP or FA or both decreasing after adding aggregates. The different role limit the applicability of the paste rheological threshold theory, which results in the self-compacting paste (SCP) zone not accurately matching the SCC zone. A powder equivalence model was proposed to solve the influence of the above three effects on this zone mismatch. LP and FA can be converted to equivalent cement through equivalence coefficients based on the SCC flowability. The equivalence coefficients of LP by volume and by mass are 0.75 and 0.6, respectively. The equivalence coefficients of FA by volume and by mass are 0.50 and 0.38, respectively. Based on the equivalence coefficients from the experiments, LP and FA were mutually used in SCCs with the coefficients unchanged. The result shows that the equivalent SCP zone for the addition of LP and FA coincide partly with the SCC zone.

Properties enhancement of super absorbent polymer (SAP) incorporated self-compacting cement pastes modified by nano silica (NS) addition

In this exploratory study, the effects of nano silica (NS) on the properties of self-compacting pastes (SCPs) incorporated with superabsorbent polymer (SAP) have been investigated. NS was added to cement pastes, containing SAP, in varying amounts of 1%, 2% and 3%. SAP were found out to be successful in mitigating shrinkage in all formulations; however they were more effective in mixes without super-plasticizers (SPs). SAP particles reduced the fluidity, increased the air content and also reduced strength slightly due to the formation of macro-pores. NS was beneficial in improving the hydration attributes by increasing the mechanical strength and refining the microstructure. The denser microstructure of the NS modified pastes compensated for the macro pore formation associated with SAP incorporation, leading to strength increase. With NS, there was better bonding of the SAP particles in the matrix. The reduced Ca(OH)2 content in NS modified samples showed increased pozzolanic activity associated with NS in cement pastes.

Development of self-compacting mortars based on treated marine sediments

This paper deals with the prospect of recycling dredged sediments in self-compacting mortars (SCM) and their impact on the fresh and hardened properties of SCC pastes/mortars. The raw sediments were dried, sieved to 120 µm, and then thermally treated at 850 °C for one hour. Physical, chemical and mineralogical properties were determined for all materials. Fifteen mortars/paste mixes were prepared using the response surface methodology, based on the variation of three independent parameters: water-to-binder, sediments-to-cement, and volume-of-binder-to-total-volume ratios. The responses were the workability and fluidity of the self-compacting pastes, and the mechanical properties of the self-compacting mortars (compressive, bending strength, and dynamic modulus of elasticity). A numerical optimization was used to select the optimal mixture with the maximum amount of treated sediments, while maintaining self-compactibility properties.

Response of self-compacting paste (SCP) systems containing Acacia Modesta gum

This paper shows the response of self-compacting paste systems (SCPs) containing botanical Acacia Modesta (AM) gum, a natural organic ooze-out of an indigenous tree called Phulai, as an admixture. The gum being different in its nature and origin, exhibited different results from Acacia Nilotica gum powder when used in SCPs. AM gum powder was characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Nuclear Magnetic Resonance (NMR) and Fourier Transform Infrared Spectroscopy (FTIR). The self-compacting paste systems (SCPs) containing 0.25%, 0.5%, 0.75% and 1% AM gum powder were tested for super-plasticizer (SP) demand, flow, viscosity, air content (in fresh state), density, total linear early shrinkage, calorimetry and both short-term (28-day) and long-term (90-day) compressive strengths. SCPs with AM gum powder showed a considerable decrease in total shrinkage, a reduction in density values, an increase in fresh state viscosity. AM gum powder also had a retarding effect on setting times of the respective gum modified SCPs. Moreover, the electrical resistivity of samples containing AM increased tremendously indicating change in the microstructure of the gum modified SCP systems. It became clear that different types of Acacia gums when incorporated in SCPs gave different responses and should be used with complete understanding. Therefore, AM gum in cementitious systems offers many potential areas for application and further future research work. The AM gum powder may be used for reducing shrinkage in SCP systems, establishing internal curing inside the SCCS, for enhancing the viscosity of the cementitious systems and for producing slightly porous energy efficient cementitious systems.

Use of Effective Micro-organisms (EM) technology and self-compacting concrete (SCC) technology improved the response of cementitious systems

Effective Microorganism technology (EMT) is of Japanese origin and has found useful applications in agriculture and water treatment works. This study reports the response of self-compacting paste systems with the addition of a mixture containing three micro-organisms namely lactic acid bacteria, photosynthetic bacteria and yeast all present in a suitable liquid medium. Two types of Effective Microorganisms (EMs) consortia, EM-Light (EML) having light brown color and low microbial cell concentration and EM-Dark (EMD) having dark brown color with high microbial cell concentration in a suitable liquid were used to study a total of seven self-compacting paste (SCP) formulations. These seven formulations include a control formulation and six EM modified SCP formulations containing 5, 10 and 15% (by wright content of cement) of both EM liquid consortia. The results showed that both EM consortia modified the plastic viscosity, delayed setting times and hydration kinetics, modified volume stability, reduced water absorption of SCP systems in hardened state and enhanced the compressive strength of SCP systems. Especially strength of SCPs with EMD seem to depend on fresh density of the paste to a large extent while with EML it shows different response. An increase of 26% in strength was observed compared to the control formulation with 15% EMD amendment at similar water-cement ratio along with a reduction in water absorption of hardened SCPs which may be attributed to the refinement in microstructure obtained by the production of calcium carbonate predominantly as a result of the reaction between microorganisms and calcium hydroxide. Scanning electron microscopy (SEM) and XRD results also suggest improvements in strengths of SCPs due to calcite (calcium carbonate).

Effect of fine aggregate characteristics on the thresholds of self-compacting paste rheological properties

This work studies the effect of fine aggregate characteristics on the thresholds of self-compacting paste rheological properties. Fine aggregate characteristics consist of gradation and content. The specific surface area (SSA) was used to quantitatively describe the gradation of fine aggregate. The most lenient criteria for qualified mortar were formulated from the view of yield stress and plastic viscosity. Mortar experiments were conducted by separately changing the SSA and sand ratio. For each combination, a series of mortar and corresponding paste experiments were performed by adjusting the water-cement ratio and the superplasticizer dosage to obtain paste rheological thresholds. Experimental verification tests on self-compacting concrete (SCC) was conducted. This method can be easily implemented with wide scope of sand gradation and content. Using this method, the aim of predicting the SCC workability from the rheological characteristics of paste was achieved.

Effect of Mixing Time on Flowability and Slump Retention of Self-Compacting Paste System Incorporating Various Secondary Raw Materials

Good workability at construction site is most important aspect of self-compacting concrete. But long delivery times can cause slump loss, which is more pronounced when mineral additives are incorporated into the concrete system. The aim of this paper is to study the effects of prolonged mixing on the flowability and slump retention under action of a high-performance polycarboxylic (PEC)-based superplasticizer used in self-compacting paste systems (SCPs) incorporating various secondary raw materials (SRMs). Experimentation for this research paper was focused on mixing times and slump retention of SCPs incorporating ASTM Class F fly ash (FA), silica fume (SF) and locally available marble powder (MP). While experimenting with SCPs, total mixing time was first restricted to 3 min of mixing to achieve the target flow of 30±1 cm, which was then prolonged to total mixing time of 10 and 20 min keeping the superplasticizer content constant, which showed a more enhanced flow with reduced timing due to better activation of superplasticizer, or enhanced workability but showed some traces of bleeding in the formulations containing MP. The samples were thereafter prepared for strength measurement as per EN-196. Parameters like flow response, strength and microstructures were studied by varying two basic factors in progression: shear time and hold time. Hydration kinetics were also affected by prolonged mixing, and it also decreased the initial and final setting time. FA showed better rheological behaviour upon extended mixing regimes as compared to SF or any other SRMs.

Self-Compacting Concrete Formulation by Measuring Excess Paste Volume

Concrete is composed of a liquid phase (paste) and of a solid phase (aggregates with fixed gravel/sand ratio), the concrete self-compacting properties come necessarily from those of the paste. The present research is the continuity of a first phase of the testing already conducted, which resulted in obtaining an optimal self-compacting cement paste composition. This paste will be used to prepare a self-compacting concrete (SCC), while passing from the scale of the cement paste to that of the concrete, by injecting wet aggregate to the self-compacting paste. The excess paste theory was used to determine the thickness of the paste coating each aggregate with a given diameter of constituting granular skeleton, then generalized for the determination of the quantity of total paste allowing the flow of the concrete by decreasing frictions between the grains of its granular skeleton. This approach was also experimentally validated. The influence of the granular distribution was minimized by the use of the approach based on the determination of the average diameter of the aggregates. This required the determination of a homothetic factor “K” similar for all concretes with different aggregate grading. Formulation of a self-compacting concrete passes initially by the determination of a sufficient quantity of paste allowing its flow without frictions between its aggregates and to balance the mixture by the quantity of water retained by the aggregates. The self-compacting concrete characteristics would come from those of the cement paste which composes it.

Set Time Measurements of Self-Compacting Pastes and Concretes Using Ultrasonic Wave Reflection

The ultrasonic shear-wave reflection coefficient at the interface between a hydrating material and a buffer material was monitored immediately after mixing as a function of time to study setting behavior of self-compacting pastes and concretes. High-impact polystyrene was used as the buffer material because it is very sensitive to early changes. Self-compacting pastes were produced using fly ash and superplasticizer. Initial and final set times were measured and compared with those obtained from the standard penetration resistance test. Both methods showed reproducible results with self-compacting pastes and were able to distinguish fairly small changes in composition. A good correlation was found between set times obtained from the two methods. The self-compacting pastes were seen to have a substantially delayed set as compared with plain pastes. In addition, self-compacting concretes were made and their set times were measured using ultrasonic wave reflection. The method was seen to be quite reproducible for concrete, and concrete set times matched those of the corresponding pastes reasonably well.

Excess paste method to formulate a self-compacting concrete

On the basis of the principle that a concrete is composed of a liquid phase (paste) and a solid phase (aggregates with fixed gravel/sand ratio), the concrete self-compacting properties come necessarily from those of the paste. The present work is the continuity of a first phase of the testing already conducted, which resulted in obtaining an optimal self-compacting cement paste composition. This paste will be used to prepare a self-compacting concrete (SCC), while passing from the scale of the cement paste to that of the concrete, by injecting wet aggregate to the self-compacting paste. The excess paste theory was used to determine the thickness of the paste coating each aggregate with a given diameter of constituting granular skeleton, then generalized for the determination of the quantity of total paste allowing the flow of the concrete by decreasing frictions between the grains of its granular skeleton. This approach was also experimentally validated. The influence of the granular distribution was minimized by the use of the approach based on the determination of the average diameter of the aggregates. This required the determination of a homothetic factor “k” similar for all concretes with different aggregate grading. Formulation of a self-compacting concrete passes initially by the determination of a sufficient quantity of paste allowing its flow without frictions between its aggregates and to balance the mixture by the quantity of water retained by the aggregates. The self-compacting concrete characteristics would come from those of the cement paste which composes it.

Excess paste method to formulate a self-compacting concrete

On the basis of the principle that a concrete is composed of a liquid phase (paste) and a solid phase (aggregates with fixed gravel/sand ratio), the concrete self-compacting properties come necessarily from those of the paste. The present work is the continuity of a first phase of the testing already conducted, which resulted in obtaining an optimal self-compacting cement paste composition. This paste will be used to prepare a self-compacting concrete (SCC), while passing from the scale of the cement paste to that of the concrete, by injecting wet aggregate to the self-compacting paste. The excess paste theory was used to determine the thickness of the paste coating each aggregate with a given diameter of constituting granular skeleton, then generalized for the determination of the quantity of total paste allowing the flow of the concrete by decreasing frictions between the grains of its granular skeleton. This approach was also experimentally validated. The influence of the granular distribution was minimized by the use of the approach based on the determination of the average diameter of the aggregates. This required the determination of a homothetic factor “k” similar for all concretes with different aggregate grading. Formulation of a self-compacting concrete passes initially by the determination of a sufficient quantity of paste allowing its flow without frictions between its aggregates and to balance the mixture by the quantity of water retained by the aggregates. The self-compacting concrete characteristics would come from those of the cement paste which composes it.

Experimental Investigation on Use of Wheat Straw Ash and Bentonite in Self-Compacting Cementitious System

In this research, we evaluated the feasibility of wheat straw ash and bentonite (raw and heated at 150°C for 8 hrs) as secondary raw materials in self-compacting paste (SCP). The fresh and hardened properties of SCP formulations including water and superplasticizer demand, flow behavior, compressive and flexural strength development, water absorption, and acid attack resistance were evaluated. Moreover, porosity, microstructural, and mineralogical investigations were also carried out on SCP formulations. Test results showed that the properties of SCP formulations in fresh state depend on the morphology of secondary raw materials. For heated bentonite and wheat straw ash formulations, the 28 days of compressive and flexural strength were higher or almost similar to reference SCP formulation. Among SCP formulations, wheat straw ash formulation was found to be more effective in consuming free lime and showed significant decrease in porosity with time, which in turn improved the resistance of this SCP formulation against water absorption and acid attack. Based on the test results, it can be concluded that the successful utilization of wheat straw ash and bentonite SCP formulations will offer durable and environmental friendly option to construction industry.