High-range Water-reducing Admixture Research Articles

Impact of sodium hydroxide molarity on mechanical properties of fly ash–slag-based geopolymer concrete

The requirement of heat curing besides the poor workability of geopolymer concrete (GPC) is the main hurdle in its practical implementation. This study investigates the impact of sodium hydroxide (NaOH) concentration on the behaviour of fly ash slag blended ambient-cured GPC. The sodium hydroxide concentration was varied within the range from 8 molar to 14 molar to investigate its impact on fresh and hardened mechanical properties. The increase in sodium hydroxide concentration from 8 molar to 16 molar resulted in a continuous decrease in the workability of GPC. The target slump of more than 150 mm was achieved even for high sodium hydroxide concentration due to the presence of high-range water-reducing admixture. However, the increase in sodium hydroxide concentration positively influences the strength development of fly ash–slag-based ambient-cured GPC. The optimum 28 days compressive strength and splitting tensile strength of 44.3 MPa and 4.01 MPa, respectively, were achieved for the GPC with a sodium hydroxide concentration of 12 molar. The comparison of life-cycle assessment indicated that GPC is a sustainable alternative that offers a 49% reduction in greenhouse gas emissions compared to ordinary Portland cement-based concrete.

The Mechanical Characteristics of Enhanced Bendable Concrete By Polyvinyl Alcohol Fibers

Abstract Engineered Cementitious Composites (ECC), which are alternatively referred to as Bendable Concrete, is a class of Ultra-ductile cementitious composites characterized by their remarkable ductility and polyvinyl alcohol fiber (PVA) fiber reinforcing. These composites are designed to regulate cracks width effectively. This study investigates the influence of matrix flowability, fiber mixing technique, and curing conditions on the mechanical characteristics of Bendable Concrete utilizing high-tenacity (PVA) fibers. This study examined the compressive strength of Bendable concrete, which ranged from 60 to 70 MPa, with a strain exceeding 3%. To regulate the flowability of the matrix, high range water reducing admixture (HRWRA) was added to a matrix with a weight ratio of silica fume was 10% by weight of cement, a weight ratio of water to cementitious material of 0.3, also polyvinyl alcohol acetate solution (PVAS). The primary parameter under investigation in this study is the changing volume fraction dose of (PVA) fiber, while the remaining materials of the combination were held constant. Four different (PVA) fiber percentages (0.5, 1.0, 1.5, and 2.0)% were adopted by volume of cement. Three (cubes, cylinders, and prisms) were fabricated and cast from each mixture and tested at the ages (7, 28, and 90) days for investigated (compressive, splitting tensile, and Modulus of Rupture) strength, respectively. The results of the tests demonstrated that the proportion of fiber substantially affects the strengths, where both the Compressive strength and Splitting tensile strength were increased with the increment of fiber content until 1% of (PVA) fiber . In comparison, the higher Modulus of Rupture was abtained at 2% (PVA) fiber.

Influence of Admixture Source on Fresh Properties of Self-Consolidating Concrete.

The study presented herein was intended to (1) compare the optimum (minimum) dosage requirements of four different sources of polycarboxylate-based high-range water-reducing admixtures (HRWRAs) and viscosity-modifying admixtures (VMAs) in attaining slump flows of 508 mm, 635 mm, and 711 mm, and a visual stability index (VSI) of 0 (highly stable concrete) or 1 (stable concrete), and (2) assess the flowability/viscosity, stability, passing ability, and filling ability of the resulting self-consolidating concretes. The test results showed that the optimum dosage requirements to obtain a uniform slump flow and visual stability index varied among the four selected admixture sources. The required dosage amount for HRWRAs was highest for the polycarboxylate-ester (PCE) type and lowest for the polycarboxylate-acid (PCA) type. Acceptable flowability plastic viscosity dynamic and static stability, passing ability, and filling ability of self-consolidating concrete can be achieved with the proper dosing of the four studied admixture sources.

Compressive and flexural strength of cement mortar blended with cassava peel ash and high-range water-reducing (superplasticizing) admixtures

This paper presents the outcome of an experiment carried out by using cassava peel ash (CPA) of varying quantities to partially replace cement in mortar mix and the influence of adding superplasticizer in the mortar mix is further investigated. The experiment was carried out by partially replacing CPA in the range of 0 to 25 percent by weight of cement at 5% intervals. A water binder ratio (w/b) of 0.5 and superplasticizer dosage of 1.5l/100kg were used to produce the blended mortar of mix 1:3. The samples were cured and tested for compression and flexure at 7, 28, and 90 days after demolding. The results of the first experiment confirmed the suitability of the cassava peel ash (CPA) at not more than 15% replacement with cement for mortar and concrete works. In the second experiment, the superplasticizer has a linear relationship with the conventional mortar while the blended cement-cassava peel ash (CCPA) mortar retarded in strength at an early stage. However, 5% CPA mortar with superplasticizer gained 52 percent strength from 7 days to 28 days of the test. In addition, at the 90-day test, 5% CPA mortar with superplasticizer has almost an equivalent strength (96%) of the conventional mortar with superplasticizer. The flexural strength for blended CCPA mortar of 5-15% showed an acceptable value with that of mortar with a superplasticizer. Generally, the addition of admixture to the blended CCPA mortar showed a different trend compared to the conventional mortar.

Interaction of Polycarboxylate-Based Water-Reducing Admixture Molecular Structure with Fly Ash Substituted Cementitious Systems: Marsh-Funnel and Mini-Slump Performance

Polycarboxylate ether-based high-range water-reducing admixtures (PCE) play a crucial role in enhancing the workability of fly ash-substituted cementitious systems. Alterations to the chemical structures of both the main and side chains can particularly enhance the electrostatic repulsion and steric hindrance effects of PCEs. As a consequence, this results in improved performance within cementitious systems containing fly ash substitutions. This study investigated the compatibility of the altered molecular structure of polycarboxylate ether (PCE) with cementitious systems containing fly ash substitutions. To achieve this, five polymers were synthesized, varying the side chain length, molecular weight, main chain length, and main chain lengths of PCEs while maintaining other properties constant. Cement pastes were then prepared using the synthesized PCEs with fly ash replacements at three different rates. Marsh-funnel flow time and mini-slump values were measured in the prepared mixtures. The study revealed that in mixtures without fly ash, PCEs with a long main chain (40k) and short side chain length (1000 g/mole) exhibited the lowest Marsh-funnel flow and mini-slump performance among PCEs with diverse molecular structures. For the other PCEs in these mixtures, the change in molecular structure did not significantly affect their performance. However, as the fly ash replacement rate increased, PCE having a medium main chain (21k) and side chain (2400 g/mole) length outperformed other PCEs in terms of Marsh-funnel flow and mini-slump performance.

Durability Study of Self Compacting Concrete Containing Fly Ash, Lime Stone and Sugarcane Bagasse

Abstract: Self-compacting concrete (SCC) is a unique kind of concrete that can flow and fill form work or moulds under its weight without the aid of vibration or mechanical compaction. SCC is accomplished using a specifically formulated mix that contains high-range water-reducing admixtures (super-plasticizers) and viscosity-modifying agents. Excellent workability, great flowability, and the capacity to pass through densely packed reinforcement without segregation are just a few of SCC's special qualities. SCC has many advantages, including increased construction efficiency, lower labor costs, improved durability, and better surface polish. The present study focuses on the durability properties of concrete mixes, which were designed using control, binary, and ternary cementitious systems. In the environment, wastes such as Fly Ash (FA), limestone (LS), and agroindustrial waste such as sugarcane bagasse ash (SCBA) are used as partial replacements for cement.

Extrusion and structural build-up of 3D printing cement pastes with fly ash, nanoclays and VMAs

3D printing technology (3DP) has provided new design and structural opportunities for cement-based systems (CBS) in architectural construction. However, there are still some issues related to extrudability and buildability of CBS, which can be overcome by using components for CBS rheology control. In this study, three types of nanoclays, a bentonite (BEN), a sepiolite (SEP) and an attapulgite (ATT), and two viscosity modifying admixtures (VMAs), a poly-acrylamide (VMA1) and a methylcellulose ether (VMA2), were added to a reference cement-fly ash 3D printing paste to evaluate their impact on CBS rheological properties and their implications in extrusion and buildability for 3DP. A polycarboxylate-ether based high range water-reducing admixture (HRWRA) was used to reach a target stiff consistency. Four laboratory tests were used to assess paste rheology, extrusion and structural build-up. Proper and deficient material extrusion limits were defined considering cohesion and initial yield stress. It was found that the combination of VMA2 and SEP increased cohesion, enhancing extrusion and avoiding water drainage and frictional behavior of pastes, producing properly extrudable paste. SEP by itself also improved structural build-up. Besides, samples with NC and VMAs required larger amounts of HRWRA, delaying cement setting and compressive strength gain.

施工者を対象とした高強度コンクリートの施工性向上に関するアンケート調査

High-strength concrete has been put into practical use by technological development of air-entraining and high-range water-reducing admixture and low-heat type cement, and has become widespread mainly in high-rise RC buildings. However, high-strength concrete with a low water-cement ratio and a large amount of cement has a high viscosity, so construction problems such as pumpability and finishability have emerged with its widespread use. Therefore, we conducted a questionnaire survey on the specific details of defects and how to improve them by modifying the mix-proportions, for construction problems such as transportation of high-strength concrete, placing and compaction, and finishing.

Data science approach to find an outlier in the group of cement dispersants

Polycarboxylate ether (PCE) is an essential cement dispersant to be included in high-range water-reducing admixtures for concrete. The polymeric structure of PCE is easily modified to satisfy its performance requirement for a specific concrete produced in sites. A PCE developer polymerizes hundreds of PCE samples to find the final product to be applied and evaluating the performance of each sample is cumbersome considering the variability of concrete-constituting materials. A data-driven algorithm is proposed to probe a PCE showing superior performance. Principal component analysis is adopted to regulate the change in the viscosity curves of mortar samples incorporating the reference PCE. An outlier PCE is then found showing the highest dissimilarity, defined by the eigen-decomposition error and the changing pattern of the viscosity curves, compared to the reference PCE. As a result, the outlier PCE had the unique distinction of providing low viscosity for concrete.

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.

Investigation of High Range Water-Reducing Admixture Requirement in Cementitious Systems Containing Fly Ash with Different Utilization Ratio and Fineness

Investigation of High Range Water-Reducing Admixture Requirement in Cementitious Systems Containing Fly Ash with Different Utilization Ratio and Fineness

Homogeneous flow performance of steel-fiber reinforced self-consolidating concrete for repair application: A biphasic approach

In this study, fiber-reinforced self-consolidating concrete (FR-SCC) was considered as a diphasic suspension of fiber and coarse aggregate (F-A ≥ 5 mm) skeleton in mortar suspension with solid particles finer than 5 mm. The coupled effect of the volumetric content of fibers, coarse aggregate particle-size distribution, and rheological properties of the mortar on the passing ability and dynamic stability of various FR-SCC mixtures was investigated. Nine high-strength and 10 conventional-strength FR-SCC mixtures for repair application were proportioned with water-to-binder ratios (W/B) of 0.35 and 0.42, respectively, and macro steel fibers of 0.1%–0.5% volumetric contents. The dosages of high-range water-reducer (HRWR) admixture were optimized to achieve a targeted slump flow of 680 ± 20 mm. The yield stress and plastic viscosity of the mortar mixtures varied between 4.6-17.7 Pa and 2.8–8.2 Pa s, respectively. Flow performance of the investigated mixtures were evaluated in terms of flowability (slump-flow test), passing ability (J-Ring and L-Box set-ups), and dynamic stability (T-Box test). According to the established correlations, the main influencing parameters on homogeneous performance of FR-SCC include W/B, paste volume, volumetric content-to-packing density of F-A (φ/φmax), HRWR dosage, fiber content, mortar rheology, and volume of excess mortar. The robustness analyses results revealed that homogeneous flow performance of FR-SCC is more sensitive due to variations of the φ/φmax and paste volume rather than mortar rheology, W/B, and HRWR dosage. The characteristics of the mixture constituents for FR-SCC mixtures with different strength levels were finally recommended to ensure acceptable homogeneous performance under restricted flow conditions of repair application.

Reconnoitring principles and practice of Modified Andreasen and Andersen particle packing theory to augment Engineered cementitious composite

• Engineered Cementitious Material ECC, unique composite with high resistant to crack. • Modified Andreasen and Andersen theory is employed to optimize mix proportion of ECC. • Particle packing model in accessible software (EMMA) decrease incidence of trial mixes required. • Optimization of particle packing with distribution modulus of 0.23 refines pore distribution. • From 26 trial mixes, optimal dosage of HRWRA is 2.62 percent with water binder content of 0.16. • Incorporation of 15 % silica fume, 0.16 water binder ratio enhances compressive strength to 82 MPa. Engineered Cementitious Composites (ECC) is a heterogeneous high-performance material with improved compressive strength and fatigue resistance. The nature and intensity of packing has a significant impact on the efficiency of ECC. To streamline the mix design by an improved technique the current study focuses on employing the Modified Andreasen and Andersen (MAA) theory to optimize the mixture proportions of ECC with the particle packing concept that in turn reduces lot of trial mixes. The primary input parameters are particle size distribution, density of materials, binder proportions and water content. In this case study, about series of 6 group of trail mixes with water binder ratio ranging from 0.14 to 0.24 are chosen, and the optimization is carried out using Elkem Materials Mixture Analyser (EMMA). Hence the MAA deals with the solid particle packing effect, the ratio of water and High Range Water Reducing Admixture (HRWRA) depends on the flowability test of ECC. According to the results, the optimal dosage of HRWRA is 2.62 percent with a water binder content of 0.16. It is ascertained from the case study that, A 09 mix recipe exhibits improved compressive strength of up to 82 MPa at 28 days. Some of the mix recipes exhibit higher early strength, but the strength decreases with age in some compositions of ECC. The discontinuity of hydration process due to the presence of excessive early age additives such as silica fume, lack of adaptivity between the cement and superplasticizer, inappropriate combination of mixture proportion reduces strength of ECC.

Effects of Curing Temperature and Chemical Admixture Type on Fresh Properties and Compressive Strength of Ultra High-performance Concrete

The types of post-setting curing and high range water reducing (HRWR) admixture used in Ultra-High-Performance Concrete (UHPC) mixtures play significant roles in determining their rheological and mechanical properties. This study compares the performance of three types of HRWR admixtures commercially available when added to UHPC mixtures under three different curing regimes. Mixtures made with the different superplasticizers were evaluated for their flow, 45mins flow retention, and setting time as fresh mix properties. Compressive strength was also tested for each mixture after 3, 7, and 28 days of curing at the investigated various curing regimes. Sika Viscocrete 180GS produced the highest mixture flow and flow retention levels with a 241 mm flow and 93.7% flow retention. Sika Viscocrete 168-1 produced the best results of setting time with 3 hours as compared to 12 hours with Sika Viscocrete 180GS. Using Hyperplast PC-202, the required 150 MPa compressive strength was secured as early as 3 days of curing with a 48hrs-90ºC curing regime. Using the same HRWR admixture, compressive strength values slightly lower than 150 MPa were reached after 7-28 days when the 72hrs-60ºC regime was adopted. The last curing regime was recommended for producing architectural UHPC units to minimize the delayed formation of ettringite.

Effect of Water-Reducing Admixtures Having Hybrid Silicon Air-Entraining Surfactants on Some Properties of Concrete Mixtures

In order to improve the fresh properties and freeze-thaw resistance of cementitious systems, water-reducing and air-entraining admixtures are actively used in concrete mixtures. Generally, these mentioned admixtures are added to concrete mixtures as two separate admixtures. In this case, when the properties/compositions of one of the admixtures change, compatibility problems of admixtures may occur with each other or with the cement, and the fresh/hardened properties of the concrete may be adversely affected. In this study, a modified water-reducing admixture with both fluidity and air-entraining properties was produced. The utilization effect of high-range water-reducing admixtures (HRWR) having different ethylene oxide/propylene oxide (EO/PO)–based air-entraining surfactants (AES) on some properties of concrete mixtures was investigated. For this purpose, firstly, hybrid silicone AESs with a silicon content of 20%, 33%, and 38.5% were supplied. Then, HRWRs containing seven different AES were produced by using substitution and synthesis methods. In HRWRs produced by the substitution method, 3 and 5 wt. % of HRWR were substituted with EO/PO-based hybrid silicon AES. In the other method, EO/PO-based hybrid silicon air-entraining macromonomers were bonded to the HRWR at ratios of 1, 3, and 5 wt. % during its synthesis process. Replacing HRWR with hybrid silicone AESs increased admixture demand to provide the target slump value in concrete mixtures. Utilization of AESs containing 20% and 33% silicon in HRWR by the substitution method positively affected the permeability and compressive strength of concrete mixtures, while the rise of this ratio to 38.5% by using the synthesis method did not affect them significantly. The presence of surfactant with 20% silicon in 3% and 5% of the admixture and with 33% silicon in 5% of the admixture positively affected frost resistance of concrete mixtures. However, the use of surfactants with 33% silicon content in 3% of the admixture and 38.5% silicon in 1%, 3%, and 5% of the admixture showed a negative effect on the frost resistance of the mixtures.

Evaluation of mix design strategies to optimize flow and strength of mortar internally cured with superabsorbent polymers

A straightforward mix design method was developed for proportioning mortars containing superabsorbent polymers (SAPs). When modified by introduction of a typical amount of SAP (i.e., 0.2% by weight of cement), the 0.42 w/c ordinary Portland cement (OPC) mortars required addition of extra water and/or high-range water reducing admixture (HRWRA) to achieve a minimum target percent flow in mortar flow table tests. At high w/c (≥0.49), SAP accelerated compressive and flexural strength development. In all mortars tested, the addition of SAP either preserved or increased compressive and flexural strength values relative to SAP-free mortar with the same w/c.

Multi-effect of superplasticisers main and side-chain length on cementitious systems with fly ash

In this study, the effect of main and side chain lengths of polycarboxylate ether-based high-range water-reducing admixtures (WRAs) on the fresh properties, compressive strength and water absorption of cementitious systems containing 0, 15, 30 and 45 wt% fly ash was investigated. For this purpose, three WRAs with the same molecular weight but different chain lengths were produced. According to the test results, the flowability of the paste and mortars was negatively affected when the length of the main and side chains of the admixture was longer or shorter than a certain value. This adverse effect is thought to arise from weakening of the adsorption of the admixture with an increase in its chain lengths. However, when the main and side chain lengths of the admixture were shorter or longer than a certain value, the time-dependent flow properties of the mortar mixtures improved. The main and side chain lengths of the WRAs did not have a significant effect on the compressive strength and water absorption capacity of the mortar mixtures. However, irrespective of the admixture characteristics, with an increase in fly ash substitution, the flow and time-dependent flow properties of the mixtures were negatively affected but their water absorption decreased.

Effect of High-Range Water-Reducing Admixture Chain Lengths on Self-Consolidating Concrete

Effect of High-Range Water-Reducing Admixture Chain Lengths on Self-Consolidating Concrete

Effect of High-Range Water-Reducing Admixtures on Alkali-Activated Slag Concrete

Effect of High-Range Water-Reducing Admixtures on Alkali-Activated Slag Concrete

Short- and long-term properties of lime mortars with water-reducers and a viscosity-modifier

This paper intends to evaluate the short- and long-term effects of high-range water-reducing (PCE and PNS) and viscosity-modifying (potato starch) admixtures when used alone or together in the formulation of lime mortars. Results showed that PCE and PNS led to a moderate decrease in porosity, a slower and lower water intake and a significant improvement in mechanical strength, both in the short- and long-term. However, they were also responsible for a delayed carbonation and an increased stiffness, and PNS, in particular, for a slower drying and lower water vapour permeability. Still, most changes were below those induced by the use of cement in blended lime mortars. In turn, potato starch led to an increase in porosity and pore size, to a faster carbonation and was not detrimental to mechanical strength. It presented a dominant effect when used together with PCE due to the higher dosage added. Nevertheless, the combined use of these two admixtures proved to minimize some of the disadvantages associated with their individual utilization in lime mortars.