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In this study, the fresh state and hydration properties of 0–60% lithium slag blended cement pastes were investigated at water-binder ratio of 0.47. The workability of the fresh pastes was evaluated by measuring the air content, marsh cone flow, mini-slump flow, setting times, and through rheology tests. A 40% lithium slag cement could produce 91% strength activity index at 28 days; mini-slump pat diameter of 70.54 mm; marsh cone flow efflux time of 145 s; air content 0.6%; hydration heat of 300 J/g (at 72 h). At replacement levels above 40%, the strength activity index, air content, mini-slump flow, hydration heat, and fluidity were significantly reduced. Experimental investigations confirm that the mini-slump test provides the best correlation coefficients (R2 = 0.96) with the maximum shear viscosity of lithium slag cement pastes than the marsh cone flow efflux time and air content. The classical slump and rheological models were used to characterise the mini-slump, yield stress, and plastic viscosity of low to high volume lithium slag cement pastes. The present study recommends that a 40% lithium slag cement paste is a viable option to produce green concrete for optimum fresh, hydration, rheological, and hardened properties. [ABSTRACT FROM AUTHOR]

High-strength-performing concretes (HSPC) have been used extensively due to new building requirements and their special properties suitable for modern cities. Superplasticizers (SPs) are essential components in the mix design of these concretes since they control their fresh properties and improve durability. In practice, superplasticizers are used to achieve a desired workability without increasing the water content by dispersing agglomerated cement particles. The aim of this research was to investigate the effectiveness of a blended polycarboxylate (PCE) superplasticizer on the rheological behavior for three different cements. It was found that two SP agents with the same molecular structure but with different weight and side-chain length provided an SP product that had a greater effect on the rheological properties of the cement paste. Yield stress values remained unaffected in the presence of blended SP with an SP fraction above 50% and with long side chains while its adsorption ability increased with the decrease in SP fraction with shorter side chains and lower molecular mass. [ABSTRACT FROM AUTHOR]

High-strength-performing concretes (HSPC) have been used extensively due to new building requirements and their special properties suitable for modern cities. Superplasticizers (SPs) are essential components in the mix design of these concretes since they control their fresh properties and improve durability. In practice, superplasticizers are used to achieve a desired workability without increasing the water content by dispersing agglomerated cement particles. The aim of this research was to investigate the effectiveness of a blended polycarboxylate (PCE) superplasticizer on the rheological behavior for three different cements. It was found that two SP agents with the same molecular structure but with different weight and side-chain length provided an SP product that had a greater effect on the rheological properties of the cement paste. Yield stress values remained unaffected in the presence of blended SP with an SP fraction above 50% and with long side chains while its adsorption ability increased with the decrease in SP fraction with shorter side chains and lower molecular mass.

The production of ordinary portland cement (OPC) contributes enormously to global anthropogenic CO2 emissions and alkaliactivated binders are one of the potential alternatives to OPC. To use these materials as a replacement of OPC-based binders, they need to be engineered to overcome the drawbacks, one of which is the rapid setting that leads to the reduced workable time. In this study, an attempt has been made to investigate the dependence of rheological parameters--namely, yield stress, apparent viscosity, and spread diameter (mini-slump) of alkali-activated slag and fly ash binders--on the oxide composition of the precursor, solid content, molar modulus, and activator dosage. It has been observed that the calcium oxide content plays a major role in the evolution of rheological parameters. Results showed that the yield stress and apparent viscosity were also influenced by molar modulus, activator dosage, and solid content. [ABSTRACT FROM AUTHOR]

• Water/Binder affected significantly the fluidity, permeability and compressibility. • SP affected primarily the fluidity, the rheology, permeability and compressibility. • VMA influenced the fluidity, rheology, permeability and compressibility. • Limestone filler affected only the min-slump and rheology. • Optimisation of stable grout can be determined by using desirability function. This paper reports the effect of mix composition of grout on the fluidity, rheological behaviour and hydro-mechanical behaviour (permeability and compressibility). Factorial design was used in this investigation to assess the combined effects of the four mix composition parameters on fluidity, rheological properties, permeability and compressibility: water/binder ratio (W/B), percentage of limestone filler as replacement of cement (LF), dosage of viscosity modifying admixture (VMA), and dosage of superplasticiser (SP). To evaluate both the rheology of the cement grout and its hydro-mechanical behaviour, mini-slump test, Lombardi plate test, and forced bleeding test, coaxial rotating cylinder viscometer were used. A two-level fractional factorial model was used to model the effect of key variables on the fluidity, the cohesion, permeability and compressibility. The predicted models are valid for mixtures made with W/B ranged from 0.35 to 0.42, LF from 12% to 45% as replacement of cement, VMA (percentage of binder) from 0.02 to 0.7%, and SP from 0.3 to 1.2%. The effects of W/B, LF, VMA and SP were analysed using polynomial regression which can identify the primary factors and their interactions on the measured properties. Prediction models were developed for mini-slump, plate cohesion meter, permeability and compressibility as function of W/B, LF, VMA, and SP. The factorial statistical approach used highlighted the effect of W/B, the dosages of SP and VMA on the various rheological properties, permeability and compressibility. [ABSTRACT FROM AUTHOR]

In this paper, the concept of paste film-forming ability is introduced as a parameter for mixture proportioning of pervious concrete. Two new test methods are also developed. The two methods characterize film-forming ability in two conditions. The first method characterizes the ability of a cement paste to form a stable film on a smooth nonabsorbent vertical surface. The paste thickness measured from this test is called, Ideal Paste T hickness (IPT). The second test characterizes the ability of cement paste to adhere and remain on an aggregate surface; this paste thickness is called A ctual P aste T hickness ( APT ). The IPT can be used as a standardized parameter to evaluate the film-forming ability of cement pastes. The APT can be used to study the formation of cement paste films on pervious concrete aggregates. In this study IPT and APT of sixteen superplasticized cement pastes were evaluated. The pastes were prepared from four water to cement ( w / c ) ratios (0.23, 0.27, 0.32 and 0.37). [ABSTRACT FROM AUTHOR]

Self-Compacting Mortars (SCM) can be regarded as high flowing mortars, which must show both a good fluidity (to fill complex formwork shapes) and sufficient viscosity (to avoid segregation). The characterization and control of fresh properties are proving to be critical for the success of SCM design. Usually, this task is performed through technological tests such as v-funnel and minislump. However, the use of viscometers can successfully perform better access of fresh properties. The objective of the present work is to correlate experimental results of v-funnel and mini-slump tests with viscosity of SCM, measured at different rotational speeds, and with constants a and b calculated from the power-law viscosity model. Linear relationships between both v-funnel and minislump tests and viscosity were demonstrated. Statistical models are also established to highlight the influence of constants a and b on the v-funnel and mini-slump variations. Results indicate the usefulness of established models to better understand the trade-off between constants a and b on fresh properties measured by v-funnel and mini-slump tests. [ABSTRACT FROM AUTHOR]

• A novel backfill material with good thermal performance was proposed. • The possibility of horizontal backfill-coupled heat exchanger was evaluated. • The mechanical and thermal properties of the backfill materials were tested. • The influencing factors of BCHE system were explored through experiments. • The thermal performance of NFG-BCHE was significantly improved. The continuous exploitation of mineral resources into the deep strata provides suitable conditions for the development of geothermal energy. Backfill technology can not only ensure the safety of mining operation and realize the recovery and utilization of solid waste, but also serve as artificial thermal reservoir. However, ordinary backfill materials have poor thermal properties and limit the geothermal energy extraction. In this paper, a novel backfill material with good thermal performance was proposed and tested to replace the traditional materials. The feasibility of horizontal backfill coupled heat exchanger system was evaluated by experimental method for the purpose of efficient cooperative development of mineral resources and geothermal resources. Natural flake graphite and other solid waste materials, such as copper slag, steel slag, aluminum slag and coal gasification slag were used to replace tailings of 2.5%, 5%, 7.5% and 10% by mass fraction to make the composite backfill material. The uniaxial compressive strength, mini-slump, thermal conductivity, specific heat capacity and density of the composite backfill material were tested to explore the best proportion. An experimental set-up of a backfill-coupled heat exchanger system was then constructed and filled with the backfill material to determine the heat storage and release processes on the thermal performance of the system. The influence of the composite backfill material and surrounding rock temperatures on the energy efficiency of the backfill coupled heat exchanger system was evaluated. The results showed that, with the increase of the tailings substitution rate, the uniaxial compressive strength, specific heat capacity and density of the composite backfill material were reduced compared with the traditional backfill material, while the thermal conductivity and thermal diffusion coefficient were increased. Finally, 10% natural flake graphite instead of tailings was used to make the backfill body for testing. Compared with traditional backfill coupled heat exchanger system, when the surrounding rock temperature was 55 °C, the heat discharging and the total efficiency of natural flake graphite - backfill coupled heat exchanger system increased by 579.1 kJ and 31.6 %, respectively. The research results provide a reference for the application of backfill coupled heat exchangers in engineering practice. [ABSTRACT FROM AUTHOR]

The properties of high performance concrete, mainly in the fresh state are governed by the flow behaviour of the paste phase, which is controlled by the dispersion of cement particles by the superplasticizer. In this paper, experimental procedures for evaluating the flow behaviour of cement paste with different types and dosages of superplasticizers are studied. The rheological nature of the paste is represented through the Bingham and Herschel-Bulkley models. It is observed that the Marsh cone flow time, mini-slump spread and the rheological parameters show the same trend with change in dosage of superplasticizer. Also, the rheological parameters increase with time and rate of increase is more significant at dosages less than the saturation dosage, as determined from the Marsh cone test. It is confirmed that the Marsh cone flow time can be predicted using an appropriate model. [ABSTRACT FROM AUTHOR]

The paper explores the potential of applicability of Genetic programming approach (GP), adopted in this investigation, to model the combined effects of five independent variables to predict the mini-slump, the plate cohesion meter, the induced bleeding test, the J-fiber penetration value, and the compressive strength at 7 and 28 days of self-compacting slurry infiltrated fiber concrete (SIFCON). The variables investigated were the proportions of limestone powder (LSP) and sand, the dosage rates of superplasticiser (SP) and viscosity modifying agent (VMA), and water-to-binder ratio (W/B). Twenty eight mixtures were made with 10-50% LSP as replacement of cement, 0.02-0.06% VMA by mass of cement, 0.6-1.2% SP and 50-150% sand (% mass of binder) and 0.42-0.48 W/B. The proposed genetic models of the self-compacting SIFCON offer useful modelling approach regarding the mix optimisation in predicting the fluidity, the cohesion, the bleeding, the penetration, and the compressive strength. [ABSTRACT FROM AUTHOR]

Abstract: This investigation was undertaken to evaluate the influence of the dosage of the second generation of viscosity modifying agent (diutan gum) on fluidity and rheological parameters of cement-based materials grout compared to welan gum. All grouts were made with 0.40 water-to-binder ratio (W/B). The fresh properties of control grouts made without any viscosity modifying agent (VMA) and with superplasticizer (SP) were compared to those of grouts made with 0.02, 0.04, 0.06 and 0.08% diutan gum by mass of binder. Similar mixes made with welan gum were compared to those containing diutan gums. The effect of admixtures on fluidity and rheological parameters are discussed in this paper. The effect of the replacement of cement by pulverised fly ash (PFA) was also investigated. Grouts with replacements of PFA of 5, 13 and 20% by mass were used with the same W/B. Similar control grouts and mixes incorporated different dosages of PFA made with welan gum were made in order to compare the fluidity and the rheological parameters to the previous grouts made with diutan gum. The results show that the increase of the dosage of diutan gum and welan gum for a given dosage of SP increases significantly the yield value, the apparent and plastic viscosity and reduces the fluidity. With an increase in dosage of SP, the apparent viscosity at low shear rate decreases dramatically than that at high rate of shear rate due to the pseudo-plastic rheology of the grouts containing VMA. Both VMAs exhibited high apparent viscosity values at low shear rates which were attributed to the entanglement and intertwining of VMA polymer chains at low shear rate and association of water between adjacent chains. For a given dosage of VMA, diutan gum showed a high apparent viscosity than welan which could be attributed to the molecular weight and to the long-side chain of diutan gum leading to greater entanglement and intertwining. For any given dosage of SP, the diutan gum exhibited higher yield value and plastic viscosity than welan gum. Diutan gum grouts demonstrate a greater yield value and apparent and plastic viscosity than welan gum for control and PFA grouts. The replacement of cement by PFA resulted in a reduction of yield value and an increase in plastic viscosity. [Copyright &y& Elsevier]

In this paper the parameters of cement grout affecting rheological behaviour and compressive strength are investigated. Factorial experimental design was adopted in this investigation to assess the combined effects of the following factors on fluidity, rheological properties, induced bleeding and compressive strength: water/binder ratio (W/B), dosage of superplasticiser (SP), dosage of viscosity agent (VA), and proportion of limestone powder as replacement of cement (LSP). Mini-slump test, Marsh cone, Lombardi plate cohesion meter, induced bleeding test, coaxial rotating cylinder viscometer were used to evaluate the rheology of the cement grout and the compressive strengths at 7 and 28 days were measured. A two-level fractional factorial statistical model was used to model the influence of key parameters on properties affecting the fluidity, the rheology and compressive strength. The models are valid for mixes with 0.35–0.42 W/B, 0.3–1.2% SP, 0.02–0.7% VA (percentage of binder) and 12–45% LSP as replacement of cement. The influences of W/B, SP, VA and LSP were characterised and analysed using polynomial regression which can identify the primary factors and their interactions on the measured properties. Mathematical polynomials were developed for mini-slump, plate cohesion meter, inducing bleeding, yield value, plastic viscosity and compressive strength as function of W/B, SP, VA and proportion of LSP. The statistical approach used highlighted the limestone powder effect and the dosage of SP and VA on the various rheological characteristics of cement grout. [Copyright &y& Elsevier]

• Initial mixing water temperature will affect the early dissolution rate for solid activator. • Initial mixing water temperature can extend AAS slump life. • Initial mixing water temperature has minimal effect on later strength. • Initial mixing water temperature had a great influence on early deformation. During hot and cold weather, initial mixing water temperature is a critical parameter in controlling the fresh and hardened properties of cement-based materials. With the advent of Alkali Activated Materials (AAMs), the effectiveness of such a technique becomes questionable as the hydration mechanism differs from that of the ordinary Portland cement (OPC). Therefore, this study focuses on evaluating the effects of initial mixing water temperature on the performance of one-part Alkali Activated Slag (AAS). Various AAS mixtures prepared by different mixing water temperatures (i.e. 0 °C, 10 °C, 20 °C, and 30 °C) were tested. Fresh and hardened properties, including mini-slump, slump loss rate, setting time, the heat of hydration, compressive strength, and shrinkage, were investigated. Results reveal that the initial mixing water temperature plays a dominant role in controlling solubility and dissolution rates for different ingredients (i.e. solid activator and slag). This, in turn, had affected the hydration process and consequently the development of various properties. Slump life and setting time were found to extend as the initial mixing water temperature reduced while the strength was not harmed. Saving energy consumed for warming water during cold weather concreting will also increase concrete sustainability. It is anticipated that these findings will pave the way for a broader implementation of such green sustainable materials in the construction sector. [ABSTRACT FROM AUTHOR]