Fresh Mortar Research Articles

Combined effect of compressing fresh concrete and curing regime on bonding performance of high strength repair mortar

High strength concrete (HSC) is highly appropriate for the retrofitting and rehabilitation of reinforced concrete structures due to its low permeability and high bonding strength. However, its low workability and sensitivity to curing conditions pose significant challenges for its implementation in such projects. This study introduces a novel technique to overcome the workability barrier of HSC while enhancing its bonding strength under various curing conditions. To achieve this, four different pressures (0, 0.87, 2.61, and 5.23 MPa) were applied to fresh high strength repair mortar (HSRM) and HSC for durations of 2, 4, and 8 hours. Subsequently, different curing methods, including the wet sack method, steam curing method, and the use of curing compounds, were employed. The modulus of elasticity and compressive strength of HSC, in addition to bonding performance between substrate HSC and 28-day compressed HSRM, were evaluated using the “friction-transfer” and “twist-off” techniques, which are standard techniques for measuring the bonding strength of concrete both in the laboratory and in-situ. Also, to further assess the effect of curing regime and pressure on the microstructures of HSRM, SEM images of 28-day HSRM specimens were collected. The results indicated that increasing the pressure to 5.23 MPa and extending the duration to 8 hours enhanced the ultimate torsional shear strength between HSRM and substrate HSC by an average of 174%. Additionally, the mechanical properties of HSC were considerably enhanced by applying 5.23 MPa pressure over 8 hours. It is worth mentioning that the bonding strength between HSRM and substrate HSC without curing was highly affected by the duration of pressure application compared to the three investigated curing methods. The wet sack curing method was found to be the most effective for enhancing the degree of hydration and increasing the failure torsional shear stress of compressed HSRM specimens.

Bonding of Beech Wood to Mortar with a Novel Epoxy Hybrid-Adhesive: Performance in Dry and Wet Conditions

Composites made of timber and cementitious materials require a rigid connection to exploit their full composite action, which can be achieved by using full-surface adhesive bonding. In this work, we investigated a novel hybrid-adhesive system consisting of a silane-terminated polyurethane (STP) and epoxy resin for the bonding of beech wood timber to fresh mortar for use in timber-mortar composites (TMC). The mechanical performance and the influence of moisture on TMC produced by the wet-in-wet process (fresh mortar) was investigated and compared to the bonding of prefabricated mortar (prefab process). The STP-epoxy hybrid-adhesive showed a suitable bonding performance of beech wood to both, fresh mortar and precured mortar with median compression shear strengths of 4.57 MPa and 6.07 MPa, respectively. The fracture pattern showed the strength of the near-surface layer in the mortar, close to the adhesive, being often decisive for the bond performance. The same failure mode predominated in TMC beams after 3-point bending tests. The stability of the composite upon the influence of moisture is especially challenging when using beech wood due to its low dimensional stability. Thus, the moisture stability of the bond was investigated by compression shear tests after water immersion. It showed superior water stability compared to composites bonded with a pure epoxy resin. Nonetheless, a clear reduction in bond strength compared to the dry state was observed, with delamination of 25% of the wet-in-wet and 17 % of the prefab specimens during water immersion. Furthermore, it was seen that the adhesive waiting time played a decisive role in the wet-in-wet produced specimens influencing both, dry and wet shear strength.

Structural build-up of 3D printed earth by drying

In recent years, the potential of earth materials in construction has emerged as a sustainable pathway, offering environmental benefits compared to traditional methods. When used in raw form, earth materials can be recycled at the end of a building life, reducing construction waste. In parallel, integrating additive manufacturing into the architecture, engineering, and construction (AEC) sector has brought about a shift in construction dynamics, combining efficiency with precision. This paper bridges the study of 3D printing with earth-based fresh mortars, emphasising the capabilities of the “Forced Layer Drying” (FLD) technique in the additive manufacturing process to increase the mechanical performance of the printing mortar.This paper begins by defining the requisite rheological properties for successful 3D printing. A chosen material for this paper is speswhite kaolin. An instrumental aspect of our research is exploring an established model for the drying rate of saturated porous media, such as earth and concrete, and its application to predict the evaporation rate of saturated earth-based mortar in 3D printing with forced drying conditions. The Wind-Tunnel experiment was conducted to validate this model, examining the interplay of airflow speed and temperature on the evaporation rate. Further deepening this study, the soil water content and undrained shear strength are correlated, specifically based on models derived from oedometer geotechnical standard tests. This facilitated a comprehensive understanding of porous earth-based materials in various moisture scenarios. Our findings confirm that airflow, temperature, and the geometry of the printed object play instrumental roles in affecting evaporation rate, consequent mechanical performance, and structural build-up of the material. The paper wraps up by offering insights into the practical application of 3D printing using earth-based mortars, with a special focus on FLD technique.

Effect of CO2 mixing on the rheological and electrochemical properties of fresh mortar at the early age

The study aimed to elucidate the mechanism behind rheological modification due to CO2 mixing at the mixing and post-mixing stages from an electrochemical perspective. The results indicated that CO2 mixing reduced the flowability while increasing penetration resistance and static yield stress. The electrostatic attraction between particles with opposite surface charges and the bridging effect of calcium carbonate constitute the primary factors for influencing the rheological properties of mortar at an early age. The altered surface charge of carbonized cement particles, primarily resulting from CO2 injection lowering the pH and ion concentration, reversed the zeta potential of particles from the traditionally negative charge (-3.59 mV) to a positive value (+13.3 mV). Furthermore, CO2 mixing further enhanced the dissolution of cement particles and accelerated the hydration process, thereby increasing the rate of structural build-up. CO2 mixing was demonstrated to be a potential rheological modifier for 3D-printed concrete applications.

Physical and mechanical properties of special cementitious materials modified by nano-particles

Compared to ordinary Portland cement (OPC), sulphoaluminate/ferroaluminate cement (SAC/FAC) and aluminate cement (CAC) are the most promising repair materials due to their excellent early strengths, but the later strengths of SAC/FAC develop slowly, and the later strengths of CAC are obviously declined. This paper studied the effects of nano-SiO2 and nano-ZnO on the physical properties, mechanical properties and early hydration processes of three special cement-based materials and compared them with OPC-based materials. The strength development and early hydration mechanism were revealed by hydration heat, scanning electron microscopy and X-ray diffraction. The test results showed that with the increasing content of nano-SiO2, the setting time of the four cement pastes was gradually shortened, the fluidity of four fresh mortars was gradually reduced, and their compressive and flexural strengths at all ages were improved to different degrees. Nano-ZnO significantly prolonged the setting time of OPC paste and increased the fluidity of OPC mortar, which had a negative effect on its early compressive and flexural strengths, but enhanced its late strengths. After the addition of 1 % nano-ZnO, the initial and final setting time of OPC were about 12 times and 13.4 times that of ordinary OPC paste, respectively. The effect of incorporating nano-ZnO on the physico-mechanical properties of three special cements was similar to that of nano-SiO2. The strength loss of CAC mortar with two kinds of nanoparticles was greatly reduced. The incorporation of nano-SiO2 and nano-ZnO could promote the hydration process of three special cements, resulting in the denser microstructure and higher crystallinity of hydration products.

Study on the influence of early frost attack on the performance of cement mortar

The loss of strength and durability caused by early frost attack is the macro performance of internal microstructure deterioration. Understanding the influence mechanism of early frost attack at the micro level is necessary to avoid or minimize the early frost attack to macro performance. In this study, the influence of early frost attack on the strength, water sorptivity, chloride permeability, and microstructure of cement mortar was investigated. The fresh mortars were pre-cured for 10, 12, 14, and 16 h and then frozen at −10 °C for 7 days to simulate an early frost attack. After freezing, the standard curing (20 °C) was carried out until the testing. It is found that after standard curing of 28 days, the strength of early-frozen mortar can reach more than 95 % of the 28-day strength of unfrozen mortar. Interestingly, the sorptivity coefficient and total charge passed of early-frozen mortar are much higher than the level of unfrozen mortar, and the loss of resistance to water penetration and chloride ion penetration exceeds 20 %, indicating that early frost attack causes more severe damage to the durability than to the strength of mortar. Mercury intrusion porosimetry (MIP) results show that early frost attack can increase the pore volume of >50 nm and coarsen the pores within 10–50 nm. Correspondingly, key pore parameters (critical pore diameter, threshold pore diameter, and tortuosity) that affect the durability of mortar are also negatively affected. Energy dispersive spectroscopy (EDS) analysis also shows that after suffering early frost attack, the interfacial transition zone (ITZ) thickness of mortar is increased from 4 to 10 μm to 8–13 μm, and the probability of high Ca/Si ratios (4–10) in the ITZ is also increased. Finally, it is concluded that the coupling effect of pore structure coarsening and ITZ degradation leads to more severe durability loss.

The influence of selected grain size fractions of coal fly ash on properties of clay-cement mortars used for the flood levees construction

This study examines the influence of different grain size fractions of coal fly ash on the properties of clay-cement mortars used in flood levee construction. Dry aerodynamic separation and mesh sieving were used to obtain ultrafine, fine, and medium fractions of high-calcium and silica fly ash. The experimental results reveal that the rheological properties of fresh mortars are significantly influenced by these fractions. High-calcium fly ash mortars exhibit high reactivity and rapid increase in viscosity, with finer fractions showing the highest reactivity. Silica ashes show increased reactivity in the later stages of suspension hardening. Their spherical shape contributes to reducing internal friction during flow in initial technological operations. Furthermore, the compressive strength of hardened mortars improves as the particle size decreases for both ashes, resulting in a dense and uniform microstructure. The separation and fractionation of fly ashes contribute to the obtaining of fractions that influence the parameters of clay-cement suspension application on different scales. The results show the potential benefits of ash separation, which can bring advantages in terms of economic viability, engineering performance, and ecological sustainability.

Damage localisation in fresh cement mortar observed via in situ (timelapse) X-ray μCT imaging

This paper presents the outcome of a study focused on the evolution of internal damage in fresh cement mortar over 25 h of hardening. In situ timelapse X-ray computed micro-tomography (μXCT) imaging method was used to detect internal damage and capture its evolution in cement mortar hardening. During μXCT scans, the temperature released during the cement hydration was measured, which provided insight into the internal damage evolution with a link to a hydration temperature rise. The measured temperature during cement mortar hardening was compared with an analytical model, which showed a relatively good agreement with the experimental data. Using 20 CT scans acquired throughout the observed cement mortar hardening, it was possible to obtain a quantified characterisation of the porous space. Additionally, the use of timelapse μXCT imaging over 25 h allowed for studying the crack growth inside the meso-structure including its volume and surface characterisation. The results provide valuable insights into cement mortar shrinkage and serve as a proof-of-concept methodology for future material characterisation.

The Role of Water Content and Binder to Aggregate Ratio on the Performance of Metakaolin-Based Geopolymer Mortars

Geopolymers are in many applications a perfect alternative to standard cements, especially regarding the sustainable development of green building materials. This experimental study therefore deals with the investigation of different factors, such as the water content and the binder to aggregate ratio, and their influence on the workability of fresh mortar and its mechanical properties and porosity on different size scales. Although increasing the water content improved the workability and flow behaviour of the fresh mortar, at the same time, a reduction in compressive strength in particular and a lesser reduction in flexural strength could be demonstrated. This finding can be attributed to an increase in capillary porosity, as demonstrated by capillary water uptake and mercury intrusion porosimetry measurements. At the same time, the increasing water content led to an improved deaeration effect (low air void content) and to initial segregation (see the µXCT measurements). An alternative approach to enhance the compressive and flexural strengths of the mortar specimens is optimization of the binder to aggregate ratio from 1 to 0.25. This study paves the way for a comprehensive understanding of the underlying chemistry of the geopolymerization reaction and is crucial for the development of sustainable alternatives to cementitious systems.

Feasibility of underwater 3D printing: Effects of anti-washout admixtures on printability and strength of mortar

The dispersion and reduction in strength of concrete underwater pose significant challenges to advancing underwater 3D concrete printing technology. While employing anti-washout admixtures holds promise, there is a dearth of relevant research. Herein, a study using various potential anti-washout admixtures, such as micro silica (MS), nano silica (NS), glass fibers (GF), and hydroxypropyl methyl cellulose (HPMC), in mortar mixes was conducted. These mortar mixes were then printed underwater, and their performance in both fresh and hardened states was evaluated to develop underwater 3D printable mortars. The findings revealed that both MS and NS enhance the washout resistance, extrudability, and buildability of fresh mortar, while also improving the flexural, compressive, and bond strengths of hardened mortar. HPMC enhances underwater printability and bond strength, although it may negatively impact flexural and compressive strengths. GF exhibits adverse effects on underwater printability and mechanical properties and is incompatible with HPMC. Noticeably, the combination of MS, NS, and HPMC greatly enhances underwater printability (no dispersion and lowest extrudability/buildability variation coefficients) and mechanical properties (increasing flexural strength and bond strength by 21 % and 151 %, respectively). These findings led to the proposal of several mortar mixes deemed suitable for underwater 3D printing.

Properties of self-curing and self-cooling eco-friendly novel green cement-based mortar

In this study, mullein plant (MP) (Verbascum Thapsus) was replaced with cement at a dosage of 300 (the amount of cement in mortar for producing 1 m3 mortar) in cement-based mortars at different weight ratios (0%, 1.5%, 3%, 4.5% and 6%). To investigate the impact of MP on the hydration (internal) temperature and the formation time of hydration products in mortars, the mortars' interior temperature and moisture ratios were measured and recorded every minute for one day. It was concluded that the MP had a high-water absorption capacity and delayed the initial and final setting times. The optimum ratio of MP as a replacement for cement was found to be 1.5%. The study also investigated the effects of direct current (DC) application on fresh mortars (both with and without MP). The results showed that the 7-day mechanical strength of the reference mortars exhibited a significant increase with the application of DC. Previous studies have not explored the use of MP in cementitious composite materials. This study concluded that adding a specific amount of MP to cement-based materials can provide self-curing and self-cooling properties. This research is critical for water conservation as it develops a novel self-curing method.

Development of high-strength geopolymer mortar based on fly ash-slag: Correlational analysis of microstructural and mechanical properties and environmental assessment

Given the insufficient mechanical performance of existing fly ash-based geopolymer mortars under ambient curing conditions, this study is dedicated to developing a high-strength geopolymer mortar that meets the requirements of modern structural engineering. Based on the rheological performance tests of the fresh geopolymer mortar, the evolution of its rheological characteristics was revealed. Through macroscopic mechanical performance tests, the influence of slag content on the compressive and flexural strength of geopolymer mortar was clarified. Employing microstructural performance testing methods such as Thermogravimetric and Mercury Intrusion Porosimetry, the micro-mechanisms behind the improvement of mechanical properties were revealed. Utilizing the grey relational analysis method, a framework was established to analyze the correlation between the microstructural and macroscopic mechanical properties of geopolymer mortar. Additionally, an assessment system for evaluating environmental and economic benefits was developed using statistical analysis methods. The results show that increasing slag content enhances the yield stress and plastic viscosity of geopolymer mortar. Optimizing slag content boosts the compressive strength of fly ash-based geopolymer mortar, reaching up to 88.13 MPa under ambient curing conditions. An optimal amount of slag also promotes gel formation during polymerization, improving the internal pore structure. Furthermore, the content of reaction products correlates more strongly with macroscopic mechanical properties than pore structure characteristics. Geopolymer mortar also presents significant environmental and economic advantages over traditional cement-based materials, with its carbon and economic intensity indices at only 5.50 % and 10.80 %, respectively, of those in cement-based materials.

Liquid nitrogen frozen cementitious material and its potential applications: Inspired by refrigeration industry

Liquid nitrogen frozen cementitious material introduces a novel approach to utilizing cementitious material in engineering construction and maintenance. This process involves the quick-freezing of fresh cement mortar into blocks. Tests were conducted on the thawed cement mortar to evaluate key technical parameters such as compressive strength and fluidity. Microscopic analyses including mercury intrusion porosimetry, scanning electron microscopy, X-ray diffraction and thermogravimetric analysis were conducted for mechanism analysis. The results indicate that quick-freezing with liquid nitrogen has a minimal or negligible impact on the compressive strength and fluidity of cement mortar, with compressive strength decreasing by no more than 4 % and fluidity decreasing by no more than 2 %. The rapid hydration reaction suspended by utilizing the extremely low temperature characteristics of liquid nitrogen is the main contribution. The freezing blocks possess unique properties such as hydration suspending, low-temperature and non-dispersibility as solid, which can be utilized in some special engineering applications such as long-distance transportation, temperature control of large volume concrete or underwater structure repair.

The Applicat ion of Super Absorbent Polymer in Self-Healing Morta r: The Effect on Mechanical Properties

Super Absorbent Polymer (SAP) were used in various application, including in mortar production. The ability of SAP to absorb a high amount of water made this material become a promising water reservoir in the mortar that can later mitigate micro-cracks in concrete. Besides SAP, a nutrient must be embedded into self-healing mortar to support metabolism in bacteria-based self-healing mortar. However, adding SAP and nutrient was reported to decrease the mechanical properties of the resulting self-healing mortar. Thus, in this research, the modification in the mix design of mortar containing SAP and nutrient were observed. The water to cement ratio was decreased up to 0.3. The amount of SAP and entrained water added is based on its swelling capacity. The swelling capacity of SAP, the workability of fresh mortar, and the compressive strength of mortar were examined. The results show that the swelling capacity of SAP was affected by the pH and the presence of calcium ions in the solution. The higher the pH and the calcium ion in the solution, the lower SAP’s swelling capacity. Applying the modified mortar mix design containing SAP and nutrient proofed to mitigate the reduction in workability and compressive strength of the resulting self-healing mortar.

DEVELOPMENT OF DRY MIX MORTARS FOR FLOOR ELEMENTS

Dry mix mortars are widely used in construction projects for the implementation of construction works in new construction, reconstruction, and repair. The improvement of properties of dry mix mortars for the installation of floor screeds is relevant. The purpose of such mortars is to equalize the differences in the thickness of the floor surface, to create an intermediate layer characterized by the necessary strength, durability, and even surface with the possibility of decoration with various types of flooring. A step-by-step design of the composition of dry mix mortar for the installation of floor screeds was carried out. The ratio of fine aggregates and limestone filler was optimized according to the maximum packing density criterion, the required amount of plasticizer was selected according to the consistency index of the fresh mortar, and the minimum amount of Portland cement was selected to ensure the required strength.

Fresh and hardened properties for a wide range of geopolymer binders – An optimization process

The objective of this study was to identify the optimal geopolymer binder compositions produced from local industrial by-products and compare them with commercially available materials. The first part investigated the optimal binder composition by studying 27 mixtures. In this part of the research, three series of binders were created: the first series of 18 mixtures was Na-based fly ash-slag, the second series consisted of 8 mixtures of K-based fly ash-slag, and the third series were a mixture of metakaolin-slag based geopolymer. The compressive strengths of the mixtures at the age of seven days ranged from 2.18 to 96.23 MPa. The strength development is clearly defined by the components and proportions of the blends. Geopolymers reach about 80% of their 28-day strength in seven days. The 25% water content was optimal for slag-fly ash geopolymers. The strength of the material increased from 68.08 to 96.23 MPa when the Blaine surface area of the slag increased from 3500 to 4500 cm2/g. The optimal proportions of the alkali solution were the intermediate ratios: SiO2/Na2O = 2.0 and SiO2/K2O = 1.5. In the case where Visonta fly ash is prepared for blending, the fly ash content can be maximized by 30%–50% in addition to the blast-furnace slag. In the second part of the research, mortars were prepared from the selected binders: 4 mixtures were prepared with two different binders. In one of these mortars, the solid part of the binder consisted of local raw materials originating from Hungary. This mixture was prepared with 43 m% fine aggregates. The optimal composition of the tested 27 binders tested was selected as the geopolymer matrix for the production of three further mortar mixtures. In these geopolymer mortars, 55, 65, and 75 m% of aggregate applied. The flowtable values of fresh mortars decreased when the proportion of sand increased. The lower the additive content was, the higher the strength of the geopolymer mortar. The 28-day compressive strengths of filtered fly ash-slag mortar sample with 55%, 65%, and 75% of fine aggregate (F–S-a55, F–S-a65, and F–S-a75) made with the selected optimised filtered fly ash-slag geopolymer binder of group A-I.3 (F–S-A-I.3) varied between 11.39 and 40.15 MPa, whereas the Visont fly ash-slag mortar sample with 43% of fine aggregate (V–S-a43) has been 25.05 MPa. For 28 days, the density ranged between 1870 and 2204 kg/m3. The V–S-a43 is found to be the lowest-density blend. The chloride migration test revealed that geopolymer mortars with higher slag content have higher resistance to Cl− ions.

Effect of Water to Cement Ratio on Properties of Calcium Sulfoaluminate Cement Mortars

Calcium sulfoaluminate (CSA) cements are a promising alternative to Portland clinker, however, a thorough understanding of their properties is needed for their broader use in the industry. One of the topics that requires a good understanding is the effect of the w/c ratio on the properties of CSA cements. To this end, the aim of this paper was to provide research into the effects of a w/c ratio in the range of 0.45–0.6 on the properties of fresh and hardened CSA pastes and mortars. For fresh mortars, consistency and setting time, as well as plastic shrinkage tests, were conducted, and were complemented by hydration heat tests, carried out on pastes. For hardened mortars, tests of compressive and flexural strength and dry shrinkage, as well as SEM photography, were conducted. It was found that, regardless of a higher hydration rate, the increase in w/c ratio decreased flexural and compressive strength, as well as shrinkage, while increasing consistency, setting time, and hydration heat. Also observed was a significant decrease in strength between 3 and 7 days of curing in mortars with a high w/c ratio. It can be concluded that, regardless of the hydration rate, low w/c ratios in CSA mortars provide better properties than high w/c ratios.

The Role of Superplasticizers on the Workability Consistency of ECC Mortar Fresh Mortar Due to an Increase in the Percentage of Palm Shell Ash

Engineered cementitious composites (ECCs) are composites that have better attraction properties and behavior than concrete. ECCs are usually formed from cement, water, silica sand, cementitious materials, fibers, and other additives with a certain proportion. In this study, there are three types of ECC mortars (types AME, EM, and TEM) where these types are differentiated by the amount of cement used, the quantity of water, and the number of sand used. Each type uses ashes of palm shells with the same proportions of 0%, 5%, 10%, and 15% of the weight of cement. According to trial and error during the workability test, the number of superplasticizers used also increased according to the increase in the percentage of ash in the palm shell, where the variation of superplasticizers achieved was 0.70%, 1.59%, 2.49%, and 3.40% of the weight of cement. Based on the results of the slumpflow test, the average diameter of the ECC freshly mixed mortar was between 88 cm and 106.5 cm, and the T500 slump flow was between 0.28 seconds and 1.39 seconds. The test results show a fairly good workability consistency of all ECC fresh mortars, although there has been an increase in the percentage of palm shell ash used. Superplasticizer turns out to be very important in maintaining consistent workability of fresh ECC mortar mix.

A new strategy to enhance 3D printability of cement-based materials: In-situ polymerization

Printability is a crucial attribute for 3D-printed cement-based materials, as it not only governs the material's printability but also directly impacts the quality of the final structure. A good printability indicates that the printed materials are flowable for transport and extrusion, followed by a rapid increase in strength to establish a stable structure. In this paper, a novel strategy is proposed to enhance the 3D printability of cementitious materials by leveraging the rapid strength enhancement of fresh mortar during in-situ polymerization of acrylamide (AM) in the matrix within 30–60 min of contact with water. Prior to extrusion, AM monomers are absorbed onto cement particles to enhance the flowability of mortar to approximately 185 mm, thereby improving pumpability and extrudability of printed materials. Shortly after extrusion, in-situ polymerization of AM monomers within the mortar takes place, resulting in a sudden albeit modest strength increases in the fresh mortar, enhancing the buildability of the printed mortar. Moreover, the flexural strength of 3D printed filaments with 5 % AM are increased by 52.4 % at 28d, respectively. Meanwhile, the interactions between the AM in-situ polymerization and cement hydration are comprehensively discussed. This innovative approach to enhance 3D printability is expected to drive the advancement of 3D-printed materials with enhanced adaptability and superior properties.

The effect of slag and natural pozzolan on the rheological and compressive strength properties of recycled self-compacting mortar

Cement replacement materials are used in self-compacting concrete mixes to reduce the cement content and hence its environmental effect. This article examined the effects of ground granulated blast-furnace slag (S) and natural pozzolan (NP) powder on the rheological and mechanical properties of recycled self-compacting mortar (RSCM). Natural sand was replaced by 100% of recycled sand (RS) by volume; while cement was replaced by slag and NP up to 40% by weight of cement. The slump flow, V-funnel time, yield stress and plastic viscosity and compressive strength of RSCM are investigated and compared with natural self-compacting mortar. The results showed that fresh properties of RSCM meet the requirements of self-compacting mortar if slag and NP contents are limited to 35%. The increase in slag content increases the yield stress and the plastic viscosity of fresh mortars whereas a decrease in the rheological properties is noticed when NP content is increased. Increasing slag and NP content leads to a reduction in compressive strength of RSCM at early ages, but enhances compressive strength at later age. The cement substitution levels by 25% of slag and 15% of NP are the optimum for attaining the desired strength that compensate for strength loss due to the use of RS.