Shrinkage Reducing Admixture Research Articles

SHRINKAGE MITIGATING STRATEGIES ON HIGH-PERFORMANCE SELF-CONSOLIDATING CONCRETE (HP-SCC)

Cracking in high-performance self-consolidating concrete (HP-SCC) is a significant concern that must be addressed during design and construction. HP-SCC is a concrete type reinforced with high-strength fibers, such as steel or synthetic fibers, to enhance its mechanical properties. HP-SCC is known for its high flowability and ability to self-consolidate without vibration, exceptional strength, durability, and crack resistance compared to conventional concrete. HP-SCC is highly durable and can withstand various environmental conditions and aggressive exposures. Combining high-strength fibers and advanced cementitious materials in HP-SCC improves resistance to chemical attacks, freeze-thaw cycles, abrasion, and impact. Utilizing an expansive agent (EA), shrinkage-reducing admixture (SRA), and saturated lightweight sand (LWS) ensures HP-SCC with a low risk of cracking. This study investigates using different types of EAs to improve compressive and flexural properties. Furthermore, the study investigates the combination of fiber, EA, and LWS in promoting high resistance to autogenous and total shrinkage. The dense microstructure of HP-SCC also contributes to its durability by reducing permeability and minimizing the ingress of moisture and harmful substances.

Mechanism underlying effect of expansive agent and shrinkage reducing admixture on mechanical properties and fiber-matrix bonding of fiber-reinforced mortar

Expansive agent (EA) and shrinkage reducing admixture (SRA) are utilized to reduce shrinkage and risk of cracking in concrete. EA compensates shrinkage by initial expansion, and SRA reduces surface tension in the pore fluid. Although EA and SRA effectively reduce shrinkage, they can impair micro-structure of concrete at high contents. The shrinkage reduction effect of EA and SRA is well known; however, there is limited knowledge about their negative effect on microstructure and fiber matrix interfacial transition zone (ITZ). The current study explores the effect of using 10 % CaO-based EA, 2 % SRA, and their combination on mechanical, shrinkage, and microstructural properties of fiber-reinforced mortar (FRM) made with 0.5 % steel fiber. The hydration products are characterized by X-ray diffraction and derivative thermogravimetric. Backscatter scanning electron microscopy, energy dispersive spectroscopy (EDS), and micro-hardness experiments are employed to characterize the microstructure of fiber-matrix ITZ at two distances of 50 and 100 μm surrounding the fibers. Experiment results indicate that the quality of ITZ and fiber-matrix bonding is impaired by using either EA or SRA. The highest drop is obtained by the combination of EA and SRA. The element analysis by EDS line and point scanning reveals the presence of longer silicate chain and stronger fiber-matrix ITZ in the reference mixture. Micro-hardness measurements confirm higher mechanical properties at the ITZ between 50 and 100 μm surrounding the fibers. Thermodynamic simulations and phase assemblages interpret the influence of EA and SRA on mechanical properties and shrinkage.

Evaluation of the Fresh Properties of Cement Pastes: Part I-Response Models Applied to Changes in the One-Variable-at-a-Time Method.

The workability of cement-based materials is one of the features that makes these construction materials the most used worldwide. Measuring and understanding how cement-based constituent materials affect fresh properties depends on the experimental plans. The experimental plans deal with the constituent materials used, the tests carried out, and the run of experiments. Here, the fresh properties (workability) of cement-based pastes are evaluated based on the diameter in the mini-slump test and the time in the Marsh funnel test being measured. This overall study is composed of two parts. In Part I, tests were carried out on several cement-based paste compositions incorporating distinct constituent materials. The effects of the distinct constituent materials on the workability were analyzed. Furthermore, this work deals with an approach to the run of experiments. A typical run of experiments was applied, with basic sets of mixed compositions being studied by only changing one input parameter at a time. This approach used in Part I is faced with a more scientific approach applied in Part II of the work where, based on the design of experiments, multiple input parameters were changed at a time. This work showed that a basic run of experiments is quick and easy to apply and leads to results for simple analyses; conversely, it lacks information for advanced analyses and scientific conclusions. The tests carried out included studies on the effect on the workability caused by changes in the limestone filler content, the type of cement, the water-to-cement ratio, distinct superplasticizers, and shrinkage-reducing admixture.

Effect of internal curing and shrinkage-mitigating materials on microstructural characteristics of fiber-reinforced mortar

Internal curing (IC) and other shrinkage mitigating materials are employed to reduce shrinkage and risk of cracking. This study investigates the efficiency of individual versus combined use of IC and shrinkage mitigating materials on key characteristics of fiber-reinforced mortar (FRM). The investigated mixtures include a 25% pre-saturated lightweight sand (LWS) that is added individually and combined with 10% CaO-based expansive agent (EA) and 2% shrinkage reducing admixture (SRA). This elucidates the synergistic effect of high content IC and EA/SRA on macro- and micro-mechanical characteristics of FRM, especially at the interface of the matrix with fibers. Mechanical properties, microstructural characteristics, and fiber–matrix bonding of FRM made with 0.5% steel fibers are investigated. The results show that the use of IC with EA and SRA completely compensates for shrinkage at 56 days. The highest compressive and fiber pull out strengths are observed for FRM with IC and without EA/SRA due to the densification of the interfacial transition zone (ITZ) confirmed by microstructural analysis. Such improvement is associated with the lower porosity of the cement paste and longer silicate chain—higher Si/Ca—obtained by FRM made with LWS. Although the combination of both EA and SRA with IC leads to 180 μstrain expansion after 56 days, the corresponding mixture presents the weakest ITZ and inferior mechanical properties.

Deformation Mechanisms of Magnesium Silicate Hydrate Cement with a Shrinkage-Reducing Admixture under Different Curing Conditions

Magnesium silicate hydrate (M-S-H) cement, a type of green building material, has poor volume stability (i.e., large shrinkage deformation), which limits its application. As a new type of admixture, the behavior of a shrinkage-reducing admixture (SRA) in M-S-H cement has not been studied. Therefore, in this research, the effect of SRA on the shrinkage properties of the M-S-H cement system was evaluated. The mechanism of SRA was investigated by surface tension measurement, hydration heat testing, thermogravimetric analysis, and pore structure analysis. Experimental results indicate that SRA can reduce the shrinkage of the M-S-H mortar, and the optimal effect is exerted when the dosage is 3.0%, drying shrinkage decreases by 22.6%, and autogenous shrinkage decreases by 60% on day 28. However, it may also adversely affect strength development. The presence of SRA in M-S-H cement can reduce pore solution surface tension, delay hydration, and maintain relative humidity within the slurry, which can be maintained at 82.0% on day 28. It can also increase pore size and porosity. The inhibitory effect of SRA on the shrinkage of M-S-H mortar is valuable for its future practical applications.

Effect of microfibers or SRA on the shrinkage and mechanical properties of alkali activated slag/fly ash-based mortars incorporating recycled fine aggregate

Alkali activated slag and fly ash (AASF) systems present satisfactory mechanical properties compared to portland cement systems; however, the high shrinkage and cracking potential of these binders require preventive strategies. Furthermore, to improve the sustainability of such systems, using recycled fine aggregate (RFA) in concrete or mortar can help reduce the problem of depletion of aggregate reserves and disposal of laboratory concrete wastes. This study aims to evaluate the shrinkage characteristics of AASF mixtures incorporating RFA reinforced with polypropylene (PP) or steel fiber (SF) or containing shrinkage reducing admixture (SRA). In this regard, the compressive and uniaxial tensile strength and drying, autogenous, and restrained shrinkage properties of AASF mortars containing RFA were studied. Furthermore, in order to investigate the effect of RFA, natural sand was replaced with RFA by 20%, and as a result of this replacement, a slight decline in mechanical properties and free shrinkage was observed. The inclusion of microfibers enhanced the tensile strength of mortars, and the utilization of 0.6% microfibers reduced the drying and autogenous shrinkage of mixtures up to 20% and 15%, respectively, while the incorporation of 0.3% of microfibers was insufficient to reduce the free shrinkage. The addition of 1.5 and 3% SRA significantly decreased the drying and autogenous shrinkage up to 28% and 53% compared to the reference mixture, respectively. The restrained shrinkage test results indicated that incorporating microfibers or SRA extended the crack initiation time up to 6.4 and 14.6 times compared to the reference. The stress rate and crack width values of mortars decreased by 74% and 91% with the inclusion of 0.6% microfibers or 3.0% SRA, respectively. The overall test results showed that AASF mixtures incorporating 0.6% SF, 0.6% PP fiber, or 3% SRA exhibited satisfactory results in terms of shrinkage properties without compromising the mechanical performance.

Concrete Shrinkage Analysis with Quicklime, Microfibers, and SRA Admixtures

This research explores the effect of various humidity conditions and the efficiency of shrinkage-reducing admixtures on the free shrinkage strain of ordinary Portland cement (OPC) concrete and its mechanical properties. An OPC concrete C30/37 mixture was replenished with 5% of quicklime and 2% of organic-compound-based liquid shrinkage-reducing agent (SRA). The investigation revealed that a combination of quicklime and SRA led to the highest reduction in concrete shrinkage strain. Polypropylene microfiber addition was not so effective in reducing the concrete shrinkage as the previous two additives did. The prediction of concrete shrinkage without quicklime additive was performed according to EC2 and B4 model methods, and the obtained results were compared with the experimental ones. The B4 model evaluates the parameters more than the EC2 model does and, therefore, was modified to calculate the concrete shrinkage for the case of variable humidity and to evaluate the effect of quicklime additive. The experimental shrinkage curve that best coincides with the theoretical one was that obtained by the modified B4 model.

Effect of lightweight sand and shrinkage reducing admixture on structural build-up and mechanical performance of UHPC

Pre-saturated lightweight sand (LWS) and shrinkage reducing admixture (SRA) can be used to mitigate autogenous shrinkage of ultra-high-performance concrete (UHPC). However, their individual and synergetic effects on structural build-up that is essential for thin bonded bridge deck overlay rehabilitation and 3D printing have not been well understood. This study investigates the impact of LWS and SRA on structural build-up of UHPC with mini-slump flow of 190 ± 10 mm. Furthermore, the cement hydration, autogenous shrinkage, mechanical performance, and porosity of UHPC prepared with LWS and SRA were studied. Test results show that the structural build-up enhanced from 90 to 138 Pa/min with the increase of the LWS content from 0 to 25% given the lower surface coverage ratio of high-range water reducer onto cement particles. The incorporation of 2% SRA led to the lowest structural build-up of 64 Pa/min due to the lower bridging effect of early-age hydration products. The LWS17&SRA1 mixture exhibited higher structural build-up of 105 Pa/min, lower autogenous shrinkage of 340 με, as well as comparable compressive strength, elastic modulus, and flexural strength of 139 MPa, 48 GPa, and 19 MPa compared to the Reference mixture prepared without any LWS and SRA that had the corresponding values of 90 Pa/min, 535 με, 142 MPa, 50 GPa and 19 MPa, respectively. The comparable mechanical performance was due to the increased effect of LWS on cement hydration and pozzolanic reaction of silica fume counteracted the reduced influence of SRA.

Bond Behavior of Steel Rebar Embedded in Cementitious Composites Containing Polyvinyl Alcohol (PVA) Fibers and Carbon Nanotubes (CNTs).

In this study, pull-out tests were conducted to investigate the bond behavior of a rebar embedded in cementitious composites with polyvinyl alcohol (PVA) fibers and carbon nanotubes (CNTs). In the cementitious composites, the binder consisted of ordinary Portland cement, blast furnace slag, and fly ash, with a weight ratio of 39.5, 21.0 and 39.5%, respectively, while the nonbinder consisted of quartzite sand, lightweight aggregate, superplasticizer, and shrinkage-reducing admixture. The water/binder ratio and volume fractions of the PVA fibers were 32.9% and 2.07%, respectively. In the test program, the rebar diameter (D13, D16, and D19) and CNTs mix ratio (0.0, 0.1, 0.2, and 0.3 wt.%) were considered as the test variables. The test results showed that the bond strength of a rebar increased as the rebar diameter decreased or as the CNTs mix ratio increased. Based on the test results, a new, simple model has been proposed with consideration of the rebar diameter, as well as the CNTs mix ratio. Comparing the test results, it was investigated that the proposed model generally represented the bond behavior well, including the bond strength and the corresponding slip of a rebar embedded in PVA cementitious composites, with or without CNTs.

Investigating the effect of hybrid curing on mechanical and durability properties of normal-strength concrete

Internal curing is commonly implemented in concrete mixes with water-to-cement (w/c) ratios lower than 0.4 because of self-desiccation. Normal Strength Concrete (NSC) with w/c ratios higher than 0.5 would benefit from internal curing because of labor and resource-saving and quality control issues. However, the loss of curing water due to evaporation reduces internal curing efficiency in high w/c ratio mixes. This research evaluates a novel approach to minimizing internal curing water loss at an early age by combining internal curing with permeability-reducing admixtures (PRA) and shrinkage-reducing admixtures (SRA). Different mixtures containing binary and ternary combinations of admixtures and internal curing agents were investigated. According to the findings, admixtures such as SRA and PRA can play a vital role in maximizing the potential of internal curing in high w/c mixes. Furthermore, the ternary combination of LWA and the two admixtures has proven promising based on the observed overall improvement in NSC properties.

Effect of additional water or superplasticizer on key characteristics of cement paste made with superabsorbent polymer and other shrinkage mitigating materials

The use of superabsorbent polymer (SAP) coupled with expansive agent (EA) or shrinkage-reducing admixture (SRA) can effectively reduce shrinkage of cement-based materials. However, SAP particles at high contents can adversely affect rheological and mechanical properties. Securing proper workability can be accomplished by additional water or adjusting the superplasticizer (SP) demand. There is an uncertainty about the efficiency of these approaches to workability compensation. This study evaluates the effect of additional water or SP on key properties of cement paste made with SAP and relatively high content of EA or SRA. Macro and micro mechanisms underlying the effect of combined shrinkage mitigating strategies on the performance of cement paste made with 0.4 water-cementitious materials ratio are investigated. Results indicate higher efficiency of increasing SP demand by 0.6% versus the addition of water by 30 g per gram of SAP. Up to 80% higher compressive strength is obtained for the mixtures made with additional SP, which is attributed to up to 33% reduction in capillary porosity and smaller pore-size distribution of the hydrated cement paste. In the presence of high EA content, the use of additional SP prevents excessive initial expansion in the paste with additional water.

Effect of polyether shrinkage reducing admixture on the drying shrinkage properties of alkali-activated slag

The effects of a shrinkage-reducing admixture (SRA) on the hydration, mechanical properties, drying shrinkage, weight loss, and microstructure of alkali-activated slag (AAS) were investigated in this paper. The results show that adding SRA in a certain range (≤2%) can make the exothermic peak move forward and increase the exothermic heat of hydration. The mechanical properties of AAS deteriorated as the SRA content increases. The addition of SRA had no effect on the type of hydration products, but the amount of hydration production decreased as the SRA content increases. The volume of the pore of AAS slurry containing SRA also decreased, while the pore size became larger, which was strongly related to drying shrinkage. Our results support the contention that the mechanism by which SRA reduces drying shrinkage is mainly related to the decrease of surface tension, the generation of fewer pores, and the coarsening of the pore structure.

Synthesis and Performances of Shrinkage-Reducing Polycarboxylate Superplasticizer in Cement-Based Materials.

Reducing or eliminating cracks caused by shrinkage of cementitious materials remains a daunting challenge for construction engineers. Drying shrinkage and autogenous shrinkage are the main shrinkage types in the service process of cement-based materials, which have a great impact on engineering applications. If cracks in concrete generate by drying or autogenous shrinkage, the mechanical properties, water resistance and durability of concrete will be also affected. It is an effective method to use chemical admixtures to inhibit the shrinkage of cement-based materials. Polycarboxylate plasticizer (PCE) is an important chemical admixture in cement-based materials and is widely used in practical engineering. It can bring great value by reducing the shrinkage effect through molecular design. Through our innovative design, a series of shrinkage-reducing polycarboxylate superplasticizers (SRPs) were synthesized, their molecular structures were confirmed by Fourier transform infrared spectroscopy (FTIR) and their molecular properties were determined by gel permeation chromatography (GPC). Furthermore, the shrinkage performances at different ages of the mortars containing the synthesized SRPs with different structures were systematically evaluated. The results showed that compared with the blank sample, the dry shrinkage rate and free shrinkage rate of the mortars containing SRP decreased by over 20% and 15%, respectively. Additionally, the shrinkage rates of the mortars containing SRP were significantly lower than that of the mortar containing conventional PCE, and moreover, the water-reducing performance was improved compared to conventional PCE. Based on the experimental results of surface tension and evaporation rate of different SRP solutions, the mechanism of the shrinkage-reducing effect was probed, as expected to provide guidance for the design and development of new shrinkage-reducing admixtures.

Benefits and drawbacks of using multiple shrinkage mitigating strategies on performance of fiber-reinforced mortar

Shrinkage mitigating strategies have been successfully used to prevent concrete cracking. Numerous studies have demonstrated the efficiency of shrinkage mitigating materials (SMM), such as expansive agent (EA), shrinkage reducing admixture (SRA), and superabsorbent polymer (SAP) on reducing shrinkage and cracking; however, few studies have addressed the limitations of using these materials. In addition, the mechanism of negative effect on microstructure and mechanical properties when these materials are used at high contents or in combinations is not well defined. This study investigates the effect of CaO-based EA, SRA, and SAP on compressive strength development, fiber pull-out strength, and shrinkage of fiber-reinforced mortar (FRM) mixtures. Hydration kinetics and internal relative humidity are also determined. Advanced microstructural characterization techniques are employed to explore the mechanism underlying the effect of SMM on the mechanical properties and shrinkage of FRM mixtures. Test results indicate that FRM made with coupled systems of SMM limited to 5% EA, 1% SRA, and 0.25% SAP are preferred. The preferred SMM combination considering compressive strength, fiber pull-out strength, and shrinkage is the coupled system made of EA and SRA. High heat of hydration obtained using 10% EA results in excessive portlandite formation and high expansion, which adversely affects the mechanical properties. The use of 0.5% SAP with additional internal curing water contributes to the excessive expansion of SAP particles and creation of voids into the matrix, which reduce compressive strength and fiber-matrix bonding. The results revealed that the individual use of 7.5% EA and coupled use of 5% EA either with 0.5% SRA or 0.125% SAP can result in producing flowable, high strength, and low shrinkage FRM mixtures applicable to repair.

Synergistic effect of shrinkage mitigating materials on rheological properties of flowable and thixotropic cement paste

This study investigates the effect of individual and combined additions of CaO-based expansive agent (EA), shrinkage reducing admixture (SRA), and super absorbent polymer (SAP) on key characteristics of flowable cement paste mixtures proportioned with a water-to-cement ratio of 0.40. Of special interest is the effectiveness of these admixtures to mitigate shrinkage of cementitious materials for 3D printing. Static and dynamic yield stress, plastic and apparent viscosities, and thixotropy were evaluated at 20-min intervals up to 90 min. Compressive strength development and autogenous shrinkage were also determined. A factorial design approach was developed to evaluate the synergetic effects of the shrinkage mitigating materials (SMM) on performance. Test results showed that the use of any given SMM increases the static and dynamic yield stress, plastic viscosity, and thixotropy. The individual use of SRA and the combination of EA-SRA presented the highest effect on reducing 20-min plastic viscosity and dynamic yield stress, respectively. The combinations of EA-SAP almost tripled the 90-min static yield stress. The individual or combined use of the SMM, especially EA and SAP, significantly reduced autogenous shrinkage. Such systems, however, reduced the 28-d compressive strength by 14%–65%. The lowest value was obtained with the paste made with EA-SRA. A multi-objective optimization based on the measured properties was performed. The results revealed that the use of 10% EA either with 0.125% SAP or 1% SRA can result in producing flowable and thixotropic cement paste with high pumpability and buildability for 3D printing applications, no autogenous shrinkage, and high strength.

Effects of Shrinkage Reducing Admixture and Polypropylene Fiber Utilization on Some Fresh State, Mechanical and Durability Properties of Khorasan Mortar

ABSTRACT This study aimed to improve the mechanical and durability properties of Khorasan mortar, a type of lime-based mortar, using polypropylene shrinkage reducing admixture (SRA) and fiber. In addition to the control mixture without fiber and chemical admixture, three series of mixtures were prepared. The first series contains 0.4–0.6-0.8% polypropylene fiber by total volume; the second series contains SRA at the 0.05–0.1-0.15% by binder weight; the third series consists of mixtures containing both fiber and the SRA. Within the scope of the study, some fresh state, mechanical and durability properties were determined. The results show that utilization of fiber and SRA reduced the length change depending on drying-shrinkage and mass loss due to abrasion compared to the control mixture. In addition, the 90-day flexural and compressive strength values for all mixtures were lower than the 28-day results. It was determined that the decrease in strength values is less than the control mixture with the utilization of fiber and SRA because of the degradation in drying-shrinkage.

On the mechanisms of shrinkage reducing admixture in alkali activated slag binders

Shrinkage-reducing admixture (SRA) efficiency as a shrinkage mitigation technique has been proven for the alkali-activated slag (AAS) system. However, the controlling mechanism is a debatable subject. Moreover, it has been reported that SRA may retard strength development and slag hydration. Hence, this study explores the behaviour of SRA and its interactions with AAS's pore solution and systems. It showed that SRA affected AAS similarly to ordinary Portland cement (OPC), reducing pore solution's surface tension and maintaining a high internal relative humidity level. However, the critical micelle concentration of SRA (i.e. 9%) was identified beyond which it self-aggregated in the bulk solution, reducing its efficiency. Chemical analysis of the extracted AAS pore solution showed how the presence of SRA impacted the aqueous electrolyte AAS pore solution. Besides, SRA reduced the dissolution affinity of ions (i.e. the cation/anion concentrations), retarding the hydration reaction and extending the setting time. Nuclear magnetic resonance results confirmed that SRA addition lowered the polymerisation degree for C-A-S-H, thereby reducing shrinkage driven by C-A-S-H syneresis. The findings of this study highlighted the critical roles of AAS pore solution composition and the formation of hydration products in the presence of SRA on AAS shrinkage behaviour and the development of other properties.

Shrinkage performance of concrete for shotcrete use restrained by rock in hot and dry tunnel environment

The shotcrete shrinks greatly in the hot and dry environments, and the shotcrete is easy to crack or even debond under the restraint of the surrounding rock. In this context, a concrete-rock restrained shrinkage test device is used to study the shrinkage performance of concrete in the hot and dry environments of 80 °C, and the inhibitory effect of steel fiber and shrinkage reducing admixture on concrete shrinkage is explored. A concrete-rock restrained shrinkage mechanics model is established to calculate the interfacial restraint force and the distribution of stress and strain on the concrete section. The results show that the concrete expands at the initial stage under hot and dry environments, but the shrinkage of the concrete increases rapidly with the increase of age, and the growth rate slows down after a certain age and finally stabilizes. With the increase of the distance to the bonding surface, the shrinkage deformation of concrete increase continuously, and the stress distribution transitions from the tensile stress zone to compressive stress zone. The end-hook steel fiber and shrinkage reducing admixture can significantly reduce the shrinkage deformation and interfacial restraint force of concrete.

A novel shrinkage-reducing polycarboxylate superplasticizer for cement-based materials: Synthesis, performance and mechanisms

The incorporation of polycarboxylate superplasticizers may increase the risk of shrinkage cracking of cement-based materials. Co-adding shrinkage-reducing admixtures (SRAs) may decrease the compressive strength or arise the incompatibility problem. Designing a novel superplasticizer with excellent shrinkage-reducing function by modifying molecular structures of polycarboxylate superplasticizers can be a promising approach.This study aims to synthesize a novel shrinkage-reducing polycarboxylate superplasticizer (SR-PCA) possessing shrinkage-reducing and water-reducing functions and to investigate its performance and working mechanisms in cementitious systems. The results indicate that SR-PCA improves the fluidity of cement paste and has a distinguished fluidity retention capability. SR-PCA prolongs the cement hydration induction period, hinders the nucleation and growth of C-S-H in the acceleration period, while enhances hydration degree and refines the pore structure at later ages. Moreover, it can also be deduced that most PCA adsorbs on the cement surfaces, however, SR-PCA is mainly in the pore solution. The shrinkage-reducing mechanism of SR-PCA in cement-based materials is attributed to lowering the surface tension of the pore solution, due to the presence of the unreacted esterification macromonomers (AA-C4-PE-600) and the unadsorbed SR-PCA molecular.

Experimental study on the effect of key mix design parameters on shrinkage and cracking resistance of dry-mix shotcrete

Shotcrete is used in a wide variety of repair applications that usually results in concrete elements having a large surface area. After curing, this large exposed surface area-to-volume ratio can lead to a non-uniform moisture distribution in the in-place shotcrete which will create differential drying shrinkage. The shrinkage and potential subsequent cracking depend on the selected material proportions and the curing regime. The three-fold focus of this study is to investigate (i) the possibility of improving the shrinkage performance of dry-mix shotcrete by optimizing the coarse aggregate and cement content, (ii) the influence of silica fume (SF) and a combined SF and fly ash (FA), (iii) and the influence of polymer, shrinkage-reducing admixture (SRA) and crack-reducing admixture (CRA) on shrinkage and cracking resistance of dry-mix shotcrete using a modified restrained shrinkage ring test. The results indicate that SF, FA, polymer, SRA, or CRA have the potential of reducing shotcrete rebound as well as improve their porosity and placement quality. The results also show that the effect of cement content on shrinkage is relatively small. The addition of SF or combined SF/FA increased the cracking potential of the dry-mix shotcrete mixtures while the addition of polymer, SRA, and CRA reduced the total free shrinkage and increased the cracking resistance of shotcrete. The results further indicate that shrinkage and cracking resistance of shotcrete are closely related to mixture parameters.