Theses and Dissertations - Department of Civil, Construction & Environmental Engineering

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Characterization and modeling of long-term behavior of frp-to-concrete interface in aggressive environments
(University of Alabama Libraries, 2015) Amidi, Shahrooz; Wang, Jialai; University of Alabama Tuscaloosa
Fiber reinforced plastics (FRP) composites have emerged as one the foremost structural materials in retrofit/rehabilitation of concrete structural members in last decades. The long-term durability of the FRP-to-concrete interface in aggressive environments places a critical role in the success of this technique. A comprehensive program using both the analytical and experimental approaches has been carried out in this study to examine the integrity and long-term durability of the FRP-to-concrete interface in presence of aggressive environments. Novel analytical solutions based on three-parameter elastic/viscoelastic foundation models have been developed for adhesively bonded joints first in this study to gain better understanding of stress transfer through FRP-to-concrete interface. These models overcome drawbacks in existing models by satisfying all boundary conditions and producing different peel stress distributions along two adhesive-adherend interfaces, making it possible to accurately predict the location of debonding initiation. These models have been verified with finite element analysis and experimental observations. Comprehensive experimental programs have been carried out to evaluate the deterioration of the FRP-to-concrete induced by moisture. In the first part, a novel environment-assisted subcritical debonding method using a wedge driving test has been proposed to examine the synergistic effect of the mechanical loads and environmental conditions on the deterioration of the FRP-to concrete interface. The deterioration of the interface induced by water has also been evaluated through measuring the residual fracture toughness of the FRP-to-concrete interface conditioned in water through two different ways. It has been found that conditioning method can have significant effect on the testing results. A novel wedge-split test has been proposed and carried out to directly measure the traction-separation law of the epoxy-concrete interfaces under mode I loading, which is not available in the literature. The potential of using silane coupling agent to improve the durability of the FRP-to-concrete interface has also been examined in the experimental program. Testing results confirm that the residual fracture toughness of the FRP-to-concrete interface attacked by moisture can be significantly increased by silane treatment.
Characterization of reinforced structural composites with carbon nanotubes grown directly on the fibers/fabrics using the Poptube Approach
(University of Alabama Libraries, 2017) Guin, William Edward; Wang, Jialai; University of Alabama Tuscaloosa
Carbon nanotubes (CNTs) are ideal candidates for the reinforcement of the matrix and interphase zone in polymer matrix composites (PMCs), due to their ability to more effectively bind the reinforcing fibers to the matrix material. This can lead to the enhancement of several critical composite properties – including interfacial shear strength and interlaminar fracture toughness – that are typically associated with a composite material’s resistance to delamination. Direct dispersion of CNTs into the matrix of the composites has been shown to be very difficult. A more effective way to reinforce PMCs using CNTs is to grow CNTs directly on the reinforcing fibers. To this end, a novel technique used to grow CNTs directly on carbon fibers has been developed at The University of Alabama and Auburn University. This method, referred to as the PopTube Approach, uses microwave irradiation to grow CNTs at room temperature in air, without the need for inert gas protection or additional feed stock gases. The simple nature of the PopTube Approach lends itself to large-scale, high-yield manufacturing that can be done in a cost effective manner. However, before this technique is developed beyond the laboratory scale, its effectiveness as a route to produce CNT-reinforced composites must be evaluated in a comprehensive manner. The objective of this work is to do just that – characterize the mechanical properties of CNT-reinforced composites produced via the PopTube Approach. A systematic experimental program is carried out to provide a comprehensive assessment of the effects of the PopTube Approach on a wide range of composite mechanical properties. Results show that the PopTube Approach provides for enhanced resistance to delamination with respect to several different loading events. Fractography studies are used to qualitatively understand the mechanisms responsible for these improvements in delamination resistance on the micro-scale. Results also suggest that improvements in delamination resistance via CNT reinforcement may come at the expense of the tensile properties of PMCs – which gives rise to the conclusion that in practice, the degree and manner of CNT reinforcement in PMCs should be carefully considered on an application-by-application basis. Together, the collection of studies performed herein provides a wide-ranging quantitative and qualitative assessment of the effects of the PopTube Approach CNT reinforcement scheme on the mechanical properties and behavior of polymer matrix composites.
End zone design for Alabama deep prestressed girders
(University of Alabama Libraries, 2016) Burkhalter, David; Aaleti, Sriram; Song, Wei; University of Alabama Tuscaloosa
Deep prestressed concrete bridge girders are becoming increasingly popular due to their ability to span longer distances and reduce the total cost of bridge projects. However, these girders have frequently been subject to end zone cracking during the transfer of prestress forces despite being designed to current AASHTO specifications. Previously, the Alabama Department of Transportation (ALDOT) has designed deep prestressed girders which can span up to 165 ft. During the fabrication of these girders, crack formations in the end zone were typically noticed. To address this concern, longitudinal reinforcement was added to the end zones. This solution controlled cracking to some extent but could not completely eliminate cracking. An experimental study was conducted to find a practical engineering solution to the problem of end zone cracking, as well as to develop a 78 in. deep prestressed bulb-tee girder design to reach a span length of 180 ft. 3D finite element modeling was used to find three practical alternative end zone modifications to the standard design. The modified designs included a lowered draping angle, partial debonding of the strands, and a combination of the two. Four 54 ft. long specimens, including three with end zone modifications, were fabricated at Hanson Pipe & Precast in Pelham, Alabama, and monitored during the detensioning process. The end zones were instrumented with steel and concrete strain gauges to better understand the complex behavior of girder end zones. External DEMEC instrumentation was also included at the girder ends to measure the transfer length of the strands in each specimen. The specimens were then load tested at the UA Large Scale Structures Laboratory (LSSL) to determine the effects of the modified end zone details on the girder capacity. Based on the study, modified girder end zone details are recommended to ALDOT for implementation.
Experimental and FEA Study of Structural Behavior of CLT Shear Walls for Wood Building Applications
(University of Alabama Libraries, 2021) Chowdhury, Farhan A.; Dao, Thang N.; Aaleti, Sriram; University of Alabama Tuscaloosa
Cross Laminated Timber (CLT) is emerging as a sustainable alternative to traditional building construction materials for tall buildings in high seismic regions. However, before they can be incorporated into the building codes, different categories of CLT shear wall systems need to be fully characterized and novel solutions must be implemented to overcome the limitations of existing timber systems. This dissertation addresses analytical modelling of unbonded post-tensioned (PT) CLT rocking wall (CLTRW) system for its use in both rectangular and nonrectangular configurations. A set of laboratory experimental tests and nonlinear finite element analysis (FEA) were compared to investigate and characterize the flexural and lateral behavior of CLTRW system. The flexural performance was studied using a full-scale, 5-layer rectangular CLT panel testing in three-point loading configuration. A three-dimensional (3D) finite element (FE) model with nonlinear geometry and contact properties was developed in ABAQUS using measured material properties. The FE model was validated using the experimental data from the CLT panel bending test. Based on the validated FE model, additional FE models of previously tested post-tensioned CLTRW panels with different wall aspect ratios and tendon configurations were also developed. A close agreement between the measured and FEA models was found in the stiffness behavior, which suggested that the proposed nonlinear FE modelling approach can be employed to predict the performance of other CLTRW systems. This research further analytically investigates shear behavior of high stiffness web-to-flange connections for nonrectangular CLTRW system. The proposed shear connections use spatially arranged self-tapping screws (STS) together with ultra-high-performance concrete (UHPC) shear-keys. 3-D nonlinear FE models for connections with and without UHPC were validated using the available experimental data, which showed that the inclusion of UHPC would significantly improve the stiffness of the connections. The FEM technique for connections was subsequently used to evaluate the lateral load performance of a 36-ft tall, T-shape CLTRW wall with multiple connections. The results from this model were compared to a T-wall without shear-key connections. It was found that the wall with high-stiffness shear-key connections showed better lateral load performance compared to traditional connection wall.
Experimental investigation of long term and lateral load behavior of CLT shear walls for mid-rise wood buildings
(University of Alabama Libraries, 2019) Hossain, Md Kobir; Aaleti, Sriram; University of Alabama Tuscaloosa
There is a recognized need for tall building (8-20 story) construction in the United States due to growing population in the urban areas. In addition, there is a significant emphasis placed by the communities on sustainability. Wood is a sustainable construction material with a negative carbon footprint in comparison to steel and concrete, which are the traditional building materials used predominantly in tall buildings. Traditional Light Wood Frame Shear Wall system used in residential building construction in the U.S. cannot be used to construction tall building as it fails to provide necessary strength and stiffness. Mass timber panel such as Cross-Laminated Timber has been recognized as a promising building construction material in recent times and has been used in hundreds of building mostly in low seismic regions. However, to realize an all wood tall building in high seismic areas, lateral load resisting system (LLRS) using CLT needs to be developed and characterized before its implementation into building construction. This research focusses on addressing some of the issues in developing a robust LLRS using unbonded post-tensioned rocking CLT wall system for high seismic application. The parameters that affect the behavior of this system such as the compression, moisture diffusion and creep behavior of CLT material were studied by conducting laboratory testing. The performance of CLT rocking wall system was investigated through laboratory testing of four full scale specimens using different wall dimensions and detailing to gain a thorough understanding of this system behavior under reverse cyclic loading. The results show that this system can provide full recentering up to 3% drift with limited sustained damage at the rocking toes and limited energy dissipation capability. The rocking wall system can be designed as a robust LLRS but can be further improved by incorporating external energy dissipating elements into the system. To improve the system performance by including damping in the rocking wall system, o-connector and LiFS are used to connect two rocking walls. The coupled walls still provide the recentering while reduces the seismic displacement demand resulting from higher damping. Tests and finite element analysis of o-connectors were carried to understand its force-displacement behavior and energy dissipating capacity under reverse cyclic load. Design equations based on the test and FEA results are proposed. Laboratory tests were conducted on two CLT-LiFS hybrid walls in addition to component level tests on LiFS and CLT-LiFS connection. A load transfer mechanism in CLT-LiFS hybrid wall is proposed and used with a simplified calculation procedure to predict the force-displacement behavior of hybrid wall. The study shows that the analysis procedure predicts force capacity within 20% of the test results and can be conservatively used for practice. The test results show that the hybrid wall system has improved energy dissipation capacity while providing almost full recentering at 4% drift. The CLT building performance can be improved and the cost associated with LLRS may be reduced by taking into account the beneficial effect of non-rectangular shear walls (such as T-wall, I-wall). Non-rectangular walls can be achieved by connecting them at web-to-flange interface with high stiffness connections. Also, a high stiffness wall-to-foundation connection which can transfer the high base shear to foundation needs to be developed. Two connections, one for web-to-flange interface and another for wall-to-foundation interface, is developed by using grouted shear key incorporating ultra-high performance concrete and self-tapping screw. Laboratory tests on these two connection show that the connections have very high stiffness (4 times) compared to traditional bracket type ones and they have high strength as high as 3 to 4 times.
Experimental Investigation of Ultra-High-Performance Concrete Panels Under Tornado Impact Loads
(University of Alabama Libraries, 2021) Kniffin, Hannah Rose; Aaleti, Sriram; University of Alabama Tuscaloosa
Tornado events pose a threat to millions of people living in the tornadic-prone areas of the United States. Although many tornado shelters and safe rooms are commercially available that satisfy the extreme loading conditions required by the International Code Council and National Storm Shelter Association, there is a need for a simple yet safe design which can be easily assembled and used for multiple purposes. New engineering materials, such as ultra-highperformance concrete (UHPC), have the potential to improve tornado shelter options and save lives. This study experimentally investigates the performance of thin UHPC panels subjected to impact of standard wood 2x4 projectiles, following the requirements of ICC/NSSA 500, the leading standard on storm shelter design. 1.25-inch-thick and 1.625-inch-thick UHPC panels were cast and impacted with 15-lb wood projectiles at speeds ranging from 50 mph to 100 mph to maintain a similar impact-energy-to-panel-mass ratio. The failure response of each panel was characterized by excessive flexural deflection or punching shear. In the case of excessive deflection, a single-degree-of-freedom dynamic displacement model describes the motion of the panel during impact and the profile of the maximum deflection. In the case of punching shear, a modified equation from ACI 318 predicts the capacity of the panel. The results of the impact testing show UHPC is a promising material for future tornado shelters: UHPC panels with half the thickness of a traditional concrete shelter can be built for a similar or lower price, creatively integrated into homes, and increase accessibility of the tornado shelter for residents.
Hybrid structures using ultra high performance concrete and normal concrete for bridge applications
(University of Alabama Libraries, 2018) Ronanki, Vidya Sagar; Aaleti, Sriram; University of Alabama Tuscaloosa
The aging transportation infrastructure problem coupled with rapidly increasing traffic volumes and tightening budgets necessitates the need for cost effective and durable bridge components which can be easily implemented using current construction techniques. These solutions must also be suitable for accelerated construction in order to ensure minimum disruption to existing traffic. In this regard, Ultra High Performance Concrete (UHPC), a highly engineered cementitious material with enhanced mechanical properties lends its self as an ideal material. UHPC cost is nearly 30 times the traditional concrete, making full UHPC structures uneconomical. Through this multipart research, the emerging UHPC material and the traditional normal concrete are optimally combined to exploit both their beneficial features and yield new economical hybrid bridge components. The rebar development length in UHPC was experimentally investigated using pull out and beam specimens with lap splices. The results from these tests add significant new data on the bond stress distribution for rebar embedded in UHPC and a simplified design equation is proposed. An embedment length of 8 db (db -diameter of rebar) in UHPC with 3db clear cover was found to be sufficient to yield a Grade 60 mild steel reinforcement. A hybrid prestressed girder concept utilizing UHPC in the end zones of the girder with normal concrete in the remainder of the girder was proposed for a long-span girder with existing shapes . The endzone and shear behavior of a deep prestressed girder was investigated experimentally and analytically using four 78 in. deep, normal concrete bulb-tee (BT-78) girders. A detailed finite element (FE) model was developed in ABAQUS and calibrated using the experimental data. UHPC-NC interface behavior under direct shear and flexural loading was also experimentally investigated using direct shear testing of small-scale interface samples and flexural testing of UHPC-NC beams. A detailed finite element model for the interface was developed in ATENA and calibrated using the experimental results. Further, a detailed 3D FE model of a 205ft. long UHPC-NC hybrid girder was developed in ATENA and used to evaluate the feasibility of the hybrid girder concept. It was found that the hybrid girder concept is not only feasible but also reduces significantly the amount of end-zone reinforcement and end-zone cracking. A hybrid bridge pier system using a precast UHPC shell as permanent formwork for traditional bridge piers or as a retrofit option for existing columns was proposed. Experimental tests were conducted on 24in. long UHPC-NC columns to quantify the effectiveness of the UHPC shell in providing the confinement to normal concrete. Results obtained from the tests indicate that UHPC-shell-confined specimens exhibit a 15 to 30 % increase in peak load carrying capacity along with a 26 to 46% increase in failure strain values.
In-situ production of calcium carbonate nanoparticles in fresh concrete using pre-carbonation method
(University of Alabama Libraries, 2017) Qian, Xin; Wang, Jialai; University of Alabama Tuscaloosa
To reduce the carbon footprint of ordinary Portland cement (OPC)-based concrete, a novel technique, pre-carbonation process, has been developed to produce CaCO3 nanoparticles in fresh concrete. In this technique, gaseous CO2 is first absorbed into a slurry of calcium-rich minerals which is then blended with other ingredients to produce mortar/concrete. The objective of this work is to obtain an in-depth understanding of the underlying scientific mechanisms associated with the enhancement of strength and durability of the concrete induced by the new method. A comprehensive research plan has been carried out to study the carbonated slaked lime slurry and the effect of carbonated slaked lime slurry on the performance of OPC-based concrete, and to evaluate the potentials of the pre-carbonation method. Experimental studies show that carbonating the calcium-rich mineral slurry with CO2 can produce CaCO3 nanoparticles and Ca(HCO3)2 in the slurry, and these carbonation products were dictated by four parameters of the pre-carbonation method: the duration and temperature of the carbonation, the concentration of the calcium source slurry, and the stirring method of the calcium source slurry during the carbonation. The mechanical properties and durability of the mortar/concrete made with the carbonated slurry were significantly improved, which can be attributed to major mechanisms induced by the pre-carbonation method: promoted hydration of the cement and denser microstructure of the mortar/concrete. Calorimetry testing showed that the hydration of OPC was greatly improved by the pre-carbonation because of the extra heterogenous nucleation sites provided by the CaCO3 nanoparticles. XRD and TGA results revealed that more ettringite was produced in the mortar/concrete with pre-carbonated slaked lime slurry. The overall volume of the hydration products of the cement was increased by the pre-carbonation, leading to denser microstructure of the mortar/concrete. It has been found that the pre-carbonation can be used to the OPC-supplementary cementitious materials (SCMs) blended cement mortar/concrete, as evidenced by the improved mechanical properties achieved by these mortars produced by using the pre-carbonation method. A preliminary study was also conducted to examine whether other calcium-rich minerals, such as Class C fly ash and limestone, can be used as calcium source in the pre-carbonation method.
An investigation of the structural capacity of the Alabama Department of Transportation’s standard prestressed precast concrete piles
(University of Alabama Libraries, 2019) Gould, Emily; Aaleti, Sriram; University of Alabama Tuscaloosa
Prestressed precast concrete piles (PPCPs) are commonly used in bridge foundations throughout the southeastern United States. The Alabama Department of Transportation (ALDOT) particularly uses them in the coastal regions in non-cohesive soils and where corrosion would be expected from salt or brackish water. ALDOT’s currently listed pile design capacities in their structural design manual (SDM) were found to be lower than those for similar PPCP pile sizes used in surrounding states. This prompted the question as to why these values were lower, and whether they could safely be increased. A joint research project involving researchers from the University of Alabama and the University of South Alabama set out to answer this question, considering the structural and geotechnical implications respectively. This thesis particularly investigates the structural capacity of ALDOTs PPCPs through a series of tasks. First, an in-depth review of the practices of surrounding DOTs was conducted, evaluating how ALDOT’s practices are similar and where they diverge, to arrive at plausible explanations for ALDOT’s current standard capacities. Next, a simple analysis program was developed using Microsoft Excel, to calculate the combined axial and moment capacities of the standard ALDOT piles. Following this, to evaluate the expected demand on pile bents using the current bridge loading (HL-93), three prototype bridges were modeled and analyzed using standard structural analysis software. Using the analysis, the demand on pile bents under different load combinations were estimated and compared with the previously determined capacities. Based on this analysis, the listed structural capacities of ALDOT’s standard PPCPs could be increased.
Low-cost, ubiquitous biomolecule as next generation, sustainable admixture to enhance the performance of ordinary portland cement-based concretes
(University of Alabama Libraries, 2021) Fang, Yi; Wang, Jialai; University of Alabama Tuscaloosa
The production of ordinary Portland cement (OPC) is highly energy-intensive and responsible for approximately 6% of anthropogenic greenhouse gas emissions. To reduce the carbon footprint of OPC based concrete, this research proposes to use a low-cost, ubiquitous, naturally occurring compound, tannic acid (TA) as a small-dose additive to significantly enhance the strength of OPC based concrete.This study is inspired by biosystems’ protein-based materials, which generally exhibit superior strength and toughness owing to their hierarchical structures via hydrogen-bonding assembly. With abundant reactive terminal phenolic hydroxyl groups, TA has an ability to complex or cross-link macromolecules sites through multiple interactions. Thus, TA can be used to complex or cross-link hydration products of cement at multi-binding sites so that the strength and durability of concrete can be significantly improved. A comprehensive research plan has been carried out to evaluate the potential of TA on performance enhancement of OPC-based concrete, understand how TA modifies the hydration of cement, mitigate the retardation of TA on cement’s hydration, and evaluate application potentials in concretes with SCMs. Experimental studies show that TA can strongly retard the hydration of cement and alite due to its ability to bind to various particles and chelate with calcium ions, causing less calcium hydroxide produced by the hydration. The strong interaction between the TA and hydration products leads to morphology change of the hydration products and generates nanoparticles at early age. Furthermore, addition of TA can significantly densify the nanostructure of cement pastes. Particularly, capillary pores smaller than 70nm are drastically reduced by TA. This finding is not only explaining why TA can enhance the micromechanical properties of concrete, but also opening a new approach to tune the nanoscale pores in concrete. Besides, a pre-hydration method is proposed and verified to mitigate the retarding effect of TA for widely adopted in practical application. Significant strength improvement at late age can be achieved by pre-hydration with TA without losing of strength at early age. TA is also successfully used in mortars with silica fume to achieve over 30% strength improvement, suggesting its huge potential to reduce the carbon footprint of concrete.
Modeling of CLT creep behavior and real-time hybrid simulation of a CLT-LiFS building
(University of Alabama Libraries, 2017) Nguyen, Tu T.; Dao, Thang N.; Kenneth, Fridley J.; University of Alabama Tuscaloosa
CLT-LiFS is an innovative hybrid structural system. This type of structure has emerged as a promising structural system for mid-rise to tall wood buildings in the seismic areas. CLT-LiFS is made by integrating post-tensioned Cross Laminated Timber (CLT) panels with Light Frame Wood Systems (LiFS). The post-tensioned CLT panels can provide excellent load bearing and self-centering capacity. And the LiFS can dissipate a large amount of energy through the slip of fasteners when it deforms. The behaviors of CLT-LiFS have been studied through a series of experimental tests under cyclic loading protocols and earthquake motions at different hazard levels using real-time hybrid simulations. Results from the experimental tests showed that the CLT-LiFS performed well under MCE (Maximum Considered Earthquake) hazard level with the maximum drift less than 1%. To obtain a good self-centering performance, the post-tensioned tendon force in CLT panels needs to be maintained at a desired level in long-term until the earthquake hits. Under the creep behavior, the post-tensioned force in the tendon will reduce as a function of time and moisture content in CLT panels. In this dissertation, a moisture content diffusion model was introduced by applying Fick’s law to estimate the moisture content migration in CLT panels under the variation of environmental relative humidity. A numerical model combined with data from a series of moisture content experiments were used to obtain the moisture content diffusion coefficients for CLT material. The four-element creep model was also proposed. This creep model could predict the creep deformation of CLT panels versus time under variations of ambient environmental conditions. A 3D finite element model (FEM) was developed with an integration of the creep and moisture content diffusion model to predict the tendon force of post-tensioned CLT panels versus time. This FEM model was used to predict the loss of tendon force in CLT panels. This tendon force loss did not include the instant loss at the beginning due to anchor slip or other factors.
Optimal discrete-time compensation design for real-time hybrid simulation
(University of Alabama Libraries, 2017) Hayati, Saeid; Song, Wei; University of Alabama Tuscaloosa
Real-Time Hybrid Simulation (RTHS) is a powerful and cost-effective dynamic experimental technique. In civil engineering, RTHS has the advantage of investigating the dynamic behavior of full-scale and complex structures by testing only the critical components. To implement a stable and accurate RTHS, the time delay in the experiment loop needs to be compensated. This delay is mostly introduced by servo-hydraulic actuator dynamics and can be reduced by applying appropriate compensators. Several existing compensators have demonstrated effective performance in reducing the actuator time delay. But most of them have been applied only in cases where the structure under investigation is subjected to inputs with relatively low-frequency content such as earthquake motion. To make RTHS an attractive technique for engineering applications with broader excitation frequency, a discrete-time feedforward compensator is developed via various optimization techniques to enhance the performance of RTHS. The effectiveness of the proposed compensator is demonstrated through both numerical and experimental studies. The proposed compensators are successfully applied to RTHS tests to study the seismic behavior of a linear-elastic reinforced concrete building equipped with a new type of tuned mass damper, known as the Disruptive Tuned Mass (DTM) damper designed by the National Aeronautics and Space Administration (NASA). The obtained results show that the proposed compensator reduces the time delay adequately and leads to a successful RTHS test. Results also suggest that the DTM damper can successfully reduce the response of the building subjected to the seismic loads. In addition, the dynamic properties of the DTM damper are fully investigated and a mathematical model is suggested for it.
Synthesis and characterization of geopolymers using locally available fly ashes
(University of Alabama Libraries, 2014) Zeng, Shixin; Wang, Jialai; University of Alabama Tuscaloosa
Geopolymer can be synthesized using industrial wastes such as fly ash, making it a promising material to replace Ordinary Portland Cement (OPC) as a green binder for concretes. In this study, four locally available fly ashes were used to synthesize geopolymers. These fly ashes were carefully selected to include both the high calcium and low calcium fly ashes. Two of the fly ashes have very similar chemical compositions. Comprehensive experimental programs have been carried out to characterize these fly ashes, to examine the critical factors affecting the mechanical properties of geopolymers, and to evaluate the potentials of these fly ashes as source materials for geopolymers. Testing results show all these fly ashes can be used to synthesize geopolymer. Among them, the fly ash from Gaston was found to be the most suitable source material for geopolymer. Fracture behavior of the produced geopolymer mortar was studied using splitting wedge testing together with digital image correlation technique. The measured full-field displacement clearly shows that a fracture process zone (FPZ) exists ahead of the major crack, suggesting that the fracture of the geopolymer mortar follows a nonlinear behavior. The bi-linear constitutive law of the FPZ was then obtained three an inverse analysis. To gain insight into the geopolymerization process, the electrical properties of the produced geopolymers were measured. It has been found that both the magnitude of the electric impedance or the electric resistance can be used as an indicator of the degree of geopolymerization. The bulk resistance of all geopolymers increases with age over one year, suggesting that the polymerization is a very long process. Finally, to explore the possibility to reinforce the brittle matrix such as geopolymer with Carbon Nanotubes, a model of shear force transfer from CNTs to the matrix is developed to understand and optimize the reinforcing effect of CNTs.

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