Center for Built Environment Research
School of Planning, Architecture and Civil Engineering

Advanced Structural Materials

PhD Projects offered under Advanced Structural Materials

 

ASM1: Integration of real-time monitoring and modelling techniques for the optimisation of precast concrete production process for marine applications

Supervisors: Prof M Soutsos, Dr S Nanukuttan

Funding Possibility: International Studentship/DEL Formula Studentship

 

Concrete is the second largest used commodity in the world after water. The environmental impact attached to the concrete production is substantially high and results in at least 5% of the total world carbon footprint. Despite the large demand, the industry is currently going through a challenging period with profit margins ranging from 1- 6% of the production cost. Winter season brings further challenge to the production process with plummeting temperatures resulting in slow strength development and increased processing time. In order to overcome this problem, producers often (1) increase the cement quantity, (2) add chemical admixtures and (3) subject the products to high temperature curing for longer periods. All these measures further increase the environmental impact whilst reducing the profit margin. It is well established that the temperature history of concrete, especially during its early age curing process, can be related to its strength development. Sophisticated models can be used to predict the temperature profile in a structural element, i.e. the strength differences that may exist between the core and outer surface concrete. Monitoring the temperature history of concrete and relating it to concrete compressive strength can help to optimise not only the temperature assisted curing time but also the cement content and type and amount of chemical admixtures needed to achieve to required minimum compressive strength for stripping/demoulding the next day. Furthermore, the technology can be adapted to forecast changes to the mixes needed to counteract adverse effects from weather forecasts. Using targeted monitoring and modelling techniques it is therefore possible to optimise the production process. This project will benefit from the expertise at the Centre for Built Environment Research in concrete technology, distributed sensing and temperature based strength prediction. The project will be supported by one of the leading precast concrete manufacturer Creagh Concrete Products Limited. The potential impact of project includes 6-10% reduction in the carbon footprint and increased profit margins up to 10%.

 

ASM2: Carbon Dioxide Sequestration Technology for Manufacturing Engineered Cement Matrix for Resisting Severe Exposure Environments (CARBON-ECEM)

Supervisors: Professor M Basheer, Dr D McPolin and Dr. T McNally (SMASE)

Funding Possibility: Strategic Studentship/DEL Formula Studentship

 

Concrete is the second largest used material in the world today after water, and Portland cement is the largest used cementitious material in concrete. The world cement production for 2010 was nearly 3.3Bt, with China responsible for more than 56% (1.868Bt) and the 27 EU member states accounting for approximately 6% (190.4 million tonne) of the global volume. This accounts for 2.74Bt of CO2 released to the atmosphere (~830kg CO2 per tonne of Portland cement). Therefore, in the past number of years the EU has introduced a body of legislation, policy guidance and targets aimed at significantly reducing the carbon footprint of construction. There are two goals for the CARBON-ECEM project; one is to develop engineered cement matrix so as to reduce the consumption of Portland cement; and the other is to develop an effective CO2 sequestration technology so as to reduce the release of CO2 to the atmosphere. The CARBON-ECEM project will achieve these two goals simultaneously by developing a novel CO2 utilisation technology, in which CO2 will modify the microstructure of the cement matrix and will result in improved engineering properties and reduced use of Portland cement. This novel CO2 technology comprises utilisation of CO2 during the manufacture of cementitious materials, such as concrete, or a delayed release of CO2 immediately after manufacturing concrete, and the anticipated benefit in reducing global release of CO2 from cement plants is 0.412Bt. A multidisciplinary approach encompassing material science, cement chemistry, sensor development and modelling will be applied to develop the technology. Unlike other newly available approaches to reduce the use of Portland cement, this technology does not require a change of current Codes of Practice, making both the technology transfer and impact realisation fast.

 

ASM3: Development of stainable drainage system using pervious concrete pavements to reduce risk of flooding

Supervisors: Dr M. Sonebi, Dr. D Hughes (EERC), and Dr Alastair Ruffell (GAP)

Funding Possibility: DEL Formula Studentship

 

Pervious (permeable) concrete is a special type of concrete characterized by a connected pore structure and high void content.  It is advantageous for in-situ drainage, thermal insulation and acoustic absorption.  It can be used in a wide range of construction applications such as pavements for parking lots, base course for roads/airports, bridge embankments.  Up till now, there is no fundamental knowledge on the mixture design and mechanical, acoustic, thermal and durability properties of pervious concrete.  These data are needed to develop thorough specifications (guidelines) for pervious concrete.  Hence, this project will review the current state of knowledge on the mixture design and properties of pervious concrete.  The gathered information will then be used to investigate the engineering performance of pervious concrete and investigate the effect the nature of surface on the durability and acoustic absorption of pervious concrete and related to the microstructure of the matrix.  This investigation will study the permeability of the system affected by freezing conditions, the impact on the local groundwater table, and what level of pollutant removal can be expected from the system. This research will investigate also the exfiltration from several selected pervious concrete plots to be constructed on a compacted clay soil and several types of treatments were applied to the clay soil prior to placement of the stone aggregate base and pervious concrete in an attempt to determine the exfiltration rate, including: 1) control – no treatment; 2) trenched – soil trenched and backfilled with stone aggregate; 3) ripped – soil ripped with a subsoiler; and 4) boreholes – placement of shallow boreholes backfilled with sand.  The internal temperature of the pervious concrete and aggregate base will be monitored in order to look at the freezing concrete temperatures related to the free water being present in the large pervious concrete pores.

 

ASM4: Investigation of engineering performance of engineered cementitious composites (ECC)

Supervisors: Dr M. Sonebi and Prof. M. Lachemi (Ryerson University-Canada)

Funding Possibility: DEL Formula Studentship

 

Engineered cementitious composites (ECC) are a type of high performance, ultra-high ductility fibre reinforced composite developed at the University of Michigan. ECC typically consists of cement, sand, fibres, chemical admixtures such as HRWR and potentially mineral admixtures, with the coarse aggregate content omitted to aid fibre dispersion. In contrast to tension-softening of conventional fibre-reinforced composites (FRC), ECC exhibits a strain-hardening behavior (whereby significant micro-cracking occurs to enable further increases in load capacity.  The benefits of ECC are not limited to mechanical properties, indicating aforementioned micro-cracking within ECC to exhibit a water permeability equal to sound concrete, thereby highlighting durability benefits.  Potential ECC applications include infrastructure elements, e.g. bridge decks or airport runways which benefit from increased toughness, and structures in seismic areas benefitting from the strain-hardening behavior. While much research has been provided upon the influence of independent variables on ECC, a significant lack of research exists with regard to the fresh properties, rheology, mechanical properties and plastic shrinkage and the durability of ECC.  The aim of this study is to investigate the various parameters of mix composition affecting the fresh properties, rheology, mechanical properties and plastic shrinkage and drying shrinkage, and the durability of ECC. 

 

ASM5: Durability of precast concrete made with self-compacting concrete (SCC) with different supplementary materials

Supervisor: Dr M. Sonebi

Funding Possibility: DEL Formula Studentship

 

The introduction of SCC into general concrete construction can be considered as the most significant advance in concrete technology for decades.  SCC is highly flowable, non-segregating concrete that can spread into place, fill the formwork, and encapsulate the reinforcement without any mechanical compaction.  SCC has been successfully used in many projects around the world and it has made a major impact on concrete placement, and construction economics.  These characteristics translate into a substantial reduction in labour cost and construction time, and a better working environment by eliminating the impact of vibration, using waste materials, reducing carbon foot print and energy consumption.   The aim of the project is investigate the effect of mix composition include the supplementary materials (such as GGBS, fly ash, silica fume, metakaolin), fillers and waste materials on the durability properties of SCC (chloride migration, sulfate attack, frost thawing, carbonation, chemical resistance to acid attack and seawater) and compare to vibrated traditional concrete. 

 

ASM6: Modelling the effect of curing temperature on the early age strength development of pozzolanic concretes

Supervisor: Dr. S. Nanukuttan , Prof. MN Soutsos, and, Dr. J. Lim

Funding Possibility: DEL Formula Studentship/InvestNI Proof of Concept

 

The use of ground granulated blast furnace slag (ggbs) and pulverised fuel ash (pfa) and ternary systems with condensed silica fume (csf) in concrete although economic has not gained popularity in fast track construction or precast concrete factory production because of the slower strength gain of these mixes at standard curing temperatures. There are however indications that ggbs and pfa are heavily penalised by the standard curing regimes. The high early age temperatures occurring inside structural elements appear to provide the activation energy needed for the pozzolanic reaction to "kick-in" earlier. This results in in-situ/air-cured or standard cured strength ratios of 2.0 to 2.4 as compared to ratios of 1.0 to 1.4 for ordinary Portland cement concrete mixes. The main aim of this project will be to investigate the early age strength development of ggbs, pfa, ggbs/csf and pfa/csf composite cements under simulated in-situ temperature histories in order to give guidance for their use in fast track construction and precast concrete factory production. It is important that techniques for monitoring the strength development on site, e.g., maturity measurements, are validated for these composite cements. This work would involve theoretical studies, computer modelling and laboratory experimental studies.

 

ASM7: Reactive Powder Concretes for Bridge Structures

Supervisor: Prof. MN Soutsos, Dr. D Robinson and Dr. D. Hester

Funding Possibility: DEL Formula Studentship/InvestNI Proof of Concept

 

Reactive Powder Concretes (RPCs) have been developed which have enhanced homogeneity, enhanced microstructure, and enhanced ductility. The inclusion of fibres improves tensile strength, and also makes it possible to obtain the required level of ductility. The compressive strengths of RPCs with-out application of pressure before and during setting are likely to be between 170 to 230 MPa depending on the post-set heat treatment (20 to 900C). Values for flexural strengths are likely to be between 30 and 60 MPa, fracture energies between 20,000 and 40,000 J.m-2 and moduli of elasticity between 50 to 60 GPa. RPC appears to be a promising new material not only because of its enhanced ductility but also because the mixing and casting procedures are no different to existing procedures for normal and high strength concretes. RPC has, however, a substantial increase in cost over and above that of conventional and even High Performance Concrete and it is therefore appropriate to identify applications which fully utilize RPC's mechanical properties and performance characteristics. Research therefore needs to be conducted to develop and commercialize types of precast products which utilize many of the enhanced properties of RPC. The main application of RPC up till now has been in the construction of prestressed structures without any secondary steel reinforcement. The Sherbrooke Footbridge was the first structure to be built with RPC. The use of RPC in structures comes up against the lack of design rules allowing full advantage to be taken of the improved mechanical characteristics of the material and of its ability to be used without passive reinforcement. This project will investigate the use of RPC for precast prestressed concrete beams that can be used for the construction of bridges. Optimisation of cross section of bridge girders with RPC to take full advantage of the enhanced properties of RPC will be undertaken. Finite Element Analysis modelling will be used to optimise the cross section of the bridge and also investigate the need or otherwise of secondary/passive reinforcement. Development of computer simulation programs that will be able to provide accurate predictions of the behaviour of RPC will require experimentally determined mechanical properties and possibly a new constitutive law for this new material to take into account its non-linear behaviour. Complete design of a bridge structure will be needed to establish the advantages of RPC for this use. For this to be achieved there will need to be a comparison with an "ordinary" bridge. This research involves several disciplines and can lead to good publications and practical recommendations when well conducted

 

ASM8: Microstructural Analysis of Cementless “Geopolymer” Concrete

Supervisor: Prof. Wei Sha, Prof. Marios Soutsos and Prof. PAM Basheer

Funding Possibility: DEL Formula Studentship/EU FP7

 

The project aims to provide key evidence for understanding what microstructure develops in cementless "geopolymer" materials of different sources which have different chemical and mineral compositions. This could allow blending of different materials so they produce geopolymer concretes with the desired engineering properties such as greater compressive strength, greater tensile strength, and greater flexibility.

 

ASM9: Impact Resistance of reactive powder concrete (RPC)

Supervisor: Dr. D Robinson, Prof. MN Soutsos, and, Dr. J. Lim

Funding Possibility: DEL Formula Studentship

 

Ultra high performance fibre reinforced concretes (UHPFRCs) which have been developed in an attempt to improve the mechanical performance of cementitious materials, especially strength and ductility under tension. The compressive strengths of Reactive Powder Concrete, one type of UHPFRC, are likely to be between 170 to 230 MPa depending on the post-set heat treatment (20 to 900C). Values for flexural strengths are likely to be between 30 and 60 MPa, fracture energies between 20,000 and 40,000 J.m-2 and moduli of elasticity between 50 to 60 Gpa. RPC appears to be a promising new material not only because of its enhanced ductility but also because the mixing and casting procedures are no different to existing procedures for normal and high strength concretes. The project will aim to supplement and develop existing expertise and data available to the supervisors to permit reliable estimation of the behaviour of RPC under impact and explosion loading conditions. This will make use of state-of-the-art equipment, computer modelling techniques and software. Specific objectives include:

  • Experimentally determine the mechanical properties, compressive and flexural strengths, fracture energies, moduli of elasticity, of RPC to provide accurate input data for the computer programs.
  • Numerically and experimentally investigate the impact load resistance of RPC, with different reinforcement details.
  • Develop guidelines for the design and detailing of RPC elements to resist impact and explosion loads.
  • Develop computer simulation programs that will be able to provide accurate predictions of the behaviour of RPC under impact and explosion loading.

The Abaqus finite element analysis package will be used to undertake the computer simulation of the impact.  The package will be used to perform an explicit transient dynamics analysis of the impact.  The non-linear plasticity models available within the package will be used to capture the material characteristics of the UHPFRC material.

 

ASM10: Crack-inducing thermal stresses in safety-critical concrete structures

Supervisor: Dr. J. Lim, Prof. MN Soutsos, and, Dr. D Robinson

Funding Possibility: DEL Formula Studentship

 

Thermal cracking in the structural concrete of foundations, bridges, tunnel linings and other medium-sized elements has become an increasing problem in the past decades. Previous methods of predicting thermal cracking and stresses in concrete structures have until now relied entirely on empirical knowledge of previous construction. Now, with the advent of powerful computer processing capabilities, it is proposed that a more rigorous and theoretically valid approach needs to be adopted. Equipment will be developed together with practical experimental procedures for determining the heat of hydration and early age mechanical properties of concrete specimens undergoing the same temperature cycles as they would in a real structure. These will comprise the increasing compressive and tensile strength, the increase of stiffness and the decrease of relaxation capacity, the coefficient of thermal expansion and the influence of chemical reactions on the deformation. These properties can then be used in conjunction with numerical modelling techniques to look at the many ramifications of the heat problem. This will include the effects of concrete strength, i.e. normal and high, binder type and content, size of structural element, casting and ambient temperatures, formwork type and time of removal on the maximum temperature rise and magnitude of the thermal stresses. The finite element program LUSAS will initially be used as it includes a concrete model with analytical capabilities for modelling concrete cracking and crushing that can model concrete characteristic behaviour. This can be coupled with a concrete heat of hydration facility in LUSAS, validated previously against standalone commercial heat of hydration programs. A combination of these capabilities will permit the structural performance of a variety of structures to be assessed, and their sensitivity to different temperatures and degree of hydration (which can be input into LUSAS).

 

ASM 11: Molecular Dynamics Modelling of FRP-Concrete Bond Durability

Supervisors: Prof. JF Chen, Prof. Muhammed Basheer and Prof. Oral Buyukozturk (MIT) 

Funding Possibility: DEL Formula Studentship

Externally bonded advanced fibre reinforced polymer (FRP) composites has become a popular technique for strengthening concrete structures, not only in the research community but also in engineering practice worldwide. This is largely due to the superior properties of FRP composites such as their high strength- and stiffness-to-weight ratios and excellent durability. One of the major challenges remains for the wider application of the technique is the prediction of the long term behaviour of the FRP-to-concrete bond under different environmental conditions. Limited existing research has been mostly experimental and empirical. This project aims to develop a new method for investigating the fundamental behaviour at nano-scale using the molecular dynamics (MD) modelling approach. The long term aim is to develop a robust methodology for the accurate prediction of the bond behaviour under different environmental conditions (e.g. moisture movement, temperature variation, and alkali and acid environments). If successful, the methodology would have a major impact in understanding the life cycle performance of structures and thus help to achieve more sustainable design of structures. This is a truly multi-disciplinary research project to be supervised by a team with internationally leading expertise in FRP strengthening, durability of concrete and MD modelling from leadingUKand US universities. Candidates with background in Engineering, Chemistry and Physics are encouraged to apply.