Ebook: Construction Materials and Structures

The first International Conference on Construction Materials and Structures (ICCMATS2014) was held in Johannesburg, South Africa from 24–26 November 2014. The event was locally considered to be a major onset for promotion and stimulation of research and engineering applications in the fields of materials and their structural implications on physical infrastructure. The core value of the conference was embedded on science and engineering as a necessary vehicle for addressing infrastructure needs and related modern socio-economic concerns, of the global community. The event also served to strengthen existing relationships and to establish new directions between South Africa as a country and research leader in the African continent, and other countries within and outside the continent including Europe, China, North America, to mention but a few.

The Proceedings of this conference contain about two hundred peer-reviewed papers from fifty-one countries, making this a truly international event. They include ten keynote speeches by some of the leading academics, researchers and international experts from Canada, USA, Turkey, United Kingdom, Uganda, New Zealand, South Africa, Qatar, and Japan.

The geographical location and timing of this event demanded special consideration on issues of developing countries where the severe lack of a critical mass of academics, research scientists and engineers undermines efforts to attain sustainable development. In developing countries, the fast population growth promotes rapid urbanization; resulting in high poverty and mortality, aggravation of poor housing conditions, disproportionately high energy demands and environmental degradation due to human activity, among other social ills. Besides these negative issues, most of these countries are on a significant economic growth trajectory, but remain in dire need for impactful and sustainable physical infrastructure. In an attempt to confront these concerns, the International Conference on Construction Materials and Structures was organized to bring together international experts from several countries to discuss scientific research and share advances in technology. Against this backdrop, ICCMATS 2014 was used as a platform for sharing of cutting-edge theories, techniques and scientific advances by some of the foremost scientists and researchers worldwide. The event provided insights for addressing issues of modern local infrastructure, and inspired future advancements, innovations and emerging researchers.

Consistent with the technical focus of the conference, high quality papers presented in these Proceedings covered a range of fields, categorized into nine (9) sub-topics and five (5) main themes viz. materials and characterization, durability of construction materials, structural implications and service life, sustainability and the environment, building science and construction. All the papers that were submitted for ICCMATS 2014 were fully peer-reviewed, a task undertaken by the International Scientific Committee (ISC). The acceptance of the papers for publishing in these Proceedings was based on the recommendations provided in the reviewer reports. Sincere gratitude is due to the individual members of the ISC and all reviewers for their important contribution of ensuring the high quality of these Proceedings.

The following organizations are gratefully acknowledged for their significant financial and technical support to the conference: The National Research Foundation of South Africa, Council of Geoscience (South Africa), Concrete Society of Southern Africa Johannesburg Convention Bureau, The American Concrete Institute and RILEM.

On behalf of the Organising Committee, the Editors of the Proceedings wish to extend special thanks to all authors for the technical contribution of their high quality research, expertise and knowledge through these Proceedings. In addition, the dilemmas of resource planning for participation in the conference, placed high demands on the authors; for which collective applause is in order for all authors who participated in the event.

Finally, thanks are due to all members of the Conference Organizing Committee, the Conference Secretarial team, the Dean of the Faculty of Engineering and the Built Environment at the University of Johannesburg (UJ), academic and technical staff of the UJ Department of Civil Engineering Science, partners from Harbin Institute of Technology, research students and all those who contributed to the running and success of the event. It was a rewarding programme to all those involved, not excluding the wider scientific community. In that regard, this event's continuity into the future is anticipated.

Editors:

Stephen O. Ekolu

Morgan Dundu

Xiaojian Gao

Obtaining durability for a known service life in chloride exposures requires knowledge of the concrete properties, relevant transport processes, depth of cover as well as minimization of cracking and construction defects. For example, imperfect curing can result in depth-dependent effects on resistance to chloride ingress. Several service life models with various levels of sophistication exist for prediction of time-to-corrosion of concrete structures exposed to chlorides. The model inputs have uncertainty associated with them such as boundary conditions (level of saturation and temperature), cover depths, diffusion coefficients, time-dependent changes, and rates of buildup of chlorides at the surface. The performance test methods used to obtain predictive model inputs as well as how models handle these properties have a dramatic impact on predicted service lives. Very few models deal with the influence of cracks or the fact that concrete in the cover zone will almost certainly have a higher diffusion coefficient than the bulk concrete as the result of imperfect curing or compaction. While many models account for variability in input properties, they will never be able to account for extremes in construction defects. Therefore, to ensure the reliability of service life predictions and to attain a concrete structure that achieves its predicted potential, designers, contractors and suppliers need to work together to ensure proper detailing, minimize defects, and adopt adequate, yet achievable, curing procedures. As well, concrete structures are often exposed to other destructive elements in addition to chlorides (eg frost, ASR) and this adds another level of complexity since regardless of cause, cracks will accelerate the ingress of chlorides. These issues are discussed along with the need to use performance-based specifications together with predictive models.

Research and applications of nanoparticles in concrete materials are rapidly increasing because fundamental properties of concrete (such as rheology, strength, transport properties, fracture behavior, etc.) are strongly influenced by the material properties at the nanoscale. Use of nanomaterials in concrete can also enhance sustainability and reduce negative environmental impact through reduction in cement use, energy and natural material consumptions during production and service. In this paper, the needs and opportunities of use of nanoparticle modified concrete are highlighted. The challenges in nanoparticle processing (such as dispersion and stabilization) are addressed. Recent developments in characterization methods (such as Raman spectroscopy, nanoindentation, modulus mapping, peak-force quantitative nanomechanical mapping and atomic force microscopy) are reviewed. Effects of nanoparticles (such as nanosilica, nanolimestone and nanoclay) on concrete rheology, hydration, microstructure development, mechanical properties, and durability are discussed.

In current seismic design, structures are typically assumed to be fixed at the base. Separation at the base during earthquakes is thus avoided, in order to avoid the possibility instability or even overturning. In contrast to this conventional approach, the structures described in this paper subscribe to a low-damage design philosophy in which the structures are indeed allowed to move and uplift while responding to earthquake loading. Whenever there is partial separation of the structure from the supporting ground, earthquake energy induced into the structure will be temporarily cut off. Consequently, the structures experience less loading and less or even zero damage can be anticipated. This paper presents an overview of current research on innovative seismic design approaches that could be implemented in low-damage earthquake-resistant structures of the future.

Severe plastic deformation emerged as new processing to fabricate ultrafine grain metallic materials with a grain size under one micron meter, or nanocrytalline metals in a bulk form. It was found that such ultrafine grain (UFG) and nanocrystalline metals have superior mechanical properties with high strength and relatively high ductility as well as corrosion properties. On the other hand, they also exhibit unique mechanical, physical and thermal properties ascribing to large fraction of grain boundaries and triple junctions, which may reach to more than 50 %. In this paper, equal-channel angular pressing (ECAP) and mechanical, corrosion and thermal properties of UFG Fe-20%Cr steel fabricated by ECAP are presented.

Thermal stress development in concrete structures is significantly influenced by the coefficient of thermal expansion (CTE) of concrete. Optimizing concrete CTE can reduce the thermal stress, which will eventually reduce the cracking potential of concrete structures. At early age, when concrete has low strength, it is much more vulnerable to cracking. Early-age cracking has a detrimental effect on the durability of concrete structures. This study presents the importance of concrete CTE on the thermal stress development in concrete structures as well as three techniques to reduce the CTE of concrete. Replacing high CTE coarse aggregates with low CTE coarse aggregates is the most effective method for reducing concrete CTE. Concrete CTE can also be reduced by reducing cement paste volume. However, if the cement paste reduction increases the void content in the concrete system, saturated concrete CTE is likely to increase.

In an attempt to address future construction requirements a clear focus is necessary on development of new technologies addressing the need for safer and more cost-effective infrastructure. The paper aims to summarise the current state-of-the-art on application of superabsorbent polymers (SAP) in cementitious composites as internal curing agents. The effect of SAP type, cement type and fly ash content on performance of cement mortars is briefly discussed. The importance of adequate selection of SAP with water absorption/desorption characteristics compatible with hydration process is highlighted.

In this paper, a summary of analytical and experimental studies into the behavior of a new hysteretic damper, designed for seismic protection of structures is presented. The Multi-directional Torsional Hysteretic Damper (MTHD) is a recently-patented invention in which a symmetrical arrangement of identical cylindrical steel cores is so configured as to yield in torsion while the structure experiences planar movements due to earthquake shakings. The new device has certain desirable properties. Notably, it is characterized by a variable and controllable-via-design post-elastic stiffness. The mentioned property is a result of MTHD's kinematic configuration which produces this geometric hardening, rather than being a secondary large-displacement effect. Additionally, the new system is capable of reaching high force and displacement capacities, shows high levels of damping, and very stable cyclic response. The device has gone through many stages of design refinement, multiple prototype verification tests and development of design guidelines and computer codes to facilitate its implementation in practice. Practicality of the new device, as offspring of an academic sphere, is assured through extensive collaboration with industry in its final design stages, prototyping and verification test programs. Analytical and experimental progress made so far in this on-going research is summarized in this paper.

Despite the relatively well-established concrete practice in the East African region, there are frequent incidents of construction failures, resulting into heavy loss of lives and property. The main objective of this paper was to examine structures that have failed during the construction phase, in East Africa, since the start of the 21^st century; identify and discuss the primary causes and sources of failures. A classic failure case of building collapse, herein referred to as BBJ building, has been used to examine the most important issues related to construction failures. Following the analysis of reports of technical investigations undertaken on the collapsed structure, it was found that failures in reinforced concrete (RC) structures during construction, result from five primary causes of: (1) poor materials and workmanship, (2) design and construction errors, (3) absence of professional supervision of site-works, (4) wrong implementation of construction methods, (5) neglect of design approval procedures. Secondary issues that are complicit to construction failures are:- attempts to severely minimize construction cost, neglect of inspection and monitoring by local authorities, influence peddling by proprietors. It is evident that construction failures can be minimized if the right procedures are followed in the design, construction and operation of the structures; a matter that is of interest to stakeholders of the Built Environment.

Ultra high performance concrete (UHPC) is a a composite material that consists of Portland cement, silica fume, ultra-fine quartz powder, superplasticizer and small sized steel fibers with low water to binder ratio and absence of coarse aggregates. Compared to conventional concrete, UHPC has superior properties such as strength, toughness and durability. In this paper, the principles for mixture design and properties including mechanical properties, dimensional stability and durability of UHPC were reviewed.

Various wastes and by-product materials are generated in the Middle East including reclaimed asphalt pavement (RAP) aggregate, demolition concrete, excavation waste, steel and aluminum slags, cement by-pass dust (CBPD), copper slag, petroleum-contaminated soils (PCS), waste tires, incinerator ash, and others. Recycling of such materials for road construction is not practiced. Research data and field studies on the potential use of selected materials in road construction applications are limited. This paper presents an overview of the different waste materials generated in many countries in the Middle East, their potential applications in road construction and the impediments to recycling initiatives. Representative results of several laboratory studies on the use of PCS in asphalt concrete mixtures; the utilization of CBPD in soil stabilization; and the recycling of RAP aggregates in road bases and sub-bases will be presented. The Laboratory data indicated that it is feasible to partially reuse some of these materials in road construction provided that economic incentives and environmental concerns are taken into consideration.

High alumina cements are widely used in refractory industry, mainly for the manufacture of refractory concrete. It is known fact that from the components of refractory concrete, high alumina cement is the fondant component of the system due to the lower melting point of the mineralogical compounds contained, compare to the refractory aggregates used. To improve the behaviour at high temperature of high alumina cement, we will try to obtain high alumina cements based on calcium-aluminates compounds with higher refractory toward the usual high alumina cement based on monocalcium monoaluminate and dicalcium monoaluminate. However, because with the improvement of refractoriness of calcium-aluminates compounds form high alumina cement, the hydraulically properties decrees, we will try to increase the hydraulically properties with an accelerator additive, such as calcium sulphoaluminate. This paper aims to present the structural and mechanical behaviour of high alumina additivated cement based on high mineralogical refractory compounds such as dicalcium monoaluminate and monocalcium hexa aluminate in comparison with the usual high alumina cement, at normal temperature and after treatment at high temperature heat, too.

This paper investigated the suitability of the use of borrow pit sand locally known as Obimo sand in structural concrete. The physical properties of the unwashed Obimo sand (UOS) and the washed Obimo sand (WOS) were first investigated and compared to those of the conventional river sand (RS). Concrete cubes made from the three samples (UOS, WOS and RS) were crushed for their compressive strength. It was found out that the specimens fall within the acceptable limits of fine aggregates for structural concrete works given in both IS: 383 – 1970 and BS 882: 1973. The chemical composition obtained by elemental analysis using X-ray florescence spectrometry proved Obimo sand samples free of sulfate and saline contents. Also the concrete made from the WOS gave 6.5% more strength than that made from RS at 28 days age, while the UOS produced a concrete of slightly lower compressive strength. Specifically, the compressive strength ranged from 29.5 to 33 N/mm² for the alternative Obimo sand. Conclusively, a cost analysis carried out showed a reduction of 1.42% and 0.43% for the WOS and UOS concretes respectively when compared to that of RS.

For the last decades, concrete materials and technology have been widely developing in many ways in order to achieve an economic and high quality product. But from the other hand concrete offersa wide range of capabilities to achieve a good balance between human needs and earth's capacity which is known as the sustainability. Two stage concrete (TSC) known sometimes as preplaced aggregate concrete (PAC) is a relatively as a new concrete type which has ability to satisfy the requirements of performance and sustainability. Its main concept depends on pre-packing the coarse aggregates in the formwork, then injecting cement mortar grout into the voids in between the aggregates. TSC differs from conventional concrete in having a higher percentage of coarse aggregates which are placed in direct contact with each other resulting in fewer voids that are to be filled with the cement mortar/grout. This low percentage of voids should have a positive impact on the concrete properties both on short and long term basis.The behaviour of TSC in compression has been well documented, but there are little published data on its behaviour in tension and modulus of elasticity. This paper presents results of experimental testing of TSC made with two types of coarse aggregates and three different mix proportions of grout. It was found that the modulus of elasticity of two-stage concrete is equivalent or higher than that of conventional concrete for the same compressive strength. Relationships of stress versus strain and modulus of elasticity versus compressive strength were statistically derived and elaborated.

The aim of this study was to find a new method for usage of the hazardous waste coming from the aluminium scrap recycling factories. It is generally considered that non-metallic residues (NMR) are process waste and subject to disposal after residual metal has been recovered from primary dross. NMR are impurities, which are removed from the molten metal in the process of dross recycling, and it could be defined as a hazardous waste product. Processing of NMR created in the aluminium scrap recycling companies is one of the most challenging tasks due to its toxic nature - in accordance with the Basel Convention, Annex III, marking of this waste is H 4.3 (reaction with water results in highly inflammable substances) and H 10 (reaction with water results in increased concentration of toxic gases, for instance, ammonia). The new alkali activated materials, which could be defined as porous building materials, were created by using calcined illite clay from local site and NMR. Solution of sodium silicate (Na₂SiO₃+nH₂O) modified by commercially available alkali flakes (NaOH) was used as an activating solution. Polymerization mechanism of raw materials in alkaline media was investigated by using FTIR and XRD. Physical and thermal properties of the obtained materials were tested. Density of the obtained materials was in the range 550-675 kg/m³, but the total porosity was from 73 to 78%. The compressive strength of the materials was in range from 1.4 to 2.0 MPa. The thermal conductivity of porous alkali activated building materials was between 0.14 and 0.15 (W/(m·K).

Steel fibers have been used worldwide to enhance properties of concrete but have not yet gained popularity in Pakistan. An experimental study was conducted to study the mechanical properties of steel fiber reinforced concrete that would lead to recommendation for possible use in Pakistan. Steel fibers conforming to recommendations of ACI Committee 544 were used with cement, sand and silica fume to cast samples for testing. Coarse aggregates were not used in order to compare the properties with famous Ultra High Performance ductile Concrete (UHPdC). Three different mixes were made with 2.5%, 5% and 8% of steel fibers by total weight of batch mix. Water cement ratio was kept as low as 0.25 to obtain high strength. Super plasticizer was added to increase workability. Reduction in flowability of concrete was observed with increasing percentage of fibers. Compressive, splitting tensile and flexural strengths were defined by testing standard cylinders and beams made up of different mixes of SFRC. Highest compressive, splitting tensile and flexural strengths were observed for steel fiber content of 8% followed by 5% and then 2.5% fiber contents as expected. Achieved compressive, splitting tensile and flexural strengths were much higher than the conventional concrete strengths used in Pakistan. Results of the study indicate that SFRC has the potential to be used in Pakistan in structures where high strength and is desired. Durability aspects of SFRC have to be looked into before it can be used in structures exposed to aggressive environments or located in coastal areas.

In order to reduce the footprint over the environment, regarding the great energy consumption required to produce cement, it was allowed in the International, European and Egyptian standards to produce the blended cement known as CEMII. This work could successfully utilize the fired ceramic wall tiles waste rejected in industry to partially replace cement up to 35% by weight to produce one of the allowed types of CEMII, depending on the fact that Egyptian standards of ceramic wall tiles allows only the 1^st grade to be delivered to the market. The obtained blended cement was found to be in good conformity to the standards.

In the present work, the fired ceramic tiles waste was vey fine ground up to particle size of 70 μm. It was replacing ordinary Portland cement (OPC) known as CEMI42.5N in different proportions, then mixed with sand and water to form mortar. Standard test methods of cement mortar were applied, then the best ratios of additions were investigated. Tools as XRD, XRF, particle size distribution and SEM with EDAX were used to assess both raw materials and the suggested mixtures as well.

The properties of concrete should be estimated in order to simulate the behavior of concrete structures at early age. However, it is difficult to estimate properties of concrete at early age because they change with time, temperature history, humidity and etc. In this study, a new approach is suggested in estimation of concrete properties such as final autogenous shrinkage, final creep coefficient and thermal expansion coefficient. Properties of concrete at early age are estimated by comparing between the results of analysis and experiments considering the effects of mixing material, temperature history and humidity by using thermal stress device which is able to get stress history in a chamber with various temperature history because each step of the analysis has the best values of concrete properties which would result in similar stress results between the analysis and the experiments. The results show that properties of concrete change with time at very early age which is within 1 day and then are converged to constant values.

Construction and Ready-Mix waste constitutes one of the increasing waste potentially useful material is disposed of as landfill. The environmental and economic implications of these are no longer considered sustainable and, as a result, the construction industry is experiencing challenges to overcome this practise. This investigation was aimed at examining the effects of recycled aggregates, ready-mix waste and laboratory waste on the properties of fresh and hardened concrete. Demolished material exhibited lower compressive and flexural strength and high initial slump. Laboratory waste on the other hand, showed a slight decrease in compressive and flexural strength, it however had a constant initial slump and good durability properties. The returned ready mix stone and sand material showed more positive results in most properties as compared to the other two waste materials. This work has demonstrated that there is a potential in utilising recycled aggregate in producing concrete although the actual percentage of substitution has to be determined by the intended application.

A pozzolan is a material that contains reactive silica or silica and alumina. When finely ground and mixed with lime in the presence of water, pozzolans react to form a cement-like product. Uganda has a vast potential for natural pozzolans especially in the rift valley areas. These can be used to produce a cheaper alternative material to Ordinary Portland Cement (OPC). However, limited investigations have been done in the past on their quality and potential to reduce the cost of housing especially for the low-income earners in Uganda. This study was aimed at generating data to determine their suitability for use in low-strength construction applications. The study established diverse physical and chemical properties of natural pozzolans in Uganda. The findings indicate a strong bearing between pozzolan grading and strength development. Due to the cost implications of attaining the finest grades, the ratio of pozzolan to lime in the blend was varied to attain optimum grades that can provide adequate strength for a number of low-strength construction applications without escalating the cost. The study recommends further investigation of strength variations of pozzolan-lime blends to generate products for specific applications at a reasonable cost.

The sealing anchor mortar is a special cement-based engineered material with water-cement ratio (W/C) less than 0.18 and early (1 day) compressive strength greater than 40 MPa. It used high frequency shock pressure molding prepared mortar material with W/C of 0.09-0.18 and pure cement as the gelling material. Among them, the early (1 day) compressive strength of the mortar with W/C of 0.13 and 0.18 being more than 65MPa, and a high late (56 days) strength of 102.4MPa. SEM analysis showed when the W/C was 0.09, only the surface of the cement particles with early hydration (3 days) was hydrated, appearing a loose form and failed to stick together as a whole. The material with W/C of 0.13 and 0.18 produced more C-S-H gel phase and the overall cement particles cemented together whose microstructure was compact and uniform. Unhydrated cement particles mainly played the role of filling and micro-aggregates in the material.

Engineered cementitious composites (ECC) with the excellent tensile strain capacity was made of domestic raw materials except PVA-fiber. The effect of water-binder ratio, fiber content and silica fume content on the mechanical properties was investigated in this paper. While the ECC microstructure was also investigated by Scanning Electron Microscope (SEM). The results showed that high water-binder ratio and larger amount of PVA-fiber will help to improve tensile property of ECC with adding a moderate amount of silica fume. While the compressive strength of ECC was 35.4 MPa to 57.6 MPa, the tensile strain capacity attended to 2.59% to 4.77%. SEM analysis showed that large amount of spherical non-hydrated fly ash could improve the matrix and fiber interface structure. The water-binder ratio has a great effect on the structure compactness of the hydration products and fiber abrasion degrees.