Use of Prefabrication, Construction and Demolition Wastes as an Aggregate in Vibropressed Precast Concrete Blocks Production

The aim of current study was to determine the recycled concrete aggregate (RCA) applicability in the production of concrete mixture for vibropressed concrete blocks. The experiments were focused especially on the crushed waste material from the same concrete elements producing plant. For this type of precast elements only some finer fractions can be implemented and the “earth-moist” consistency of fresh mixture is required. The series of samples was prepared in which the mixture of natural aggregates was partially or totally substituted by recycled concrete aggregate. The 0/4 RCA fraction, which is usually rejected in ready mix concrete technology, plays a role of 0/2 sand. The substitution of sand fraction was from 20% to 100% respectively. The substitution of the coarser aggregate fractions by 4/16 RCA was also done. The standard properties of vibropressed elements, such as the degree of densification, the density of material, the compressive and splitting tensile strength and the water absorption capacity according to the relevant standards were determined. The parameters of materials with the natural aggregate substitution by RCA are affected by the ratio of recycled concrete aggregate. In most cases the results do not decline specially from those for reference samples, when only the natural sand (0/2) fraction is substituted by the 0/4 recycled aggregate. As one could expect, as lower the substitution, as better the test results. The partial substitution of natural aggregate by coarser fractions requires experimental verification; over 20% substitution of natural aggregate by 4/8, 8/16 or 0/16 RCA should be excluded.

The properties of preplaced aggregate concrete technology contain the industrial waste-material and the various shapes and sizes of coarse aggregate

The success of preplaced aggregate concrete technology depends on two main factors which are potential grout and coarse aggregate. This research was conducted experimentally to determine the effect of using two different fly ash sources as an alternative for the partial replacement of cement and several size and shapes of coarse aggregate on the compressive and tensile strength of PAC specimens. This involved the use of seven concrete mixes with a low water-cement ratio of 0.4 and cement to sand ratio of 1:0.75 to produce standard cylinder specimens of concrete containing rounded and crush aggregate. Moreover, fly ash was added at a dosage of 5% and 10% of cement weight while three shapes and sizes of a rounded and crushed aggregate at 20 mm, 30 mm, and a mixture of the two were also applied. The results showed the compressive strength of specimens with different sizes or a mix of rounded aggregate in PAC exhibited a similar performance with 30 mm of crushed coarse aggregate. Furthermore, the specimen with a higher content of calcium fly ash demonstrated a more rapid strength at an early age of seven days than those with lower content. Therefore, the partial replacement of cement with industrial waste material in the form of fly ash in preplaced aggregate concrete has the ability to save up to 10% of cement and also produce certain environmental benefits.

3D printing-A Review of Materials, Applications, and Challenges

Now a days 3-Dimensional Printing (3DP) technology is used world widely and it can actually print each and every thing with the desired computer program. In Construction engineering the challenges are like availability of skilled man power, time constraint, cost effectiveness and complicated shapes etc. But with the help of an automated machine, the 3D printing technology, has huge potential to have faster and more accurate construction of complex and more laborious works. This technology can build three-dimensional (3D) objects by connecting layers of materials and can be applied to convert waste and by-products into new materials. The 3DP in concrete construction is increasing thanks to its freedom in geometry, rapidness, formwork-less printing, low waste generation, eco-friendliness, cost-saving nature and safety. This paper attempts to review the digital printing technology introduced in the construction industry and the also highlights the impact on concrete technology. It also discusses about the materials used in 3DP, mix design, various applications and challenges in the construction industry. Keywords: 3D printing, Concrete, 3DCP, Mix design.

Novel Fuzzy-Based Optimization Approaches for the Prediction of Ultimate Axial Load of Circular Concrete-Filled Steel Tubes

An accurate estimation of the axial compression capacity of the concrete-filled steel tubular (CFST) column is crucial for ensuring the safety of structures containing them and preventing related failures. In this article, two novel hybrid fuzzy systems (FS) were used to create a new framework for estimating the axial compression capacity of circular CCFST columns. In the hybrid models, differential evolution (DE) and firefly algorithm (FFA) techniques are employed in order to obtain the optimal membership functions of the base FS model. To train the models with the new hybrid techniques, i.e., FS-DE and FS-FFA, a substantial library of 410 experimental tests was compiled from openly available literature sources. The new model’s robustness and accuracy was assessed using a variety of statistical criteria both for model development and for model validation. The novel FS-FFA and FS-DE models were able to improve the prediction capacity of the base model by 9.68% and 6.58%, respectively. Furthermore, the proposed models exhibited considerably improved performance compared to existing design code methodologies. These models can be utilized for solving similar problems in structural engineering and concrete technology with an enhanced level of accuracy.

Design of Cold-Mixed High-Toughness Ultra-Thin Asphalt Layer towards Sustainable Pavement Construction

Ultra-thin asphalt overlay has become the mainstream measure of road preventive maintenance due to its good economic benefits and road performance. However, hot mix asphalt concrete technology is widely used at present, which is not the most ideal way to promote energy saving and emission reduction in the field of road maintenance. At the same time, the ultra-thin friction course based on cold mix technology, such as slurry seal layer, micro-surface, and other technologies, are still far behind the hot mix friction course in terms of crack resistance. In this research, by establishing an integrated design of materials and structures, a cold paving technology called “high-toughness cold-mixed ultra-thin pavement (HCUP)” is proposed. The high-viscosity emulsified bitumen prepared by using high-viscosity and high-elasticity modified bitumen is used as the binder and sticky layer of HCUP. The thickness of HCUP is 0.8–2.0 cm, the typical thickness is 1.2 cm, and the nominal maximum size of the coarse aggregate is 8 mm. Indoor tests show that HCUP-8 has water stability, anti-skid performance, high temperature performance, peeling resistance, and crack resistance that are not weaker than traditional hot-mixed ultra-thin wear layers such as AC-10, Novachip, and GT-8. At the same time, the test road paving further proved that HCUP-8 has excellent road performance with a view to providing new ideas for low-carbon and environmentally friendly road materials.

Unspoken Modernity: Bamboo-Reinforced Concrete, China 1901-40

Engineering science in the China of 1901-40 had unique characteristics that disrupt the idea of a universal approach to its history.1 The following case study describes the ideas and trials of introducing bamboo into the seemingly globalised technology of reinforced concrete—an innovation developed across the borders of mechanical, naval, civil, and aeronautical engineering. The article showcases a way of knowing and working by twentieth century engineers that has not been fully acknowledged, and is not only a phenomenon of China. While bamboo was a complicated and somewhat marginal object for engineering, it did make the European concrete technology more viable in the construction sites of China, and stimulate engineers’ experimental and resourceful spirit in mobilising both craft and scientific knowledge. It also opened up a challenge to engineering science of the time.

Water Absorption of Incorporating Sustainable Quarry Dust in Self-Compacting Concrete

In construction industry nowadays, self-compacting concrete (SCC) is a concrete technology innovation which gives more benefits over conventional concrete. SCC was invented to improve concrete durability without using any vibrator while placing it into formwork. In order to conserve natural sand, quarry dust (QD) as a waste and sustainable material has been incorporated to replace fine aggregate in SCC. In this study, conventional concrete and quarry dust in self-compacting concrete (QDSCC) mixes consist of 0%, 10%, 20%, 30%, 40% and 50% QD were prepared. The workability test was conducted to determine the performance of fresh concrete and ensuring all the QDSCC properties follow the acceptance criteria for SCC. Meanwhile, the hardened concrete specimens were water cured for 7, 28 and 60 days to conduct water absorption test. This research aim is to determine water absorption of incorporating sustainable QDSCC. Thus, it resulted that 50% of QDSCC has achieved the lowest water absorption of QDSCC as compared to other dosages. Finally, sustainability in concrete technology can be promoted by incorporating QDSCC.

Evaluation of Rapid Repair of Concrete Pavements Using Precast Concrete Technology: A Sustainable and Cost-Effective Solution

Concrete and asphalt are the two competitive materials for a highway. In Sweden, the predominant material for the highway system is asphalt. But under certain conditions, concrete pavements are competitive alternatives. For example, concrete pavements are suitable for high-traffic volume roads, roads in tunnels, concentrated loads (e.g., bus stops and industrial pavement). Besides the load-carrying capacity, the concrete pavement has many advantages such as durability (wear resistance), resistance against frost heave, environment (pollution, recycling, and low rolling resistance leading to fuel savings), fire resistance, noise limitations, brightness, evenness and aesthetics. Concrete pavements are long-lasting but need final repair. Single slabs may crack in the jointed concrete pavement due to various structural and non-structural factors. Repair and maintenance operations are, therefore, necessary to increase the service life of the structures. To avoid extended lane closures, prevent traffic congestions, and expedite the pavement construction process, precast concrete technology is a recent innovative construction method that can meet the requirement of rapid construction and rehabilitation of the pavement. This paper evaluates rapid repair techniques of concrete pavement using precast concrete technology by analysing three case studies on jointed precast concrete pavements. The study showed that the required amount of time to re-open the pavement to traffic is dramatically reduced with jointed precast concrete panels.

Application of electro-hydraulic shock in concrete technology

The aspects, related to the influence of the electrohydraulic shock method use in a water-cement slurry passing in a closed chamber (activation reactor) with a pre-applied pressure to the system under various processing modes are highlighted in the article. In order to test the effect of this method on water-cement slurry, an installation was developed, consisting of: a high-voltage source, a high-voltage diode, capacitor banks, a closing element and an activation reactor. The necessary experiments were carried out on the completed installation. The procedure for conducting experiments is described in the work, shows a schematic diagram of the installation for performing activation, a diagram of the reactor, and the processing modes. Several activation modes were considered, depending on: the number of pulses (1-4), pulse energy (0.5-8 kJ), water-cement ratio (0.2-0.35), time intervals for starting treatment from the moment the cement was mixed with water (0 -120 minutes), volume and shape of the container (activation reactor), holding temperature (20-60°C), etc. According to the results of the data obtained, it was experimentally established that the use of electric pulse treatment of water-cement suspension has a positive effect on strength (cup compressive strength) indicators, obtained as a result of processing cement stone samples at different times of hardening (1-3 days). The compressive strength of the treated specimens’ increases in comparison with the untreated specimens, increase in strength reaches up to 45%, depending on the activation mode. The resulting effect was achieved due to many factors (high pressure, magnetic, temperature, energy, ultrasonic and other influences), which were applied in the most optimal period of time (stage) of the cement grain hydration process.

Built Infrastructure Renewal and Climate Change Mitigation Can Both Find Solutions in CO2

From technology to policy, the US is thinking about construction differently. The federal government is motivated to address the aging infrastructure across the country, and policy proposals are surfacing that seek green methods of performing this construction. This paper reviews the current status of concrete technology and policy to provide insight into the current state of the art. The scale of CO2 emissions from concrete production and use is elucidated. Current embodied emissions reduction methods show that action can be taken today in small and large projects alike. Additionally, developing concrete technologies offers pathways to reuse and rely on concrete for longer service lifetimes and reduce their lifetime embodied emissions. These concrete technologies must be implemented, and public procurement proves a unique tool to develop a nationwide demand signal for low embodied carbon building materials. Local governments closely interact with concrete producers, state governments oversee large infrastructure projects, and the federal government invests massively in construction. All three levels of government must coordinate for the effective rollout of low embodied carbon construction practices. Disparate policy approaches show successes and pitfalls to developing an effective construction policy that is aligned with climate. Importantly, approaches to addressing the twin challenge of climate change and crumbling infrastructure must consider the whole lifetime of the concrete. Throughout this paper, we examine the sector to highlight current practices and provide a vision for effective implementation.