Ready-mixed Concrete Research Articles

Domestic Wastewater Reuse in Concrete Using Bench-Scale Testing and Full-Scale Implementation

Demand for fresh water by the construction sector is expected to increase due to the high increase in the growth of construction activities in Jordan. This study aims to evaluate the potential of scale-up of the application of treated domestic wastewater in concrete from bench-scale to a full-scale. On the lab scale, concrete and mortar mixes using Primary and Secondary Treated Wastewater (PTW, STW) and Distilled Water (DW) were cast and tested after various curing ages (7, 28, 120, and 200 days). Based on wastewater quality, according to IS 456-2000, the STW is suitable for mortar and concrete production. Mortar made with STW at curing time up to 200 days has no significant negative effect on the mortar’s compressive strength. Conversely, the PTW exceeded the maximum permissible limits of total organic content and E coli. for concrete mixing-water. Using PTW results, a significant increase in the initial setting time of up to 16.7% and a decrease in the concrete workability are observed. In addition, using PTW as mixing water led to a significant reduction in the compressive strength up to 19.6%. The results that came out from scaling up to real production operation of ready-mix concrete were in harmony with the lab-scale results.

Safety in ready mixed concrete industry: descriptive analysis of injuries and development of preventive measures

Ready mixed concrete (RMC) industry, one of the barebones of construction sector, has its distinctive occupational safety and health (OSH) risks. Employees experience risks that emerge during the fabrication of concrete, as well as its delivery to the construction site. Statistics show that usage and demand of RMC have been increasing along with the number of producers and workers. Unfortunately, adequate OSH measures to meet this rapid growth are not in place even in top RMC producing countries, such as Turkey. Moreover, lack of statistical data and academic research in this sector exacerbates this problem. This study aims to fill this gap by conducting data mining in Turkish Social Security Institution archives and performing univariate frequency and cross tabulation analysis on 71 incidents that RMC truck drivers were involved. Also, investigations and interviews were conducted in seven RMC plants in Turkey and Netherlands with OSH point of view. Based on the results of this research, problem areas were determined such as; cleaning truck mixer/pump is a hazardous activity where operators get injured frequently, and struck by falling objects is a major hazard at RMC industry. Finally, Job Safety Analyses were performed on these areas to suggest mitigation methods.

Beneficial use of marine dredged materials as a fine aggregate in ready-mixed concrete: Turkey example

This study describes the potential beneficial use of untreated and treated marine dredged material (DM) in ready-mix concrete (RMC) as a fine aggregate. DMs collected from four Turkish ports/harbours were characterized, assessed according to the National Legislation and transformed into one composite DM. Silica sand was replaced with untreated- and treated-composite-DM (COMP-U/COMP-T) at five ratios (0%, 25%, 50%, 75%, 100%), respectively. Mechanical, durability, leaching, mineralogical/micro-structural properties of DM-based-RMCs were analysed. Concretes having 50% COMP-U and 100% COMP-T met the minimum requirement for C25/30 class RMC. Marine DM can be beneficially used in RMC production; however, DM pre-treatment should be applied.

Study on preparation of precipitated calcium carbonate using recycling water of ready-mixed Concrete

Study on preparation of precipitated calcium carbonate using recycling water of ready-mixed Concrete

Study on optimization of liquid carbonation pilot plant (system) using sludge water of ready-mixed concrete

Study on optimization of liquid carbonation pilot plant (system) using sludge water of ready-mixed concrete

Effective ready mixed concrete supply adjustments with inoperative mixers under stochastic travel times

The purpose of this study is to develop a systematic scheduling model that will help ready mixed concrete (RMC) carriers/suppliers with effective scheduling adjustment after temporary breakdown of mixers under stochastic travel times. The model is formulated as a mixed integer network flow problem with side constraints that is characterized as NP-hard. The authors employ problem decomposition and relaxation techniques, with a mathematical programing solver, to develop an algorithm that is capable of efficiently solving the problem. A simulation-based evaluation method is also proposed to evaluate the model, joined with a deterministic model, as well as the method currently used in actual operations. Finally, a case study is performed using real operating data from a Taiwan RMC firm. The preliminary results demonstrate that the stochastic model and the solution algorithm could be useful to reduce system cost for the RMC carrier in actual operations.

Performance-based Durability Indicators of Different Concrete Grades Made by the Local Ready Mixed Company: Preliminary Results

The durability of a material is defined as its ability to withstand environmental deterioration. The ability of a concrete structure is to withstand environmental deterioration is important to be investigated in order to enhance the service life of the reinforced concrete structure without having to incur unforeseen high cost for maintenance or repair. The quality of the concrete on durability aspect has to be evaluated through series of concrete durability experiments before the service life model has taken place rather than relies on the conventional prescriptive deemed-to-satisfy approach. Performance-based durability is thus based on durability transport properties instead of limiting particular ingredients, proportions or construction operations without predicting the service life of structure. In order to fulfill customer satisfaction with lasting and great concrete performance at reasonable grade concrete, it is important to conduct various experiments to identify the durability transport properties parameters on the earlier stage of construction. The experiments performed in this study are water absorption, volumes of permeable void (VPV) and sorptivity. The experiment was investigated using Ready mixed concrete of grades G40, G45 and G50 that has been conducted to determine the properties at different concrete zones using 150 mm and 100 mm for compressive strength test. The strength of G50 increases 18% in sealed curing and site cured concrete has 8% strength increments from 28-90 day of age. Concrete G40 has the highest water absorption, VPV and sorptivity properties followed by G45 and G50 in all ages of test under both curing conditions. Amongst all the different zones, top zone has highest water absorption, VPV and sorptivity followed by left and right zone for all grade. Meanwhile, the bottom zone has the lowest water absorption, VPV and sorptivity followed by middle and center zone of concrete for all grades. The sealed cured (S1) concrete condition shows relatively lower water absorption, VPV and sorptivity than site cured (S2) concrete condition.

Fundamental properties of industrial hybrid cement: utilization in ready-mixed concretes and shrinkage-reducing applications

Utility properties of novel hybrid cement (H-Cement) are influenced by pozzolanic reaction of fly ash, latent hydraulic reaction of metallurgical slag together with the alkali activation of inorganic geopolymer based on precipitated waste water coming from bauxite residues. Content of Portland cement clinker is at maximum of 20 mass %, the remaining portion consists of inorganic geopolymer. Up to 80% of CO2 emissions are saved by H-Cement manufacture compared to ordinary Portland cement (OPC). No heat treatment or autoclaving is needed at H-Cement production. The field application of H-Cement is performed by the same way than that of common cements listed in EN 197-1, and is also connected with highly efficient recovery and safe disposal of red mud waste. H-Cement is suitable for ready-mixed concretes up to C30/37 strength class and is specified by beneficial shrinkage-reducing property of the concrete kept in long dry-air cure opposite to common cements.

Productivity Dispersion in Medicine and Manufacturing.

The conventional wisdom in health economics is that large differences in average productivity across US hospitals are the result of idiosyncratic features of the healthcare sector which dull the role of market forces. Strikingly, however, we find that productivity dispersion in heart attack treatment across hospitals is, if anything, smaller than in narrowly defined manufacturing industries such as ready-mixed concrete. While this fact admits multiple interpretations, it suggests that healthcare may have more in common with “traditional” sectors than is often assumed, and relatedly, that insights from research on productivity and allocation in other sectors may enrich analysis of healthcare.

Matching experts' decisions in concrete delivery dispatching centers by ensemble learning algorithms: Tactical level

Abstract Ready Mixed Concrete (RMC) suffers from a lack of practical solutions for automatic resource allocation. Under these circumstances, RMC dispatching systems are mostly handled by experts. This paper attempts to introduce a machine learning based method to automatically match experts' decisions in RMC. For this purpose, seven machine learning techniques with their boosted algorithms were selected. A set of attributes was extracted from the collected field data. Eleven metrics were used to assess the performance of the selected techniques using different approaches. Due to concerns about randomness, significant testing was performed to assist in finding the best algorithm for this purpose. Results show that Random-Forest with 85% accuracy outperforms the other selected techniques. One of the most interesting achieved results is related to the computing time. The results show that all the selected algorithms can solve large-scale depot allocations with a very short computing time. This is possibly because a model built by a machine learning algorithm only needs to be tested with new instances, which does not need an extensive computation effort. This provides us with a chance to move toward automation in Ready Mixed Concrete Dispatching Problems (RMCDPs), especially for those RMCs with dynamic environments where resource allocation might need to be quickly recalculated during the RMC process due to changes in the system.

LCA 기반 PSC 교량의 환경부하 특성분석에 대한 연구

This study aims to analyze characteristics of environmental load for the construction phase of PSC beam bridge based on Life Cycle Assessment. For detail computation of environmental load, the construction materials and energy consumption are derived from the BOQ, also connecting with environmental load by Korea LCI Database Information Network. The characteristic of environmental impact was analyzed by 25 cases and cut-off ratio was 80% to 94%. The result sorted by construction materials revealed that environmental load were 53.3% for ready-mixed concrete, 9.6% for wire rod, 7.8% for rebar, 6.8% for cement, 5.5% for plywood, and 5.2% for energy. Furthermore, the result of environmental impact revealed that 45.5% for global warming, 30.4% for abiotic resources depletion, 10.5% for human toxicity, and 8.9% for photochemical oxidant creation. In the future, we can make a decision considering environmental load based on LCA at design phase.

Financial assessment of manufacturing recycled aggregate concrete in ready-mix concrete plants

Concrete waste is crushed in the present recycling operation to produce crushed concrete (CC), which is mostly used as a road base filler material. The coarse portion of CC, referred to as recycled concrete aggregate (RCA) can be used in structural concrete replacing coarse natural aggregate (NA). The resultant concrete which is referred to as recycled aggregate concrete (RAC), would create a sustainable end use for concrete waste, and reduce the demand for NA, leading to its preservation. However, the concrete industry has been reluctant to embrace production of RAC to its full potential. Beside uncertainty regarding material performance, options available to effectively set up the existing plant operations to manufacture RAC is yet to be explored. This paper attempts to simulate the manufacturing set up to produce RAC by integrating processes involved in concrete waste recycling and readymix concrete (RMC) production environments. It presents a model to evaluate the financial effect of manufacturing RAC in lieu of normal concrete, calibrated with data from RMC manufacturing and recycling plants. Analysis of the response to produce RAC highlights that the price of RAC differ significantly based on the type of RMC manufacturing plant and the cement content of the mix. It is observed that it is highly probable that the price of RAC is 0–10% higher than that of natural aggregate concrete (NAC). Probabilistic estimation of the price difference between RAC and NAC concludes that RMC plants having aggregate feeding mechanism with front-end loader (FEL) would be an appropriate entry for industrial scale manufacturing of RAC.

Effects of recycled aggregates from construction and demolition wastes on mechanical and permeability properties of paving stone, kerb and concrete pipes

The main objective of this research is to investigate the utilization criteria of the recycled aggregates gained from construction and demolition wastes, in the production of various ready-mixed and precast concrete elements. Within this scope, construction and demolition waste materials were selectively separated to have homogeneous concrete wastes in the recycling plant. Then, fine and coarse aggregates were achieved from concrete wastes. Recycled concrete aggregates were than crushed to specific sizes; physical properties were determined and compared with those of normal aggregates. Finally, these recycled aggregates were investigated about their utility in the industrial production of various concrete products like ready-mixed concrete, concrete pipe, paving stone and kerbs. Also some studies were done to determine durability and permeability properties of these products. It can be concluded that the use of recycled aggregates in the production of various concrete elements is possible with proper separation and classification. Moreover, lower replacement rates should be applied to obtain sufficient conditions which are specified in related product standards.

Experimental investigation of the utilization of quarry dust for the production of microcement-based building elements by self-flowing molding casting

The management and disposal of fine by-products produced by the aggregate industry, ready-mix concrete and asphalt concrete installations (also known as filler or quarry dust), emerges as a major environmental problem of quarrying and construction sector. Even though considerable research has been undertaken for the utilization of this fine by-product in several applications, it still remains under-utilized, while its disposal and stabilization is also problematic due to resulting emissions of airborne particle pollutants. In this study the production of self-flowing castable cement-based building elements incorporating high amounts of quarry dust was investigated in laboratory scale. Quarry dust, microcement, water and concrete admixtures were mixed and casted in steel molds for the production of the specimens. The initial study of mixtures composition was based on the Andreassen particle packing model, while the final mix design was determined via Box–Behnken fractional factorial design of experiments, in combination with the response surface method. The compressive strength and water absorption values of hardened specimens exceed the relevant technical requirements currently in force, regarding load-bearing as well as decorative building elements, thus opening a new promising field for the utilization of this by-product.

Application of Bayesian updating for real-time schedule estimation in a concreting operation

Ready-Mixed Concrete (RMC) delivery schedules should be carefully planned due to the limited time span between mixing and placing. The scheduling of RMC supply is challenging to both contractors and plant managers because of multiple operational issues such as traffic conditions and unloading delays. Simulation has been applied to address this challenge; however, the unique and complex nature of construction environments raises a validity issue in the use of previous datasets as input for the simulation of a new operation. Based on this recognition, the idea of using real-time data has been proposed to address the input data validity issue and to enhance the predictability of the simulation model. One important concern that has not yet been fully addressed regarding this issue is the amount of data collection required to yield a valid sample such that the output is sufficiently reliable. To answer this question, this paper uses a Bayesian updating technique with data collected from a concreting operation in a high-rise building project in Abu Dhabi. Through the case study it is concluded that the Bayesian forecasting technique has great potential for providing a better statistical representation of operational data and improving the predictability of the simulation model.

Optimal materials purchasing for ready-mixed concrete in construction projects with environmental effects

Construction project managers require many different kinds of ready-mixed concrete. In this paper, a materials purchasing optimisation model is established for ready-mixed concrete in construction projects. The proposed model can determine the optimal balance between different objectives and takes account of the complex dynamics and uncertainties in the decision-making process. Further, materials recycling and carbon emissions can also be considered as part of the materials supply planning. We also show the feasible constraints that the managers may have a finite preference for some resource limitation. Then, a dynamic programming-based particle swarm optimisation is developed to determine the optimal solutions to the material purchasing problem. The operational performance of the proposed quantitative method is tested using data from a Chinese hydropower construction project in which it is shown that human uncertainty can be a significant factor in the purchasing problem that materials purchasing quantities are significantly influenced by recycling and that including recycling in the purchasing problem can not only save money but also reduce pollution.

The Rheological and Mechanical Performances of Concrete Manufactured with Blended Admixtures Based on Phosphonates

The paper deals with the effectiveness of blended phosphonate-based superplasticizers (PHN) for ready mixed concrete. Two phosphonates (PNH1 and PNH2) were added in different percentage to naphthalene sulphonate (NSF) or polycarboxylates (PCEs) based admixtures to improve both compatibility with different cements and workability retention of concrete. The performance of the obtained concrete mixtures was compared to concretes manufactured with the pure NSF or PCE based admixtures. Concretes with the same initial workability (flow table > 580mm) were produced at a temperature of 20 °C and 30 °C. Workability was measured at 0, 30 and 60 minutes to evaluate the flow retention performances of blended superplasticizers. Compressive tests were carried out to study the influence of the superplasticizer on concrete strength gain at the age of 1, 7 and 28 days. PNH1 in combination with NSF improved workability retention with respect to pure NSF, but caused a reduction in the early compressive strength when the dosage exceeded 0.10% (dry polymer vs. cement mass). Dosage of hybrid PCE-PNH superplasticizers to attain the targeted workability was lower with respect to hybrid PNH1/NSF admixtures. PNH1 was more effective than PNH2 in hybrid PCE admixtures in terms of workability retention. A threshold value for PNH dosage (about 0.18 - 0.20 %) exists also in hybrid PCE superplasticizers, but it is about two times higher than that of hybrid PNH1/NSF.

Use of Recycled Concrete Aggregates in Precast/Prestressed Concrete

This paper describes a preliminary investigation on factors related to the use of recycled concrete aggregates (RCA) in precast/prestressed concrete applications. In particular, the effects of RCA are experimentally investigated for: 1) the bond between seven-wire prestressing steel strand and concrete; 2) the compression strength gain of concrete with time; and (3) the compression stiffness gain of concrete with time. The test specimens were made by replacing the natural course aggregates in the concrete mixtures with RCA from: 1) discarded/rejected precast concrete; and 2) returned ready-mix concrete. The data to-date show that the introduction of RCA results in an effect (decrease or increase) in the strand bond strength that is consistent with the effect of RCA on the compression strength of concrete. For the materials tested, RCA from precast concrete performed better than RCA from returned ready-mix concrete. The use of RCA did not have a significant effect on the rate of concrete compression strength gain with time. The results for the stiffness gain of concrete with time were somewhat more varied than the results for the strength gain.

Hybridizing a fuzzy multi-response Taguchi optimization algorithm with artificial neural networks to solve standard ready-mixed concrete optimization problems

AbstractIn this study, a fuzzy multi-response standard ready-mixed concrete (SRMC) optimization problem is addressed. This problem includes two conflicting quality optimization objectives. One of these objectives is to minimize the production cost. The other objective is to assign the optimal parameter set of SRMC’s ingredient to each activity. To solve this problem, a hybrid fuzzy multi-response optimization and artificial neural network (ANN) algorithm is developed. The ANN algorithm is integrated into the multi-response SRMC optimization framework to predict and improve the quality of SRMC. The results show that fuzzy multi-response optimization model is more effective than crisp multi-response optimization model according to final production cost. However, the ANN model also gave more accurate results than the fuzzy model considering the regression analysis results.

Current Methods for the Utilization of the Fresh Concrete Waste Returned to Batching Plants

As the fresh concrete waste has a high potential to damage the environment, current methods for the utilization of the returned ready-mixed concrete were presented throughout this study. Toward this aim, an in-depth literature review was performed as a methodological approach. Thus, types of the returned concrete were first explained and the existing methods were then discussed one by one. Consequently, the current methods were determined as (i) matching with suitable customers, (ii) blending with next matches, (iii) discharging into the settling basin, (iv) discharging onto the ground, (v) producing pre-cast concrete components, (vi) recycling mechanically, (vii) using the hardened slurry cake in concrete, (viii) using the hardened slurry cake in partition wall blocks, (ix) using hydration stabilizer admixtures, and (x) using superabsorbent polymer.