Precast Products Research Articles

Characteristics of self-compacting green concrete

Locally, conventional concrete is still created utilizing river sand and crushed stone as filer materials. The massive quarry dust by-product remain untapped in the production of concrete. The coal-fired power station produce significant quantities of Type F fly ash. Self-compacting concrete (SCC) provides many advantages for creating high-quality concrete. Consequently, the main objective of this research is to create a mix design for high-strength SCC utilizing a binary blends, hybrid fibers and fine aggregates that meet both hardened and fresh concrete characteristics. The study is conducted in amendment of w/b ratio, superplasticizer, proportion of fine aggregate to coarse aggregate, optimumal cement replacing by fly ash, dosage of low macro fibre and micro fibre. Mix-50c-X is the best mix design that was produced. The mix quantity for 1m3 concrete was 315 kg Class F fly ash, 315 kg OPC, 630 kg quarry dust, 508 kg river sand, 400 kg coarse aggregate, 0.7% superplasticizer,0.32% w/b, 0.10% macro fiber, and 0.01% micro fiber. This SCC mixture showed fresh characteristics as well as compressive strengths of more than 22 MPa and 62 MPa after 1 day and 28 days, respectively. The results of high-strength SCC demonstrated the enormous potential for the local construction, especially precast product.

Effects of polycarboxylate superplasticizer and hydroxypropyl methylcellulose on the properties of ferric-rich sulfoaluminate cement

Ferric-rich sulfoaluminate cement (FR-SAC) is a promising low-carbon cement and is usually used to prepare precast products due to its short setting time. However, the fast setting of FR-SAC paste also leads to its poor fluidity and workability. Polycarboxylate superplasticizer (PCE) and hydroxypropyl methylcellulose (HPMC) can improve the fluidity and viscosity but may affect other properties of FR-SAC products. To get a suitable performance of FR-SAC by adding PCE or HPMC, the properties of FR-SAC paste with PCE and HPMC added and their influence mechanism were explored. The results indicate that PCE adsorbs on the surface of positively charged ettringite in the slurry under the electrostatic attraction, which makes the negatively charged or uncharged FR-SAC particles uniformly dispersed in the slurry, thus regulating the rheology and other properties of FR-SAC paste. The compressive strength of FR-SAC paste increases with the increase of PCE addition. PCE slightly retard the early hydration rate of FR-SAC but does not affect the formation of later hydration products. Adding HPMC to FR-SAC paste can decrease the fluidity and increase the viscosity of FR-SAC paste but has little effect on its hydration properties. Therefore, when PCE and HPMC are used to modulate the rheology of FR-SAC paste, it is necessary to combine the utilization process and compressive strength requirements to keep both the rheological parameters and compressive strength in the suitable condition.

Effect of different aggregates on the properties of carbonated self-pulverized low-calcium clinker mortar

This study investigated the effects of four aggregates - standard sand, manufactured sand, slag, and coal gangue - on the properties of carbonated self-pulverized low-calcium clinker (SPLCC) mortars. The SPLCC, aggregates, and water were mixed in a mass ratio of 1.00:2.50:0.15 and compaction molded, then carbonation cured by 99.99 % CO2 exposure at 0.2 MPa. Tests determined the weight gain, compressive strength, water absorption, and interfacial transition zone (ITZ) microstructure after 1, 4, and 24 h of curing. Results showed the manufactured sand mortar had the highest compressive strength (39.7 MPa) and lowest water absorption (3.50 %) at 24 h, indicating the best macroscopic performance. This was due to the manufactured sand's stone powder content improving SPLCC binding and accelerating calcium carbonate accumulation in the ITZ. Nanoindentation revealed the manufactured sand mortar had the narrowest ITZ width (15 μm). SEM-BSE also showed higher Ca content in its ITZ. The Ca: Si ratio in the ITZ strongly correlated with strength and absorption. Overall, manufactured sand as aggregate can enhance carbonated SPLCC mortar properties, providing potential for precast products.

Enhancement of Alkali Resistance of Glass Fibers via In Situ Modification of Manganese-Based Nanomaterials.

Glass fibers are widely used in cement-based precast products, given the reinforcing requirements for toughness and strength. However, inferior alkali resistance hinders the effectiveness of glass fibers in reinforcing cement-based materials. In this paper, nanoparticle coatings were applied on the surface of alkali-resistant glass fiber (ARGF) as a protective layer via the in situ chemical reaction of oleic acid (OA) and potassium permanganate (PP). The morphology and constituents of the as-prepared ARGFs were examined using scanning electron microscopy (SEM) and obtaining X-ray photoelectron spectroscopy (XPS) measurements. Mass loss and strength retention were investigated to characterize alkali resistance of modified ARGFs. Results showed that ARGFs could be optimally coated by a layer of MnO2-based nanoparticles consisting of approximately 70% MnO2, 18% MnO, and 12% MnSiO3, when modified with an optimum OA to PP ratio of 10 for 24 h. The dissolution of ARGFs matrix in 4% and 10% NaOH solutions were distinctly delayed to 28 d, as a consequence of the introduction of the MnO2-based nanoparticle layer, compared with nontreated ARGF occurring at 3 d in 4% NaOH solution. For the optimally modified ARGFs, the mass loss was controlled to 1.76% and 2.91% after 90 d of corrosion in 4% and 10% NaOH solutions, and the retention of tensile strength was increased by approximately 25%. With respect to the increment in alkali-resistant performance, the modified ARGFs can be promising candidates for wide applications in alkaline cement-based products.

Development and Promotion of Concrete Strength at Initial 24 Hours.

Knowing and promoting the strength development of concrete at an earlier age is essential for accelerating formwork circulation of the on-site construction and precast product manufacture. The strength development rate at earlier ages of less than the initial 24 h was investigated. The effect of measures of adding silica fume, calcium sulfoaluminate cement, and early strength agent on the strength development of earlier concrete at ambient temperatures of 10, 15, 20, 25, and 30 °C was studied. The microstructure and long-term properties were further tested. It is shown that the strength increases exponentially first and then logarithmically, different from what is commonly recognized. Increasing cement content exhibited a certain effect only above 25 °C. When the cement content increased from 420 to 460 kg/m3, the strength only increased from 6.2 to 6.7 MPa after 12 h at 25 °C. The early strength agent could increase the strength significantly, the strength could be increased from 6.4 to 10.8 MPa after 20 h at 10 °C and from 7.2 to 20.6 MPa after 14 h at 20 °C. All measures for promoting earlier strength did not have an evident negative effect. The results could be potentially referred for the formwork removal at a suitable moment.

Implementasi Sistem Manajemen Keselamatan dan Kesehatan Kerja (SMK3) Pada Pekerjaan Proyek Pembangunan Infrastruktur

ABSTRACT: The development of technology and information today is very closely related to capacity building in the world of construction, especially in the implementation of infrastructure development projects. This development can be seen from the use of various modern equipment, types of materials and production methods and procurement processes. Humans as workers also experience development in their efforts to get jobs armed with skills and expertise. Based on this, workers as the spearhead in the management and implementation of the project are the main concern to ensure the safety and health of their work In this study it is devoted to knowing the general conditions of the contractor's activities and work activities in carrying out the Occupational Safety and Health Management System, how the Occupational Safety and Health Management System (SMK3) is owned by the contractor, both in field conditions or standard operating conditions and how conformity elements of the implementation of the Occupational Health and Safety Management System with ISO 45001:201, Government Regulation Number 50 of 2012. From the research results it can be said that contractors engaged in road construction construction services, in carrying out their projects in accordance with their duties, principals and functions and produce various types of construction products, such as "U-ditch" pre-cast products. Implementation In implementing project SMK3, planning management is determined using SMKK (Construction Safety Management System) which refers to PUPR Ministerial Regulation Number 10 of 2021. In implementing OSH performance, companies have made efforts to carry out SMK3 procedures in general that are appropriate and refer to PP Number 50 of 2012 and ISO 45001: 2018 with the results of an analysis of the implementation for the K3 performance aspect which refers to the two SMK3 elements according to Government Regulation Number 50 of 2012 and ISO 45001: 2018 of 74.8% and for the provision of various safety support facilities at work of 71% .
 

Analisa Risiko pada Rantai Pasok Industri Beton Pracetak Sistem Make-to-Order

The precast concrete supply chain has a long process and timeframe which often becomes an obstacle in its implementation. Like what happened to PT. X which is one of the precast concrete industrial companies located in the city of Semarang. In the supply chain work method at PT. X implements a make-to-order (MTO) system in which precast products will begin to be produced if they have received direct orders from consumers so that the finished time of precast products can adjust to the time of project implementation in the hope that the products are still in new and good condition. Long supply chain processes often cause problems or risks in their performance. To be able to find out what risks arise in the process of supply chain stages, it is necessary to have a risk analysis in the supply chain of the precast concrete industry. Risk analysis is carried out by first identifying the risks that may arise, then calculating the analysis by multiplying the probability and the impact of the risks that arise. Probability value and risk impact on PT. X was obtained from the results of questionnaires and interviews conducted with all employees. Based on the results of the analysis, it is known that the risk with the highest level is the "critical" level, namely at the "return" stage with the chance of returning the product to the factory due to precast products arriving with conditions not according to the standard order. Risk handling is carried out by "avoiding risk", namely by accepting the risk and immediately to be reproduced.

Investigating the Impact of Fly Ash on the Strength and Micro-Structure of Concrete during Steam Curing and Subsequent Stages

Steam curing, a common way of curing precast concrete, can greatly improve its 1-day strength. However, the thermal effect of prolonged high-temperature curing can negatively impact the concrete's performance, thus compromising production of precast products in cold regions. Fly ash (FA) is used as a supplementary cementitious material to improve part of the properties of concrete. In this paper, we investigated the effect of FA (10~30%) on the compressive strength and microstructure of manufactured sand concrete at the steam curing and later stages. Specifically, we analyzed the behavior of FA in the constant temperature phase under steam curing. Results indicated that the pozzolanic reaction of FA started to occur at 24 h of constant temperature curing. Early hydration under steam curing produces a large amount of Ca(OH)2, causing the pozzolanic reaction of FA to occur significantly earlier, and the high pH value of the solution and the fibrous mesh structure of the FA surface promote the pozzolanic reaction. The addition of 30% FA to manufactured sand concrete causes a significant reduction in early strength under steam curing, which is not beneficial to the formwork removal and tensioning of precast members. Notably, manufactured sand concrete with 20% FA under steam curing had the highest late strength. The filling effect of FA and the additional gel produced by the pozzolanic reaction would result in the reduction in large pore content, refinement of pore size, improvement of microstructural compactness, and increase in gel system strength. Therefore, the addition of 20% FA to the manufactured sand concrete can improve the long-term strength, which is beneficial to the production of precast beams in cold regions.

Effect of incorporating municipal solid waste incinerated bottom ash in alkali-activated fly ash concrete subjected to accelerated CO2 curing

The effect of incorporating bottom ash from municipal solid waste incineration (MIBA) as partial replacement for fly ash (FA) (0%, 15% and 30%) was studied on alkali-activated mortars under two curing environments: conventional climatic chamber (∼0.04% CO2) and carbonation chamber (5% CO2). The microstructural characterization showed that the use of MIBA resulted in a decrease of calcium silicate hydrate gel (C–S–H) and sodium aluminosilicate hydrate (N-A-S-H) observed as “rounded growths” worsening the macrostructural behaviour (compressive/flexural strength, ultrasonic pulse velocity, dynamic Young’ modulus, dry bulk density, shrinkage, depth of carbonation and porosity accessible to water). The accelerated CO2 curing stage produced high amounts of aragonite, observed as “needle-like” formations improving the macrostructural behaviour. One tonne of mixture with MIBA and CO2 curing could decarbonise approximately 3695, 7391 and 10163 m3 of air volume at the age of 7, 14 and 28 days. The combined substitution of FA with MIBA and CO2 curing can be a highly viable technique in plain precast products.

The FastCarb project: Taking advantage of the accelerated carbonation of recycled concrete aggregates

Recycled concrete aggregates (RCA) incorporate hydrates that can be carbonated. The FastCarb project aims to mineralize CO2 within RCA, improving the quality of these aggregates by the clogging of the porosity and finally decreasing the CO2 impact of concrete in structures. It has two main objectives: to optimize in laboratory conditions the accelerated carbonation process which can be transposed at an industrial scale at a suitable cost and to show that the process could be used in industrial conditions. This paper presents firstly the results obtained in laboratory conditions: it confirms that it is possible to store between 10 and 50 kg of CO2/t of RCA depending on several factors (natural carbonation, water content, temperature, size of RCA…) and that the treatment allows an improvement of the properties like the water absorption. The feasibility of accelerated carbonation has been also demonstrated by setting up two industrial-scale demonstrators. The first results without optimization showed a CO2 capture rate in the order of 3–4 %, i.e. 30 kg of CO2 per ton of crushed concrete. 80 t of carbonated RCA were produced and used to produce C25/30 and C45/55 concretes. The measurement of the main properties (performance in the fresh state, mechanical performance, and durability) shows that the use of the carbonated RCA doesn’t affect these properties. A variety of precast products (blocks, curbs, stairs) and parts of cast-in-situ structures (construction of walls) were fabricated showing the feasibility of using these aggregates in real situations. Finally, our project considers whether the accelerated carbonation process is environmentally acceptable and economically viable. The first results show that the distance of transport (by trucks) is a major factor and that transportation should be limited to maintain a positive impact of the accelerated carbonation (i.e. local sources of CO2 should be used). The LCA and the economic study confirm that the sand fraction of RCA is the most interesting material for the uptake of CO2. This is also interesting for a circular economy objective because recycled concrete sand is not easily used in concrete made with RCA.

ENVIRONMENTAL ASSESSMENT OF STORMPAV GREEN PAVEMENT FOR STORMWATER MANAGEMENT

This study evaluates the stormwater management potential of a green pavement technology for permeable road pavement with subsurface micro-detention storage (StormPav) from a water quality perspective. The system provides integration of permeable pavement with hollow spaces to attenuate peak discharge with design installation using precast products. The environmental assessment was gathered from field experiments to assess the water quality, mosquito breeding capability and infiltration rate in the StormPav. The water quality parameters were determined to assess environmental benefits, which are one of the components of sustainable development. The parameters consist of total suspended solids, pH and alkalinity and they showed identical results to other permeable pavement types. Larvae development was found as early as eight days in stagnant water in the cylindrical hollow section of StormPav. However, the StormPav showed a high permeability rate within 122.45 mm/hr to 168.12 mm/hr at subgrade soil of HSG A soils group with no stagnant water retained in the void section in less than two hours, which nullified the required retention time for larvae development. Hence, StormPav displayed a significant benefit in terms of environmental concern for a sustainable design invention in stormwater management with the presence of subsurface detention storage.

Fibre Mesh in Reinforced Slabs

Abstract: Fiber Reinforced Concrete is gaining attention as an effective way to improve the performance of concrete. Fibers are currently being specified in tunneling, bridge decks, pavements, loading docks, thin unbonded overlays, concrete pads, and concretes slabs. These applications of fiber reinforced concrete are becoming increasingly popular and are exhibiting excellent performance The usefulness of fiber reinforced concrete in various civil engineering applications is indisputable. Fiber reinforced concrete has so far been successfully used in slabs on grade, architectural panels, precast products, offshore structures, structures in seismic regions, thin and thick repairs, crash barriers, footings, hydraulic structures and many other applications. This study presents understanding srength of fibre reinforced conceret. Mechanical properties and durability of fiber reinforced concrete.

Microscopic observations of sites and forms of ettringite in the microstructure of deteriorated concrete

The determination of delayed ettringite formation (DEF) in hardened concrete relying simply on the identification of ettringite by electron microscopy or powder X-ray diffractometry can be imperfect because of the high risk of missing other possible deterioration phenomena. The presence of ettringite can be easily biased as an indication of DEF while the actual cause of deterioration is ASR. This paper identifies the deterioration causes and presents different ettringite formation factors based on the petrological observation results. The experiments conditions including depth of carbonation, mix proportions of concrete, curing temperature and others were considered. The deterioration of the samples seem to be correlated to ASR, except for the precast concrete product which presented DEF. In order to determine the deterioration causes and demonstrate the importance of petrological approach, different observations using the same methods were carried out on a concrete specimen blended with fly ash showing some cracks.

Adoption of alkali-activated cement-based binders (geopolymers) from industrial by-products for sustainable construction of utility buildings-A field demonstration

There is an increasing interest towards using sustainable construction materials for reducing the consumption of natural resources and maximising the utilisation of industrial waste. Alkali activated alumina silicates sourced from industrial by products are environmentally friendly as they leave a low carbon footprint. In this research, performance-based mixes were designed in which a competitive cementitious binder (0% Ordinary Portland Cement) comprising a blend of fly ash–GGBSGround granulated blast furnace slag as a solid precursor and mixture of sodium hydroxide and sodium silicate was produced and utilised in the construction of a utility building after a comprehensive study. As a result of using the Alkali activated fly ash and slag (AAFS) binder, the formation of reaction product sodium-/calcium-containing alumino silicate hydrate gel of type N-A-S-H and C-A-S-Hnetworkyielded high compressive strength, good bond strength with steel and lower deterioration of the matrix on sulphuric acid exposure, which were confirmed from various test results. In-situ precast products of both structural and non-structural elements, viz. blocks, bricks, window/door frame and slabs of various sizes, were fabricated using local materials andproper training was provided to skill the workers to produce them. Different grades of concrete were produced (M20–M40) and utilised in different stages of the construction of the utility building rural children care centre. The field trials, testing methods, monitoring of various stages of the constructions and challenges are presented in this paper. The findings of this research would help in designing suitable user-defined geopolymer mixes in construction and if this technology becomes ubiquitous in the construction industry, it can contribute to reducing the adverse effects of climate change due to environmental degradation.

The use of recycled aggregates in the construction sector: a scientific bibliometric analysis

The environmental problems associated with the construction sector have promoted the worldwide scientific community to pay attention to the use of recycled aggregates from construction and demolition waste. SciMAT and VOSviewer bibliometric tools have been applied in order to analyse, quantify and visualise the conceptual and social aspects of this scientific field, as well as its evolution between 1973 and 2019. The study of 843 scientific papers in this field has shown that the most important thematic area has been Recycling. In general, the common objective of the published papers was to study the efficient use of resources contained in construction and demolition waste due to their treatment to produce recycled aggregates, particularly for use in concrete. Likewise, some lacks have been observed in other areas of the analysed field, e.g. the use recycled aggregates in applications subject to less demanding regulations (mortars, precast concrete products, or green roofs).

Technical effectiveness of cement-based mortar for high-reflective building envelope through building energy simulations: preliminary results

In areas with high levels of solar radiation, decreasing the amount of solar energy absorbed by the building envelope is useful to reduce the need of air conditioning and "heat island" effects. Most high-reflective products, however, suffer from low durability. The COOL-IT project is developing an innovative high-reflective cement based mortar for precast products to be used as outer layer in buildings for both vertical and horizontal surfaces, or for road pavement. The mix design is aimed at increasing the durability of this cement-based component while retaining high reflectance to solar radiation. This paper presents the preliminary results of the project, based on the simulation of the energy demand of a residential building, intended as a support to optimize the proposed mixes. The model is analysed in three different locations in Italy, for one year of operation. This allows evaluating the trade-off of the energy demand between the winter increase and the summer reduction.

Structural grouting of load-bearing precast concrete elements: Issues and solutions

The purpose of this paper is to raise construction industry awareness regarding structural grouting of precast concrete projects in the United States. Incidents related to structural grouting have occurred with both precast concrete systems and other building systems. Designers, architects, owners, insurance carriers, and the construction industry in general are becoming increasingly aware of deficient grouting installation methods and verification procedures. Concerns include the timeliness of grout installation during the erection process, the lack of grout on some components of finished projects, and the poor quality of installed grout. These concerns pertain to horizontal connection joints of critical load-bearing elements between foundations and precast concrete columns and walls, stacked precast concrete columns, and stacked precast concrete walls. Current building codes and standards provide no requirements and limited guidance for the installation or special inspection of these critical horizontal joints. In an effort to address this gap in building codes and standards, as it specifically relates to precast concrete structural products, some precast concrete producers and erectors are implementing several strategies and new procedures, as noted and further developed in this paper.

Effect of calcined kaolin clay on mechanical and durability properties of pet waste-based polymer mortar composites

This study attempted to prepare a novel polymer mortar (PM) composite comprising unsaturated polyester resin (UPR) derived from polyethylene terephthalate (PET), as a replacement for cement; calcined kaolin clay as a filler; and silica sand as an aggregate. The UPR resin was synthesized by depolymerizing PET waste using propylene glycol and modifying it with styrene (UPR1) and methyl methacrylate (UPR2) monomers. Most previous studies have focused on the effect of kaolin clay filler on the properties of Portland cement concrete, whereas the effect of kaolin clay filler and sand grading on the properties of UPR resin PM has not been examined. In this study, the effects of UPR1 (UP:styrene) resin, UPR2 (UP:MMA) resin, calcined kaolin clay, and silica sand (zones I, II, and III) on the mechanical and durability properties of a PM composite were investigated. The polymer mortar (PM) mixture design was optimized through the design of the experiment (DOE) using Taguchi and ANOVA analyses. The compressive, tensile, and flexure strengths of the UPR2 PM formulation increased by 19.48, 25, and 28.21 %, respectively, compared to UPR1 PM. In addition, UPR2 PM with 20 % kaolin clay and sand (II) exhibited a decrease in water absorption, mass loss, and loss in compressive strength by 28.20, 15.90, and 7.31 %, respectively, compared to PM containing 18 % kaolin filler and sand (I). Moreover, the experimental results indicated that sand grading significantly influenced the properties of the UPR PM composite. The UPR resin prepared from waste PET and modified using MMA can be successfully used as a binder in PM composites to prepare mortar for interior decoration, repairing, grouting, and lightweight precast products in construction applications.

Recycled Precast Concrete Kerbs and Paving Blocks, a Technically Viable Option for Footways.

The linear economy paradigm in place to date has to be seriously challenged to give way to a new school of thought known as the circular economy. In this research work, precast kerbs and paving blocks made with recycled concrete (RACC-mixture) bearing 50 wt% mixed recycled aggregate (masonry content of 33%) and an eco-efficient cementitious material as 25 wt% conventional binder replacement were evaluated to assess their intrinsic potential to replace traditional raw materials, in keeping with circular economy criteria. Therefore, precast products were subjected to mechanical strength, durability and microstructure tests and were compared to conventional concrete units (CC-mixture and commercially available precast elements). Although a class demotion was observed for water absorption and some decreases in flexural strength (26%), splitting tensile strength (12.8%) and electrical resistivity (45%) and a lower class water absorption were registered, and the recycled mixture also exhibited a greater performance in terms of compressive strength (6%), a better abrasion resistance classification and a comparable porosity and microstructure, which ensures a good concrete durability. In any case, the results showed that precast pieces were European standard-compliant, thus supporting the viability of the mixed recycled aggregates and eco-efficient cementitious replacement in footways.

Recycled Aggregates from Construction and Demolition Waste in the Manufacture of Urban Pavements.

Construction and Demolition Waste (CDW) is among the largest waste streams in the world. Therefore, within the Circular Economy concept, there is a growing interest in its reuse. The purpose of this work was to study the use of recycled aggregates (RAs) obtained by a specific separation method from CDW, replacing natural aggregates (NAs) in the manufacture of precast concrete elements, such as kerbstones and paver blocks. The physical and technological properties of precast products formulated with RAs were analysed in accordance with current regulations, comparing them with those of commercial products manufactured with NAs. The results indicated that partial or total substitution of NAs by RAs increased the water absorption and apparent porosity values of the precast elements while reducing the bulk density and compressive strength. However, all units manufactured with RAs showed breaking load values higher than the minimum required by EN 1338 and, in some cases, slightly higher average tensile strength values than the reference material. In addition, some of the compositions including RAs gave rise to pieces that, according to their flexural strength, were classified as class 1 and marked S in accordance with EN 1340. According to abrasion resistance, in most cases, the precast elements are classified as Class 4 and I (≤20 mm). Finally, precast concrete produced from RAs satisfies the tolerance requirements for classification as class 3 (≤1.5 kg m−2). Therefore, it could be suitable for use in high pedestrian or traffic areas.