Sustainable Construction Materials Research Articles

Alkali-activated composites with synthetic fibers and recycled aggregates: a study of mechanical properties

This study examines the potential for enhancing alkali-activated composites (AACs) through the incorporation of a blend of meta-zeolite (MZ) and slag, reinforced with synthetic fibers and incorporating aluminum sludge (AS) and recycled concrete aggregate. AACs were activated with sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃) in varying ratios and molarities (8M to 14M). The optimal mix, comprising 50% MZ and 50% S at 12M NaOH with 30% AS, exhibited notable enhancements in mechanical properties. Specifically, the addition of 0.5% basalt fibers resulted in a 7.26% increase in compressive strength and a 24.15% enhancement in flexural strength. These findings underscore the potential of MZ-S-based AACs, enhanced with aluminum sludge and basalt fiber, to develop advanced, sustainable construction materials. The study underscores the significance of optimizing material ratios and reinforcement strategies to achieve superior performance, thereby contributing to the development of environmentally friendly building solutions that align with contemporary standards.

Compressive Strength of Paver Block Using Rubber Tyre Waste and Bamboo Fibre Under Extreme Conditions

The utilisation of by-products in paver block production has gained significant attention due to its potential in environmental condition. This research investigates the effect of incorporating rubber tyre waste and bamboo fibre into the fabrication of paver block on compressive strength, water absorption, density and ultrasonic pulse velocity tests. This research comprises two batches of paver blocks fabrications following a 1:2:3 ratio(cement: fine aggregate: coarse aggregate). Batch 1 involves the fabrication of paver blocks by incorporating varying percentages of rubber tyre waste (0, 10, 20, 30, 40 and 50%), which replace a portion of the sand (referred to as rubber paver block). In Batch 2, various dosages of bamboo fibre, used as a reinforcement material were added to the paver block containing 40% rubber tyre waste, which are referred to as rubber-bamboo fibre paver blocks. Nevertheless, the compressive strength of the rubber-bamboo fibre paver blocks was further examined under two simulated environmental conditions: (1) air and dry cycle, and (2) wet and dry conditions. These conditions aim to assess the block’s resistance to temperature fluctuations, moisture effects, and theiroverall durability. The strength of the paver blocks decreases with the additional inclusion of rubber tyre waste. While the utilisation of 0.3% bamboo fibre has shown improvement in its strength performance compared to 0.2% and 0.4%. It suitable to used for non-loading structural applications that require strength below 25 kPa. This study was able to promote sustainable and green construction materials for paving applications through the efficient recycling of waste materials. It aligns with Sustainable Development Goals (SDG) 9 (Industry, Innovation, and Infrastructure) and 11 (Sustainable Cities and Communities).

Assessing the durability properties of sandcrete blocks incorporating iron filings as fine aggregate

The rising costs of construction materials, particularly sandcrete blocks, necessitate the exploration of cost-effective alternatives. This study examines the feasibility of incorporating iron filings (IF), a by-product of metal workshops, into hollow sandcrete block production and assesses their performance under harsh conditions. IF was used to replace 5–20 % of the fine aggregate component in blocks at a step of 5 %, mixed at a 1:8 ratio, and sized at 450mm×150mm×225mm. The study evaluated the impact of acidic exposure on the density, sorptivity, and compressive strength of these blocks, as well as their sensitivity to elevated temperatures. The results showed that IF blocks had significantly lower density than non-IF blocks, especially those cured with H₂SO₄. For instance, blocks with 15 % IF and cured in 0.3 mol/dm³ H₂SO₄ had a 13.9 % reduction in density. Despite higher acid concentrations, IF samples demonstrated better sorptivity, absorbing water more slowly than non-IF samples. However, exposure to acidic media reduced compressive strength by 1.9 %–47.8 % for HNO₃ exposure and 0.5 %–42.4 % for H₂SO₄ exposure. None of the acid-exposed blocks met the minimum standards for load-bearing (2.5 MPa) or non-load-bearing walls (2.0 MPa) as per NIS standards. Furthermore, the sensitivity of IF sandcrete blocks to changes in compressive strength under elevated temperatures decreased by almost half, from 0.026 to 0.014 MPa/°C, as the curing period increased from 7 to 28 days. Blocks with 5–15 % IF showed improved compressive strength at temperatures below 150 °C, but strength declined sharply beyond this temperature. By utilising IF, a readily available waste material, the implications of the study are significant for promoting a circular economy in the construction industry. However, the performance of the blocks against durability concerns needs to be improved further before integrating such waste materials into developing sustainable and resilient construction materials

Effect of steel fiber content on failure strength and toughness of UHPC-CA at low temperature: An experimental investigation

As a potential and sustainable construction material, ultra-high performance concrete containing coarse aggregate (UHPC-CA) finds promising applications in engineering constructions, particularly in severe cold regions. This study conducts an experimental study to investigate the influence of fiber content (ranging from 0.0 % to 3.0 %) on the uniaxial compression and splitting-tension failures of UHPC-CA across a temperature range of −90 °C∼20 °C. Through microstructure analysis, the underlying mechanisms and quantitative analysis behind the low-temperature enhancement effect and fiber reinforcement effect on the nominal strength and toughness of UHPC-CA were elucidated. The test results show that as the temperature drops from 20 °C to −90 °C, nominal strengths of UHPC-CA monotonically increase (with a maximum increase 88.1 % for splitting-tension strength while 72.6 % for compressive strength), but the compressive toughness reduces with a maximum decrease 54.6 %. Additionally, the incorporation of steel fibers can enhance the nominal strengths and compressive toughness, exhibiting the fiber reinforcement and toughening effects. Compared to the UHPC matrix, all the increases for nominal strengths and compressive toughness of UHPC-CA with 2.0 % steel fibers at room temperature are higher than those at low temperatures, demonstrating that the decreasing temperature can weaken the fiber reinforcement and toughening effects, which may attribute to fact that the formation of microcracks (due to the expansion of phase change of pore ice) in the surface between steel fiber and UHPC matrix at low temperatures, as observed in the microscopic test. However, as the fiber content exceeds 2.0 %, the splitting-tension strength decreases, thereby it is recommended that the optimal steel fiber content is around 2.0 % for UHPC-CA at low temperatures. Finally, considering the quantitative effects of steel fiber characteristics and temperature, the empirical prediction models for cryogenic nominal strengths were proposed and verified, which can well predict compressive and splitting-tension strengths of UHPC-CA with various steel fiber contents at low temperatures. This study can provide an experimental data reference for the safety design of UHPC structures and contribute to promoting the application of UHPC-CA in the engineering construction of cold regions.

Mechanical properties of basalt macro fibre reinforced geopolymer concrete

Growing public environmental awareness leads to an increased focus on utilizing green and sustainable materials in infrastructure construction. Geopolymer concrete (GPC) and basalt macro fibres (BMFs) are promising construction materials due to their eco-friendly merits and excellent mechanical properties. In this study, a new type of BMFs reinforced GPC (BMF-GPC) was developed, and the compressive and flexural properties of BMF-GPC were investigated. The effects of BMF content and length on the mechanical properties of GPC were studied. It was found that with the addition of 2 % BMFs, the compressive and flexural toughness (energy absorption capacities) of GPC were greatly enhanced by up to 126 % and 965 %, respectively. Increasing the content and length of BMFs resulted in favourable outcomes for strain softening of GPC under compression and post-cracking behaviour of GPC under flexural loads, whilst having limited effects on the modulus of elasticity and flexural strength. Additionally, an analytical model was proposed to predict the compressive stress-strain behaviour of BMF-GPC, which could be used for the design of BMF-GPC structures.

Optimizing toughness and cost-effectiveness in one-part geopolymers via fiber reinforcement: A comprehensive investigation of PVA, PE, and glass fibers

This study explores developing and characterizing a one-part geopolymer, an innovative and sustainable construction material. The effects of incorporating polyvinyl alcohol (PVA), polyethylene (PE), and glass fibers (GF) on the toughness of slag and fly ash-based one-part geopolymer mortars were investigated through compressive, three-point flexural, and four-point bending tests. The findings demonstrate that fiber incorporation reduces fluidity and compressive strength due to increased porosity, lower elastic modulus of fibers, and weak interfacial bonding. However, fibers significantly enhance damage resistance and toughness via crack bridging and load transfer mechanisms. Formulations with 2 % PVA fibers and combinations of 1 % PVA with 1 % PE fibers and 1 % PVA mixed with 0.5 % PE and 0.5 % GF demonstrate excellent toughness. Notably, the latter two fiber blends achieve 14 % and 10 % cost reductions, respectively, compared to using only PVA fibers, making them economically viable for large-scale applications. Scanning electron microscopy and X-ray diffraction provided insights into the toughening mechanisms, including crack bridging, fiber pull-out, and enhanced stress distribution within the geopolymer matrix. Digital image correlation techniques further elucidated the fibers' role in improving the post-cracking behavior and structural resilience under load.

Elaborating the 3D microstructural characteristics and strength softening mechanical mechanism of fiber-reinforced recycled aggregate concrete

Recycled aggregate concrete (RAC) is a sustainable and low-carbon construction material, but it tends to have inferior physico-mechanical properties compared to natural aggregate concrete. This study aims to enhance these properties to make RAC a viable alternative for broader construction applications. By incorporating steel fibers (SF) and polypropylene fibers (PPF) into RAC, the mechanical properties, particularly crack resistance and post-peak strength softening, were significantly improved. Extensive low-cycle loading tests were conducted to assess the strength softening behavior and energy dissipation capacity. The results showed that fibers increased post-peak strength softening resistance by up to 30 % for SF and 25 % for PPF. Proposed strength softening models based on residual strain accurately predict the effects of fiber dosage on the composite’s properties, providing a technical foundation for RAC engineering applications.

Characteristics of concrete incorporating construction and demolition waste aggregate and post-consumer tires rubber and steel fibers

This study aims at investigating the performance of Portland cement concrete incorporating construction and demolition waste aggregate in conjunction with rubber and steel fibers from post-consumer tires. Eight concrete mixes were prepared and tested. In these, natural coarse aggregate (NCA) was replaced by 100 % recycled concrete aggregate (RCA) and/or 20 % and 40 % rubber coarse aggregate (RuCA). The contribution of post-consumer tire steel fibers (PCTSF) to the behavior of the various recycled concrete mixes was also examined. The axial compressive stress–strain, flexural stress–deflection, and splitting tensile strength behaviors together with the dry density, porosity and rapid chloride penetration for all concrete mixes were investigated and compared. The results indicated that increasing the replacement levels of RuCA resulted in a decrease in concrete strength, although the decrease was less pronounced in the concrete mixes with RCA than in mixes incorporating NCA. Specifically, the reductions in compressive, tensile and flexural strengths were respectively as much as 6.6 %, 12.9 % and 14 % less in the mixes containing RCA. Also, the addition of PCTSF substantially mitigated the reductions in strength and, more significantly, the deflection at peak stress was increased by up to 664 %. Furthermore, incorporation of these fibers maintained up to 47 % of the flexural peak strength of the concrete mix at 4 mm deflection in the post-peak region. Additionally, the porosity of the concrete mixes ranged from 6 % to 12 %, placing them in the high-durability concrete category. The dry density exhibited an inverse relationship with the rubber aggregate content, resulting in a reduction of up to 10.2 % compared to the control mix. Hence, utilizing a substantial volume of post-consumer tire materials in recycled-aggregate concrete mixes is envisaged as an ideal choice in construction applications where lower concrete rigidity is desired, for example in seismic or vibrated zones. The approach also aligns with the increasing emphasis on sustainable construction materials.

Fly Ash-Based Geopolymer Concrete

This paper investigates the properties and applications of fly ash-based geopolymer concrete (GPC) using sodium hydroxide (NaOH), sodium silicate (Na2SiO3), and coarse and fine aggregates. The focus is on understanding the chemical interactions, mechanical properties, and durability of this sustainable construction material. Additionally, results from a rebound hammer test are discussed to evaluate the in-situ strength over time. Keywords : - Fly Ash, Geopolymer Concrete, Sodium Silicate, Sodium Hydroxide, Sustainable Construction, Mechanical Properties, Durability

Layer-over-Layer Electrostatic Self-Assembly of Bioresourced Compounds in Thermoreversible Polylactide Gels as an Effective Approach to Enhance the Flame Retardancy of Aerogels.

Polylactide is a high potential polymer that can satisfy the growing demand for sustainable and lightweight materials in construction, packaging, and structural applications. However, their high flammability poses a serious concern. Herein, with the aid of solvent exchange and noncovalent interactions, poly(l-lactide) (PLLA) thermoreversible gel was modified with sodium alginate (SA), chitosan (CS), and phytic acid (PA) via a layer-over-layer approach. Freeze-drying of the modified hydrogel furnished a highly flame retardant aerogel with shape stability and no shrinkage. The modified PLLA aerogel (PLLA@SA@CS@PA) exhibited self-extinguishment of flame, the highest limiting oxygen index of any porous polylactide (∼32%), and a tremendous reduction in flammability parameters such as the heat release rate, heat release capacity, total heat release, etc. A comprehensive mechanism of flame retardancy was proposed. This work provides a sustainable strategy for the flame retardant modification of semicrystalline polymer-based aerogels and is expected to expand their practical applications in various industrial sectors.

Reimagining resources policy: Synergizing mining waste utilization for sustainable construction practices

To address the urgent need for sustainability, this paper provides a critical discussion and serves as a pivotal resource for stakeholders in the mining and construction sectors. It advocates repurposing mining waste into concrete aggregate, promoting eco-friendly practices. The paper conducts a thorough review of recent developments, technological innovations, and methodologies to showcase mining waste's potential as a sustainable construction material. Highlighting more than a decade of research, our analysis reveals significant environmental, economic, and practical benefits, such as reduced ecological footprints through waste minimization and resource conservation, alongside cost-effective material alternatives. This investigation offers an in-depth look at these advantages and sparks essential discussions about incorporating advanced recycling technologies into conventional construction workflows. Promoting circular economy principles, the study underscores the dual gains: lessening environmental impact and progressing towards resource efficiency. Aiming to alter industry perceptions and practices, the work encourages a shift towards environmental stewardship and innovation. Ultimately, this paper aims not only to disseminate knowledge but also to motivate action. It provides readers with the necessary insights to lead a transition towards more sustainable industry norms, thus establishing a new benchmark for addressing sustainability challenges with creativity and collective effort.

Long-term durability of discarded cork-based composites obtained by geopolymerization

Geopolymers are amorphous aluminosilicate inorganic polymers synthesized by alkaline activation characterized by a lower carbon footprint, greater durability, and excellent mechanical properties compared to traditional concrete, making them promising building materials for sustainable construction. To develop sustainable lightweight geopolymer-based building materials useful as fire resistant thermal insulation materials, we added 5 and 10 wt% of discarded cork dust, a readily available industrial by-product, to metakaolin before and after the alkaline activation with sodium hydroxide 8 M and sodium silicate solutions. We followed the chemical, microstructural, antibacterial, and physical properties of the resulting composites for up to 90 days in order to monitor their long-term durability. The presence of cork does not interfere with the geopolymerization process and in fact reduces the density of the composites to values around 2.5 g/cm3, especially when added after alkaline activation. The composites resulted in chemically stable matrices (less than 10 ppm of cations release) and filler (no hazardous compounds released) with a bacterial viability of around 80%. This study provides valuable insights into the tailoring of discarded cork-based composites obtained by geopolymerization with a porosity between 32 and 48% and a mechanical resistance to compression from 15 to 5 MPa, respectively, suggesting their potential as durable interior panels with low environmental impact and desirable performance.

Development of red mud based sintered artificial aggregates with various industrial wastes

Red mud (RM) has drawn a lot of attention in the search for potential uses in the production of sintered artificial aggregate from industrial waste products. The main objective of the study is to produce an RM-based sintered artificial aggregate (SAA), with several blends (binary, ternary, and quaternary) using various industrial wastes. This study includes assessing the mechanical and physical properties of SAA as well as the sintering parameters in order to determine the appropriate material mix ratio. To achieve these objectives, a comprehensive experimental approach was adopted. A total of 35 different mixtures were formulated by incorporating various industrial wastes as binders and sintering additives. The green pellets were preheated at 105 °C for 24 h, and consecutively sintered at different temperatures, namely 700 °C, 900 °C, 1100 °C, and 1150 °C with a duration of 30 min. A compressive strength test was performed in order to find the mechanical property of SAA similarly water absorption and bulk density tests were conducted to find the physical properties of SAA. To characterize the SAA, scanning electron microscope analysis (SEM), X-ray diffraction (XRD) and energy dispersive x-ray analysis were conducted, and also data analysis was performed using Artificial Neural Network (ANN) tools, yielding accurate predictions. Successfully best compressive strength low water absorption SAA was produced. The best material weight mix ratio for the production of SAA was identified as (A18) RM: Fly Ash: Waste Glass Powder; 78:10:12. Out of all blends the ternary blend (A18) SAA exhibited impressive properties after 30 min of sintering at 1150 °C: high compressive strength of 22.92 MPa, water absorption of 4.26%, and bulk density of 1296.12 kg m−13. This was made possible by the high amount of Al2O3, SiO2, in the combination of fly ash, and waste glass powder with RM. SEM and XRD analysis also confirmed that the (A18) SAA achieved the best compressive strength, and low water absorption due to turning the surface and core area into a solid, reduced internal pores and formed quartz, and hematite phases. The findings of this study serve as a foundation for future work and pave the way for the development of sustainable construction materials.

Preliminary Development of Mycelium Based Sustainable Construction Material Out of Agricultural Waste

Preliminary Development of Mycelium Based Sustainable Construction Material Out of Agricultural Waste

Enhancing Geopolymer Mix Optimization: Integration of the Plackett–Burman Method and Response Surface Methodology for Sustainable Construction Materials

Enhancing Geopolymer Mix Optimization: Integration of the Plackett–Burman Method and Response Surface Methodology for Sustainable Construction Materials

Development of a New Method for Assessing Project Risks in Sustainable Building Construction Projects in Developing Countries: The Case of Jordan

Sustainable buildings contribute significantly to achieving sustainable development and provide many benefits. However, sustainable building construction projects are riskier than traditional construction projects. Thus, this research aimed to identify and assess the risks in sustainable construction projects in Jordan based on their probabilities of occurrence and impacts on time and cost. For this purpose, a literature review and structured interviews were performed to identify the risks. Additionally, questionnaire surveys were conducted, and the relative relevance index and analytic hierarchy process were utilized to assess the probabilities and impacts of these risks on time and cost. After that, a focus group discussion was conducted. According to the the risks’ probability and impacts on time and cost, the top-scoring risks include changes to the original design, budgeting inaccuracies owing to a lack of experience with sustainable building projects, additional costs incurred as a result of the use of sustainable building construction materials and equipment, inadequate or inaccurate sustainable design information, insufficient funds from clients, inadequate project planning for a sustainable building project, a tight project schedule for a sustainable building project, and insufficient identification of sustainable construction’s scope. This research contributes to the body of knowledge and practice by providing a novel integrated method for assessing risks in sustainable building construction projects in Jordan.

Nano-fly ash and clay for 3D-Printing concrete buildings: A fundamental study of rheological, mechanical and microstructural properties

Three-dimensional printing concrete (3DPC) represents a recent innovation in the construction and building research sector and novel approach to building techniques. The focus of this study is to develop an environmentally sustainable cementitious composite optimized for 3D printing applications. The research involved preparing 3D printing mixtures that comprised of 50 % Portland Cement (PC), 50 % Colorobia Clay (CC), and varying contents (0 % 5 %, 10 %, and 15 % by weight of cement) of Nano-Fly Ash (N-FA) under standardized printing parameters. The fresh mixture's properties have been evaluated and the mechanical and microstructural properties of the printed samples were assessed, subsequently. The findings demonstrated that incorporating N-FA into the cementitious mixes enhanced their flowability and workability. Specifically, the mix containing a low N-FA concentration of 5 wt% exhibited superior compressive strength relative to the other formulations. Additionally, flexural strength assessments indicated a minimum increase of 39.4 % across all mixes compared to the control 3D-printed mixture. Microstructural investigations by SEM imaging validated the anticipated formation of hydration products, namely calcium-silicate-hydrate (CSH) and ettringite, facilitated by the synergy between clay and fly ash. The t-statistical analysis further corroborated that the inclusion of N-FA significantly bolstered the strength attributes of the mixes designated for 3D printing. In conclusion, this study underscored the efficacy of integrating clay as a sustainable construction material within 3D printing applications. The utilization of clay-cement mixes, augmented with N-FA, emerged as a viable strategy to enhance the sustainability and reduce the carbon footprint of construction practices.

Influence of GGBFS and alkali activators on macro-mechanical performance and micro-fracture mechanisms of geopolymer concrete in split Hopkinson pressure bar tests

With superior low-carbon emission and low-resource consumption, geopolymer concrete (GPC) is receiving increasing attention as an optimal alternative to conventional building materials for cleaner and sustainable construction. However, the practical application of GPC poses great challenges since its dynamic mechanical performance remains far from well understood. In this study, via a split Hopkinson pressure bar (SHPB) system, a series of dynamic compression tests at strain rates of 45 s-1 to 150 s-1are conducted on GPC specimens with different alkaline activators (AAS)-binder mass ratios (i.e., 10%, 15%, 20%, and 25%) and ground granulated blast furnace slag (GGBFS)-binder mass ratios (i.e., 0%, 30%, 50%, 70%, and 100%). Our testing results comprehensively explored the influence of mix proportions and loading rates on the dynamic mechanical performance of GPC, including the dynamic strength and deformation characteristics, energy evolution and utilization, and progressive failure behavior. The permanent strain, energy dissipation density, and dynamic strength of GPC specimens generally increase with increasing strain rate, while the average fragment size decreases. Under higher loading rates, GPC specimens are featured by denser microcracks, shorter propagation paths, and more prominent stepwise fractures. In addition, GGBFS has a greater impact on dynamic strength, strain rate sensitivity, and energy utilization than AAS. Micro-fracture effect of GPC with different mix proportions is investigated. An appropriate content of alkaline activator (i.e., 20%) and higher GGBFS content (i.e., 100%) promotes the binder depolymerization-aggregation reaction, reduces initial defects inside concrete specimens, and facilitates a more compact block structure.

Enhancing alkaline resistance of concrete using alccofine and metakaolin in mineral admixtures of sustainable development

Addressing the need for sustainable construction materials that minimize environmental impact and reduce CO2 emissions, particularly in OPC compositions. Assessing alccofine and metakaolin in OPC compositions to determine their impact on concrete strength, durability, and microstructure in alkaline environments for sustainable material development. Experimental investigation involved incorporating alccofine and metakaolin into OPC concrete mixes, creating binary and ternary blended systems. Modified concrete specimens were subjected to various alkaline attacks using diluted solutions of magnesium sulfate (MgSO4), sodium sulfate (Na2SO4), and sodium chloride (NaCl) both individually (5%) and in combination (2.5%), resulting in significant improvements in concrete strength and durability. The modified concrete exhibits enhanced resistance to alkaline attacks, reduced weight and compression strength loss, and superior performance in Base Durability Factor (BDF) and Base Attack Factor (BAF) compared to conventional specimens. Scanning electron microscopy (SEM) study of the altered concrete’s microstructure shows that it has a densely packed microstructure, which increases its load-bearing capability. Mineral admixtures aid pore clogging, leading to denser, more alkali-resistant concrete due to finer particles. Notably, Alccofine and metakaolin offer effective solutions for sustainable construction materials, aiding in the decrease of CO2 releases during cement production and addressing critical gaps in sustainable material development.

Unveiling physico-mechanical and acoustical characteristics of fly ash geopolymers through the synergistic impact of density and porosity

This paper investigates the physico-mechanical and acoustic properties of fly ash geopolymers via casting and pressing methods. The existing research lacks comprehensive insight into the relationship between variations in geopolymer density and their impacts on both physico-mechanical properties and sound insulation and absorption capabilities. Geopolymers, as sustainable construction materials, are pivotal in mitigating noise and providing structural strength. To surpass these limitations and achieve either higher or lower densities in geopolymers, alternative approaches are necessary. Casting (non-foamed and foamed with 1.0, 2.0 and 3.0 foam-to-geopolymer paste ratio) and pressing methods were employed to produce a range of geopolymer densities between 1400 kg/m3 – 2200 kg/m3. The pressing method produced a highly dense geopolymer with an excellent compressive strength of 116 MPa. While the lightest geopolymer produced by adding a foaming agent had a compressive strength of 13 MPa. Good sound transmission loss (66.1 dB) was achieved by highly dense pressed geopolymers. Highly porous geopolymers achieved an excellent sound absorption coefficient of 0.79. The density variation and preparation methods greatly affected the pore size and distribution which subsequently affected the acoustical properties of the geopolymers. Manipulating the density and porosity of the geopolymers is essential for creating spaces with optimal acoustics to meet building codes and noise control regulations.