Portland Cement Association Research Articles

Improved mechanistic performance of natural rubber latex modified pavement concretes in sulfate environments

ABSTRACT Sulfate attack causes significant degradation in the concrete matrix, including softening, expansive cracking, and other disruptive processes. This research examined the impact of incorporating a Natural Rubber Latex (NRL) additive on the mechanical and durability improvement of concrete pavements. The study evaluated the influence of water to cement (w/c) ratios and dry rubber to cement (r/c) ratios on compressive and flexural strengths, as well as flexural fatigue characteristics, before and after immersion in a 5% sulfate solution at various intervals. Optimal r/c ratios for the highest flexural strength and fatigue life were 0.58, 1.16, and 1.73 for w/c ratios of 0.3, 0.4, and 0.5, respectively. The highest durability was achieved at an r/c ratio of 5.78, resulting in a compressive strength loss of 4.2–7.7 times lower compared to that of normal concrete, hence extending the service life against severe environment. The fatigue model equation proposed by the Portland Cement Association (PCA) was utilised to predict the fatigue life of both normal and NRL-concretes. The outcome of this research will lead to a fundamental knowledge in the development of a design guideline of sustainable concrete pavements, and eventually promote the usage of NRL, which is abundant in Southeast Asia, including Thailand.

Durability of clayey soil stabilized with calcium sulfoaluminate cement and polypropylene fiber under extreme environment

Calcium Sulfo-Aluminate Cement (CSAC) is gaining interest among researchers, consultants, engineers, and environmentalists as a prospective replacement of Ordinary Portland Cement (OPC) across many construction industries. The main reason is that the production of CSAC generates a lower carbon footprint as compared to OPC cement production. Other benefits of CSAC include quick bonding & strength development, and less shrinkage. Many studies are available and ongoing on the advantages and limitations of CSAC in concrete. However, only a few studies are available on its application in soil stabilization. Therefore, the efficiency of CSAC for soil stabilization is a topic of discussion in geotechnical engineering. In this research, a locally sourced highly compressible clayey soil was stabilized with different combinations of CSAC and polypropylene fiber (e.g., 5.0%, 7.5% & 10.0% of CSAC and 0.5% & 1.0% polypropylene fiber), and its effectiveness was observed and evaluated in terms of durability (Wetting-Drying and Freezing-Thawing tests) against extreme environments and also checked Unconfined Compressive Strength (UCS) as per American Society of Testing and Materials (ASTM) guidelines. The findings of this research are evaluated in terms of percentage of soil loss, change in moisture content and volume, and loss of strength after durability exposure. Moisture content and bulk unit weight were determined after each stage in the Freezing-Thawing durability cycles. Samples prepared with 10.0% of CSAC and 1.0% of fiber were able to survive all durability cycles of Wetting-Drying with PCA (Portland Cement Association) soil-loss percentage criteria. On the other hand, samples prepared with 10.0% cement with 0.5% as well as 1.0% fiber were able to survive all durability cycles of Freezing-Thawing with PCA soil-loss percentage criteria. These survived samples showed a significant amount of unconfined compressive strength even after being subjected to these durability cycles.

Long-term field monitoring of slabs-on-ground reinforced with GFRP bars

The current design of GFRP bar-reinforced slabs-on-ground, according to ACI 440.1R-15 is based on an empirical equation derived from the design of steel-reinforced concrete slabs-on-ground, developed based on the subgrade drag equation proposed in Portland Cement Association code (1990). ACI 440.1R-15 explicitly stipulates that field performance data from the application of FRP bar-reinforced slabs-on-ground is required to validate the equation. This paper reports the experimental outcomes of a comprehensive study on the long-term field monitoring of eight large-scale slab-on-ground specimens. Slabs of plan dimensions 6000 × 1100 mm2, resting on a lean concrete subbase over a compacted soil subgrade and exposed to harsh ambient environment, were monitored for 525 days to study rebar and concrete strain development and concrete cracking. The exposed ambient environment was characterized by averages of 41.7 ℃ with RH 12.8% in summer and 9.5 ℃ with RH 87.7% in winter. The major parameters of the study are reinforcement types (ribbed GFRP, sand-coated GFRP, and ribbed steel), reinforcement spacings (200 mm and 300 mm), slab thicknesses (100 mm and 200 mm), and the presence of a contraction joint. It was observed that all GFRP bar-reinforced slabs developed a transverse mid-panel shrinkage crack within the first 18 days of casting. The maximum average crack widths over the long-term were within the ACI 440.1R-15 and AASHTO LRFD code limit of 0.7 mm, and the maximum strains in rebars in the vicinity of the cracks did not exceed 12.4% of the ultimate strains of the bars. Decreasing the slab thickness from 200 mm to 100 mm did not affect the development of cracking or strain evolution. The presence of a saw-cut contraction was effective in localizing the cracking location.

EVALUATION AND STRUCTURAL MODELING OF 200 m3 CIRCULAR TANK SUPPORTED WITH SOFTWARE APPLICATION

Permanent constructions in drinking water systems are of primary use in the development of a population. The objective of this work was to perform a non-destructive surface evaluation and structural modeling of the 200 m3 supported tank under conditions in the town of Pomata, Peru. A sclerometer was used to determine the concrete strength of the circular wall and the lower base of the old tank. The structural evaluation of the old tank was carried out by applying the design tables of the Portland Cement Association (PCA) and modeling with reliable structural calculation software; likewise, in the old tank the spectral dynamic analysis was carried out with the design parameters of the Peruvian National Construction Regulations, structural standards E.020, E.030, E.050, E.060 and ACI 350-01, ACI 350-06. The same results were obtained for the annular and bending stresses in a static analysis using the PCA design tables. According to the technical evaluation of the old tank, which has a useful life of more than 20 years of use in the potable water system; a new tank with the same storage capacity and in the same location was proposed; in the static and dynamic spectral analysis the PCA tables and modeling with software were used; achieving similar results in both tanks. It was demonstrated that demolition is necessary.

Development of geopolymer-based composites for geothermal energy applications

This paper intends to develop geopolymer-based composites for geothermal energy applications. Both silicon carbide (SiC) sand and SiC powder were applied to optimize the thermal and mechanical behaviours of geopolymer. The flexural and compressive strength of geopolymer composites with different mix designs were investigated. A novel test set-up to record the thermal conductivity were designed, and the thermal behaviours of geopolymer composites with different mix design were tested. It was found that the proper addition of SiC powder is conducive to the compressive and flexural strength of geopolymer composites, while the influence of SiC particles is insignificant. The relationship between flexural and compressive strength of geopolymer composites was also investigated, and it was found that the Portland cement association (PCA) code reached the best fitting precision. With the addition of SiC materials, the maximum thermal conductibility of geopolymeric composite can be as high as 5.35 Wm−1K−1, which is about five times higher than conventional cementitious composite. The combined application of SiC powder and SiC particle is practical to increase the thermal conductivity of geopolymer, making it a suitable material for geothermal energy applications. Based on the numerical model, it was concluded that the addition of silicon carbide is beneficial to the heat exchange rate of the energy pile and improves the heat utilization efficiency of the energy pile.

Technical Analysis of Soil Cement as A Construction Material Applied in Rural Houses

The project reveals the properties of soil cement as a construction material in rural houses. The context of this research was in Pilcomayo district, Huancayo, Peru, due to the high abundance of poor constructions without any security or comfort for the inhabitants of the area. In the experiment, the technical analysis of the soil cement was carried out with doses of 5%, 9%, 13%, 17% and 21% of cement, applying tests of Granulometry, Compaction, Compression and Durability established by the Portland Cement Association. It was found that the soil of the district has an efficient granulometry for the use of soil cement, and also that it has a resistance of 129.42 kg-f/cm² with 21% cement at 28 days of curing. The lab test results also showed that the cement soil loses just 4.22% in weight with 17% of cement in the durability test, as well as with this same percentage, the soil cement presents a higher maximum compaction density of 2,255 g/cm³. These results propose alternative applications for soil cement according to their resistance, granulometry and durability. According to the Peruvian Technical Standard, the minimum f'c for floor concrete base is 100 kg/cm², a dosage of 19% cement was proposed for this element, and for brick masonry the minimum f'c is 50kg/cm², so it was proposed 12% cement to meet this requirement, in addition, the soil cement was proposed as a slope protection with 17% cement since it achieved good results in the durability test.

Environmental life-cycle assessment of concrete produced in the United States

Concrete is a primary material in infrastructure projects and is a significant contributor to global climate emissions. However, there is a lack of readily available cement and ready-mix concrete inventory data for evaluating the environmental performance of the industries. This study describes the development of cradle-to-gate inventories for U.S. ready-mix concrete and gate-to-gate inventories for portland cement production technologies. These life-cycle inventories provide baselines for the environmental releases associated with concrete that is used for major infrastructure projects. The inventories are incorporated into the publicly available Greenhouse gases, Regulated Emissions, and Energy use in Technologies (GREET) model. The life-cycle inventories are created using facility-level environmental release data from U.S. datasets normalized to activity levels which are based on production capacity and utilization data provided by Portland Cement Association (PCA) and the U.S. Geological Survey Minerals Yearbook. Unit processes for limestone quarrying, sand and gravel quarrying, and wet-mix concrete batch plants are developed on the basis of national total point-source environmental releases and production statistics, coupled with corresponding flows associated with off-road fuel consumption and other non-point-source emissions. Midpoint impact assessment results are normalized to provide insight into their relative significance in the context of U.S. total impacts. These findings show that advanced calcination technologies help reduce greenhouse gas emissions, but the full set of releases also highlights the significance of metal releases and particulate-matter emissions generated by non-combustion-related activity.

Cement, Concrete and Research Literature Online Repositories (Portland Cement Association)

Cement, Concrete and Research Literature Online Repositories (Portland Cement Association)

Stormwater Harvested from Permeable Pavements as a Means to Save Potable Water in Buildings

The main objective of this work is to analyse the potential for potable water savings in university buildings by using stormwater collected from permeable pavements. Six buildings located on the campus of the Federal University of Santa Catarina (UFSC) were selected to obtain monthly water consumption patterns and parking lot areas. The same six buildings were then evaluated considering their location in eight different cities in Brazil, with different rainfall patterns. Simulations using the computer programme Netuno were run to obtain the potential for potable water savings in each building and city combined. The structural design of permeable pavements was also assessed using two methods available in the literature, that is, the American Association of State Highway and Transportation Officials (AASHTO) and Brazilian Portland Cement Association (ABCP). The hydrological-hydraulic design of the permeable pavement was also carried out. The designed thicknesses were compared with the thicknesses obtained using the computer programme Permeable Design Pro. The potential for potable water savings between 18.4% and 84.8% was obtained, depending on the city, building and non-potable water demand considered. For the structural design, the thicknesses obtained by using both methods were similar; however, it was observed that the AASHTO method better represents the pavement model. Regarding the hydrological-hydraulic design, the differences obtained show that the simplification performed for the pavement drainage was in favour of safety. In conclusion, the use of permeable pavements in stormwater harvesting systems is promising, aligning the drainage aid, structural capacity and potential for saving potable water.

The effect of CO2 loading on the properties of normal concrete vs fly ash concrete

Purpose There is an increase in greenhouse gasses and global climate change is frequently reported on. What can be done? Certainly to try and reduce the carbon footprint, which is not a new topic, by encouraging applications and activities for concrete during its lifetime (Portland Cement Association, 2019). This study aims to focus on introducing CO2 to normal and fly ash concrete and thus investigating the effect on the carbon footprint of the samples and the effectiveness of the CO2 introduction methods, namely, carbonated water addition during the mixing process and by means of an infusion pipe directly into the concrete when the samples are casted and have been casted. Design/methodology/approach The feasibility of carbon dioxide storage within concrete is determined by investigating the effects of introduced carbon dioxide into concrete samples and the effectiveness of the concrete at storing carbon dioxide. The concrete was mixed in a 1:3:3 ratio for the OPC or blended 52.5 R cement:sand:stone (22 mm) with a 28 day strength of 50 MPa. Samples were also prepared containing low-grade fly ash cement contents ranging from 15% to 60%. CO2 was introduced to the concrete via carbonated mixing water and an infusion pipe system directly to the hardening concrete cubes. In total, 16 g CO2 bicycle carbon dioxide inflators and valve system were used to infuse the concrete over a period of a week until the canister was emptied with valve release on the lowest setting. A compression test was carried out to determine the strength of the concrete cubes with, and without, the introduction of carbon dioxide. Results were also obtained using a scanning electron microscope (SEM) and energy dispersive x-ray spectrometer (EDS) to determine how the carbon dioxide changed the microscopic composition and chemical composition of the concrete. A microcontroller with carbon dioxide sensors was used to gather carbon dioxide emission data for a period of three months. Findings The compressive strength tests show by introducing carbon dioxide to the concrete, the compressive strength has increased by as much as 13.86% as expected from the literature. Furthermore, by infusing carbon dioxide with the fly ash blended cement, will give a higher strength compared to the control with ordinary portland cement. This correlates to an overall reduction in cost for the structure. The optimal fly ash content for the control with minimal strength degradation is 30%. Where the optimal fly ash content for the concrete with carbon dioxide stored within, is 45%. The SEM analysis showed the concrete with sequestered carbon dioxide has significantly more calcium silicate hydrate (C-S-H) gel formation, thus the strength increase. Furthermore, the carbon dioxide emission test showed the concrete with infused carbon dioxide stores carbon dioxide more efficiently compared to the control sample. With the data showing the infused sample releases 11.19% less carbon dioxide compared to the control sample. However, the carbonated water sample releases 20.9% more carbon dioxide when compared to the control sample. Thus the introduction of carbon dioxide by means of infusion is more effective. Practical implications This is a practical pilot investigation of carbon dioxide introduction via two methods, one being infusion of CO2 into normal concrete and fly ash concrete and two, mixing normal and fly ash concrete with carbonated water. These results show, cheaper cement can be used to achieve equivalent or better strength. This can help in the reduction of the construction industry’s carbon footprint. Originality/value By reducing the construction industry’s carbon footprint with this research results, a saving can not only be made financially in the construction industry, but this will help to preserve our environment for future generations.

Portland clinker with civil construction waste: influence of pellet geometry on the formation of crystalline phases

Abstract Efforts to reduce greenhouse gas emissions in the context of sustainable development have intensified, with the development of research aimed at the production of new materials and binders for construction. This article analyzes the influence of pellet geometry in the production of clinkers, with the incorporation of construction waste (CCW). Procedures adapted from the method proposed by Brazilian Portland Cement Association were adopted in studies of laboratory clinkers, in an attempt to simulate the stages of the industrial process. Pellets were prepared with the same formulation, however, with four different geometries: spherical, with diameters of 1 cm, 2 cm and 3 cm, with manual molding, and semi-spherical, with a diameter of 2 cm, using molds of PLA (polylactic acid) printed on a 3D printer to facilitate the molding of the clinkers in a standardized way. Clinkers were characterized mineralogically by x-ray diffraction (XRD) and the Rietveld method was used to quantify the phases. Variations in the quantities of the alite and belite phases were observed depending on the geometry of the pellets, although the same calcination conditions were used. This is probably due to the variation in the surface area (exposure area) and the gradients of the cooling rate.

Mechanical and durability properties of fiber reinforced concrete overlay: Experimental results and numerical simulation

Nowadays, fiber reinforced concrete (FRC) overlays are used for repairing and reinforcing pavements. In this research, some experimental tests performed to investigate the effects of steel and synthetic fibers on the performance of the concrete overlay. The synthetic fiber in this study is based on Modified Synthetic Polypropylene (MSP) Fiber. Plain and FRC specimens underwent flexural and compressive strength, and durability tests. The results show that the use of MSP in concrete overlays increases compressive and flexural strength, residual strength, ductility, and energy absorption, and reduces the resistance of concrete against freezing and thawing cycles. Using similar addition volume, Steel Fiber Reinforced Concrete (SFRC) has better flexural performance and lower compressive strength and workability than Modified Synthetic Polypropylene Fiber Reinforced Concrete (MSPFRC). To determine the thickness of the bonded concrete overlay (t), the Portland Cement Association (PCA) design criteria were used. In this study, these criteria simulated using finite element (FE). The results showed that the use of MSP in concrete overlays could reduce the thickness of bonded concrete overlay up to 15%.

Long-Term Durability of Ordinary Portland Cement and Polypropylene Fibre Stabilized Kaolin Soil Using Wetting–Drying and Freezing–Thawing Test

Soft soil stabilization frequently uses cement, lime, fly ash, etc., but very limited studies were conducted on the long-term durability of stabilized soil. The present study deals with the long-term durability of commercially available kaolin soil stabilized with ordinary Portland cement (OPC) and polypropylene fibre using a much more realistic approach, where the effect of weathering action can be observed in each cycle. Laboratory investigations were conducted to find the percentage loss of stabilized soil during wetting–drying and freezing–thawing tests, which are used as a durability indicator of cement and cement–fibre-stabilized soil. The stabilized soil encounters seasonal cycles of monsoon and summer in long run of its service life, which is simulated in rapid harsh weathering cycles in a laboratory setup. Kaolin soil samples were stabilized using different percentages of cement and mix of cement–fibre combination and were subjected to 12 cycles of wetting–drying and freezing–thawing cycles separately to determine the percentage loss of soil in accordance with the ASTM standards. Results of wetting–drying tests indicate that kaolin soil stabilized with cement and fibre combination survived up to 12 cycles, but only 10% cement + 0.5% fibre was durable against wetting–drying test based on percentage loss. Results of freezing–thawing tests indicate that only the kaolin soil stabilized with 10% cement, 5% cement + 0.5% fibre, and 10% cement + 0.5% fibre survived up to 12 cycles and are durable against freezing–thawing test based on percentage loss which satisfies the Portland Cement Association’s durability specification.

A critical review of the PCA and IRC methods of thin white topping pavement design

The concept of Thin White Toppings (TWT) is gaining momentum across the nations as an economical and durable rehabilitation technique for the bituminous roads in distress compared to repairs or rehabilitations done with bituminous mixes. On the other hand, constructing a completely new cement concrete (CC) pavement in these stretches by removing the existing pavement structure is a very costly alternative. So, Portland Cement Association (PCA) constructed some test sections of TWT and developed the performance equations based on the performance of the test sections. Indian Roads Congress (IRC) adopted these equations and simplified them with minor changes for calculating the stresses. These changes lead to overestimation of stresses and subsequent reduction in cost saving for TWT compared to constructing a new concrete pavement. The present study examines the differences between IRC and PCA design methods for TWT by considering various parameters. Both methods consider 8 T single axle load and 16 T tandem axle load for estimating the stresses in CC layer. The stresses estimated with IRC equations are higher compared to the stresses estimated with PCA equations of the order of 40 to 50 percent for 8 T single axle load and of the order of 0 to 22 percent for 16 T tandem axle load.

Effect of temperature gradients on the behaviour of jointed plain concrete pavements

Abstract In many countries of Latin America, Jointed Plain Concrete Pavements (JPCP) are designed using the American Association of State Highway and Transportation Officials (AASHTO) or the Portland Cement Association (PCA) methods, none of which take explicitly into account the environmental conditions of the specific region where a JPCP will be built. It is well known that temperature gradients across the thickness of concrete slabs produce curling which can cause slabs to lose support at its corners and its center depending on the time of the day. This situation, in combination with vehicle loading, generates tensile stresses which can be significant enough to cause initial cracking and the subsequent failure of the pavement. In this research, the Finite Element (FE) package EverFE2.25 was used to study the impact of temperature gradients (calibrated to account for humidity gradients) in combination with a vehicle load (a dual wheel tandem axle of 180 kN) on the performance of a typical JPCP highway section. For the JPCP under study, the apparent increase of the tensile stresses attributable to negative local (ΔT = -18.5°C) Equivalent Temperature Gradients (ETGs) was as 5.5 times larger than the one induced by the axle when it was placed at the border of the slab and up to 8.8 times larger when it was placed at the corner of the slab. Although the apparent increase was not as high when the positive local ETGs (ΔT = +18.5°C) were used, the absolute magnitude of the stresses in combination with the vehicle load were still high enough for the pavement to fail under fatigue. Thus, local temperature gradients should be studied regionally and considered in the design of JPCP using more suitable design procedures such as the Mechanistic-Empirical design procedure.

Assessment Of Designed And Measured Mechanistic Parameters Of Concrete Pavement Foundation

There are plenty of in situ tests available to examine pavement foundation performance regarding stiffness and support conditions. This study evaluates several in situ tests of the stiffness and support conditions of concrete pavement foundation layers. The principal objective of this study was to evaluate the outputs from Dynamic Cone Penetrometer tests and Falling Weight Deflectometer tests. The California Bearing Ratio from Dynamic Cone Penetrometer tests and the deflection data from Falling Weight Deflectometer tests were correlated to the design parameter – modulus of subgrade reaction k through correlations employed in pavement design manuals. Three methods for obtaining the k values were conducted, with the intent to evaluate which method provides the results most similar to the target value and whether the studied correlations are reliable. The back-calculated k values from Falling Weight Deflectometer deflections and the weak layer California Bearing Ratio correlated k values based on the Portland Cement Association method were close to the target value, while the California Bearing Ratio empirically correlated k based on the American Association of State Highway and Transportation Officials method presented values significantly higher than the target value. Those previously reported correlations were likely to overestimate the k values based on subgrade California Bearing Ratio values.

FLEXURAL STRESS ANALYSIS OF RIGID PAVEMENTS USING AXI-SYMMETRIC AND PLANE STRAIN FEM

The design of pavement involves a study of soils and paving materials, their response under load for different climatic conditions. In the present study, an attempt has been made to compare stresses predicted using two finite element analyses. First analysis is based on the twodimensional plane strain assumption where as in second approach axi-symmetric condition is assumed to consider three-dimensional behavior of rigid pavement. The results are compared with flexural stresses obtained from conventional Portland Cement Association method. The computed flexural stresses obtained from axi-symmetric condition are found to be in close agreement with PCA method. Results of plane strain analysis show a fair agreement after application of an appropriate multiplication factor

Additional Intermediate Tension Coefficients in Cylindrical Liquid Storage Tanks under Hinged Base Condition

Hoop tension coefficients for analysis of cylindrical liquid storage tanks are available in codes of practice of various countries and also in Portland Cement Association (PCA). Hoop tension coefficients values are dependent on the dimension parameters, ranging from 0.4 to 16. Since these coefficients are available in irregular intervals with the assumption that the intermediate coefficients can be calculated by interpolation. This paper shows graphically and with the table providing in the appendix by solving the fourth order differential equation that the hoop tension coefficient values, calculated from interpolation is not accurate with the increasing from 0.4 to 16. Availability of these intermediate hoop tension coefficients for from 0.4 to 16 with interval of 0.1 will not only facilitate analysis and design process for variety of tank dimensions with better accuracy but also provides ease to the practicing engineers.

Lift Truck Load Stress in Concrete Floors

This text presents an analytical expression to calculate the maximum tension, at the bottom side of a concrete slab on ground, due to lift truck wheel loads. The result of the analytical expression is in close agreement with the result of a design chart by the Portland Cement Association and with the result of a finite element analysis. The analytical expression is able to show the relationships among the design variables and it can be used for the thickness design of concrete floors for factories and warehouses. The expression applies only to unreinforced concrete slabs on ground.

Influencing compressive strength of roller-compacted concrete

Roller-compacted concrete is a type of zero-slump concrete that usually has a higher compressive strength than ordinary concrete, with the same cement content. This is primarily due to the high level of aggregate interlock achieved by compaction, but many other factors are also involved. The goal of this study was to investigate the influence of aggregate gradation, cement content, water content, compaction effort, curing conditions and admixtures on the compressive strength of roller-compacted concrete. It was found that aggregate gradation within the limit recommended by the Portland Cement Association is desirable for high compressive strength. The concrete becomes less sensitive to water content when the cement content is augmented, and a minimum of 98% modified Proctor dry density ratio is needed to achieve the maximum strength. Moderate strength improvement can be obtained with moisture control during the curing process, and it is possible to extend working time by using admixtures without compromising strength.