Short-term Compressive Strength Research Articles

Characterization of the remaining material and mechanical properties of historic wooden foundation piles in Amsterdam

The majority of the bridges in the historic city centre of Amsterdam are supported by wooden foundation piles. Most of these were constructed 100–300 years ago, currently raising concerns about potential safety issues. The wooden piles under the bridges remain entirely under the water table, potentially subjected to bacterial decay in anaerobic conditions. Bacterial degradation proceeds at a slow rate, allowing the piles to perform their function for many years, although causing a reduction of their load-carrying capacity over time. To this end, a large experimental campaign was conducted to characterize the material and mechanical properties in relation to biological decay of 60 spruce and fir piles, dated back to 1727, 1886 and 1922, retrieved from two bridges in Amsterdam. Large-scale compression tests were carried out on 201 pile-segments extracted from head, middle-part and tip of the piles to determine their remaining short-term compressive strength. Micro-drilling measurements were conducted on each pile and analysed with a TU-Delft-developed algorithm, aimed at determining the soft shell – the width of the decayed outer layer of the piles’ cross section. Micro-drilling allowed to accurately assess the remaining sound cross section of the pile, which resulted to be well correlated to its mechanical properties. The extent of decay throughout the cross-section of the piles was assessed within sapwood and heartwood through experimental models from literature and validated with Computed Tomography (CT) scanning. This allowed to identify that bacterial decay was only present in the non-durable sapwood, even in very degraded piles. Moreover, the soft shell resulted to be rather uniform along the piles’ length. The analysis of decay, supported by micro-drilling and CT scans, allowed to develop experimental equations to predict the remaining short-term compressive strength along the pile length. The micro-drilling technique is now used on a large scale in Amsterdam, supporting the assessment of the remaining load carrying-capacity of wooden foundation piles in the city, aiding in the planning of conservation, maintenance and preservation strategies.

Innovative application of micro-drilling for the assessment of decay and remaining mechanical properties of historic wooden foundation piles in Amsterdam

The majority of bridges and quay walls in the centre of Amsterdam are supported by 100–300 years-old wooden foundation piles subjected to bacterial decay. Bacterial degradation proceeds at a slow rate, allowing the piles to perform their function for many years, although causing a reduction of their load-carrying capacity over time. In this study, micro-drilling measurements were employed to capture the amount of decay and remaining short-term compressive strength of the historic wooden piles. The applicability of micro-drilling was studied on 60 wooden piles with various decay levels, retrieved after 100–295 years of service life. An algorithm was developed for analysing the micro-drilling signals, aimed at determining the decayed outer layer of the piles’ cross section, and validated with the results of mechanical testing on the piles. The micro-drilling technique is now used on a large scale in Amsterdam, supporting the assessment of the wooden foundation piles in the city.

Utilization of GEP and ANN for predicting the net-zero compressive strength of fly ash concrete toward carbon neutrality infrastructure regime

Abstract The present infrastructure regime being promoted by the United Nations Sustainable Development Goals is such that by the year 2050, the use of cement in the production of concrete and its use in the general construction activities as to reduce carbon emissions to zero must be replaced with net-zero construction materials. These cement replacement materials should be pozzolanic enough to either partially or totally replace the conventional cement and reduce its carbon footprint. The current study adopts two machine learning techniques: gene expression programming (GEP) and artificial neural network (ANN) to determine the 56 days and 180 days of net-zero compressive strength of fly ash concrete. The study effectively depicts how machine learning techniques can be used for the prediction of long- and short-term compressive strength of fly ash concrete toward a carbon neutrality infrastructure regime. The dataset has been compiled by various researchers, and the input parameters include cement, fine aggregate, coarse aggregate, fly ash, water, and water/binder ratio. And the 56 days and 180 days compressive strength (fck) values are the targeted output values. In order to determine a better model, both GEP and ANN were assessed based on the values of the correlation coefficient and crosschecked by other statistical parameters. Both models performed well; however, GEP outweighs the ANN model in estimating the fck at 56 days and 180 days. Moreover, the GEP model generated a simplified equation for foreseeing the value of fck for different ages of net-zero fly ash concrete.

Temperature-Dependent Classification of Geopolymers Derived From Granite Designed for Well Cementing Applications

Abstract Alternative materials such as geopolymers appear to have potential advantages compared to Portland cement. However, the application of geopolymers for all sections of the well is still a major challenge due to the difference in temperature ranges. To that end, the classification of the granite-based geopolymer mix designs requires a thorough investigation of various properties at a range of different operational temperatures. In this study, three mix designs are presented for different well sections at temperatures ranging from 5 °C to 60 °C. The mix designs for low temperatures (<50 °C) were tuned by adding CaO to the dry solid blend. Workability, rheology, short-term compressive strength, and X-ray diffraction (XRD) analysis were conducted to conclude the performance of the mix designs under study. Results highlight the presence of Ca content (wt%) in mix designs and its role in enhancing material performance at low operational temperatures. The study reveals a promising future application of the granite-based geopolymer for well construction and abandonment at varying depths with recommendations for further improving the performance by the addition of chemical admixtures. In addition, the relation between temperature and Ca content was highlighted, and more investigations into the kinetics governing these two parameters were recommended.

Microstructure and chemical characterizations with soft computing models to evaluate the influence of calcium oxide and silicon dioxide in the fly ash and cement kiln dust on the compressive strength of cement mortar

Environmental issues are raised from the global warming due to raised Carbon Dioxide (CO2) emissions of factories worldwide. Cement manufacturing is highly energy- and emissions-intensive because of the extreme heat required to produce it. Producing a ton of cement requires 4.7 million British Thermal Units (BTU) of energy, equivalent to about 400 pounds of coal, and generates nearly a ton of CO2. Therefore, it is necessary to reduce cement production; as a result, it contributes to solving those issues. This study investigates the effect of two major chemical compositions in the CKD and FA on the long-term compressive strength of cement mortar, especially their Calcium Oxide (CaO) and Silicon Dioxide (SiO2) contents; furthermore, their chemical, mineralogical, and microstructure are compared. In addition, 228 data for FA-modified cement mortar and 167 data for CKD-modified cement mortar were collected from previous literature and used to develop predictive models to forecast the compressive strength of cement mortar modified with CKD and FA. The dataset contained different mix proportions of the cement mortar, such as curing times, various SiO2 (%), CaO (%), water/cement ratio (w/c), and curing times up to 90 days. The result of the Multi expression programming (MEP), full quadratic (FQ), Nonlinear regression (NLR), and artificial neural network (ANN) models were used to quantify the effect of CaO and SiO2. The short-term compressive strength of cement mortar modified with fly ash (from 1 to 28 days) decreases with increasing the fly ash content, while the long-term compressive strength (from 28 to 90 days) increases by up to 15% replacement of cement with fly ash. However, the compressive strength of the cement kiln dust modified-cement mortar decreases with increasing the cement kiln dust content. The sensitivity evaluation discovered that the most influential parameter for predicting compressive of the cement mortar modified with CKD and modified with FA is the curing time.

Design of Fly Ash-Based Alkali-Activated Mortars, Containing Waste Glass and Recycled CDW Aggregates, for Compressive Strength Optimization.

Alkali-activated mortars and concretes have been gaining increased attention due to their potential for providing a more sustainable alternative to traditional ordinary Portland cement mixtures. In addition, the inclusion of high volumes of recycled materials in these traditional mortars and concretes has been shown to be particularly challenging. The compositions of the mixtures present in this paper were designed to make use of a hybrid alkali-activation model, as they were mostly composed of class F fly ash and calcium-rich precursors, namely, ordinary Portland cement and calcium hydroxide. Moreover, the viability of the addition of fine milled glass wastes and fine limestone powder, as a source of soluble silicates and as a filler, respectively, was also investigated. The optimization criterium for the design of fly ash-based alkali-activated mortar compositions was the maximization of both the compressive strength and environmental performance of the mortars. With this objective, two stages of optimization were conceived: one in which the inclusion of secondary precursors in ambient-cured mortar samples was implemented and, simultaneously, in which the compositions were tested for the determination of short-term compressive strength and another phase containing a deeper study on the effects of the addition of glass wastes on the compressive strength of mortar samples cured for 24 h at 80 °C and tested up to 28 days of curing. Furthermore, in both stages, the effects (on the compressive strength) of the inclusion of construction and demolition recycled aggregates were also investigated. The results show that a heat-cured fly ash-based mortar containing a 1% glass powder content (in relation to the binder weight) and a 10% replacement of natural aggregate for CDRA may display as much as a 28-day compressive strength of 31.4 MPa.

Assessment of the Compressive Strength of Lime Mortars with Admixtures, Subjected to Two Curing Environments

This article presents the assessment of the compressive strength of three types of lime mortar, one without admixture and the remaining two added with metakaolin and brick dust. The chemical composition of the lime and the pozzolans was evaluated using the X-ray fluorescence (XRF) technique. The mortars were subjected to two curing conditions: humidity and temperature-controlled chamber, and accelerated carbonation chamber, then they were tested at ages of 7, 28, 60 and 90 days. The results showed that the samples cured in the carbonation chamber presented higher compressive strength values than the ones cured in the humidity and temperature-controlled chamber, due to the fact that lime mortars increase their strength with the carbonation of the calcium hydroxide that exists in the lime. Likewise, when adding metakaolin to the lime mortars cured in the humidity and temperature-controlled chamber, the values of compressive strength were close to those of the mortars with lime only, that were cured in the carbonation chamber. From the results of the research, it is notable that the use of pozzolans in lime mortars improves the short-term compressive strength, which is attractive for the rehabilitation of heritage buildings since in short periods of time it manages to match the strengths that lime mortars acquire over time.

Optimum curing temperature and duration of alkali-activated glass inorganic binders

ABSTRACT The effects of curing temperature and duration on the compressive strength of alkali-activated glass inorganic binder (AAGIB) are investigated here. AAGIB specimens, produced by mixing glass powders with an activator containing only sodium hydroxide, were cured at temperatures ranging from 60 to 100°C for various durations and then placed in air for different numbers of days. The short and long-term compressive strengths of AAGIBs under the curing process were measured and compared to one another. Results show that the optimal curing duration to give a maximum short-term compressive strength becomes shorter as the curing temperature is raised. However, the long-term compressive strengths of AAGIBs can be enhanced substantially if they are cured at a relatively low temperature for optimal curing duration. The resulting maximum compressive strengths of AAGIBs depend on the alkali-equivalent content in the activator. Consequently, the optimal alkali-equivalent content, curing temperature and curing duration for the production of AAGIBs are suggested.

Long-term quality control of self-compacting semi-lightweight concrete using short-term compressive strength and combinatorial artificial neural networks

Artificial neural networks are used as a useful tool in distinct fields of civil engineering these days. In order to control long-term quality of Self-Compacting Semi-Lightweight Concrete (SCSLC), the 90 days compressive strength is considered as a key issue in this paper. In fact, combined artificial neural networks are used to predict the compressive strength of SCSLC at 28 and 90 days. These networks are able to re-establish non-linear and complex relationships straightforwardly. In this study, two types of neural networks, including Radial Basis and Multilayer Perceptron, were used. Four groups of concrete mix designs also were made with two water to cement ratios (W/C) of 0.35 and 0.4, as well as 10% of cement weight was replaced with silica fume in half of the mixes, and different amounts of superplasticizer were used. With the help of rheology test and compressive strength results at 7 and 14 days as inputs, the neural networks were used to estimate the 28 and 90 days compressive strengths of above-mentioned mixes. It was necessary to add the 14 days compressive strength in the input layer to gain acceptable results for 90 days compressive strength. Then proper neural networks were prepared for each mix, following which four existing networks were combined, and the combinatorial neural network model properly predicted the compressive strength of different mix designs.

Effect of carbon fiber on mechanical properties and dimensional stability of concrete incorporated with granulated-blast furnace slag

Concretes with binary and ternary blends of Portland cement, granulated-blast furnace slag (GGBS), and carbon fiber (CF) were prepared to investigate their effects on mechanical performance, drying shrinkage and creep behaviors. Nine types of concrete mixtures were prepared and tests were conducted during a long testing period which was up to 180 days. Research showed that GGBS and CF played a detriment effect on short-term compressive strength. GGBS could improve the workability of concretes, while CF presented an opposite effect. Concrete with the addition of CF showed superior drying shrinkage resistance and creep resistance, while GGBS increased the drying shrinkage and creep potentials. The coupling effect of GGBS and CF on the drying shrinkage and creep performance highly depended on the relative content of GGBS and CF. Analysis of variance (ANOVA) was performed to analyze the importance of GGBS and CF on the drying shrinkage and creep performance. Results showed that test period, content of GGBS, and content of CF were all significant factors in influencing the drying shrinkage and creep behaviors. Models to predict the drying shrinkage strain and creep coefficient were proposed by considering different proportions of cement, GGBS, and CF, and the models give promising results. Besides, the cost-benefit analysis and the environmental impact were also quantitively studied, and results showed that concretes incorporated with 20% GGBS in mass and 0.1% or 0.2% CF in volume presented both good cost-benefit effectiveness and low environmental impact. • Concrete incorporated with GGBS and carbon fiber CF was prepared. • The mechanical, drying shrinkage and creep behaviors were investigated. • Analysis of variance (ANOVA) was conducted. • Models were established to predict the shrinkage strain and creep coefficient. • Cost-benefit and environmental impact analysis were performed.

Mine Backfilling in the Permafrost, Part II: Effect of Declining Curing Temperature on the Short-Term Unconfined Compressive Strength of Cemented Paste Backfills

When cemented paste backfill (CPB) is used to fill underground stopes opened in permafrost, depending on the distance from the permafrost wall, the curing temperature within the CPB matrix decreases progressively over time until equilibrium with the permafrost is reached (after several years). In this study, the influence of declining curing temperature (above freezing temperature) on the evolution of the unconfined compressive strength (UCS) of CPB over 28 days’ curing is investigated. CPB mixtures were prepared with a high early (HE) cement and a blend of 80% slag and 20% General Use cement (S-GU) at 5% and 3% contents and cured at room temperature in a humidity chamber and under decreasing temperatures in a temperature-controlled chamber. Results indicate that UCS is higher for CPB cured at room temperature than under declining temperatures. UCS increases progressively from the stope wall toward the inside of the CPB mass. Under declines in curing temperature, HE cement provides better short-term compressive strength than does S-GU binder. In addition, the gradual decline in temperature does not appear to affect the fact that the higher the binder proportion, the greater the strength development. Therefore, UCS is higher for samples prepared with 5% than 3% HE cement. Findings are discussed in terms of practical applications.

Effect of Clay Content on Soil Stabilization with Alkaline Activation

This paper presents the role of clay portion in soil used to stabilize soils during alkaline activation with potassium-based alkaline activator. A 10 M potassium hydroxide solution was utilized to activate the soils with and without palm oil fuel ash (POFA) at a solution. Soils with and without POFA mixtures were tested using unconfined compression tests and microstructural analysis (using scanning electron microscopy and X-ray diffraction). Comparing the strength of the mixtures with and without POFA, the results presented that short-term compressive strength was higher for mixtures with POFA. However, after longer curing the admixtures of higher kaolinite content with POFA reached significantly higher strength levels than the admixtures without POFA. This work brings new insights to the soil stabilization by alkaline activation providing a relatively new avenue for effective utilization of aluminosilicate source materials with parent-treated soils. The clay minerals of hosted soil play an important role in soil stabilization with alkaline activation that affects the behavior of binder with hosted soil.

Potential use of activated Algerian natural pozzolan powder as a cement replacement material

The purpose of this experimental work is to develop a suitable approach for an alkali-activated binder material to replace cement CEM-II/42.5 by 80% of natural pozzolan. The chemical activity of silica and alumina found in Algeria's natural pozzolan is improved using heat treatment and chemical curing, together with several alkali activators, including a 6-mole NaOH and a 6-mole KOH along with CaCl2, Na2SO4 and Na2SiO3. The chemical and morphological processes are monitored using X-ray diffraction, TGA and DTA, as well as particle size distribution analyses. Laboratory tests show that thermal pretreatment positively affects the compressive strength; moreover, the use of 6% Na2SiO3 and 6% Na2SO4 results in increased short-term and long-term compressive strength, respectively. Optimal compressive strength values are reached under chemical activation and thermal pretreatment processes. These combined processes also affect Young's modulus values and the relative deformations caused by ultimate stresses. This experimental work highlights the potential of natural pozzolan in producing an economical and environmentally-friendly sustainable material that can be substituted for Portland cements and used in multiple engineering applications.

Short-Term Compressive Strength of Fly Ash and Waste Glass Alkali-Activated Cement-Based Binder Mortars with Two Biopolymers

AbstractThe Roadmap to a Resource Efficient Europe aims that by 2020, waste will be managed as a resource. Thus materials that have the ability for the reuse of several types of wastes, such as alk...

Assessment of the mechanical performance of crumb rubber concrete

Crumb rubber concrete (CRC) has some known shortcomings in mechanical performance compared to conventional concrete, particularly with respect to compressive strength. Many previous researchers have tried to overcome the material deficiencies using different methods; however, the results have often been contradictory and highly variable. In this research, three methods to improve and then assess the mechanical performance of CRC have been examined namely, rubber pre-treatment using sodium hydroxide (NaOH) solution, using silica fume additives, and increasing concrete cement content. The effect of the rubber pre-treatment time (0–2h), silica fume content (0–15%), and cement content (300–400kg/m3) on CRC slump, short and long term compressive strength, and tensile strength were measured for fifteen concrete mixes prepared with 0% and 20% rubber content. Six 100×200mm cylinders were prepared from each mix for evaluating the compressive strength at 7 and 28days. Four additional 100×200mm cylinders were prepared from two mixes for evaluating the compressive strength at 56 and 84days. In addition, two 150×300mm cylinders for each mix were prepared and tested to determine the indirect tensile strength at 28days. The results showed that 0.5h of rubber pre-treatment using NaOH solution, 0% of silica fume replacing cement by weight, and 350kg/m3 cement content were the best alternatives in this assessment range to enhance the CRC performance.

Utilization of Fly Ash in High Performance Floor Screed Based on Cement and its Influence on Physical Mechanical Properties

This paper deals with the evaluation of a partial replacement of cement by Czech fly ash in high strength floor screed in dosage of 10, 20, 30 and 40% and the assessment of the physical-mechanical properties such as compressive strength, water absorption and bulk density. Used fly ashes are from power plants Počerady, Opatovice and Tušimice. The experimental study showed that the use of Czech fly ash improves the compressive strength. The bulk density decreases and therefore water absorption increases. Reference samples become clearly the lowest compressive strength at age of 28 days (fc28). A significant increase in compressive strength (fc28) was observed in case of mix design with addition of 10% and 20% of fly ash Tušimice (10%ETU, 20%ETU) and 20% and 30% of fly ash Počerady (20%EPC, 30%EPC). The addition of 20% of fly ash Počerady (20%EPC) has noticeable influence on short-term compressive strength (measured at the age of 24 hours).

Prediction of compressive strength of concrete based on accelerated strength

Moist curing of concrete is a time consuming procedure. It takes minimum 28 days of curing to obtain the characteristic strength of concrete. However, under certain situations such as shortage of time, weather conditions, on the spot changes in project and speedy construction, waiting for entire curing period becomes unaffordable. This situation demands early strength of concrete which can be met using accelerated curing methods. It becomes necessary to obtain early strength of concrete rather than waiting for entire period of curing which proves to be uneconomical. In India, accelerated curing methods are used to arrive upon the actual strength by resorting to the equations suggested by Bureau of Indian Standards' (BIS). However, it has been observed that the results obtained using above equations are exaggerated. In the present experimental investigations, the results of the accelerated compressive strength of the concrete are used to develop the regression models for predicting the short term and long term compressive strength of concrete. The proposed regression models show better agreement with the actual compressive strength than the existing model suggested by BIS specification.

Resistance of fly ash–Portland cement blends to thermal shock

Thermal-shock resistance of high-content fly ash–Portland cement blends was tested in the following ways. Activated and non-activated blends with 80–90% fly ash F (FAF) were left to set at room temperature, then hydrated for 24 h at 85°C and then for an additional 24 h at 300°C, and tested in five thermal-shock cycles (600°C heat – 25°C water quenching). X-ray diffraction (XRD) and thermal gravimetric analyses, along with calorimetric measurements and scanning electron microscope-energy-dispersive X-ray tests demonstrated that the activated blends form more hydrates after 24 h at 300°C, and achieve a higher short-term compressive strength than do non-activated ones. Sodium meta-silicate and soda-ash engendered the concomitant hydration of ordinary Portland cement (OPC) and class F fly ash (FAF), with the formation of mixed crystalline FAF–OPC hydrates and FAF hydrates, such as garranite, analcime and wairakite, along with the amorphous FAF hydration products. In sodium sulfate-activated and non-activated blends separate OPC (tobermorite) and FAF (amorphous gel) hydrates with no mixed crystalline products formed. The compressive strength of all tested blends decreased by nearly 50% after five thermal-shock test cycles. These changes in the compressive strength were accompanied by a marked decrease in the intensities of XRD patterns of the crystalline hydrates after the thermal shock. There was no significant difference in the performance of the blends with different activators.

Studying the hardening and mechanical performances of rice husk and hemp-based building materials cured under natural and accelerated carbonation

The purpose of this paper is to investigate the mechanical properties and the lime-based binder hardening of green concretes made of rice husk or hemp hurd. Concrete specimens were subjected to different curing conditions. Under natural carbonation, specimens were cured during 10months either in a climate-controlled room (20°C – 50%RH) or exposed outdoors. The work also focused on an accelerated carbonation curing (CO2 curing) aiming to improve the short term compressive strength (1–2months) of the concrete materials.Compressive strength tests were conducted at different dates until 10months of natural carbonation and after CO2 curing. Powdered matrix samples were collected in the bulk and on the surface of the specimens to investigate carbonation and hydration of the binder by thermal analysis and a phenolphthalein test was used to provide information about the carbonation depth.Under natural carbonation, the results indicated that the lime-based binder was almost hardened in the same way for both concretes with a similar rate of carbonation. However, the rice husk concrete was characterized by a ceiling effect of mechanical performances over time, which was attributed to the lower bonding strength between rice husks and lime. Concerning specimens exposed outdoors, the strength gain over time was more significant owing to more favorable humidity conditions for carbonation. The accelerated carbonation curing led to an increase of mechanical properties of the concretes in the short term. The compressive strength after CO2 curing was approximately equivalent to those obtained after 10months of outdoor exposure under natural carbonation.

Testing and Modeling the Short-Term Behavior of Lime and Fly Ash Treated Sulfate Contaminated CL Soil

In this study, the effects of calcium sulfate contaminated soil treatment methods on the index properties, compacted soil properties, free swelling and compressive stress strain relationship of a CL soil obtained from the field was investigated. Calcium sulfate concentration in the soil was varied up to 4 % (40,000 ppm) and the soil samples were cured for seven days at 25 °C and 100 % humidity before testing. With 4 % sulfate contamination the liquid limit and plasticity index of the soil increased by 44 and 81 % respectively. The free swelling increased from 7 to 18 % and the compressive strength decreased by 65 % with 4 % of calcium sulfate, Also the study investigated the effects of fly ash (class C) and hydrated lime treatment on the behavior of treated sulfate soils. X-ray diffraction (XRD) was used to characterize the soil and the reaction products of lime and fly ash treated soils. Based on XRD analyses, major constituents of the CL soil were calcium silicate (CaSiO3), aluminum silicate (Al2SiO5), magnesium silicate (MgSiO3) and quartz (SiO2). Addition of calcium sulfate resulted in the formation of calcium silicate sulfate [Ternesite Ca5(SiO4)2SO4] and aluminum silicate sulfate [Al5(SiO4)2SO4]. Treatment with lime resulted in the formation of ettringite [Ca6Al2(SO4)3(OH)12·26H2O]. Treating with fly ash resulted in the formation of calcium silicate hydrate (CaSiO3H2O) and magnesium silicate hydrate (Mg3SiO3H2O), cementing by products. Contaminated soil treatment with lime and fly ash reduced the index properties and free swelling and increased the short-term compressive strength of the soil. Behavior of the compacted sulfate soils, with and without treatment, has been quantified using a unique model that was used to represent both linear and nonlinear responses. Also the model predications were compared with other published data in the literature. Compressive stress–strain relationships of the sulfate soil, with and without lime and fly ash, have been quantified using a nonlinear constitutive model. The constitutive model parameters were sensitive to the calcium sulfate content and the type of treatment. Compared to the fly ash treatment, the lime treatment reduced the strain at peak stress making the lime treated soil more brittle.