Using an Artificial Neural Network to Validate and Predict the Physical Properties of Self-Compacting Concrete

SCC (self-compacting concrete) is a high-flowing concrete that blasts into structures. Many academics have been interested in using an artificial neural network (ANN) to forecast concrete strength in recent years. As a result, the goal of this study is to confirm the various possibilities of using an artificial neural network (ANN) to detect the features of SCC when Portland Pozzolana Cement (PPC) is partially substituted with biowaste such as Bagasse Ash (BA) and Rice Husk Ash (RHA) (RHA). Specialist systems based on the fully connected cascade (FCC) architecture in artificial neural networks (ANN) are used to estimate the compressive toughness of SCC. The research results are confirmed with the forecasting results of ANN utilizing 73 trial datasets of differentiation focus proposals of cement, BA, and RHA containing parameters such as initial setting time (IST), final setting time (FST), and standard consistency. Experiments to determine compressive strength for a wider range of mixed prepositions will result in higher project expenses and delays. So, an expert system ANN is used to find the standard consistency, setting time, and compressive strength for the intermediate mix propositions according to IS 10262:2009. The experimental results of compressive strength for 28 days are considered, in which 70% was used to train the ANN and 30% was utilized for testing the accuracy of the predicted compressive strength for the intermediate mix proposition. Using all of the datasets, the number of hidden layers used for compressive strength prediction for intermediate mix proposal is determined in the first step. The compressive strength for the intermediate mix preposition was identified in the second phase of the research, using the number of hidden layers determined in the first phase. The results were validated using the correlation coefficient (R) and root mean square error (RMSE) obtained from ANN, resulting in an acceptance range of 97 percent to 99 percent.

Experimental Study on Mechanical Properties of Repair Materials for Underwater Rapid Construction

Several strength grades of sulphoaluminate cement concrete were designed, and the mechanical properties with different mix ratios were studied. This paper mainly analyzes the mechanical properties of sulphoaluminate cement concrete with the setting time test, compressive strength test and flexural test. The test results show that the setting time of cement concrete can be controlled by mixing different admixtures. One hand, the initial setting time increases from 34 min to 340 min, and the final setting time increases from 57 min to 580 min when the incorporated borax content changes from 0 to 1.0 %. Other hand, the initial setting time decreased from 34 min to 11 min, and the final setting time increased from 57 min to 18 min, when the incorporated borax content changed from 0 to 0.5 %. Furthermore, the compressive strength can reach 40 MPa, and the flexural strength can reach more than 2.5MPa after 6 hours of curing. The experiment results illustrate that the setting time and the mechanical properties satisfy the needs of the rapid construction requirements under normal temperature conditions.

Hydro-Mechanics Analysis on the Strength Development of Cement-Stabilized Sand

Deep cement mixing is an effective ground stabilization technique to control the ground movement on sand areas, and most of the projects have the problem of seepage. The cement slurry is in a fluid state before the initial setting time, the seepage may affect the diffusion process of cement slurry during this period. A hydro-mechanical approach is proposed to investigate the interaction between the seepage and the strength of cement-stabilized sand. The diffusion of the cement slurry under seepage is considered in this study and the diffusion process is simulated by the finite element method. According to the cement concentration at the end of the diffusion process, the strength of cement-stabilized sand can be predicted by combining an empirical formula. Simulation results examine that the existence of seepage and cracks can enhance the non-uniform diffusion process of cement slurry, and the actual strength distribution of the deep cement-mixed sand is far from the ideal state. This indicates that the influence of seepage on the strength of cement-stabilized sand should be considered in the design of projects.

The Effect of Superabsorbent Polymer and Nano-Silica on the Properties of Blended Cement

Incorporating superabsorbent polymer (SAP), which has the abilities of absorption and desorption in cement mortar, can achieve the effect of internal curing. It is expected that the incorporation of nano-silica will improve the workability and strength in cement mortar/concrete. Hence, this study aims to examine the effect of SAP and nano-silica on the properties of blended cement paste. The experimental investigations via several tests such as consistency, setting time, compressive strength, UPV, and acid test were performed. Based on energy-dispersive X-ray analysis (EDX) test and scanning electron microscopy (SEM) test results, the morphology of hydration products and mineral compositions of cement paste were further analysed, and the mechanism of SAP with 0.2% and 0.3% and NS with lower percentages ranging from 0.5% to 2% on the performance of cement paste was studied. The results exhibited that incorporating SAP in various percentages from 0.5% to 2% prolonged the initial setting time, reduced the fluidity, and increased the water content and formation of pores. In addition, various percentages ranging from 0.5% to 2% of NS were added; thereby, an increase in the hydration process and refining the microstructure was found. The microscopic test results showed that the blended cement paste can effectively improve the denser microstructure and refine the pore structure.

Investigation of the material mixtures and fiber addition for 3D concrete printing

The era of Construction 4.0 is characterized by technological advances used in the construction industry. One of the advancements is the use of 3D concrete printing in construction. However, until now, the development of 3D concrete printing in Indonesia is still minimal. The main challenge is to determine the composition of the material mixtures for making the mortar, having good extrudability but still has sufficient strength. The rapid initial setting time required was also different for the concrete for typical construction. Our previous mixture composition incorporating calcium oxide to accelerate the initial setting time was adequate. However, the extrusion process was still not satisfactory. In this study, the effect of cement to sand ratio, sand particle size, and the addition of synthetic micro-fiber was investigated on the main properties of 3D printing materials, i.e., initial setting time, flowability, extrudability, and compressive strength. It was found that using smaller maximum particle size sand increases the initial setting time. The addition of synthetic microfiber reduces the strength and the workability of the mortar. However, fiber inclusion has advantages as it reduces the possibility of cracking in the printed concrete. The extruded concrete specimens were shown to have significant strength reduction due to lack of compaction, and it was affected by the direction of printing showing orthotropic properties of the 3D printed concrete.

Physical Characteristics and Compressive Strength of Na-Geopolymer Paste Designed by a Taguchi Method

Geopolymer paste is a revolutionary building material that the chemical activity of inorganic molecules will create. It is an alternative to traditional Portland cement and is more Eco-friendly. This analysis aimed to classify the mixtures and their process parameters suitable for the development of Geo-polymer paste with one of the ultimate compressive powers, the highest-lowest porosity, and the lowest-lowest final and initial setting time. In the experimental design of the Geo-polymer-based-metakaolin, a Taguchi methodology has been utilized. Five variables parameters were chosen that are mostly to influence the properties of the geopolymer. These are the quantity of Si, alkali, the proportion of alkali reagents, duration of blending, and water amount. These variables’ influence has been calculated at 7 and 28 days on compressive strengths, porosity, density, and setting time. The analysis indicates that the strong compressive strength (115MPa) of Geopolymer paste could be achieved with the formula (1Na2O. Al2O3. 3.8SiO2.xH2O) utilizing suitable processing conditions under which the molar ratio of alkali silicate to alkali hydroxide must be held within the range of 3.25-3.02.

Investigation on the Compressive Strength and Time of Setting of Low-Calcium Fly Ash Geopolymer Paste Using Response Surface Methodology

Approximately 2.78 Mt of coal fly ash is produced in the Philippines, with a low utilization rate. Using fly ash-based geopolymer for construction will lessen the load sent to landfills and will result in lower GHG emissions compared to OPC. It is necessary to characterize the fly ash and optimize the geopolymer components to determine if it can replace OPC for in situ applications. The activator-to-precursor ratio, the water-to-solids ratio, and the sodium hydroxide-to-sodium silicate ratio were optimized using a randomized I-optimal design from the experimental results of 21 runs with five replicates, for a total of 105 specimens of 50 mm × 50 mm × 50 mm paste cubes. The engineering properties chosen as the optimization responses were the unconfined compressive strength (UCS), the initial setting time, and the final setting time. The samples were also ambient-cured with the outdoor temperature ranging from 30 °C to 35 °C and relative humidity of 50% ± 10% to simulate the on-site environment. Runs with high unconfined compressive strength (UCS) and short setting times were observed to have a low water-to-solids (W/S) ratio. All runs with a UCS greater than 20 MPa had a W/S ratio of 0.2, and the runs with the lowest UCS had a W/S of 0.4. The initial setting time for design mixes with a W/S ratio of 0.2 ranged from 8 to 105 min. Meanwhile, five out of seven design mixes with a W/S ratio of 0.4 took longer than 1440 min to set. Specimens with an alkali activator ratio (NaOH/WG) of 0.5 (1:2) and 0.4 (1:2.5) also had significantly lower setting times than those with an alkali activator ratio of 1. The RSM model was verified through confirmatory tests. The results of the confirmatory tests are agreeable, with deviations from the expected UCS ranging from 0 to 38.12%. The generated model is a reliable reference to estimate the UCS and setting time of low-calcium FA geopolymer paste for in situ applications.

Analysis of the Influence of Crystalline Admixtures at Early Age Performance of Cement-Based Mortar by Electrical Resistance Monitoring

Crystalline admixtures are employed for waterproofing concrete. This type of admixtures can affect the early age performance of cement-based mixes. The electrical resistance properties of cement have been related to the initial setting time and to the hydration development. This paper proposes a system for remote monitoring of the initial setting time and the first days of the hardening of cement-based mortars to evaluate the effect of the incorporation of crystalline admixtures. The electrical resistance results have been confirmed by other characterization techniques such as thermogravimetric analysis and compressive strength measurements. From the electrical resistance monitoring it has been observed that the incorporation of crystalline admixtures causes a delay in the initial setting time and hydration processes. The measurements also allow to evaluate the influence of the amount of admixture used; thus, being very useful as a tool to define the optimum admixture dosage to be used.

Effects of a Natural Mordenite as Pozzolan Material in the Evolution of Mortar Settings

This paper shows the results of a study focused on the evolution and properties of mortars made with a mixture of portland cement (PC) and natural mordenite (Mor). To begin, samples of mordenite, cement and sand were studied with X-ray diffraction (XRD), X-ray fluorescence (XRF) and granulometric analysis (GA). Next, mortars with a ratio of 75% PC and 25% mordenite were prepared to determine their initial and final setting times, consistency and density. Continuing, the density, weight and compressive strength of the specimens were determined at 2, 7, 28, 90 and 365 days. Finally, the specimens were studied using SEM, XRD and XRF. The results of the study of the mordenite sample showed a complex constitution where the major mineral component is mordenite, and to a lesser degree smectite (montmorillonite), halloysite, illite, mica, quartz, plagioclase and feldspar, in addition to altered volcanic glass. Tests with fresh cement/mordenite mortar (CMM) showed an initial setting time of 320 min and a final setting time of 420 min, much longer than the 212–310 min of portland cement mortar (PCM). It was established that the consistency of the cement/mordenite mortar (CMM) was greater than that of the PCM. The results of the density study showed that the CMM has a lower density than the PCM. On the other hand, the density of cement/mordenite specimens (CMS) was lower than that of portland cement specimens (PCS). The CMS compressive strength studies showed a significant increase from 18.2 MPa, at 2 days, to 72 MPa, at 365 days, with better strength than PCS at 28 and 365 days, respectively. XRD, XRF and SEM studies conducted on CMS showed a good development of primary and secondary tobermorite, the latter formed at the expense of portlandite; also, ettringite developed normally. This work proves that the partial replacement of PC by mordenite does not have a negative effect on the increase in the mechanical strength of CMS. It indicates that the presence of mordenite inhibits the spontaneous hydration of C3A and controls the anomalous formation of ettringite (Ett). All this, together with the mechanical strength reported, indicates that mordenite has a deep and positive influence on the evolution of the mortar setting and is an efficient pozzolan, meaning it can be used in the manufacture of mortars and highly resistant pozzolanic cement, with low hydration heat, low density, stability in extremely aggressive places and a low impact on the environment.

Optimization of Ternary Binders Based on Flash-Calcined Sediments and Ground Granulated Blast Furnace slag Using a Mixture Design

CO2 emissions resulting from the production of cement is a major issue, but can be limited by the partial substitution of cement by low-carbon-impact additions. The aim of this study was the formulation of a ternary binder based on ordinary Portland cement (OPC), ground granulated blast-furnace slag (GGBS) and flash-calcined sediment (FCS), a dredged waste which was valorized after applying a new heat treatment: flash calcination. The used materials were physically, chemically and mineralogically characterized. The composition of the formulations was optimized using mixture designs. Five formulations, one reference formulation RM (100% OPC), one binary formulation (50% OPC/50% GGBS), and three ternary formulations with a variable FCS rate (10%, 15%, 20%), were selected and characterized fresh and hardened. Results showed that the incorporation of FCS reduced the workability and increased the density. In addition, a decrease in the initial setting time and the heat of hydration peak were observed. In the hardened state, the formulation containing 10% FCS showed 90-day mechanical strengths superior to that of RM. The use of FCS in ternary binders could reduce the environmental impact by reducing greenhouse gas emissions.