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The purpose of this paper is to collect the numerical elaboration of resistances measured on cubes made during the concrete casting and on cores extracted after the completion of the structure, for the concrete used in the construction of the “Esaro” Dam facilities (Cosenza, Italy). In addition to the statistical treatment of the sample, aimed at assessing the analytical congruence with the homogeneous classes provided in the design, the influence of compaction degree on in place strength value was qualitatively evaluated.

The reliability of the concrete during the construction phases was evaluated by two analytical control types according to Italian and European technical rules: “production controls” based on statistical processing of resistance values; “laying controls” that serve to assess the compaction degree with a statistical approach.

Results highlighted in the assessing of compliance checks of the mixture, the fundamental relation between statistical approach and concrete laying control. They become important when is necessary to quantify, especially in the case of great infrastructure, the gap between “potential” and “structural” concrete.

The advantage obtained by controlling the compaction degree in the construction phase is unquestionable. Specifically, it might allow a reduction of the drilling cores, and so minor structural damage, especially for relatively recent structures favouring extensive non-destructive tests.

Concrete decay has become a major ongoing problem for the developed world, affecting all manner of structures. The purpose of the reported research is thus to advance the prospects for the realisation of high capacity, robotic repair systems through sensor technology. Here, the particular target is the removal of defective concrete by the hydro‐erosion method. The main advantages of the method are that it is kind to the structure while having the potential to produce high definition excavations. Sensing has been investigated for both prediction of the hydro‐erosion task and real‐time process feedback. The latter is complicated by the extremely destructive hydro‐erosion environment, which precludes the use of conventional sensing probes. For this, vibration and process noise have been investigated to determine if diagnostic characteristics are detectable. To support the task, a predictive basis has been developed using non‐destructive testing (NDT) sensors within a data fusion model. Covermeter, rebound hammer, impact echo and surface dampness NDT data are fed into this. Progress is reported on this part of the ongoing research.

This paper aims to study and assess residual strengths of concrete specimen exposed to elevated temperatures by core recovery tests.

The appraisal of concrete structures is typically carried out by means of partially destructive tests such as tests on concrete cores taken from the structure and non-destructive testing.

This paper presents results associated with determination of residual compressive strengths of plain and reinforced concrete elements exposed to elevated temperatures by core recovery test. Physical observations and results of compressive strengths of cores extracted from plain cement concrete, as well as from reinforced concrete beam elements exposed to elevated temperatures, have been presented.

The empirical relations have been proposed between standard cube and core extracted for compressive strength of concretes exposed to elevated temperatures are useful for damage diagnosis.

Roller compacted concrete (RCC) pavement is used in areas subjected to heavy impact loads; therefore, higher impact resistance is a desirable property of consideration. This study aims to investigate the effect of partial replacement of fine aggregate with crumb rubber (CR) and the addition of nanosilica (NS) by weight of cementitious materials on the impact resistance of roller compacted rubbercrete (RCR).

Four replacement levels of CR (0, 10, 20 and 30 per cent) and four addition levels of NS (0, 1, 2 and 3 per cent) were considered. The impact resistance test was carried out using the drop weight test recommended by ACI 544.

The results showed that the impact resistance of RCR increases with an increase in both CR and NS addition, though for CR above 20 per cent, sudden drop in impact resistance was observed. However, NS reduces the ductility of RCR by decreasing the post-cracking impact resistance. Response surface methodology was used to develop models for predicting the impact resistance of RCR, and the developed models showed a high degree of correlation. As a result of wide variations in the impact drop test data, two-parameter Weibull distribution function was used for the data analysis, and it was found that the probabilistic distributions of the first crack and ultimate failure impact resistance follow the two-parameter Weibull distribution function.

In this work, the effect of partial replacement of fine aggregate with CR and the addition of NS by weight of cementitious materials on the impact resistance of RCC pavement has been investigated. CR has been used to increase the impact resistance of RCC Pavement.

The purpose of this work is to study the in-situ performance of ternary geopolymer concrete in road repair work. Geopolymer cement concrete is an attractive alternative to Portland cement concrete owing to environmental, economic and performance benefits. Industrial wastes, such as fly ash (FA) and ground granular blast furnace slag (GGBS), have been extensively used to manufacture unitary and binary geopolymer concrete with heat activation (at different temperature); however, it has indicated a limitation for its application in precast industry only.

In the present study, efforts have been made to produce a ternary geopolymer concrete mix, using GGBS, FA and Silica fumes (SF) in varied proportion mixed with 8 M sodium hydroxide (NaOH) as alkali activator and cured at ambient temperature. Total ten geopolymer concrete mixes have been prepared and tested for strength and durability properties and compared with control mix of ordinary Portland cement (OPC). Based on the mechanical properties of various mixes, an optimum geopolymer concrete mix has been identified. The control mix and optimum geopolymer have been studied for microstructural properties through scanning electron microscopy.

The in situ performance of the optimum mix has been assessed when used as a road repair material on a stretch of road. The ternary geopolymer concrete mixes (a) 65% GGBS + 25% FA + 10% SF, (b) 70% GGBS + 20% FA + 10% SF, and (c) 75% GGBS + 15% FA + 10% SF have resulted in good strength at ambient temperature and the mix 75% GGBS + 15% FA + 10% SF have shown good in situ performance when tested for road repair work.

Geopolymer concrete is gaining interest in many fields as an alternative to conventional concrete, as it not only reduces carbon footprint due to huge cement production but also provides a sustainable disposal method for many industrial wastes. This paper focuses on finding some alternative of OPC concrete to reduce dependency on the OPC.

The purpose of this paper is to show how the investigation into early strength gain of concrete will allow the contractor to speed up the construction process using in situ concrete, which will affect subsequent time and cost savings. If a medium dose of accelerator was found to be effective, the cost/benefit would be substantial as well as being low risk with regard to additive additions in concrete.

Comparative examination of plain concrete, and concrete with a non‐chloride accelerator additive was carried out, using the compressive strength to establish strength gain at various time intervals between one and 28 days. The additive dose was less than half of the maximum recommended to avoid the strength loss problems associated with the use of accelerating admixtures due to possible overheating.

The findings showed a significant increase in strength using an accelerating admixture in the early life of the concrete, which may allow a contactor to strike the formwork earlier, due to the use of an admixture, thus speeding up the construction process to produce time/cost savings.

The research will assist the designer, contractor and health and safety co‐ordinator to strike formwork at the earliest date with greater certainty and therefore reduced risk. By using an accelerator, rather than increasing the cement content to achieve early life strength, this paper displays another way to produce sustainable buildings with a lower carbon footprint. Early life strength provides better freeze/thaw protection and a greater resistance to impact damage and therefore a potential higher quality with lower defects.

The purpose of this paper is to investigate the effect of the replacement of natural coarse aggregate (NCA) with different percentages of recycled coarse aggregate (RCA) on properties of low calcium fly ash (FA)-based geopolymer concrete (GPC) cured at oven temperature. Further, this paper aims to study the effect of partial replacement of FA by ground granulated blast slag (GGBS) in GPC made with both NCA and RCA cured under ambient temperature curing.

M25 grade of ordinary Portland cement (OPC) concrete was designed according to IS: 10262-2019 with 100% NCA as control concrete. Since no standard guidelines are available in the literature for GPC, the same mix proportion was adopted for the GPC by replacing the OPC with 100% FA and W/C ratio by alkalinity/binder ratio. All FA-based GPC mixes were prepared with 12 M of sodium hydroxide (NaOH) and an alkalinity ratio, i.e. sodium hydroxide to sodium silicate (NaOH:Na₂SiO₃) of 1:1.5, subjected to 90^°C temperature for 48 h of curing. The NCA were replaced with 50% and 100% RCA in both OPC and GPC mixes. Further, FA was partially replaced with 15% GGBS in GPC made with the above percentages of NCA and RCA, and they were given ambient temperature curing with the same molarity of NaOH and alkalinity ratio.

The workability, compressive strength, split tensile strength, flexural strength, water absorption, density, volume of voids and rebound hammer value of all the mixes were studied. Further, the relationship between compressive strength and other mechanical properties of GPC mixes were established and compared with the well-established relationships available for conventional concrete. From the experimental results, it is found that the compressive strength of GPC under ambient curing condition at 28 days with 100% NCA, 50% RCA and 100% RCA were, respectively, 14.8%, 12.85% and 17.76% higher than those of OPC concrete. Further, it is found that 85% FA and 15% GGBS-based GPC with RCA under ambient curing shown superior performance than OPC concrete and FA-based GPC cured under oven curing.

The scope of the present paper is limited to replace the FA by 15% GGBS. Further, only 50% and 100% RCA are used in place of natural aggregate. However, in future study, the replacement of FA by different amounts of GGBS (20%, 25%, 30% and 35%) may be tried to decide the optimum utilisation of GGBS so that the applications of GPC can be widely used in cast in situ applications, i.e. under ambient curing condition. Further, in the present study, the natural aggregate is replaced with only 50% and 100% RCA in GPC. However, further investigations may be carried out by considering different percentages between 50 and 100 with the optimum compositions of FA and GGBS to enhance the use of RCA in GPC applications. The present study is further limited to only the mechanical properties and a few other properties of GPC. For wider use of GPC under ambient curing conditions, the structural performance of GPC needs to be understood. Therefore, the structural performance of GPC subjected to different loadings under ambient curing with RCA to be investigated in future study.

The replacement percentage of natural aggregate by RCA may be further enhanced to 50% in GPC under ambient curing condition without compromising on the mechanical properties of concrete. This may be a good alternative for OPC and natural aggregate to reduce pollution and leads sustainability in the construction.

The occurrence of multiple hazards in extreme conditions is not unknown nowadays, but the sustainability of the reinforced concrete structures under such scenarios form competitive challenges in civil engineering profession. Among all, fire following earthquake (FFE) is categorized under multiple extreme load scenarios which causes sequential damages to the structures. This paper aims to experiment a full-scale RC frame sub-assemblage for the FFE scenario and assess each stage of damage through the nondestructive testing method.

Two levels of simulated earthquake damages, i.e. immediate occupancy (IO) level and life safety (LS) level of structural performance were induced to the test frame and then, followed by a realistic compartment fire of 1 h duration. Also, the evaluation of damage to the RC frame after the fire subsequent to the earthquake was carried out by obtaining the ultimate capacity of the frame. Ultrasonic pulse velocity and rebound hammer test were conducted to assess the structural endurance of the damaged frame. Cracks were also marked during mechanical damages to the test frame to study the nature of its propagation.

Careful visual inspection during and after the fire test to the test frame were done. To differentiate between concrete chemically affected by the fire or physically damaged is an important issue. In situ inspection and laboratory tests of concrete components have been performed. Concrete from the test frame was localized with thermo-gravimetric analysis. The UPV results exhibited a sharp decrease in the strength of the concrete material which was also confirmed via the DTA, TGA and TG results. It is important to evaluate the residual capacity of the entire structure under the FFE scenario and propose rehabilitation/retrofit schemes for the building structure.

The heterogeneity in the distribution of the damage has been identified due to variation of fire exposure. The study only highlights the capabilities of the methods for finding the residual capacity of the RC frame sub-assemblage after an occurrence of an FFE.

It is of find kind of research work on full-scale reinforced concrete building. In this, an attempt has been made for the evaluation of concrete structures affected by an FFE through nondestructive and destructive methods.

This paper reviews the most common building defects and techniques for their diagnosis. Problem areas are listed by their location within a structure and the information is presented in tabular form for easy reference. The first paper in this series — ‘Effective diagnosis of material problems and defects in building and construction’ — was published in Structural Survey Volume 4 Number 1. Part 3 will be an appraisal of better known in situ testing and NDT techniques featuring specific items of equipment.

There are a great number of in situ floor finishes available today, including the traditional self‐finished concrete, granolithic and sand cement screeds as well as a bewildering array of special proprietary floor finishes. These include epoxy and polyester resin mortars, and bitumen and polymer emulsion cementitious floor toppings. This article looks at the most common types of floor finish, describes their uses and looks at some of the common faults which arise both through poor materials and workmanship, and heavy usage.