Materiales de Construcción

Study on binary and ternary systems with cement, hydrated lime and fly ash: thermogravimetric analysis, mechanical analysis and durability behaviour

P. Lorca — 2023-07-10

The use of high percentages of substitution of Portland cement by pozzolans can provoke the total consumption of portlandite. The present research proposes the study of ternary systems of Portland cement (PC), fly ash (FA), and hydrated lime (CH). After 180 days of curing, the mortar with 50% substitution of PC by FA obtained 65.9 MPa versus the mortars with an addition of 20% of CH and control mortar (100 PC) that obtained 69.9 MPa and 76.7 MPa respectively: this behavior is very positive value considering that tested FA containing mortars had a 50% of Portland cement. Regarding the effect of the amount of extra hydrated lime on durability issues, the evolution against carbonation of PC-FA and PC-CH-FA mortars was studied: the reduction of carbonation velocity was around a 37% for the mortar with CH respect the PC-FA mortar.

Recycling of eps foam and demolition wastes in the preparation of ecofriendly render mortars with thermal-acoustic insulation properties

C.D. Acevedo-Sánchez — 2023-08-09

The design of render-mortars from construction and demolition waste (CDW) was evaluated. Fine aggregates from red-clay-brick waste, mortar and concrete waste were used, together with recycled expanded-polystyrene (EPS) as lightweight filler. Mixes composed of 70%-recycled aggregates, and 30% consisting of a matrix of Portland cement were produced. Characterization tests were conducted on the physical, mechanical, thermal, and acoustic properties. The render-mortar A4, A7 and A9 can be classified according to compressive strength results as CSI-W0 for interior use under standard UNE-EN-998-1. The A7 mortar, with the best physical and mechanical results, contained 21% EPS, 17.5% brick waste and 17.5% mortar waste. Mix A4 obtained the lowest thermal conductivity, 0.12 W/m·K - a reduction of 79% compared to the commercial-mortar AC1. The acoustic absorption properties were also enhanced by the incorporation of EPS, such that the A4, A7, and A9 mixes were identified as Absorbent for the frequencies of 2000 Hz and 4000 Hz.

Fresh, hardened and thermal properties of coating mortars containing mineral additions and vermiculite

K. dos Santos — 2023-08-09

Efforts are made to alleviate thermal problems in buildings. The use of thermal mortars for coating with vermiculite as aggregate is used for this purpose, but the use with mineral additions is still scarce, especially the rheology through squeeze-flow. Thus, it was aimed to evaluate the behavior in fresh, hardened state and in the thermal conductivity of these mortars. Mortars containing Portland cement, lime, vermiculite, sand, and additions of metakaolin or ceramic brick waste, in the proportion of 1:1:6 (Cement: Lime: Sand), were evaluated. The sand was replaced by vermiculite in 40%, and the additions added in the proportion of 20% to the cement mass, and the water content determined with the spread obtained on the consistency table. Mixtures containing 20% mineral addition and 40% vermiculite proved to be feasible, reaching minimum values according to the respective standards.

Investigation of reinforced concrete members with bond deterioration under tensile load

A.I. Quadri — 2023-08-10

Bond deterioration in reinforced concrete (RC) structures is frequently caused by aging, environmental factors, overloading, or poor design. This deterioration may cause the structure to lose its aesthetic, and eventually collapse. The behavior of structures that exhibit bond deterioration is poorly understood and inadequately maintained. The response of RC structures exhibiting bond loss under tension load is presented in this paper. In order to comprehend the impact of bond loss in RC composite, the RC system was first built for a pullout. It was then expanded to the nib corner of RC dapped end beams. Additionally, the system was analytically examined using 3-dimensional FEmodel. The bond loss created a weak zone with internal cracks parallel to the bar’s axis. The nib section separated from the full depth of the dapped end, while the hanger reinforcement resisted the diagonal tension cracks. The dapped section must therefore be given more consideration during monitoring and maintenance.

Experimental investigation of clogging mechanism of pervious concrete made with variable aggregate gradations

M. Nazeer — 2023-08-10

In this study, the clogging mechanism of pervious concrete was evaluated using three different cloggers such as, Sand (S), Clay (C), and combination of sand and clay (S &C). The clogging mechanism was performed through falling head permeability apparatus, using clogger sediment load at the rate of 50, 150, and 200 grams in repetitive clogging cycles. It was observed from the results that combined (S & C) clogger shows overall critical results of clogging as 80% of the clogging was seen in 3 to 4 cycles. Moreover, it was observed from the results that pervious concrete mix made with R- type of aggregate gradation shows optimum compressive strength of the order of 8.6, 15.9, and 17 MPa at 7, 28 and 56 days of curing. Furthermore, the visual inspection test shows that clogging by clay clogger shows an even distribution of sediment on the whole length of the sample.

Fresh, hardened and durability properties of sodium carbonate-activated Algerian slag exposed to sulfate and acid attacks

R. Kahlouche — 2023-08-10

This paper investigates the use of Na2CO3 as an alkaline activator on the durability of the alkali-activated slag (AAS) mortar toward sulfates and acids. The behavior of this binder in these aggressive environments is compared to those of slags activated with Na2SiO3 and NaOH. In addition, the setting times, workabilities, mechanical properties and drying shrinkage were evaluated. The AAS had superior workabilities, faster setting times and higher shrinkage rates than the Portland cement (PC). Increases in the activator dosages had positive effects on the mechanical strengths of the materials. Na2SiO3 was the best activator in terms of strength development, but it led to much higher shrinkage. The AAS showed less expansion and lower weight losses than the PC when exposed to sulfate and acids, respectively. The Na2CO3-AAS exhibited less shrinkage and higher resistance to sulfuric acid than the other activators, but the mechanical strength seen at early ages was low.

Analysis of two experimental setups to study mode II fracture on fibre-reinforced gypsum notched specimens

Fernando Suárez — 2023-08-28

The main aim of this work is to study two relevant experimental setups designed for studying shear fracture and see if any of them allows studying the evolution of fracture under Mode II conditions, not only inducing a shear stress state at the onset of fracture. Two tests have been selected, a standardised test described by a Japanese standard, here referred to as the JSCE test, and the push-off test. These tests have been carried out on fibre-reinforced gypsum specimens with increasing proportions of polypropylene fibres and monitored by means of digital image correlation (DIC). The results show that fracture under Mode II conditions is relatively easy to induce with both tests, but once fracture begins, it is extremely difficult to induce a fracture process under Mode II. In general, Mode II has an important role at the onset on fracture, but Mode I predominates afterwards.

Computer vision application for improved product traceability in the granite manufacturing industry

J. Martínez — 2023-08-10

The traceability of granite blocks consists in identifying each block with a finite number of colour bands that represent a numerical code. This code has to be read several times throughout the manufacturing process, but its accuracy is subject to human errors, leading to cause faults in the traceability system. A computer vision system is presented to address this problem through colour detection and the decryption of the associated code. The system developed makes use of colour space transformations and various thresholds for the isolation of the colours. Computer vision methods are implemented, along with contour detection procedures for colour identification. Lastly, the analysis of geometrical features is used to decrypt the colour code captured. The proposed algorithm is trained on a set of 109 pictures taken in different environmental conditions and validated on a set of 21 images. The outcome shows promising results with an accuracy rate of 75.00% in the validation process. Therefore, the application presented can help employees reduce the number of mistakes in product tracking.

New insights into the production of sustainable synthetic aggregates and their microstructural evaluation

R. Vignesh — 2023-07-28

In this study, a novel technique for producing synthetic aggregates using industrial by-products was experimentally investigated. Taguchi method is used to identify the optimum mix design proportion to develop durable synthetic aggregates. For this, different combinations of quaternary binders including ordinary Portland cement, ground granulated blast furnace slag, metakaolin, and lime powder was used. The obtained results revealed that the synthetic aggregates prepared with optimized mortar mix enhanced the compressive strength by 5.9%. Then the performance of synthetic aggregates was evaluated based on their mechanical and durability properties. Microstructural properties of the produced aggregates were examined. The results showed that optimum mix is highly effective than control mix. The manufactured synthetic aggregates are in accordance with the ASTM C 330 standard requirements. Therefore, our study contributes to the advancement in the sustainability by developing a method for producing synthetic aggregates from industrial byproducts.