A review of the multi-component utilisation of coal fly ash

A review on dynamic mechanical properties of natural fibre reinforced polymer composites

Geopolymer foam concrete: An emerging material for sustainable construction

The thermal conductivity (k-value) of cement-based materials like concrete is an important factor when considering the amount of heat transfer through conduction. The amount of heat loss through walls and roofs has a direct effect on the energy consumption of buildings. The steady state and transient methods are considered the two main thermal conductivity measurement approaches. The moisture content, temperature, type of aggregate, type of cementitious material and density of concrete are influential factors on the thermal conductivity. The aim of this paper is to review the techniques most commonly used to measure the thermal conductivity of concrete as well as to consider the factors affecting the thermal conductivity of cement-based materials. In addition, a general equation for predicting the thermal conductivity of concrete is proposed in this study based on data reported by researchers. The results of this review indicate that most researchers have measured the k-value of cement-based materials based on transient methods. The reported k-value in saturated conditions is higher than in dry conditions. Moreover, the measured k-value exhibits a declining trend with increasing temperature. It is concluded that using lightweight concrete in structural and non-structural building envelopes is a valuable method of reducing the amount of heat transfer and energy consumption owing to the lower k-value of lightweight concrete compared to normal weight concrete.

Thermal conductivity of concrete – A review

The pozzolanic activity of calcined clays depends on the type and amount of clayed minerals, the nature and amount of impurities, the thermal treatment used for its activation and the specific surface obtained after calcination. In this paper, four test methods for assessment the pozzolanic activity on seven calcined clays (five kaolinites and two bentonites) were analyzed. Natural clays were calcined and investigated by two direct tests (Frattini and saturated lime) and two indirect tests (strength activity index and electrical conductivity). Frattini test and the strength activity index (SAI) were found to be the most accurate and reliable methods to assess pozzolanic activity over time. Frattini test evaluates accurately the calcium hydroxide (CH) consumption by pozzolanic reaction, and SAI test discriminates the real contribution of pozzolanic reaction to densification of microstructure. The electrical conductivity (EC) and the lime consumption (LC) tests evaluate the ability of pozzolanic material to fix CH during the first time of contact and their results are correlated with the specific surface of calcined clay.

Assessment of pozzolanic activity of different calcined clays

This article presents experimental research work oriented toward developing practical design tools for industrial application, and illustrates the potential benefits of the synergistic effect of an ASTM C 618 Class F fly ash (FA) and a high-range polycarboxylate superplasticizer (SP) in the production of conventional concrete. The different concretes considered in this study were produced with mass substitutions of cement by FA between 15% and 75%, and a target slump of 200 mm ± 20 mm. The total water content was minimized through the use of an optimum SP dosage that resulted in water reductions of 18%, 15% and 11% respectively for the reference mixtures of w/b = 0.5, w/b = 0.55, and w/b = 0.6, which leads to the same percentage reductions of cement. Heat release and heat flow were analyzed through isothermal and semi-adiabatic calorimetry, illustrating that heat release per unit mass of cement is independent of w/b, contrasting with the time of setting results that vary by several hours between the three different w/b ratios. The paper highlights the beneficial effect of the SP in terms of cement reduction and slump retention. Correlations between the FA substitution and slump loss, setting times, compressive strength and static modulus of elasticity (E) were established and they represent very useful tools for the practical applications of the results. Compressive strength developments up to an age of 56 d are also reported, as well as correlations between the modulus of rupture and compressive strength or splitting tensile strength at an age of 28 d.

/pdf/evaluation-of-sustainable-high-volume-fly-ash-concretes-44re3rhlpo.pdf

Evaluation of sustainable high-volume fly ash concretes

As sustainability moves to the forefront of construction, the utilization of high-volume fly ash concrete mixtures to reduce CO2 emissions and cement consumption per unit volume of concrete placed ...

Thermal properties of high-volume fly ash mortars and concretes:

https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=904699

A. Durán-Herrera

Papers

Evaluation of sustainable high-volume fly ash concretes

Thermal properties of high-volume fly ash mortars and concretes:

Evaluation of Sustainable High-Volume Fly Ash Concretes | NIST

The micromechanical signature of high-volume natural pozzolan concrete by combined statistical nanoindentation and SEM-EDS analyses

Comparative study between natural and PVA fibers to reduce plastic shrinkage cracking in cement-based composite