The properties of hydraulic mortars were studied by means of simultaneous thermal analysis (STA), according to a procedure
proposed in the literature. Hydraulic limes, cement and/or slaked lime were mixed using different proportions of both inert
and reactive aggregates, in order to test the effectiveness of such procedure in distinguishing the different degree of hydraulicity
of such samples. The use of the normalized coordinates suggested in the literature results in overlapping of the clusters
of different kinds of mortars. Modified coordinates are proposed, which give promising results in view of outlining a ‘master
curve’ of hydraulicity.
Authors:L’. Krajči, S. Moujmdar, M. Kuliffayová, and I. Janotka
Two types of raw materials, original kaolin sand OKS I and OKS II were used for experiment. They were transformed (1 h at
650 °C with 10 °C/min temperature increase) to burnt kaolin sand (BKS I and BKS II) with pozzolanic properties. Contents of
decisive mineral—metakaolinite—in BKSs are as follows: BKS I (fraction below 0.06 mm) 20%; BKS II (fraction below 0.06 mm)
36% and BKS II (fraction below 0.1 mm) 31% by mass. Mortars with blends of Portland cement (PC) and BKS were prepared announced
as: MK I (0.06) with 5 and 10% cement substitution by metakaolinite; MK II (0.06) with 5 and 10% cement substitution by metakaolinite
and MK II (0.1) with 5, 10, 15 and 20% cement substitution by metakaolinite. The reference mortar with 100% of PC was made
for comparison. All mortars were adjusted on the constant workability 180 ± 5 mm flow. Besides significant increase in compressive
strengths—the refinement of pore structure in mortars with BKS connected with decreases in permeability and Ca(OH)2 content were revealed. The above facts confirm pozzolanic reaction of BKS in contact with hydrated PC and indicate perceptiveness
of BKS for the use in cement-based systems as a pozzolanic addition.
In this paper the results of an investigation about steel fibers bond strength in mortar matrix are presented. Pull-out tests were made with four different types of fibers (hookedend, crimped, flat-end, anchoraged), the fibers were embedded individually into a cement based sample with three different embedded length (10, 15, 20 mm). Another variable parameter of the experiment was the strength of the matrix (three different mixture were used), and hooked-end fibers with higher tensile strength and zinc surface coating were tested also. During the tests pull-out force and displacement were measured.
Authors:M. García de Lomas, M. Sánchez de Rojas, and M. Frías
This work presents the relation between the pozzolanic activity, the hydration heat and the compressive strength developed
by blended mortars containing 10 and 35% of a spent fluid catalytic cracking catalyst (FCC).
The results show that, in comparison with 100% Portland cement mortar, a mortar with 10% FCC increases the hydration heat
all over the period of testing. This hydration heat increasing is due to the pozzolanic effect, therefore the resulting compressive
strength is higher than the reference mortar. Whereas, in a mortar with 35% of FCC, the hydration heat is higher than 100%
PC mortar, until 10 h of testing. After this age, the substitution degree predominates over the pozzolanic activity, showing
in this case, lower hydration heat and developing lower compressive strength than 100% PC mortar.
The chemical corrosion and the mechanical strength were studied in cement mortars containing an additive of FBCC under conditions
of long-term action of sodium sulphate solution or saturated brine. The observations have shown that saturated brine is a
more aggressive agent, since it leaches Ca(OH)2 and contributes to the decomposition of the C-S-H phase thus worsening the compressive strength as compared with that of
mortars kept in water. The addition of 20% FBCC inhibits the leaching process and counteracts the decrease of compressive
strength in mortars kept in brine. On the other hand, sodium sulphate solution changes favourably the mortar microstructure,
increases of the content of small pores and improves both the compressive and the flexural strengths, as compared with those
of a mortar kept in water.
The influence of spent catalyst from catalytic cracking in fluidized bed on the hydration process of cement and the properties
of cement mortars were studied. The spent catalyst was used as an additive to cement in the mortars (10 and 20% of cement).
The samples of mortars kept in water for28 days, then they were placed in sulfate and chloride media for 2 months (the control
samples were kept in water for 3 months). After this time they were subjected to bending strength and compressive strength
determinations. Thermogravimetric and infrared absorption studies were performed and capillary elevation, capability of binding
heavy metals, and changes in mass and apparent density were determined too. The studies disclosed the pozzolana nature of
spent catalyst and its influence on cement mortars being in contact with corrosive media.
Authors:J. Gonçalves, R. Toledo Filho, and E. Fairbairn
This paper reports an experimental study on the magnesium sulphate resistance of mortar specimens incorporating 0, 10 and
20% of metakaolin (MK). The evidence of the attack was evaluated through the content of calcium hydroxide (portlandite) and
formation of magnesium hydroxide (brucite) by thermal analysis (thermogravimetric and derivative thermogravimetric analysis).
The mechanical degradation of the mortar specimens was evaluated through splitting tensile tests after 200 days of exposition
to the magnesium solution. The addition of metakaolin resulted in a reduction in the content of calcium hydroxide and in a
smaller formation of brucite in comparison with reference mixture. A tensile strength loss of about 7% was observed for the
metakaolin mortars submitted to the magnesium solution attack for 200 days.
Authors:G. Rizzo, Laura Ercoli, B. Megna, and Maria Parlapiano
Long aged mortars from ancient hydraulic constructions of Sicily, i.e. the Roman aqueduct of Thermae and the Punic cisterns
and traditional water supply systems in Pantelleria, have been characterised by means of XRD analysis, optical microscopy
and simultaneous thermal analysis to correlate the hydraulic properties to the texture and to their different role in the
construction, i.e. lining, covering, roofing and joint mortars.
According to a procedure proposed in the literature all of the samples, but two air hardening ones, show high hydraulicity,
which somehow can be related to the characteristics of aggregates.
Authors:C. Tomasi, O. Ricci, G. Perotti, and P. Ferloni
Plasters and mortars taken
from the walls of the ancient hospital ‘San Matteo’ of Pavia (Italy),
were investigated with thermal and other techniques. From the data collected,
two groups of materials were brought out: the first one, containing the plasters,
is remarkably richer in calcite than the second group, formed by the mortars.
These findings allow one to relate these groups to two historical periods:
the middle of the XV century, and the end of the XVIII century. Some hypotheses
may also be made on the compositions of the binding/inert fractions adopted
in preparing these materials in the building yards of the two periods.
Sulphate resistance and passivation ability of the mortars made from pozzolan cement of CEM IV/A (P) type according to European
Standard EN 197-1 (zeolite blended cement with 60.82 mass% of PC clinker, 35.09 mass% of zeolite and 4.09 mass% of gypsum
abbreviated as ZBC) and ordinary Portland cement (abbreviated as PC) are introduced. Resistance tests were performed in water
and 5% sodium sulphate solution (both 20°C) for 720 days. The increased sulphate resistance of pozzolan cement relative to
that of PC was found. The key quantitative insight into the hydrate phase behaviour is given by thermal analysis. This is
due to pozzolanic reaction of zeolite with PC resulting in reduction of the formed Ca(OH)2 opposite to the reference PC. Ability of pozzolan cements with 15 to 50 mass% of zeolite to protect steel against corrosion
was verified in 20°C/85% RH-wet air within 180-day cure. Steel was not corroded in the mortars made with pozzolan cement containing
up to 35 mass% of zeolite. Pozzolan cement of CEM IV/A (P) type containing 35 mass% of zeolite is a suitable cementitious
material for concrete structures exposed to sulphate attack. Steel is protected against corrosion by this pozzolan cement
in the same measure as the reference PC.