The paper reports on the performance of 34 different concrete mixes containing glass crushed to ¾-in. (19-mm) maximum size as coarse aggregate and six reference mixes made with gravel of the same size. Two cements of alkali equivalent 0.58 and 1.13, classifiable as low and high alkali (ASTM C 150-72), in amounts ranging from 400–900 lb/yd3 (237–534 kg/m3 were used in combination with glass both with the fines removed and in the as-crushed condition. Partial cement replacement with fly ash and mixing of glass with gravel aggregate were included in an attempt to find a suitable method of overcoming the expected adverse effects of the reaction between glass and cement alkalis. On the basis of compressive strength, flexural strength, expansion, and visible surface deterioration recorded up to an age of one year, the results show that in many cases the direct combination of glass with portland cement yields concrete which exhibits marked strength regression and excessive expansion due to alkali-aggregate reaction. The conditions under which performance is satisfactory appear to relate to limiting maximum values of cement content and alkali equivalent. Replacement of 25 to 30 percent by weight of the cement, whether low or high alkali, appears to be an effective and widely applicable method of ensuring good long-term concrete performance, although the minimum required in any given case may be related to cement composition.
Compressive and tensile strength of dry Douglas-fir was measured through rapid constant deformation rate tests at temperatures from 25 to 288°C, at initial thermoequilibrium and after 2 h of heating. The tensile strength decreased slowly with increasing temperatures to 175°C. Above 175°C, the tensile strength reduces rapidly. This is attributed to alteration of the cellulosic fraction of wood. The compressive strength decreases more uniformly with temperatures increasing to 288°C due to changes occurring in all three basic wood components with change in temperature. A first-order reaction equation for bond rupture/formation was adopted to describe the response. Including only terms for bond rupture resulted in good correlation to the observed strength response at reaching thermoequilibrium.
Sulfate attack on concrete can either be of expansion-cracking type due to ettringite formation or of surface deterioration type due to acidic nature of sulfate solutions. The present test methods for determining sulfate resistance generally evaluate the expansive attack phenomenon. Since low C3A portland cements are not susceptible to this type of attack, new methods need to be developed to test the long-time resistance of these cements to the acidic type of sulfate attack. An attempt to develop a laboratory method involving immersion of small specimens of cement paste in a sulfate solution held at constant pH is described. Preliminary results are given for five different types of cements tested in accordance with the new method.
Time and costs studies in 1965 showed that in soil mechanics laboratories 60 to 90 percent of the total costs of tests were labor costs. The reason for these high labor costs is there has been very little mechanization of soil mechanics laboratory tests.
The porosity and pore size distributions of cement pastes of water/cement ratios of 0.35 and 0.55 were measured by high pressure (50,000 psi) mercury porosimetry. Measurements were made on pastes hydrated from 8 hours to 90 days. The variation of mercury porosity with maturity was found to correlate well with generally held concepts of the hydration of cement paste. Differences in the pore size distributions between pastes of different water/cement ratio lie mainly in the region of large pores.
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