... with stronger
dipole yet short-lived ( 30 60 minutes) forces. Their addition rates are
rather higher than for plasticisers and range approximately from 200 to
200 0 ml/ 50 kg depending upon the effect ... 2.5
TYPICAL EFFECT OF PLASTICISING ADMIXTURE ON
PROPERTIES OF A VIBRATED CONCRETE PRODUCT
The dosage rates vary from 100 to 100 0 ml/ 50 kg cement and each
type should be dispens...
... following F/C ratios and approximate total water contents were
used:
F/C 0 0·25 0 37 0 50 0·63 0 75
Total water 0 28 0 32 0 34 0 36 0 38 0 40
Observed and cost-corrected-relative-to-control failing ... weight)
The mix, ash and water variations were as follows:
F/C 0 0·25 0 50 1 00 1· 50 2 00
Total water 0 35 0 39 0 43 0 50 0·58 0 65
Table 4.11 lists the 14 day o...
... cone flower
pot units, etc., and when properly constructed and used have a lifetime of
200 – 100 0 uses. Figure 1.6 illustrates a GRP-U-section gulley unit mould
where the resin has a white silica ... relevant
to precast concrete manufacture leaving mix design to Chapters 5 and 6.
1.5.1 Cement types
The most common cements used are ordinary and rapid-hardening
Portland (includi...
... concrete colour
Both the desk-top 100 mm square sample and the 300 mm square hand-
portable samples are misleading in the case of unpigmented materials,
and for coloured concretes and mortars they seldom ... agents should be water-in-oil emulsion creams or
chemical release agents. Ordinary mineral mould oils and oil-in-
water emulsions promote streaking and staining.
(c) Pan-typ...
... accurate and consistent quantity of
concrete into the mould.
In some precast processes tilting tables are used both to cast the
concrete and lift the mould and concrete into the near-vertical ... devices such as clamp-on and poker vibrators are
high-wear-rate pieces of machinery and a sufficient supply of spares
should always be kept.
9. Poker vibrators need plenty of room...
... Science Publishers Ltd 1982
Water 40+ 20+ 30= 90= Added or total water
40= Effective or free water
The two W/C ratios are 0 40 and 0 90.
6.1 GENERAL PRECAST WET-CAST PRODUCTION
Products in this ... clean 0 4% 0
150kg sand 1 0% 3 0%
100 kg cement
40kg effective water
The granite needs 1·2 kg water to cater for its absorption. The sand has
3 0 kg excess water in it, (3 0% –1 0% )...
... of natural aggregate
concrete contains about 200 0 kg aggregate and lightweight aggregate
about 1 200 kg, the exotherm from the same cement content will result in
a higher concrete temperature ... up and gains strength slowly; a warm-starting concrete, say 25°C,
warms up and gains strength more quickly; and a concrete starting at,
say 40 C, can be handled within a few hours. An...
... effect as the following typical readings in m1/
m
2
/s show:
10 min 30 min 1h
Non-air-entrained 0 50 0· 30 0· 20
Air-entrained 0 40 0 05 0 01
Fig. 8.18. Defective kerbs with only partial replacement.
Copyright ... factor of 10; i.e.
20dBA is about 2× 10
-4
N/m
2
, and so on. Equivalents in real terms are:
Less than 10 An eerie silence
10 20 Birds in a garden
20 40 Conve...
... the
previous 3 days.
Day of casting no. 10 min 30 min 1 h
1 0 20 0·12 0 09
2 0 10 0 07 0 05
3 0 13 0 08 0 06
4 0 09 0 06 0 04
5 0 37 0 20 0·16
6 0 09 0 07 0 05
One would need to look at the curing ... 10 blocks/day testing:
Average of 10 blocks м 0. 9 × specified strength + 0. 62 × standard
deviation
Day no. Average of 10 Standard 0 9×7 0 Accept/
deviation...